Polk SDA SRS acrylic crossover mod board with Path Audio resistor mounts
magnetichifi
Posts: 10
in Speakers
Greetings all. First, I wish to thank all of the members of this forum for the invaluable assistance and knowledge I have gained here. I am fairly new here and this is my first post.
I hope someone finds my method of resistor mounting and plexiglass bending useful.
Using the idea of other members who used acrylic (or plexiglass) crossover add-on boards, I made my crossover add-ons using a heat bending method to create 90 degree angles as seen in the photos. Then drilled out the sheet to allow for longer bolts to go through the inductors and the acrylic. This makes for a very strong and easy method of affixing the acrylic add-ons to mount the larger caps and resistors. 1/4" acrylic fits right between the original circuit board and L brackets. I used 14ga solid inductor wire to pass up through the acrylic for the Path resistors.
The Path Audio resistors are mounted on TO-220 silver heatsinks. They click right into the heatsinks just like a fuse does in a fuse holder. The heatsinks do need to be filed down a bit, or they will likely cause a little cosmetic damage to your valuable resistors. These T0-220 heatsinks look cool, hold the resistors securely and add cooling to the resistors to boot.
I will try to post more pics as the work progresses.
I have a couple of questions I hope I can get some advice on-
Is solid inductor wire ok to use to extend capacitor, resistor, etc leads?
I am stuck on what kind of wire to use for the 16MH C-Coils. Can anyone recommend wiring for the C-coils? Thank you all so very much.
I hope someone finds my method of resistor mounting and plexiglass bending useful.
Using the idea of other members who used acrylic (or plexiglass) crossover add-on boards, I made my crossover add-ons using a heat bending method to create 90 degree angles as seen in the photos. Then drilled out the sheet to allow for longer bolts to go through the inductors and the acrylic. This makes for a very strong and easy method of affixing the acrylic add-ons to mount the larger caps and resistors. 1/4" acrylic fits right between the original circuit board and L brackets. I used 14ga solid inductor wire to pass up through the acrylic for the Path resistors.
The Path Audio resistors are mounted on TO-220 silver heatsinks. They click right into the heatsinks just like a fuse does in a fuse holder. The heatsinks do need to be filed down a bit, or they will likely cause a little cosmetic damage to your valuable resistors. These T0-220 heatsinks look cool, hold the resistors securely and add cooling to the resistors to boot.
I will try to post more pics as the work progresses.
I have a couple of questions I hope I can get some advice on-
Is solid inductor wire ok to use to extend capacitor, resistor, etc leads?
I am stuck on what kind of wire to use for the 16MH C-Coils. Can anyone recommend wiring for the C-coils? Thank you all so very much.
Comments
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Just use regular 14ga. solid core. If the coating on the inductor wire gets scuffed/scraped you're screwed. Time to start over.
While you're in there replace all of that original clear jacket cable that has turned green. Oxidized copper is not a good conductor.
What's the 15" PR in the box for?Political Correctness'.........defined
"A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."
President of Club Polk -
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Thanks for the reply F1. Copy that on the solid core wire. The tweeter wire is the one mod I see on here that I haven't performed. Couldn't decide on what type of wire to use there either. The PR is for my subs, not the Polk's. LOL
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I like it. Are the bolts non ferromagnetic? Personally I'd prefer aluminum or brass to stainless steel.
You did everything except the tweeter wires? What wire did you use for the other drivers so far?
Many have used Supra Rondo. I'd consider DH Labs Silversonic and Cardas Litz but the Litz is a pain to work with.George / NJ
Polk 7B main speakers, std. mods+ (1979, orig owner)
Martin Logan Dynamo sub w/6ft 14awg Power Cord
Onkyo A-8017 integrated
Logitech Squeezebox Touch Streamer w/EDO applet
iFi nano iDSD DAC
iPurifier3
iDefender w/ iPower PS
Custom Steve Wilson 1m UPOCC Interconnect
iFi Mercury 0.5m OFHC continuous cast copper USB cable
Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
Custom Vibration Isolation Speaker Stands and Sub Platform -
Gardenstater, thanks for your reply. The bolts are magnetic, as are the original bolts. Is it important to use non magnetic bolts?
