Bad setup, bad room, or sensitive ears? Subs are just never from the "same cloth"!

[caesar]

Every time I have heard subs connected to a speaker system, I have been able to hear a lot of musical information that I never expected to hear. I do know there is a lot of potential of enhancing the the system by possibly adding sub-woofers. Unfortunately, however, I have also been hearing the sub(s) as completely separate drivers from the rest of the speaker.

And I am not the only one with this problem. After giving a GLOWING review to the Martin Logan CLX in TAS, Jonathan Valin was supposed to slap on a couple of subs to his system and update the review. But this never happened. I am guessing he didn't want to put a black mark on Martin Logan, so he never wrote the "bad" review.

To me, and I am guessing to Valin, the music is just not from the "same cloth". On the other hand, many people are happy with subs. Can anyone shed some light on this?

(Please use common language and explain the terms you are using like you are talking to a 10 year old. I took physics and advanced calculus as a freshman in college, and although I did very well in the classes, it has been a long, long time - and I forgot everything!!)

[RBFC]

The quality of a subwoofer is only one part of the equation. The setup is probably the most important portion of the "integration" scheme. I brought up the subject here:

http://www.whatsbestforum.com/showth...-Relationships

and the ensuing discussion quickly showed how complex seamless integration of a sub (or multiples) can be. Most folks don't take the time and effort to accomplish good integration IMO.

Lee

[DaveyF]

Caesar, I think that the discontinuity that you hear is primarily due to the basic difference between the speed of the drivers. Most stats and many dynamic drivers have a fast rise/settle time. Unfortunately, I believe most subs which are able to move larger amounts of air ( which IMO is the primary aspect of being able to reproduce very low notes) are able to do so mainly by using larger drivers. The larger the driver, generally the slower the rise/settle time.Let's use a vehicle analogy, a boxy truck can reach 60mph in say 15 seconds, while a small car can reach the same speed in say 8 seconds. It takes more power to get the truck to 60mph than the small car....due to mass, air resistance, etc. Once at 60mph, both can keep that speed with little power required, however, then you want to slow the truck and the car down to zero mph. Takes a lot more energy and time to slow the truck.....the truck is like the subwoofer, the car like the stat or smaller dynamic speaker.
The trick is to match the sub to the main speakers, which gets more difficult as the mains have a quicker rise/settle time. Therefore, i believe that the secret lies in trying to match the mains to a sub that shares as close as possible in the type/size of driver as the mains. Many times this will require loosing the very bottom end due to the restriction of the sub driver size that can be incorporated.-----or something like that

[terryj]

nah davey, does not work like that. Not to say it is easy to integrate subs properly, but them being slow has nowt to do with it.

They do not need to be fast, a sub signal is sloooow man. If you get a chance, just listen to a sub on it's own. A more horrible, amusical gargle you will never hear.

Get the idea how long it takes for us to even recognise a 20 hz signal as 20 hz....then compare to how long it takes to recognise a 20 khz signal (I know, I know, it's a thought experiment!).

So, a 21 inch woofer is PLENTY fast to reproduce a 50 hz signal.

[DaveyF]

Sorry terry, BUT your analogy is wrong. Otherwise a 21" woofer could be used for midrange and a 18" woofer for high's ...
Speed of the driver response is THE main reason why it is so difficult to integrate subs and mains.
Don't believe me, then take your 18" sub and see how easy it is to integrate that with a pair of Quads or other ultra fast drivers....I'm thinking ribbons, etc. Not saying it cannot be done, however, a fast 8" or smaller driver in a sub is a lot easier to integrate.
Assuming of course that the x-over is up to the job..

[terryj]

Sorry terry, BUT your analogy is wrong. Otherwise a 21" woofer could be used for midrange and a 18" woofer for high's ...
Speed of the driver response is THE main reason why it is so difficult to integrate subs and mains.
Don't believe me, then take your 18" sub and see how easy it is to integrate that with a pair of Quads or other ultra fast drivers....I'm thinking ribbons, etc. Not saying it cannot be done, however, a fast 8" or smaller driver in a sub is a lot easier to integrate.
Assuming of course that the x-over is up to the job..

No davey, I agree that an 18 would not be the best job for a tweeter, whatever gave you the idea I was suggesting that? Even in that case there are many other factors (other than """speed"""-or 'fast and slow bass') which work against using it in that role.

Sorry, 'speed' is a misused and completely misunderstood audiophile jargon word. Not quite as bad as synergy and prat I grant you.

Per your argument (speed), then flipping your point on it's head a tweeter (it IS fast enough) should be able to work as a sub.

Clearly an inappropriate point you are trying to make.

Have a look at the waveform of a bass signal. There is NO need for 'speed'. There is, however, plenty of need for displacement, which is exactly what a 21 will give.

Have you ever heard a sub on it's own as I suggested for a means of finding the answer to this??

If so, can you describe what you heard?? Would any part of that description be 'speed'??

Take a look at the measurement series in a recent thread here, JA. Look at the step impulses etc of the measurements. Compare the step of the tweeter to the mid (I assume a mid has enough 'speed' to do the job asked of it?). It will look very much spread out compared to the tweeter. Now extrapolate that to a sub, it is very spread out in time, but that is a function of the signal sent to it, not anything to do with 'speed'.

You are completely free to hold onto your beliefs, and disagree with me. I don't have the slightest problem with that. But in a thread asking for 'reasons why' I feel that my point definitely needs to be made.

