Small MLTL for Mark Audio Alpair 6 Drivers - Page 3 - diyAudio
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Old 2nd April 2009, 06:19 AM   #21
EUVL is offline EUVL  Europe
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What didn't you like precisely, if I may ask ?

Patrick
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Old 2nd April 2009, 06:35 AM   #22
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I thought it killed the sound, for want of a better word. Any component in the signal path is always going to sound worse than nothing at all. Also when I measured FR it didn't appear to need any BSC.
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Old 9th June 2009, 06:45 AM   #23
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Default Transmission Line

The CHR 70 will do -3 db at 38hz with a transmission line enclosure. It is really an impressive driver for the price. Can not wait to get my hands on an alpair 6 in a TL and see what it can do!

Matt
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Old 15th July 2009, 09:43 PM   #24
Colin is offline Colin  United Kingdom
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I wouldn't normally consider using a different driver for a specific enclosure design but as the Alpair 6 and Jordan JXR6HD specs are so close ...

Does Jim or anyone consider the two driver close enough to use the JXR6 in this MLTL design and if so which parameters (if any) will need adjusting?

Specs on the JXR6 pair I have are:

FO Hz - 65 Hz
Qm - 1.634
Qe - 0.71
Qt - 0.495
Re ohms - 4.498
Vas - 3.051 litres
Xmax p-p - 6.00 mm
SPL 1m 1w - 85.38

These are the standard specs for the last batch made by Mark - the F0 was measured for this pair by Ted. I initially thought the JXR6 would be unsuitable a it lacks a rear spider but I think the Alpair is the same. Is this correct?
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Old 16th July 2009, 12:29 AM   #25
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No, the Alpair 6 is not the same. It does have a rear spider.
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Old 16th July 2009, 02:18 AM   #26
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Default Re: Transmission Line

Quote:
Originally posted by mdrake74
The CHR 70 will do -3 db at 38hz with a transmission line enclosure.
Mark,

IIRC this was in reference to some plots you posted elsewhere where your measuring kit was clipping (making the measures invalid)?

dave
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Old 25th March 2013, 08:07 PM   #27
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Default Use of Generation 2 Alpair 6 Drivers

I recently did a little study to determine the functionality of Alpair 6.2 drivers in my Alpair 6.1 MLTL design. My original design used the first generation metal cone Alpair 6 drivers but only second generation drivers are currently available. The second generation drivers are the Alpair 6.2P (paper cone) and 6.2MA (metal cone).

In my simulations I use Martin King’s excellent worksheets to derive performance plots of the driver within the enclosure. In the Martin King simulations you enter the T/S specifications for the specific driver you plan to use. Next you enter an enclosure model which consists of the box length and cross-sectional area, driver location, port location, port length and diameter, and stuffing density. You then vary the box parameters and iterate until you achieve acceptable results. I usually aim to have flat frequency response down to the 3 dB corner frequency. Then I check the other performance curves to verify adequate results for impedance, phase, deflection, etc.

I re-ran my simulation model with the 6.1 driver and then plugged in Thiel/Smalle parameters for the 6.2P and 6.2MA drivers. I retained the same enclosure model for all three cases so only the T/S specs were changed for each driver. All T/S specs used were the values given on the Mark Audio and Madisound websites. For the MLTL enclosure entries I used the dimensions that I gave in the first message in this thread. Now if you compare the T/S specs for the 6.1, 6.2P, and 6.2MA drivers, there are minor differences between the three drivers. The question I had was whether the different drivers would yield similar performance results.

My MLTL Alpair 6.1 design yielded a 3 dB down point (F3) at 44 Hz with a port length of 4”. When I compared the performance curves of the three drivers, the SPL response vs. frequency plots were nearly complete overlays. The 6.1 and 6.2P drivers differ only by width of the ink lines on thier plots while the 6.2MA driver seems to have a shift of less than 0.5 dB higher SPL level vs. the other two drivers.

Thus I concluded that any of these three drivers will perform the same in my MLTL box. Of course T/S specs may differ across the production of these drivers so it is always best to measure your own drivers and rerun the simulation model to ascertain the expected results. Fortunately, most of the Mark Audio drivers are built in a single manufacturing lot so differences should be very small.

Last edited by Jim Griffin; 25th March 2013 at 08:14 PM. Reason: correction
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