I did not change the MW wires. I meant I did almost all of the other mods. Thanks for suggesting the Supra wire, I was leaning that way. -
No expert on inductors here, but if Polk used a ferromagnetic bolt inside the air core inductors they must've concluded that it would have minimal deleterious effects at that frequency and I would say you can leave it that way because it may even effect the value of the inductance.
But, and this is just me, I wouldn't go and change the size of the bolt and that looks like a pretty long one to me. How long was the original?
https://www.youtube.com/watch?v=q7lybOaPjNc
I've personally not used the Supra Rondo, just passing on that others have. PVC insulation is not generally favored by audiophiles who are often guilty of OCD perhaps, but it is what it is. Dielectric constant is higher. Why are polypropylene capacitors favored over polyester or mylar ones?George / NJ
Polk 7B main speakers, std. mods+ (1979, orig owner)
Martin Logan Dynamo sub w/6ft 14awg Power Cord
Onkyo A-8017 integrated
Logitech Squeezebox Touch Streamer w/EDO applet
iFi nano iDSD DAC
iPurifier3
iDefender w/ iPower PS
Custom Steve Wilson 1m UPOCC Interconnect
iFi Mercury 0.5m OFHC continuous cast copper USB cable
Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
Custom Vibration Isolation Speaker Stands and Sub Platform -
The new bolts are 1/2" longer than the originals. I can't imagine the 1/2" difference would throw much off. Think I read somewhere the bolt changed the value of the inductor and Polk accounted for that? I could be way wrong on that.
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magnetichifi wrote: »The new bolts are 1/2" longer than the originals. I can't imagine the 1/2" difference would throw much off. Think I read somewhere the bolt changed the value of the inductor and Polk accounted for that? I could be way wrong on that.
It will increase the value of inductance but I do not know how much, and if you're like me you don't have an LCR meter to find out.
You could cut it to the same length or better yet use the original bolts.
On another note, if you moved those silver (aluminum?) TO-220 heatsinks closer together you could get more contact and a better heat transfer from the resistors. I'd space them so that the gap between them was twice the distance of how far from the ends they are spaced.George / NJ
Polk 7B main speakers, std. mods+ (1979, orig owner)
Martin Logan Dynamo sub w/6ft 14awg Power Cord
Onkyo A-8017 integrated
Logitech Squeezebox Touch Streamer w/EDO applet
iFi nano iDSD DAC
iPurifier3
iDefender w/ iPower PS
Custom Steve Wilson 1m UPOCC Interconnect
iFi Mercury 0.5m OFHC continuous cast copper USB cable
Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
Custom Vibration Isolation Speaker Stands and Sub Platform -
The original bolts were not quite long enough to pass through the inductor and acrylic. The mounting bolts for the heat sinks would contact the resistors If I didn't leave the correct spacing.
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magnetichifi wrote: »The original bolts were not quite long enough to pass through the inductor and acrylic. The mounting bolts for the heat sinks would contact the resistors If I didn't leave the correct spacing.
OK gotcha. Can you put a brass threaded insert in the plexiglass and use the originals? Probably doesn't matter.
I see now that the mounting screw's threads extend through the heatsink a little. Could be ground down but ideally you want a heatsink's fins to be exposed to air convection anyway and using them this way doesn't allow that.George / NJ
Polk 7B main speakers, std. mods+ (1979, orig owner)
Martin Logan Dynamo sub w/6ft 14awg Power Cord
Onkyo A-8017 integrated
Logitech Squeezebox Touch Streamer w/EDO applet
iFi nano iDSD DAC
iPurifier3
iDefender w/ iPower PS
Custom Steve Wilson 1m UPOCC Interconnect
iFi Mercury 0.5m OFHC continuous cast copper USB cable
Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
Custom Vibration Isolation Speaker Stands and Sub Platform -
I didn't really plan on the heatsinks acting like heatsinks, just a way to mount the resistors. They do however hold the resistors up off any surfaces allowing for air circulation all around the resistors.
