Flush mounting surround system. (Front.)

Hello. I’m trying to flush mount my Dynaudio BM15A speakers. So far I have built a construction where all 3 front speakers are standing at 1.80m & properly angled & facing listening position at equal distance. The center speaker is almost touching the wall & .L & .R speakers are at about 1m (3foot?) from the wall. The room has massive bass traps in all corners & lot of insulation above the recessed acoustic ceiling. The center speaker has already quite linear response where .L & .R has a massive dip with the center at about 80Hz. I’m intending to fill the cavity behind the speakers with heavy pressed Rockwool, (to eliminate obvious canceling in bass frequency’s), but wonder if I should built a new back wall just behind the speakers? Will filling the cavity with insulation cure the problem or even so, the new wall (with insulation behind), is necessary?

Aloha and welcome to the forum, Would you be able to provide more information, please? - How have you built your "construction" - How is the rest of the room built? - Are you located on a slab? 2nd floor? Home? Warehouse? - What are your room dimensions - L x W x H? - At what height are your speakers positioned (woofer)? Could you post some pics? It would be helpful to see what you're describing. Aloha 8)

The studio is located at a separate building. The control room is about 6 x 7.5m with 3.30m to ceiling. Sorry for the poor camera pictures.

So the question is: Will filling the cavity with insulation cure the problem or even so, the new back wall (with insulation behind), is necessary? :cry:

Love your CD rack. Seems like it double-functions as a chair also. 8) How's your back wall treated? Just the bass traps in the corners, or is there more to it? Thanks for the pictures. One picture says more then a thousand words... Cheers, Sigert

:lol: Hah-hah, yeah, I was just going thru my samplings, finding 58 pcs, now obsolete sound libraries. I have for sure used thousands of hours to get them right, -than.. Modern times.. As you see back corners are “heavy” bass trapped, (the other corner is identical), -there is some diffusion on the back. Under the roof, all meeting corners are taken care of too.

You said you have a dip at 80Hz. Is this dip flanked by peaks at nearby frequencies? If this is the only frequency causing trouble, and the rest of the spectrum response of the room pleases you, you would probably want to leave the idea of adding more broadband treatment and start looking for tuned constructions. You still have some wall space left. :)

Sigert wrote:

You said you have a dip at 80Hz. Is this dip flanked by peaks at nearby frequencies? If this is the only frequency causing trouble, and the rest of the spectrum response of the room pleases you, you would probably want to leave the idea of adding more broadband treatment and start looking for tuned constructions. You still have some wall space left. :)

Thank you. :o Well, the distance from the front of the speakers to the back wall is about 95-105cm. This corresponds quite exactly to 320-350Hz. 1/4 wavelength of this is just there: 80-87Hz. My question is: does one have to built special (solid) box/wall for/behind the speakers or filling the whole corner with heavy insulation will do? I will still have space underneath for hangers, Heimholz or whatever. I’m quite sure that finishing "first floor" will get me very near quite nice frequency plot. :wink:

I don't think the distance between your speaker and the wall behind it causes the trouble. Is your room by chance about 4,35meters long?

kurtkurt wrote:

Will filling the cavity with insulation cure the problem?

Don't think you could do much harm with filling that cavity up. Depending on the seriousness of the problem, you might need to add range specific treatment afterwards.

Hello Sigert. The control room is about 6 x 7.5m with 3.30m to ceiling. The predicted cancelation dip at 1/4 of the wavelength, when the front of the loudspeaker is placed about 1m from the back wall says: cancelation dip at about 80-87Hz. It’s all in the standard papers. You are right that filling the cavity is not going to cure all of the problems but I have to finish construction now, & don’t know if building an extra wall will do any good. The loudspeakers are already placed in their boxes & if you look at the pictures, you will see to & from air ventilators, placed there because of the amps back on the speakers. I have just to mount flexible air duct channels on them. (I hope you understand what I mean.) I want to have it done now. Later on, I will for sure have to deal with fine-tuning, but that’s another story. Do you have any experience/opinion about the wall question? :wink: PS. Strange that nobody else have any opinion. Am I on the wrong forum? :cry:

Well, I'm not claiming any expertise in the field. I've only been studying it for bout six months or so. But at some point you gotta dive in, speak your mind and ...well... take the punches if you're mistaken I guess. The only way to learn the field. :lol: I lost track of the fact that your construction wasn't finished yet. I thought you'd done all the work, tested the setup and noticed a problem. Thought you had then tore apart your construction to show us the inside. The standard design you found on the forum worked for a lot of guys here so I see no reason why it shouldn't work for you. This does indeed mean filling up that cavity, with the exception of a narrow gap of air. Could you talk to me on the subject of predicting that dip? Sounds unfamiliar to me, so I'm intrigued... :D Cheers, Sigert

Hi. Well, I didn’t got the idea from here but would you be kind & point me toward the discussion? Thanx.:wink:

It's the basic design, common here on the forum. I think it's John's work. btw.. could you resize your picture above so we don't need to scroll all the time?

Thanx. Going to dinner.. :wink:

Thank you Sigert for helping me. Going to record/mix in 6-8 days a CD project from tomorrow. After that.. All the best.

This might have been better off in the speaker forum, but no matter - flush-mounting (soffits) should solve your problem, check the speaker forum (and Sigert's inclusion of side details) for the direction to go... Steve

I realize this is an old thread, but do you have any updates? I'm considering bm15a's for my control room, and would like to know how the flush mount worked out for you.