Erse SuperQ's or Madisound Sledgehammers for SDA 2B's?

Stew

I've been reading some old posts on inductors such as this one:

http://www.polkaudio.com/forums/showthread.php?t=70124&highlight=inductors

I want to try lower DCR inductors to replace the stock 16 mH inductors in my SDA 2B-TL's for the improved bass response. I don't think my NAD C370 will mind the lower resistance.

Erse SuperQ's are available from Parts Express in either 15 or 17 mH. The Sledgehammers from Madisound can be custom wound to 16 mH. Which one should I order? Will the Erse SuperQ's sound any better than the Sledgehammers? If so, should I order 15 mH or 17 mH? Any advice appreciated!

ben62670

Here you go. I used the Erse. The 15mh is just fine.
http://www.polkaudio.com/forums/showthread.php?t=54561
Ben

decato

I used custom-wound 16.0 mH Madisound Sledgehammer inductors for my 1.2tls.
http://www.polkaudio.com/forums/showthread.php?t=35433

Both Madisound and Erse products are good, and they will definitely bring up the bass.

ben62670

decato wrote: »

I used custom-wound 16.0 mH Madisound Sledgehammer inductors for my 1.2tls.
http://www.polkaudio.com/forums/showthread.php?t=35433

Both Madisound and Erse products are good, and they will definitely bring up the bass.

Awe I thought I was the first to use a low DCR SDA inductor:D
Ben

Stew

Thanks guys! I think I'll try the 15 mH Erse from PE.

ben62670

Good choice;)

Stew

A pair of 15 mH Erse Super Q's arrived from PE a few days ago and I installed them last night in my 2B's. As others have noted, there is a significant improvement in bass. Deep bass is stronger, mid bass has more punch, and bass and mids are cleaner. Well worth $56 and a couple of hours!

ben62670

Congrats on the new coils. Seeing all the money folk's spend on caps you would think this would be a more popular upgrade

Early B.

ben62670 wrote: »

Congrats on the new coils. Seeing all the money folk's spend on caps you would think this would be a more popular upgrade

Huh? Educate me, Ben. It's been my understanding that switching out inductors can be really tricky. With caps you a fudge a bit, but you gotta know what you're doing to change out inductors. Is that correct? Besides, how do you determine the values?

BTW Ben, I'm looking for a reason to mod my speakers again. Just give me a reason. While we're performing minor surgery, you can by-pass the jumper switch on my other speaker. One speaker probably sounds slightly different than the other. :eek:

ben62670

You have the Erse's on the lows;) Yes just swapping inductors can get you in trouble, but these are the SDA inductors that are used between the SDA cable, and the ground. Polk sent me an email saying the SDA inductors can be very low DCR.
Ben

Early B.

ben62670 wrote: »

You have the Erse's on the lows;)

Well, nevermind.:cool:

Give another reason to open them suckers up. I got my screwdriver in my hand and I'm lookin' for some action.

Stew

I added a tube buffer to my system a few years ago in the preamp-out/main-in loop of my NAD C370. Ever since, there has been a "pop" when I turn the system off. It was less if I turned the amp off first.

After I installed the new inductors, no more pop. None! I have no idea why but I'll consider it a gift.

Stew

Curiosity got the best of me and I tried turning off the tube buffer first. Pop's still there. If I turn off the amp first, no pop at all. Before the new inductors there was still a pretty good pop even when I turned the amp off first.

schwarcw

Hi Stew!

Glad to hear the inductor replacement was a success!

Have you tried applying Dynamat to your metal baskets? And using Mortite between the woofer/tweeters/PR and the front baffle? These tweaks are very inexpensive (probably $25 or less - no need for an Obama bailout). I was pleasantly surprised how much difference this tweak made. I was a bit skeptical that I would hear more than a subtle difference. The improvement was more than subtle, I was quite surprised. Two hours and $25 yielded a big return for that investment.

F1nut

Some words from the man himself.

However, I can add these comments. Usually, in a typical low pass crossover, one would not want to swap out an inductor for another one with much different characteristics because it would alter the voicing of the speaker. However, in this case there could be a performance benefit if the amp being used doesn't mind seeing a lower impedance. The inductor I believe they are talking about is part of the "Full Complement Sub-Bass Drive" circuit. That's a term that Sandy coined to describe the system we used to allow the SDA drivers to work in parallel with the stereo drivers in the bass while producing the SDA signal at higher frequencies.

