New member - Dahlquist DQ10 questions


Hello gentle people,

im a retired electronics engineer so I now have time to do some repair projects I've been wanting to do. 
I've wanted to get back into listening to my stereo setup and be able to play vinyl again so I resurrected a pioneer pl 50 table and then got to looking at my DQ10's thinking I'd refoam the woofers, check the crossovers, etc. I've owned the dq10's for over 25 years and never did a thing to them but when I got them apart, I found the woofer surrounds to be in great shape, which I thought was really weird. The guy I bought them from mirrored them and I'm wondering if he then coated the woofer foams and that's why they're in such good condition.
I did find one of the 5" mids has a approx 1/4" tear in the rubber surround. It plays ok but I'm thinking the surrounds on both mids should be replaced. 
I've been doing a lot of reading but see no replacements for rubber surrounds for these.
Anyone know of a source?
Also, I'm driving these with a (about to be recapped) quad 405-2, that is driven by a Mac C27. 
Im thinking even after a recap, the quad may not be up to the task. Thoughts?

Thanks very much

ritamacaw
Just got my mids for the dq10's back from Bill LeGall at millersound. They look like new speakers. They're now installed along with new 80uf crossover caps. Did the caps change to the quad 405-2 as well. 
What an improvement!  Speakers sound more alive, better low end as well as much better detail. 

Thanks for everyones responses to my project. Lots of very good information got some good sounds back in my house. 

Michael
I've ordered the 80uf caps for the crossovers.
IME, the smaller the cap value, the more critical the quality. The difference between mylar and polypropylene can be quite astounding.

30 year old electrolytic caps may measure close to their value, but the ESR is likely much higher.

IMO, do it once and do it right. Do them ALL w PP!
Did you replace the tweeters and unplug the super tweeters or replaced both tweeters in each?

thanks,
michael
I replaced the tweeters with Decca ribbons. It made a wonderful change!  
Best

JD
Thanks for that information.
I've ordered the 80uf caps for the crossovers. I may end up replacing others. 

Im thinking after the cap changes in the crossovers, the mid surrounds getting replaced and recapping my power amp, I'm going to just listen to them and not mess with the woofers for now unless I hear some strange stuff out of them. 
Have no idea if refoaming them would make any sonic difference being they seem so pliable after all these years. 
Mike,

I owned DQ10s in the mid 70’s. Mirror imaging is a good thing. Drivers outside in my room back then. YMMV. I like to set coherent speakers toed in slightly so they align about 1 foot behind my head. In a narrow room w reflective walls next to the speaker, drivers inside and firing straight back may be preferred.

Ditto pzo tweeter replacement. IMO, they sound better up off the floor and less angled than the stock feet. Today, I’d add a pair of subs, probably XO ≈60-80Hz, depending on the room. Definitely recap with PP to get rid of the electrolytics, ceramics. I don’t remember the details, but I changed the woofer XO / damping / ???. You might be able to turn up something similar.

IIRC, I had Ampzilla, maybe a big Yamaha, but also listened with several amps belonging to friends. The original 405, APT 1 & other era of similar power drove the DQs easily.

As far as recapping the 405, the service manual is available @ HiFi Engine
https://www.hifiengine.com/manual_library/quad/405.shtml

The parts lists does not indicate the capacitor types. Any ceramic, mylar should probably be upgraded with PP or PS. The WIMA MKP are well regarded PP https://www.tawelectronics.com/wima/WIMA_MKP_10.pdf


-- Al (also a retired EE)
Al, we never ’retire’.
Our caps dry out, our resistors drift, ours tubes fade...
The regular tweeter/mid "block" should be to the inside. Toe in the speaker just a tad.

The HiFi Engine has the manual, mirror image info and schematic.

https://www.hifiengine.com/manual_library/dahlquist/dq-10.shtml




Made contact with Bill LeGall. I'll send the mid speakers out this week. 
What are your thoughts on my woofers being in great shape after all these years? As I mentioned, I'm assuming they were coated years ago and that preserved them. Would you leave them as is?

