Cheap DIY three way, Separate bass chamber?

Hello all,

I'm putting together a very cheap pair of 3' floorstanding speakers with some parts I have on hand (10" car woofers and midbass/tweeter drivers cannibalized from some nicer quality bookshelves) to use at parties and such. I'm spending less than 50$ on this project (mainly MDF) as I have everything on hand, and I'm not looking to spend any more :)

My question, though, is whether I should have a separate chamber for the bass woofers. The 10" woofers achieve a Qtc of around 0.69 in a sealed config such as this, and in 12x12" boxes had no issues hitting 31hz with only a -2db dropoff (though it was much steeper under 30hz).

I see most loudspeakers utilize a single chamber for all three drivers, rarely do I see compartmentalized designs such as this - so I'm wondering if there's a distinct disadvantage to it.

I'm open to opinions, but in the diagram below, red MDF divider between the bass and midbass/high chambers?

Schematic_zps69e0e930.jpg


I'm also still arguing with myself if I want to port the top chamber and tune it for midbass to take some strain off the woofer, but that's a subject for another thread :)

Cheers!
 
Yes, you should have a separate chamber for each driver.
If you do not have separate chambers, the drivers will interact.
Usually, the tweeter is sealed, so you do not have to do anything.
My recommendation is to never port a mid-range driver.
The reason is that excursion rises below port tuning, where a sealed box protects the driver from over excursion.
IMHO, its simply not worth the trade-off.

HTH

Doug
 
Excellent. Thanks Doug.

That's exactly what I thought. I'm not sure why many three way speakers schematics show bracing pieces between the drivers, but not separate air-tight chambers.

And they're not actually mid-bass drivers per-se, they're "mid range" (100hz-~6000hz) drivers stolen from a pair of ported bookshelves, which have the same volume as the top chamber will, so I was thinking of even using the same fluted port from the bookshelves...

But I like your reasoning. I'll build them sealed, and see how that sounds. I can always port, or de-port them after :)

Cheers!
 
Hi, where are you going to put the port(s) ? :p:eek:
It's better on the back.
What about different positioning of the drivers ?
It can be woofer on top, tweeter in the middle and midrange below
or if you like woofer on the bottom, invert tw and mid.
I suggest to put the tw outside, as it doesn't need a box, dunno if it
worth a baffle ...:rolleyes:
Also the mid can be just fixed on the baffle only, with no box ( just some acoustic absorber like pillow stuffing )
 
Yeah, the setup is going to be


Midrange
TW
______
Woofer


It would be back ported, simply due to space. I'd like to keep the woofer low to keep the damn things from being top heavy.

I'm actually considering trying to do an open baffle type design for the mid chamber and just stuffing it with some loose blackhole.