Design concepts for speakers

[yves]

sme

You raise some good points. Agree that adding more mass to the woofer design to get more tactile extension can cause a decline in accuracy, but I should note that not all woofers are being designed this way; the dual 8" woofers in my Cantons use an aluminum woofer membrane partly because aluminum has a low mass versus its strength, strength being important also because it prevents the surface from flexing so starting to cause noticeable distortions above a certain SPL. A bigger diameter woofer displaces more air, but also flexes more. On top of that; sound waves generated at the left edge of the woofer membrane do not reach the ears via the same path as those generated at the right edge so the smaller diameter woofer can have cleaner dispersion. A better design approach to increasing woofer low end extension IMO *can* be to aim for optimizing the cabinet, using advanced bass reflex technology. Further, the bass of my Canton speakers cuts off very steeply below 29 Hz, they already are down 6 dB by 31 Hz, but for watching movies I can cheat a couple Hz thanks to manual PEQ in the UMC-200. These speakers use Displacement Control, a technology developed by Canton, that eliminates frequencies below 20 Hz to prevent uncontrolled deflections of the woofer membrance, and to improve accuracy. I mostly listen to ripped vinyl so in my case it also removes the excess rumble that vinyl sound often has. Speaker impedance dips below 4 Ohms, but never very far. Speaker sensitivity is reasonable IMO at 88.5 dB sensitive. With the XPA-2 Gen 1 powering these speakers, the SPL that I am able to achieve without noticing signs of strain / compressed dynamics is above permanent ear damage / monstrosity level, which helps to explain why manual PEQ in the UMC-200 works for me in HT listening mode, enough for me to not need a sub for now, due partly to budget constraints, personal preferences and other priorities (like, for example, waiting for Emo subs to appear on website). Waveguide technology is included in the design of my Cantons. Frequency response is surprisingly more linear neutral compared to Bowers & Wilkins costing over double the price of my Cantons. I could go on, for example by adding that there's more to sound than bass alone, but... different folks, different strokes!

[sme]

To clarify about woofers with more mass. Mass does not harm accuracy, at least not directly. Adding mass decreases the resonance frequency and increases the Q of the driver, which tends to increase sensitivity in the region of the resonance frequency of whatever alignment is chosen. Another way to think of it is that adding mass lowers the -3 dB point in the response. However, adding mass comes with a big cost which is reduced sensitivity and efficiency for the most of the rest of the frequency range. The reduced efficiency can harm accuracy because the coil needs a lot more power to get the same output from the driver. Real life drivers often exhibit power compression at power levels that are a fraction (1/8th or less) of their rated power. So all else the same, a less efficient driver will be less dynamic and have higher distortion.

With lighter drivers, the -3 dB point of the final system tends to be a lot higher in frequency, which looks bad. But what is happening in reality is that the lighter woofer is putting out a lot more sound in the higher frequencies. The added mass only actually increases output slightly in the region of the resonance by increasing its Q or its tendency to store energy. Instead, the frequency response rolls off more gradually. This is often a *good* thing because the room gain in smaller listening rooms can compensate for a gentler roll-off, leading to a flatter in-room response. Furthermore, electronic EQ can be used to smooth things out further, which I *highly recommended* anyway for quality bass because your room messes up the response so severely.

But because buyers are obsessed with "flat response" and a -3 dB point in the bass that's as low as possible (even when they plan to use subs), passive speaker designs are often very compromised when it comes to dynamics. So my argument is that, for any given woofers, lower extension usually comes with the price of lower sensitivity and efficiency.

And for what it's worth (it's my opinion), I don't think 88.5 dB sensitivity is necessarily reasonable. This could be 88.5 dB/2.83V with 4 ohm impedance measured in anechoic half-space. Realistic efficiency may be considerably lower. Depending on the nature of the sound, some continuous sounds at 80 dB and up will likely cause hearing damage. However, not all sounds are equal. The ears can and routinely does tolerate transients at *much higher* SPL. Sounds with transient peaks of 100 dB and higher are probably encountered routinely in your home and your surroundings. They occur in many live music performances, acoustic or otherwise. Larger assemblies in larger halls can generate ever higher transient SPL. In the U.S., the OSHA regulations most people are familiar with apply to sounds that are measured continuously, using a "slow" meter. For transient impact noise, OSHA does not mandate hearing protection until SPL reaches 140 dB. 140 dB! Can your speakers do that?

As far as compressed dynamics are concerned, it can be very hard to hear this happen a system unless you are very familiar with the same recording on a system that does not compress. Likewise, as you boost the volume and distortion increases, you will likely perceive the increased loudness from the distortion before you'll perceive the distortion for what it is. Whereas solid state amps usually begin distorting quite abruptly as you approach their limits, the increased distortion in speaker drivers shows up more gradually as you push the volume. It might make it seem to sound better because of the "warmth" of the extra harmonics, like using a tube stage. But it will also sound louder than it should also. You may notice the music get really loud but not realize that it's because the drivers are being pushed.

Anyway, these are just my opinions. Before I built my high sensitivity speakers, I wondered if I would really benefit from the extra dynamics given that I was coming from 92 dB/2.83V/8 ohm speakers running on an XPA-5. I figured I'd notice an improvement on some of the some ultra high dynamic range stuff I've got, some movie soundtracks, and stuff played at ear-bleed levels. I was pleasantly surprised to experience dynamic improvement even at medium playback levels with most content. Indeed, it's enough that I almost wish I did pairs of 8 ohm woofers instead of a single 4, but instead, I plan to augment their sound with that from high-end custom mid-bass subs that can play up into the lower mid range. So I would say that you don't know that you're missing dynamics until you hear what you're missing. The more dynamic system will be more effortless, natural, and realistic. I believe lack of accurate dynamics is one of the biggest reasons barriers to getting a recording to sound like real-life sound. The weakness in the signal chain is almost always in the speakers and/or amps rather than the recording chain or the media format.