Can you tell me how to properly reply to comments, so that certain people know who I am replying to? Like, your replies quote my comments, but I don't know how to do that. -
Sure. At the bottom of each person's post are a bunch of reaction selections and the 2nd one from the left is "Quote".George / NJ
Polk 7B main speakers, std. mods+ (1979, orig owner)
Martin Logan Dynamo sub w/6ft 14awg Power Cord
Onkyo A-8017 integrated
Logitech Squeezebox Touch Streamer w/EDO applet
iFi nano iDSD DAC
iPurifier3
iDefender w/ iPower PS
Custom Steve Wilson 1m UPOCC Interconnect
iFi Mercury 0.5m OFHC continuous cast copper USB cable
Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
Custom Vibration Isolation Speaker Stands and Sub Platform -
Gardenstater wrote: »Sure. At the bottom of each person's post are a bunch of reaction selections and the 2nd one from the left is "Quote".
Awesome, thanks a bunch! And thanks for all of your help. -
magnetichifi wrote: »Thanks for the reply F1. Copy that on the solid core wire. The tweeter wire is the one mod I see on here that I haven't performed. Couldn't decide on what type of wire to use there either. The PR is for my subs, not the Polk's. LOL
I would use stranded copper wire, no tin plated copper though. The signal travels on the skin and tin isn't as good as copper.
Glad to know the PR is not for the Polk's.Political Correctness'.........defined
"A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."
President of Club Polk -
Tin plated copper sounds excellent, just saying- Not Tom ::::::: Any system can play Diana Krall. Only the best can play Limp Bizkit.
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I used this DH Labs hook up wire. Expensive but no regrets. Making a new wire loom for my 2.3tl's was very tedious. Crimped and soldered all the ends and used gold plated everywhere I could.
https://silversonic.com/products/hookup-wire/ofh-14/ -
I would recommend t14 over hook up wire, similar price point but you can maintain the outer jacket, internal geometry and damping which is a plus- Not Tom ::::::: Any system can play Diana Krall. Only the best can play Limp Bizkit.
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So stranded OFC wire is ok? Or would you recommend Supra wire or the like.magnetichifi wrote: »Thanks for the reply F1. Copy that on the solid core wire. The tweeter wire is the one mod I see on here that I haven't performed. Couldn't decide on what type of wire to use there either. The PR is for my subs, not the Polk's. LOL
I would use stranded copper wire, no tin plated copper though. The signal travels on the skin and tin isn't as good as copper.
Do you recommend wire like Supra or the like, or just good quality ofc wire for the tweeters? Is 16ga correct size?
Glad to know the PR is not for the Polk's.
I knew you were thinking- " I hope he's not gonna try using those PR's in the Polks" Hahaha -
Thank you all for the recommendations.
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magnetichifi wrote: »
So stranded OFC wire is ok? Or would you recommend Supra wire or the like.magnetichifi wrote: »Thanks for the reply F1. Copy that on the solid core wire. The tweeter wire is the one mod I see on here that I haven't performed. Couldn't decide on what type of wire to use there either. The PR is for my subs, not the Polk's. LOL
I would use stranded copper wire, no tin plated copper though. The signal travels on the skin and tin isn't as good as copper.
Do you recommend wire like Supra or the like, or just good quality ofc wire for the tweeters? Is 16ga correct size?
Glad to know the PR is not for the Polk's.
I knew you were thinking- " I hope he's not gonna try using those PR's in the Polks" Hahaha
All I can recommend is to not use tinned wire.
Ya got me...lolPolitical Correctness'.........defined
"A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."
President of Club Polk -
Political Correctness'.........defined
"A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."
President of Club Polk -
Doesn't change the fact tin plated copper simply sounds fantastic, *shrugs*
My entire system is tin plated copper- Not Tom ::::::: Any system can play Diana Krall. Only the best can play Limp Bizkit. -
Thanks for the recommendations.
