output voltage/input sensitivity question for the experts

[deepstage]

I've had my XMC-1 up and running a couple of years now. For subwoofer duty I have the RCA pre-out going to a Dayton SPA-1000 amp and driving a 15" Dayton UM15-22 in their own 3 ft3 sealed enclosure.

It sounds great! I first had the sub out in front of me and moved it around a bit, but could always localize it and it just didn't satisfy me. Then I put it behind my listening position and it totally disappeared and sounds fantastic.

Music sounds great and for the most part movies too, except scenes with obscene ultra low output. The amp easily clips and I find myself turning the volume down a bit to avoid a meltdown. Now I'm not a fool and know the Dayton audio amps don't put out anywhere near their rated power. Fall is upon us and it's time to hibernate in the movie room, which is when I usually get the itch to upgrade so here goes my plan,,,,,,,,,,,,,,,and the info I'm seeking from you to make sure it's a sound choice I make based on available specs.

I'm keeping the 15" ultimax driver for now and plan on adding another sub or two. However, I want to throw some serious power at it, which it seems to be begging for.

Plan is to purchase a Cerwin Vega CV-5000 amp. I have read nothing but good about these amps. They are a beast with a monster transformer and the capacitance to match. For quite awhile I have been considering an Inuke 6000 or similar. However, I have come across some discussion that these amps just aren't up to the task of putting out the raw power, quality control and sound amps such as the Cerwin Vega, Crest, etc have.

So here's my question. I've read a bit about pro audio amps and home audio processors not matching up well as far as output voltage and input sensitivity. Can some educate me exactly how this works? Here are the specs taken directly from Cerwin Vega for the CV-5000.

Input Sensitivity (8 ohms 1.42V (+5.3dB) Input Impedance 20 kohms Balanced / 10t kohms Unbalanced

I see the 10t and believe it's a simple mistake (don't know where the t comes from )

Comparing two amps, all things being equal, would it mean that amp A with an input sensitivity of 0.775V have twice the gain compared to one with 1.42V?

I tried a Crown XLS1500 a couple years ago on the same sub in my upstairs room. Using my UMC-200, I had to turn the gain on the Crown all the way up and also slightly boost sub output of the UMC-200 to match the wimpy NHT MA-1A driving the same sub. Some people said it was a mismatch between output voltage on the pre-out and input sensitivity on the amp that caused the issue.

I want to make sure there isn't such a mismatch with the XMC-1 and CV-5000.

The CV-5000 does have a balanced input I could use also.

So please let's discuss this issue and how to match a sub amp with the outputs of the XMC-1. I want to use a solid amp with plenty of muscle and don't need any signal processing as that can all be handled via the XMC-1.

Sorry for the long winded post but I believe a lot of people run into this issue and could benefit from a good discussion regarding this, irregardless of what processor they use.

[KeithL]

If two amps have the same output power, and one requires half as much input to drive to full output as the other, then the one which requires the lower voltage is twice as sensitive.
However, note that sensitivity is simply a design parameter, and isn't especially important per-se.

There's usually a design trade-off, where increased sensitivity means more noise, so the designer picks the best compromise for a particular design.
In general, there's no need or reason to "match" sensitivity between components, except in a very broad way.
For example, if your preamp puts out a maximum of 2V, but your amp requires 20V to reach full output, then your preamp will not be able to drive that amp to full output.
But, if your preamp was capable of delivering 20V, and the amp only required 2V, you'd end up with the Volume control on the preamp barely off the bottom stop.
(And, that far down, the channels on the preamp might not track very well, and there might be issues with the noise floor.)

In general, there is a sort of informal standard for consumer equipment of around 1V or 2V.
Most consumer preamps and pre/pros can put out at least a bit more than that, and most amps can be driven to full power with something around there.
If you were to buy a pro amp that REQUIRED 10V to reach full output, then some consumer processors may not be able to drive it satisfactorily.
However, you are most unlikely to find an amp with that sort of requirements, and most current equipment works pretty well together.
(Back in the old days, when a lot of equipment was somewhat noisy, noise could be minimized by matching things more closely - but that really isn't important these days.)

