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Dahlquist DQ-10

That's a B&W DM-70, clearly confused by one of a pair of nattily dressed Dahlquist DM-10s that showed up the other day.  Don't laugh.  Actually, go ahead, I did.  They look funny and  that pretty cloth could stop a bullet.   These Dalquist speakers and a pile of old NAD components found me when a friend, moving, wanted to unload her late husband's stereo system.    She offered to sell, I said OK, thinking that I'd help her out, sell the speakers, break even, and use the NAD amp and tuner in the workshop.  Never is it that easy.   None of the equipment  was in great working condition, dirty pots, missing buttons, funny noises from the CD player.  And that upholstery!   Ugh.  More projects.

Anyway, the price was reasonable, and I'd already committed.

Design

Something of a mid-fi footnote in the vintage audio world, the Dahlquist DQ-10s (with proper grill cloth) look cool.  I had always thought, based on seeing one pair.. once... in a pawnshop... that they were a poor man's Quad ESL wannabe.  What do I know?   Perhaps I'm being harsh - my apologies to the fanatical.  

Designed by Jon Dahlquist and Saul Marantz,  they are unapologetically large, suggesting that the designers were willing to accept a smaller served market in exchange for performance.  They are kind of a wild design, with no fewer than 5 drivers spread over a large frontal area, giving a retro-cool appearance.   The bottom section is a woofer in a sealed, fibreglass damped enclosure,  The mid and hf drivers are "time aligned" -  mounted on individual masonite baffles, set at varying distances back from what would be the front baffle "plane" in a conventional speaker enclosure.  

As if that wasn't enough, they were intended to be used with a passive sub and crossover, both of which show up on ebay from time to time.  Overall, one would expect a very low WAF!

While DQ-10s aren't highly prized collectibles, they are noteworthy enough to be fondly remembered by many, and they make many recommended ("for their time") component lists.   They have some glowing, mostly nostalgic internet references, particularly relating to imaging,  and are regarded in the audio press as a milestone design.   I have also read that they really require the use of a subwoofer to be fully appreciated.   Unfortunately, any  cult following appears to be very small and there is little information available for those seeking to restore. 

I hooked 'em up and they worked, sort of.  One had very noisy bass the other had less noisy bass.  As expected the speaker surrounds were rotten, one much worse than the other.  I can already tell they require lots of power and which supports their reputation for inefficiency.  (86db apparently, which may even be a stretch)    I can't believe they were designed to be used with tube amps as is claimed on some internet discussion groups.   Doesn't really make sense... such amps would be huge and expensive, and these were manufactured into the 80's, when transistors had long since become the norm.  Anyway, these DQ-10s had been paired with an NAD 2700, 200wpc.  A pair of these amps bridged to 400w each would provide loads of oomph without breaking the bank....

The serial numbers are consecutive, 47478 and 47879, and the woofers magnets are dated June 1983.     You can see the original oak veneered stands.  I also have the original feet.  Notice that the speakers are symmetrical opposites of each other, and  are actually labeled left and right.  Earlier production were not 'mirror imaged" in this way, and this has become an oft recommended mod.    With the exception of C1 - an 80mfd non-polarized electrolytic, the crossovers feature film caps, private labeled for Dahlquist.  Earlier DQ-10s apparently featured more, possibly all electrolytics, which would likely require replacement after a quarter century in service. 

 

Grill Removal and Disassembly.

Removing the grills is easy.   Remove the 2 large phillips wood screws from each side and the four tiny phillips screws from along the rear top edge of the back.   It might be just as easy to remove the cage which protects the drivers and crossover at this stage.  Just a few more little screws.   Pull the grill assembly forward - it lifts right off.  The cloth is clamped under the side trims, so with the grills removed you can remove another 3 screws per side to remove the hardwood (in this case oak)  caps.   Sue had glued the edges onto the metal grills, and the original grill cloth was undisturbed beneath the caps.

