[Big Red Machine]

More photos in my Gallery.

Here's one, left and right sweeps done but not plotted yet.

[Big Red Machine]

I did not get the level that same as the previous stereo set but plotted them all on the same chart anyways.

[MaxCast]

Hi Danny,
We listen with both speakers so wouldn't it make sense to play both speakers and try to correct for flattest response with position and room treatment?

Yea but we listen in stereo. Left and right speakers don't get the same signal. If they did then we'd be listening in mono. A mono signal (like the test signal) played on two speakers will cancel each other out or couple to give you twice the output level depending on distance and wavelength.

You have to shoot them individually or you won't know what you have.

Is that true from 20-20,000? 
Why do both my woofers do a dance on low notes?  Are they playing something different?

If we shoot each of them how do we interpret the results?

two speakers will cancel each other out or couple to give you twice the output level depending on distance and wavelength

I see by Pete's graph the canceling and the coupling, but what do you do with that?
What about dual subs?

This is interesting to me as I have never heard of this before.  And I am sorry for hijacking Pete's thread.  Would you care to elaborate in the acoustics circle if I start a post?

[Danny Richie]

Is that true from 20-20,000? 

Sure.

Why do both my woofers do a dance on low notes?  Are they playing something different?

Let's say they are both playing a 20Hz note. That means only 20 movements per second (slow compared to the rest of the spectrum). Can you tell be looking at it if they are in time with each other?

If they are in time with each other (and in a lot of music material they are) they will likely couple and create gain. One has to be delayed in time in relation to the other to be out of phase and cancel.

Check this thread out about stacking speakers. On the second page I responded with measured data. Really check out that post. You'll get it. You will see that it is the shorter wavelengths that are more easily cancelling each other out.

http://av123forum.com/showthread.php?t=15154

I see by Pete's graph the canceling and the coupling, but what do you do with that?
What about dual subs?

It is hard to tell from what Pete posted. It looks like his output of a single speaker is down 20db from the output of both of them in the lower region. Plus the response does not look anything like what I would expect from that speaker. If anything a room response will have a softer and more rolled off top end as the shorter wavelengths are more easily attenuated by the room.

Would you care to elaborate in the acoustics circle if I start a post?

I can post some measured data for you on this when I get a chance.

[Ethan Winer]

Is that true from 20-20,000? 
Why do both my woofers do a dance on low notes?  Are they playing something different?

Most pop music has the kick drum and electric bass centered to play equally from both channels. So I agree with measuring low frequencies, anyway, while driving both speakers together. But it's useful to test each speaker separately too. So you're both right.

--Ethan

[laserman]

Pete,

Thank you for getting this thread back on track, and sharing your graphes and pictures of your new room setup.

I have a couple of questions though after viewing the posted picture and others in your gallery.  It looks like you moved your speakers 90 degrees to a new wall.  Is this the short wall?  Had you tried this set up before, and if so with the HT3s or a different pair of speakers?  From the pictures it appears the fabric looks shiny.  What did you use?  How thick are the OC703 panels on the wall and ceiling?

Thanks in advance,
Lou

[Big Red Machine]

I was able to get with Bryan face-to-face at RMAF and a one step at a time plan was discussed.  So I went for broadband absorption in all the usual places first and then we'll go from there.

So I cut my 6" bass traps down on the table saw to 2" 4-sided frames for the 703 and used the mirror technique for first reflections of both speakers on the sides and ceiling.  Placed the traingles in the corners and I had 2x 1x4x0.5 foot bass traps left over.

Found some funky polyester at Joanns Fabric and just used compression to hold the material inside the frames.

I was on the long wall before and my ears were right against the back wall as a result.  So now I have about 4 feet+ behind me and actually have the speakers farther apart on the short wall.  I dismantled my old rack and except for longer runs of IC's now needed, the overall result is cleaner and the room feels twice as large.

Sounds better but every time I see the graphs I want to grab a Tact and "fix" it.  I'm a little obsessed but not overly so with having a "flat" room response.  I'm interested if I need any diffusers evetually or should more absorption be done.  Pretty crude using the Ratshack meter and even though I sit next to my chair with the meter on a tripod in the chair, if I move in to see the reading, the reading changes as I reflect more to the mic.  If you have ever tried this, you will find out how sensitive frequencies over 500 hz really are!

Hopefully by Xmas I can review all the equipment I have had in and out of there recently and continue to play with.  You'll notice I was deliberately excluding any equipment shots except for the HT3's.

[laserman]

Pete,

Thanks for the feedback info.

I'm a relatively new convert to room treatments and try to learn as much as possible from others.  Each listening room has it's own set of tics and fleas to get rid of.    I have treated my two separate listening rooms with significant positive affects.  So much so, I have invited others and they too have become converts to how important room treatments are over using electronic methods.  However, sometimes that may be the only answer, if you know what I mean (WAF).

