The B&C DCM50. Can it replace the K55 driver?

[consistent]

The BMS seems a more 'cheaper' alternative to the more expensive B&C...at least in my part of the world!

[Rudy81]

So will it go to the limit of the driver, on the high end ?

DO you plan on running any test on this. I would really like to go back to passives... Trying to keep it simple.

That's funny. I just finished going through the pains of going active. Minor inconvenience to turn the Furman sequencer on and off, but otherwise pretty simple once setup. It seems the grass is always greener on the other side after all.

[Al Klappenberger]

--55,

"So will it go to the limit of the driver, on the high end ?"

I don't know. All I can say is that I have used my 1-inch horns from 500 Hz up with the JBL 2426 drivers. That driver needs to be EQed because they roll off above about 6 Khz no matter what horn I put them on. The limiting factor is probably the low end. The 2-inch 420 horn looks like it unloads at about 320 Hz on the low end. I don't recommend running it below 400 Hz. That's where the Khorn crosses over. The high limit would be dispersion. I have not measured that.

Al K.

[DrWho]

So what does that section look like, schematically, with the added cap? How is the value determined?

Basically you go from the + input with a cap sized for 6dB/oct hi pass where freq response begins to roll off (approx 4 kHz), bypassing the existing HF network and connecting to the + HF driver terminal thru a padding resistor which adjusts for proper response. Note that there must be a sufficient difference in sensitivity between the other driver(s) to allow for CD compensation.

I tried to find a schematic online, but I wasn't able to find anything so I whipped up a quick sketch of the most simple type of shelf filter.

To think about how it works, basically a filter network acts like a voltage divider and caps are shorts at high frequencies and opens at low frequencies and inductors are shorts at low frequencies and open at high frequencies. So the resistor on the bottom in the shelf filter acts like a voltage divider against the impedance of the driver. Ignoring for a second that the driver impedance changes with frequency, if you had an 8ohm driver and an 8ohm resistor, then the voltage at the driver would be cut in half, so 6dB of attenuation. Since the capacitor acts like a short at higher frequencies, there is no voltage divider and the high frequency voltage isn't attenuated. However, at lower frequencies the capacitor looks like an open circuit, so all the low frequency current must flow through the resistor.

When you throw in the highpass, the cap tries to block low frequencies and then the inductor following it tries to short the low frequencies to ground...which is a really good voltage divider at low frequencies. Higher frequencies short through the cap and then the inductor looks like an open circuit...so no attenuation. The reason for the resistor is to attenuate the frequencies above the corner of the highpass filter...just like in the shelf filter.

I wouldn't actually build this circuit for a variety of reasons, but I thought I'd whip something up to help explain the idea. As long as your CD system has the same sensitivity at 20kHz as your bassbin at the xover frequency, then you don't need to take a sensitivity hit in the lower frequencies. Using a horn that beams the high frequencies to bring up the on-axis response, and then padding down the entire passband to match the LF then results in less overall HF energy in the room because there is now less energy in the off-axis. Now you have to play games with voicing the speaker for the particular application. If you have a flat power response and a flat on-axis response, then you don't need to tweak the sound for a corner versus being pulled out into the room...which makes it way easier to optimize speaker location for things like imaging without messing with the tonal balance at the same time.

And just one other comment...most of the output above ~6.8kHz for a 2" compression driver is going to be dominated by the phase plug and mass rolloff. You would need to go to something like an exponential horn if you were expecting any DI gain from the horn.

[whatever55]

--55,

"So will it go to the limit of the driver, on the high end ?"

I don't know. All I can say is that I have used my 1-inch horns from 500 Hz up with the JBL 2426 drivers. That driver needs to be EQed because they roll off above about 6 Khz no matter what horn I put them on. The limiting factor is probably the low end. The 2-inch 420 horn looks like it unloads at about 320 Hz on the low end. I don't recommend running it below 400 Hz. That's where the Khorn crosses over. The high limit would be dispersion. I have not measured that.

Al K.

Al,

Do you have a K69 to test with ? I would be willing to send one to you for that purpose..

[Al Klappenberger]

--55,

Yes, I would run some tests on a K69 if you care to send me one. I might not have a 420 horn at the time and I might need to wait until Martinelli makes a batch to run the tests though. That could take a couple weeks.

Al K.

[Rudy81]

--55,

Yes, I would run some tests on a K69 if you care to send me one. I might not have a 420 horn at the time and I might need to wait until Martinelli makes a batch to run the tests though. That could take a couple weeks.

Al K.

This should be really interesting.

[whatever55]

--55,

Yes, I would run some tests on a K69 if you care to send me one. I might not have a 420 horn at the time and I might need to wait until Martinelli makes a batch to run the tests though. That could take a couple weeks.