Regnar/Dahlquist claims to be the long lost stepchild of the original company, and they reference 3 grill cloth colours on their site: black, polar white, medium grey.  My original grill cloth was none of the foregoing, and was a sand/beige material.    I sent them an email on the subject and never heard back.

Closest to original I found was  Acoustone FR 400 series material, pictured at left.  The original shade is between those two.  It is  available from  www.acousticalsolutions.com  Seems like a good source but you must buy a minimum of 5 yards of material!  Keep looking...

 

I ended up going with simple black grill cloth (http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=260-335)  from www.partsexpress.com  .   Good price, easy to order.  Woofer surrounds are available there too.

New grill cloth was installed with a staple gun and some cardboard shims along the top edge.  It helps to hang the grill over the back of an appropriate chair as  the job is a bit awkward. 

Cleaning

Yuque.  They do get dusty.  Removing the rear cage and doing some gentle work with a paintbrush and vacuum cleaner produces decent results, then a wipe with simple green on a damp rag does the rest.  Mundane, but done, ready for new dust. The surfaces against which the metal mesh cages rest has a foam gasket material, no doubt to prevent rattles.  This stuff had long since rotted and needs replacement.

Woofer Removal and Repair

If you have a pair of DQ-10s which have not had the woofer surrounds replaced, expect that they will need it.  Don't pump up the volume!

 Strange looking driver.  9.5" cone in a 12" basket, difference made up with more masonite.   This woofer was shared with another, possibly better known  speaker model made by Advent .

Make a note of the colour code to the speaker terminals. 

There are a few refurbishment options - replacement of the foam surrounds, reconing (if damaged) and replacement with similar but not identical new drivers.    Costs for the pair range from $50 (parts only) to $300+ for replacments or a full, loving rebuild from Regnar.  (seems totally nuts to me).   Most will only need the foam surrounds replaced.  I sent  the woofers to Santon Audio in Markham to be refoamed and tested   $120 total for the pair.  Not a bargain, but local.  Good guys too, and they did a great job with the correct reverse rolled surround orientation etc.   

Reassembly

The wood on the frames had been splintered a bit when Sue pounded in the carpet tacks to secure the upholstery.  A little methodical clamping and gluing fixed that.  I replaced the foam gasketing around the rear metal screens with weatherstripping material from home depot - 3/8" wide black closed cell foam.  Perfect stuff.  I used a staple gun to refasten the grill cloth, reversed the disassembly procedure.  Easy job.   Below is one of the finished speakers.

 

Listening

I take back some of what I said above.  While they aren't as good as the B&Ws or quads,  they aren't bad either.  In our big living room, they certainly work better than my Mordaunt-Short bookshelf speakers.    I found that the Piezo tweeter sounded awful, so I unsoldered it and the sound improved immensely.  The DQ10s lack the realism of electrostats IMO, but they have decent bass and do a lot of things pretty well.  Using them with a McIntosh MC100 or NAD2700 they can play louder than I need or like.   100 quality watts per channel should be plenty.  Will try with Quad 405 as well.   

The DQ10s will slide right off their stands, so I used a little blu-tack to hold them in place.  

Further experimentation with other components will probably find a suitable combo,  but overall I've been enjoying the DQ10s. 

Does anyone have any technical information, schematics, or original owners' manuals they would be willing to email to me? Please? I will post here for the benefit of others.   Thanks!

 

DQ-10 Tech in no particular order

Here is the DQ10 crossover schematic:

Here is an email thread started by a question from Jim H in New York.

 From: 
Sent: Thursday, December 04, 2008 4:49 PM
Subject: Dahlquist Speakers

 
Hi Dave,

I recently picked up a pair of Dahlquist DQ 10's, and in researching them I came across your helpful site (thanks). I'd like to ask you a few questions, for advice, if you don't mind, and let me say that I am not used to digging into stereo equipment very much.
 