Clipping can occur in different places....
If your preamp was unable to deliver enough voltage to drive your power amp to full power, then the output of the preamp could clip.
However, in real life, when things "run out of power", it's almost always the power amp that's clipping.

Sept 10, 2017 10:47:44 GMT -5 deepstage said:

I've had my XMC-1 up and running a couple of years now. For subwoofer duty I have the RCA pre-out going to a Dayton SPA-1000 amp and driving a 15" Dayton UM15-22 in their own 3 ft3 sealed enclosure.

It sounds great! I first had the sub out in front of me and moved it around a bit, but could always localize it and it just didn't satisfy me. Then I put it behind my listening position and it totally disappeared and sounds fantastic.

Music sounds great and for the most part movies too, except scenes with obscene ultra low output. The amp easily clips and I find myself turning the volume down a bit to avoid a meltdown. Now I'm not a fool and know the Dayton audio amps don't put out anywhere near their rated power. Fall is upon us and it's time to hibernate in the movie room, which is when I usually get the itch to upgrade so here goes my plan,,,,,,,,,,,,,,,and the info I'm seeking from you to make sure it's a sound choice I make based on available specs.

I'm keeping the 15" ultimax driver for now and plan on adding another sub or two. However, I want to throw some serious power at it, which it seems to be begging for.

Plan is to purchase a Cerwin Vega CV-5000 amp. I have read nothing but good about these amps. They are a beast with a monster transformer and the capacitance to match. For quite awhile I have been considering an Inuke 6000 or similar. However, I have come across some discussion that these amps just aren't up to the task of putting out the raw power, quality control and sound amps such as the Cerwin Vega, Crest, etc have.

So here's my question. I've read a bit about pro audio amps and home audio processors not matching up well as far as output voltage and input sensitivity. Can some educate me exactly how this works? Here are the specs taken directly from Cerwin Vega for the CV-5000.

Input Sensitivity (8 ohms 1.42V (+5.3dB) Input Impedance 20 kohms Balanced / 10t kohms Unbalanced

I see the 10t and believe it's a simple mistake (don't know where the t comes from )

Comparing two amps, all things being equal, would it mean that amp A with an input sensitivity of 0.775V have twice the gain compared to one with 1.42V?

I tried a Crown XLS1500 a couple years ago on the same sub in my upstairs room. Using my UMC-200, I had to turn the gain on the Crown all the way up and also slightly boost sub output of the UMC-200 to match the wimpy NHT MA-1A driving the same sub. Some people said it was a mismatch between output voltage on the pre-out and input sensitivity on the amp that caused the issue.

I want to make sure there isn't such a mismatch with the XMC-1 and CV-5000.

The CV-5000 does have a balanced input I could use also.

So please let's discuss this issue and how to match a sub amp with the outputs of the XMC-1. I want to use a solid amp with plenty of muscle and don't need any signal processing as that can all be handled via the XMC-1.

Sorry for the long winded post but I believe a lot of people run into this issue and could benefit from a good discussion regarding this, irregardless of what processor they use.

[deepstage]

Thanks for the response Keith. Does Emotiva publish voltage of the preamp outputs? I have a UMC200 and XMC-1 and would like to know those specs.

I was contemplating purchasing a new sub amp last year and either asked the question or read a post where someone else did, whether the XPA-1 (if I could find one) would be a good choice for a sub amp. I recall someone on the forum said it would be a poor choice as there are so many other options out there much cheaper with more power. However, most of the options I see brought up time and time again seem like mass produced cheap junk. 3-5 thousand watt class D amps that weight 8 lbs?? I'd rather spend good money on something that would have the legitimate muscle, along with a 12v switched input than a few hundred dollars on something that feels cheap and I have little confidence in. This is why I am leaning toward trying the CV-5000. I have read a few places that they do indeed put out their claimed power or very close to it. This would give me plenty of power and room to grow.