In this generation of the SDA's the stereo drivers were nominally 6.5 ohms and the SDA drivers were nominally 3.5 ohms. The plus terminals of the SDA drivers on each side were connected to the plus amp terminal on that side via their cross-over network. Then, the negative terminals of the SDA drivers on one side were connected to the negative terminals of the SDA drivers on the other side via the interconnect cable. This causes the SDA drivers on the right to produce an R-L signal and the ones on the left to produce L-R. Since bass is pretty much mono in most recordings, if the SDA drivers both get full-range R and L signals they would cancel at low frequencies and the SDA drivers would just sit there acting like badly tuned passive radiators. So, we added an inductor in each speaker between the SDA driver negative terminal and the amp negative terminal on that side. At low frequencies that diverts the signal back to ground instead of through the interconnect to the SDA drivers in the other speaker. As a result, at very low fequencies the Right SDA drivers produce only right channel bass and vice versa, while still producing the R-L and L-R signals at higher frequencies. The transition occurs between about 50Hz and 150Hz.

However, because of the DC resistance of the inductor, the system isn't perfect. I don't recall the DC resistance of these coils but it was high, at least several ohms depending on the model. This means that the SDA drivers will continue to produce some SDA signal even at very low frequencies. Decreasing the DC resistance will definitely improve the bass response of the system both qualitatively and quantitatively. However, before you rush out to buy those Hi-Q replacement inductors be aware of some concerns.

We chose the higher DC air core coils for a couple of good reasons. First, we were always on the edge of acceptability with the impedance of the SDA's. The DCR of these coils kept the minimum impedance high enough for the amps available in those days. Depending on the model, reducing the DC resistance of these coils may take the minimum impedance down to around 2 ohms. If your amp doesn't mind, you shouldn't either. The other concern is saturation of the inductor core. Air core inductors don't saturate. Given the cost of adequate ferrite or laminated core inductors at the time, plus the need for a higher DCR, the air core choice was obvious. So, when switching to a ferrite or laminated core inductor make sure it will handle at least 5 amps without saturation. That's equivalent to 100 watts of low frequency power through the SDA driver.

hope this helps.

-msp

Yes just swapping inductors can get you in trouble, but these are the SDA inductors that are used between the SDA cable, and the ground. Polk sent me an email saying the SDA inductors can be very low DCR.

Yeah, those are what Matt is talking about above.

ben62670

Some more words from the man himself.

...Then, finally, you'll need a large inductor, about 8mh and less than 1 ohm DCR connected from the interconnect wire to the negative terminals for the two dimensional array amp channels. This allows the dimensional arrays to complement the stereo arrays in the bass.

If your amp is non-common ground, let me know and we'll figure out what to do.

Good Luck!

-msp

The stock Polk 16MH are 2.4ohms DCR which are paralleled which yields 1.2ohms, and 8MH. The Erse Super Q's handle 500watts each for a total of 1000watts before saturation.
http://www.parts-express.com/erse-16-gauge-inductors.cfm
Of coarse this would drop the DCR of both coils to .25 which would lower the over all DCR of the system less than one ohm during bass heavy material. He knew how I was wiring them so that is why the recommendation of the single 8mh inductor instead of two 16mh inductors. Not trying to start a pissing match, but just repeating what I was told.
I would not recommend using them in the original 1's, 2's, or the 2.3's with the sub bass drivers without asking Polk first. I did test my meter against a 7.5ohm 1% resistor and it measured 7.4ohms
Ben

F1nut

Huh? Maybe I missed it, but I thought we were talking about factory made SDA's, not those that you made. I mean, you can't compare the two as they are nothing alike.

ben62670

The SDA circuit is the same as all PB SDA circuits. The only thing I can think of is maybe the BB SDA's that are 4 ohms nominal, or SDA's with the sub drivers like the original 1's, 2's, or the 2.3's dip more than he would be comfortable giving a blanket statement saying it is OK to use the low DCR inductors with?

Stew

schwarcw wrote: »

Hi Stew!

Glad to hear the inductor replacement was a success!

Have you tried applying Dynamat to your metal baskets? And using Mortite between the woofer/tweeters/PR and the front baffle? These tweaks are very inexpensive (probably $25 or less - no need for an Obama bailout). I was pleasantly surprised how much difference this tweak made. I was a bit skeptical that I would hear more than a subtle difference. The improvement was more than subtle, I was quite surprised. Two hours and $25 yielded a big return for that investment.

Carl - I have not tried either of those tweaks yet. Maybe a project for down the road.

Conradicles

If my SDA-2B are currently 6 ohms, and I perform this mod, does anybody know what ohm rating they will be afterward?
Thanks, Eric.

ben62670

Just less than a 1 ohm difference in the bass extremes.

Conradicles

So an amp capable of 4 ohms will be fine. Cool.
Sounds like a nice cheap upgrade for the future.