QLS Restoration Tips
Congrats on getting these out and running again buddha6!
Great timing as I just got my pair back in commission for the first time since buying last year from original owner - serial numbers 7001464 and 5. All original drivers including the grey coated Watkins, everything works, but a bank of my mids went out immediately after I got them home and started fiddling with the pots. So, I too rebuilt my crossovers with great results. They sound marvelous again.
There is an amazing amount of info on AK for these speakers - Jim Reeves has been a huge contributor and source of useful info for me and many others to follow.
Here is what I learned beyond the readily known stuff:
>Though Infinity recommends bi amping horizontally (one amp for each speaker to tame the Watkins beasts) the bass can be overwhelming, so bi amping vertically with an amp that can handle the Watkins with gain control may be even better - I'm still sorting my amps, using a Sunfire 300~2 bi wired now but not enough juice when I crank it. buddha, mine drained my Carver TFM42 like a leaky coffee cup! My friend has 2 pairs of QLS and found Carvers were not up to the task, even bi amped. He is running Adcom mono blocks, also has a massive Krell and Parasounds.
>Infinity recommends use of the grilles as there is a diffuser bar between the mids and tweeters. If you run without, you can insert a diffuser for same effect (see Jim's posts)
>Correct position of the speakers is with the tweeters pointed toward the center (50/50 on tweeters inside or outside on photos all over the web); room placement is another topic
>Tweeters are wired in pairs - if one is out, will take the other one out too - check them by listening through a cardboard tube (like empty paper towel roll)
Here is what I learned and did regarding the crossovers:
>Easiest I think to remove the bases and just work on the caps, pots, etc all attached to the base (many posts on how to remove bases - remove woofer, then remove 8 screws, then tap with mallet, use putty knife and they are apart)
>Check your wiring - schematics all over here and really easy color coding to plug into the junction block
My woofers were not properly connected!
>Recap the woofers! Those 2 large cans control the Watkins and I noticed a marked difference before and after. I used Parts Express NPEs and wired together to get the large values needed. Also replaced the other single NPE. I have read that NPEs in the woofers control damping so not recommend upgrading to film, etc. This saves money too
>I did not recap the remaining 5 yellow film caps - in hindsight, probably would do this while in there and you are done for good. Many opinions on whether film caps need to be replaced.......I'm not going there.
>Clean the pots - these things all have dead spots by now. The one that took out my bank of mids actually looked good but would not pass current down the center pole piece. Made of brass, had to drill out and replace with bolt and nut, works fine now. They are tempermental even when cleaned, may be best to replace them all if these are keepers
>Tweeter crossover setting seems best at Low position (subject to your room and taste) but gives most sound from EMITs down to 4K (mine sounded better in Hi or Low versus Mid and maybe because it's been on mid it's whole life and I didn't replace these caps?) Mine seemed to need some warm up time in the middle position then the veil lifted with some juice applied too. In Low they sound great immediately.
I am just now getting them dialed in, but this represents my collective notes from reading and restoring. Luckily, mine had been refoamed and done well, cabinets all very nice, as are grilles. All midrange tinsels in tact, and all EMITs working including the rear (which I have on).
By FAR these are the MOST inefficient speakers I've ever owned. I've had Carver Amazings, Martin Logans, and now have some large 86db McIntosh XR19s, but these take the cake! You need mega reserve, high current power or they will scoff at your gear. But, with the right power, the sound is absolutely rewarding - not veiled, but somewhat laid back; bass is absolutely stunning (my prior Polk SDA SRS 1.2 TL had the crown for deepest and lowest, but it's a tie now); imaging is amazing esp if you can position them right (I can't because I am a horder
; they get loud but easy to listen too.....takes you by surprise, kinda like when the Bimmer is doing 90mph and you think you're legal.
Hope this was helpful for anyone like Bucky too...saw Jim helping you along. I'll post some pics tonight.