TSW Mid range "blues" + happy ending

[onplane]

Let me introduce myself ... I am among the very few members on this forum who owns a working pair of BOTH AR3a's AND a pair of TSW 610's. Further, I'm the proud ORIGINAL owner of these systems. At one time I listen almost exclusively to the TSW's.  My 3a's just sounded so muffled and lifeless, that I rarely even bothered with them.  That changed about 8 years ago when I completely removed the corroded pots and passively bi-amped the 3a's using just the original three terminals.  Since then, the situation reversed in that I now listen far, far more to the 3a's. Please remember that with the two amps, I can make the 3a's as "brilliant" and bright as I want.

People don't want to talk about mods in this forum so I won't.  Nevertheless, it is a credit to the AR engineers who developed these unique 3a drivers that they are still "singing" after all of these years.  (Frankly, I'm still amazed that the 3a tweeters can compete with the titanium domes in the TSW system, but ... give them more voltage and ... they do!)

Anyhow now for my tale of "blues".  Turned the TSW's on the other day and the left speaker sounded dull and lifeless. Naturally, my first inclination is the source is bad, but by simply switching the inputs that notion was quickly debunked. My next thought was the equalizer integrated into my amp went bad. Again by simply switching the amps that idea proved incorrect. That left the left speaker and sure enough the mid-range driver died (open circuit and no response on the battery polarity test). 

Now this is frustrating!  How is it that all of the drivers in the much, much older 3a's work fine and this mid range is totally dead?

Anyhow, now I needed to find a 6.5 inch, 4 ohm, open back, and hopefully poly cone driver. Turns out there are many of them around. They are used in automotive and home theater systems, but ... which one? So within a matter of minutes I went from despair thinking I'd have to abandon the TSW's, to elation that there simply must be a solution out there .... somewhere??

To make a long story short, this morning I installed a new mid-driver that I purchased from Parts Express (with excellent service from Lisa). Here are the specifics on that driver:

   6.5 inch so an exact fit - even the mounting holes lined up!
   4 ohm
   poly cone, foam surround, cloth spider, open back
   Voice coil diameter - 1 inch
   Rated Frequency range 60 to 8,000 Hz
   Sensitivity - 92 dB @ 2.83V 1 meter on axis

(in the attached pics, the original driver is on the left)

By accident I stumbled upon this particular driver, but from the specs it looked like a decent fit. The X-over points in the 610's are at 700 Hz and 5,000 Hz, so I wanted a driver capable of producing sound in the range of 500Hz to 7,000Hz. Next, the 610 system sensitivity is rate at 90 dB so I wanted driver with a sensitivity exceeding 90 dB.

In theory this driver should be a decent "fit", but as we all know, it rarely works out that way. Anyhow, as I said I installed the driver in the left speaker and spent two hours comparing it to the 610 with the original driver. I'm happy to report I can NOT hear any difference with one minor exception. The original driver appeared to have better dispersion when way off axis (and I mean way OFF). 

Now, I have a 7 stage equalizer and figured I'd either have to cut back or boost the mid frequencies to match the original driver. The speakers sound so similar that to get an exact match, I have absolutely no idea which way to go. (I don't own a high quality mic, so have no way to measure.) In any event, I can't HEAR any difference, so I'm NOT planning to modify the X-over.

I would say that this positive outcome is direct result of the excellent design work done by the AR engineers. Their conservatively designed X-over is so robust it will tolerate minor differences in drivers.

Just to complete the "fix", NOT knowing the new driver would match so well with the original, I purchased a pair of 6.5 inch drivers and installed both. That leaves me with a working original driver just in case I ever come across another original AR mid-driver.

Now for a few disclaimers.  When I say I can't "hear" any difference that is with:

  My old ears
  My room ... and it's set up for the munchkins NOT for audio
  My TSW 610's
  My amp
  My music

Clearly, YMMV!

To complete the story, I'll share a few random observations. To compare the original mid against the new mid I chose Big Band music! Reason for this is most Big Band music is MONO, and it's just full of mid frequencies. (Base heavy music just wouldn't help much when trying to compare the systems with different mid-drivers.) Next BB music often has a large number of different instruments playing simultaneously. What I was particularly listening for was a degradation in "definition". That is the ability to pick out the individual instruments as opposed to a "jumbled mess". Most people say definition is primarily due to a flat frequency response, but I believe distortion plays a significant role in this as well and maybe a more important role.

In any event, I haven't listened to Dish's Big Band music in years and there is some really nice music there! It's the type of music that really showcases a high quality, low distortion system.

Another observation is the sub-enclosure which houses the mid-driver in the TSW-610 is made of wood and it is cylindrical! Why in heaven's name go to the expense of building a wood cylindrical sub-enclosure? Now there is a real mystery. Then another unusual design feature is the mid-drivers are wired out of phase with the woofers in the 610's.

Earlier I complained about the failed mid-driver, but in all honesty if I had to choose a driver to fail, it would be that one! Frankly, I have no idea what I'd do if the 12 inch woofer or the titanium dome tweeter failed.

One final observation on a comparison between the 3a's and the 610's, these systems are similar in design, acoustic suspension three ways; yet, they don't sound the same! As I mentioned earlier, prior to bi-amping the 3a's sounded "dull" compared to the 610's ... and by a lot! That's no longer the case and at modest listening levels (around a watt or two), I now prefer the sound of the 3a's. When I'm in the mood for a more robust experience at higher volume levels, the 610's, in my opinion, really out perform the 3a's. It just seems that it’s so effortless for the 610's to fill the room with sound, while the 3a's on the other hand, appear to struggle. I don't know exactly why that is, but I have some suspicions. First off, the cabinets on the 610's are 30 percent bigger than the 3a's allowing the drivers to be spaced out rather than all jammed together. Next, I've often wondered whether the poly cone drivers just work better when they are pushed harder. In my limited experience, these poly cones just don't sound as good at low volume levels. Now, that is a personal observation and as always, YMMV.

Hope you enjoyed my tale and observations ...

Regards,
Jerry

[michiganpat]

you probably could find a replacement original on Ebay....don't throw out the original, it could just be a broken tinsel lead that could be re-soldered, or you could replace the voice coil....

[onplane]

47 minutes ago, michiganpat said:

you probably could find a replacement original on Ebay....don't throw out the original, it could just be a broken tinsel lead that could be re-soldered, or you could replace the voice coil....

If you look at the pic, you'll see I removed the dust cap in hopes of finding the break.  No luck!

Both the good and blown original drivers are in the Parts Express box in my basement.

I've never attempted to replace a voice coil, but that doesn't sound like a trivial exercise. I assume this would involve replacing the foam surround as well? Then when I'm done, is there any guarantee the repaired speaker will match exactly the other original driver?

[DavidDru]

Great write-up Jerry on a well considered effort. A few folks on here will have additional info for you including sourcing of an original replacement.