1st rew graph

**Dwight Angus** · **09-03-08, 12:04 PM**

I have taken several measurements but found this one to represent the best location todate. I colocated the subs at the listening position with the spl meter positioned in the front corner. I expected better spl at this location. I am less concerned about the peaks as I expect a bfd (not yet purchased)will solve that problem.

I will continue to check other locations but is there anything else I can do to improve these results?

cheers

Dwight

Name: 1colocated stacked front corner full crossover and full phase.jpg
Views: 121
Size: 60.1 KB

Name: 1colocated stacked front corner full crossover and full phase.jpg
Views: 121
Size: 60.1 KB

**Wayne A. Pflughaupt** · **09-03-08, 01:01 PM**

Without the BFD all you can do is experiment with different positions. This one looks pretty good though...

Regards,
Wayne

**salvasol** · **09-03-08, 01:05 PM**

Does your receiver has a Parametric Equalizer??? ... if it does, you can try making some adjustments for the 48Hz-68Hz deep

Before the adjustments ... try different positions (just set the sub at the listening position, and crawl around the room to find the best spot)

**Dwight Angus** · **09-03-08, 02:08 PM**

Hi Wayne
Yeah I will order a bfd shortly but for now I wanted to determine where these subs should be positioned. This graph shows the best results todate. I am concerned with the lack of spl in the 15-28 hz range and I suspect I will have to upgrade to larger subs to achieve that improvement. Should I be concerned about those peaks or am I
correct in assuming the bfd will address that?

cheers
Dwight

**brucek** · **09-03-08, 02:31 PM**

Quote:

am I correct in assuming the bfd will address that?

Yep, easily..........

brucek

**thewire** · **09-03-08, 03:25 PM**

That looks kind of like my subwoofer measurement. My BFD works very well.

**carls64** · **09-03-08, 03:25 PM**

Mine looks very similar to yours, I had two subs a 10" DCM and a 8" Polk, the 8" Polk seems to fair better firing into the corner of the room, where as the 10" DCM seems to not have the low end 15-20 as the Polk. I have that same peek though between 30-50 you have.

Based on what I have been reading are we simply (not so simply maybe) measuring mostly our subs, even though the Polk I have seems to have the best curve, without both subs I don't seem to have the impact I had with both subs in place. I have a couple older Boston Acoustic 8.4 Subs I had in my car years ago, and a couple sound stream reference 300 amps I am wondering if I can come put with a way to power those and try a DIY sub system ;-)

**carls64** · **09-03-08, 03:27 PM**

Here is my best reading on my DCM:

**thewire** · **09-03-08, 03:49 PM**

Quote:

carls64 wrote:

Mine looks very similar to yours, I had two subs a 10" DCM and a 8" Polk, the 8" Polk seems to fair better firing into the corner of the room, where as the 10" DCM seems to not have the low end 15-20 as the Polk. I have that same peek though between 30-50 you have.

Based on what I have been reading are we simply (not so simply maybe) measuring mostly our subs, even though the Polk I have seems to have the best curve, without both subs I don't seem to have the impact I had with both subs in place. I have a couple older Boston Acoustic 8.4 Subs I had in my car years ago, and a couple sound stream reference 300 amps I am wondering if I can come put with a way to power those and try a DIY sub system ;-)

I have a bunch of Boston Acoustic 5.5" speakers, they are really great but I have not heard the subwoofers before. I used two kicker competition 15" in my previous HT powered by the same amps I am using on the new four 12" subwoofers. Try placing them on the right wall if you decide to use them.

Edit: mine are Boston, not sure they are Boston Acoustic.

**Dwight Angus** · **09-03-08, 04:01 PM**

Hi Salvasol
No I don 't have a parametric equalizer on the avr so I need to get a bfd. The dip from 48hz to 68hz do I need to worry about that as it is at the target line and the dip below the target line appears small? I thought I would need to concern myself if the dip was significantly below the target line similar to the one at 15hz to 28hz range. My fear is my subs may not capable to filling that void.Not sure if I have enough understanding the what the graphs means at this early stage.

cheers
Dwight

**Dwight Angus** · **09-03-08, 04:11 PM**

Hi Steven
good to hear the bfd works well on those peaks

**Dwight Angus** · **09-03-08, 04:24 PM**

Hi Carl
Yes your curve is very similar to mine. Looks like you have better spl then me in the lower range.I want to get better spl in the 15hz to 30 hz range. My room is 25 ft long by 17 ft wide. I thought 2 10 inch subs would deliver the impact if they are colocated in a corner. I may have to go to a larger sub. In the meantime I will order a bfd and do some more testing.

