[Saurav]

Hi,

First post here, and you seem like a really helpful bunch of guys. So here I am with my problem I have a really small and nearly square room - about 12'x14' or so. The ceiling is vaulted a little in the middle, so at least it's not a near-cube. My subwoofer is in the garage, it won't fit in this room. My current woofers go down to about 50-60Hz, I'll probably replace the drivers and get some that go down to 40Hz or so, and then the 35Hz room mode will kick in and extend response some more

I know that bass modes are the biggest problem in a small room, but right now I think my bass situation isn't too bad, mostly because my speakers don't go low at all. However, my midrange drivers are on open baffles, and they are pretty close to the front and side walls. Also, my listening chair is very close to the back wall. So I'm thinking that the first thing I should tackle is reflections, and specifically, the back wave from the dipoles. I think I'm hearing the effects of the reflections, the primary ones being vague / shifting imaging and a shallow soundstage. This is compared to the same system in my previous place, where it was in a much larger room. But this room is a listening room, so I can put up treatments without upsetting my wife.

So the first question is, does that make sense? Because if the answer is no, then I should go back to looking at fibreglass bass traps. So... moving on, assuming it makes sense to tackle the dipole back wave first. The speakers are dipole from 500Hz to 3500Hz, there's a ribbon tweeter above that. So any absorption/diffusion I need is only down to about 500Hz. And I like the 'dipole sound', I prefer the 'surrounded by sound' feeling over the pinpoint imaging that monopoles seem to do well.

So my initial thoughts are, I think I need mostly diffusion behind the speakers. Both on the front wall, and the side walls behind the speakers - basically, in both corners. And probably absorption on the side walls in the first reflection points, because the tweeter will be lighting those up. The speakers are toed in quite a bit, so the dipole null almost points at the first sidewall reflection point, so the midrange shouldn't be sending too much energy there.

Does that make sense so far? If it does, does anyone have suggestions for DIY or commercial products? Since this is just down to 500Hz, does acoustic foam become a viable option instead of OC fibreglass? Also, I could DIY absorption panels with fibreglass, but DIY diffusors seem to be kinda complicated to make. And I saw these:

Auralex MetroFusor

Auralex DST-R-Fusor

HSF Acoustics

That's not an unreasonable aount of money, and it's about the amount of coverage I think I'd need. I'd probably rule out the 2nd one, a 1" thick diffusor probably won't work down to 500Hz. Does anyone have any knowledge and/or experience with these products? Or anything similar? Are there any simple DIY options?

Thanks in advance,
Saurav

[ctviggen]

I've also been toying with diffusers, though I've not purchased any.  Here's another website:

http://truesoundcontrol.com/products/TFUSOR.html

You can also fill this product (which they say will lead to better broadband diffusion; is that really true?  I thought the outside of the product defined the diffusion; you might get better absoption, but not diffusion).

[Saurav]

Yeah, I've seen that one too, but that's significantly more expensive. I'd guess it's more effective too. You said you've been toying with diffusors but haven't purchased any... does that mean you've built them?

[TheChairGuy]

Saurav,

Welcome to AC, my man.

I've had rooms of this (more or less) 12 x 14' size as listening rooms for the past 6 years and finally realized, despite my best efforts with sound absorption, a small room can't handle and integrate bass cleanly any way it is dispersed.  

My planar dipoles (Maggie MMG's) have a -3db cutoff at 50Hz....I miss some music below that, but everything above that point is wonderful.

Books and bookshelves are an elegant way to absorb those natty mid reflections you are getting, too.  Too much behind kills the aural presence of dipoles, tho.

Now, that I gave up and looked more realistically at my room config, I sold my subs, and other speakers that didn't work in here (Vandy 1c's with a 3db cut at 38Hz overwhelmed the room, too). I kept my neat little Linaeum Tower, with it's dipole tweeter, as it extends only to the mid-50's.

There's no basements in this part of California and my main rig ain't going into the large living room (by order and decree of the sheriff 'round these parts   ), so I make do in my small-ish space.

You can't put lipstick on a pig - I finally made peace with that and have a few more bucks in my bank account with it's knowledge.

[ctviggen]

No, I've been toying buying them (building them would be too hard -- they're formed from primitive root sequences and the like).  I'm just not sure whether to implement diffusion with absorption (I already have 6 Real Traps), where to physically place the diffusion, and how to measure its effects.  For instance, with ETF (a program), I can easily measure absorption, but I'm not sure how I could measure diffusion.   And, it's not clear to me what benefit diffusion provides.  Thus, I was going to experiment with diffusion to see if I feel its effects are justified.

[John Casler]

Hi Saurav,

Welcome to AC.

I'm not sure I understand the positioning of everything.

