Non-ideal IB

[toecheese]

I'll soon have photos of an IB I helped a neighbor build from my old pair of Tempest 15s.

I told him that the pair weren't enough for a room his size. We decided for him that a manifold would be better for his setup, so I cut (with the jasper I bought for mine), a sheet of MDF with cutouts for 4 speakers, but only cut out for the two tempests (didn't cut the other two all the way out).

Over my (not loud enough) objections, he bought a single PE DVC to mate with the Tempests, and cut the board (it was too tall due to WAF :-( ) down so that it only has three drivers!

Non ideal:

Having a of a time figuring out how to wire three speakers (it can be done, but it isn't pretty).
Having a of time figuring out how to hook them up to the amp. Decided for the moment to use only one channel.
Turns out the DVC doesn't have the same impedance (it shows up as 6) compared to the 8s of the tempests.

Summary- use an even number of matched drivers. If you must (because like my case, the tempests were discontinued) buy more drivers, buy them in pairs so you can drive them from your own channel.

[Sonnie]

Looking forward to seeing some photos...

That wiring sounds like it may be a challenge.

[toecheese]

Ugh- it has been. First of all, I had to dust off my brain to remember how to calculate resistance for parallel circuits (R1*R1/(R1+R2) and series (just add them) and then come up with a combination that would give an impedance between 4 and 8 Ohms- where his amp would be happiest. Doing each dual-8-ohm VC in series (16 ohms), then making all of them parallel (another formula is 1/r=1/r1 + 1/r2 + 1/r3, I think; double-check the math), which gives me 5.7 or so.

Except that the PE Tempest clone measured at 6 Ohms. Now I may be running it on its own channel instead of getting a weird mixture of impedance on one channel (I am not entirely sure what would happen with one driver having a lower load than the others)

A bit of cleverness was buying a speaker terminal block so I could wire the speakers up in different configurations. Pics coming. Tomorrow maybe. And no making fun of my solder job.