Placing speakers on top of subwoofers

[Ron Texas]

Why add a sub to a speaker with 2 18" woofers?

 

[andreasmaaan]

Why add a sub to a speaker with 2 18" woofers?

Not sure why this Genelec dude in the purple shirt does it, but one reason could be to position them in optimal places around the room for more even bass response.

 

[svart-hvitt]

Why add a sub to a speaker with 2 18" woofers?

The 1236 needs a base (sic!) to have its acoustic axis in ear height

On a serious note; extra membrane area would probably lower distortion. Membrane area matters.

Once, I visited a guy who has eight 24 inch woofers. Adding membrane area works even if producers of girlie speakers tell you another story. For some reason, science hasn’t been able - as far as I know - to find a one-stop measure that tells you if the sound is «big» or «small». In the meantime, one should assume that size matters.

 

[svart-hvitt]

My gut feeling says that the Behemoths outperform the very most of the "high end" speakers, including the girlie speakers you mentioned. I would have loved to listened to them.

Yeah, I think this system would work quite well, and it’s plug and play. Just set it up, spend 5 minutes to calibrate through DSP and turn up the volume.

 

[stunta]

I don't see it as a problem at all. In any event, what's the difference between a genuine large full-range loudspeaker and a small loudspeaker on top of a sub?

I don't know but why I am not getting the same dynamics out of my small speaker + sub (I only have one sub ATM) as I get from full range loud speakers? For instance, the Revel F208 has 8" woofers. My Sub has one 10" woofer. Will adding a second sub help?

 

[RayDunzl]

I don't know but why I am not getting the same dynamics out of my small speaker + sub (I only have one sub ATM) as I get from full range loud speakers?

Loudness?

My little JBL LSR 308 won't play (cleanly) with the same apparent loudness as my big speakers.

Can you measure?

I think I see compression/limiting beginning to set in on the woofer at higher levels, above 95dB. I didn't press any higher:

 

[andreasmaaan]

I don't know but why I am not getting the same dynamics out of my small speaker + sub (I only have one sub ATM) as I get from full range loud speakers? For instance, the Revel F208 has 8" woofers. My Sub has one 10" woofer. Will adding a second sub help?

Which speakers and sub do you have, what's the crossover point and slope, and how are you doing the crossover?

 

[sergeauckland]

I don't know but why I am not getting the same dynamics out of my small speaker + sub (I only have one sub ATM) as I get from full range loud speakers? For instance, the Revel F208 has 8" woofers. My Sub has one 10" woofer. Will adding a second sub help?

Which speakers and sub do you have, what's the crossover point and slope, and how are you doing the crossover?

You'll only get an increase in dynamics if the sub has a filter to remove the LF from the main pair. That way, the sub handles all the extreme LF, and the mains only have to handle what they're capable of, say above 80-100Hz. Getting a second sub won't change that.

S

 

[svart-hvitt]

You'll only get an increase in dynamics if the sub has a filter to remove the LF from the main pair. That way, the sub handles all the extreme LF, and the mains only have to handle what they're capable of, say above 80-100Hz. Getting a second sub won't change that.

S

But you should still get the evening out of the frequency curve, agree?

 

[stunta]

ATC SCM19 (v1) speakers and REL Storm III sub. Right now, I am crossing over (in the preamp - Classe CP800) at 80 Hz with a 6db slope.

I will get some measurements this weekend. @RayDunzl - I am looking at your graph and I am not understanding how you are interpreting compression from it. Is it the slightly steeper dip close to 20k at 95db?

My comfort level is 85db.

 

[stunta]

SCM 19 newer version frequency response. Should be similar to what I have.

EDIT: source: http://www.avmentor.net/reviews/2016/atc_scm19_2.shtml

 

[andreasmaaan]

ATC SCM19 (v1) speakers and REL Storm III sub. Right now, I am crossing over (in the preamp - Classe CP800) at 80 Hz with a 6db slope.

I will get some measurements this weekend. @RayDunzl - I am looking at your graph and I am not understanding how you are interpreting compression from it. Is it the slightly steeper dip close to 20k at 95db?

My comfort level is 85db.

Ok, I reckon your problem is likely to be that 6dB crossover slope, which at 80Hz is still asking a huge amount from the ATCs.

Try a higher order filter, 12dB or 24dB, and/or a higher crossover frequency (if your sub is not too far from the speakers and is more or less equidistant from you).

In @RayDunzl's graph, the point of interest is mostly at around 40-120Hz. You can see there that at 95dB something isn't coping.

 

[RayDunzl]

Is it the slightly steeper dip close to 20k at 95db?

No.

The measurements were 5dB increments.

The compression I see is in the bass.