I just can't help but think an original XPA-1 backed up by the EQ capability of the XMC-1 would make a great, dependable sub amp. After all, it probably legitimately has double the power capability of my ho hum Dayton (sub) amp.

[405x5]

Velodyne is the answer for subwoofers 🔊 and the power to drive them.
And.....a superior match to the XMC over any product from Dayton IMHO....

Bill

velodyneacoustics.com

[deepstage]

I'm sorry, but what relevance does this have to what I've posted? I'm asking about matching amps to preamps. Not looking to buy any particular subwoofer. Some of us are DIY types and love the reward of building things ourselves.

[405x5]

Sept 12, 2017 18:38:49 GMT -5 deepstage said:

I'm sorry, but what relevance does this have to what I've posted? I'm asking about matching amps to preamps. Not looking to buy any particular subwoofer. Some of us are DIY types and love the reward of building things ourselves.

"The amp easily clips and I find myself turning the volume down a bit to avoid a meltdown. Now I'm not a fool and know the Dayton audio amps don't put out anywhere near their rated power"

........your words
Appears (from what you have posted) that you are lacking power to accomplish your listening level goals. This has more to do with your difficulty from what I've read, than the questions you have asked, looking for answers.

Bill

[deepstage]

Again, the relevance?

Yes I admitted the Dayton amp is underpowered. I'm interested in buying a new amp which will meet my goals and want to further my understanding of matching an amplifier to the XMC-1. I believe Keith did a good job of steering me in the right direction. I also did done searching and read a few articles on input sensitivity, output voltage and gain structure.

Sure one of Velodynes high end subwoofers may sound better than what I have. Keep in mind I'm using a $399 amp, a $199 driver and an enclosure that's properly stuffed and braced, which cost me material to make. So fir around $700 I have a subwoofer that, through 95% of what I listen to, sounds as good as anything I've heard in some very nice high end theater setups. Also take into account I use a calibrated mic along with multiple programs to measure its output and room response.

I've decided to order the Cerwin Vega amp. I'm not looking for it to make any difference in my system other than to give me the extra power to fill the void during those intense, high demand moments in movies. I'm sure it will loaf along on one channel, allowing me to add another sub later when I have time to build one.

Then again, I could just go buy a couple 3-5K Velodyne subs for possibly no improvement or for all you know, a downgrade.

I could name 10, 20 or more other subwoofers that would claim they are as good or superior to anything Velodyne makes and really, I think we all know so much of this is, at a certain price and quality point, subjective.

No offense Bill, but I'm glad so many others that read this post and didn't have anything relevant to add, refrained from suggesting I go spend thousands on a subwoofer from XYZ. It just isn't relevant to what I was trying to learn.

[405x5]

How many read this ?!

[405x5]

🤠

[rbk123]

Can you hook up a normal amp to your Ultimax and see how that works? I ask because it seems odd that, even over-rated, 1000W from the Dayton isn't enough. In one setup I am using a UPA-200 driving 2 different subs, both sealed, and when I crank I can't get any clipping; my ears give out from the overall setup before any of the amps. Seems like something else is wrong - what is the rest of your system? If a multi-channel Emo amp - can you borrow one of the channels and drive the Ultimax to see how that performs?

Sorry - no help on the sensitivity question, but personally I prefer to use regular amps to drive my sealed subs vs. plate amps. In another setup I have XPA-100's driving them.

[KeithL]

For a pre/pro, the "preamp output" is simply the main output - so those specs apply.
The XMC-1 can put out 4 or 5 V, which is plenty to drive any normal amp out there.
I couldn't find the spec on the UMC-200 offhand, but it puts out plenty to drive any normal consumer amp to full power.
(There isn't really a hard standard, but virtually all consumer audio equipment can be driven to full power with around 2V, and virtually all preamps will all put out more than that.)

The main reason people "cut corners" on subwoofer amps is simply that the requirements are different than for regular amps.
Most subs want/need a lot of power, but only at low frequencies...
So a subwoofer amp needs to be able to deliver a lot of power from, maybe, 10 Hz to 500 Hz, at low distortion..... but whether it's clean or not at 10 kHz really doesn't matter.
This aligned well with early Class D amps, which were very efficient, and very powerful, and worked very well over that range of frequencies, but didn't necessarily sound very good over the full audio range.

