FR125S/SDX7 2-way

[Timn8ter]

I've been working with the idea of an open-baffle full range mated with a BR woofer and came up with something that seems to work quite well.
This design uses the CSS FR125S on an OB with "wings" and the new CSS SDX7 woofer in a unique curve pipe/expansion chamber enclosure.

[Timn8ter]

I used Praxis to measure the T/S parameters of the SDX7 and came up with
Qe = .419
Qm = 2.42
Qt = .357
Fs = 33.8Hz
Vas = 29.7 L
Mms = 18.4g
Re = 6.1
BL = 7.55
Le = .75
Sd 131.8 cm^2
Xmax = 11.1 mm
SPL = 87.58 db
This led me to a total enclosure volume of 18 liter and a port size of 2" x 7.5" tuned to 38Hz.

[Timn8ter]

I decided to use a 4th order XO at about 750Hz and accepted a dip at the crossover frequency to try and minimize the effect of cancellation in the crossover range. This along with mounting the drivers close together seems to have helped. I also accepted the FR's peak at 7kHz. You can see the dip on the graph fairly easily. Neither of these anomolies are bothersome to me when listening.
The enjoyable part is the balanced sound from the mids on up rather than having a tweeter take over the upper ranges. It presents a more seamless presentation this way.

[Timn8ter]

Here are a couple of pictures of the back.

[Timn8ter]

This view shows my wiring scheme for the FR125S.

[Timn8ter]

The performance of the CSS SDX7 is almost startling in this arrangement.
Track 6 from the First Impression Music Audiophile Reference IV SACD is "Sometimes I Feel Like a Motherless Child" performed by Arne Domnerus on saxophone and Gustaf Sjokvist on a full size pipe organ recorded in the Spanga Church in Stockholm.
This track contains very low registers of the organ and this speaker plays them in a balanced manner with the rest of the music. Very impressive for a 2-way system.
The pipe behind the SDX7 is a 6" diameter plastic elbow pipe stuffed with polyester wool. The bass reflex box below it is empty except for the port tube and crossover.
The mid-range details are much improved with the FR125S being freed from the confines of a box and low frequency duties.

[planet10]

Thanx for that Tim... i've been playing with the SDX7 too, 14 litre sealed so far, quite amazing bottom with a 5 dB boost at 30 Hz (default on the plate i installed in the box). I have an aperiodic TL up next.

Try this. Run the pad of your finger over the cone. Now your fingernail. I can't help but think that you can hear that when the music is playing. I am on my 2nd prototype to see if i can make things better. Mail me if you'd like details (did you get my last "email")

dave

[CSS/XBL]

Tim,

Thanks for posting your project. We are certainly pleased with the performance of the SDX7 and we have some people who are now replacing their existing Extremis in 3 way designs.

Bob

[Cal Weldon]

Hi Tim,

Love the innovative chamber. Would like to hear those.

Originally posted by Bob Reimer
some people who are now replacing their existing Extremis

Uh-oh, I think I smell a road trip. Quit dangling those carrots in front of me Bob. You know I have no will power.

[Timn8ter]

Originally posted by Bob Reimer
Tim,

Thanks for posting your project. We are certainly pleased with the performance of the SDX7 and we have some people who are now replacing their existing Extremis in 3 way designs.

Bob

My HT speakers are 3-ways using 2 Extremis, a WR125S and a Hiquphon OWIII tweeter. Swapping out the Extremis with the SDX7 would make one very impressive floorstander. In fact, I would just use 1 SDX7 per side in a TL arrangement. That would be plenty.