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Thiel CS.5 tweeter replacement

A

allene222

New Member
Bought a pair of Thiel CD.5s for the other room. (CS3.6s in the living room). The tweeters are bad so the guy refunded my money and said I could repair or return, my choice (that was nice).

Impedance across the installed tweeters is about 18 ohms which I assume is the crossover and an open tweeter. Tweeter is Vifa D25AG-68 6 ohm 410.

I can find Vifa D25AG-35-06. What is the difference? Is there another substitute? I don't need perfection, just something acceptable.
 
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Thiel repair says $200 each for new, $150 each for rebuild. Parts express suggested Peerless DA25BG08-06 but didn't have spec on the D25AG-68 and didn't know what the 68 meant. AliExpress has VIFA D25AG-35-06 at $66.28 a pair but takes a month to get here (free shipping).

It looks like the crossover is about 2KHz, which sure seems low. My measurement was with the tweeters removed and a 5 ohm resistor across the leads. Measured with a tone generator, and a voltmeter.
 
No replies here but thinking is that the Peerless DA25BG08-06 are close enough given the price difference on what was a $67 purchase. I re-measured the crossover with my oscilloscope and got 2800Hz this time and the Peerless are pretty flat through 2KHz so hopefully it will be OK. I would love for someone to chime in and give me some confidence here. If it was my 3.6s, I would get the ones from the Thiel repair guy but I can't justify it for what are still unknown speakers.
 
My own experience is with restoring/repairing a pair of Thiel 04a, very different model than yours. But from my own experience, Thiel crossovers are too complex, and small differences in tweeter specs will be Audible. My tweeters were probably modificed Audax HD13d34 for Thiel (the magnets were smaller than actual HD13d34), I used diaphragm/voice coil replacements from Audax's updated version (TW034). Their specs were identical, except the updated version had a resonant frequency 100hz lower. I heard noticeable mid range distortion in certain vocals. I ended up tracking down a pair of HD13d34, and swapping the diaphragm/voice coil into the original magnets, and the results were much much better.
 
It would be very helpful if someone had the specifications on the Vifa D25AG-68 6 ohm. I am assuming they were based on the Vifa D25AG-35-06 but with a lower resonate. The 35's have a resonate frequency of 850 Hz and the proposed replacement a resonate of 721 Hz. That is one thing that gave me hope. But your experience is sobering. I take it you tried the replacements first.
 
Yes, I tried the modern replacements from Audax first, bought them new direct from madisound.

I then tracked down a pair of Audax hd13d34, seller said they came out of a pair of Phase tech model D. The magnets were too big to fit, so I took them apart and transferred the diaphragm and voice coil into my original tweeters. The results were much better, and these are easily the best speakers I own right now.

I documented my repair here http://audiokarma.org/forums/index.php?threads/thiel-04a-should-i-re-cap-them.733504/#post-12085671

What are the exact markings on your original tweeters? Have you tried contacting Vifa and seeing if they have the specs for the Vifa D25AG-68 ?
 
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Wow, I guess the number after the dash is important as that D25AG-09 has no resemblance to mine. Here are mine. (I hope these images show up. New to this forum so not sure how it works)
upload_2019-1-15_7-48-48.png

The Peerless replacement looks pretty flat across the crossover region but it would sure be nice to know what the goal is. It looks flatter than the one linked above that has a lower fs so go figure. Clearly if these were my main speakers I would spend the money and get the real thing. The choice is between the one below for $60 or the real things for $300 for rebuilt ones. upload_2019-1-15_7-50-38.png upload_2019-1-15_7-53-11.png

Vifa was bought by a larger company and their products became Peerless as I understand it but the D25AG line was obsoleted some time ago.
 
The Peerless tweeters came this morning. The connections are in a different location (which I knew before ordering) and one cabinet is modified and a tweeter installed.

I hooked them up and played a tone which I slowly swept. Right around 2100Hz the tone came out of both speakers but when I listened between the speakers there was no tone. I put the + lead to the - wire and now it seemed better but there are still nulls as I move my head around the room at certain frequencies. I was wondering if there was a universal definition of + for speakers. Maybe this is an indication that these speakers are not a good replacement after all or more optimistically that I just don't know how to test them. Maybe some of that is expected given the wavelength of 2KHz. I am really over my head here. Would love some guidance.