On the front cloth, to replace them,I can see how they wrap around the bottom, but how are they attached once the wood trim is removed on the sides, glue? And I didn't see any screws to give access to how to attach them on the top, you mentioned cardboard shims... how did you do this?

on the woofers, I looked up a few refoaming outfits in the States, and one, watkinsstereo.com, said this:
 There is a small enclosed air space
behind the dome where the air is compressed and rarified as the
cone moves back and forth. The dome's stiffness and it's resistance
to air flow through it are crucial to the amount of low bass. The
dome is also the source of sound in the speakers upper range and
determines frequency response in that area. The usual refoaming
process requires cutting out the dome to gain access to the voice
coil, such that it may be centered in the magnetic gap with shims
during the refoaming process. This destroys the original dome,
requiring replacement with a new and different one, since original
domes are no longer available for older speakers. The only way to
retain original performance is to leave the original dome and its
original attachment to the cone intact. We do this by centering
the coil in the magnetic gap electronically with test tones. The
dome and its attachment are left completely intact and as original,
thusly retaining the speakers original bass and frequency response.
This guarantees the speaker will sound the same as when new.

Does this sound right to you?

I asked them about having to resolder the woofers when I got them back (because mine are soldered in) and they said I could cut the wires 2 inches from the connection and they'd provide a means of reattaching them without soldering... What would you suggest. Did you cut yours, or melt the solder and remove them and then resolder them?

Thanks in advance for your help,

Jim H, NY
 
 

Hi Jim,

 
No problem - but do understand that I am not an authority of any sort.
 
The shims might be more accurately described as wedges.  I rolled the cloth around two thcknesses of corrugated cardboard and used another thickness to stuff that into the groove in the top of the speaker frame.  The cardboard compresses enough to wedge the cardboard/cloth sandwich into the groove.  Make sense?   I then used a staple gun to attach the cloth to the sides. 
 
That theory from watkins may have merit, I don't know.   It all depends on why you enjoy the hobby.   
 
I was an audiophile gear nut for awhile, and was able to notice and appreciate many of the tweaks that I applied, though I was always skeptical about some of the sillier stuff out there.  I take the advice of internet cheerleaders (however well meaning) with a grain of salt.  I do think that the better the gear, and the more thoughtfully designed the room, the more detectable are the improvements, (and deficiencies) especially when you get into REALLY good gear, some of which I own and enjoy.   In other words, IF dq10s are really excellent speakers, and IF every other variable (including the room) is equal to or better than the DQ10s inherent excellent quality, then precisely replicating the original damping and original cone placement may be discernible.  As you may have guessed, I really doubt it is very significant.  These were decent but not super high end speakers and the woofers were cranked out on an assembly line in the days before really good computer controlled equipment was available, (so units probably vary somewhat)  plus the foam itself has been replaced (altering the damping to some small degree) with stuff that - we hope- is of a different formulation than the short-lived originals.  In any case, the material ages and properties change over time.    Also, your couch is in a different place than mine.... ;-)  You get the idea.  I do all the practical things to optimize my system and room, and I have the best gear I can justify, but after that I just relax and enjoy.  If I really want music to sound great I enjoy a glass or two of nice wine while listening.  It is after all, a psycho-acoustic phenomenon.   (My .02, for free, and worth every penny!)
 
Soldering is easy, but you do need to know how to do it.  There is less risk of overheating something and doing damage if you solder or otherwise connect to the wires as you describe, but that is the only real reason to do one or the other.  I have been happily soldering and desoldering wires to speakers since I was around 14 years old and have never damaged one.
 
I had both my dq10s reconed at Santon audio in Markham ON (near Toronto) for $120 Cdn, they sound fine to me.  It may not be too big a deal for you to ship them to Canada, and you now have 20% greater purchasing power WRT the Cdn dollar. 
 
Good luck with the project. 
 
Dave
 

One from Steve