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Old 13th April 2008, 08:52 AM   #3351
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Aside from the technical aspects of the Unity, which theatre loudspeakers or commercially available studio monitors use them? I look at these applications and I see JBL dominating the world market, with a sprinkling of other brands - EAW, Meyersound, Westlake, Dynaudio, Genelec, PMC, ATC, and a variety of others.

Only a few professional products mention the impulse response, such as the MeyerSound X-10, and even then, we don't get to see what it looks like 15 and 30 degrees off-axis. The performance of the constant-directivity waveguide will have a big impact on the off-axis impulse response.
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Old 13th April 2008, 02:02 PM   #3352
mige0 is offline mige0  Austria
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Quote:
Originally posted by Lynn Olson

The demands on the 10 to 15-inch speaker that meets the compression driver and horn system are very high: more than 96 dB/metre efficient, linear magnetic-system design (underhung voice-coil strongly preferred), low IM distortion particularly in the 500 Hz to 1.5 kHz range, and freedom from high-Q breakup modes at frequencies higher than 1.5 kHz.

Beyma 102Nd (very speedy),
http://www.beyma.de/index.php?id=126
http://www.beyma.de/fileadmin/seiten...onal/102Nd.pdf

Beyma 12MW NdE (low distortion, soft roll off),
http://www.beyma.de/index.php?id=179
http://www.beyma.de/fileadmin/seiten...al/12MWNdE.pdf


or probably - if not crossed too low - two vertically stacked Beyma 6G40Nd (excellent directivity)
http://www.beyma.de/index.php?id=120
http://www.beyma.de/fileadmin/seiten...nal/6G40ND.pdf
matching the directivity of the Raal if the horn experiment fails for one reason or another

None of them under hung VC anyway.

Low (Doppler-) IM basically is the product of low frequency excursion (big Sd for given LF-SPL) and the frequency span to the point of measurement as outlined by John Kreskovsky earlier - and easy to calculate with the spreadsheet I have put together not so much brand dependent at the very first glance.



Greetings
Michael
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Old 13th April 2008, 02:10 PM   #3353
SunRa is offline SunRa  Romania
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Quote:
or probably - if not crossed too low - two vertically stacked Beyma 6G40Nd (excellent directivity)
Hello Michael,

any reason for not using the 605nd or the 6nd410 in the configuration above? The spl figures are much higher compared to 6G40Nd.
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Old 13th April 2008, 02:18 PM   #3354
Anglo is offline Anglo  Canada
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Lynn,


http://www.diyaudio.com/forums/attac...amp=1207965148



Are these available somewhere or is there more info on the specifics of these amps.

Also, I am SET 845 fan, does this fit my cord in comparison?
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Old 13th April 2008, 02:24 PM   #3355
mige0 is offline mige0  Austria
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Quote:
Originally posted by SunRa

any reason for not using the 605nd or the 6nd410 in the configuration above? The spl figures are much higher compared to 6G40Nd.

Hello SunRa,

The 605 Nd is my personal favourite but is somewhat peaky at the high end and does not have the excellent directivity of the 6G40Nd up to nirvana.

Same for the 18 Sound - with regard to directivity (they also do not supply distortion figures to compare with).

Besides that the 6G40Nd is a very powerful speaker providing an impressive 110 dB at 1m in a 400mm (16") OB as a single driver down to 250Hz.


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Michael
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Old 14th April 2008, 02:35 AM   #3356
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Thanks, Michael, for the links to the Beyma drivers. The 10 and 12-inchers look good, with the 12MW Nde looking like an interesting alternative to the Altec 414's - efficient, very smooth response, low distortion, all good things. The 6-incher is rougher than I'm comfortable with, unless the HF notches and peaks are artifacts of test cabinet diffraction.

The major divisions on the Beyma graphs are 5 dB, and the entire FR curve of the Ariel fits inside a 5 dB window, with most of the local deviations being smaller. I'd like the FR of the completed system to fit in a fairly tight window, and with a minimum of notch and shelf filtering.

As for commercial availability of the Karna amplifier, maybe some day, if I could license the design and chase out the remaining technical issues - that alone is a 1-year project or more, and one that I've set aside for now pending the completion of the new speaker system.

845 SET amplifiers have very serious issues with driver-tube distortion. The distortion of the 845 is very low, in the 300B league, but the 120~150 volt bias demands drive voltages twice as large as the 300B, and there's just as much Miller capacitance as a 300B. In other words, a difficult-to-drive, highly reactive load at higher frequencies (potential slewing problems).

This a creates a requirement for a driver section with less distortion than the output tube at grid-drive levels around 200V rms - a small, ultralow distortion Class A power amplifier in its own right. No known RC-coupled driver can accomplish this due to the slope of the load-line and power losses in the plate-load resistor. Choke, transformer, or dynamic loads can do this, but only DHT's achieve the requisite low distortion levels - and it seems pointless to use a low-distortion output tube if the driver distortion swamps it out.

So-called distortion-cancellation schemes using driver tubes with complementary distortion to the output do not account for the upper harmonics, which are the ones that really matter. (2nd harmonic dominates THD measurements but is nearly inaudible. The magnitudes of the upper harmonics - 3rd, 4th, 5th, etc. - are much smaller but are also much more noticeable.)

If you like the sound of the 845 (SE or PP), seek out a design that uses a DHT driver and choke, transformer, or active loads for the driver. No RC-coupling, sorry. It's easy and cheap to do but has 3~5 times the driver-tube distortion, not a small difference. That probably eliminates most commercial 845 amplifiers, and many DIY designs.
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Old 14th April 2008, 04:14 AM   #3357
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While keeping things off-topic:

Quote:
Originally posted by Lynn Olson
If you like the sound of the 845 (SE or PP), seek out a design that uses a DHT driver and choke, transformer, or active loads for the driver. No RC-coupling, sorry. It's easy and cheap to do but has 3~5 times the driver-tube distortion, not a small difference. That probably eliminates most commercial 845 amplifiers, and many DIY designs.

Do you mean something like this ?


If memory serves well there are quite a few topologies using 300B as a driver and 845 (or even an 805 !!) as output tupe, in either SET or PP topologies. Alas not many of those have are freely available circuit diagrams ...
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Old 14th April 2008, 04:41 AM   #3358
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Lynn you can find some testing I did on the 6G40Nd in my sig link.
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Old 14th April 2008, 05:19 AM   #3359
SamL is offline SamL  New Zealand
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Quote:
Originally posted by augerpro
Lynn you can find some testing I did on the 6G40Nd in my sig link.
Hi Augerpro,

Guess I must be the biggest dummy. No problem accessing your photo album but there no description to tell which measurement is for what.
Can see the photo of 6G40Nd but without desc, can't tell what driver is next to it. Is it bec I don't have a login ID to the site?
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Old 14th April 2008, 09:46 AM   #3360
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All the driver tests are listed along the left side of the screen. The rest of the of the stuff on the main page is just my junk.

Sometimes I forget to give the pic a title, but if you hover the mouse cursor over the pic it will show the filename, which describes the measurement. Generic measurment info for all the tests is in the READ THIS FIRST folder.

The driver next to the Beyma in the picture is teh B&C 6NDL38.
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