In short, any good full range audio amp will work well for a sub...
But many sub amps wouldn't sound very good if you used them on a main channel (and that's not a problem - because you won't be asking them to do so).

The other side of the coin is that SOME subs are difficult to drive....
Some may operate at very low impedances (like 2 Ohms) and others may drop to a very low impedance at certain frequencies.
And, because they usually use heavy drivers with big magnets, subwoofer drivers tend to generate a lot of back EMF.
Both of these situations mean that some subs may be especially difficult for a "normal" amplifier to drive.
And, of course, a "subwoofer amplifier" should have been designed specifically with this in mind.

The short answer to your comment is that, yes, an XPA-1 will usually run a subwoofer very well...
(However, some passive subwoofers are really difficult to drive, and will make it work really hard, and some may actually be outside its capabilities.
For example, we do NOT recommend that you use your XPA-1 to drive a 2 Ohm load, continuously, at high power, for extended periods of time.)
But a purpose-designed subwoofer amp may give you more power, for a lot less money, and may sound just as good in that limited application.
(And some of them are designed to run into a 2 Ohm, or even a 1 Ohm load, continuously.)

Subwoofer amps have sort of become an uncommon subject - because most modern home subwoofers (other than DIY ones) come with an amp built in.
(And the amp has been chosen to work optimally with the driver and cabinet they used.)

Sept 11, 2017 19:28:00 GMT -5 deepstage said:

Thanks for the response Keith. Does Emotiva publish voltage of the preamp outputs? I have a UMC200 and XMC-1 and would like to know those specs.

I was contemplating purchasing a new sub amp last year and either asked the question or read a post where someone else did, whether the XPA-1 (if I could find one) would be a good choice for a sub amp. I recall someone on the forum said it would be a poor choice as there are so many other options out there much cheaper with more power. However, most of the options I see brought up time and time again seem like mass produced cheap junk. 3-5 thousand watt class D amps that weight 8 lbs?? I'd rather spend good money on something that would have the legitimate muscle, along with a 12v switched input than a few hundred dollars on something that feels cheap and I have little confidence in. This is why I am leaning toward trying the CV-5000. I have read a few places that they do indeed put out their claimed power or very close to it. This would give me plenty of power and room to grow.

I just can't help but think an original XPA-1 backed up by the EQ capability of the XMC-1 would make a great, dependable sub amp. After all, it probably legitimately has double the power capability of my ho hum Dayton (sub) amp.

[KeithL]

In general design terms, output level and input sensitivity are both simply design choices.
It literally costs EXACTLY the same to design a preamp that can put out 1V as one that can put out 3V...
Likewise, it costs the same to design your power amp to have a full output from a 0.5V input as from a 5V input...
(There are certain tradeoffs - but they are minimal over this narrow range. The old days of tricky trade-offs are mostly gone. )
As long as your source can deliver MORE than your amp requires, then they'll work well together.

With commercial consumer equipment there are sort of de-facto standards that everyone stays near.....
But, if you're designing your own DIY equipment, and you want it to work with the widest variety of commercial equipment, there are slightly different choices that make sense....
For example, if you're designing a preamp or active crossover, design for an output level of up to about 5V.
(Most equipment will be fine with 1V to 2V, but that way you're covered if you encounter the odd piece of equipment that needs more.)
And, if you're designing a subwoofer, which has a Volume control on its amp, you probably want it to be able to reach full output with 0.5V or so - or even less - when the control is all the way up.
(That way it will work with even the occasional low-output preamp, and probably even with a passive volume control.)
You might even want to include a "gain" switch to choose between "normal" and "high" gain.

Sept 12, 2017 18:38:49 GMT -5 deepstage said:

I'm sorry, but what relevance does this have to what I've posted? I'm asking about matching amps to preamps. Not looking to buy any particular subwoofer. Some of us are DIY types and love the reward of building things ourselves.

