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Dahlquist DQ-10


Deang
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It started with an email from Dave (Gothover). Now I have three other emails about my work on this speaker. I can't find a thread anywhere, so I can't figure out what's sparking the interest -- so I guess I'll start a thread.

The biggest problem with restoring these is dealing with the 4" Phillips midbass driver. The rubber surrounds are usually dried out, and they are prone to cracking and splitting -- often not obvious by just looking at them. Wet a Q-tip with Armour All and gently go over the surround. Don't saturate the Q-tip, you don't want the Armour All running down over the paper driver. Do this three or four times until they are clean and "reconditioned". As you are moving the Q-tip over the surface, gently press down and look for splits in the material. If you find any, you will have to send them out to Orange County Speaker repair. I think they do this driver now, but didn't back when I was doing my rebuild. Call and find out, and if they do, just have them reconed along with the surround replacement. When I did mine, I was at the mercy of eBay, and it took four tries before I got a pair acceptable for use.

The pot in the back must be replaced. You will have to remove the woofer and all of the batting to get to the pot -- make sure you put it back exactly as it was before you pulled it out. I could not find replacement pots, and had to use Regnar. Don't use these people for anything except the pots. They rebrand off the shelf stuff and mark it up 300%. For example, they charge $10 for a few feet of rope caulk. If you are forced to buy a replacement drivers, get ready for sticker shock. If you find a source for the pots, please let me know.

Crossovers are always in bad shape, and should be rebuilt. At the very least, replace the electrolytics. If you have a very old pair, then all the caps will be electrolytic (later models used Mylars). Older models also weren't mirror imaged,. You can fix that, but it ain't fun work.

The vinyl on the bass bins is usually shot and the adhesive is starting to bleed through. On the three pair I restored, I heated it up with a heat gun, peeled it off, and replaced it.

If you have to redo the surrounds on the woofers, just buy the surround kit for the Original Old Advent.

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Guest David H

The biggest problem with restoring these is dealing with the 4" Phillips midbass driver. The rubber surrounds are usually dried out, and they are prone to cracking and splitting -- often not obvious by just looking at them. Wet a Q-tip with Armour All and gently go over the surround. Don't saturate the Q-tip, you don't want the Armour All running down over the paper driver. Do this three or four times until they are clean and "reconditioned". As you are moving the Q-tip over the surface, gently press down and look for splits in the material. If you find any, you will have to send them out to Orange County Speaker repair. I think they do this driver now, but didn't back when I was doing my rebuild

I didnt have any luck finding a source to repair the driver 4" driver either, so I replace the suspension myself using the Bose 901 kit. In order to use this suspension kit you must carefully trim approx 1/16 inch from the drivers 4inch cone.

post-24405-13819636400662_thumb.jpg

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Guest David H

I wonder how the TS parameters of the driver are effected by doing that?

I suspect no more than having the driver re-coned with a comparable part, and certainly better than changing to a different driver. My preference would have been o/e suspension.

Dave

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Recap article. The crossover changed over time. Various resistors were added in parallel with the woofer, fuses added, cap values changed, etc.

There is a small discussion group on the Classic Speaker pages about Dahlquist, and a very active Yahoo group on the DQ-10. That latter group is where the action is in driver replacement.

What taper is the HF contour pot? If it is a linear taper, then 25 ohm linear pots, rated 5 or 10 watts, are plentiful. They can often be found in old tube gear, including test equipment.

DQ10 recap.pdf

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Nice articles. It's always interesting to read and see the different ways people tackle this beast.

The most popular mod is to replace the Phillips tweeter and dump the piezo. I just went half-way with that. The DQ gets a little harsh when pushed, and blame for this is normally put on the piezo. However, people who modify the network and get rid of the piezo find out that it's really the Phillips tweeter breaking up. Back when I was doing these, the ScanSpeak was the driver people were using (with a 12 ohm resistor in parallel) -- I have no idea what they are using now since the D2010 isn't available anymore.

I rebuilt my friend's pair last year, and he's using a pair of Adcom GFA-555 II amplifiers. He wanted them stock, so I just did the crossovers, wiring, and pots. He thinks they sound fantastic. I think they sound like fingernails going across the chalkboard. It has to be the amps, because it sure ain't my crossover work. :) It's very hard to go back to that kind of sound after years of exposure to high efficiency/low distortion loudspeakers. OTOH, he doesn't care for the sound of my loudspeakers -- I guess they just don't screech and thump enough. :)

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Guest David H

I have no idea what they are using now since the D2010 isn't available anymore.

Looks like Madisound still has the Scanspeak in stock.

ScanSpeak D2010/8513 20 mm Dome Tweeter
Madisound# D2010/8513
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post-24405-13819636642202_thumb.jpg

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Guest David H

I have been having a ball with these old Dahlquist, they're not by any means perfect, but still comparable to speakers built today. I built my subs into the stands using Dayton Titanic MkIII's. Reall a nicely built drivers, and operates in a 1cu ft box.

I still need to add the wood trim to the stands and the grill, but it's a good start.

Dave

post-24405-13819637005998_thumb.jpg

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