Where did the bass go? Need some help troubleshooting!

A friend of mine is having some problems with his stereo setup. I have tried setting things up correctly, but I fail.

Here is the setup:



S = Speakers ( Klipsch RF7's )
CV = Cerwin Vega (HFA 21"SX)
AE1 & 2 = P1152 (AV15H) from AE Speakers (The subs are facing each other)

Couches = Listening positions

The length on the "left side" is not 6meters btw, but 8m. Did a typo!

As for amplifiers etc, he has:
Vincent SP993 = 2x200W (For Klipsch)
Behringer EP2500 = 2x600W (For the AE Subs)
Carver Preamplifier
Behringer DCX2496 for EQ

All the subs are connected to the DCX2496, and the DCX2496 is connected to the Carver Preamp via Subwoofer Preout.

So as you can see, his setup should be capable of some serious bass.

And that is the problem... I am having difficulties setting things up correctly..

I can say some of the things I have tried:

First of all, I mute ALL the subwoofers, and play just with the speakers. We try some different songs (with bass that varies a bit), I then measured approx how much SPL there was. The Klipsch speakers had no problems putting out around 106dB, at the LP.

Then I unmute the Cervin Vega sub. Same songs, same listening level. No difference in SPL. I try adjusting the phase from 0, 45, 90, 135, 180 degrees. No difference. I try setting the polarity to "Inverted" (And also adjusting the phase again). There is a TINY difference FELT when setting the polarity to inverted, but not much. The SPL is the same (around 106dB). No matter if the CV is CRANKED, there is no difference in the SPL. It's like the bass just.. goes somewhere else.

Note: When im up front with the CV, the bass is INTENSE. And there is a shitload of air coming out of it.. so it's pumping hard!

So, not much difference with the CV enabled. It's a huge 100 kilo subwoofer with a 21" woofer.. it should be able to put out some serious bass. But.. it's not.


Okey. The next thing I try is the following:

I unmute the CV.. Now I want to try and work some with the AE subwoofers. As you can see, these subwoofers are facing each other. The polarity is set to "Inverted" on both of them. We do the same thing, play some songs, measure (and feel). I then disable ONE of them (the one to the left on the picture), and there is NO difference FELT, and NO difference measured. I enable it again, then try to the set polarity to "Normal" on the DCX2496. Still no difference at all. I play around a bit with the Phase, setting it to 90, 180 degrees... no difference.

That's weird?

I would assume if hooked up correctly, the measured SPL should be approximately +3dB. But there really isn't any difference at all, when playing with 1 or 2 of these subwoofers. When stacked, there should be around +6dB increase, I think ?

Note: I have of course checked the drivers, they ARE PLAYING.


To sum it up:
1. Speakers only: A lot of nice bass!
2. With the CV enabled: A tiny bit more bass felt, but not measured (Phase & polarity has been played with)
3. I disable the CV, and try to work with the AE subs - there is NO difference FELT or MEASURED, when im using just one of them, or both (Phase & Polarity has been played with).

What is going on here ?


Any suggestions ?

He's always had problems with "bass disappearing" in that room. Pretty much the entire setup is new, except the CV subwoofer. He do have some experience with it, for example that if he turns it around, he gets a lot more bass at LP. But it doesn't look very good when the CV is turned around. He has also tried it several different places with no big success.

In short: The room is a nightmare when it comes to bass. It always has been.. But I thought that problem could be fixed, by getting more bass spread throught the room (like it is now).

But one thing that was quite surprising, is that the RF7s play VERY LOUD in the room, where they are placed. Lots of punch/bass!

The CV sub has been bypassed before, it behaves the same way with the DCX2496.

As for measuring equipment, Im just using a Digital SPL Meter from Radioshack (I do have an EMC8000.. but I don't see the point in using it. There should have been some dB differences with just the RS).

LTD02, although the idea is very nice, it's not an option (Might be for me though, in the future ). The P1152 are 'sealed', using 2 x 18" PRs, not sure if you know that or not (If not, then I assume they play a bit louder).

