Interim report on SciFiTom's tweeter experiment
SciFiTom
Posts: 58
FYI Folks,
I now have about 200 hours on the modification I made to try 198 tweeters in 2.3s. I think I like them, so I have ordered the other 3 198s. Admittedly, I didn't try the 194s, as strongly suggested by many, so perhaps I bollixed things up. To my very poor ears, the sound is quite good, and my daughter (chosen for her much younger ears) says she thinks the 198s are working toward becoming a large improvement. Notably, the modified speaker works MUCH better with the Magnepan 1.7s in the system, and such things as string noises from guitars, and the like, are much more pronounced, as with Maggies. I believe the sound is smoother across the range, and the range has gotten wider as compared to the SL2000s. This DOES translate to more rasping in the sibilants, so far. It may have behaved so with the 194s, I don't know. One of the reasons I tried the 198s was that in talking with Polk, the impression I had was that the 194s would be a nearly exact equivalent to the SL2000s, which wasn't quite what I wanted. Yes, that means I changed the voicing, but for me, it improved the intelligibility of vocals, and talking in movies. Sort of a large scale, high quality, hearing aid, if you will.
I don't think I recommend this approach for everyone, by any means. I still have 1.5 ohms in front of the crossover at this point (0.5 ohms of which is in the XO by design, as a replacement for the polyswitch), down from 2.5 early on, to reduce the stridency especially from tweeter 1 (straight 8uf cap in the third-order position). That isn't a good approach, but I am encouraged by the reduction in series "R" I made yesterday. If the tweeters continue to mellow, perhaps I can reduce the resistance more. This approach does allow me to adjust tweeter amplitude (at the expense of impedence match), so starting out hot wasn't all that bad.
I expect a significant error was in replacing the inductors with larger gauge versions, as that lowered the DCR, likely causing me to have the resistor out front now. I took that step so I could revert to stock, if it was really bad, but I didn't find 22AWG inductors on the net (OK, I didn't look very hard). I also did NOT reverse the phasing at the XO, as shown in the schematic. I did try reversing them at the connections, but it was wrong in this application.
If the stridency bothers me when the tweeters get more hours on them, an L-pad, or maybe just a 1/2 ohm resistor after the 8uF cap should solve the problem without upsetting things too much. It really isn't extreme.
I expect to do some damping next, and did use some on the 6511 I had to replace. Some of the more cost-conscious folks may be interested in a material I found at Home Depot. It's U.S. Seal "Instant Waterproof Repair Tape" which is an asphaltic-based, roughly 1/8th inch thick mastic with an aluminum outer surface. It comes in a 6 inch x 25 ft. roll, which should be plenty for anything to do with speakers. The adhesive IS gooey, but not as bad as the Armaflex adhesive, so watch that. I've not encountered the BH-5, or dynamat products, so I have no comparison. That said, it was $16.50 for the roll. Some reviews of the product on the HD website included use as a sound deadener with comparisons to Dynamat (grade not specified) in automotive applications. In their opinions, it performs similarly, and could be used in a double layer to improve its effectiveness. I don't know whether it would work well on cabinet backs, based on a concern for the permanence of the adhesive on particle board, but I pass the info along should it be of use to anyone here. Caveat emptor!
At the recommendation of Westmassguy, et al, I have 18mH Erse Super-Q inductors on order. Now, if I could get ToolFan to sell me at least the PR rings...
Best Regards to All,
Tom
I now have about 200 hours on the modification I made to try 198 tweeters in 2.3s. I think I like them, so I have ordered the other 3 198s. Admittedly, I didn't try the 194s, as strongly suggested by many, so perhaps I bollixed things up. To my very poor ears, the sound is quite good, and my daughter (chosen for her much younger ears) says she thinks the 198s are working toward becoming a large improvement. Notably, the modified speaker works MUCH better with the Magnepan 1.7s in the system, and such things as string noises from guitars, and the like, are much more pronounced, as with Maggies. I believe the sound is smoother across the range, and the range has gotten wider as compared to the SL2000s. This DOES translate to more rasping in the sibilants, so far. It may have behaved so with the 194s, I don't know. One of the reasons I tried the 198s was that in talking with Polk, the impression I had was that the 194s would be a nearly exact equivalent to the SL2000s, which wasn't quite what I wanted. Yes, that means I changed the voicing, but for me, it improved the intelligibility of vocals, and talking in movies. Sort of a large scale, high quality, hearing aid, if you will.