Seriously, why buy an Emotiva amp, except to get more dynamic capability? But what does something like a 1000W/channel XPA-1 get you over a 100W/channel stereo amp built into a receiver? The answer is 10 dB more dynamics minus the lost output due to power compression by having the voice coil heat up 10X faster when pulling 1000W vs. 100W. (Oh, and the potential loss and/or distortion due to driver over-excursion if that power is enough to push things too far). Big amps are good to have for "reserve power", but higher speaker efficiency is the real key to getting accurate, realistic dynamics.

[garbulky]

sme
"Seriously, why buy an Emotiva amp, except to get more dynamic capability? But what does something like a 1000W/channel XPA-1 get you over a 100W/channel stereo amp built into a receiver? The answer is 10 dB more dynamics minus the lost output due to power compression by having the voice coil heat up 10X faster when pulling 1000W vs. 100W. (Oh, and the potential loss and/or distortion due to driver over-excursion if that power is enough to push things too far). Big amps are good to have for "reserve power", but higher speaker efficiency is the real key to getting accurate, realistic dynamics."

Agreed on more efficient speakers can sound better. But if one feels that the reason for the XPA-1 is solely due to more horsepower. Then why spend so much for it? There are plenty of high pwoer class D alternatives that sell for much much less. If your speakers are bi ampable you can get two class D alternatives for less - like the Crown amps.

Imo the advantage of the XPA-1 is - yes horsepower - but also really good quality sound. I've heard amps as powerful - and more - than the XPA-1. They didn't sound as good. And the receivers I listened to didn't sound as good at any volume level.

[yves]

Jul 19, 2016 5:06:37 GMT -5 sme said:

To clarify about woofers with more mass. Mass does not harm accuracy, at least not directly. Adding mass decreases the resonance frequency and increases the Q of the driver, which tends to increase sensitivity in the region of the resonance frequency of whatever alignment is chosen. Another way to think of it is that adding mass lowers the -3 dB point in the response. However, adding mass comes with a big cost which is reduced sensitivity and efficiency for the most of the rest of the frequency range. The reduced efficiency can harm accuracy because the coil needs a lot more power to get the same output from the driver. Real life drivers often exhibit power compression at power levels that are a fraction (1/8th or less) of their rated power. So all else the same, a less efficient driver will be less dynamic and have higher distortion.

With lighter drivers, the -3 dB point of the final system tends to be a lot higher in frequency, which looks bad. But what is happening in reality is that the lighter woofer is putting out a lot more sound in the higher frequencies. The added mass only actually increases output slightly in the region of the resonance by increasing its Q or its tendency to store energy. Instead, the frequency response rolls off more gradually. This is often a *good* thing because the room gain in smaller listening rooms can compensate for a gentler roll-off, leading to a flatter in-room response. Furthermore, electronic EQ can be used to smooth things out further, which I *highly recommended* anyway for quality bass because your room messes up the response so severely.

But because buyers are obsessed with "flat response" and a -3 dB point in the bass that's as low as possible (even when they plan to use subs), passive speaker designs are often very compromised when it comes to dynamics. So my argument is that, for any given woofers, lower extension usually comes with the price of lower sensitivity and efficiency.

And for what it's worth (it's my opinion), I don't think 88.5 dB sensitivity is necessarily reasonable. This could be 88.5 dB/2.83V with 4 ohm impedance measured in anechoic half-space. Realistic efficiency may be considerably lower. Depending on the nature of the sound, some continuous sounds at 80 dB and up will likely cause hearing damage. However, not all sounds are equal. The ears can and routinely does tolerate transients at *much higher* SPL. Sounds with transient peaks of 100 dB and higher are probably encountered routinely in your home and your surroundings. They occur in many live music performances, acoustic or otherwise. Larger assemblies in larger halls can generate ever higher transient SPL. In the U.S., the OSHA regulations most people are familiar with apply to sounds that are measured continuously, using a "slow" meter. For transient impact noise, OSHA does not mandate hearing protection until SPL reaches 140 dB. 140 dB! Can your speakers do that?

As far as compressed dynamics are concerned, it can be very hard to hear this happen a system unless you are very familiar with the same recording on a system that does not compress. Likewise, as you boost the volume and distortion increases, you will likely perceive the increased loudness from the distortion before you'll perceive the distortion for what it is. Whereas solid state amps usually begin distorting quite abruptly as you approach their limits, the increased distortion in speaker drivers shows up more gradually as you push the volume. It might make it seem to sound better because of the "warmth" of the extra harmonics, like using a tube stage. But it will also sound louder than it should also. You may notice the music get really loud but not realize that it's because the drivers are being pushed.

Anyway, these are just my opinions. Before I built my high sensitivity speakers, I wondered if I would really benefit from the extra dynamics given that I was coming from 92 dB/2.83V/8 ohm speakers running on an XPA-5. I figured I'd notice an improvement on some of the some ultra high dynamic range stuff I've got, some movie soundtracks, and stuff played at ear-bleed levels. I was pleasantly surprised to experience dynamic improvement even at medium playback levels with most content. Indeed, it's enough that I almost wish I did pairs of 8 ohm woofers instead of a single 4, but instead, I plan to augment their sound with that from high-end custom mid-bass subs that can play up into the lower mid range. So I would say that you don't know that you're missing dynamics until you hear what you're missing. The more dynamic system will be more effortless, natural, and realistic. I believe lack of accurate dynamics is one of the biggest reasons barriers to getting a recording to sound like real-life sound. The weakness in the signal chain is almost always in the speakers and/or amps rather than the recording chain or the media format.

Seriously, why buy an Emotiva amp, except to get more dynamic capability? But what does something like a 1000W/channel XPA-1 get you over a 100W/channel stereo amp built into a receiver? The answer is 10 dB more dynamics minus the lost output due to power compression by having the voice coil heat up 10X faster when pulling 1000W vs. 100W. (Oh, and the potential loss and/or distortion due to driver over-excursion if that power is enough to push things too far). Big amps are good to have for "reserve power", but higher speaker efficiency is the real key to getting accurate, realistic dynamics.