The polyester material you used is shiny because it is treated with something from the manufacturer, correct?  I thought I read some where that using such a treated fabric would be okay only if you want to reflect higher frequencies verses midrange and lower frequences.  It appears from your gallery you moved away from foam have totally embraced rigid fiberglass.   So, with the shiny fabric you basically went from absorbing some of the energy of the higher frequencies (foam) to much less absorbtion (rigid fiber glass with shiny polyester), is that a correct assessment too? 

I like your corner trap idea and it seems pretty easy to mimic.  Do you feel you got better results with this method verses say a 6" thick fiberglass panel placed equal distance from the corner of two adjoining walls thereby trapping an air pocket behind the panel?  Did you use any faced 703 or just unfaced on the panels?

Thanks again,
Lou

[bpape]

The idea of measuring each separately is to see what each is doing in relation to room boundaries.  Measuring them together allows you to see what's really happening with real material (sometimes they're the same, sometimes not.)  Using both of those plots together allows you to pick and choose how best to place things to use the anomolies to your advantage.

Overall, for a first shot, you're not doing bad Pete.  Up to 300Hz, you're +/-5db in-room unEQ'd.  A lot of people would kill for that.  There are probably some additional things we can do to smooth it out a bit.  Tweaking sub/speaker locations and seating locations may yeild a small improvement.  Inches matter. 

Do the sub first if you have one.  That's independent of the imaging so much easier to do.  Then do the mains full range.  Even though they may be cut off, it's not a brick wall so there will be some overlap.  Getting a peak from the mains to overlap with a dip from the sub can help smooth things out nicely.

Then we play with the seat.  ... and repeat.  If you're going to use EQ, then shoot for a response curve that has peaks in it rather than nulls. 

Bryan

[Big Red Machine]

No sub Bryan - pure HT3 output there, baby.  I did offset my seat 6" to one side so I am not in the dead center of the room.  The extra space is on the left side and may account for the response deltas of each channel.

It sound really good.  I think I need a more consistent high frequency measuring device than the RS meter.

Lou, I'll answer your questions in a few days after my biz trip.

[bpape]

Absolutely.  Getting off center a bit will help at the seat but change the SBIR from side to side.  A 2-4" thick panel directly beside and directly behind each speaker will help offset this and also smooth things out more in general.

With no sub, it's just a back and forth with speaker positioning and seat placement to get the balance right.  Do all of this prior to putting up the panels I mentioned above.

Bryan

[Big Red Machine]

Here is a layout consistent with the photos I attached.  Where, oh where, should the diffusion go?

[bpape]

Most likely on the side walls behind your listening postion.  Not enough distance to the rear wall for it to be effective.

Bryan

[Glenn K]

3' from the back wall? Any way I can talk you into going 6" on that panel? 

Glenn

[Big Red Machine]

3' from the back wall? Any way I can talk you into going 6" on that panel? 

Glenn

That's easy.  I expected to put diffusion there with absorption behind it.  So how will added low frequency grabbing help there?  When I walk around the room I can "feel" the boom where there is no bass trapping and am happy that in the bass trapped corners there is no "pressure".   I don't recall any "pressure" behind my seat.  IS the 6" going to add any diffusion effect?

[Ethan Winer]

Where, oh where, should the diffusion go?

Since you emailed me a link to this thread through my RealTraps account, I assume you want my sales advice?

I'd put three of our Near type bass trap / diffusors on the near wall behind you, and one Far type in the deeper part of that wall.

--Ethan

[Big Red Machine]

Most likely on the side walls behind your listening postion.  Not enough distance to the rear wall for it to be effective.

Bryan

How about the horizontal surface on the bottom of those beams?

[bpape]

Again, it's so close to you that diffusion really isn't effective in a direct path.  Additionally, it's not opposite a hard surface so there's not even any benefit of eliminating slap.

On the side walls behind you it's really not as much of a direct thing as creating a blended diffuse field around you that's coming back at you from all surfaces AFTER hitting the diffuser and then hitting the other surfaces.

Now, on the vertical face of the beam that's facing the rear of the room might be an additional surface to address though it's likely so small that any standard diffusor isn't going to fit. 

Filling the D1 with absorbtion in the cavity can provide some small amount of bottom end control without compromising the performance of the diffuser.   

Bryan

[Big Red Machine]

Bry,
On the side walls, is a pair vertically in a 2' wide by 4' high config preferred over side by side?  At ear level?  Ribs vertical?

[bpape]

If it was me, and 2 was it on each side, that's what I'd do.  I'd also leave maybe 6" between them. 

Bryan