Jake you still rocking those DIY speakers as well?
Jake you still rocking those DIY speakers as well?
Perhaps attach the GTMat with a temporary method so you can "test" it out? My thought anyway.
Taken from a recent Audioholics reply regarding "Club Polk" and Polk speakers:
"I'm yet to hear a Polk speaker that merits more than a sentence and 60 seconds discussion."
"Green leaves reveal the heart spoken Khatru"- Jon Anderson
"Have A Little Faith! And Everything You'll Face, Will Jump From Out Right On Into Place! Yeah! Take A Little Time! And Everything You'll Find, Will Move From Gloom Right On Into Shine!"- Arthur Lee
Here is another picture of the factory bracing in my 1986 SRS 2s:
Last night I cracked open my SRS 2s again to installed the new GTMat Quadro dampener/foam combo. The deadening mat is about 1/3in thick, and has a decent weight to it. It cuts easily with a utility knife, if treated like any other deadener mat. I had 2 sq/ft of it, and with eight midwoofers, I cut the Quadro mat into eight equal, 6 sq/in pieces. The back of the mat comes with a pressure sensitive adhesive, which was strong enough to grab onto the clean MDF cabinet, but would peel off with a little effort if I ever needed to remove it. Applying the deadener pieces to the back of the cabinet behind each midwoofer occupied about 2/3 of the total surface area. I have heard mixed reviews of how much deadener foam to apply to absorb midwoofer backwave, but the consensus seemed to be that 100% is too much, so 2/3 sounded like a good ratio. Even though the Quadro mat also can reduce cabinet resonance by adding mass, the factory internal bracing in my SRS 2s would seem to make that less necessary than other vintage Polk speakers I've owned. I then wired up all the drivers, replaced the factory roll of acoustic stuffing behind each midwoofer, and mounted the woofers back in the baffle.
As it was late and my family was already asleep, I turned on the most recent sound track of Les Miserables at a low level and sat down for a few minutes of listening. I usually listen to music with the volume turned up a bit, as the additional power seems to bring out the dynamics and detail of these power hungry speakers. Since this wasn't an option, I did an initial listen to see if I could hear anything at the lower volume, until I could do a real listen the next day. I started up the music at a low volume, and to my amazement, the music sounded great! After moving through a few songs, I could hear that I was enjoying all the detail, micro dynamics, and voicing that I was used to! The music was also cleaner sounding and less congested, but the tracks I was listening to were not terribly complex, so most testing on that topic would need to be done. The soundstage was recessed, and the macro dynamics were still lacking, but I attribute both of these to the low power/volume, and I will retest for these again on my next listening session. I also noticed an increase in bass response while listening, and the bass was very full and blended well with the upper frequencies in a way that I previously had not heard at low volume listening. I'm not sure I can attribute this to the installation of the foam deadening mat, but it sounded great none the less, and I will not hesitate to do low volume listening in the future!
For a product that is $13 an sq/ft, I am very happy with the initial increase performance that it gave my speakers. Currently, I would consider it a moderate tweak in terms of performance gains, but it is just one more piece that can increase the overall performance of a great pair of vintage speakers. I can't compare this to a more expensive and purpose development product like NoRez or BlackHole, but it gets my initial recommendation as another tweak in the toolbox of the speaker upgrader/modifier.
For full disclosure, when applying the deadener foam mat, I had already applied deadener to the midwoofer and passive radiator baskets. Crossovers were stock, drivers were original including SL2000 tweeters, and cabinets were otherwise stock.
After critical listening last night with many types of music, and different volumes, and including watching "This Is It", the application of Quadro deadening foam from GTMat increased the overall clarity, decreased decay time of a sound, and aided in reducing muddy playback on very complex passages and songs. Since I only provided 2/3 coverage of the cabinet walls behind the midwoofers, I don't know if adding or removing the mat would proportionally add or decrease it's effect on reproduction, but I am very happy leaving it in place and moving on to other upgrades.
Now, I'll be really interested to hear what happens to these speakers with the two different applications of deadener, once I upgrade the crossovers...
The decreased decay time is something I've noticed by applying any deadening material to any piece, including the electronics. It almost feels like the air is taken out of the music, but in reality I think you're just hearing the sound of the actual gear more accurately than before. The same mod is on the list when I get my Usher's reworked.
Usher CP-6311, Shuguang S200MK, Shuguang S845MK, Pioneer BDP-51fd, MIT Exp1 IC's, PNF Audio SC's, Pangea PC's, Epson 8100
seems like a good ROI
One of these days let's run a test. GTMat vs. NoRez. It's harder to compare Black Hole and 3-layer S.B., because they don't have the damping layer which adheres to the enclosure. But, we could use a layer of the PartsExpress vinyl with S.B. stuck on top it- a "poor man's NoRez." Or, the same thing with a Dynamat layer instead of the vinyl. Or, to heck with the S.B. and just try the damping layer by itself.
We'd have to build a baffle of a given size, mount a driver in it, and stimulate the driver with a given signal, like an MLS impulse. I will have to wire up my accelerometer for use in the measurement software, but I'm going to do that anyway.
After everything is calibrated and a few experiments run to nail down a definitive test, then we should end up with a fairly definitive result.
An alternate test to find the efficacy of Black Hole in comparison to other products would be to build an enclosure, mount the driver, stimulate it, and measure the vibration on the walls of the enclosure at the bass frequencies that the stuff is supposed to isolate the walls from. This could get very expensive, but it would be interesting! Something to think about...