Like I said you are just ignoring material strength, cone shape, damping, quality of the voice coil / its ability to dissipate that extra amount of heat, the magnet, the cabinet, etc. etc.. www.audioholics.com/loudspeaker-design/loudspeaker-drivers/diaphragm-material
Further, a speaker doesn't need to attain 140 dB SPL at listening position. Around 115 dB is a much more realistic figure. Reason I know there's no noticeable distortion coming from my speakers even at high SPL is they can go MUCH louder than the loudest you will ever want to listen to anything, and can do so without any audible sign of gradually increasing distortion. Dynamics on these speakers are far excellent. You don't know what you are missing until you have heard them in person. These are just *my* opinions. Oh and, if you can't hear many differences in the recording chain or the media format, then that's because my opinions are obviously always necessarily 150 percent correct.

[gzubeck]

What about the quality of the recording? I have about 89 db speakers (sb acoustics) and when I hear really good audio they come alive. I really enjoy listening to well recorded movie and television soundtracks on my speakers. Try listening to the opening soundtrack of "Marcella" on Netflix (British detective series). The base is just plain fun...

Unless you purchase professional drivers or boutique tube speaker drivers its hard to find highly efficient drivers at 98 db.

[sme]

Jul 19, 2016 9:36:08 GMT -5 garbulky said:

sme Agreed on more efficient speakers can sound better. But if one feels that the reason for the XPA-1 is solely due to more horsepower. Then why spend so much for it? There are plenty of high pwoer class D alternatives that sell for much much less. If your speakers are bi ampable you can get two class D alternatives for less - like the Crown amps.

Imo the advantage of the XPA-1 is - yes horsepower - but also really good quality sound. I've heard amps as powerful - and more - than the XPA-1. They didn't sound as good. And the receivers I listened to didn't sound as good at any volume level.

Good question.  I think that for a lot of buyers, it's about the prestige of owning mono-blocks and/or class A capability.  IMO, these features have negligible impact on sound quality, but that doesn't seem to matter for a lot of people.

For me personally?  Lack of noisy fans is one good reason.  There are some class D pro-style options that run without fans but they are often both expensive and limited in power output.  In any case, I already owned an XPA-5, and there weren't actually a lot of other options for getting a healthy amount of power for 5 channels into 4U space with no fans.  Since I made my purchases, I've learned more about what's on the market and seen some new products come out.  One of these is the SpeakerPower SP4-2800 amp (4 x 700W into 4 ohm ACD in a 2U, with "quiet fan" option), which I'm buying to power the mid-bass units I'm building.  Of course, it'll still set you back $2k, and it's idle draw is similar to an XPA-5, so provided that I never hit the limits of my XPA-5 it's probably not worth it for me to change anything at this point.

I won't try to argue that all amps sound the same because most people already have a set opinion on this point.  And anyway, I honestly don't know if all amps sound the same.  I do know that if a solid state amp is designed to sound neutral and is competently implemented, then there shouldn't be any audible differences.  And even if they were audible under strictly controlled conditions, these differences would still be completely swamped by the damage done to the signal by the speakers and the room acoustics.  If you really believe that some amps sound better than others, can you explain why?  I mean, can you point to a measurement that reveals a difference?  Now, what happens if you try to compare two amps using in-room measurements?  Any differences are almost certainly overwhelmed.  For the most part, moving your head a few inches changes the sound a lot more than changing amps.  Likewise, power compression in a speaker driver changes the sound a lot more than different amps do.  I don't really have golden ears, so maybe there are differences to be heard that I just don't pick up on.  I don't really care because my goal is for my system to sound better to everyone who listens to it, not just those with golden ears.  This is what I recommend.  Trust me, it helps with WAF a lot when *she* can hear the differences too.

[pedrocols]

Jul 22, 2016 21:18:27 GMT -5 sme said:

Jul 19, 2016 9:36:08 GMT -5 garbulky said:

sme Agreed on more efficient speakers can sound better. But if one feels that the reason for the XPA-1 is solely due to more horsepower. Then why spend so much for it? There are plenty of high pwoer class D alternatives that sell for much much less. If your speakers are bi ampable you can get two class D alternatives for less - like the Crown amps.

Imo the advantage of the XPA-1 is - yes horsepower - but also really good quality sound. I've heard amps as powerful - and more - than the XPA-1. They didn't sound as good. And the receivers I listened to didn't sound as good at any volume level.

Good question.  I think that for a lot of buyers, it's about the prestige of owning mono-blocks and/or class A capability.  IMO, these features have negligible impact on sound quality, but that doesn't seem to matter for a lot of people.

For me personally?  Lack of noisy fans is one good reason.  There are some class D pro-style options that run without fans but they are often both expensive and limited in power output.  In any case, I already owned an XPA-5, and there weren't actually a lot of other options for getting a healthy amount of power for 5 channels into 4U space with no fans.  Since I made my purchases, I've learned more about what's on the market and seen some new products come out.  One of these is the SpeakerPower SP4-2800 amp (4 x 700W into 4 ohm ACD in a 2U, with "quiet fan" option), which I'm buying to power the mid-bass units I'm building.  Of course, it'll still set you back $2k, and it's idle draw is similar to an XPA-5, so provided that I never hit the limits of my XPA-5 it's probably not worth it for me to change anything at this point.

I won't try to argue that all amps sound the same because most people already have a set opinion on this point.  And anyway, I honestly don't know if all amps sound the same.  I do know that if a solid state amp is designed to sound neutral and is competently implemented, then there shouldn't be any audible differences.  And even if they were audible under strictly controlled conditions, these differences would still be completely swamped by the damage done to the signal by the speakers and the room acoustics.  If you really believe that some amps sound better than others, can you explain why?  I mean, can you point to a measurement that reveals a difference?  Now, what happens if you try to compare two amps using in-room measurements?  Any differences are almost certainly overwhelmed.  For the most part, moving your head a few inches changes the sound a lot more than changing amps.  Likewise, power compression in a speaker driver changes the sound a lot more than different amps do.  I don't really have golden ears, so maybe there are differences to be heard that I just don't pick up on.  I don't really care because my goal is for my system to sound better to everyone who listens to it, not just those with golden ears.  This is what I recommend.  Trust me, it helps with WAF a lot when *she* can hear the differences too.

You can potentially fail miserably in trying to make your system to the liking of everyone. My goal is for my system to sound good to me...

