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Post by Boomzilla on Aug 21, 2021 16:11:23 GMT -5
I've an audio amigo whose subwoofers sound better than any I've ever heard. They not only blend into his satellites without any speed or frequency indication, but they also are VERY fast, VERY deep, and have low enough stored energy that they don't overhang any sounds. Not only do these subs work this magic at thunderous levels, but they do so at whisper-soft levels as well. This audio amigo holds very strong opinions about why his subs are so articulate, although I know for a fact that some of his theories are wrong. But whether or not his "why's" are accurate, his subs' performance outdistances any other system I've heard. And just to be clear, I am NOT discussing home theater in this thread - this is solely about 2.2 music performance. His subs use 10" RTR woofers from a Crown speaker system. Each (large) box has two or three drivers in it. Here are my audio amigo's subwoofer theories (please note that *** I *** don't necessarily espouse these, and that, in fact, I'm convinced that some are wrong): 1. To be articulate, a sub woofer driver must be low mass. This precludes any heavy cones, huge voice coils, or stiff suspensions. In fact, the lighter and "floppier" the driver system, the less energy it will store and the quicker the driver can respond to low-level signals. In fact, I believe this to be a fallacy. Mr. DYohn has pointed out that regardless of the cone mass and suspension compliance, sufficient amperage through the voice coil will overcome all obstacles, and provide precise cone placement. I understand the sense of this, but somehow my audio amigo has obtained fantastic results with tiny voice coils. 2. Because the sub woofer driver must be low mass, any cone sizes of more than 10-inches will inhibit subwoofer quickness. The cones flexibility also rises exponentially with size, introducing distortion. If you need to move more air, use more cones. See the response to claim one above for comments on cone mass, but if a cone can be made sufficiently rigid, I don't think that it would necessarily introduce distortion. 3. Sealed boxes are superior to ported boxes. I have no opinion on this one... 4. A high quality external amplifier optimized for current delivery is superior to any built-in plate amp on the market. I haven't heard all the plate amps around, and so can't comment on this. Audio amigo uses an Electron Kinetics Eagle 7a to drive his two subs. And the results are breathtaking. 5. Virtually ALL commercial, self-powered subwoofers use insufficient cabinet space (for WAF) and then try to compensate with more power. This tends to produce a resonant and peaky frequency response intended to provide maximum output for movie transients, but which is FAR too resonant for music use. The peaked frequency response of typical HT subs is an insurmountable obstacle for music. I tend to agree with this one. And the cheaper the subwoofer, the more the frequency response peak. 6. You can't buy a commercial cabinet that is sufficiently braced, and that doesn't sing along with the driver(s I also agree with this one - cabinet bracing is not only EXPENSIVE, but also interferes with the internal volume of the subwoofer to the point where additional cabinet volume is required to compensate for the volume of the bracing. 7. Typical HT subs begin rolling off far too soon. Even with the THX-standard 80 Hz. crossover the average sub has frequency response that drops like a stone even before you reach 80 Hz. Therefore the electronic crossover tends to leave a gap between the satellites and the subwoofer. I'd agree with this one too. Thoughts? Boom |
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Post by donh50 on Aug 21, 2021 16:38:12 GMT -5
I disagree with every one of those but have learned the painful lesson that technical reasons matter not to most audiophiles.
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Post by ttocs on Aug 21, 2021 18:23:54 GMT -5
Well, that's certainly a big bag of absolutes all in one place.
There's a lot of ways to make frequencies bounce. And I would wager that all of what your amigo espouses are correct for your amigo and lots of other folks as well, but it never ceases to amaze me as to how someone else will come along and get things to work differently but still sound amazing.
While I would say that I prefer sealed to ported or sealed/w/passive radiators, I've heard each design sound amazing. Wilson's Subsonic subs have ports, drivers which are lightweight for their size, are very well braced, built for music, use external amps, and sound incredible. My room isn't big enough.
I whole heartedly agree with the statement about subs designed for HT should be used for HT, except, that they "can" be integrated into systems when using their strengths as assets. Just use them for the frequencies they do best, and use other subs for the same reason. So, this is just to point out that the destination can be found from more than just one path.
