Which 8" coaxial ?

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#81
dirkwright said:
I would guess that the JBL horn would have better controlled dispersion down to 500Hz than the 8" coaxials
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The JBL2385A with the JBL2445 (below) doesn't sound too good at 500Hz. I prefer to cross at 800-1K.
 

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#86
Here are the FR and the step response (inverted) with Xover and some EQing. I had to stop before I was cointent with the outcome but it sounded quite nice at least to my taste. A former incarnation of the X-OVER Eqd the LF section down to a -6dB point of 40 Hz (fc' of 40 Hz with a Qtc' of 0.5) but this seemed to be too power- and excursion- hungry.

Regards

Charles
 

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#87
dirkwright said:
Likewise, BMS must not be entirely truthful or at least realistic about their drivers either.
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The data on their spec sheets is honest if you know how to read one. The drivers are sold and the manufacturer cannot know how they're going to be used so it's conceivable that they will be used that low. There is an Oris implementation that xod them at 220hz but I have never heard it.

I never thought mine would work to 300Hz, but I tried it to see.
 
#89
Michael Chua said:
Thanks for your measurements. Any idea the cause of the notch at about 1,700Hz?
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Yeah, I'm wondering too, because a dip like that usually means a long ringing tone when seen on a waterfall... as seen here and here, for example.

The B&C 8CXN51 doesn't look too bad, though ! And I wouldn't be surprised if it was the driver used here and in a few other commercial designs...
 
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#90
The dip could be due to some standing wave or the like. Maybe it goes away when the protective grill is removed. But together with the xov that I used there is not much left of it. Altough the woofer dip below 1.5 kHz is still a little prominent.

Regards

Charles
 
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#91
Brett said:
The data on their spec sheets is honest if you know how to read one. The drivers are sold and the manufacturer cannot know how they're going to be used so it's conceivable that they will be used that low. There is an Oris implementation that xod them at 220hz but I have never heard it.

I never thought mine would work to 300Hz, but I tried it to see.
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All I'm saying is that the manufacturer says they can be used down to 300Hz, but your and other's experience seem to indicate that it is not realistic to cross over that low.
 
#93
dirkwright said:
It's a shame they advertise them as being good that low.
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The JBL2385A can be crossed at 500Hz. It's just that for hifi use, I prefer to cross higher (before the roll off). You can see from the FR below that 500Hz is somewhere down the roll-off slope.

In SR use, where these monsters are designed for, you may want to cross at 500Hz if you have a 15" 2-way.
 

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#96
Loudspeakers' manufacturers like Cabasse, Tannoy, Kef, Tad or Thiel have excellent coaxial drivers on the reference models, but I think they're not available for the diy community.

I believe the Beyma 8CX300Nd is the most advanced coaxial from Beyma with 8" (not in your list):

http://profesional.beyma.com/ingles/pdf/8CX300Nd.pdf

Seas' drivers have a high reputation on the diy community. Consider these two (although slightly smaller than 8"):

E0051-04/06 C16N001/F

H1333-08/06 T18RE/XFCTV2

I also like Visaton. It has a new coaxial driver (although only 4") that looks promising:

Visaton HX10_4
 
#99
Speaker measurements

Been noted elsewhere on the forum, czech distributor of BC, RCF and other brands has a comprehensive archive of measurements of every model they are (or have been) selling and it is available here
PRODANCE - profesionální svìtelná a zvuková technika - hope you can deal with czech somehow 🙂

RCF has a floor monitor series starting with 10" coax, the speakers are being active and are multipurpose ie can be used as small pa if needed and sound very good, just had a chance to audience them last saturday and compare them to lots of other models
another diy guy (http://www.splacoustic.cz) made great monitors using 12" coax

btw the bc 8" seems to produce pretty good result using the bc supplied xover - http://www.prodance.cz/protokoly/bc_8cxn51.pdf
 
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