Eminence Beta 10CX (ZMA/FRD)

Testing out the 10CX coax. Box is BR (Int Vol=52L).

ZMA file download



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If you think the midwoofer on-axis plot is bad, just wait until you measure the effect it has on your compression driver on-axis response.

We're talking a huge -22dB notch at about 6khz and several smaller notches. Off-axis it measures a lot better though.

Most important to note is that frequency response rarely has much to do with sound quality though. A frequency plot can be used to detect were something could be improved but you really can't say from a frequency plot that a driver sounds bad from the start. Horrible sounding drivers often measure really well on a frequency plot.
We're talking a huge -22dB notch at about 6khz

That's a deep notch. Have you tried reversing the phase of the compression driver.

Please post the fr plot of your 10CX (on-axis). It'll be interesting to see what kind of response you're referring to. By the way, what is the compression driver you're using?

I'll be out of town for a couple of days. I'll respond when I return.
The notch is due to LF drivers voice coil former protruding from the mouth of horn. If you dare to remove dust cap and know how to cut protruding part you could get rid of the notch (or most of it). But in practice it won't bother you and will not spoil listening experience although it looks ugly in the graph.
Can you post the graph with the notch and a picture showing the woofer voice coil former protruding from the mouth of the horn?

Unfortunately I can not find graph. It is published in Klang & Ton CT235 project so it is copyrighted. But I do not recommend this tricky removal of protruding part of vc former. It is very difficult, former is very hard for cutting.
Well, it seems that I was wrong. I found K&T CT235 project and it say that 6kHz notch is "ein Phaenomen, das durch die Bauform des Hochtonhorns verursacht wird", meaning that the bullet inside horn is responsible. And graph shows it with APT50 measured alone, without being mounted inside Beta 10CX, although LF drivers vc former protrusion seems to enhance the effect. If you want to get rid of the notch at any cost you can replace APT 50 with another compression horn driver that does not have bullet plug inside.
Thanks for the clarification. I don't have the APT50 nor do I intend to use it with the 10CX. I cannot accept crossing a 10" at 3,500Hz. It's much too high for my liking. I suppose it'll be fine as ceiling speakers for voice announcements but not for hi-fi.

My Radian 8" coax crosses at 1,800Hz. My bigger Radian, a 12" Coax, crosses at 1,500Hz. I assume somewhere in between is suitable but looking at the horn response with the RX14, I'm inclined to cross at 2,000Hz.
APT 50 is crossed at 2kHz (with Beta 10CX) in K&T CT235 project without any problems. Many people use Celestion CDX1-1425 instead of APT50 in the same project and cross also at 2kHz. They say that Celestion sounds much better. But Eminence ASD1001S is direct replacement with bigger diaphragm that can be crossed low.


Paid Member
2007-06-10 12:41 pm
Hello All,

I am working on a speaker using Beta10cx and ASD1001. I have taken some measurements of this combination to see what the general view is.

Measurements were taken using room eq wizard v5. Off axis is as shown in the picture, I did not have an protractor to hand. Levels are all relative but are all taken at the same gain settings so can be compared with each other (as I can't find my SPL meter).

My initial observation is that the ASD1001 goes much lower than expected and that the 4k - 12k broadband notch is not observable off axis. In general the offaxis response looks much better than the on axis. The reduction in woofer level <230Hz is the expected baffle step, bass response is close to predictions.


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Hello kipman725

Thanks for sharing your measurements. The 4k - 12k broadband notch is quite usual. I don't believe I've seen anything quite like it before. Normally, the horn response either tapers off linearly or sometimes with certain compression drivers, there's a sharp cone breakup at about 10K-12K.

Unfortunately, I don't have the ASD1001, otherwise I can run a comparison test.
Hello Kipman725 & Michael Chua,

Just a short question - so how do they sound? Is it worth building such a speaker or is it a waste of time. It seems that people who have actually build-it, are very satisfied with it.
Wonder how close is to full range speaker in terms of sound cohesion?
I would like to have one point source monitor for alternative listening but with some bass and treble since I got disappointed with different Fostex speakers in the past.
Hi tubemax

They sound wonderful. If you're looking to build your first coax, I highly recommend the Beta 10CX. It is not only very affordable but surprisingly, is an excellent performer.

I can't comment on full range drivers because I am not really into them. The only driver I tested is the Audio Nirvana AN12CF. The Beta 10CX is far better. You will get Bass and Treble with the 10CX, no problem with that. Coherency is what one would expect from a point source.

Presently, the compression driver I'm using is a Peavey RX14, a 1" titanium compression driver. The frequency response plot is below. Disregard the region below 500Hz. You can see the effects my room has on the bass measurement.

I will be testing it with a Selenium D220Ti later. I should be able to cross at 1,500Hz with the D220Ti.

For more information on the 10CX, click here.


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