And I have a feeling the "close to the back wall" seating position is causing much of the problem.

Is the "null" of the dipole "in line" with your ear in the listening position?

How close to the back wall are the rear faces of the dipoles?

My suspicion is that these two elements might be causing some problems.

[Saurav]

Thanks for the welcome, guys.

TheChairGuy,

Yeah, I figured I would have to give up on the low bass. And it's a duplex, so I don't want the neighbors complaining either. So I guess you're saying that it makes sense to try and tackle the reflections.

ctviggen,

Thanks. If you do buy some products to try them out, I'd love to hear of your results. And yes, whether ETF will show any changes or not is an interesting question.

John,

> And I have a feeling the "close to the back wall" seating position is causing much of the problem.

Quite likely. My head is probably < 1' from the back wall. But I'm not sure I can move the chair out further, that puts me really close to the speakers.

> Is the "null" of the dipole "in line" with your ear in the listening position?

No, the null is pointed towards the first reflection point on the side walls.

> How close to the back wall are the rear faces of the dipoles?

Hmm... 2 - 2.5'? Something like that. The distance from the side walls is in the same ballpark. I can measure them tonight. I tried a variation of the 'Cardas' positioning advice, where I took the woofer's distance to floor/front wall/side wall and tried to get those in a 1:5:8 or 5:8:13 ratio. I think that helped even out the bass a little bit, but since I don't have much bass now, I can't really tell. I also don't remember if my speakers are still in that position or not

[John Casler]

John,

> And I have a feeling the "close to the back wall" seating position is causing much of the problem.

Quite likely. My head is probably < 1' from the back wall. But I'm not sure I can move the chair out further, that puts me really close to the speakers.

..

If you treat the wall behind you suffiicently, you might be able to get the mids and highs OK, but the bass might still be tough to qwell.

> Is the "null" of the dipole "in line" with your ear in the listening position?

No, the null is pointed towards the first reflection point on the side walls.

That, in itself may also be negatively impacting what you are hearing.

I know this may sound like a strange suggesstion, but you might try placing the dipoles so that the null is exactly facing the ear in the listening position, BUT...since that would be way too close to the rear wall, set them to fire UP and DOWN.  I know it sounds crazy, but it would be far better than receiving "direct" from one face as you are now.

> How close to the back wall are the rear faces of the dipoles?

Hmm... 2 - 2.5'? Something like that. The distance from the side walls is in the same ballpark. I can measure them tonight. I tried a variation of the 'Cardas' positioning advice, where I took the woofer's distance to floor/front wall/side wall and tried to get those in a 1:5:8 or 5:8:13 ratio. I think that helped even out the bass a little bit, but since I don't have much bass now, I can't really tell. I also don't remember if my speakers are still in that position or not

Confused about what you mean by "The distance from the side walls is in the same ballpark".  

Aren't the dipoles mounted on the side walls?

[Saurav]

OK, now I see the confusion I couldn't figure out what you meant by pointing the null at the listener.

Here's what my speakers look like:



The upper baffles are open in the back, so the speakers form a dipole because the back wave cancels the front wave.

[John Casler]

     

What a dummy I am

I hear dipoles and I immediatly think HT.

So sorry.

I can't say I am a big fan of dipoles, since they acheive their sonics by using room reflection and are without a doubtthe most finicky of speakers to set up.

I'm sure you have visited the Linkwitz site to see how he explains set up on his since yours are of a similar nature.

The "shifting images and soundstage depth are certainly set up and interaction issues of that type of speaker.

Hang a thick blanket behind each one and see if you can get any type of result.  If so, then absorbative room treatment behind the speaker will help.

I used to have Maggies, and the best they ever sounded, was when I had a full length floor to ceiling, thick velvet curtain behind and beside them.

Sorry about my being so dense.  Good Luck.

[youngho]

I believe John is referring to this: http://www.linkwitzlab.com/faq.htm#Q31

Also, I seem to recall that the designer of the Audio Physics loudspeakers used to argue for putting his loudspeakers *way* out into the room and the listener up against the rear wall. I think his argument was that the early reflections off the rear wall were less of a problem from a psychoacoustic standpoint that later ones, and the placement of the speakers tended to excite room modes less. But my memory could be faulty.

Young-Ho

[Saurav]

I think I read Linkwitz's website every two weeks, and every time I feel like I understand a little bit more. Or maybe I'm just fooling myself

John, that's cool. You had me confused for a bit there. I was thinking, OK, to point the nulls up and down, I'll have to lay the speakers on their sides. That can't be what he means, can it?

I've tried rugs on the walls behind the speakers to see if absorption would work. I think the rugs had too tight of a weave though, they didn't really do much. I'll try blankets if I can steal some without my wife noticing