[sme]

Jul 19, 2016 17:41:41 GMT -5 yves said:

Like I said you are just ignoring material strength, cone shape, damping, quality of the voice coil / its ability to dissipate that extra amount of heat, the magnet, the cabinet, etc. etc.. www.audioholics.com/loudspeaker-design/loudspeaker-drivers/diaphragm-material
Further, a speaker doesn't need to attain 140 dB SPL at listening position. Around 115 dB is a much more realistic figure. Reason I know there's no noticeable distortion coming from my speakers even at high SPL is they can go MUCH louder than the loudest you will ever want to listen to anything, and can do so without any audible sign of gradually increasing distortion. Dynamics on these speakers are far excellent. You don't know what you are missing until you have heard them in person. These are just *my* opinions. Oh and, if you can't hear many differences in the recording chain or the media format, then that's because my opinions are obviously always necessarily 150 percent correct.

Cone material strength, cone shape, and damping have fairly minor impact on efficiency in most cases.  These things do matter a lot for sound quality, particularly at higher frequencies.  Voice coil design is very complicated, but fundamentally there are big trade-offs between power handling vs. coil mass with efficiency loss largely washing out the benefit of increased power handling.  Bigger coils also tend to come with more inductance, which mainly effects frequencies higher frequencies may be the biggest cause of audible distortion in drivers. With subwoofer drivers, these trade-offs are more acceptable because the sub won't be used to play very high.  But in a passive system, the sensitivity of the woofer essentially sets the sensitivity of the system because otherwise the system would not measure flat.  So for a given cabinet design and woofer size, the lower the "-3 dB" point, the more power dissipated in the woofer as well as potentially the crossovers and even the amp itself.  It's a little less bad in a 3-way at least because more of the mids will escape the consequences of power compression and current-modulated distortion, but it's still much better to use a much more efficient woofer with a higher "-3 dB point"  and dedicate a subwoofer with much larger voice coil and larger amp handle the lowest frequencies.  If form factor is concerned, a good design option is for the sub to be built into the bottom of the tower with its own integrated amp.

Yet another example of passive system signal shaping that harms performance is baffle step compensation (BSC).  BSC is typically used in a passive crossover to compensate for the loss of directivity of the speakers at low frequencies.  Because the speaker continues to produce the same sound power, the loss of directivity means lower SPL for frequencies below the baffle step.  With a passive circuit, this involves reducing the sensitivity above a chosen frequency.  While some BSC is a good idea with most passive speaker designs, it involves making a lot of guesses about the nature of the room and speaker placements.  Unfortunately, rooms differ so much that even with consistent placements, BSC is likely to be a very crude correction.  On the other hand, an active system with room correction like Dirac can do BSC electronically right at the point that it's needed and do so without giving up headroom in the higher frequencies.

My overall point is that most passive speakers involve significant design compromises, both because they are passive and because they must cater to a market that expects flat frequency response out to as low a frequency as possible.  Mass loading of woofers is but one signal shaping approach taken to achieve these goals.

I agree that 140 dB is probably more than is needed, but my point was that the ear's sensitivity to transient vs. continuous sounds differs extremely.  For reference level playback of theatrical content, 120 dB is good figure to aim for in the sub section, but more is better.  There *is* BD content in the wild that demands more than 120 dB from the subs at reference level, depending on how your bass management is configured.  Also keep in mind that you will probably want to use DSP.  I think Dirac will boost up to 6 dB, frequency-by-frequency, and the combined effects of the filter on complex signals can demand even more headroom than that.  So now we're talking more like 130 dB, but it really really depends on what your room is doing and where they are placed.  Every room is different and in-room measurements are crucial to get the best results.  And in reality, most people can go that far, so "as much sub as you can get" is often the best advice for home theater.

I'd rather not argue about how your speakers sound, and you are right.  I have no idea.  They could be very capable with a big enough amp.  I do know that I felt exactly the same way as you do about my 92 dB sensitive Hsu speakers.  I still have a high opinion of the Hsu Speakers as their performance is fantastic for their price (starting at $150/ea).   I've heard very few speakers that rival them, but ultimately through years of listening and measurement, I became aware of several of their flaws.  I was sold on the concept of the controlled directivity horn, and opted to try this design mostly for the (IMO state-of-the-art) SEOS horn.  The increase in headroom was not my primary goal.  I honestly thought I might notice a subtle improvement at the highest of listening levels with the most dynamic of soundtracks.  I was flat out wrong.  There is a world of difference in dynamic sound quality, even at moderate listening levels with highly compressed loudness war recordings.   It's actually a lot more obvious how compressed they are, as well.  With recordings with strong dynamics like some classical stuff, high end labels like Chesky Records, good movie soundtracks the difference is huge.  I'll never look back.  This is the closest I've come to having good quality recordings sound like a live acoustic event.

And again, the argument that you know you aren't distorting because you can play much louder doesn't really hold water.  Loudness is not the same as SPL.  This is a big deal.  In many cases, they are opposites.  To the extent that your system distorts or compresses, peak SPL is often decreased and at the same time, loudness will likely increase.  I've heard laptop speakers play loud enough to bother my ears.  Loudness means nothing.  A more constructive figure of merit would be what level you find to be too loud.  That laptop may have barely broke 70 dB, but it was very irritating.  OTOH, I can listen to drums pounding away at > 100 dB while not being irritated at all.  With my new speakers speakers, too loud is almost always a bit higher on the volume control. That's a real figure of merit as far as I'm concerned.  That strongly suggests that I'm getting more SPL and less loudness, which means I'm distorting less.  It sure does sound like that's the case.  It's not just me either.  My wife likes having the volume turned up more. 