I hope this doesn't sound ignorant but, when the DQ10's are mirrored, which one is considered left or right?

thanks for everyone's time. 
Michael
If you happen to want to make your own stands, below are some dimensions for making them obtained from Regnar, years ago. I finally retired my DQ10’s this past year after 40 years of faithful service, passing them on to a neighbor.

DQ-10 Stand Dimensions

Top platform: 15" W x 7.5" D
Back Lip attached to top platform: 15 W x 1.5" H
Column posts (in between top platform & Bottom Base): 7" H
Bottom Base: 22" W x 11.5" D
Posts are 60mm square

Mike
Should you not have the stands, I have a pair from mine (when I sold then I guess the guy didn't want them)

If in the NY area they are all yours, happy to give them to a fellow QC-10 owner.
I recommend Bill LeGall at Millersound for any speaker repair.   A true artisan, in a world that is running out of true artisans.
Back in the early to mid 80's The DQ-10 was my reference speaker. As tomic601 states the drivers are of Phillips design, the woofer was made by Advent. I replaced the Piezoelectric super tweet with  a modified  Panasonic ribbon with level control. That improved the highs immensely. Also replaced mylar caps with high quality polypropylene caps. Make sure you get them up on their optional stands instead of the short 4 inch pegs that normally come with the speakers. If you can't find Dahlquist stands, they are fairly easy to make. They put the speaker approx. 12 inches off the floor.
I owned them many moons ago. TAS has them listed number 6 of the 12 most significant loudspeakers of all time!

6. Dahlquist DQ‑10

One should always be wary of pronouncing “firsts,” but, appearing in the early seventies, Jon Dahlquist’s DQ‑10 was to my knowledge the first dynamic speaker to employ multiple drivers in an open-baffle configuration (except the acoustic‑suspension woofer, which was enclosed) staggered for proper time‑alignment and phase coherence, in an attempt to realize the openness and freedom from boxiness that Dahlquist prized in his beloved Quad ESL-57s—with the added advantages of deeper bass and dynamic extension well beyond the Quad. (The physical resemblance to the Quad was both mandated by the design and an intentional homage.) Far from flawless (including conceptually), the DQ-10 was nevertheless a ground-breaking design that preceded dozens of subsequent speakers (perhaps most prominent among them models from KEF, B&W, Spica, Thiel, Vandersteen, and Wilson) continuing up to the present day. Few large, full-range dynamic speakers before or for some time afterward equaled its openness. Paul Seydor

Dahlquist DQ‑10


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I had the DQ-10's as my first speaker.  I drove them with Mac gear (C-28 pre and 2205 Amp).  The amp was rated at 200 watts per side.  My experience was that they really needed a lot of power / current to get to them going.  I don't think you should be shy about getting a lot of power to them, the more the better.
lots of info out there on improving the already good DQ-10. Memory has it w phillips midrange, which should be available or repairable. I would replace the Piezo “super tweeter” for sure, those were obnoxious.
have fun, the quad is a good amp from a legend!
best
jim
Thanks for your response Al, much appreciated. 
I'll checkout miller sound. 

Have a great holiday. 
Michael
Regarding replacement of the surrounds on the mids, contact Bill LeGall at Millersound.net. His repair work on older speakers has received effusive praise from many members here over the years, including me, and he is a delight to deal with.

Regarding use of the Quad amplifier with the DQ10s, I see in the manual for the speaker that its impedance is specified as 8 ohms, and varies over the frequency range from about 5.5 ohms to about 10 ohms. And amplifier power ratings of 60 to 200 watts are recommended for it. The 100 watt/8 ohm rating of the amp falls right in the middle of that range, so I see no compatibility issues. Having no experience with the amp, though, and just brief exposure to the DQ10 many years ago, I can't comment on the sonics that would result.

Good luck, and welcome to the Forum! Regards,

-- Al (also a retired EE)