2nd time around..measurements

**Mattlock** · **12-29-07, 01:27 AM**

Well after royally screwing up my first attempt at measurements....here's my 2nd attempt...

Sub only
700 liter sonosub, FI Q18 tuned to 13hz, powered by EP2500, with BFD1124.
Crossover set at 80.

First graph without filters
2nd...with filters...

any thoughts or suggestions....

Still alittle confused about setting the target..looks like they should match up to compare the filter effect? correct?

thanks
Matt

**Otto** · **12-29-07, 07:18 AM**

Hi Matt,

You can overlay the plots on the same set of axes so they're easier to compare. In the filter window, there are tabs, and one is called "All Measured." Select that one and then you will be allowed to choose which of your (up to) nine measurements you want to overlay.

I would probably push the output of the sub a little bit, such that you go above the target by 5 6dB or so. Then, you will be able to quash peaks more, such that you get a flatter response. This assumes you have the headroom, which you will with the EP2500 amp. Just turn the amp gain up a little and remeasure and refilter.

I also like to apply some gain in the dips. Not too much, and I like to play with it manually, either on the front panel of the BFD or through REW and the MIDI download (either way is OK, but the point is it's me picking the filter values, and not REW).

**Mattlock** · **12-29-07, 09:57 AM**

Quote:

Otto wrote:

Hi Matt,

You can overlay the plots on the same set of axes so they're easier to compare. In the filter window, there are tabs, and one is called "All Measured." Select that one and then you will be allowed to choose which of your (up to) nine measurements you want to overlay.

I would probably push the output of the sub a little bit, such that you go above the target by 5 6dB or so. Then, you will be able to quash peaks more, such that you get a flatter response. This assumes you have the headroom, which you will with the EP2500 amp. Just turn the amp gain up a little and remeasure and refilter.

I also like to apply some gain in the dips. Not too much, and I like to play with it manually, either on the front panel of the BFD or through REW and the MIDI download (either way is OK, but the point is it's me picking the filter values, and not REW).

Okay Otto, Since I set up my system with my amp gain at max, I assume I can adjust my SW output on my receiver to boost the output. I will also overlay and repost. I'll play around with some gains but from my understanding I should keep these on the lower side to prevent clipping???

thanks again for your suggestions. BTW...should my Target be the same for both measurements? seems logical but I have to manually adjust when I re-measure with filters. Make sense?

**Otto** · **12-29-07, 10:01 AM**

Yeah, you can turn up the SW output on the receiver, or you can just turn up the volume knob on the receiver. Either way will work. I'd probably go with the master volume knob since it's easier.

I don't think that Target is super-important. I usually set it at the beginning and then just tweak till I get close to the desired curve. You're doing fine, and on the right track!

**Wayne A. Pflughaupt** · **12-29-07, 10:09 AM**

Matt,

IMO your response is highly problematic, to the point that it’s probably unequalizable. You have about a 30 dB or more differential between some of your peaks and depressions. That needs to be narrowed to something workable, i.e., ~15 dB or less.

Often when we see response this bad, the problem is a bad sub location. Do you have any other placement options? I’d try a good corner (i.e., one with no unsealable openings in either wall), if you have one available.

Also, it appears you applied some equalization way up in the 130 Hz range. You don’t have your sub crossed over that high, do you? There’s usually no need to apply equalization above the crossover frequency.

Regards,
Wayne

**Mattlock** · **12-29-07, 10:15 AM**

Quote:

Wayne A. Pflughaupt wrote:

Matt,

IMO your response is highly problematic, to the point that it’s probably unequalizable. You have about a 30 dB or more differential between some of your peaks and depressions. That needs to be narrowed to something workable, i.e., ~15 dB or less.

Often when we see response this bad, the problem is a bad sub location. Do you have any other placement options? I’d try a good corner (i.e., one with no unsealable openings in either wall), if you have one available.

Also, it appears you applied some equalization way up in the 130 Hz range. You don’t have your sub crossed over that high, do you? There’s usually no need to apply equalization above the crossover frequency.

Regards,
Wayne

Wayne,
thanks. I may be able to put the sub up front left next to picture...it's already wired. Challenge is I have my front speaker there as well. It may mean I have to reduce my screen little due to the diameter of this beast....see picture. Currently it is in rear behind the couch. (not in pic but there now) I'll play around with it and re-measure.

**brucek** · **12-29-07, 10:28 AM**

Matt - some tips.......

Use logarithmic display and not linear display for your graphs. Press the Freq Axis icon in the top right corner of REW.

Use a vertical scale of 45dB-105dB and a horizontal scale of 15Hz -200Hz.

There is a Filter Sort icon on the Filters screen to order your filters from low to high. It's very useful.

brucek

**Mattlock** · **12-29-07, 04:42 PM**

Quote:

Wayne A. Pflughaupt wrote:

Matt,

IMO your response is highly problematic, to the point that it’s probably unequalizable. You have about a 30 dB or more differential between some of your peaks and depressions. That needs to be narrowed to something workable, i.e., ~15 dB or less.

Often when we see response this bad, the problem is a bad sub location. Do you have any other placement options? I’d try a good corner (i.e., one with no unsealable openings in either wall), if you have one available.

Also, it appears you applied some equalization way up in the 130 Hz range. You don’t have your sub crossed over that high, do you? There’s usually no need to apply equalization above the crossover frequency.

