Dual Chamber Speaker Box

[kelticwizard]

Mikee:

I don't know that the bass is really any smoother in a Double Chamber Reflex than in a conventional reflex, (ported). In fact, I have read that there is some small interference between the ports that might make the bass of the Double Chamber reflex slightly worse. Whether this is audible, I do not know.

But the big benefit of the Double Chamber Reflex is that it cuts down even more on the Intermodulation Distortion in the midrange. And as you pointed out, distortion up there is much more audible than distortion in the bass.

It is all well and good to take distortion measurements at 1 Watt. But if your woofer is going to carry both the bass and midrange, what do you think is happening to the delicate female voices while the woofer that carries them is going back and forth 1/8" or more, in order to produce the bass frequencies even at moderate power levels? Not pretty. After all, bass requires a lot of air to be moved-the midrnge frequencies significantly less so.

The more the cone must move to produce bass, the more the midrange suffers from Intermodulation Distortion. There is no way around that, assuming the bass driver is carrying the midrange.

I would go so far as to say that building a two way Double Chamber Reflex is akin to building a three way speaker with the bass driver of the 3 way crossing over two octaves above the port frequency. In other words, a 3 way with crossovers at 160 Hz and 2500 Hz is equivalent to a Double Chamber Reflex with a crossover of 2500 Hz. The only differences, I would think, would be slightly more distortion in the 40 Hz to 60 Hz range and less dispersion in the midrange, since the 3 way is likely to use a midrange driver smaller in diameter than the bass driver.

Again, I have neither heard nor measured the Double Chamber Reflex. However, the formulas for excursion/IM distortion would indicate that is how it works.

[mikee12345]

It is all well and good to take distortion measurements at 1 Watt. But if your woofer is going to carry both the bass and midrange, what do you think is happening to the delicate female voices while the woofer that carries them is going back and forth 1/8" or more, in order to produce the bass frequencies even at moderate power levels? After all, bass requires a lot of air to be moved-the midrnge frequencies significantly less so. Not pretty.

yep my jbl is measured at 60watts in ten cubic foot sealed -<1%

probably my amp wil be about 0.5% anywys at moderate power-but i must try a bandpass sometime because they are different :P

..basshorn for jbl first..

[kelticwizard]

Originally posted by mikee12345


yep my jbl is measured at 60watts in ten cubic foot sealed -&lt;1%

probably my amp wil be about 0.5% anywys at moderate power-but i must try a bandpass sometime because they are different :P

Is that 1% figure for Harmonic Distortion or Intermodulation distortion? I would guess the only way to measure Intermodulation Distortion would be the way Paul Klipsch did-running two or more specific tones through a speaker and see the how large the distortion frequencies are. That test is rarely performed.

by mikee
..basshorn for jbl first..

And why do basshorns sound so exquisite even though the reflex has a deeper cutoff per cubic foot of enclosure? Because the horn suppresses cone excursion even more than the reflex enclosure does. I love the sound of basshorns, even with their higher cutoffs.

bass horns

[jackinnj]

a double chamber, small transmission line:
http://tech-diy.com/LS_Articles.htm

[kelticwizard]

Thanks, Jack. I have been interested in Dalines for some time.

Here is another thread that deals with Dalines. The subject was discussed from Post # 19 on.
Dual Woofer TL?

[claudio]

Kelticwizard:

I am using a Focal 7k4412 and a ATD 135 ribbon tweeter.
The cabinet is unfinished cause my intentions are to test it in ported way, then DCR, then try with the tweeter mounted on the top of the box in phase with the woofer( I already made a different front panel to switch with the one you see in the pic).
It's a lot of work and a lot of time, and till now they are just playing with no damping in opposed phase: imagine the sound!

What I believe DCR helps a lot is in diminishing standing waves in tall tower cabinet, like mine. Some impedence measures will tell me if it is the right way to go.

Claudio