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Post by 405x5 on Aug 21, 2021 18:25:31 GMT -5
When I run the infamous THX demonstration the sweep is as smooth as a baby’s behind from the high end all the way down to 15hz. There are MANY ways to get there and personal preference rules with no boundaries.
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Post by Boomzilla on Aug 21, 2021 21:37:18 GMT -5
I disagree with every one of those but have learned the painful lesson that technical reasons matter not to most audiophiles. Might I ask that you select the axiom that you disagree with MOST STRONGLY, and then explain your reasons? I'd find that most helpful. Thanks - Boomzilla |
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Post by donh50 on Aug 21, 2021 22:44:37 GMT -5
I disagree with every one of those but have learned the painful lesson that technical reasons matter not to most audiophiles. Might I ask that you select the axiom that you disagree with MOST STRONGLY, and then explain your reasons? I'd find that most helpful. Thanks - Boomzilla I'll try, you may believe it or not (Ripley). I am not a speaker designer (my career took a much different path though I dabble in audio design) and, while I'll stand behind my opinions, these are general observations from experience (listening, measuring, etc.), some design, and ancient mostly-forgotten grad courses in acoustics. 1. To be articulate, a sub woofer driver must be low mass. This precludes any heavy cones, huge voice coils, or stiff suspensions. In fact, the lighter and "floppier" the driver system, the less energy it will store and the quicker the driver can respond to low-level signals. I do not know what "articulate" means to him but higher mass requires more driving force and better damping (lower amplifier output impedance). Lower mass is an admirable goal, but must be accompanied with increasing stiffness or distortion due to cone deflection will rise, eventually resulting in breakup modes (standing waves, peaks and valleys across the cone). More mass can be countered by a more powerful motor driving the cone. In contrast, the "floppier" the cone, th greater the distortion and at lower output (SPL) levels compared to a stiffer, heavier cone. The ideal would be infinitely stiff with zero mass, but for best performance one must trade mass, motor (amplifier) power, and distortion. 2. Because the sub woofer driver must be low mass, any cone sizes of more than 10-inches will inhibit subwoofer quickness. The cones flexibility also rises exponentially with size, introducing distortion. If you need to move more air, use more cones. Just how fast does a subwoofer need to react? Most any decent sub will respond to 200~300 Hz with high output and low distortion. A small cone will have less output, requiring greater excursion and more powerful amplifiers, or additional cones. A larger cone may be stiffer, will be more than "fast" enough, and requires less excursion for equivalent output and thus generally exhibits lower distortion. 3. Sealed boxes are superior to ported boxes. A mixed bag. A well-designed ported sub will have greater output than a sealed sub and thus lower distortion, for less amplifier power, than a sealed sub. Below port tune, a sealed sub will roll off slower, providing more output and potentially greater "room gain". A ported sub essentially "unloads" the cone below the port tune leading to cone flopping, and of course overdriving a ported sub can result in "chuffing" from the port. A right-sized ported sub, with sufficient port area/flow and proper roll-off, will provide greater output at lower distortion than a sealed sub. That said, I prefer sealed myself, and all my current subs are sealed though I have had ported in the past. 4. A high quality external amplifier optimized for current delivery is superior to any built-in plate amp on the market. I am not sure what he means by "current delivery". Assuming he means an amp that delivers gobs of current, and not a current-mode amplifier, then there is no reason this would be true except you may be able to buy a better amplifier than the plate amp in the sub. But most plate amps, whether class AB (like mine) or D (like most subs), are designed to deliver gobs of power into a very low load (many subs are wired as 1 to 4 ohm loads internally). So I don't have enough experience to get into a pissing contest on minutia, but I strongly suspect today's plate amps are more than adequate for the task. 5. Virtually ALL commercial, self-powered subwoofers use insufficient cabinet space (for WAF) and then try to compensate with more power. This tends to produce a resonant and peaky frequency response intended to provide maximum output for movie transients, but which is FAR too resonant for music use. The peaked frequency response of typical HT subs is an insurmountable obstacle for music. Uh, not really, though shipping size does limit the size of many of them. Long-throw drivers with proper EQ and control (my subs use a servo loop, similar to the DIY servo subs I built decades ago) provide adequate response. Measured data (databass etc.) does not show a lot of "peaky" response curves nor severe ringing; maybe