But where there are discrete notes, as in classical guitar, the octave from about middle "C", 360 to 622Hz seems 'muffled' somehow.
There is the same distinct sound of finger on string heard above and below but the 'ring' is missing.

I no longer have my freq. resp. graph that came with the Deltas.
Is there a dip there?
If so, some way to compensate?
Will the Theatre Pros improve on this?
Am I deaf in the mid-range?

Honestly, I don't hear any problems in this range from Theater Series four π Speakers. The truth is that I've been building and shipping a lot of these lately, so I have many chances to listen to them at various volume levels and with many different kinds of music. Just the other day, I listened to Rick Wakeman pound the keys on the song Awaken, and the album, "The six wives of Henry VIII" on Theater fours. Awesome! Certainly no weakness in the octave above or below middle C to my ears. Very pure and strong there, to tell the truth, but not peaky or overpowering.

I've listened to 'em at length with music from Beethoven to hard rock like Limp Bizkit and Tool, from Sarah McLachlan's pure voice to Roy Orbison's, the Stray Cats 50's style stand up bass to Steve Howe on acoustic guitar in the 70's art-rock band, Yes. Recently, I even cranked up a pair to full power and watched the movie Matrix, start to finish. That's a treat that will bring beads of sweat to your forehead from emotional energy!

Here's the response graph of the Delta 15:

Delta 15 frequency response; Used in Theater Series four π Speaker

As you can see, there is no dip in the midrange response of this speaker. From 100Hz to 800Hz, they're ruler flat. And if you have wired in the crossover circuit as shown, I don't think you are having problems with an underdamped filter or anything like that. The crossover is pretty well thought out, and the cabinet configuration is not one that is vulnerable to midrange anomalies so I expect your system's performance is probably pretty good.

You might check your cabinet, make sure it is well braced, so no panel vibration. And also make sure you have insulation as described in the plans. If you've tried alternate forms of insulation material like some do, try going with the R11 on the back, side and bottom. Put a sheet across the cross-section brace. This damps standing waves very well but without it, you might have some problems.

I'm running Pi 7's at home and have a weak mid/treble.

I figure it's because I'm not using a standard horn on the tweeter. Are you using standard components all over, or are there some places where you've "optimized" things? (not that any of us would ever do something like that... ;->)

In my case I'm looking to back towards the "normal" horns soon.

Grant.

message to Wayne: You should replace your computer renderings with some real images of all of your speakers. I think it would help peopel get an idea of what your speakers are like. Maybe show some pictures of them in setting in a listening room and/or in a P.A. application.

Adam

Also, the drivers are listed on the Pi website, but where can I get the horn ?

Thanks alot...
Tom Ottman
Berlin, Ct

Kevin

Thanks for the Peavey Horn info.

Did you get your plans from Wayne ? Or did you design the cabinet yourself?

Tom