First impression of The RD 0198 "TL" MOD SDA 2B's
Comments
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I'm already down the rabbit hole of modding/recapping. I don't know if I'll love them but I am addicted to rebuilding vintage speakers because it's getting towards winter and I just love doing it. I'm doing the 2B's and a set of Time Windows in parallel.
The only variable left is why there is a 2.2 ohm resistor rather than a 2.7 ohm resistor. Both left and right crossovers employ the 2.2 ohm resistor so it's not just one side. I was going to replace it merely to get it to 2.7 ohms to match the schematic not for performance reasons. -
I'm guessing F1Nut will know the answer and he's pretty thorough in noticing new posts, etc.
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If you're going to get better resistors get resistors made by mundorf or vishay Mills. Both much better resistors in the sand cast The factory used
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I've hit all the threads that I could find regarding the processes and recommended components. I am more focused on the value of the resistor discrepancy.
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Maybe the polyswitch in yours was a non-standard one that was 0.5Ohm higher resistance than the standard one? You could see what resistance you measure from the + binding post to the other side of the resistor. I think you need to disconnect one lead from each of the MW's to get a desired reading. Edit to add - If the polyswitch has been replaced by a 0.5Ohm already do you have the polyswitches? If so you can measure them directly to see if they are 0.5 or 1 Ohm. I don't know if Polk ever did this. Just trying to think of a solution to your discrepancy.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 -
.Lumin X1 file player, Westminster Labs interconnect cable
Sony XA-5400ES SACD; Pass XP-22 pre; X600.5 amps
Magico S5 MKII Mcast Rose speakers; SPOD spikes
Shunyata Triton v3/Typhon QR on source, Denali 2000 (2) on amps
Shunyata Sigma XLR analog ICs, Sigma speaker cables
Shunyata Sigma HC (2), Sigma Analog, Sigma Digital, Z Anaconda (3) power cables
Mapleshade Samson V.3 four shelf solid maple rack, Micropoint brass footers
Three 20 amp circuits. -
That's a great suggestion and supposition. I'll desolder the poly switch and measure it, I already intend to jumper it as it stands. I would replace it with a .5 ohm resistor as is advised but given that I'm approaching 50 and my high frequency hearing is likely degrading a little more high end might suit my ears better.
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mccarty250 wrote: »I'm already down the rabbit hole of modding/recapping. I don't know if I'll love them but I am addicted to rebuilding vintage speakers because it's getting towards winter and I just love doing it. I'm doing the 2B's and a set of Time Windows in parallel.
The only variable left is why there is a 2.2 ohm resistor rather than a 2.7 ohm resistor. Both left and right crossovers employ the 2.2 ohm resistor so it's not just one side. I was going to replace it merely to get it to 2.7 ohms to match the schematic not for performance reasons.
It's possible that's all Polk had on hand at the time. It's also possible that the polyswitch used has a higher resistance than the spec'd one, although I think that's unlikely. The spec'd polyswitch should be a RDE050A or a RDE090A and should measure about 0.5 ohms. Regardless, it's best to get rid of them and replace with a 0.5 ohm resistor.
That 0.5 ohm difference between 2.2 and 2.7 is very audible. You might consider getting some 2.2 and 2.7ohm resistors to see which you prefer. Use Vishay Mills.
It's extremely rare for vintage Polk serial numbers to be consecutive.
Glue the side panels back on with construction adhesive. They look stupid without them.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 -
0.6 ohms. Probably was triggered a few times and went up a hair in resistance. But nothing outlandish.
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In that case replace with the 0.5 ohm resistor and replace the 2.2 with 2.7.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 -
That was my exact game plan, thanks for affirming it. I was just puzzling over the reasoning for the 2.2 ohm nonstandard resistors.
Final question - what are your thoughts on the horrible MDF side panels? Can I just remove and dispense with them or would that impact some design constraint based around baffle width to where I need to clamp/reglue/refabric them? -
And yes I'm considering TL modding them but only if I can get them to work properly from a spacing perspective in my room and if I love them. If I end up selling them I likely won't recoup my investment in the tweeters on the open market so I want to be confident before taking that step. It's a room full of large speakers so adding more to the mix is illogical - not that I'm highly rational.