But this is where we may just have to agree to disagree because unless you have in-room measurements or are relying on some kind of calibration, I have no idea what "loud" means for your circumstances.  Lest I appear to be a hypocrite myself, I will volunteer that my speakers are calibrated with -20 dbFS pink noise band limited to band-limited 500-2000 Hz at a level of 83 dBC, as per Bob Katz's recommendations.  This is equivalent or 2 dB less than the theatrical reference standard, depending on which expert you ask.  I calibrate this way with a slight house curve in place.  House curves are necessary to achieve proper in-room tonal balance and depend on the speakers, placements, and room acoustics.  Lively listening level for compressed music is -12 dB or lower.  A lot of said music is just too fatiguing to listen to at a high level for long.  Most recordings from the pre-digital days play well at -7 to -10.  Some older classical recordings play well at -5 dB.  Modern high fidelity recordings and a fair bit of content from the digital golden age of the mid to late 1980s often have enough dynamic range to enjoy at higher levels, as high as or higher than "0".  (As an aside, that period of the 1980s wasn't entirely golden as DACs/ADCs tended to suffer serious audible distortion, but the better dynamics makes this stuff far better than most modern stuff, in my opinion.)  I have a handful that don't really come to life until beyond "0 dB" like Kodo drumming and some Telarc.  Then there's unprocessed recordings like those made by Thomas Danley, largely to showcase his horns.  (Another state-of-the-art design.)  Examples include recordings of live fireworks or the sound of a Harley motorcycle with > 115 dB peaks, much of which reside above the subwoofer range.  The trickiest recording I have is probably the live Space Shuttle, recorded from 3 miles away at the point where they let tourists go and watch.  IIRC, this recording peaks at 126 dB with 120 dB @ 25 Hz and 115 dB @ 16 Hz all the way down to DC.  Very few systems in the world can accurately reproduce that recording.

[garbulky]

Jul 22, 2016 21:18:27 GMT -5 sme said:

Jul 19, 2016 9:36:08 GMT -5 garbulky said:

sme Agreed on more efficient speakers can sound better. But if one feels that the reason for the XPA-1 is solely due to more horsepower. Then why spend so much for it? There are plenty of high pwoer class D alternatives that sell for much much less. If your speakers are bi ampable you can get two class D alternatives for less - like the Crown amps.

Imo the advantage of the XPA-1 is - yes horsepower - but also really good quality sound. I've heard amps as powerful - and more - than the XPA-1. They didn't sound as good. And the receivers I listened to didn't sound as good at any volume level.

Good question.  I think that for a lot of buyers, it's about the prestige of owning mono-blocks and/or class A capability.  IMO, these features have negligible impact on sound quality, but that doesn't seem to matter for a lot of people.

For me personally?  Lack of noisy fans is one good reason.  There are some class D pro-style options that run without fans but they are often both expensive and limited in power output.  In any case, I already owned an XPA-5, and there weren't actually a lot of other options for getting a healthy amount of power for 5 channels into 4U space with no fans.  Since I made my purchases, I've learned more about what's on the market and seen some new products come out.  One of these is the SpeakerPower SP4-2800 amp (4 x 700W into 4 ohm ACD in a 2U, with "quiet fan" option), which I'm buying to power the mid-bass units I'm building.  Of course, it'll still set you back $2k, and it's idle draw is similar to an XPA-5, so provided that I never hit the limits of my XPA-5 it's probably not worth it for me to change anything at this point.

I won't try to argue that all amps sound the same because most people already have a set opinion on this point.  And anyway, I honestly don't know if all amps sound the same.  I do know that if a solid state amp is designed to sound neutral and is competently implemented, then there shouldn't be any audible differences.  And even if they were audible under strictly controlled conditions, these differences would still be completely swamped by the damage done to the signal by the speakers and the room acoustics.  If you really believe that some amps sound better than others, can you explain why?  I mean, can you point to a measurement that reveals a difference?  Now, what happens if you try to compare two amps using in-room measurements?  Any differences are almost certainly overwhelmed.  For the most part, moving your head a few inches changes the sound a lot more than changing amps.  Likewise, power compression in a speaker driver changes the sound a lot more than different amps do.  I don't really have golden ears, so maybe there are differences to be heard that I just don't pick up on.  I don't really care because my goal is for my system to sound better to everyone who listens to it, not just those with golden ears.  This is what I recommend.  Trust me, it helps with WAF a lot when *she* can hear the differences too.

You are quite right on a lot of points. The first is that room acoustics and speakers do way worse stuff to the signal than amps and electronics.
With my wife, I don't think she heard much difference as she didn't remark on the amp change much. I had gone from a UPA-2 to an XPA-1 gen 2. Though she is not really interested in speakers, which I think most of us can relate here, she on occasion does like good sound.


Can I point to a measurement that reveals a difference? I don't think I can. This is because of a few things. Namely I don't know how to interpret measurements to that extent and I wonder if they can be interpreted. For instance if I said the amp sounded like it revealed spatial dimensions better, how would I reveal that from measurements?

Now as to measured in room effect. This is more realistic. One of the differences I noticed is that there was more bass extension and more bass volume. This should probably be easy to measure. Before I was contemplating subs. The axioms got low but not dual subs low. Now the bass performance is better and also it feels "tighter" and cleaner. So this may be able to be measured.

How I usually compare amps is to be subjective. I have heard the XPA-2 gen 1 in the same room and the XPA-2 gen 2 and the XPA-1 gen 2 in a different room as well. I would say the XPA-2 gen 2 is very similar in sound signature to the XPA-1 gen 2 ....but it's not quite the same. The class A switch on the XPA-1 gen 2 does a bit better when revealing spatial dimensions and room acoustics in the recording. I think that is the biggest difference. Also placement and dynamic power feels like it has improved. The UPA-2 vs the XPA-1 gen 2 though I think the differences are more obvious than between the XPA-2 gen 2.

My thoughts on what makes it different?
For measurements class A can reveal a complete lack of crossover notch distortion. Current class AB amps have very low amounts of crossover notch distortion. But it is not eliminated. I have heard a Nakamichi stasis class A amp before. It had a very involving mid-range. However its power was a 100 watts and its limits did not allow it full control of the system. It produced a lit up from within sound in the mid range.
The fully balanced architecture does cut down on distortions especially when paired with fulyl balanced gear. However this has a pitfall that if the balanced architecture is not precisely matched, it could mess with the sound. I have heard that happen too on two preamps though I can't say if the balanced architecture is the culprit.

