AR91 repair story - new mids and tweeters identified

[Pete B]

I was just re-reading some of my old posts and wanted to ask if we ever figured out when

the 1.88 to 2.85 mH inductor change happened in the AR-3a? Did it match the cone mass

change?

[RoyC]

I've been using the MWA 6 inch 6004B spider for the ceramic magnet woofers, and 5 1/2" 5503B spider for the alnico woofers. Fs has always measured less than 20hz with MWA foam surrounds and these spiders with original cones. (I always try to retain the original cone.) My Fs results with the new cone have been around 21hz with the "Msound"/MWA kit....similar to Carl's. It should be noted there are 2 voice coils available. The "kit" voice coil's dcr is around 3.5 ohms, and the other is around 2.5 ohms, which is closer to the original spec. Both are are about the same size, and fit very well. Le of both voice coils are a fraction (.3mh+/-) higher than original. They have metal formers. The ceramic magnet woofer I referred to above had a paper former.

Pete, the foam damping ring was used on the alnico woofer cones, and used for just a year or so with the first ceramic magnet woofers. The foam is very much like the high density gasket tape foam sold by Part Express. It appears to be the same thickness.

The inductor change occurred with the switch to the ceramic magnet woofer and new cone around 1970.

Roy

[Carlspeak]

The spider from Nu-way was to test the fit but I don't think they had a

very high compliance off the shelf part. They'd do a custom spider

for a large minimum order. It feels like an MWA C type. The best I

seem to have is an MWA 6004 B. I don't think they had an A at the

time I ordered. The Nu-way sits perfectly on the 6004B and seems

to have the exact same dimensions. They probably make the spiders

for MWA at least at the time I ordered.

23 Hz should be fine since the box compliance dominates. Mass is the

most important factor and it seems that we're getting a better handle on

it. Still, I wouldn't want the Fs to be much more than the 23 figure.

My latest 3a kit order had 5003-B spiders. Quite soft which may have helped get the 23 hz Fs with the light cones. I don't think MWA has any 'A' texture spiders.

[Pete B]

I've been using the MWA 6 inch 6004B spider for the ceramic magnet woofers, and 5 1/2" 5503B spider for the alnico woofers. Fs has always measured less than 20hz with MWA foam surrounds and these spiders with original cones. (I always try to retain the original cone.) My Fs results with the new cone have been around 21hz with the "Msound"/MWA kit....similar to Carl's. It should be noted there are 2 voice coils available. The "kit" voice coil's dcr is around 3.5 ohms, and the other is around 2.5 ohms, which is closer to the original spec. Both are are about the same size, and fit very well. Le of both voice coils are a fraction (.3mh+/-) higher than original. They have metal formers. The ceramic magnet woofer I referred to above had a paper former.

The inductor change occurred with the switch to the ceramic magnet woofer and new cone around 1970.

Roy

I'd avoid the 3.5 ohm VC it is too far off and will not load the crossover correctly.

I'd expect the sensitivity to be significantly different also.

[RoyC]

I'd avoid the 3.5 ohm VC it is too far off and will not load the crossover correctly.

I'd expect the sensitivity to be significantly different also.

Pete,

Could the higher dcr of the kit voice coil compensate somewhat for the lighter replacement cone?

Roy

[Pete B]

It will lower the voltage sensitivity but obviously it does nothing to lower Fc,

and it will shift the crossover frequency and Q.

I found a picture of the woofer with the foam and, from memory, I was

picturing something different. I didn't remember that it was so wide and

thin.