he is looking at cheaper models? Some inexpensive subs I have seen do have issues, but the better ones do not. My subs do fine for me with music or movies. Most of the "boomy" subs I have heard are due to the room and over-boosted bass, not the sub itself. The servo does help with ringing, but a well-designed sub with a good amplifier won't ring significantly. That said, larger cabinets are generally more efficient, but WAF or not they get huge very quickly and I would not have space for say a 4' H x 3' W x 3' D cabinet my friend built for his 12" sub back in college. He used the same woofer I did for my servo design, which was basically an 18" cube, and at the end the measured performance was better for my design though his did indeed require less power. But mine fit in my room. 6. You can't buy a commercial cabinet that is sufficiently braced, and that doesn't sing along with the driver(s). I don't know how he defines "sufficiently braced" nor what level of cabinet vibration he considers "singing along with the drivers". All the better subs have thick, heavy cabinets that are more than adequately braced, and their custom designs (e.g. Funk, Salk) that take it even further. Again, this sounds like an issue with cheaper (less expensive) subs using thinner cabinets and such. But I have not done accelerometer measurements of sub cabinets lately. The cabinet I built, for a 12" servo-sub with 16 Hz -3 dB frequency, was no better than most cabinets I have seen today and that old DIY cabinet's vibrations were way below (orders of magnitude) the sub's output so you certainly would not hear it "singing along". 7. Typical HT subs begin rolling off far too soon. Even with the THX-standard 80 Hz. crossover the average sub has frequency response that drops like a stone even before you reach 80 Hz. Therefore the electronic crossover tends to leave a gap between the satellites and the subwoofer. Guess I'd have to see examples. I looked at a number of subs a few years ago and all had response well above the LFE limit (160 Hz), and the crossover rolls them off at from 12 to 48 dB/octave electrically before the acoustic roll-off. If you have satellites that do not reach to 100~120 Hz I can see where there might be a problem, but I am not up on where the average satellite speaker rolls off these days. I prefer to use larger speakers that have decent response an octave or more below the crossover to keep their distortion low and provide more flexibility in setting the crossover to counter room modes and such, plus a more seamless integration. |
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Post by Boomzilla on Aug 22, 2021 5:12:43 GMT -5
I'll try, you may believe it or not (Ripley). I am not a speaker designer (my career took a much different path though I dabble in audio design) and, while I'll stand behind my opinions, these are general observations from experience (listening, measuring, etc.), some design, and ancient mostly-forgotten grad courses in acoustics. Thank you so much for taking the time to write this, donh50 - it's most helpful. " 1. To be articulate, a sub woofer driver must be low mass. This precludes any heavy cones, huge voice coils, or stiff suspensions. In fact, the lighter and "floppier" the driver system, the less energy it will store and the quicker the driver can respond to low-level signals." - I do not know what "articulate" means to him but higher mass requires more driving force and better damping (lower amplifier output impedance). Lower mass is an admirable goal, but must be accompanied with increasing stiffness or distortion due to cone deflection will rise, eventually resulting in breakup modes (standing waves, peaks and valleys across the cone). More mass can be countered by a more powerful motor driving the cone. In contrast, the "floppier" the cone, th greater the distortion and at lower output (SPL) levels compared to a stiffer, heavier cone. The ideal would be infinitely stiff with zero mass, but for best performance one must trade mass, motor (amplifier) power, and distortion. Infinitely stiff + zero mass... I thought this Sony design with four voice coils per panel driver went far toward that goal: " 2. Because the sub woofer driver must be low mass, any cone sizes of more than 10-inches will inhibit subwoofer quickness. The cones flexibility also rises exponentially with size, introducing distortion. If you need to move more air, use more cones. - Just how fast does a subwoofer need to react? Most any decent sub will respond to 200~300 Hz with high output and low distortion. A small cone will have less output, requiring greater excursion and more powerful amplifiers, or additional cones. A larger cone may be stiffer, will be more than "fast" enough, and requires less excursion for equivalent output and thus generally exhibits lower distortion. "Any decent sub" is in the tiny minority these days if your definition is one that can achieve 300 Hz. with flat response. Here's a typical sub's response curve (this particular one is of a Klipsch R-15sw, although the R-12sw, sold at Costco and many other stores, is essentially identical): Note that the response is a typical steep hill shape and that the HF