Polk RTA 12 B Overhaul
Comments
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Michael8it wrote: »I think I'm running into the same issue. I am going to go with what the schematic shows and ignore the wire colors I see.
When you took everything apart did you mark all of the wires clearly? If you did try and figure out what the people putting it together meant to do.
Unless someone was messing with the internals of both of our speakers there might be a reason for it. Even a new guy wouldn't just splice a black wire to a white wire.
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I have the schematic and it is pretty straightforward. There is one wire coming off the crossover that mounts to the binding posts that seems like it is reversed... and of course... it's the one I DONT have a picture of LOL.Carver C-1, M-500 MKII, Yamaha HTR-5835, Polk RTA 12BM's (M-for mod'd).
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If I remember correctly the RTA 12b is one of the few, if not the only crossover that does not follow the "black is positive" to the tweeter. My 12's sounded like they were not right, so I checked the schematic, consulted with westmassguy and switched the wires. It made a HUGE difference in the high end. Check this schematic and correct me if I am wrong.
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I knew about the tweeter. The x-Over mounted inside with the binding posts (LFM) seems to have the wires reversed from what the schematic shows. That's what I'm trying to resolve. The schematic shows the black positive wire going through the 0.61mh coil, then to the side where the two 27 uf Caps are connected, then on to the driver. But on my crossover I have the black wire coming off where the schematic shows the white wire should be. That does not make sense.Carver C-1, M-500 MKII, Yamaha HTR-5835, Polk RTA 12BM's (M-for mod'd).
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I can check mine when I have some time to pull things apart, but I would not be surprised if they where wired wrong from the factory or someone fiddled with them . I think if it was me, I would go with the schematic.
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I ignored the wire colors and wired everything based on the schematic, and reversed the tweeter (per the schematic).
Carver C-1, M-500 MKII, Yamaha HTR-5835, Polk RTA 12BM's (M-for mod'd). -
Last but not least... Up and running! Now I'll need to burn them in for a while but even with my half dead Mackey amp they sound fantastic. Now to rebuild the Carver M500... I wait a bit LOL.
Carver C-1, M-500 MKII, Yamaha HTR-5835, Polk RTA 12BM's (M-for mod'd). -
Very cool. Did you put the dacron fill back in?
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Very cool. Did you put the dacron fill back in?
I used new poly fill. The originals had a foam wedge... Yikes. I think I stuffed them a bit too much though. May take some out and see how it sounds.
Carver C-1, M-500 MKII, Yamaha HTR-5835, Polk RTA 12BM's (M-for mod'd). -
I'd be worried that the left speaker could be damaged, it looks like it it's ready to fall off a cliff.
It's got a smidgen of room... plus I added a piece of 3/4" to the bottom of the cabinet, and moved the crossover to the bottom as well. I don't think I will leave them here though. I'm a bit concerned about the heat that stove puts off in winter...Carver C-1, M-500 MKII, Yamaha HTR-5835, Polk RTA 12BM's (M-for mod'd). -
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Not to mention the stove is an acoustic disaster placed between and ahead of the speakers.
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....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 -
Nice woodwork.
I assume you are mounting the tweeter exactly the same as stock since these are a "real time array" speaker? Also I wonder about the fact that tweeters now have a bezel around them with a lip, might affect dispersion.
If the dispersion and tweeter characteristics are altered they will no longer be time aligned and that could hurt the awesome performance of these speakers.
H9
Sorry for reviving an old thread, but got here somehow....
I mean for sure, his work looks great, but my first thought also. Lot of diffraction from back mounting a tweeter that was not meant to be. -
I seriously must have checked out for a few, I missed this.
Those look incredible!! -
He said he took great care to place them exactly where and how they were before.
I have a pair and I think his tweeters look positioned just like mine are.
Most people just listen to music and watch movies. I EXPERIENCE them. -
He said he took great care to place them exactly where and how they were before.
I have a pair and I think his tweeters look positioned just like mine are.
The positioning is fine, but they are mounted Behind the wood, creating diffraction where the tweeter output hits the edge of the wood.
Not the end of the world, but not sure why not front mounted was all. -
Well...I see your point, but the SL2000's plastic flange center opening rim looks to be very close in thickness to his wooden one.
I just looked at mine and my Peerless tweeters are very flat across the flange. No plastic flange.
There's a thread about replacing the domes of Sl2000 with China made ones. One member, @xschop chamfered the plastic bezel opening where it meets the dome. I believe he said it was well worth doing too.
I replaced a bunch of domes also. I tried using caulking to create a beveled lip. My ears are old so I doubt I could tell a difference, but I know the idea behind diffractions.
https://forum.polkaudio.com/discussion/168239/a-real-sl-2000-hack-replace-stock-burnt-voice-coils-with-silk-diaphragm-dome/p1This mod is for TonyM. Fair warning, use a 45° max chamfering tool and don't go wider than 1.325" Total ID and ALL domes including the Wuhans will still seal/seat properly.
These are my testing frames/bezels for a few more mods I'll be doing. Heck, the new inset domes have better side clearance than the factory....
The beginning of the cool dome replacement and a lot of other tweeter improvements by talented machinists.
https://forum.polkaudio.com/discussion/168239/a-real-sl-2000-hack-replace-stock-burnt-voice-coils-with-silk-diaphragm-dome/p1Post edited by Tony M onMost people just listen to music and watch movies. I EXPERIENCE them. -
Hansvelton wrote: »
The positioning is fine, but they are mounted Behind the wood, creating diffraction where the tweeter output hits the edge of the wood.
Not the end of the world, but not sure why not front mounted was all.
The way I see it is that you are no doubt correct but the OP did things that were aesthetically pleasing to him that were not perfect sound wise. Otherwise he would've had the Peerless bezels flush with the wood AND he would've put large bevels or roundovers at the edges like Polk did, to minimize edge diffraction. You can also get a diffraction from the mounting screws and even the gap in the cutout if the bezel isn't a perfectly tight fit.
I think the overall aesthetics are beautiful even if they are compromising sound somewhat.
The OP did lots of things to improve the SQ like updating the crossovers to the later versions which mitigate the combing and lobing effects.
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'm surprised at some of the attention this thread got! To answer some of the questions. yes, one of my main goals was aesthetics, but I did not intend to compromise the sound quality. After reading some of the later comments I see some of the things I could have done differently.
I placed the tweeter behind the mount for aesthetics, but was very careful to make sure the alignment stayed the same. Never considered diffraction from the mount (that's a level of design a few dozen steps above me!). At one time I though about taking a router and smoothing the inner edge but I never got around to it. They sounded so much better after the mods, and I didn't have the time to do any changes.
And now... they are up for sale!Carver C-1, M-500 MKII, Yamaha HTR-5835, Polk RTA 12BM's (M-for mod'd). -
What's next for you?