The other thing other than the monoblock capability, is that the XPA-1 has a huge power supply.
I have heard amps with smaller power supplies but that claim high power - mostly Crown's, and they simply can't keep the axiom speakers balanced from the bass to the treble. Usually it sounds like the mid range gets sucked up and there is straining in the bass. Shouty is a good descriptor. So maybe the ability to keep its current supply stable over a wide frequecy range and impedances might help explain the difference I hear.

[novisnick]

Jul 23, 2016 12:40:40 GMT -5 garbulky said:

Jul 22, 2016 21:18:27 GMT -5 sme said:

Good question.  I think that for a lot of buyers, it's about the prestige of owning mono-blocks and/or class A capability.  IMO, these features have negligible impact on sound quality, but that doesn't seem to matter for a lot of people.

For me personally?  Lack of noisy fans is one good reason.  There are some class D pro-style options that run without fans but they are often both expensive and limited in power output.  In any case, I already owned an XPA-5, and there weren't actually a lot of other options for getting a healthy amount of power for 5 channels into 4U space with no fans.  Since I made my purchases, I've learned more about what's on the market and seen some new products come out.  One of these is the SpeakerPower SP4-2800 amp (4 x 700W into 4 ohm ACD in a 2U, with "quiet fan" option), which I'm buying to power the mid-bass units I'm building.  Of course, it'll still set you back $2k, and it's idle draw is similar to an XPA-5, so provided that I never hit the limits of my XPA-5 it's probably not worth it for me to change anything at this point.

I won't try to argue that all amps sound the same because most people already have a set opinion on this point.  And anyway, I honestly don't know if all amps sound the same.  I do know that if a solid state amp is designed to sound neutral and is competently implemented, then there shouldn't be any audible differences.  And even if they were audible under strictly controlled conditions, these differences would still be completely swamped by the damage done to the signal by the speakers and the room acoustics.  If you really believe that some amps sound better than others, can you explain why?  I mean, can you point to a measurement that reveals a difference?  Now, what happens if you try to compare two amps using in-room measurements?  Any differences are almost certainly overwhelmed.  For the most part, moving your head a few inches changes the sound a lot more than changing amps.  Likewise, power compression in a speaker driver changes the sound a lot more than different amps do.  I don't really have golden ears, so maybe there are differences to be heard that I just don't pick up on.  I don't really care because my goal is for my system to sound better to everyone who listens to it, not just those with golden ears.  This is what I recommend.  Trust me, it helps with WAF a lot when *she* can hear the differences too.

You are quite right on a lot of points. The first is that room acoustics and speakers do way worse stuff to the signal than amps and electronics.
With my wife, I don't think she heard much difference as she didn't remark on the amp change much. I had gone from a UPA-2 to an XPA-1 gen 2. Though she is not really interested in speakers, which I think most of us can relate here, she on occasion does like good sound.


Can I point to a measurement that reveals a difference? I don't think I can. This is because of a few things. Namely I don't know how to interpret measurements to that extent and I wonder if they can be interpreted. For instance if I said the amp sounded like it revealed spatial dimensions better, how would I reveal that from measurements?

Now as to measured in room effect. This is more realistic. One of the differences I noticed is that there was more bass extension and more bass volume. This should probably be easy to measure. Before I was contemplating subs. The axioms got low but not dual subs low. Now the bass performance is better and also it feels "tighter" and cleaner. So this may be able to be measured.

How I usually compare amps is to be subjective. I have heard the XPA-2 gen 1 in the same room and the XPA-2 gen 2 and the XPA-1 gen 2 in a different room as well. I would say the XPA-2 gen 2 is very similar in sound signature to the XPA-1 gen 2 ....but it's not quite the same. The class A switch on the XPA-1 gen 2 does a bit better when revealing spatial dimensions and room acoustics in the recording. I think that is the biggest difference. Also placement and dynamic power feels like it has improved. The UPA-2 vs the XPA-1 gen 2 though I think the differences are more obvious than between the XPA-2 gen 2.

My thoughts on what makes it different?
For measurements class A can reveal a complete lack of crossover notch distortion. Current class AB amps have very low amounts of crossover notch distortion. But it is not eliminated. I have heard a Nakamichi stasis class A amp before. It had a very involving mid-range. However its power was a 100 watts and its limits did not allow it full control of the system. It produced a lit up from within sound in the mid range.
The fully balanced architecture does cut down on distortions especially when paired with fulyl balanced gear. However this has a pitfall that if the balanced architecture is not precisely matched, it could mess with the sound. I have heard that happen too on two preamps though I can't say if the balanced architecture is the culprit.

The other thing other than the monoblock capability, is that the XPA-1 has a huge power supply.
I have heard amps with smaller power supplies but that claim high power - mostly Crown's, and they simply can't keep the axiom speakers balanced from the bass to the treble. Usually it sounds like the mid range gets sucked up and there is straining in the bass. Shouty is a good descriptor. So maybe the ability to keep its current supply stable over a wide frequecy range and impedances might help explain the difference I hear.

If I may interject a thought here please, higher powered properly designed and constructed MONOBLOCKS do controll the phsical speaker much much better and therefore, to my ears, sounds much richer and more accurate then lessor amps.

Thank you gentalman. 

[yves]

Jul 23, 2016 4:52:55 GMT -5 sme said:

Jul 19, 2016 17:41:41 GMT -5 yves said:

Like I said you are just ignoring material strength, cone shape, damping, quality of the voice coil / its ability to dissipate that extra amount of heat, the magnet, the cabinet, etc. etc.. www.audioholics.com/loudspeaker-design/loudspeaker-drivers/diaphragm-material
Further, a speaker doesn't need to attain 140 dB SPL at listening position. Around 115 dB is a much more realistic figure. Reason I know there's no noticeable distortion coming from my speakers even at high SPL is they can go MUCH louder than the loudest you will ever want to listen to anything, and can do so without any audible sign of gradually increasing distortion. Dynamics on these speakers are far excellent. You don't know what you are missing until you have heard them in person. These are just *my* opinions. Oh and, if you can't hear many differences in the recording chain or the media format, then that's because my opinions are obviously always necessarily 150 percent correct.