response is already diving at 100 Hz. The Klipsch is typical of almost ALL "consumer" subwoofers, that constitute the VAST majority of subs currently available. Your expectations of commercial subwoofers do not conform to what is available to consumers. " 3. Sealed boxes are superior to ported boxes." - A mixed bag. A well-designed ported sub will have greater output than a sealed sub and thus lower distortion, for less amplifier power, than a sealed sub. Below port tune, a sealed sub will roll off slower, providing more output and potentially greater "room gain". A ported sub essentially "unloads" the cone below the port tune leading to cone flopping, and of course overdriving a ported sub can result in "chuffing" from the port. A right-sized ported sub, with sufficient port area/flow and proper roll-off, will provide greater output at lower distortion than a sealed sub. That said, I prefer sealed myself, and all my current subs are sealed though I have had ported in the past. Although you're right in theory, in application, ports are generally used exactly as shown in the Klipsch frequency plot shown above. A clever DIY designer could use a port as you suggest, but very few manufacturers opt tor flat response. If you buy a commercial sub, you, in 99.9% of all cases, buy a HT design similar to the Klipsch. I know there must be at least some makers who don't design for maximum output and to hell with the ringing, but I don't know who those might be. " 4. A high quality external amplifier optimized for current delivery is superior to any built-in plate amp on the market." - I am not sure what he means by "current delivery". Assuming he means an amp that delivers gobs of current, and not a current-mode amplifier, then there is no reason this would be true except you may be able to buy a better amplifier than the plate amp in the sub. But most plate amps, whether class AB (like mine) or D (like most subs), are designed to deliver gobs of power into a very low load (many subs are wired as 1 to 4 ohm loads internally). So I don't have enough experience to get into a pissing contest on minutia, but I strongly suspect today's plate amps are more than adequate for the task. In theory, I think you're right. But in practice, I think my audio amigo has the right of it. Plate amps are made for low cost and to tolerate overdriving and abuse. Their linearity and distortion are generally NOT on the designers' radar as priorities. Full-range amplifiers, OTOH, are engineered for full bandwidth performance within their design parameters with minimized distortion and very good linearity. They cost orders of magnitude more than plate amplifiers, but audio amigo claims the difference is significant and audible. I find no reason to dispute him on this one. " 5. Virtually ALL commercial, self-powered subwoofers use insufficient cabinet space (for WAF) and then try to compensate with more power. This tends to produce a resonant and peaky frequency response intended to provide maximum output for movie transients, but which is FAR too resonant for music use. The peaked frequency response of typical HT subs is an insurmountable obstacle for music." - Uh, not really, though shipping size does limit the size of many of them. Long-throw drivers with proper EQ and control (my subs use a servo loop, similar to the DIY servo subs I built decades ago) provide adequate response. Measured data (databass etc.) does not show a lot of "peaky" response curves nor severe ringing; maybe he is looking at cheaper models? Some inexpensive subs I have seen do have issues, but the better ones do not. My subs do fine for me with music or movies. Most of the "boomy" subs I have heard are due to the room and over-boosted bass, not the sub itself. The servo does help with ringing, but a well-designed sub with a good amplifier won't ring significantly. That said, larger cabinets are generally more efficient, but WAF or not they get huge very quickly and I would not have space for say a 4' H x 3' W x 3' D cabinet my friend built for his 12" sub back in college. He used the same woofer I did for my servo design, which was basically an 18" cube, and at the end the measured performance was better for my design though his did indeed require less power. But mine fit in my room. I agree with you that cabinet volume may be a red herring. But it is undeniable that the design choices made by the vast majority of sub manufacturers minimize volume in order to provide maximum output - not flat output. " 6. You can't buy a commercial cabinet that is sufficiently braced, and that doesn't sing along with the driver(s)." - I don't know how he defines "sufficiently braced" nor what level of cabinet vibration he considers "singing along with the drivers". All the better subs have thick, heavy cabinets that are more than adequately braced, and their custom designs (e.g. Funk, Salk) that take it even further. Again, this sounds like an issue with cheaper (less expensive) subs using thinner cabinets and such. But I have not done accelerometer measurements of sub cabinets lately. The cabinet I built, for a 12" servo-sub with 16 Hz -3 dB frequency, was no better than most cabinets I have seen today and that