[405x5]

Sept 13, 2017 0:57:02 GMT -5 deepstage said:

 "I could just go buy a couple 3-5K Velodyne subs for possibly no improvement or for all you know, a downgrade. "

Unlikely.......My Velodyne HGS 18 in use with the XMC

Bill

[deepstage]

Great info Keith, I really appreciate your time and some of the info I have dug up confirms exactly what you have said.

RBK, I have tried hooking up my old NHT sub amp which is rated at 80 watts @8ohms. Running at 4 ohms I'm sure it's putting out quite a bit more, but nothing impressive for sure. I have had this amp powering a JL audio sub in a bandpass enclosure for almost 20 years. An absolute insane level of efficiency in the bandpass region. This amp couldn't drive the Ultimax sub very hard and it did clip, but that's expected. I also did power it off one channel of my UPA-7 and obviously just didn't have the power either, though it did sound good. I never drove it hard enough to test for clipping as I didn't feel lucky enough LOL!

I sent one Dayton amp back after it failed. The replacement had issues that went away mysteriously and has worked great for a couple years. I may have overstated that it easily clips. It's more that it does so in the very lowest octave during those scenes when a space ship is rumbling, an airplane is crashing or generally the world is going to hell. It digs deep and sounds great until I have to back it off. I've read where people have measured the output of various amps and I believe the SA1000 was shown to hit 490 or so. I have no reason to doubt that. I should have the CV-5000 next week so I'll see how it works. I'm expecting to be frightened.

Bill I appreciate that you love to show off your Velodyne and I'm sure it is the cats meow, but again, it's not going to happen and the inclusion of it in this discussion is really just pointless.

[405x5]

Sept 13, 2017 8:05:58 GMT -5 rbk123 said:

Can you hook up a normal amp to your Ultimax and see how that works? I ask because it seems odd that, even over-rated, 1000W from the Dayton isn't enough. In one setup I am using a UPA-200 driving 2 different subs, both sealed, and when I crank I can't get any clipping; my ears give out from the overall setup before any of the amps. Seems like something else is wrong - what is the rest of your system? If a multi-channel Emo amp - can you borrow one of the channels and drive the Ultimax to see how that performs?

Sorry - no help on the sensitivity question, but personally I prefer to use regular amps to drive my sealed subs vs. plate amps. In another setup I have XPA-100's driving them.

Could possibly be a phase issue....
If the subwoofer is out of phase with the main speakers, more power would be required to achieve the same level of bass output with greater distortion likely.


Bill

[rbk123]

Sept 13, 2017 18:46:16 GMT -5 deepstage said:

RBK, I have tried hooking up my old NHT sub amp which is rated at 80 watts @8ohms. Running at 4 ohms I'm sure it's putting out quite a bit more, but nothing impressive for sure. I have had this amp powering a JL audio sub in a bandpass enclosure for almost 20 years. An absolute insane level of efficiency in the bandpass region. This amp couldn't drive the Ultimax sub very hard and it did clip, but that's expected. I also did power it off one channel of my UPA-7 and obviously just didn't have the power either, though it did sound good. I never drove it hard enough to test for clipping as I didn't feel lucky enough LOL!

That certainly is odd; one of my subs on the UPA is the Titanic MKIII which the Ultimax eventually replaced, and the other is a DVC 15" driver also from PE. I wonder if you're just reaching the max excursion of that driver and need to build another 1 (or 3) so it isn't working as hard to reach the SPL's you like? Or it could be out of phase like 405x mentioned; that's possible. Will be curious to hear how it turns out, so keep us posted.

[deepstage]

I'll play around with it a bit and see if I get different results. I know I've tried playing with the phase and everything I could think of. I'm still getting the CV amp so it will be interesting to see how it fairs with that.

The room I have it in is approximately 350ft2 with 7 foot ceilings so it's not a huge room. It's not like it requires a wall of subs. I'm thinking of building another sub using the peerless XXLS 835017 driver. That's just more for fun. It may end up in the movie room or upstairs.