The subwoofer and main speaker output must be in phase

Posted by kh6idf (A) on June 14, 2015 at 11:06:00

In Reply to: Low frequency output didn't match specification posted by Elgee1 on June 12, 2015 at 11:43:29:

The subwoofer could actually be SUBTRACTING bass if it is not in phase with your main speakers at the listening position. See if the bass sounds better with the subwoofer off. If it does, it is out of phase.

If you can get a sound pressure meter like the Radio Shack model, it can measure the amplitude, and you can control the frequency by using a test CD where different frequencies are on different tracks. You can play a 40 Hz tone on 'repeat' and use the SPL meter to measure the response both with and without the subwoofer. Don't be surprised if the response measures lower with the subwoofer. If the SW doesn't have a continuous phase control (best) or phase reversal switch, you can still adjust the phase by moving it around in the room until you find a setting or position where it is increasing the amplitude instead of reducing it.

My subwoofer was reducing the amplitude when on, and it didn't have a phase switch. Since I didn't want to change the location, I opened it up and reversed the leads on the drivers (it had two). Then it increased the bass rather than decreased it. It is probably not exactly in phase (I would need a continuous phase control for that or change the location) but it is much better than it was before I reversed the leads.

The other thing I found was for planar main speakers (I have Magneplanar SMGc's) it sounds much better letting the main speakers run full range than to use the subwoofer's crossover to feed a high-pass signal to to the main speakers. For other types of speakers this may not be the case.

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Follow Ups Full Thread

Topic - Low frequency output didn't match specification - Elgee1 11:43:29 06/12/15 (16)

Measurement Method - Inmate51 16:42:58 06/15/15 (0)

the microphone - dont' go measuring without the right tools nt - BigguyinATL 13:22:14 06/15/15 (0)

The subwoofer and main speaker output must be in phase - kh6idf 11:06:00 06/14/15 (1)

RE: The subwoofer and main speaker output must be in phase - Elgee1 12:11:38 06/14/15 (0)

RE: Low frequency output didn't match specification - coli 10:21:29 06/13/15 (1)

RE: Low frequency output didn't match specification - Tidycat1 10:59:21 06/13/15 (0)

"something missing especially from the orchestral stuff I play" - M3 lover 09:42:25 06/13/15 (1)

RE: "something missing especially from the orchestral stuff I play" - Hornlover 09:24:15 06/15/15 (0)

WHAT!!! Your results may vary? - airtime 14:30:29 06/12/15 (0)

RE: "rated at 40 hz" - genungo 13:06:51 06/12/15 (5)

I agree with this. Get a Radio Shack decibel meter, a frequency test CD , - alaskahiatt 19:06:30 06/12/15 (4)

RE: I agree with this. Get a Radio Shack decibel meter, a frequency test CD , - Tidycat1 21:07:35 06/12/15 (3)

Bass frequencies do not need ROOM to develop - Dave_K 14:10:37 06/13/15 (0)

This is exactly what I did. It was long ago, so I don't remember - alaskahiatt 23:18:14 06/12/15 (1)

RE: "nulls...at least three in that distance" - genungo 08:09:47 06/13/15 (0)

RE: Low frequency output didn't match specification - ErikM 12:14:51 06/12/15 (0)

Follow Ups

The subwoofer and main speaker output must be in phase - kh6idf 11:06:00 06/14/15 (1)

RE: The subwoofer and main speaker output must be in phase - Elgee1 12:11:38 06/14/15 (0)

The subwoofer and main speaker output must be in phase

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