old DIY cabinet's vibrations were way below (orders of magnitude) the sub's output so you certainly would not hear it "singing along". Maybe - but I refer (again) to the frequency response curve shown above. The entire system is designed to be HIGHLY resonant for maximum output, and the designers, considering any additional output to be "good" output, don't normally spend a penny beyond what they absolutely HAVE to to minimize box vibrations. The Klipsch subs dance over the floor with box vibrations when played loudly. They aren't atypical. " 7. Typical HT subs begin rolling off far too soon. Even with the THX-standard 80 Hz. crossover the average sub has frequency response that drops like a stone even before you reach 80 Hz. Therefore the electronic crossover tends to leave a gap between the satellites and the subwoofer." - Guess I'd have to see examples. I looked at a number of subs a few years ago and all had response well above the LFE limit (160 Hz), and the crossover rolls them off at from 12 to 48 dB/octave electrically before the acoustic roll-off. If you have satellites that do not reach to 100~120 Hz I can see where there might be a problem, but I am not up on where the average satellite speaker rolls off these days. I prefer to use larger speakers that have decent response an octave or more below the crossover to keep their distortion low and provide more flexibility in setting the crossover to counter room modes and such, plus a more seamless integration. I could waste pages with examples... MONOPRICE 9723:  PRESONUS T10:  SVS SB-2000:  HSU VTF-15H:  ETC. ETC. ETC. |
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Post by marcl on Aug 22, 2021 9:09:07 GMT -5
(deleted the long post with pictures to save a tree  ) Very interesting discussion. Thank you both boomzilla (and amigo), donh50. Two thoughts ... Seems to me the needs of LFE with high output and a 120Hz top limit (rolling off ~12db/octave I believe), and bass management for low frequencies which would benefit from flat response and extension up to 200-250Hz (thinking about small Atmos speakers) get all mixed up in the discussion. Two very different needs, trying to be accommodated by one sub design. And .... how about open baffle dipoles like the GR Research kits? p.s. my answer to the first issue is I send bass management to large fronts that only go to subs below 40Hz. LFE goes only to the subs. |
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Post by DYohn on Aug 22, 2021 9:56:19 GMT -5
Mr. DYohn has pointed out that regardless of the cone mass and suspension compliance, sufficient amperage through the voice coil will overcome all obstacles, and provide precise cone placement. I understand the sense of this, but somehow my audio amigo has obtained fantastic results with tiny voice coils. What I actually posted before was the math behind subwoofer motor operation showing that the mass and compliance of the system is moot when it comes to driver transient response (or the feeling of "speed" to the listener) and that the most meaningful electrical criteria is the inductance of the voice coil (not the amperage.) Lower inductance = better driver transient response. Now realize that this is only one of many system design criteria and may not be the most important one depending on system alignment and placement in room. But the bottom line remains that the woofer mass is not meaningful. Large or small voice coils are part of what determines a couple of things including power handling, sensitivity and inductance, but again the voice coil physicals size is not the key. The electrical characteristics of the coil are the key. I read through your post and it is full of so many misunderstandings and technical errors I am not going to reply point by point as that would take longer than I am willing to spend here. Suffice it to say that the enclosure is equally important to the driver in determining system performance, that any woofer can be used as a subwoofer (some performing better than others of course,) and any subwoofer system can be made to sound pretty good in a 2-channel setup if the installer has sufficient skill and tools to set it up properly. |
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Post by donh50 on Aug 22, 2021 10:17:23 GMT -5
I'll not get into a contest with Boomzilla; he has made his points well, though I disagree on principle, and don't feel the need to keep counterpointing everything about why the curves do or do not matter. I will say that a "humped" response does not necessarily imply peaking in the control theory sense that leads to underdamped behavior (ringing); it is usually a consequence of the LPF filter in the sub and intentional roll-off of the driver. IME/IMO. And a full-range amp is wasted on a sub, where loudness curves and user preferences dictate much higher power requirements more readily handled by a special-purpose amplifier. But it is because of the underdamped behavior of many subs that I originally designed a servo circuit for my first subwoofer. You can do it without a servo, and these days many subs do just fine. It is also one of the ironies of hearing that many folk prefer subs that have higher distortion