[Nils]

I've been playing around with my newly-acquired piles of acoustic treatment, and with one exception, I have a room that sounds quite amazing.  The bass is mostly even, incredibly transient, and well-articulated.  Detail, soundstage, and imaging are wonderful -- there's a real sense of the acoustic space of the recording.  It's quite amazing.

The one exception is that it feels like some of the midbass has been sucked out completely.  This issue arose only after both walls were treated.  I suspect that the listening-level monster bass traps are doing their job a little too well, and that I should experiment with replacing them with absorption that doesn't work so darn well on the 200-500hz region.   It also might be I'm hearing the flaws in my current (lacking) setup.  My Bryston 7B-SSTs are arriving this week, and my Magnepan 3.6s are waiting to be hooked up in the other room. 

Pictures are below.

And BTW -- the diffusion stays.  Line-source dipoles + diffusion on the front wall is something magical.

The front wall: GIK tri-traps, GIK 244 panels, GIK D1 diffusors, Sonex panels


The rear wall, GIK monster bass traps, Sonex panels, Golden Sound acoustics discs

[1000a]

The one exception is that it feels like some of the midbass has been sucked out completely.  This issue arose only after both walls were treated. 

I am no expert but have been messing around a little with my own DIY panels and bass traps

did the mid bass go after the back wall was done?  I would try the monster bass traps in the rear corners (straddling th ecorner if possible- if not as close to the wall joint as possible and see what happens. I think you are right that position for the monster traps is not a good one- that typically is a diffifusion or absorbtion postion behind the listening position. 

from what I read you probably only need diffusion and or basic absorption at the position the monster bass traps are placed.

hope this helps

[ctviggen]

How do you know the midbass isn't correct as is and was too high prior to the room treatments?  Maybe what you're hearing now is right.  Without some type of actual data in that range, you won't know.

[bpape]

Well, 200-500 is going to be sucked up by pretty much everything - even the Sonex.  Are you sure this is the range you think you're missing?  Can you describe what parts of the music don't seem right to you?  Just trying to get a better handle on things to work through with you.

Bryan

[samplesj]

Where do you sit in relation to the back wall?  Is it the same distance as the speakers from the front wall?  That Cardas "trick" cancelthe backwave bass which might otherwise cloud those frequecies.  However even if you are sitting at that position is it possible that the absorption on the back wall is doing its job and you aren't getting the cancelation of the rearwave by the bounce of the front wave?  I'm not really sure and just like you I have absorption back there (6" of 703 [3 2" sheets with only 1 foil faced toward the room]).  I didn't really notice a bass loss or smearing when I did that so maybe it isn't a big a deal.

I would definately lose the bass traps in the front corner floor.  I know the corners are perfect trapping locations, but with a dipole you are shooting right into them.  In my HT system I used them, but they weren't even considered in the Maggie system.

Where are your FRP traps?  Maybe you could move the tritraps to the back and take the back ones to the side for the first reflection point?

As a side note, how high do you have your diffusion placed?  It seems to be too high since it goes above the speaker and still leaves lower stuff undiffused, but maybe that is just a much shorter speaker than your 3.6's will be.  My 4'x4' block of skylines don't extend past the top or bottom of my 3.6's.

[bpape]

The Tri's laid on the ground like that should still allow good spherical bass radiation from the Maggies with no issues.

The Monsters on the rear are there specifically to help with killing the bounce off the back wall that will cause the null based on the distance from ears to rear wall/speakers to ears. 

I will agree that a potential slight seat move might help the situation.  Sometimes when you kill one issue, another that was being cancelled by the one you just killed pops up. 

Bryan

[Nils]

I would definately lose the bass traps in the front corner floor.  I know the corners are perfect trapping locations, but with a dipole you are shooting right into them.  In my HT system I used them, but they weren't even considered in the Maggie system.

Where are your FRP traps?  Maybe you could move the tritraps to the back and take the back ones to the side for the first reflection point?

As a side note, how high do you have your diffusion placed?  It seems to be too high since it goes above the speaker and still leaves lower stuff undiffused, but maybe that is just a much shorter speaker than your 3.6's will be.  My 4'x4' block of skylines don't extend past the top or bottom of my 3.6's.

The 244s and tri-traps along the ground help out quite a bit in my acoustic space, I've found.  I am also using an ACI Titan II for the last few octaves, and the bass tightens up considerably with the combination of diagonal 244s + tri-traps.

As for my FRPs along the side wall, well, one side wall is a giant sliding glass door out onto my balcony (at least it has vertical blinds that can be shuttered to have convex surfaces along that sidewall.  The other side opens out into my dining area and kitchen.  While the listening room half is effectively 12' x 17' x 8', the actual entire room is 17' x 21' x 8' (not shabby dimensions for room modes!)

