Stupid CTC spacing question

[hulan]

Stupid question:
On an MMTMM, do I measure the CTC spacing from the tweeter to the nearest woofer, or from the tweeter to the woofer furthest out if all the woofers are crossed at the same frequency?
Sorry about the wording, hope my question makes sense.

[zach_t]

If all woofers have the same crossover, then from the farthest woofer. What is common is for the "outer" woofers to have a low crossover frequency fall off first and the inner woofers crossover over to the tweeter.

[hulan]

> If all woofers have the same crossover, then
> from the farthest woofer. What is common is
> for the "outer" woofers to have a
> low crossover frequency fall off first and
> the inner woofers crossover over to the
> tweeter.

Thanks, that's what I was attempting first, but thought I might be able to get away with something a little simpler. I'll have to go with a tweeter I can cross lower.
Thanks.

[hulan]

Maybe I'll just rebuild the boxes and go with a standard MTM. I like having left over parts, anyway.

When I put the drivers in the boxes and ran the woofers full range, it was pretty flat out to the breakup. So in the current boxes, I can't use the outer woofs for baffle step like I would have liked to. I don't know what went wrong in the modeling, but oh well. That's why we build and test, right?

[paul_n_oneal]

I start with driver selection first, then model the box, then build the box, then mount the drivers and measure each individual driver and then model and design the crossover. Then listen and model and change about 100 times until I think it sounds right.

[cjd]

Go 2.5 way. Better control, less misery...

C

[georgew]

> Thanks, that's what I was attempting first,
> but thought I might be able to get away with
> something a little simpler. I'll have to go
> with a tweeter I can cross lower.
> Thanks.

My understanding is that in a WWTWW setup, the size of the two woofers can be combined to calculate the spacing. For example if you were using 4" woofers, you would calculate for an 8" WTW arrangement, also adjusting for any spaces between the 5 drivers. This would call for a tweeter that could cross lower, but should work. Am I wrong in this assumption?

[hulan]

> I start with driver selection first, then
> model the box, then build the box, then
> mount the drivers and measure each
> individual driver and then model and design
> the crossover. Then listen and model and
> change about 100 times until I think it
> sounds right.

Just out of curiosity, how do you do that? Do you plug the holes for the other drivers and mount one, then measure? How is that affected by the ports? I ask because I'm always game for trying other folks ways of doing things. I think it helps us refine our own processes by learning from others.