Quadral Rondo Phonologue Gold repair project

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Gallery Redistributions Renovations


Quadral Rondo Phonologue Gold (or Rondo MKVI) are quality German speakers from the second half of the 90s. Very solid, thick, rear-ported enclosures, nice finish, originally they use a 6” woofer and a quasi ribbon tweeter (like EMIT) – model XX 1000 that’s based on Technics TH 400 “leaf tweeter”. For reference, the earlier version of Rondo (MKV) had smaller front-ported enclosure, smaller woofer (5” I think) and T110/20/2 titanium dome tweeter.

I bought a pair of Rondos for parts. I needed tweeters for my Quadral Amuns MKV (I wrote about that project a few months ago). The description from the auction was actually “I think they work, but I don’t know how to check them properly”, which in seller talk usually means “they’re dead or half-dead, but I’ll pretend that I don’t know that”. But I only needed tweeters (which are VERY expensive and hard to find), so I took a risk.

No surprise, they arrived, and of course only one of the woofers sounded OK. The other woofer distorted, both tweeters were dead silent. But looking inside revealed scorched crossovers and the tweeters turned out to be fine. I quickly installed them in my Amuns where they belong. And they’re worth more than I paid for the Rondos, meaning that all that was left after recovering the tweeters I got for free.

So, what I had left was 2 nice speakers with damaged crossovers, one bad woofer (the other was OK), and no tweeters. But I did have a pair of Quadral T110/20/2 titanium dome tweeters that I had used as substitutes in my Amuns before. These tweeters were originally installed in earlier version of Quadral Amuns, Rondos and many other models. They worked fine in my Amuns without any crossover modification, so I figured they should be OK in Rondos too. Especially that they were originally used in the earlier version of Rondos, and had the same crossover point.

The “to do” list was:

1. Get the crossovers fixed
2. Test the speaker with the undamaged woofer and a T110/20/2 tweeter
3. Get the other woofer fixed or find a replacement
4. Replace or clean grille cloth (it was in a bad shape)

So, crossovers first. It turned out that the components were fine, like I suspected, only the PCBs and tracks were damaged. Previous owner probably pushed the speakers so much that the heat from resistors burned the boards. My tech resoldered the boards around the scorched bit and raised the two resistors that heated up and caused the problem.

Once the crossovers were repaired did a test with substitute tweeter and the one woofer that was working. The sound was fine, the dome tweeter was doing a decent job as a substitute. It did change the character of the speaker quite a bit compared to the original quasi-ribbon tweeter that was originally installed in Rondo Gold, the speaker now had more aggressive, sharper highs. It still sounded very good. The dome tweeters are same width but not as high as the ribbons (about 1.5 cm difference), but I had inserts (wood covered with black velour) that I made to close the remaining opening when I used these tweeters in Amuns. They were a perfect fit here as well.

The next step was to get the bad woofer fixed or replaced. Actually someone already tried fixing that woofer, they just did a crappy job. I was going to send both woofers to the speaker repairman I had worked with before. He would match the new coil to the working woofer. But I got lucky. I found a pair of Quadral woofers in perfect shape locally for about $40. It’s a very similar model – Rondos originally had W170M woofers, I found W170K. Same dimensions, same ring, same impedance, also used in 2 way Quadrals with a 10W higher nominal power rating. They even had magnetic shielding. And the seller said I could return them if they didn’t work well in my Rondos. I picked them up, installed one and compared with the other speaker with working original woofer. As far as I could tell by ear, they sounded the same, so efficiency was a match too. According to specs, the replacement should have a slightly higher efficiency (86 dB vs 87.5 dB). I couldn’t hear it, but even if it did, it was a good thing considering I was using a more aggressive-sounding tweeter. The only difference I could determine were the cones – same material, different finish.

I installed the second new woofer and did some listening and tests. The speakers sounded great at low and moderate volume level. I also did a frequency sweep. Sound was clearly audible from about 35 Hz, and the speakers sounded quite flat from 45 Hz to well above the crossover point. Both replacements (woofers and tweeters) appeared to work fine with the original crossover.

Buying replacements was (probably) a bit more expensive than repairing the damaged woofer, but I had a nice fresh pair, one spare original woofer, and I skipped the waiting and hassle of repairs.

The last step was the grills and enclosures. I cleaned the grilles and “shaved” some pulled threads. They looked much better after that, so I decided not to replace grille cloth after all. I also removed few stains from the enclosures and covered few small nicks with black marker.

For the final listening test I played Santana’s “Dance of the Rainbow Serpent” (first disc) quite loud, and the speakers sounded great! Highs, mids, bass – all there and in the right proportions. As expected, the highs were aggressive, but not painfully, especially with grilles on. The soundstage was not as wide as with ribbon tweeters, but still very good. Bass was nice and tight, despite ported enclosures.

I also did another frequency sweep, with the Rondos placed properly this time (on stands, some 50 cm from the rear wall). Bass was clearly audible at 27 Hz and fairly flat (by ear) from about 38 Hz. The replacement tweeter goes to 25 kHz (according to Quadral’s specs), so the frequency range was probably 40 Hz – 25 kHz. Not bad! Efficiency 86-87 dB, but that’s normal for Quadrals.

The Rondos already have a new home, paired with a vintage Akai AA-5210DB. According to the new owner, in his room they sound best slightly toed out.

Quadral Rondo Phonologue Gold (MK VI)

General information

Manufacturer: Quadral
Model: Rondo Phonologue Gold (MK VI), No. 200690

Years of manufacture: 1996 – 1998?
Manufactured in: Hannover, Germany
Colour: walnut, mahogany, black oak, maple; special order: rustic oak, natural oak
Dimensions: 375 x 226 x 294 mm (H x W x D) with grille

Specifications

Type: 2-way ported system
Woofer: 1x 170mm
Tweeter: 1x ribbon (replaced with 19mm titanium dome tweeter)
Power handling (nominal/music): 50/80 W
Efficiency: 86 dB / 1W / 1m
Frequency response: 45-80000 Hz (original), 45-25000 Hz (after tweeter replacement)
Crossover frequency: 3500 Hz
Nominal impedance: 4 ohms

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