and ringing as the higher-frequency distortion is more audible (see equal-loudness curves) so they may sound louder and "richer" or "fuller" than a cleaner (lower-distortion) sub. Subwoofers are, or should be, optimized for a relatively narrow frequency band. Having extended high-frequency response adds noise, distortion, etc. so I don't have a problem with a sub that is rolled off well before 300 Hz. But again, I much prefer main speakers with sufficient LF range that I do not need to use a sub at several hundred Hz -- that is a job for a midbass driver in my mind. At such high frequencies, a sub is localizable, thus defeating one of the primary goals of using a sub to counter room modes through proper placement unencumbered by directionality. That is, if you use a sub that high, you can tell (hear) where it is, and that means it has to be located where it does not muck up the stereo image. Most of the time that is not where it should be placed in the room for the smoothest bass response. When I have had that problem, I usually give up on room compensation and place the sub centered between the L/R speakers, or use a stereo pair of subs. I consider that sub-optimal (no pun intended) to being able to place the subs to counter room modes that are usually the major problem with deep bass. I chose my Atmos speakers in my current system to handle an 80 Hz crossover but of course that is not always an option. When I had surrounds with higher cut-off, I rolled them off, and threw away the deep bass for them (at that time, some years ago, little deep bass went to the anyway) rather than muck up the bass flatness I had achieved by routing the higher bass from the little speakers to my subs. LFE over the crossover set by bass management in my last few AVRs/processors (save one) was routed to the mains, so the subs did not have to deal with that. At 120 Hz and above the sound is localizable so I did not want it in the subs. Since LFE is a mono channel, sending it only to the subs makes a lot of sense, and I used a steeper rolloff whenever I could to prevent any localization of the LFE channel. Sometimes I had access to a steeper slope in the processor, and other times I used the line input instead of the LFE input to provide a 24+ dB/oct slope rather than the default 12 dB/octave of most AVRs. When I built my first sub back around 1980 or so I experimented with crossover slopes and found 12 dB/oct was not enough for me. That was all-analog days and I built an 18 dB/oct crossover. Had I known more (I was early in college then) I would have built a L-R 24 dB/oct design like a purchased and used for many years after that. Open baffle subs will act like point sources in the deep bass, same as any other sub, but as frequency increases the rear wave becomes more of an issue. They also require more attention to cone structure and amplifier performance IME since there is no cabinet to help control excursion. I have not looked at GR's designs; the best-sounding and measuring designs I have seen used a number of drivers to keep excursion (and distortion) limited (making them large) and often used a back-to-back pair of drivers so pressure waves were somewhat compensated. I have rarely had open-baffle subs, just did not really see the point and they generally have higher distortion and more limited frequency response, but when I did I rolled them off steeply. I did not, and do not, expect to change any minds, which is why I should have not commented in the first place. But this provides in my mind (feeble as it is) a good point/counterpoint for people to read opposing viewpoints. |
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Post by 405x5 on Aug 22, 2021 10:39:08 GMT -5
I'll not get into a contest with Boomzilla; he has made his points well, though I disagree on principle, and don't feel the need to keep counterpointing everything about why the curves do or do not matter. I will say that a "humped" response does not necessarily imply peaking in the control theory sense that leads to underdamped behavior (ringing); it is usually a consequence of the LPF filter in the sub and intentional roll-off of the driver. IME/IMO. And a full-range amp is wasted on a sub, where loudness curves and user preferences dictate much higher power requirements more readily handled by a special-purpose amplifier. But it is because of the underdamped behavior of many subs that I originally designed a servo circuit for my first subwoofer. You can do it without a servo, and these days many subs do just fine. It is also one of the ironies of hearing that many folk prefer subs that have higher distortion and ringing as the higher-frequency distortion is more audible (see equal-loudness curves) so they may sound louder and "richer" or "fuller" than a cleaner (lower-distortion) sub. Subwoofers are, or should be, optimized for a relatively narrow frequency band. Having extended high-frequency response adds noise, distortion, etc. so I don't have a problem with a sub that is rolled off well before 300 Hz. But again, I much prefer main speakers with sufficient LF range that I do not need to use a sub at several hundred Hz -- that is a job for a midbass driver in my mind. At