Building Infinite Baffle Boxes

[radiolee]

Hello one and all!!

This is my first post and I would like to say I am delighted to find this forum as I am an avid collector of vintage audio and do most of my listening on Altec A-7's.

I look forward to corresponding with all of you!

I have dealt with Bill at GPA on several occasions and consider him THE BEST. (Hi Bill, it's Lee from New Castle.)

On to my question- I will be building a new audio room from scratch and want to build large infinite baffle boxes into the front corners to house some 604D's.

Does anyone here have any experience with building similar enclosures?

Also, is there any info on same on the web that I may not have uncovered yet?

Again, it's great to find this board and I look forward to talking to all of you!

Peace

Lee

[radiolee]

Hi Roland
Thanks for the reply.

Here's a reply I posted on the DIY Audio forum that's gives you an idea of what I'm contemplating--
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This topic is very timely for me as I will be constructing a room shortly that will hopefully be "sonically correct" (to coin a phrase).

My basic aim will be to have as few parallel surfaces as possible.

It will have a cathedral ceiling, thus eliminating the vertical.

I will be building large infinite baffle boxes, basically closets, in the front corners that will angle out at about twenty degrees. These will hold my Altec 604's.

The side walls will have built in shelving that tapers in toward the front of the room. This will eliminate parallel surfaces on the sides.

The rear wall will be something af a challenge. I am thinking of a floor standing cabinet with a slanted front and a bow window on top of that.

This should eliminate most parallel surfaces.

I have heard audio in such a room and the difference is amazing.

The room is definitely the most under addressed element in an audio system, in my opinion. This is probably due to a hesitancy to build slanting walls or cabinetry.

Lee

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Since my room will probobly not have attic space above, I may go with the "closet" concept.

That is a terrific idea, though, to utilize the attic.

My latest thought on the side walls is to build regular bookshelves,for books, vinyl,etc., but hinge them on one side so that they can be swung out when doing serious listening to eliminate those parallel surfaces.

I am also now thinking of using a thick curtain material on the back wall to deaden the reflected sound.

If I can find two more 604's I'll have five and can do a surround thing. All tube amps, of course.

Ciao!

Lee

[rolandr]

Lee you hit the nail on the head. Refer to Jim D question to Roland on these pages. There the benefits of true infinite baffles are discussed
in more detail. In summary the benefits are the bass is flat and smooth to cone resonance without the boomy exagerated bass of bass reflex enclosures, without bulky floor occupying cabinets and without having to worry about Thiele and Small parameters. The only problem is having infinite baffles available in your sound room. In other words having an attic, a basement, a closet, a wall someway of dissipating the rear wave into the large space. These are true infinite baffles. For the altec duplex series it is particularly easy if you have an attic. In the upper corners of your sound room in the ceiling build small enclosures just barely bigger than your driver the upper part of the enclosure along with the ceiling sheetrock is removed thereby dissipating the rear wave into the infinite baffle of the attic. The enclosures can be built with a slight tilt medially and downward to focus the sound on your listening sweet spot. Reinforce the attic near the enclosure as needed to prevent any vibrations and use some 2" fiberglass in at least the back, one side and bottom of the enclosure. This method makes the easiest to built best performing low freqency enclosure I know of. If you use the 515 or 416 in the above enclosure and attach the 811 or 511 horn underneath you will get deeper bass than in the A7 or A5 cabinets without the massive 825 enclosures.

If you are seriously considering a dedicated surround sound audiovisual room consider sloping the border, the perimeter of the ceiling downward cathedral style. Placing 604s in the front side and back of this sharply sloped cathedral modification of the ceiling border gives the best sound without floor occupying bulky enclosures. Remember the "Best enclosure is none" and WAF (wife acceptance factor) is excellent