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mccarty250 wrote: »That was my exact game plan, thanks for affirming it. I was just puzzling over the reasoning for the 2.2 ohm nonstandard resistors.
Final question - what are your thoughts on the horrible MDF side panels? Can I just remove and dispense with them or would that impact some design constraint based around baffle width to where I need to clamp/reglue/refabric them?
As I previously stated, "Glue the side panels back on with construction adhesive. They look stupid without them."
In addition, if you were to sell them and they didn't have the side panels you just knocked a lot of money off the price.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 -
Crap I missed your entire post on that topic. Good point and agreed. Guess I'll have to pick up some speaker fabric.
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Actually I think there was a previous post where someone just jumpered the poly switch and bumped up the 2.7 ohm resistor to 3.2 ohms, I kind of prefer that solution if you agree that it's valid, they appear to be inline/in series per the schematic so unless there's a compelling reason I might go that route.
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I think that could mess things up if you plan to TL them in the future.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 -
Because the 5.8uf cap i parallel with the 3.2 ohm might present a different slope than a 2.7? Good point and I don't know. It was suggested and approved of in another old SDA 2B TL mod thread that I read.
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YepPolitical 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 -
Yep to it impacting slope or yep to it being a valid method?
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The 5.8uF is in parallel with a 2.7 ohm, not a 3.2 ohm, so using a 3.2 ohm will have an affect. Whether or not one can hear it depends, but that's not how the circuit is supposed to be.It was suggested and approved of in another old SDA 2B TL mod thread that I read.
I guess someone was trying to save a few bucks. They should redo their crossovers properly, IMO.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 -
Resistors are pretty cheap components even for high end ones compared to caps, doing it the right way isn't a terrible cost increase. Thanks for all the advice and clarity on process. I'm going to purchase some new grill cloth from parts express, some liquid nails (or other heavy duty construction adhesive) and re-add the side-boards.
I noticed that the cloth was glued onto the MDF boards not stapled (if stapled it might be hard to get them to re-adhere flush to the sides of the SDA) do you know what's expedient to hold/glue grill cloth like that? I'm thinking contact cement might be the way to go since once it adheres it grabs on good and that you need at least one side with firm adhesion before you stretch/wrap speaker cloth. -
There are a lot of upholstery adhesives out there of which I know very little.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 -
Ditto. I've always used staples due to the lack of knowledge, perhaps someone else can fill our mutual knowledge gap.
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The upholstery adhesive was a contact cement type at a friend's upholstery shop. You had to apply on both sides to get it to adhere. As to what brand I do not know as they bought in huge barrels. All my personal use has always been 3M 77 spray adhesive for car headliners and such. It would work fine for your use. Like any other contact cement you get one shot make it count.
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Thanks for the info all! VSAT88, is that the material to make an pair of SDA's look like a yeti?
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I'm into shag man. Glad you are getting your SDA's all together. I have been hooked on them a while now... Especially the shag set man.
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HAHAHAH if you actually had a set in shag I'd love to see the pictures that rules!
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I can't post a picture of them here on site it might upset @F1nut .
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I can't post a picture of them here on site it might upset @F1nut .
Yeah, may trigger '70's flaskbacks2-channel: Modwright KWI-200 Integrated, Dynaudio C1-II Signatures
Desktop rig: LSi7, Polk 110sub, Dayens Ampino amp, W4S DAC/pre, Sonos, JRiver
Gear on standby: Melody 101 tube pre, Unison Research Simply Italy Integrated
Gone to new homes: (Matt Polk's)Threshold Stasis SA12e monoblocks, Pass XA30.5 amp, Usher MD2 speakers, Dynaudio C4 platinum speakers, Modwright LS100 (voltz), Simaudio 780D DAC
erat interfectorem cesar et **** dictatorem dicere a