The real test will be to take one to my son's house and compare with his CS.5s but I would like to at least get the phase right before I do that.
 
I usually just go with whichever phase gives you more output, that's usually the right way to hookup.

Do you have a measurement mic, and can you run sweeps with REW? That will probably give you the best data.
 
A long time ago I was into this stuff in a serious say and made a pink noise test set with variable band pass filter with variable Q and could test speakers and room resonances. I worked with Russ Riley and Siegfried Linkwitz and we were all into testing and equalizing speakers and of course they went on to make some significant contributions to the area of crossovers. I was planning on using that to test this tweeter but when I took the test set out of the attic the pink noise source just had this huge low frequency sine wave on it so I just put it back. I am not up on how all this is done now. I have lots of pretty good microphones but I would not call any of them a measurement mic.

That said, I just hooked the tweeters up + to + and played our goto test track, "Missing" by Anything but the Girl. I have four sets of speakers. The computer is hooked up Alesis M1Active 320USB which sound crappy. Next is some Alesis M1 Active studio monitors and are the originals so I guess you could call them Mark 1s. They have 6 inch woofers and 1 inch tweeters. They sound very bassy and hollow. At the top are the Thiel 3.6s hooked up to a Classe CA-200. The CS.5 sound most like their big brothers, the 3.6s. Actually pretty hard to hear any difference although I would assume if I could put them in the same room with an A-B switch I would and of course, the 3.6s can play louder and are in a larger room which needs the added power.

Bottom line is I am happy with the Peerless tweeters on the CD.5s

As an aside as long as I brought up Linkwitz-Riley the thing they spent a lot of time testing was the effect of phase vs frequency on music. I recall they had an all-pass filter which only affects the phase of the music. I and others would listen to some music and they would switch the filter in and out basically putting in a 180 degree phase shift across a crossover frequency. Nobody could hear the difference. That led to their crossover design which is basically an all pass filter so that the amplitude is constant vs frequency at the expense of the phase not being constant. This is relevant to Thiels which are phase coherent and try and maintain the phase of the music through the crossover. No harm in doing that but it is not necessary. And of course, it doesn't subtract from the quality of the speakers. I have always described the Thiel coherent design as "unnecessary but sufficient". In other words, if you can reproduce a square wave you have maintained flat frequency and phase basically by definition. You don't need the phase but you do need the flat frequency so they sound good.

Allen
 
The difference in part number probably one is for Thiel, the other for general sale. They may slightly modified from the standard model. But without a spec sheet for the -68 model, there's no way to tell without actually testing them.
 
From all I read and was told, the -68 couple be totally different than the -35. I was specifically told I could not buy a speaker with as low a fs as the -68. I really have no idea but did try and get a low fs both because of this and because the crossover is low and first order. The Peerless is 721 and the -35 is 850. I will say the -35 and the -68 certainly look different.
 
Just curious, what amp are you using to power these? I have a feeling so many second hand Thiels have dead tweeters because of inadequate amplification, exasperated by the poor tweeter protection of 1st order crossover.
 
I am using a Marantz 7200. I think I mentioned that the tweeters were blown out when I bought the speaker. I did not know that when I bought them and the seller refunded my money and said to keep them as he was unaware of the problem as well. I do not know what he was driving them with. The Marantz was sold to my son when he bought his CS.5s and he used them for many years without blowing the tweeters. He bought them from the same high end store that I bought my main system so I know they were a good match. I believe my son did blow out the woofers when his roommates in college kept turning the volume up during a party.
 
I downloaded REW and made a sweep using my Samson Meteor USB microphone. Nothing was calibrated but I figured if there was some huge problem it would show up. I used a 1/3 octave filter so smooth the data as that is what we did back in the day. Pretty mice software. The sweep was 50 - 11000. I can't hear anything even close to 11000 but I wanted to see what the steady state level of the tweeter was so seemed like a good stop point.

I have an AudioTechnics ATR3350 but I seem to need a preamp into my sound card to make it work. I thought I would post now as I don't expect the other mic to be mich different.

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