Westrex

**Andywin** · April 27th, 2012, 04:12 PM

The Westrex 2080E bass drivers in my 2326A's have an added mass ring around the circumference of the dust cap.

My understanding of mass rings is that they effectively lower the frequency response.

They certainly seem to go as low as the JBL 4333's I used to have that were reconed to 2235 spec and are certainly more articulate. The reproduction og bass guitar and doublr bass id the most realistic I've ever heard.

Did Altec ever go down the path of adding Mass? If not, I think they missed a trick.

IMG_1332.jpg IMG_1333.jpg

**VolvoHeretic** · April 27th, 2012, 05:55 PM

I think that I want to try the added mass to my bastard 418-8H II A8 clones, (but cheating with a graphic equalizer goes a long way to the bass junkie fix I want) and I have the math linked around here somewhere, just can?t link up with my too busy engineer son to run the math. What is that metal ring, copper wire, gold painted steel coat hanger? This 418 has no cooling venting front or back, I wonder if I need to cut out a quarter sized hole through the aluminum dust cover first, then glue on a 416 paper vented dust cover over that, and then add the wire ring, adjusting the wire gauge to fit the mass needed? Just how accurate does the added mass have to be, calculated weight of glue and actual globbed on are two different things?

GM · April 27th, 2012, 06:37 PM

Originally Posted by VolvoHeretic

This 418 has no cooling venting front or back......Just how accurate does the added mass have to be, calculated weight of glue and actual globbed on are two different things?

It takes a considerable amount of added weight referenced to the driver's moving mass [Mms] to make any major change, so the more accurate the added mass, the closer to hitting a target set of specs. For example:

12" driver/40 Hz Fs/0.4 Qts/60 L Vas has a Mms = ~78.4028 g. Adding this amount reduces Fs/SQRT[2] = 28.28 Hz and Qts increases by SQRT[2] = 0.566, SPLeff. drops by a factor of 4 [~6 dB].

Since the motor will run hotter due to lower efficiency, adding a cooling vent seems a good plan, though if used in a MI app it may not sound 'right' anymore.

GM

**VolvoHeretic** · April 27th, 2012, 08:03 PM

Originally Posted by GM

It takes a considerable amount of added weight referenced to the driver's moving mass [Mms] to make any major change, so the more accurate the added mass, the closer to hitting a target set of specs. For example:

12" driver/40 Hz Fs/0.4 Qts/60 L Vas has a Mms = ~78.4028 g. Adding this amount reduces Fs/SQRT[2] = 28.28 Hz and Qts increases by SQRT[2] = 0.566, SPLeff. drops by a factor of 4 [~6 dB].

Since the motor will run hotter due to lower efficiency, adding a cooling vent seems a good plan, though if used in a MI app it may not sound 'right' anymore.

GM

2.77 ounces? I don't know what MI app means, but it is a base reflex box.

**cradeldorf** · April 28th, 2012, 12:28 AM

Originally Posted by VolvoHeretic

2.77 ounces? I don't know what MI app means, but it is a base reflex box.

MI app = Musical Instrument application. (Guitar Amplifier)

GM · April 28th, 2012, 02:36 AM

Originally Posted by VolvoHeretic

2.77 ounces?

Right, not much in reality in this case, but I said 'referenced to the driver's moving mass [Mms]', which is a doubling of mass. Normally, mass loading is only done to [sub] woofers and of course passive radiators [PRs] where thousands of grams may be added. I've bonded 3/4" MDF discs to 15" woofers to get them down to below 20 Hz.

GM

**Andywin** · April 28th, 2012, 03:13 AM

Yes there is always a trade off with any changes. In this case the reduction of resonant frequency also means a loss in efficiency. As Westrex have reversed the compression drivers in my speakers to use them as dome mid/hi's the loss of efficiency is not a problem. They still require padding down to match levels.

Below are some measured specs of the 2080E driver I found on the web. Specs are pretty good

Model: 2080.E
Thiele-Small Parameters:
Fs: 34.00 Hz
Vas: 149.27 l
Qms: 19.3111
Qes: 0.1998
Qts: 0.1978
Sd: 693.60 cm2
Vd: 0.0694 l
XMax: 1.00 ?mm
Revc: 12.0000 Ohms
ZMax: 1171.7574 Ohms
ZNom: 12.0 Ohms
Bl: 35.8684 N/A
Rms: 1.1093 kg/s
Cms: 0.2185 mm/N
Kms: 4.5767 N/mm
Mms: 100.2717 g
Mmd: 79.2648 g
Levc@1kHz: 2.5270 mH
Levc@5kHz: 1.0722 mH
Levc@10kHz: 1.3017 mH
Levc (Ave): 1.0793 mH
no: 2.8480 %
SPL @ 1W,1m: 96.56 dB
SPL @ 2.83V,1m: 94.80 dB
Measurement Info:
Method: Delta Mass
Added weight: 32.00 g

**kjs** · April 28th, 2012, 06:09 AM

Adding mass to the cone does not only alter T/S parameters and efficiency. Of course it alters sound also. And in case of changing a 2080 by adding the 32g mass ring one will change its attack and sustain tremendously. The hole in the dust cap has not much to do with cooling in case of 2080 instead it prevents compression of air and stiffening of the suspension due to movement.