Room Response

**Bob_99** · **06-12-07, 02:53 PM**

When measuring room response, the usual practice is doing the sub, left or right individually or doing the sub with the left or with right in combination. Since many systems now are surround systems what is the correct way to measure so that you can see the total result of the system. Also, if it is possible to measure the whole system, would a pulse be sent to all the speakers as five channel stereo or would you need a pulse that would be processed through one of the sound formats? Does anyone have any thoughts on this?

Thank you.

Bob

**Ethan Winer** · **06-12-07, 03:40 PM**

Bob,

Quote:

Does anyone have any thoughts on this?

Yes, I have thoughts on this.

Seriously, you are correct that the entire system is what matters. It's a good idea to check each speaker separately too, but with most music bass instruments are panned to the center. So most important is to test with at least the left and right fronts, and the sub, all active at once.

--Ethan

**Bob_99** · **06-12-07, 03:47 PM**

Thank you Ethan. The reason that I asked is because I was experimenting with different combinations and I noticed that if I did the left/right/sub together, then some of my dips above the crossover frequency were minimized

. I wasn't sure if what I was doing was valid testing but what you wrote seems to confirm my thoughts.

Bob

**bpape** · **06-12-07, 05:40 PM**

Yup. Test the left and right full range, the sub full range, then the L/R/Sub together with the crossover. What you're seeing is exactly what we're looking for - the ability to smooth things based on the interaction. If you see it worse around the xover, then you have a couple things that can be done - adjust phase or move the sub slightly or both.

Bryan

**Bob_99** · **06-13-07, 07:40 AM**

Bryan,

Thanks for your input. Any thoughts on the center and surrounds?

Bob

**Ethan Winer** · **06-13-07, 11:56 AM**

Quote:

Bob_99 wrote:

Any thoughts on the center and surrounds?

In all honesty I've never done that in my HT, though I probably should. Then again, it sounds fabulous as is, so inertia keeps me from obsessing over it.

--Ethan

**Bob_99** · **06-13-07, 12:28 PM**

Thanks Ethan. I may try and few things just to get a better understanding of the interaction of the speakers. I'm not sure if there's anything to learn but from what you said about books on home acoustics and such, it may be the only way to learn and maybe get some understanding of the total system.

As always, appreciate your taken time to answer my questions.

Bob

**wilsonj** · **06-13-07, 05:42 PM**

Hi Bob,

I recently asked this same question in the REW forum. Particularly in relation to the integration of the sub to the LCR speakers.

What was suggest to me is basically what Bryan and Ethan said above.

I'll run through what I did anyway.

First thing was to EQ the sub, then run in 2.1 (front LR and sub) and use a sweep up to 200hz. This way I could see how the xover point performed. I then played with both the hp and lp filters on my preamp and the phase on my sub until I got a response I was happy with. This took some time to find a combo that worked well.

I assumed the centre channel should perform the same as the LR. Ideally I should still try a response for LCR+sub but I am happy the way it is.

Unless you run full size/range rear speakers, I wouldn't worry too much about them. Mine are crossed over above the point of causing any problems with the sub driver, which from what I have seen so far is where the majority of the problems occur. I did however check the phase, but left it at that.

Jamie

**Bob_99** · **06-14-07, 09:35 AM**

Jamie,

Thank you for your input. The reason that I mentioned the surrounds is because I have them crossed at 80Hz and I was wondering how they would affect the 100Hz to 200Hz region. As you mentioned, it may not be critical but at this point, my curiousity is peaked.

Thanks again,

Bob

**Ethan Winer** · **06-14-07, 12:27 PM**

Quote:

Bob_99 wrote:

The reason that I mentioned the surrounds is because I have them crossed at 80Hz and I was wondering how they would affect the 100Hz to 200Hz region.

I'm sure some low frequencies come out of the surrounds, and the really low stuff is sent to the sub and can potentially combine to create peaks and nulls. But you know what? There's nothing much you can do about it! Other than add more bass traps of course.

--Ethan

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