Regards,
Wayne

Well,it looks like I limited to the rear. The speaker is simply too large to be moved up front (left). I can move around a little in the rear (to the left) so that it is right beside the cutout wall. Its only about 2 feet but can't hurt to try.

more later

**Mattlock** · **12-29-07, 04:46 PM**

Quote:

brucek wrote:

Matt - some tips.......

Use logarithmic display and not linear display for your graphs. Press the Freq Axis icon in the top right corner of REW.

Use a vertical scale of 45dB-105dB and a horizontal scale of 15Hz -200Hz.

There is a Filter Sort icon on the Filters screen to order your filters from low to high. It's very useful.

brucek

Will do brucek....thanks for the suggestions

**Mattlock** · **12-29-07, 04:49 PM**

Quote:

Wayne A. Pflughaupt wrote:

Matt,

IMO your response is highly problematic, to the point that it’s probably unequalizable. You have about a 30 dB or more differential between some of your peaks and depressions. That needs to be narrowed to something workable, i.e., ~15 dB or less.

Often when we see response this bad, the problem is a bad sub location. Do you have any other placement options? I’d try a good corner (i.e., one with no unsealable openings in either wall), if you have one available.

Also, it appears you applied some equalization way up in the 130 Hz range. You don’t have your sub crossed over that high, do you? There’s usually no need to apply equalization above the crossover frequency.

Regards,
Wayne

Wayne....got a semi-random question for you. Does it make any sense for me to consider a 2nd sub up front if indeed I cannot get the peak/dip range shortened? Still learning here but somewhere I read that dual subs must be tuned the same (13hz) in my case so the point if probably moot because with 8.5feet ceilings I can only go so high with a narrower diameter...just thought I would ask....

Had this crazy idea....Was playing around with Sonosub.exe and it looks like I may be able to get a 24 inch diamter sonosub but the specs would have to be...500 liters, 6.5ft tall, port 8x40, which would give me a 13hz tune.....have I gone off the deep end?

**Mattlock** · **12-29-07, 05:35 PM**

Here's my graph using the logarithmic display and changing my graph scales per Brucek.

Anyone with more filter suggestions or other comments?

thanks

**Jman** · **12-29-07, 06:07 PM**

Do you have any space for bass traps?

**Mattlock** · **12-29-07, 06:32 PM**

Quote:

Jman wrote:

Do you have any space for bass traps?

hmmmm...not real sure....school me a little on what these could do for me?

**brucek** · **12-29-07, 10:15 PM**

Matt, any chance you can show me your impulse response graph of your measurement?

brucek

**Mattlock** · **12-30-07, 04:58 PM**

Quote:

brucek wrote:

Matt, any chance you can show me your impulse response graph of your measurement?

brucek

Bruce,
Here is my impulse graph.....

**brucek** · **12-30-07, 05:27 PM**

Just wanted to see where the noise floor was in relation to the signal.

Signal is ~40dB above the noise. Not great, but OK. Sometimes the response graph looks a bit like yours when there's a lot of noise....

Does your Check Levels routine work out OK for you when you're setting up?

brucek

**Mattlock** · **12-30-07, 05:31 PM**

Quote:

brucek wrote:

Just wanted to see where the noise floor was in relation to the signal.

Signal is ~40dB above the noise. Not great, but OK. Sometimes the response graph looks a bit like yours when there's a lot of noise....

Does your Check Levels routine work out OK for you when you're setting up?

brucek

think so but I'll double check....what could be the culprit on the noise?

**kbgl** · **12-30-07, 05:45 PM**

Matt.... Forget what I said to do yesterday by PM!

**Wayne A. Pflughaupt** · **12-30-07, 05:50 PM**

Matt, are you using both of these subs?

Regards,
Wayne

**Mattlock** · **12-30-07, 05:52 PM**

Quote:

Wayne A. Pflughaupt wrote:

Matt, are you using both of these subs?

Regards,
Wayne

no...just the big one....plan on selling the other

**Wayne A. Pflughaupt** · **12-30-07, 06:03 PM**

Quote:

Mattlock wrote:

Wayne....got a semi-random question for you. Does it make any sense for me to consider a 2nd sub up front if indeed I cannot get the peak/dip range shortened?

It may make things worse. You could do some checking using the SVS before you sell it, but don’t forget to level-match them first.

Quote:

I may be able to put the sub up front left next to picture...it's already wired. Challenge is I have my front speaker there as well. It may mean I have to reduce my screen little due to the diameter of this beast....see picture.

Maybe you could lay it on its side? You’d have to do something to keep it from rolling, of course. And make some kind of custom stand or wall mount for the left speaker...

Your before and after graph, does the “after” sound any better?

Regards,
Wayne

**Mattlock** · **12-30-07, 06:08 PM**

Quote:

Wayne A. Pflughaupt wrote:

It may make things worse. You could do some checking using the SVS before you sell it, but don’t forget to level-match them first.

Maybe you could lay it on its side? You’d have to do something to keep it from rolling, of course. And make some kind of custom stand or wall mount for the left speaker...

Your before and after graph, does the “after” sound any better?

Regards,
Wayne

Havent really had time to do much comparison yet but will soon. These holiday plans just get in the way of more important things..

**JohnM** · **12-31-07, 05:24 AM**

From the impulse response the distortion looks very high, getting on for 10% 2nd harmonic and several % 3rd harmonic. May want to check the sub isn't being driven too hard.

**Mattlock** · **12-31-07, 06:19 AM**

Quote:

JohnM wrote:

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