MCM 8" 55-2421 Isobaric

[ODougbo]

Pics of my 3rd front to back 55-2421 Isobaric box. A friend gave me a sheet of ½” MDF and I had one more pair of 55-2421, so couldn’t leave that combination sitting around.

½” is too light, so decided to build the box complete and then go back and “wrap” it with a second layer, lapping the joints and thickening the walls up to 1”.

The second ½” layer will be added today also I did use ¾” scrap for the tunnel.

As far as isobaric design, I’ve tried side by side speaker boxes - two speakers in one huge sealed cabinet - two speakers in ported box, on and on. I’ve gone back and isobaric mounted them, it does work better as far as low bass, rumble, and that sensation of power.

For another example, I took an old pair of 10” NTH woofers, (pretty old but in good shape,) again with a small tunnel and a box one half the size, the best bass ever. I wish I built them years ago

[ODougbo]

To follow up on this thread, attaching pic of finished box/design. The ½ over ½ MDF worked out well, a little more time/energy than I had planned, but glad I did it.


I have two of these in the back of the HT room, the bass is fantastic and loving it. The bass response is low, powerful and defined; I did find some 2" black foam “floor stands” to get them up off the floor a bit.

I connected them to two channels on a 5X200watt amp. and moved the rear speakers (shown left) to an older 100watt stereo amp. The 4ohm, MCM woofers are wired in series.


During the signal generator testing, there is noticeable bass enhancement down at 25hz, it rolls off pretty quickly after that (down to 20hz).

I like this project, somewhat easy to build, it works well and the costs are low. I also like that they sound great at low volumes; no need for "loud", bass enhancement, etc.


The 2 MCM woofers are $60 (sale price); I don’t think there is a single woofer out there for that amount that can do what this combination can achieve, if so, I would be curious what is out there that compares.

[epa]

nice finish ,
to bad they don't sell in europe.

[kornnylike]

I have two in a bassreflex and they sound great. Next build for the same driver bass horn

[ODougbo]

I’ve been watching your thread; and yes I may come over to the dark side. Any speaker project sounds good to me and I have 1 driver left on the bench. I was going to ask if you can take some shots during fabrication. I think I understand it, but pics would be great.

Originally Posted by kornnylike

I have two in a bassreflex and they sound great. Next build for the same driver bass horn

[ODougbo]

Truth be known, that was a three coats before lunch project. That’s a flat, water based paint by Valspar, but when sprayed it has a bit of sheen. Since it was MDF there’s another easy trick to fill the flat surfaces (most will shout no-way). I skim coated it with regular green lid drywall compound; probably the fastest way to fill everything at once. The “mud” was applied very, very “tight”; on a gray primer (1st) coat and then sanded lightly.

Originally Posted by epa

nice finish ,
to bad they don't sell in europe.

[kornnylike]

Originally Posted by ODougbo

I’ve been watching your thread; and yes I may come over to the dark side. Any speaker project sounds good to me and I have 1 driver left on the bench. I was going to ask if you can take some shots during fabrication. I think I understand it, but pics would be great.

Sure I wil. I have few Things to finalize before building start, if every thing goes well I will start next week.

[Djim]

Originally Posted by epa

nice finish , to bad they don't sell in europe.

Epa, these are relabelled TangBand's loudspeakers which are available in Europe. But it's complete "stierenstront" we have to pay around 80Euro's for the same driver...

[revboden]

wait... Djim can say that in Dutch but i can't say ******** in english. that's Bull Smeg...

[epa]

Originally Posted by Djim

Epa, these are relabelled TangBand's loudspeakers which are available in Europe. But it's complete "stierenstront" we have to pay around 80Euro's for the same driver...

well some relatives asked me to bild a ht subje(dus ik dacht lekker goedkoop)
but on the other hand i have plenty of other commitments right now,so ill put it in the fridge for now.