Measured in room bass response of my speakers

[3db]

I had generated some test tones and burned them on a CD running the full gambit from 20Hz ro 20KHz . I was curious to see my speakers bass response and room interaction so here are my findings.

From my seating position, using a 1KHz test tone, I chose a reference value of 74db at the seated locatin. Holding the Rat Shack meter within 6" of the ceiling, I measured 77db.

Frequency; Seated Postion (db); Ceiling (db)
100; 81; 81
90; 82; 81-82
80; 79; 79
70; 76; 78
60; 70; 75
50; 73; 75
40; 61; 64
30; 73; 74
20; 52; 52

The dip at 40 surpised me a little. I also have a rather nast y echo if I clap my hands in that room. Will acoustic treatments smooth out the bass response, particluairy at 40 Hz and will it remove the echo that I expereience when clapping my hands?

 

[MacManNM]

I had generated some test tones and burned them on a CD running the full gambit from 20Hz ro 20KHz . I was curious to see my speakers bass response and room interaction so here are my findings.

From my seating position, using a 1KHz test tone, I chose a reference value of 74db at the seated locatin. Holding the Rat Shack meter within 6" of the ceiling, I measured 77db.

Frequency; Seated Postion (db); Ceiling (db)
100; 81; 81
90; 82; 81-82
80; 79; 79
70; 76; 78
60; 70; 75
50; 73; 75
40; 61; 64
30; 73; 74
20; 52; 52

The dip at 40 surpised me a little. I also have a rather nast y echo if I clap my hands in that room. Will acoustic treatments smooth out the bass response, particluairy at 40 Hz and will it remove the echo that I expereience when clapping my hands?

They wont do much about the bass, thats modal. Try moving the sub around a bit. Rotate, move it further or closer to the wall, things of that nature. It should help the reflections when you clap your hands though.

 

[3db]

They wont do much about the bass, thats modal. Try moving the sub around a bit. Rotate, move it further or closer to the wall, things of that nature. It should help the reflections when you clap your hands though.

That just my main speakers with the sub out. Next time the other half is out shopping, Ill try palying with speaker positioning to see what I can come up with.

 

[jcPanny]

Sub measurements

Fist, I think the ceiling measurements are irrelevant since you wont have your ears in that location. My understanding is that room treatments (bookcase, rugs, carpet, etc.) will help deal with the higher frequency room issues including the echo you described, but bass is more difficult.
Huge, ugly bass traps or expensive electronic equipment would be required.

Your best bet is too experiment with sub locations and positions in the room to see if you can get a better response. It takes time, but the result will be a less boomy sub. Assuming your mains play low enough, set your crossover at 80 Hz or lower to eliminate the bump on the higher frequencies.

 

[3db]

One question I thought off is this..

The s/w used to gnerate the test tones. Is it safe to assume that the levels are equal for all the frequencies generated if I did not touch the level control of the s/w when I generated these tones?

Oh and the subwoofer was turned off whne these tests were run

 

[fergusonv]

Looks to me like you need to be crossed over at around 80hz based on that response. Worry about getting your subs response flat up to there and don't worry so much about the 40hz null, it will be down prob 12db or more at 40hz if you crossover at 80hz.

 

[mtrycrafts]

I had generated some test tones and burned them on a CD running the full gambit from 20Hz ro 20KHz . I was curious to see my speakers bass response and room interaction so here are my findings.

From my seating position, using a 1KHz test tone, I chose a reference value of 74db at the seated locatin. Holding the Rat Shack meter within 6" of the ceiling, I measured 77db.

Frequency; Seated Postion (db); Ceiling (db)
100; 81; 81
90; 82; 81-82
80; 79; 79
70; 76; 78
60; 70; 75
50; 73; 75
40; 61; 64
30; 73; 74
20; 52; 52

The dip at 40 surpised me a little. I also have a rather nast y echo if I clap my hands in that room. Will acoustic treatments smooth out the bass response, particluairy at 40 Hz and will it remove the echo that I expereience when clapping my hands?

If these numbers are direct meter numbers, not adjusted for its inaccurate at low frequencies, then it is not telling you the full story of the real levels. There are correction curves on the net for the RS meter.
For instance: you add 7.5 for the 20Hz, 5 to the 25 Hz, 3 for the 30 Hz, 2.5 for the 40Hz.

 

[j_garcia]

The most common room modes are usually around 40-50Hz.

*edit - removed sub info, put into separate thread.

What speakers are you running again? That's pretty good response for mains.

 

[3db]

The most common room modes are usually around 40-50Hz.

*edit - removed sub info, put into separate thread.

What speakers are you running again? That's pretty good response for mains.

PSB Image T45s

 

[edwelly]

Would one of those Velodyne SMS thingies help with an issue like this?

 

[j_garcia]

Would one of those Velodyne SMS thingies help with an issue like this?

Most likely, but at $400, it probably isn't worth it for a single dip like that. It's harder when it's a dip because you don't want to be boosting big dips and it depends on whether it is a response issue due to placement or if it is truly a room mode. It's not so bad to cut a peak, but boosting a dip can create new problems. I agree about the 80Hz x-over (or even a 60Hz), I'd try that if possible and see what it does.

 

[jaxvon]

Yes it would Ed. A parametric EQ is handy for getting rid of peaks in your frequency response. The nulls are a different story, but if you can get it to where you have peaks only (or something close), then a parametric EQ will give you flat response.

While the velodyne thing is awesome, you can get good results with a Behringer Feedback Destroyer, which is only $99 shipped from Musician's Friend. Ilkka (the guy who did the PB10 vs. EP600 thread) has some good links for software to work with the BFD.

I should mention that the BFD is not automatic like the Velodyne option. It requires you to measure the FR yourself then make the EQ adjustments according to those numbers.