Polk SDA SRS 2
Polk RTA 15tl
Polk Monitor 7C
Polk Monitor 4.6
Infinity RS-II (modded)
Infinity RS-IIIa (modded)
Infinity RS 2.5 x 2
Magnepan 1.6QR (modded)
My friends and family know that in the past 10 years, I've had too many pairs of speakers to count, but everyone who's come over since I've had the SRS 2s have said, "Wow. Those sound great!" I would have to agree, and am very happy I made the jump back to SDAs after a few years.
I'm not sure what upgrades I can get to this week even though I got my new SpeakOn SDA cables parts in, but next week my daughter will be at her grandparents house, so I might be able to get the rest of my upgrades completed; install new caps and resistors, install rings, install new SpeakOn SDA cable and connectors.
Crossover and SpeakOn IC upgrades started because... what better time than now...
Finished the right speaker, and the left one will take me half as long now that I know how to screw things up. :) I forgot that the LP circuit film caps don't fit behind the passive radiator, so I had to make that adjustment. I also didn't realize how impressive installing the SpeakOn connector was going to be, in seriously updating the look and feel of the back of these speakers; combined with new, silver binding posts of course.
The left speaker will be finished tonight, followed by testing to ensure I didn't mess anything up that would create SDA issues. HF boards for these speakers use four resistors and two caps each, and the large MOX resistors mixed with the film caps make for a bit of a puzzle on those boards. I'm very excited to give these a listen tonight and hear what improvements the new crossovers, binding posts, SpeakOn SDA cable, driver basket Dynamat, and GTMat Quadro deadener provide. Rings will be installed this weekend as it's a bit more of an involved project, and original gaskets still seem to be holding the cabinet seal very well.
Pictures to come! Except I can't seem to successful upload them with the forum changes...
Nice! Next up, Dreadnaught!
Good music, a good source, and good power can make SDA's sing. Tubes make them dance.
Use Imgur for pictures.
"He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss the abyss also gazes into you." Friedrich Nietzsche
Got everything finished up last night and went for a listen, but no SDA effect... I'll have to open them back up this weekend to figure out why, but I need to double check the connections on the SpeakOn jacks. I accidentally got a pair of 4-pole jacks, and need to confirm that I soldered the correct two tabs on both sides as the cable and plugs are 2-pole.
Anything else that maybe commonly overlooked to make the SDA midwoofers not play? When I replaced the components on the boards, I did not remove them from the cabinets or desolder the leads from the drivers, so there should be no chance of crossed wires there. I'll also double check the wiring to the binding post for correct polarity, the wires that connect the HF and LF boards, and the continuity of my new SDA cable.
Did some testing and here's what I found so far:
-SpeakOn SDA cable has continuity from left to right speaker, and white wire swapped polarity at SDA connector.
-Connecting SDA results in no change in Dimentional drivers
-With or without SDA cable connected, low level signal comes out of Dimentional drivers
-Sit back and listen, and they sound like good stereo speakers
I'll check all my wiring, soldering, and traces, but I'm currently stumped...
Blue wire of right speaker connects to white wire of left speaker.
Black wire of left speaker connects to white wire of right speaker.
Reverse-polarity speaker wires? If both speakers are reversed-polarity, the SDA is defeated.
Troubleshooting guide: http://www.polkaudio.com/forums/atta...9&d=1268334955
Last edited by Schurkey; 09-28-2013 at 01:17 AM.
Since the SDA connector is located behind/inside the inductor on the back of the cabinet, the inductor body seemed to have been pinching the wires. I rearranging the routing and that seems to have fixed the issues! More testing is coming...
Started to install the rings last night, and I'll going to be a LONG process...
Larry's rings are a great product and design, but all the internal bracing of my 1986 SRS 2s is really screwing up the process. The brackets for the top tweeter go in well, except I have to trim off the bottom of the bracket for the bottom bolt because it hits the bracing. The top mounting holes for the bottom tweeter go directing into the bracing, so I haven't figured out what I want do there. The bottom midwoofers are also mounted right next to bracing, so I will have to cut down the mounting rings there, and the passive radiators have bracing along the top of the opening creating the same issue.
I have everything drilled out except for the bottom tweeters because I'm still figuring those out, and I have a few rings in already, so hopefully I'll be able to get the rest in tonight. My nibbler has been awesome at tweaking the brackets only taking off as little material as I need to get the right fit.
The rings don't have much rigidity. Consider using hurricane nuts instead of rings.
Much rigidity? They are steel rings with threaded inserts? I guess you'll have to explain...
I will have to use the original mounting screws for the top of the tweeters, as there is 4" of MDF behind that's not going anywhere. I cut the tweeter brackets in half, and will be using it for the bottom half of the tweeter. Oh well and they will still be very secure.
Jake, the round ends of the tweeter brackets are designed to be separated from the curved middle section. Just bend the round ends back and forth until the tabs break. I don't know if that will help with your situation, but you don't seem aware of that.
The 4 pole versions are bigger, beefier and spec better than the 2 pole. You got the right ones.Originally Posted by zingo
The hell they don't.Originally Posted by Schurkey
"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 turd by the clean end."
Thanks for the tips Jesse!
I'm current working through each driver and its matching ring to get the best fit.
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