Why does a compression driver need a horn?

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
drewmc said:
The horn is designed to do two things:
1 Provide proper loading for the CD
2 Provide the desired directivity or sound coverage
Without proper loading the CD will not achieve the designed efficiency.

So if a CD was to be used without a horn, the the sensitivity would just be lower, and dispersion would be more or less like a dome tweeter, just with higher sensitivity?

So theres nothing stopping a CD to be crossed to say.... a small 3 khz waveguide to get good sensitivity and controlled dispersion? Seems like a much better alternative to the regular dome tweeter...
 
Defo said:


So if a CD was to be used without a horn, the the sensitivity would just be lower, and dispersion would be more or less like a dome tweeter, just with higher sensitivity?

So theres nothing stopping a CD to be crossed to say.... a small 3 khz waveguide to get good sensitivity and controlled dispersion? Seems like a much better alternative to the regular dome tweeter...

A compression driver IS a dome tweeter. Except it's buried inside of a compression chamber, with a sophisticated phase plug on the other side of the diaphragm.

Without a waveguide, the frequency resonse of a compression driver will be terrible... You definitely need to use one.
 
Ex-Moderator R.I.P.
Joined 2005
Defo said:


So theres nothing stopping a CD to be crossed to say.... a small 3 khz waveguide to get good sensitivity and controlled dispersion?

Seems like a much better alternative to the regular dome tweeter...


Could be, but you need a small sensitive pro mid, which mostly only does it down to about 400hz

Alternative to dome tweeter?
You will need a lot of attenuation best done actively
Or low gain power buffer amp :D

btw, Bastanis doesnt have any horn/waveguide, but is crossed very high

But why cross high when it easily go lower with rather small waveguide
I see that as the main advantage of a CD
 
tinitus said:



Could be, but you need a small sensitive pro mid, which mostly only does it down to about 400hz

Alternative to dome tweeter?
You will need a lot of attenuation best done actively
Or low gain power buffer amp :D

btw, Bastanis doesnt have any horn/waveguide, but is crossed very high

The Bastanis has a short horn on the front, and no compression chamber. So it's a dipole tweeter with a horn on one side, but not the other. The horn side has a phase plug. Kind of an odd design, but sounds very good.

vc.JPG
 
Ex-Moderator R.I.P.
Joined 2005
Nice picture

I knew it would be commented when I said no horn
Im sure the rounded edge have some effect
But I guess its mostly phase related
But from picture tweeter frontplate could seem to have become thicker
I suppose its only the most expencive version with this dipole option

It the backside of CD diaphragm we see on picture?
I always thought the dipole action was achieved by additional driver

ehh, does that mean that the voice coil is mounted in front of the diaphragm:confused: says rear facing free voice coil, but its hard to see really
 
Defo said:
So theres nothing stopping a CD to be crossed to say.... a small 3 khz waveguide to get good sensitivity and controlled dispersion? Seems like a much better alternative to the regular dome tweeter...

That's what the small B&C DE10 + ME10 (a horn, not a waveguide) combo does for a handful of euros. I'm very happy with it, in a three way active system. :)

An externally hosted image should be here but it was not working when we last tested it.
 
What exacly happens if a compression driver is used below horn cutoff?

Since most wideband compression driver diaphragms rest a fraction of a millimeter from the phasing plug, the likely scenario is that the diaphragm will make dramatic contact with the phasing plug at any real SPL. If it's a composite or polymer diaphragm, it will just sound bad. If it's a beryllium diaphragm, it will sound bad very briefly and become expensive confetti. :(

Also, keep in mind that, depending on the horn, "horn cutoff" may be well below the Fs of the bare driver.
 
Just to present a minority view, though, I'd say that a hornless compression driver isn't necessarily always a non-starter. Like any driver, you simply have to look at its capabilities in the intended alignment and judge whether it fits your goals. Sans horn, you have to take its reduced power handling into account and its likely non-flat FR.

Common wisdom isn't always wisdom. A bare compression driver certainly won't always work as you might hope, but there is a small sub-set of cases in which it might work very well.
 
Administrator
Joined 2004
Paid Member
As far as I understand, a compression driver will be damaged if operated without its horn at anything above a small fraction of its 'normal' power. The horn is an impedance matching device, and without it, the diaphragm is poorly coupled to the mass of air it is intended to move. You get excessive diaphragm excursion, which will do it no good.

That's a really good point which is why I never run my JBL cds without their horns. In addition I do not run them below their recommended cut off either in order to prevent over excursion of the diaphragms. The diaphragms are really expensive to replace which is why I am careful. I've blown up enough drivers over the years - I'm so over that.. :D
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.