Unity progress

[keto]

Hey all,

thanks to xcortes loaning me some cool measuring gadgets, I've made a few advances in my system.

The source is a TD-124 and a Panasonic Strain Gauge cart. Checking in with a CD player (maybe not the best reference) tells me that the high-pass shelf-filter in the Seduction (now without RIAA and with C4S battery-bias for the cartridge), is not quite enough and that I should go with a steeper slope.

For the mids, I've just ordered the parts for a speaker-level notch-filter @ around 4khz (0.22mH coil + 7uF cap + a resistor, all in parallel).

I've decided to go with a 220hz Marchand LR4 lowpass XM46, which will be "imbedded" in the Paramount chassis.

For the moment I've had to suspend experimenting with the BMS 4550 compression drivers, and have rewired the Tom Danley time-aligned passive filter for the B&C DE25s. They have a little dip at 4khz, but sound great.

At the moment, just the compression drivers (driven by a S.E.X. amp) and the big TDXs (driven by Paramounts) are in play.

I've enjoyed having all the measured info, which gives me a kind of step-by-step path forward.

Any suggestions on all this would be most welcome.

--Tom Jones

[John Roman]

Wow, Is the TDX a bass driver only. Or rather what frequency range is it handling? What volume cabinet are the TDX's using or perhaps their open baffle? Really interesting stuff. Marchard is an active filter , correct?  I'm currently exploring an open baffle carrying the mids and tweets on top of a 15" paper cone driver crossed at 250 hz passively in a ported bin at 4.7 cu ft. When you say it sounds good could you elaborate. John

[keto]

The TDX's are handling everything up to 300hz, with 2nd-order XM46 low-pass PLLXO's before the Paramounts. Next step will be to use 220hz 4th-order XM46's, to line up with the midranges' rolloff. The XM46's are passive (great!), but have an input Z of 1K (tricky! -- they will require a very special preamp).

The enclosures are 14 cu. ft. -- pretty much perfect for the TDX and the SET damping factor.

One nice thing about crossing over at 250hz (or 220hz) is that its possible to get the drivers' centers within 1/4 wavelength at crossover.

The compression driver (that sounds pretty good, or pretty "natural" to my ear) has a passive speaker level filter that a) produces a nice-looking rolloff and b) is designed to be "time-aligned", which I take to mean "of minimum phase shift" -- something that Danley has been developing extensively during the past decade (since mine were designed).

[earwaxxer]

Wow, 14 cu. ft! Those speakers must be VERY efficient with those compression drivers. Im guessing around 104db.  Interesting system.

I'm kind of on the brute force end of things with over 2KW of total system power. This hobby can take different forms!

[keto]

The TD15X's are about 95dB/1W/1m. So they would reach 104dB peaks with the Paramounts' 8W. They play louder than necessary with no visible cone motion.

[earwaxxer]

very cool! Well done!