The diffusion arrays are 4' x 4' with 2' x 4' of sonex in the middle.  Sure, I realize I am absorbing the lowest 18" of the rear wave, but that sound energy is highly unlikely to make it to my ear, give the heavy area rug, etc.  Once I get these D1 arrays mounted on boards (I hate using adhesive gunk on walls), I'll play around more.  I'd like to play with Skylines, but those are quite pricey.

Oh, and... I just got my 3.6s!    Even though I have to wait another 2 weeks for my Bryston amps, I can tell that they sound less lean than the MMGs... by FAR.  Maybe the treatments were doing the right thing, after all.

[Nils]

Well, 200-500 is going to be sucked up by pretty much everything - even the Sonex.  Are you sure this is the range you think you're missing?  Can you describe what parts of the music don't seem right to you?  Just trying to get a better handle on things to work through with you.

Bryan

Hi Bryan, it seemed like vocals were losing their weight and fullness.  As I just posted, I think it might've been the poor old MMGs.  Most of my system is changing at the moment, so I feel I can't critically evaluate anything at this point it time.   When things settle down, I'll let you know about my findings.

Thank you!
-- Nils

[samplesj]

I would definately lose the bass traps in the front corner floor.  I know the corners are perfect trapping locations, but with a dipole you are shooting right into them.  In my HT system I used them, but they weren't even considered in the Maggie system.
....

The 244s and tri-traps along the ground help out quite a bit in my acoustic space, I've found.  I am also using an ACI Titan II for the last few octaves, and the bass tightens up considerably with the combination of diagonal 244s + tri-traps.

I don't think I picked the right words.  I didn't actually mean remove the extra trapping from the room, but rather just put it somewhere else in the room.  It probably wouldn't matter because like Bryan said it looks like you've got a clean shot for most of the rearwave, but since you were talking about missing bass I just figured it couldn't hurt to move them.  But if its working now then why make changes.

Oh, and... I just got my 3.6s!    Even though I have to wait another 2 weeks for my Bryston amps, I can tell that they sound less lean than the MMGs... by FAR.  Maybe the treatments were doing the right thing, after all.

Enjoy.  Hopefully its not cold where you are.  When I first got my 3.6s they'd been out in the cold so long that it took around a day before they sounded right (too little mids or bass [ribbon warmed faster than the mylar?]).  I fired them up after an hour of them setting in place and had to just shut them back down they sounded so strange (very etched).

As long as you are careful I wouldn't worry about hurting them while you wait for the Bryston.  I've run mine with several different amps and believe it or not a 5 watt 300b was enough for lower level listening and caused no permanent harm.

Play with them as is for a while to get a feel for their sound, but eventually build/buy (Mye) some better stands.

Turn that sub off .   Seriously listen for a few days without it before you decide you still need it.

[bpape]

The Titan is a nice little sub.  I would agree though that at most, I'd use it from maybe 40hz or so down unless having the flexibitliy of moving it around helps smooth response.  The 3.6's will do surprisingly well with a bit of in-room gain.

One thing you might consider is to take the 244's that are straddling the wall/floor boundary and hang them up high straddling the wall/wall corner in the front of the room.  That'll let you move one of the diffusors down a bit.  A little space between the diffusors will help a bit.  I'd put them right behind the speakers.  One pair I'd also potentially put up high on the front wall or up high on the rear wall if there is space there.

Bryan

[Jason Jones]

The Tri's laid on the ground like that should still allow good spherical bass radiation from the Maggies with no issues.

The Monsters on the rear are there specifically to help with killing the bounce off the back wall that will cause the null based on the distance from ears to rear wall/speakers to ears. 

I will agree that a potential slight seat move might help the situation.  Sometimes when you kill one issue, another that was being cancelled by the one you just killed pops up. 

Bryan

I agree with Bryan on this. As for the diffusers, all the fun and exciting fancy pants math only applies to about 500 Hz and up (565 is their design frequency). In the 200-500 Hz frequency range the way to think of the diffusers is that each diffuser is a "well" of a bigger diffuser.

So if you want to try and use the diffusers for low frequency issues, you certainly can. The way that you would do that is by setting up your columns up in a pseudorandom sequence. I would probably recommend using a Barker Code Sequence. Some barker code sequences are here: http://en.wikipedia.org/wiki/Barker_code

The problem with this for a your set-up is that these sequences may not be best for your mid and high frequencies which seem to be working really well. Though, BTW this is a good use of the sidewall area behind you in general.

But, playing around with the diffusers and their spacing from one another (while keeping symmetry for the mid-highs)  may help with this low frequency issue.

Jason

[Nils]

The Titan is a nice little sub.  I would agree though that at most, I'd use it from maybe 40hz or so down unless having the flexibitliy of moving it around helps smooth response.  The 3.6's will do surprisingly well with a bit of in-room gain.

