And yet another trans lam for a friend.

[R-Carpenter]

Well well well. The question is: translam or not translam? Not really, I've been waiting for an opportunity to do a full size 3-way translam speaker and here it is. A friend of mine listened to some of my designs and after an hour or so decided to dump his small Sonus Faber on his cousin and splurge for some real good drivers. I said oki doki, I'll build you a pair.
Here comes the ebay and DIY forums for some great pricing.
Just got a set of 4 SS 18w/8531G-00 Revelators.
Have a pair of 25w/8565-01 stored in the box
and finally a pair of Seas Excel T25cf-003

So I am thinking: acoustic suspension BMTM crossed over at about 350hz and 2800hz with electrical 2nd order.
The impedance of the 25w is pretty high at resonance so I am curious to see how the impedance compensation including this peak would affect the sound and perhaps make an amplifiers job less stressful. I am also going to create internal cavity in the loudspeakers walls and use a heavy filler, such as powdered glass or silicon-carbide may be binded with epoxy.
I am also thinking if I should get another pair of 25w so I wouldn't have to over complicate the crossover with BSC coil.
Any thoughts?

I measure with Sound Easy, Beringer console and microphone.

[R-Carpenter]

Stock of precut parts.

[R-Carpenter]

This is a result of a day and a half of work. I had an option of going to someone with CNC but chose to do it the old fashion way. Jig saw, band saw and a shaper. I did see this type of the internal anechoic chamber on Tony G web site and decided to over complicate things a bit. There are 3 semi random patterns stocked up internally. I will apply sound absorbing foam to each layer before glue up.
Figuring out internal volume is also a pain. I think I'll place each type of this segments on the flat surface, fill it up flat with sand and then measure the volume of sand in a measuring glass. Then do my math. My believe is that this enclosure will be very much dead internally.

[Shaun]

Nice! ...especially the inside surface.

Have you considered adding internal cross-bracing?
A tip: if you can still manage to do it, try to include some sort of alignment guide. IME, it is difficult to align all pieces simultaneously.


My lam project (WIP)

[R-Carpenter]

Thanks Shaun. How's your project going?
I am planing to include bracing later on, just haven't gotten to do it yet.
I think in addition I will make a vertical cross brace.
The other idea that's really tempting it to attach the driver to bracing. Orion ++ has the driver mounted on the bracket so perhaps I could somehow utilize this idea.

[Shaun]

My project runs in stops and starts. Mostly because I don't have a sheltered work area (it's winter here now). Due to some sections having slid out of alignment while gluing, I have lots of sanding/filling/plaining to do. My next best chance of getting going is the December holidays, so the translam project is on hold while I carry on with smaller projects.

The next translam project I do will definitely use plywood instead of MDF. I keep worrying about expansion and contraction of the MDF (will get it sealed thoroughly?).

Good luck with yours.

[Salas]

Those internal patterns need to be really big wedges, else it is just extra work. The absorption is going to do all there is to be done.

[R-Carpenter]

Well, there's a specific resonance for each material such as MDF or in this case HDF. There's also a volume specific resonance for the enclosure. While a specific resonance in a rectangular chamber without stuffing or an acoustical absorbent can go as high as 60 decibel I am curious to see how this chamber will react. The measurements will be posted later on.
Now, how and based on what there's a conclusion on the size of the wedges Salas?

[Salas]

Half wavelength of your longest cabinet mode. Based on acoustics. See an anechoic chamber for example.

[R-Carpenter]

OK, next question, how effective and at what frequencies your sound absorbent material work?
I have measured a few.
Also, you saying that a sound wave will be reflected from a flat surface such as MDF the same way compare to the broken down surface that I have here?