What we will try next:
When looking at the picture, we did try one AE sub all the way to the right (the corner with the kitchen opening).. But there was something very wrong with the DCX2496 then, so we got NO bass (They were pumping, HARD.. but it was seriously no bass to be felt, even when sitting close to it). Now that the DCX2496 is configured, we will try putting the AE Subs in that corner. If there is DECENT bass with one, we will stack them, and take it from there.

It should be noted that the owner of the setup has been annoyed with his troublesome room for quite some time, so annoyed that he took up a loan so he could buy a new house (yes, just to get a better room). Hehe.. im not kidding.

He will also get rid of that huge aquarium if need be, and try the subs way back there.


But, first thing first: We try the AE Subs on the right corner !


Edit: Still a bit puzzled though, that the RF7s do so well where they are placed, all on their own !

Minor update:



As suggested, we moved AE Sub 1 to "Location 1" (Near the kitchen opening). When playing with just the speakers & that sub, we were able to get peaks around 116dB (With just the speakers, we were able to get peaks around 106dB) - so that was nice!

Well, if one sub works in that corner, won't 2 be twice as good?

So we stacked both AE Subs in location 1. No matter what we did with the polarity/phase, there was NO increase in bass. 116dB MAXIMUM!

I would like to try the 2nd AE Sub at "Location 2" (Near the Kitchen opening). Perhaps we will get an increase there ? Note: We were not able to do that now, because he has a huge aquarium there now. But he is going to sell it.

If we are able to get an increase with bass there, I would also like to put one CV in the corner, with one AE sub on top of it.

Im still a bit puzzled that there is no increase what so ever, with two AE subs stacked, when one is working well

(On a side note: Im glad I don't have a difficult room like that )

Yes the room is approx. 3400 cubic foot.

When I say "Maximum 116dB", it is when it doesn't get any louder when the volume is cranked up. Red clipping on the amp, but the subwoofers are not clipping, just not going any higher.

As for Xovers, I belive I have a But12 at 90hz, on the AE Subs (I have also set a SS filter on them, at ~17hz). The CV subwoofer is configured to play up to 150hz.

I guess I could use REW to measure the AE Sub that is actually decent where it is placed now, then remeasure with the 2nd AE sub stacked on it - to see what is going on.. Why Im not getting double the output.

Placing all 3 subwoofers (facing each other), what is that good for? Wouldn't they cancel each other out? But surely we can try that, and see what happends!

Note: This is not me or my home, but I will try to measure the subwoofers when I have time, at his place, using REW.

I know he is amp limited.

The point I was trying to make, is that he reached a maximum of 116dB (peaks) on some songs, WITH ONE AE SUBWOOFER (+Mains). With TWO AE subwoofers then, he should be able to get MORE SPL (More than 116dB) at those songs.

So it was on some certain songs (measuring the peaks), not on a sine wave. Not certain what frequencies that were played during those songs.. I guess around 25-60hz.

REW ! REW ! REW !

In order to get to the bottom of this, I will do this, when I have time.



Now that is interesting, and as mentioned: We will try that!



REW again!

0 subwoofers = 106dB
1 subwoofer = 116dB
2 subwoofers = 116dB
3 subwoofers = 116dB

It wasn't 3 subwoofers that added 10dB, just ONE (The AE subwoofer). Adding one more AE subwoofer (stacked) yielded no difference. Adding a 3rd subwoofer (The CV) yielded no difference.


And if I understood you correctly, I should not be expecting no more than 1-2dB increase, by adding a 2nd AE subwoofer (assuming same wattage to it), or a 3rd subwoofer: the CV. Still, that should be ~2-4dB increase, over those 116dB I got with one.

For some reason, I have always thought that if I had one subwoofer that did ~110dB from 20-40hz, I would get ~113dB if I bought an identical subwoofer (not stacking them).. And that I would get ~116dB if I stacked them.

I just thought I could come with a little update:

Instead of trying to fix the bass-mess he had, he bought a new house instead. He actually bought my brother's house (He was the previous owner of the AE subwoofers.. and they rocked !)

So... problem solved New house, awesome bass!