I have it crossed over right about where you recommend.  I love Maggie bass.

One thing you might consider is to take the 244's that are straddling the wall/floor boundary and hang them up high straddling the wall/wall corner in the front of the room.  That'll let you move one of the diffusors down a bit.  A little space between the diffusors will help a bit.  I'd put them right behind the speakers.  One pair I'd also potentially put up high on the front wall or up high on the rear wall if there is space there.

Bryan

When you say "space between the diffusors", do you mean horizontal space or vertical space?  The pictures I've seen of people with other diffusors (e.g. QRD704s and Skylines) shows no spacing between them.  Is the spacing recommendation due to the GIK D1's design?

Thanks again, Bryan!
-- Nils

[bpape]

Spacing both ways can help and I suspect that a difference in spacing horizontally vs vertically will also broaden the effect.  Actually Jason designed them so he would be THE source to get the best answers.  I know what they do and how they function and how they're different from other diffusors.  However, he's spent a LOT more time playing with them and that experience is priceless.

Bryan

[Jason Jones]

When you say "space between the diffusors", do you mean horizontal space or vertical space?  The pictures I've seen of people with other diffusors (e.g. QRD704s and Skylines) shows no spacing between them.  Is the spacing recommendation due to the GIK D1's design?

Thanks again, Bryan!
-- Nils

I am not sure that I want to blame equipment (it is not usually a MAJOR problem), but those speaks can be touchy and tough to drive. Your new speaks and a beefy amp may help quite a bit. But, aside from that:

1) Your current problem is  due to a lack of control of the lower frequencies in your room. You need more a more diffuse bass response. A more diffuse bass response means that you can walk around your room and you don't hear peaks and valleys. If you put on a sustained tone - like from Ethan's bass test disc - and walk around you will be amazed how uneven it is.

     a) Unfortunately it is not going to be perfect in that size room. So you have three options:
          i. Play around with your seating location. Often a small move can get you to a spot with a more flat frequency response.
          ii. More bass trapping. I know, you are probably thinking, "I need more bass. I can't afford to trap the little I already have!". This will help flatten your response and actually increase the "percieved" bass due to a lack of cancellations.
          iii. Use diffusion to help even things out.

I will leave options i and ii to Bryan's able hands. As for the diffusers:

Diffusers are mostly used with ONLY mid-high frequencies in mind. When they are all tightly spaced, as in most set-ups that you see pictures of they, that is all you get. To have a diffuser effective down in the 200-300 hz region, just from it's front wells, it would have to be a foot deep. At a foot deep, peaky absorption becomes a problem and your room gets pretty claustrophobic!

With a standard QRD or with the D1 you can get some extra performance down in the low-end by spacing them apart. As I mentioned before, think of each individual diffuser as a "well" of a bigger diffuser. A skyline will not work for this, you need the "tall" sides.

I am working on some graphic room layouts to show "ideal" usage. But for now we'll assume we are just optimizing your current "stuff" for the sweet spot.

Try setting up the diffusers with 6" to a foot between them. Try spaces vertically and horizontally. I can't really tell you exactly the optimum placement, too many variables I don't know about your pad.

Hope that is coherant. I am on vacation and my wife is giving me the evil eye - no time for spellcheck. I'll check back tonight to see if you have any further questions.

Jason

BTW, I would optimize your seating position before playing with the diffusers.

[Glenn K]

 

 

Hope that is coherant. I am on vacation and my wife is giving me the evil eye - no time for spellcheck. I'll check back tonight to see if you have any further questions.

 

Do what I do, throw her your credit card and hours will pass before you see her again!!!   

[Nils]

Thank you for all your input!  Bryan, I'd like to do the 244 wall-ceiling straddle mounting, but I'm a little nervous about having two giant panels hanging above all my shiny equipment.  I hope I'm not the only one who feels this way about 25-pound panels hanging from the ceiling. 

-- Nils

[bpape]

Actually, I was thinking more of hanging them vertically straddling the wall/wall corner but up where the walls meet the ceiling. 

Bryan

[Nils]

Actually, I was thinking more of hanging them vertically straddling the wall/wall corner but up where the walls meet the ceiling. 

Bryan

Hi Bryan, wouldn't that absorb quite a bit of the Maggie rear wave?  I tried placing the tri-traps vertically in the wall-wall corner (which I suppose would be a similar treatment), but I wasn't a fan of the resulting sound.

-- Nils

[bpape]

Actually not as much as you think.  You have enough space above that it will only be hitting just the edge of the speaker and only the top couple of feet.  When you had the Tri's stood up, you were catching the bottom 4'.  This orientation still leaves the middle and ear level of the speaker free and open.

Bryan