such high frequencies, a sub is localizable, thus defeating one of the primary goals of using a sub to counter room modes through proper placement unencumbered by directionality. That is, if you use a sub that high, you can tell (hear) where it is, and that means it has to be located where it does not muck up the stereo image. Most of the time that is not where it should be placed in the room for the smoothest bass response. When I have had that problem, I usually give up on room compensation and place the sub centered between the L/R speakers, or use a stereo pair of subs. I consider that sub-optimal (no pun intended) to being able to place the subs to counter room modes that are usually the major problem with deep bass. I chose my Atmos speakers in my current system to handle an 80 Hz crossover but of course that is not always an option. When I had surrounds with higher cut-off, I rolled them off, and threw away the deep bass for them (at that time, some years ago, little deep bass went to the anyway) rather than muck up the bass flatness I had achieved by routing the higher bass from the little speakers to my subs. LFE over the crossover set by bass management in my last few AVRs/processors (save one) was routed to the mains, so the subs did not have to deal with that. At 120 Hz and above the sound is localizable so I did not want it in the subs. Since LFE is a mono channel, sending it only to the subs makes a lot of sense, and I used a steeper rolloff whenever I could to prevent any localization of the LFE channel. Sometimes I had access to a steeper slope in the processor, and other times I used the line input instead of the LFE input to provide a 24+ dB/oct slope rather than the default 12 dB/octave of most AVRs. When I built my first sub back around 1980 or so I experimented with crossover slopes and found 12 dB/oct was not enough for me. That was all-analog days and I built an 18 dB/oct crossover. Had I known more (I was early in college then) I would have built a L-R 24 dB/oct design like a purchased and used for many years after that. Open baffle subs will act like point sources in the deep bass, same as any other sub, but as frequency increases the rear wave becomes more of an issue. They also require more attention to cone structure and amplifier performance IME since there is no cabinet to help control excursion. I have not looked at GR's designs; the best-sounding and measuring designs I have seen used a number of drivers to keep excursion (and distortion) limited (making them large) and often used a back-to-back pair of drivers so pressure waves were somewhat compensated. I have rarely had open-baffle subs, just did not really see the point and they generally have higher distortion and more limited frequency response, but when I did I rolled them off steeply. I did not, and do not, expect to change any minds, which is why I should have not commented in the first place. But this provides in my mind (feeble as it is) a good point/counterpoint for people to read opposing viewpoints. …..what he said |
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Post by Boomzilla on Aug 22, 2021 11:24:30 GMT -5
Below is the frequency response curve of the JL Audio Fathom subwoofer - one that I consider well-designed and suitable for music: Compare this curve with the ones shown earlier. Now that said, I can't afford a Fathom (at least not until Covid is over and we can all go back to work). Anyone know of any other subs with similar curves for less $$$ ? Boom |
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Post by donh50 on Aug 22, 2021 12:08:51 GMT -5
This is the curve for my subs (Rythmik F12). Attachments:
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Post by novisnick on Aug 22, 2021 12:24:29 GMT -5
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Post by Deleted on Aug 22, 2021 12:28:00 GMT -5
Below is the frequency response curve of the JL Audio Fathom subwoofer - one that I consider well-designed and suitable for music: Compare this curve with the ones shown earlier. Now that said, I can't afford a Fathom (at least not until Covid is over and we can all go back to work). Anyone know of any other subs with similar curves for less $$$ ? Boom Perhaps some might share why they like "flat" subwoofers? I personally don't quite agree w/ the overall desirability of having flat frequency subwoofers. I take it the above graph is the frequency response of a sealed cabinet? I guess there's an extreme with everything but if I have a sub that has a bass peak somewhere in its operational range either from room interaction or more efficiency at port tuning frequency why might someone want to tune that out? - speaking of subwoofers. Recently I was engaged w/ another that couldn't stop assuming and kept trying to pass his nonsense off as "academia". The desired house curve I implemented was +10 Harman Research. The person couldn't wrap his mind around the fact that it is possible to achieve such curve not by "boosting" but rather by adding subwoofers to pretty flat mains. Likewise, the person assumed he knew what the main's frequency response looked like before any eq. In doing so he suggested there was no difference in "boosting or lowering to dips". Here's what I'm suggesting. The mains are shown in the below graph with no eq. They are pretty flat. To achieve +10 house curve two subs were added. I ended up also adding a +10 house curve to the mains by lowering the upper frequency response of the mains. In the end I had to trim back the gains on the subs by -12db to achieve a +12db house curve by Harman Research:  |