Cone material strength, cone shape, and damping have fairly minor impact on efficiency in most cases.  These things do matter a lot for sound quality, particularly at higher frequencies.  Voice coil design is very complicated, but fundamentally there are big trade-offs between power handling vs. coil mass with efficiency loss largely washing out the benefit of increased power handling.  Bigger coils also tend to come with more inductance, which mainly effects frequencies higher frequencies may be the biggest cause of audible distortion in drivers. With subwoofer drivers, these trade-offs are more acceptable because the sub won't be used to play very high.  But in a passive system, the sensitivity of the woofer essentially sets the sensitivity of the system because otherwise the system would not measure flat.  So for a given cabinet design and woofer size, the lower the "-3 dB" point, the more power dissipated in the woofer as well as potentially the crossovers and even the amp itself.  It's a little less bad in a 3-way at least because more of the mids will escape the consequences of power compression and current-modulated distortion, but it's still much better to use a much more efficient woofer with a higher "-3 dB point"  and dedicate a subwoofer with much larger voice coil and larger amp handle the lowest frequencies.  If form factor is concerned, a good design option is for the sub to be built into the bottom of the tower with its own integrated amp.

Yet another example of passive system signal shaping that harms performance is baffle step compensation (BSC).  BSC is typically used in a passive crossover to compensate for the loss of directivity of the speakers at low frequencies.  Because the speaker continues to produce the same sound power, the loss of directivity means lower SPL for frequencies below the baffle step.  With a passive circuit, this involves reducing the sensitivity above a chosen frequency.  While some BSC is a good idea with most passive speaker designs, it involves making a lot of guesses about the nature of the room and speaker placements.  Unfortunately, rooms differ so much that even with consistent placements, BSC is likely to be a very crude correction.  On the other hand, an active system with room correction like Dirac can do BSC electronically right at the point that it's needed and do so without giving up headroom in the higher frequencies.

My overall point is that most passive speakers involve significant design compromises, both because they are passive and because they must cater to a market that expects flat frequency response out to as low a frequency as possible.  Mass loading of woofers is but one signal shaping approach taken to achieve these goals.

I agree that 140 dB is probably more than is needed, but my point was that the ear's sensitivity to transient vs. continuous sounds differs extremely.  For reference level playback of theatrical content, 120 dB is good figure to aim for in the sub section, but more is better.  There *is* BD content in the wild that demands more than 120 dB from the subs at reference level, depending on how your bass management is configured.  Also keep in mind that you will probably want to use DSP.  I think Dirac will boost up to 6 dB, frequency-by-frequency, and the combined effects of the filter on complex signals can demand even more headroom than that.  So now we're talking more like 130 dB, but it really really depends on what your room is doing and where they are placed.  Every room is different and in-room measurements are crucial to get the best results.  And in reality, most people can go that far, so "as much sub as you can get" is often the best advice for home theater.

I'd rather not argue about how your speakers sound, and you are right.  I have no idea.  They could be very capable with a big enough amp.  I do know that I felt exactly the same way as you do about my 92 dB sensitive Hsu speakers.  I still have a high opinion of the Hsu Speakers as their performance is fantastic for their price (starting at $150/ea).   I've heard very few speakers that rival them, but ultimately through years of listening and measurement, I became aware of several of their flaws.  I was sold on the concept of the controlled directivity horn, and opted to try this design mostly for the (IMO state-of-the-art) SEOS horn.  The increase in headroom was not my primary goal.  I honestly thought I might notice a subtle improvement at the highest of listening levels with the most dynamic of soundtracks.  I was flat out wrong.  There is a world of difference in dynamic sound quality, even at moderate listening levels with highly compressed loudness war recordings.   It's actually a lot more obvious how compressed they are, as well.  With recordings with strong dynamics like some classical stuff, high end labels like Chesky Records, good movie soundtracks the difference is huge.  I'll never look back.  This is the closest I've come to having good quality recordings sound like a live acoustic event.

And again, the argument that you know you aren't distorting because you can play much louder doesn't really hold water.  Loudness is not the same as SPL.  This is a big deal.  In many cases, they are opposites.  To the extent that your system distorts or compresses, peak SPL is often decreased and at the same time, loudness will likely increase.  I've heard laptop speakers play loud enough to bother my ears.  Loudness means nothing.  A more constructive figure of merit would be what level you find to be too loud.  That laptop may have barely broke 70 dB, but it was very irritating.  OTOH, I can listen to drums pounding away at > 100 dB while not being irritated at all.  With my new speakers speakers, too loud is almost always a bit higher on the volume control. That's a real figure of merit as far as I'm concerned.  That strongly suggests that I'm getting more SPL and less loudness, which means I'm distorting less.  It sure does sound like that's the case.  It's not just me either.  My wife likes having the volume turned up more. 

But this is where we may just have to agree to disagree because unless you have in-room measurements or are relying on some kind of calibration, I have no idea what "loud" means for your circumstances.  Lest I appear to be a hypocrite myself, I will volunteer that my speakers are calibrated with -20 dbFS pink noise band limited to band-limited 500-2000 Hz at a level of 83 dBC, as per Bob Katz's recommendations.  This is equivalent or 2 dB less than the theatrical reference standard, depending on which expert you ask.  I calibrate this way with a slight house curve in place.  House curves are necessary to achieve proper in-room tonal balance and depend on the speakers, placements, and room acoustics.  Lively listening level for compressed music is -12 dB or lower.  A lot of said music is just too fatiguing to listen to at a high level for long.  Most recordings from the pre-digital days play well at -7 to -10.  Some older classical recordings play well at -5 dB.  Modern high fidelity recordings and a fair bit of content from the digital golden age of the mid to late 1980s often have enough dynamic range to enjoy at higher levels, as high as or higher than "0".  (As an aside, that period of the 1980s wasn't entirely golden as DACs/ADCs tended to suffer serious audible distortion, but the better dynamics makes this stuff far better than most modern stuff, in my opinion.)  I have a handful that don't really come to life until beyond "0 dB" like Kodo drumming and some Telarc.  Then there's unprocessed recordings like those made by Thomas Danley, largely to showcase his horns.  (Another state-of-the-art design.)  Examples include recordings of live fireworks or the sound of a Harley motorcycle with > 115 dB peaks, much of which reside above the subwoofer range.  The trickiest recording I have is probably the live Space Shuttle, recorded from 3 miles away at the point where they let tourists go and watch.  IIRC, this recording peaks at 126 dB with 120 dB @ 25 Hz and 115 dB @ 16 Hz all the way down to DC.  Very few systems in the world can accurately reproduce that recording.

