Which Theile parameters are most important

[Mikie]

I'm using mainly cornwall components on my custom center. To keep the box height down I intend to replace the 15" woofer with 2 8" or 10" woofers. I'd like to keep costs down by reusing the cornwall crossover, squawker, & tweeter. When evaluating new woofer drivers which Theile parameters are most important & need to approximate the cornwall?

[WMcD]

I only dabble in T-S in vented boxes. I'm mostly a bass horn guy.

It is a noble project. Keeping the mid and tweeter and crossover is indeed a good idea.

Basically, it seems your aim is to make a smaller cabinet with smaller bass drivers while still keeping the quality of the Cornwall bass response.

One thing working in your favor is that HT receivers will allow the center channel to only reproduce down to 70 Hz.

So you'll have to find a computer program which will allow you to model various small bass drivers with two in the box. The CW is vented and has a "Butterworth" alignment.

Last I saw, Madisound will sell you some smaller bass drivers and supply advice on box size, vents, etc. There may well be a small fee. This might be the most painless way to go.

Best,

Gil

[Mikie]

Thanks Gil,

Yes, spousel acceptance requires a center that is short and wide. I won't get anything over 14 inches tall approved.

I wasn't aware that HT receivers limit the center to <70 Hz. This should make it alot easier to design an acceptable enclosure. Is this a restriction of the receiver, or is it typically the crossover point for a sub?

[Deang]

They're all important. The more you know about the drivers -- the better the chance you'll be successful. I like to build things -- but my math skills are suspect. So, I use this stuff:

http://www.carstereo.com/help2/Articles.cfm

http://www.lalena.com/audio/

http://www.termpro.com/articles/xover2.html

http://sound.westhost.com/lr-passive.htm

"I wasn't aware that HT receivers limit the center to <70 Hz. This should make it alot easier to design an acceptable enclosure. Is this a restriction of the receiver, or is it typically the crossover point for a sub?"

80Hz is the typical crossover for a sub (THX standard). Check your manual, you may be able to run your center full range.

[formica]

Lets put it this way... the TS parameters of K33 used by Klipsch varied over the years but they were used pretty interchangeably.

In the Cornwall, the K33 was crossed over at 600Hz and rolled of pretty steeply below 40Hz. These had a Re of 3.5ohms and efficiency of 94.5 to 96dB/2.83V. This is a relatively easy frequency range for many pro style woofers... where you can group a pair of 8ohm speakers (wired in parallel to 4ohms nominal) with a similar combined efficiency.

Later...

Rob

PS: a very popular Bass Enclosure modeling software in WinISD... which works well esp given it's freeware.

[Mikie]

Many thanks, this is in line with my thinking. My goal is to select a pair of 8" or 10" woofers with an Re and SPL close to the K33. Other parameters seem like they could be accomodated by enclosure design.

I've been using WinISD, so it's good to hear that it's an OK tool.