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Post by Deleted on Aug 22, 2021 12:33:32 GMT -5
1. To be articulate, a sub woofer driver must be low mass. This precludes any heavy cones, huge voice coils, or stiff suspensions. In fact, the lighter and "floppier" the driver system, the less energy it will store and the quicker the driver can respond to low-level signals. In fact, I believe this to be a fallacy. Mr. DYohn has pointed out that regardless of the cone mass and suspension compliance, sufficient amperage through the voice coil will overcome all obstacles, and provide precise cone placement. I understand the sense of this, but somehow my audio amigo has obtained fantastic results with tiny voice coils. 2. Because the sub woofer driver must be low mass, any cone sizes of more than 10-inches will inhibit subwoofer quickness. The cones flexibility also rises exponentially with size, introducing distortion. If you need to move more air, use more cones. See the response to claim one above for comments on cone mass, but if a cone can be made sufficiently rigid, I don't think that it would necessarily introduce distortion. Thoughts? Boom Newtonian Laws vs Einstein's theory of relativity. The whole Newtonian laws of motion of using low mass drivers are designed in most Tekton arrays. I do agree theoretically with DYohn but only suggest that lower efficient drivers demand much more power to control more mass which goes back to Newtonian law. In general I note larger subwoofers are less sensitive and have mega power watt handling capability. That combination [much more mass and bigger motors] generally requires more power handling. Newton's laws of motion: "Newton's laws of motion are three laws that describe the relationship between the motion of an object and the forces acting on it. The first law states that an object either remains at rest or continues to move at a constant velocity, unless it is acted upon by an external force. The second law states that the rate of change of momentum of an object is directly proportional to the force applied, or, for an object with constant mass, that the net force on an object is equal to the mass of that object multiplied by the acceleration. The third law states that when one object exerts a force on a second object, that second object exerts a force that is equal in magnitude and opposite in direction on the first object." My personal preference leans to multiple drivers equaling the same overall area of larger drivers. In such I love my 4-10s and also Tekton's MTM array. Each 4-10 has the same overall piston area of an 18" subwoofer. And each Tekton 15 driver MTM array has the same overall piston area of a 9" midrange with overall mass of only several grams and individually less than a gram of mass. Such arrays using smaller multiple drivers to equal larger driver area often exhibit lightening quick transient response and less bass hang in subwoofer frequency ranges. |
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Post by Boomzilla on Aug 22, 2021 13:18:02 GMT -5
Actually, the Emotive Reference 13 has a pretty flat curve:  |
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Post by Deleted on Aug 22, 2021 13:21:11 GMT -5
Actually, the Emotive Reference 13 has a pretty flat curve: Which all goes out the window once you place that subwoofer in an actual listening room.  A lot of guys don't bother measuring below 20hz because the measurement results are mainly room interaction at play. |
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Post by Boomzilla on Aug 22, 2021 13:24:56 GMT -5
Yeah, but I have the DSP box to repair room interactions!
It isn't quite violent enough with its correction to turn a HT sub into a more expensive one, but it does help some.
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Post by Deleted on Aug 22, 2021 13:40:57 GMT -5
Yeah, but I have the DSP box to repair room interactions! It isn't quite violent enough with its correction to turn a HT sub into a more expensive one, but it does help some. Of course room treatment isn't the same as room eq. I've decided to build an extension from my main wall to extend into the open space wrapping the sub on the right to match the left main wall's corner and the sub's loading. I'll tackle this "amphitheater" type wall project come winter when stuck indoors to escape the cold. No amount of DSP or eq can achieve bettering the open sided sub location as the corner loaded sub's frequency and gain. I prefer not to handicap the corner loaded sub by equaling that sub out to a lesser desirable location. Rather I'd prefer to equalize the locations by addressing the room design making the less than desirable location the same as the other more desirable one. |
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