Example - 70Hz

62 67 72 77 82 87 92dB and then (compression) 93 (97dB expected)

( I don't hear at the high end (never have), so anything there won't affect me)

My comfort level is 85db.

Mine is about the same level - for loud listening, averaged over time.

But, that implies 100~105dB dynamic peaks, some of which might be reduced by several dB if I extrapolate from the above measurements.

 

[Ron Texas]

I don't know but why I am not getting the same dynamics out of my small speaker + sub (I only have one sub ATM) as I get from full range loud speakers? For instance, the Revel F208 has 8" woofers. My Sub has one 10" woofer. Will adding a second sub help?

I think the crossover frequency has a lot to do with it. A sub comes in in the 50 to 80hz range. Floor standers cross over those dual (or triple) woofers around 400hz. The LF driver in the stand mounts is the limiting factor because it is covering too much of the audio range.

 

[sergeauckland]

But you should still get the evening out of the frequency curve, agree?

Yes, the frequency response will extend downwards more evenly, but without a crossover from sub to mains, the mains will still be trying to reproduce LF they can't manage, so distortion will be higher and power handling more limited.

As was also mentioned above, although 6dB/octave is better than nothing, 24dB/octave is far more effective.
If the sub doesn't have a filtered low level output to the main amplifier, a two-way active crossover can be used here provided the crossover point can be set low enough, to around 100Hz.

When my son went to university, I built him a sub with such a crossover, and it made some cheap small Mission loudspeakers very acceptable.

S

 

[stunta]

I think the crossover frequency has a lot to do with it. A sub comes in in the 50 to 80hz range. Floor standers cross over those dual (or triple) woofers around 400hz. The LF driver in the stand mounts is the limiting factor because it is covering too much of the audio range.

^ This could explain a lot. The Revel F208 for instance has
-----------------------------------------------------------------------
CROSSOVER FREQUENCIES
270 Hz, 2200 Hz

LOW FREQUENCY EXTENSION
-10dB@23Hz, -6dB@27 Hz, -3dB@31Hz
-----------------------------------------------------------------------

So the two 8" woofers on the F208 are handling everything below 270 Hz.

Here I am asking the 6" driver on the ATC (crossover at 2.5kHz) to handle everything from 2.5kHz to 80 Hz. So its not that the Revels are large speakers, its that they have multiple drivers each handling a narrower band. Obviously the more drivers it has, the larger the cabinet needs to be.

Yes, the frequency response will extend downwards more evenly, but without a crossover from sub to mains, the mains will still be trying to reproduce LF they can't manage, so distortion will be higher and power handling more limited.

Is distortion the issue here? The ATCs measure quite well and known to be some of the lowest distortion speakers. As Ray & Co were saying above, is it more likely the compression? That should also explain the perceived lack of dynamics.

 

[stunta]

Ok, its after 5 PM on a Friday here so I have to hang out with the crew and party. Scratch that, I will go to my basement and take some measurements with REW

 

[andreasmaaan]

^ This could explain a lot. The Revel F208 for instance has
-----------------------------------------------------------------------
CROSSOVER FREQUENCIES
270 Hz, 2200 Hz

LOW FREQUENCY EXTENSION
-10dB@23Hz, -6dB@27 Hz, -3dB@31Hz
-----------------------------------------------------------------------

So the two 8" woofers on the F208 are handling everything below 270 Hz.

Here I am asking the 6" driver on the ATC (crossover at 2.5kHz) to handle everything from 2.5kHz to 80 Hz. So its not that the Revels are large speakers, its that they have multiple drivers each handling a narrower band. Obviously the more drivers it has, the larger the cabinet needs to be.



Is distortion the issue here? The ATCs measure quite well and known to be some of the lowest distortion speakers. As Ray & Co were saying above, is it more likely the compression? That should also explain the perceived lack of dynamics.

Distortion goes hand in hand with power compression, so it’ll be both.

The ATCs are no doubt low distortion within their normal operating range, but no 6” driver is low distortion when asked to play low and loud.

 

[stunta]

So if I keep my ATCs, would a pair of these do the trick? Would I effectively be building something like the Revel F208s? I can then place the ATCs on top of these subs.

F8 Direct Servo bass and midbass subwoofer
F8 is a subwoofer that can cover more than a decade of frequency range of servo control from below 20hz to 250hz.

 

[andreasmaaan]

So if I keep my ATCs, would a pair of these do the trick? Would I effectively be building something like the Revel F208s? I can then place the ATCs on top of these subs.

Without looking at the link in-depth, certainly looks like they would

Before you invest in new gear though, I'd see what improvements you can make with your current sub. Try making the crossover slopes steeper, and raising the crossover frequency, and see whether that gives you an improved sense of dynamics.

6dB/octave @ 80Hz is too low/shallow a crossover slope for a 6" woofer if you want to do more than moderate levels IMHO.