Al K.

OK...

What address should I send them to...

You can PM or email it...

[linkalley]

i have been following the 10 pages. for the life of me, why not try a community m-200 2 inch driver made in THE USA--- that fits the khorn requirement for the 400 hz crossover??? MR. DJK HAS REFERENCED THIS ON MANY OCCASIONS. i have tried them & many others but this one gets it right &&&&&&&&&&& made in usa???

[Al Klappenberger]

Linkalley,

" why not try a Community M200"

Why indeed! I looked at the spec sheets on that driver. It was on my list of drivers to look at when I was looking for an appropriate driver for the Khorn. There is one thing about it that bothers me, fero-fluid cooling. That says that it is intended for very high power applications that we certainly don't need in our application. I have also heard from a good source that PWK once said that fero-flud cooling "sucks the life out of a driver". This is the only reason I did not choose it. Realize that that stuff is a goop that actually sits in the voice coil gap right along with the voice coil. If somebody has one I would be happy to test it though. I understand it has a lower compression ratio than other drivers and lower distortion at high levels. We don't need high levels though. The only real problem with me testing it is that I don't trust my ears and I think that particular driver would require a serious listening test, not just the instrument tests that I do.

--55,

You have a PM.

Al K.

[Al Klappenberger]

Here is the spec sheet on the M200 driver.

http://www.communitypro.com/files/literature/spec%20sheets/M200_SPEC.pdf

It has another problem that may bother some Khorn owners. It is only good to 4000 Hz without help. That would not be a problem for me as my ES4000 network would drop right in.

AL K.

[Rudy81]

What's up with that 5kHz droop in that M200?

[djk]

It's designed to cross at 4Khz, most CLS speakers using this driver cross at 3.5Khz to a 1" driver.

[Al Klappenberger]

Dennis,

I'm glad you joined the discussion.

What thoughts do you have about the fero-fluid cooling? I think the comment I heard from PWK was in reference to tweeters. but since it's second hand information, I don't really know about mid-range drivers.

Al K.

I see another problem. The spec sheets on the M200 show mount studs 1 inch long. My 420 horn only has room for 3/4 inch length. The studs would need to be shortened or replaced to fit. [] I would have to check with Martinelli to see of the throat area could be drilled to pass the extra 1/4 inch. My guess is that it could be done.

[linkalley]

hey al k--- try a hacksaw. it will work wonders on the 1/4 studs. tell you what---- how about i send you an m-200 to test on the 2 inch tractrix horn. i need your shipping address.

i think we all would like to see the graph. djk is right on as the driver must be crossed over at 4k -----and ---- ole hard of hearing bob crites sells the perfect tweet to match up on the top end. my buddy uses a jbl 2404. i prefer phenolic. he simply cannot get rid of his 2404 tweets .

i think most all will agree-- the tractix horn is hard to beat & it fits in top of khorn. i think dr. bruce edgar addressed that nearly 15 years ago.

HAPPY TUNES TO ALL!!!

[DrWho]

What's up with that 5kHz droop in that M200?

Probably the phase plug design (or lack thereof), which they actually show in the datasheet (way cool). The K-55 exhibits the same kind of behavior, albeit with a different design. The 5kHz notch would correlate to a resonance in the throat.

My guess is that low frequency distortion was the primary concern and since a 4kHz xover was the design intent, it was probably cheaper/easier and still achieved the desired HF extension.

The motor looks good to ~7kHz, but it wouldn't make sense to cross that high in a pro sound application, and would add considerable cost.

The M200 has sounded quite good in every pro sound application I've seen them used in.

[Al Klappenberger]

Alley,

I looked at the 420 horn. I'm pretty sure it can be drilled to accept the 1 inch studs without cutting them off. Doing that just wouldn't be reasonable! The two horns I have in stock are spoken for, so I need to be very carefull doing any hacking on Martinelli's handy work to those!

I never bothered to keep the plot of the ES4000 network, but the computer says the actual crossover is 4080 Hz. That would be the upper limit for the M200, You are right about the tweeter. The K77 can't be counted on the extend down to 4000 Hz. You would need to change it to something better. The Crites CT125 would do it.

The address is

27458 Nanticoke Rd

Salisbury MD 21801

AL K.

[pocket.change]

WHEW!

After plugg'n through all this, I'm sure glad my JBL 2482s

are in place.

Hard to believe no one has mentioned them in this discussion.

p.c

[Deang]

They aren't current production, and aren't all that easy to come by.

[ZAKO]

The 2482 phenaulic diaphrames can be replaced with aluminum units from radian,,Increasing its banwidth.