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Old 26th October 2012, 02:04 AM   #8291
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Default "Ideal"

How is a Helmholz resonator an ideal reproducer of a microphone input? Isn't a sealed box the least damaging option?
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Old 26th October 2012, 03:02 AM   #8292
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I have been using a 50Hz bass horn with a Vitavox K15/40 drivers. I don't get the extension, but it integrates and images well. Probably the time alignment issue takes this outside of any acceptable spec, however I have always wondered how direct radiators ever achieve time alignment (due to the phase shift that comes with flat response - which horns in the pass band in theory dont have). . The driver on the 425 horn is Yamaha JA6681B, and I have a Fountek ribbon tweeter next to it. Compared to a Fostex T900A horn tweeter I prefer the ribbon, bearing out what Lynn says, and may well go for the RAAL.


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Old 26th October 2012, 05:47 AM   #8293
puppet is offline puppet  United States
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I haven't yet figured out an attractive-looking cradle for the compression driver; it needs to have about an inch of front-to-back travel so it can be time-aligned in-room (time-aligning partly depends on seating height).
Have you considered using a pair commercial grade ballbearing drawer slides? K&V make these and I believe they can be had in a 6" length. They can be mounted flat ... as in under your horn carriage ... so, directly attached to the woofer top panel. Slide horn in or out to suit
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Old 26th October 2012, 07:18 AM   #8294
DeonC is offline DeonC  South Africa
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Hi Lynn

I hope you don't mind all the questions, but I guess everyone wants to lnow the thoughts of the master. I hope you don't mind if I add a few of my own.

As to box loading, IIRC you did consider open-baffle for the 'Beyond the Ariel' project, but what do you think of cardioid loading. To me it seems to be halfway between resistive vent and open baffle. Possibly a good compromise between them? I have read a lot of good comments about it.

Second, have you seen North Creek Music's MAPD driver loading technique? It looks very interesting and could work well, but needs a very large box. However if, as the advertising blurb states, and it does reduce suspension non-linearities, it could be interesting. It will just be impractical for a drivers with very large Vas (like my Tannoy DU386 with a Vas of 770 liters ).

Thanks again for putting up with all the questions.

Regards,
Deon

PS. I was curious to read your opinion on the MLTL. Is it just another form of TL, i.e. good?
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Old 26th October 2012, 05:40 PM   #8295
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Have you considered using a pair commercial grade ballbearing drawer slides? K&V make these and I believe they can be had in a 6" length. They can be mounted flat ... as in under your horn carriage ... so, directly attached to the woofer top panel. Slide horn in or out to suit
How do you avoid rattles?
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Old 26th October 2012, 06:48 PM   #8296
puppet is offline puppet  United States
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How do you avoid rattles?
The tolerances in this type of drawer slide is very close. I wouldn't expect any rattles.

http://www.knapeandvogt.com/8800_Hea...ils.35#details
http://www.knapeandvogt.com/4100_Low...age=details.46

Other makers offer a similar designed slide. If you look at the section thru the slide (in the .pdf file) ball bearings are loaded in four places (bearings not shown). They are loaded where each section is curved to correspond with the curve of the mating section. The whole assembly is pretty tight. They offer a 12" length (in the heavy duty) and 8" (in the medium duty) but I'm pretty sure I've seen shorter.

Last edited by puppet; 26th October 2012 at 07:07 PM.
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Old 26th October 2012, 07:13 PM   #8297
Pano is offline Pano  United States
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Truetone - very unusual looking system. And I enjoyed the nice B77 on the shelf.
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Old 27th October 2012, 12:26 AM   #8298
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Guys ... a tight slide is two or more pieces of something bolted together (wood comes to mind) that is adjustable. Slides aren't. Zene
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Old 27th October 2012, 07:01 PM   #8299
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Is it unreasonable to think that the exit angle for the 288k is similar?
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Old 27th October 2012, 07:07 PM   #8300
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The exit angle of the 288 has been measured by Bjorn Kolbrek as being between 7 and 8 degrees. The AH425 is optimized for that angle. The Radian 745P and 745Neo is 4 degrees, according to the engineer I spoke with at Radian, which gives a very slight mismatch to the AH425 but I saw no time-domain artifacts when I measured the Radian/Azurahorn combination.

By measurement and audition, both the Altec/GPA 288 and the Radian 745Neo are excellent choices for the AH425, with very flat responses (+/- 1 dB) in the 700 Hz to 7 kHz range. No equalization was required - the system response is as flat as any soft-dome tweeter, but with 10~20 dB more headroom.

Martin of Azurahorn is using the rare Yamaha driver, and he's getting really good results as well.
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