Work on a pair of QLS-1

[ducsi]

Hi,
I own a pair of QLS-1 (7001816 / 70018160 ) for some time and some work need to be done.
I have not worked on speaker driver and you might give some hint’s or tips.

<Findings>
Woofer:
Foam need to be replaced on booth driver, any recommendation, source, always / never do.

Midbass coupler:
One is not working, I need to measure by a meter, might be the potentiometer ?
(Waiting for the right tool to unscrew !!)

Dome Midrange:
Any good way to test them and how to clean?

Tweeter:
How to test function?

Potentiometer:
Some are “scratching” better to replace ?

Capacitor:
Do there try out ?, better to replace ?

Sorry if some point’s makes no sense or have been discussed already in the Forum.

Comments are much welcome.

Roland

 

[slimpikkins]

Hey Roland, you found the right place to find info on those speakers. Lots and lots of threads on the problems with the QLS. The pots will need to be cleaned, if you replace them you will need to rearrange the components on the xo as the only new ones are much larger. I would hook the speakers up, play them low, and listen to each driver and fool around with the pots. Mark the "dead" drivers with a piece of tape. The tweeter array can be a pain to get working properly. The mid domes can be fixed. The mid bass coupler most like is the pot which like the others will need removed and cleaned.

I took my woofers Millersound for complete rebuild as it was not just a simple re foam because of some damage to the cones. He can fix the mid domes and tweeters as well. It will get very expensive so you should take some time and search this site for the QLS rebuild threads and fix these up yourself.
http://www.audiokarma.org/forums/index.php?search/9530389/&q=QLS&o=date&c[title_only]=1&c[node]=129

The capacitors in the xo are the least of your problems right now. Most likely they are not the reason the speakers are not working. The ones on the mid bass coupler, bass circuit could be replaced ounce you get the other issues straight.
Jim

 

[chef free]

Nice rare speakers, even more rare auf Deutschland I imagine! You are in the right place for help and information. There are several of us at AudioKarma who have successfully rebuilt these beautiful speakers.

Slimpikkins is right, step one is to figure out which of the 34 drivers work.

The pots are known to get really dirty and cut out sometimes. They are pretty easy to remove and clean however. Make sure the pots are good before declaring any of the drivers "dead".

The soldier buttons on high impeadence tweeters can be reflowed to restore most of them. They should between 3.5 - 4.0 ohms.

The domes can have the wires break. There are no good replacements and used domes are rare and expensive. But they can be fixed!

The "mid bass couplers" are the most common driver. They were used in many different speakers and are available CHEAP.

Check both coils on the Watkins woofer, they should be about 4 ohms and 2 ohms.

These speakers sound GREAT when restored, it's going to be a lot of work but it will be work all the effort! Good luck and keep us posted on your progress.

 

[ducsi]

Thanks guys, I will keep you informed about the progress.
Roland

 

[7.62]

As a former owner I'll share with you, check your crossovers with a fine tooth comb, and your best glasses for ANY loose solder joints / connections. Just one bad connection will shut down a whole bank of speakers in the QLS-1.

Distilled White Vinegar is Your Friend ! for cleaning the potentiometers. I can gaurantee once you get in there your going to find SOME corrosion. Again, one bad one or ANY bad contact point WILL stop all of the emits or midranges from working. If you disassemble them and soak them they will come out looking like new.

That's were I would start, once you have that all checked out and confirmed, check to see if your speakers are working.

Be very carefull testing the midranges, (6). The only thing I can add here is I tried testing one with a direct signal, I used a home avr and put the speaker wires +/- at a very low volume and it blew the mid within seconds, DONE !!!

