I would like to "TL" my 1986 SDA SRS 2's

inspiredsports

GV#27 wrote: »

No the cabinet volume is part the bass tuning,the resistors value is not related to it.It only affects the tweeters response.More resistance =less output.The tweeters output is not related to or affected by cabinet volume because it's diaphram/dome is completey sealed.As for woofers big boxes =greater efficiency.

Thanks! I guess it was just a tweak Polk made that must have made the 1B sound better acoustically.

Systems

inspiredsports wrote: »

Thanks! I guess it was just a tweak Polk made that must have made the 1B sound better acoustically.

Yes it was part of the voicing or balancing of the treble response of the system.

Systems

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Disc Jockey

inspiredsports wrote: »

Did you ever go through with this mod?

I never did the mod as I ended up not purchasing the speakers. WIthout a doubt, though, this was the 1B And I specifically included the model in my e-mail to polk cs

inspiredsports

As mentioned in my post #1, I have updated my SRS 2's with new RDO194-1's, Sonicaps and Mills.

I then acquired another set of crossovers on eBay for experimentation with the intent to move these cabinets a few more rungs up the ladder with the introduction of RDO198-1's.

Disc Jockey, Thank you, a million times, Thank you. I'm sold! I'm going to place an order with Sonic Craft including the 5.8uf cap + 2.7 ohm resistor mod to build out these crossovers for SDA-1B/SDA SRS 2. I could use help with a schematic positioning the 5.8 cap and 2.7 resistor if someone is so inclined.

I know the group concensus is that this only works on the SDA-2B and CRS+ and will let you know how it turns out.

With luck, I will then have an extra 1986 SDA SRS 2 crossover system just waiting for the "TL" mod for sale.

If anyone out there has compared the SDA-1B and SDA-2B schematics, and can see a reason why the a 5.8 cap and 2.7 resistor can't be paralleled into the 1B circuit, please chime in.

NOTE: some above had asked--- this mod, if successful, WILL NOT ALLOW for the use of the AI-1 for non-common ground amps.

inspiredsports

Just noticed Sonic Craft is running their 20% off discount right now making the 5.6uf 200VDC caps (custom valued to 5.8uf) $14.00 each less 20% and the 2.7 ohm MRA-12 Mills $3.85 each less 20%.

I will finally get my wish. SDA SRS 2 "TL's" for less than $40 for parts and less than $200 (4 X $48) for RDO198-1's !!!!! Will then have 4 gently used RDO194-1's and SDA-1B/SDA SRS 2 crossovers for sale to recoup some of the investment.

Systems

inspiredsports wrote: »

If anyone out there has compared the SDA-1B and SDA-2B schematics, and can see a reason why the a 5.8 cap and 2.7 resistor can't be paralleled into the 1B circuit, please chime in.

The 1B already has a 4.4uf and 750pf parralleled with a 2.7ohm res.The 2B does not.

inspiredsports

Disc Jockey wrote: »

I can't help you with the resistor value question but if the crossover circuit is the same as the 1B, you should be able to do this simply. I looked in to the TL upgrade on a pair of 1Bs I ws going to buy, and this is the response I got from Ken (great CS as always):

Hello,
I forwarded your question to Matthew Polk:


"Yes, that modification should work. The 5uf cap, also known as a "By-pass cap", should only be added across the resistor that is in series with the input signal and not the one that is in series with the small inductor.

The inductance of the tweeter voice-coil causes the impedance to rise at high frequencies contributing to a gentle roll-off. The by-pass cap modification allowed us to compensate for that roll-off without disturbing the carefully tuned relationship between the tweeter and the drivers in the crossover region."

Regards, Ken, Polk Audio

The above is what Disc Jockey posted earlier

GV#27 wrote: »

The 1B already has a 4.4uf and 750pf paralleled with a 2.7ohm res.The 2B does not.

The only cap that is "in series with the input signal and not the one that is in series with the small inductor." is the one I've marked in my image and diagrams in post # 53 at http://www.polkaudio.com/forums/showthread.php?t=74946&page=2