AR-5 Technical Details

[Pete B]

I'm seeing a lot more interest in the AR-5 these days as compared to back 5 or more years ago

when I was here more often.  Someone local is trying to build back up some AR-5 boxes to fully

working systems.  I sold him the woofers from my AR-2axs  but he still needs mids and tweeters.

Anyone have impedance data for the AR-5 midrange, I see one on ebay with and ohm meter 

showing 4.8 ohms but the full impedance curve would be better, even better and .frd file.  Also, 

for the woofer and tweeter.  I should have taken a measurement before I sold the woofers.

I have a midrange substitute in mind but should try to match the impedance as best as possible

and I don't have a sample here to measure.

I measured the AR-11 midrange here many years ago:  http://www.classicspeakerpages.net/IP.Board/index.php?/topic/1400-ar-11-midrange-200010-1-measurements/

I should have uploaded the .frd file years ago - it might still be on my measurement system hard drive.

If anyone knows of online or has AR-5 midrange measurements I'd like to see them.

[Pete B]

I found these specs online and it is interesting to note that both the in system Fc of 56 Hz is given

as well as the free air 26 Hz figure.  I've seen else where that the spec tolerance for Fc is 56 to 58 Hz.

Also, the woofer to mid crossover is 650 Hz - higher than the 3a's crossover:

Acoustic Research AR-5 Specs:

Drive units: 254mm (10in) acoustic suspension woofer, 38 mm (1,5 in) midrange hemispherical dome, 19 mm (3/4in) high-frequency hemispherical dome

Crossover: 650 Hz, 5000 Hz

Impedance: 8 ohms nominal

Controls: Midrange and high-frequency driver level controls

Amplifier: Up to 100 watts per channel

Size: 343 x 610 x 292 mm deep (13,5 x 24 x 11,5 in)

Weight: 17,8 kg (39lb)

Woofer resonance: Free air 26 Hz, in enclosure 56 Hz

Volume of enclosure: 38,2 liters (1.35 cu ft.).

[Pete B]

I posted this many years ago about AR-2ax "pot magnet", 4 bolt stamped frame, floppy cone woofers that I had but were also used in the AR-5:

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:

Woofer #1 MEASURED IN FREE AIR

(12.5 g delta mass)

refoamed with generic 10" foam:

Fs 31.6

Vas 170 l (5.9 cu ft)

Rvc 6.8

Qes 1.05

Qms 7.28

Qts .92

Mms 28.5 g

no .48

SPLref 88.8

Bl 6.0

Fs is a bit high at 31.6 Hz as compared to the spec of 26 Hz, 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.  This is proven out by the in box measurements 

where Fc = 57 Hz is right on the 56-58 Hz spec:

AR-2ax WOOFER #1 MEASURED IN THE AR-2ax BOX

through the crossover:

Fc 57.0

Qec 3.13

Qmc 4.19

Qtc 1.79

The in box bass response into 2pi space is that of a high pass filter with the cutoff frequency being Fc

and the shape determined by Qtc.  The output relative to the woofer's passband is given by:

20 * log Qtc or 20 log 1.79 =  +5.06 dB  that is a very high peak it is an economical way of getting 

baffle step and a more "efficient" woofer from one with less magnet.

[Pete B]

Way back in 2005 I tried a (now discontinued) Peerless 1727 woofer in the AR-5 (really 2-ax) box

and measured these parameters, note the much lower Fc of 44.7 Hz which is much closer to the AR-3a, 

and the much more controlled Qtc of .92,  response at Fc is 20 log .92  =  -.72 dB:

Peerless 1727 WOOFER MEASURED IN BOX  through the crossover:

Fc 44.7

Qec 1.13

Qmc 4.86

Qtc .92

This brings the 2ax close to the AR-3a in terms of deep bass response, but of course not MaxSPL. 

This would be a very interesting upgrade bringing the 5 much closer to the 3a.

I don't plan to discuss this further since this is not intended to be a modification thread.

[Pete B]

It would be good to know the correct Qtc for the AR-5 and I looked through the library but

was unable to find the spec for the AR-2 family or the AR-5.  All other 10" AR speakers, AR-12,

AR-14, AR-48s, had and Fc of 56 Hz and Qtc = 1.15.  My measurement of the AR-2ax woofer of

Fc = 57 Hz and Qtc = 1.79 does not seem to be correct with regard to Qtc and I'm going to 

assume that the woofer is defective.

I also measured a 6 bolt older AR-2x and found Fc = 54 Hz with a Qtc = 1.1 which is very close

to the typical Qtc = 1.15.

I'm going to assume that Qtc = 1.15 is correct for the AR-5 unless someone has better data.

Peaking at Fc = 20 log 1.15 = 1.2 dB at 56 Hz and slightly more above Fc.

One thing to note is that the system Qtc is dependent on the woofer inductor DCR which is

different in the AR-2 family (#5 1.18 mH  .40R)  vs. the AR-5 (#10  3.83mH .92R) with a much

larger inductor value.  The stuffing could be adjusted to compensate for the difference.

 

[Pete B]

AR-5 crossover schematic:

 

[Pete B]

AR coil chart:

 

[tysontom]

14 hours ago, Pete B said:

It would be good to know the correct Qtc for the AR-5 and I looked through the library but

was unable to find the spec for the AR-2 family or the AR-5.  All other 10" AR speakers, AR-12,

AR-14, AR-48s, had and Fc of 56 Hz and Qtc = 1.15.  My measurement of the AR-2ax woofer of

Fc = 57 Hz and Qtc = 1.79 does not seem to be correct with regard to Qtc and I'm going to 

assume that the woofer is defective.

I also measured a 6 bolt older AR-2x and found Fc = 54 Hz with a Qtc = 1.1 which is very close

to the typical Qtc = 1.15.

I'm going to assume that Qtc = 1.15 is correct for the AR-5 unless someone has better data.

Peaking at Fc = 20 log 1.15 = 1.2 dB at 56 Hz and slightly more above Fc.

One thing to note is that the system Qtc is dependent on the woofer inductor DCR which is

different in the AR-2 family (#5 1.18 mH  .40R)  vs. the AR-5 (#10  3.83mH .92R) with a much

larger inductor value.  The stuffing could be adjusted to compensate for the difference.

 

Hi Pete,

I think 1.15 is very close to the average Qtc measurement for the 10-inch (and 8-inch) series.

--Tom

 

[Pete B]

I mentioned in the first post that an AR-5 midrange on ebay showed a DC resistance of 4.8 ohms.

Now a pair is for sale there with one reading 6.0 and the other 6.2 ohms DCR, one question is if

the meters were zeroed before taking the measurements.  An accurate reading would help.