Pete B Posted September 28, 2005 Report Share Posted September 28, 2005 I measured a pair of 4 bolt AR-2ax woofers, these are ALNICO with very floppy cones. The spider is much stiffer than those used in the 11/12" woofer and the cone readily comes back to center position when pushed even without the foam edge.I refoamed #1 using generic 10" foam from one of the major suppliers. This foam feels stiff compared to some others that I've used. I got side tracked from this project and have not yet refoamed woofer #2 and decided to try measuring it without the foam edge, the results are given below:Woofer #1 MEASURED IN FREE AIR(12.5 g delta mass)refoamed with generic 10" foam:Fs 31.6Vas 170 l (5.9 cu ft)Rvc 6.8Qes 1.05Qms 7.28Qts .92Mms 28.5 gno .48SPLref 88.8Bl 6.0Fs may seem to be high, however I've pointed out several times that it's moving mass or Mms that matters since as long as Fs << Fc the box air spring dominates. Also notice the high Qts which indicates a weak magnet, people like ALNICO and it does have some excellent properties but it is expensive and it appears that more could have been used. AR-2ax WOOFER #1 MEASURED IN THE AR-2ax BOXthrough the crossover:Fc 57.0Qec 3.13Qmc 4.19Qtc 1.79The Fc spec for the AR-2ax is 56 to 58 Hz, it's right on the money even though Fs is a bit high. This supports my statements that moving mass is most important. Notice how high Qtc is, this system is going to have a significant amplitude peak around Fc.Peerless 1727 WOOFER MEASURED IN THE AR-2ax BOXthrough the crossover:Fc 44.7Qec 1.13Qmc 4.86Qtc .92This brings the 2ax close to the AR-3a in terms of deep bass response, but of course not MaxSPL. The Qtc is higher, a Qtc of 1 would have minor peaking above Fc and cross the 0 dB level at Fc. This supports my claim that it is a significant upgrade from the original woofer. It is a bit less efficient, sorry I don't have a number handy, and needs a lot of power (50W or more) to really perform. I did not measure the midrange response or how this driver blends with the midrange, but I did give it a quick listen and I did not hear any obvious problems. I do not believe the AR-2ax is up to modern day standards as far as driver integration goes even with the original drivers.AR-2ax WOOFER #2 MEASURED IN FREE AIR WITHOUT FOAM EDGE,YES JUST THE SPIDER (12.5g delta mass):Fs 24.0Vas 280 l (9.9 cu ft)Rvc 6.4Qes .90Qms 9.6Qts .82Mms 26.3 gno .41SPLref 88.2Bl 5.3Cms 1.68 mm/NThese data and data from this driver after refoaming will allow the edge compliance to be calculated.This is the original thread where we discussed the Peerless 1727 woofer in the AR-2ax box:http://www.classicspeakerpages.net/dc/dcbo...ing_type=searchPete B. Link to comment Share on other sites More sharing options...
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