isobaric sub with scanspeak 25W8565-00

[aaronboumans]

hi there
I'm looking for a isobaric design with two 25W8565-00 's
There were some but websites are down....
Can anybody help in some way?
thanks

[Brett]

It's not much use as a sub; the driver only has 6.5mm of Xmax. Sealed isobaric for Q=0.707 is 52L net, F3 is 35Hz and it runs out of Xmax with 100W/driver at 65Hz.

Ported is even worse in terms of excursion, but has a nice FR. I tried a couple of different volumes but 110L was about the best.

I'd use something different for a sub.

[aaronboumans]

thanks Brett
but are those graphs for an isobaric design or just two 25w's in a cabinet?

[Brett]

Isobaric

[aaronboumans]

ok! hmm...
not looking that bright indeed.
Maybe I should rethink this project? But I already have those two 25w's.
What else to do with them?

[Brett]

Sell them and use the money to buy useful drivers.

[aaronboumans]

BTW, how is it that you calculated 110L. I thought that one should take half of the 'normal' volume for a single driver. I calculated 120L for one unit so shouldn't an isobaric design be around 60ltr?
What did I mis(understand)?
And what are useful drivers?

[Brett]

I tried lots of things, but first I calced a std 4th order tune for a solo driver and got something like 250L, so I halved it. Didn't look any better larger or smaller and going for a small box ported with a low tune doesn't often work as the port becomes too long if you want decently low airspeed.

Try dedicated sub drivers like those from Acoustic Elegance, Exodus, CSS, Fi, Audiopulse etc.

[aaronboumans]

Thanks Brett very helpfull
Now you make me do it again! buying more speakers