Glad to see you understood my point that very high speaker sensitivity can and in practice often does restrict rather than help to improve the final sound, as there are way too many complex factors at play for one to be able to always stick to generalized conclusions of a certain kind. Higher numbers don't translate to better fidelity, proven traditional designs in conjunction with real innovations do.

This is what I look for in an audio system before letting my ears do the final judging. To add subwoofers to existing speakers is to re-design speakers, it is a path the end result of which is not necessarily always worth the patience and effort spent because a speaker is a complex system. Based on my personal listening experiences, I am in the camp of "adding subs doesn't add enough to stereo music albums I like except if I can break the bank and someone comes along and fixes that problem". As for your question what "loud" means in my circumstance, it means guys standing outside on the driveway in front of my window front side of the house listening to my sourced from vinyl LP copy of Pantera ~ Vulgar Display of Power thinking there's a serious live event happening in the back yard.

[Axis]

Can someone tell my why they made these new Airmotiv passive speakers 4 ohm ?

[sme]

Easy. So you can get the most power out of your Emotiva amp.

[sme]

Jul 23, 2016 13:02:37 GMT -5 novisnick said:

If I may interject a thought here please, higher powered properly designed and constructed MONOBLOCKS do controll the phsical speaker much much better and therefore, to my ears, sounds much richer and more accurate then lessor amps.

Thank you gentalman. 

Actually, unless you are running tube amps, the biggest parameter that determines how well the amp controls the driver is the motor strength of the driver in most cases.  If the motor is very strong, then current flowing into coil couples very strongly to acceleration of the cone motion.  Likewise, in the absence of signal, the electrical brake will be very strong.  Low inductance and a lack of a passive crossover are also big pluses, but motor strength is key.  In some sense, the reason why increased motor strength lowers Q is because it dissipates the energy of mechanical resonances much faster.  So here's yet another reason to favor systems that aim for a gradual, low Q roll-off rather than a low "-3 dB" point.

For those who are interested in speakers with high dynamic range, I already mentioned the Tekton Pendragon.  Another commercial option for a high dynamics is Seaton Sound and his Catalyst and Spark.  These are pretty pricey speakers.  For those willing to glue, clamp, and finish, I highly recommend looking at DIYSG.  The SEOS family of horns can be bought from there, but they also offer CNC pre-cut kits for a variety of speakers of different sizes, mostly using the SEOS but also some without horns.  Of course, the speakers using the SEOS are the most sensitive with several passive designs available with 99 dB/2.83V sensitivity, and depending on size, options that extend pretty low.

[yves]

www.audioholics.com/loudspeaker-design/audio-measurements/image_view_fullscreen

P.S. - It's very easy to manipulate loudspeaker response curves and data by:

⚫ Displaying max output levels without specifying distortion levels or whether or not the loudspeaker is suffering from audible mechanical noises and/or distress under such testing levels

www.audioholics.com/loudspeaker-design/audio-measurements/audio-measurement-techniques-cont

[pedrocols]

Jul 24, 2016 2:25:38 GMT -5 sme said:

Jul 23, 2016 13:02:37 GMT -5 novisnick said:

If I may interject a thought here please, higher powered properly designed and constructed MONOBLOCKS do controll the phsical speaker much much better and therefore, to my ears, sounds much richer and more accurate then lessor amps.

Thank you gentalman. 

Actually, unless you are running tube amps, the biggest parameter that determines how well the amp controls the driver is the motor strength of the driver in most cases.  If the motor is very strong, then current flowing into coil couples very strongly to acceleration of the cone motion.  Likewise, in the absence of signal, the electrical brake will be very strong.  Low inductance and a lack of a passive crossover are also big pluses, but motor strength is key.  In some sense, the reason why increased motor strength lowers Q is because it dissipates the energy of mechanical resonances much faster.  So here's yet another reason to favor systems that aim for a gradual, low Q roll-off rather than a low "-3 dB" point.

For those who are interested in speakers with high dynamic range, I already mentioned the Tekton Pendragon.  Another commercial option for a high dynamics is Seaton Sound and his Catalyst and Spark.  These are pretty pricey speakers.  For those willing to glue, clamp, and finish, I highly recommend looking at DIYSG.  The SEOS family of horns can be bought from there, but they also offer CNC pre-cut kits for a variety of speakers of different sizes, mostly using the SEOS but also some without horns.  Of course, the speakers using the SEOS are the most sensitive with several passive designs available with 99 dB/2.83V sensitivity, and depending on size, options that extend pretty low.

I wonder what can be a good use for these kind of speaker design if the listener, like myself, isn't interested in reference listening sessions? Maybe I am not aware of how many people listen at rock concert levels in the privacy of their homes which in reality is not good for your ears.

[yves]

Jul 24, 2016 9:54:32 GMT -5 pedrocols said:

Maybe I am not aware of how many people listen at rock concert levels in the privacy of their homes which in reality is not good for your ears.

I know that in reality it is not good for my ears. But my Westone ES60s give me 28 dB passive attenuation so no problemo!

[pedrocols]

Jul 24, 2016 10:03:46 GMT -5 yves said:

Jul 24, 2016 9:54:32 GMT -5 pedrocols said:

Maybe I am not aware of how many people listen at rock concert levels in the privacy of their homes which in reality is not good for your ears.

I know that in reality it is not good for my ears. But my Westone ES60s give me 28 dB passive attenuation so no problemo!

Good alternative for not to disturbed your neighbors...

[yves]

Jul 24, 2016 10:29:06 GMT -5 pedrocols said:

Jul 24, 2016 10:03:46 GMT -5 yves said:

I know that in reality it is not good for my ears. But my Westone ES60s give me 28 dB passive attenuation so no problemo!

Good alternative for not to disturbed your neighbors...

Nah. They're custom fit so my neighbors can't wear them.

[DYohn]

Much more important to audible distortion than mass is voice coil inductance.