Let's assume that a quad IS 'faster' than a cone driver (you mean stats etc??). Ok cool. Let's assume they are ten times as fast. That is all well and good, but a driver only needs to be as fast as the signal requires. I also note the OP did not restrict this discussion to stats or ribbons, he asked a general question aimed at sub integration, presumably including normal cone systems.

If you prefer, how about I say 'look to other far far more important factors than speed first'. Hopefully you can agree with that.

Else, there would be no successful sub integrations anywhere...I doubt you would agree with such a broad statement.

[DaveyF]

No davey, I agree that an 18 would not be the best job for a tweeter, whatever gave you the idea I was suggesting that? Even in that case there are many other factors (other than """speed"""-or 'fast and slow bass') which work against using it in that role.

Sorry, 'speed' is a misused and completely misunderstood audiophile jargon word. Not quite as bad as synergy and prat I grant you.

Per your argument (speed), then flipping your point on it's head a tweeter (it IS fast enough) should be able to work as a sub.

Clearly an inappropriate point you are trying to make.

Have a look at the waveform of a bass signal. There is NO need for 'speed'. There is, however, plenty of need for displacement, which is exactly what a 21 will give.

Have you ever heard a sub on it's own as I suggested for a means of finding the answer to this??

If so, can you describe what you heard?? Would any part of that description be 'speed'??

Take a look at the measurement series in a recent thread here, JA. Look at the step impulses etc of the measurements. Compare the step of the tweeter to the mid (I assume a mid has enough 'speed' to do the job asked of it?). It will look very much spread out compared to the tweeter. Now extrapolate that to a sub, it is very spread out in time, but that is a function of the signal sent to it, not anything to do with 'speed'.

You are completely free to hold onto your beliefs, and disagree with me. I don't have the slightest problem with that. But in a thread asking for 'reasons why' I feel that my point definitely needs to be made.

Let's assume that a quad IS 'faster' than a cone driver (you mean stats etc??). Ok cool. Let's assume they are ten times as fast. That is all well and good, but a driver only needs to be as fast as the signal requires. I also note the OP did not restrict this discussion to stats or ribbons, he asked a general question aimed at sub integration, presumably including normal cone systems.

If you prefer, how about I say 'look to other far far more important factors than speed first'. Hopefully you can agree with that.

Else, there would be no successful sub integrations anywhere...I doubt you would agree with such a broad statement.

Terry, I think we may be speaking of the same thing. I am talking about the driver's ability to quickly start and stop moving. The larger the driver, the more momentum that is in play and the more ability to move air. The smaller the driver, the less momentum and therefore a superior ability to start and stop moving ( but less ability to move air). I think if you re-read my prior posts, you will see what I am saying......Hopefully

[terryj]

Terry, I think we may be speaking of the same thing. I am talking about the driver's ability to quickly start and stop moving. The larger the driver, the more momentum that is in play and the more ability to move air. The smaller the driver, the less momentum and therefore a superior ability to start and stop moving ( but less ability to move air). I think if you re-read my prior posts, you will see what I am saying......Hopefully

cool davey, and yes as re-stated now there is nothing to disagree with.

It IS true that a sub could not play 20 khz, and I'd hazard an awful lot of that is due to it's mass etc.

After that I suspect it gets a little more murky..eg if from that someone were to say a woofer cannot accelerate as fast as a tweeter, well I think we'd be getting into murky territory...i suspect it could.

Anyway, keeping your point in mind we come back to the required ability of the driver to start and stop as asked. A sub is completely and totally capable of doing that at the frequencies in question.

Back then to the factors which DO make an impact on how to successfully integrate a sub into a system.

(BTW, if sometime you do get a chance to do the experiment outlined above-listen to a sub on it's own-do so, as it is quite illuminating)

[DonH50]

IME, problems I have heard with subs rarely have to do with the speed of the attack, let alone sub "speed" (not sure exactly what that means though the term is thrown about a lot). What I have observed and/or measured:

1. High distortion and ringing/slow decay that muddies the response. I have measured 10% or more THD in subs; at 20 Hz, honestly, I doubt it matters; at 100 Hz, it does. At least to me. As for the decay, I have found the 50 - 150 Hz range seems muddy if the sub is still "hanging on" after the musical signal has moved on. One reason I prefer servos.

2. Subs crossed over too high, or with too slow a roll-off so they have too much output too high in frequency. Too many folk don't seem to realize that the sub does not magically and instantaneously cut off at 0.001 Hz over the crossover frequency.

3. Subs crossed over too low, so the mains are working too hard and outside their peak performance range. If the crossover is not properly set, frequency and phase, there will be a peak or null at the crossover point.

4. Poor phase matching with the mains. If the sub is not in phase with the mains at the crossover point all kinds of bad things can happen. An octave above, and the sub usually dominates so phase is not as critical; ditto an octave above, where it's mostly the mains. Right at the crossover, you want the sound to be seamless coming from the mains and sub.

5. Adding a sub to boost the low end often brings out room modes you didn't know you had. This can cause boomy bass and all the usual issues related to room acoustics.

FWIWFM - Don

EDIT: Just noticed this was Tom's place; my apologies for spouting off! I get caught all too often by going to "What's New" and not noticing when treading in an expert's forum. Senility, I suppose.

[Ron Party]

WRT *speed*, start here, and read on for a couple of pages as our resident expert Mark Seaton joins in the discussion.