I don't think I recommend this approach for everyone, by any means. I still have 1.5 ohms in front of the crossover at this point (0.5 ohms of which is in the XO by design, as a replacement for the polyswitch), down from 2.5 early on, to reduce the stridency especially from tweeter 1 (straight 8uf cap in the third-order position). That isn't a good approach, but I am encouraged by the reduction in series "R" I made yesterday. If the tweeters continue to mellow, perhaps I can reduce the resistance more. This approach does allow me to adjust tweeter amplitude (at the expense of impedence match), so starting out hot wasn't all that bad.
I expect a significant error was in replacing the inductors with larger gauge versions, as that lowered the DCR, likely causing me to have the resistor out front now. I took that step so I could revert to stock, if it was really bad, but I didn't find 22AWG inductors on the net (OK, I didn't look very hard). I also did NOT reverse the phasing at the XO, as shown in the schematic. I did try reversing them at the connections, but it was wrong in this application.
If the stridency bothers me when the tweeters get more hours on them, an L-pad, or maybe just a 1/2 ohm resistor after the 8uF cap should solve the problem without upsetting things too much. It really isn't extreme.
I expect to do some damping next, and did use some on the 6511 I had to replace. Some of the more cost-conscious folks may be interested in a material I found at Home Depot. It's U.S. Seal "Instant Waterproof Repair Tape" which is an asphaltic-based, roughly 1/8th inch thick mastic with an aluminum outer surface. It comes in a 6 inch x 25 ft. roll, which should be plenty for anything to do with speakers. The adhesive IS gooey, but not as bad as the Armaflex adhesive, so watch that. I've not encountered the BH-5, or dynamat products, so I have no comparison. That said, it was $16.50 for the roll. Some reviews of the product on the HD website included use as a sound deadener with comparisons to Dynamat (grade not specified) in automotive applications. In their opinions, it performs similarly, and could be used in a double layer to improve its effectiveness. I don't know whether it would work well on cabinet backs, based on a concern for the permanence of the adhesive on particle board, but I pass the info along should it be of use to anyone here. Caveat emptor!
At the recommendation of Westmassguy, et al, I have 18mH Erse Super-Q inductors on order. Now, if I could get ToolFan to sell me at least the PR rings...
Best Regards to All,
Tom
Post edited by SciFiTom on
Comments
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the impression I had was that the 194s would be a nearly exact equivalent to the SL2000s
Not even close.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 -
http://www.polkaudio.com/forums/showthread.php?158916-Question-why-Hurricane-nuts-instead-of-Tee-NutsNow, if I could get ToolFan to sell me at least the PR rings...
Hurricane nuts. -
Marantz 1152 DC- Denon DP 1200, Soundsmith Carmen MKII- ADS L980 - Blue Jeans IC's
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Not even close.
Evidently, from your comment, and BKphoto's, I should have asked here instead of at Polk. They literally said the 194s were an exact match. Might have changed my game plan, huh? -
They are a direct replacement, but they sound VERY different.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 -
10-4 good buddy. -
They are a direct replacement, but they sound VERY different.
Aw, there you go with the whole materials science, and electrical versus audible, bit. My daughter and I were having that very discussion just today, about orchestra instruments.
I did ask about the sound when I called Polk. Since I placed two orders for the 198s, I asked the question both times, and got the same answer from two different folks at Polk. Frankly, the first time, I didn't realize how active this forum is. Many of the threads I read before-hand were quite elderly. I have been pleasantly surprised at how much interest there is in these speakers, and how active those with much experience are in helping newbies like me.
Since I listen to quite a bit of classical music, the 198s really aren't too bad (and I probably do use the hearing-aid part). It seems I have a number of mods left as it is, so I think at this point, I'll wait until everything else shakes down to see whether I want to re-do the tweeters (again). Sigh, it wouldn't be the first time I wound up starting over. Anybody need some Magnepans?
F1nut, I do appreciate your comments.
