New Woofer for an Old Speaker: Infinity RS 2.5

This vintage (introduced 1979) speaker still sounds very good and is readily available today at bargain prices. The innovative Watkins circuit combined with low bass passive EQ in the crossover combine to produce surprisingly extended bass for a 12 inch woofer in a 2.42 cu ft (71 liter) sealed cabinet. Unfortunately, the low Xmax and the fact that the Watkins design allows more current to flow to the voice coils mean bottoming is a problem, especially when used for home theater. These woofers are fairly rare and are expensive to replace.

My solution was to scrap the outdated Watkins woofer and replace it with a modern 12 inch woofer with Xmax suitable for today's music and HT. The MB Quart PWH302 seemed to fit the bill nicely when I plugged the TS data into WinISD. Down 6dB point is point is 27 Hz and Qtc is .730. Sensitivity matches the rest of the speaker at right around 85 dB, and the dual 2 ohm voice coils can be connected in series to match the 4 ohm nominal impedance of the main coil in the original woofer. Not only does it model well, it sounds great! I found one on my local Craigs list for $75 and installed it in the speaker with great results. The crossover to the midrange panels (EMIMs) is 360 Hz and voicing is identical in that region to the original. The problem is this beautifully made, high Xmax (15 mm) woofer is discontinued and extremely hard to find at reasonable prices, so I'm looking for something similar that is both readily available and reasonably priced. I'm considering the Bravox EXS12D-2. It doesn't sim as well as the MB Quart, (the Bravox is the yellow trace) but the sensitivity is within range at 86.4, it's a 2 + 2 ohm design like the MB Quart, and the Xmax is respectable at 11 mm. Best of all, it available at PE Bravox EXS12D-2 Extreme Duty 12" DVC Subwoofer 2 Ohm Per Coi 269-531 for $84.80 including shipping. Any other suggestions before I pull the trigger on a pair of these would be appreciated.


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In this case less is more... :D

But I want it to work with one amp and the stock crossover, and padding down a woofer doesn't make sense...but come to think of it, maybe I could "unpad" the mids and tweets. Hmmm...I'll have to take another look at the crossover schematic, there are some big a** resistors in there.
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The Dayton Audio RSS315HF-4 12" Reference it's just fine.
DAYTON RSS315HF-4, VB = 70.0 L, QTC = 0.754, 85.1 dB/2.83V/m, F3 37.7 Hz free field

2*Pi - 85.1 dB/2.83V/m, 81.2 dB/W/m
Calculated/simulated for the speaker.

2*Pi - 89.2 dB/2.83V/m, 85.5 dB/W/m
4*Pi - 85.2 dB/2.83V/m, 81.5 dB/W/m
Calculated/simulated in open baffle
You can also manage a little control playing with the resistance of the inductor you are using, making it an air core or high resistance or a cored inductor with low resistance.


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