 

[ducsi]

Thanks for your replies,

Findings Part two:

<1816>
Tweeter: 10 Ohm -> resolder 5,7 Ohm -> ok
Mid Dome: wire brooken -> solder -> ok
Woofer: foam need to be replaced

<1825>
Mid Bass Coupler: crossover capacitor 40uF "open"
Woofer: foam need to be replaced

All driver coils seams ok using Ohmmeter

I was looking for a 40uF / 100V foil Capacitor, found only one with 39uF
2x 20uF parallel, ok ?
Any recomendation, How critical ?
I want to change also on the <1816>

Have a good day,
Roland

 

[slimpikkins]

I used solen caps for the midbass coupler as mine were the red and black leaky ones. 2x20 will be just fine. Looks like you are well on you way to getting them going again.
Jim

 

[chef free]

Wow! It sounds like you are in good shape, very few damaged drivers, that's good news.
Inspect any red and black caps carefully, ALL of them in my pair were leaking, electrolytic caps have a finite life span, replace them.
Nice work on the dome repair, those little wires are pretty tricky to work on.

 

[ducsi]

Hi again,
seams the woofer form I need to order from the US, do you have a recommendation,
found different version for the 12" Watkins woofer.

Looking already a bit ahead, hope not too early, how to power the QLS-1.
Up to now I was using a Revox Amp B251 ( 100W 8Ohm) with a jumper wire to bridge the high/low end with the low end.
I'm reading about bi-amps,
L Channel -> high/mid end R Channel -> low end
this will balance the Amp power supply, any experience ?
This is interest, definitely I want to try using the Revox I have.

Some thoughts:

- get a second Revox amp
- get a 4 channel gear
- use a more powerful 2 channel amp.

Any comment is very welcome, much appreciated.


Roland

 

[tubed]

I'm not recommending any particular seller however here is an example of a surround that may work well.
The most important thing is that a seller should indicate all inner-outer measurements, the innermost diameter being the most important.
The Watkins has a 9" cone so a surround with an 8 1/2" inner dimension will be too small as the edge would overlap the cone too much.
Flat edge for the Watkins.
Measure your particular cones width. Around a 1/4" overlap is okay.
These might work however I prefer the white glue......
https://www.ebay.com/itm/2-Infinity...671245?hash=item3f57c819cd:g:NeYAAOSwxN5WVKu5

You want to use an amplifier that is rated for 2, 4 and 8 ohms.

 

[ducsi]

thanks tubed,
the woofer foarm is ordered including new gasket's
same for the capacitor's.

Time to read more on the amps.

Greetings


roland

 

[ducsi]

hi,

40uF caps arrived and seams working,
new findings.
a 5 ohm pot is rotten.
cleaned and re-assembled I used contact grease, not sure how long it will last.

12" speaker foarm's are stoped at custom !!

 

[ducsi]

progress made,
both 12” Watkins are glued and now drying.

Question:
one driver don’t have polarity marking, are there symmetrical, or better check, how ?

 

[slimpikkins]

To check polarity of any speaker you can use a "c" or "d" battery. Positive to positive, negative to negative the speaker cone will move out. Opposite the speaker will move in. Hope this helps.

 

[ducsi]

thanks slimpikkins, this was easy.

the Watkins are done and back in the QLS,
almost good,
one black outer ring on the 12" must shrunk, I can't get the driver into right position.
any hint ?


Tested one speaker, the sound is great !!

 

[MoreBeer]

one black outer ring on the 12" must shrunk, I can't get the driver into right position.
any hint ?

Are you talking about the trim ring the woofer sits in? If so, I can't see how that could have shrunk? That's not possible.

 

[ducsi]

yes, the black ring, well not shure what happen, anyhow thanks to Grinder (Dremel) it fit now. All good now, have not used the speaker for many years. The sound is phantasic!!
Many thanks for all your support.
Now i’m looking to find a good amp.

roland

 

[tubed]

yes, the black ring, well not shure what happen, anyhow thanks to Grinder (Dremel) it fit now. All good now, have not used the speaker for many years. The sound is phantasic!!
Many thanks for all your support.
Now i’m looking to find a good amp.

roland

Just curious.
What was wrong with the "black ring"?

 

[ducsi]

one ring is smaller in diameter, not realy shure why, years ago a speaker was replaced or repaired, you can see on the poly cone.
I add pictures from the kit.
Playing old CD´s this morning, great !!

 

[slimpikkins]

Nice looking pair Roland. Glad you have things sorted out.