**salvasol** · **09-03-08, 09:56 PM**

Quote:

Dwight Angus wrote:

No I don 't have a parametric equalizer on the avr so I need to get a bfd. The dip from 48hz to 68hz do I need to worry about that as it is at the target line and the dip below the target line appears small? I thought I would need to concern myself if the dip was significantly below the target line similar to the one at 15hz to 28hz range.

No you don't have to worry about it ... I suggested about the EQ so you can level that range to the rest of the curve

Have you measured the sub response with the mains and see how it looks??? ...I remember that when I did my tests, subs alone where missing something on the lower end too ... but when I added the mains the graph improved a lot

**carls64** · **09-03-08, 11:07 PM**

I am giving serious thought to one of the budget priced SVS subs like this one: 20-39PCi

**Wayne A. Pflughaupt** · **09-03-08, 11:25 PM**

Quote:

Dwight Angus wrote:

The dip from 48hz to 68hz do I need to worry about that as it is at the target line and the dip below the target line appears small?

Not really, what you would need to do (with the equalizer) is drop the areas above and below to the Target curve.

Quote:

I thought I would need to concern myself if the dip was significantly below the target line similar to the one at 15hz to 28hz range. My fear is my subs may not capable to filling that void.

If you're asking if your sub can fill the void below 28 Hz, that would be correct. However, equalizing the reading below 50 Hz down to the Target curve would get your extension down to about 25 Hz, which would be a significant improvement.

Regards,
Wayne

**Dwight Angus** · **09-04-08, 03:04 PM**

Hi Salvasol
No I have not taken any full range measurements yet. I thought I would wait until I hook up a bfd first

btw what bfd model should I look that?

**Dwight Angus** · **09-04-08, 03:10 PM**

The 20-39 is a nice looking sub. Have you demoed it yet?

**Dwight Angus** · **09-04-08, 03:19 PM**

Hi Wayne
I thought the bfd would only reduce peaks down to the target line. Can I also flatten or reduce dips as well. I have that small dip at 58hz. I read somewhere there is a risk of clipping if you input filters to eliminate dips. Is that correct or maybe I can make limited adjustments up to a certain threshold?

**brucek** · **09-04-08, 03:35 PM**

Quote:

Is that correct or maybe I can make limited adjustments up to a certain threshold?

You can make small gain adjustments as long as the room allows it. You have to check this with REW. There are dips that will not correct, no matter the gain that is thrown at them. Usually a dip is caused by a reflection that is the opposite phase, so if you add gain at that frequency, the reflected opposing signal will also increase and you end up right where you started. Generally it's best to stick with cuts...

brucek

**thewire** · **09-04-08, 03:42 PM**

Peaks or dips can be controlled with PEQ. The problems that may be are that the frequency that you are trying to boost will be a null and thus increasing the amplitude of the wave will only make matters worse to cause these peaks to become cancelled by the room. Boosting a dip that is caused by creating cuts for example will work. How much you will do some you will want to watch for. If there is clipping it will be audible. Most people jump out of their seat if they hear it. I have read that a +3dB boost is pretty acceptable. I have done as much as boost as the BFD would allow before around 20Hz but it only seemed to make things in the room vibrate more. I think you loose that certain dynamic sound that is usually sought after in subwoofers with a boost that large for example. If there is a boost it should be a larger bandwidth as a narrow one will actually sound like a resonance.

**Dwight Angus** · **09-06-08, 11:12 AM**

Thanks Brucek

I just ordered a bfd FBQ2496. It should be delivered within a few days. I will take a few measurements once I input the filters and then post the results.

cheers
Dwight

**Dwight Angus** · **09-06-08, 11:19 AM**

thanks Steven
Once I get the bfd I will first eliminate the peaks and then listen to determine if any further adjustments are required. I am hoping to avoid the dips if possible.

cheers
Dwight

**Wayne A. Pflughaupt** · **09-06-08, 12:28 PM**

Quote:

Dwight Angus wrote:

Hi Wayne
I thought the bfd would only reduce peaks down to the target line. Can I also flatten or reduce dips as well. I have that small dip at 58hz.

The other guys have pretty well answered your question. I'll just add that the dip at 58 Hz is insignificant and doesn't require any attention.

Quote:

I read somewhere there is a risk of clipping if you input filters to eliminate dips. Is that correct?

It's correct, but you can simply re-adjust the input level (from the receiver) to keep the meters out of the red.

Regards,
Wayne

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