new DS18 Pro D1 2" compression driver - to good to be true?

Dear Tommus,

Points to note:

  • No labelling on any of the axes of the provided graph.
  • Rising frequency response with a phenolic diaphragm.
  • Response flatness exceeds 20x the lower frequency limit (claimed to be 500Hz).
  • 5" diameter driver with 2" voice coil and 35oz ferrite magnet doing 320W program.
  • Poor documentaion with conceptual flaws -"Ferrite motor structure that provides great motor force and loudness.... Ferrite is definitely a great motor structure you want to go with for the absolute loudest ear piercing high range frequencies."
  • Another one = "....titanium voice coil"

Looks like you're being misled. Please specify your application so that someone could indicate any real options available.
 
.....they have a lot of seemingly high-end products. here's a coax compression driver. it's $550....."designed and made in the USA"

Maybe, but what's the point when the original BMS coax (mentioned by David Morison) costs just about the same ? Besides, the BMS coaxes are all reputed, well-tested, well-characterised devices !! In my opinion, at least the cost needs to be much lower for copies (inspirations) succeed. One such example is the PAudio PA-D99 that mimics the JBL2446H at a fraction of its price.
 
What I am really interested in, is an inexpensive 2" CD that doesn't drop off a cliff at 8Khz and can be used full-range (low end 400-600Hz) at low power levels.
I'm not well-informed about copycat Chinese drivers, so I don't know if this company is offering anything new or just low QC copies of other products.
But I assume that somtimes a cheap rip-off can be half-decent under certain conditions.

If the performance of the first drivers I posted are actually a physical impossibility (like rising response to 15K) then I give up.
If there's a chance of something being useful I might buy one and see.
 
What I am really interested in, is an inexpensive 2" CD that doesn't drop off a cliff at 8Khz and can be used full-range (low end 400-600Hz) at low power levels.

If the performance of the first drivers I posted are actually a physical impossibility (like rising response to 15K) then I give up.
Rising response to 15K is not a physical impossibility with a horn that "beams", the narrowing response counteracts the mass roll off all compression drivers have. 109 dB for a "beaming" horn is about 3- 6dB lower than one might expect for a decent driver that may use 1/2 to 1/4 the power to produce the same output.

Since the diaphragm is only 2", low end output is limited to that of a driver like the 1" exit Eminence PSD 2002.

Using a 2" exit horn with a driver using a diaphragm typical of a 1" exit driver will compromise high frequency dispersion. Unless you have 2" horns already, there is little reason to look further at these drivers, especially considering you own better drivers already.

Cheers,
Art
 
Art, I have those Ebay ZXPC K-510 clone horns. Currently messing around with a 2" full-range driver (haven't made noise with it yet though) but thinking already that I will be disappointed with the dynamics. So I am trying to plan for a little better without spending $$$ on a "real" compression driver, while trying to keep it 2-way.

But this seems more and more like a fool's errand, and I am realizing that a 1" tweet + tapped mids is a much better way to go if I want more output.
 
What I am really interested in, is an inexpensive 2" CD that doesn't drop off a cliff at 8Khz and can be used full-range (low end 400-600Hz) at low power levels.
I guess you're referring to the on-axis response curve of the driver. From what I have read, all 2" exit drivers fall off before 10kHz, while 1" drivers hold up to 13kHz or so. However, a horn that compensates for this rolloff can avoid this issue, as already hinted by weltersys. One example I have seen is the JBL2370A that crushes the vertical so much that the horizontal gets equalised to within 6dB (picture). Other horns utilising similar tricks possibly exist.
According to JBL:

"....small vertical mouth dimension was chosen to allow a gradual narrowing of the vertical coverage pattern with increasing frequency. This provides acoustic equalization of the frequency response of the horn in the horizontal plane and compensates for the falling power response of all compression drivers."

I've used the 2370 with the Eminence ASD1001 and very little EQ is required to get to flatness. However, note that this is a horn for a 1" driver. If you're looking for 2" setup, the K-69 driver used by Klipsch with the K-402 horns (BM-D750) is easily available in the open market for DIY (link here) for reasonable money. However, do not trust the response on the BM-D750 datasheet, instead judge this driver based on its actual measured response given by people in the Klipsch forums.
 

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What I am really interested in, is an inexpensive 2" CD .... If the performance of the first drivers I posted are actually a physical impossibility ...

The 2-inch drivers you have mentioned in the opening post also seem to have a 2-inch voice coil and therefore a 2-inch diaphragm at best. Though I've been trying to imagine such a phase plug, I'm unable to do so. Are you sure that these drivers have a phase plug at all ?

Can someone please explain if a compression driver can have a voice coil of the same dimensions as its exit ? This is for my understanding, thanks.