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Old 8th March 2013, 04:48 PM   #1
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Join Date: Feb 2013
Location: Philly
Default Need B652 ZAPH xover mod advice

I really appreciate all of these DIY forums and such. Haven't bought any "hi-fi" gear since I was in the military in the 1980s (Sansui B2101 Amp, Kenwood Basic C2 pre-amp, Cerwin Vega PD-9s and PD 6s) so being able to get some good sounds going for so little money is a real treat.

Thanks to the work of ZAPH, I am currently listening to a MUCH better sounding pair of B-652s driven by the DTA-100a amplifier on my desktop. I followed the ZAPH tweaks to the letter--built the crossover, braced with 1/2" dowel as directed, and added poly fill up top.
(with the exception of the added vented port) and it really does take them up a notch.

Of course, this excursion into "cheap" hi-fi ain't so cheap when you gotta buy a soldering station, parts, glue gun, etc. but man, for a quick DIY job it sure pays benefits.

Now, here's a question. I actually have two pairs of these speakers. On my first set one woofer was bad on delivery and PE was kind enough to send a replacement pair of speakers rather than a replacement driver.

So, rather than sit on half a pair of B652s, I bought new woofers and dropped them in.

But, I could not find the same woofer at PE and wasn't sure which woofer would be the best replacement.

I ended up ordering the cheapest 6.5" polypropylene driver they had, this one: GRS 6PR-8 6-1/2" Poly Cone Rubber Surround Woofer 292-426

When I installed that, the b652s sounded better than stock for sure, much better bass even with everything else left as is...

However, that replacement driver has different specs and is 8 ohm while the stock woofer says 4 ohm ( When I ordered it, I assumed the b-652 woofer would be 8 ohm since the speaker itself was 8 ohm, not sure how the speaker is 8 ohm when both the woofer and tweeter are 4ohm?)

I am thinking I am going to apply the ZAPH mods to this pair of B652s as well so here's my question:

Can the ZAPH crossover be used in stock form or do the cap and coil on the woofer have to be changed to deal with the different impedence and such of the new driver?

Or, is the crossover just set for the tweeter and thus whatever is below that is fine with the stock ZAPH parts?

Here is the ZAPH xover for teh stock b652s:

I am guessing "yes,it must be changed" due to the impedence but I have no idea how to address the changes.

Can anyone offer thoughts/assistance?

I really appreciate any thoughts and suggestions.

Specs for the new woofer are as follows:

Power Handling (RMS) 60 Watts
Power Handling (max) 85 Watts
Impedance 8 ohms
Frequency Response 60 to 8,000 Hz
Sensitivity 85 dB 1W/1m
Voice Coil Diameter 1.50"

Resonant Frequency (Fs) 75 Hz
DC Resistance (Re) 7.55 ohms
Voice Coil Inductance (Le) 1.11 mH
Mechanical Q (Qms) 4.32
Electromagnetic Q (Qes) 1.34
Total Q (Qts) 1.02
Compliance Equivalent Volume (Vas) 0.24 ft.
Maximum Linear Excursion (Xmax) 3 mm
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