Probably idiotic how I've done it though I'm curious if there's an optimal way to do this that anyone has mastered? I observe the following -- more open less nasal aggressive sound. Reduction in level -- maybe 5-8db which I will try to measure at a later date. Not as pronounced an effect as open baffle woofers though still seemingly beneficial as it seems to do away with some cavity resonances from the cd inclosure which are otherwise reflected from the rear wall of the chamber, back into the diaphragm and through the horn. In other words it sounds more clean and effortless. Not certain if I will stick with this though I'm enjoying comparing the right and left sides which are standard and open for now, and will probably devise some sort of clamp if I do settle on the open cd version.
Yes, couldn't make it work despite the pros.
One of the real negatives was that off center the sound chamges much more than usual because of the dipolar characteristic. And in an enclosure with a woofer it is a no-go anyway. What does work well is a bit bigger enclosure behind the CD, well damped (don't overdo it).
One of the real negatives was that off center the sound chamges much more than usual because of the dipolar characteristic. And in an enclosure with a woofer it is a no-go anyway. What does work well is a bit bigger enclosure behind the CD, well damped (don't overdo it).
No clue about modern horn drivers, but historically with W.E. tiny sealed chamber ~ 'clones' they were already I.B., so a felt lining on the rear cover was sufficient, though did try one with a stuffed TL attached that softened its response a bit more.
to accurately calculate IME.
If it's used accordingly, then not necessarily. The same excursion will produce the same output, notwithstanding whatever effect the new rear radiation will have. We'd have to assume that when the back is removed, the difference is measured and compensated.
Also, compression refers to the opening at the front. This is not a spring chamber, but the rear chamber is one.
Also, compression refers to the opening at the front. This is not a spring chamber, but the rear chamber is one.
A primary reason why I prefer the extended frequency compression driver horn pairing which I'm using is that it is able to throw sound a great distance with excellent directivity. As a result treble frequencies which would otherwise fall off through air over distance are rendered with great and equal authority as the rest of the frequency spectrum. This translates to a level of detail which a direct radiator cannot match even at a listening distance of 15'. I think good directivity and properly implemented compression are essential in order to achieve this quality. I have experimented with different horns and listening to the drivers unmounted to horns in a/b left right comparisons in order to come to this conclusion.
Regarding the original post -- yes, the diaphragm is basically flopping around to a degree as the tight tolerances of the driver in its original 'closed' configuration are lost to an extent reducing performance. If optimized, open baffle all day over closed baffle as it's more true to how instruments function and waves are generated in air. Conventional drivers aren't necessarily optimized for this and thus the principle when considering both may be hard to conceptualize or envision as it relates to transducer architecture. I hope to see driver architectures which consider this in the future.
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You're not suggesting the rear chamber has anything to do with the compression which makes it a compression driver? It's a different thing.
Removing the rear chamber will alter the ratio of input power to excursion because it changes the resonance. When corrected for not having a rear cover, this only means the necessary drive Voltage will change. The diaphragm will still be doing the same thing.
This issue was brought up on another forum site in the past where a JBL compression driver was being used as a direct radiator the way I mentioned but it had a custom protective damping plate to prevent over excursion. Apparently a major cause of blown drivers is due to the deterioration of the foam chamber cover gasket. Using the driver as a direct radiator is probably more novel than useful.
The old Celestion 1300 was essentially a cd motor used backwards, a chamber on the concave side with a diffraction grate on the now front convex side.
Quite good to 13khz, then a steep dropoff, Spendor and others used a supertweeter for that last 2/3 octave.
See Troels for a description.
Quite good to 13khz, then a steep dropoff, Spendor and others used a supertweeter for that last 2/3 octave.
See Troels for a description.