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Allison AL-120 tweeter repair


Carlspeak

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It's become apparent to me recently the tweeter in the subject model speaker was plagued with a common malady caused by corrosion of the tinsel wires. The attached document shows a step-by-step method to make the repair. A jumper wire is fabricated that bypasses the corroded area and is afixed at each end with solder to make a positive connection between the voice coil leads and the connectors where the tweeter wires attach at the back side.

Allison_AL_120_tweeter_repair_doc.pdf

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Yes, please.... :blink:

Polars taken at 1 meter with ECM 6000 test mic. My angles are approximate as I don't have a calibrated rotating table.

The speaker was elevated off the floor. The test software does not use a gated signal. Plot resolution is 1/3 octave smoothed. Test was done with the Al-120 grille on.

post-100237-1277248770.jpg

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This time with the correct title:

Were your polars taken with a grille on? The grille on the 120 is made up of a curved perferated plate covered with a black fabric. Resp tests done with the grille on and off show up to 5 db drop and it could have an influence on polars as well. Again we need to compare apples to apples for a valid test. I also suspect test set ups could affect the outcome.

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Were your polars taken with a grille on? The grille on the 120 is made up of a curved perferated plate covered with a black fabric. Resp tests done with the grille on and off show up to 5 db drop and it could have an influence on polars as well. Again we need to compare apples to apples for a valid test. I also suspect test set ups could affect the outcome.

Grille construction is similar, and I ran Unit #2 both with the grill in place and without. See the legends:

With: http://www.classicspeakerpages.net/IP.Boar...ost&id=5688

Without: http://www.classicspeakerpages.net/IP.Boar...ost&id=5699

Click between them to view the difference.

I presented the original data with 1/6 octave smoothing, and the post-processing at 1/2 octave. The full sets are here:

With: http://www.classicspeakerpages.net/IP.Boar...amp;#entry84951

Without: http://www.classicspeakerpages.net/IP.Boar...amp;#entry84960 (to +/- 45° only.)

Here are the waterfalls:

With: http://www.classicspeakerpages.net/IP.Boar...ost&id=5686

Without: http://www.classicspeakerpages.net/IP.Boar...ost&id=5700 (again, to +/- 45° only.)

As you suggest, the difference is substantial.... :blink:

post-102716-1277320013.jpg

Edit:

Here are the waterfalls for both at 45°

With: http://www.classicspeakerpages.net/IP.Boar...ost&id=5749

Without: http://www.classicspeakerpages.net/IP.Boar...ost&id=5700

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  • 1 year later...

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