John,
Thank you much for the write-up of the modifications you have done
to your DQ-10s. I have copied the pertinent text into a text file
and posted it in the Files section for future reference by others.
As to my pair, I did some more troubleshooting earlier today and
determined that the piezo is still good on the one (makes noise with
the good ol' meter lead scrape across the contacts), so it's likely
the caps that are bad. As cubdog suggested on AK, this one DQ-10
must've taken one heckuva shock from a dying amp to have two drivers
with burnt tinsels and the capacitors to the other two drivers go
bad.
Interestingly, the resistors also measure about 10ohms lower than
their label on my trusty, calibrated Simpson 206 Series 6. That's a
fair bit greater than the 10% tolerance, so maybe these old
wirewounds don't age all that gracefully. Perhaps future crossover
upgrades will also include replacement resistors in addition to new
caps and inductors.
As I don't have the appropriate capacitors on hand, I followed your
modification suggestion and just disconnected the supertweeter
altogether on both Dahlquists. The treble is a bit suppressed and
definitely rolled off on the higher end -- my guess by ear is around
15-16kHz. When I switched the tweeter leads, the output was greater
(though the roll-off was still present). However, there was a weird
phasing thing happening at the lower crossover frequency where the
midrange ends. It was very subtle and I may have overlooked it were
I not accustomed to other phase coherent speakers, but it was a
detraction and interfered with the coherence of the sound. So, I
returned the meter leads to their previous position and instead
upped the potentiometer to adjust for the reduced output.
To that end, I've figured out why the one working DQ-10 was 2-3dB
louder than the one I've repaired -- someone in the past removed the
adjustment knob on the good '10 and mispositioned it so the arrow
was not in the same position as the other. A very simple issue and
even simpler fix, but I was so obsessing over bad caps and drifting
resistors that I overlooked it for too long.
At any rate, the resultant sound is very pleasant and reminds me a
great deal of the Magnepans that drew me into audio in the first
place (though without the added joys of dipolar sound that the DQ-
10s lack everywhere but in the midbass).
Right now, I'm debating whether it's worth my scrounging up the cash
to completely rebuild the crossovers (nearly broke college student
here) and subsequently be out $100-150. The question is whether such
an outlay of money could be recouped were I to sell these speakers
eventually.
Thanks all for the help. I love trouble-shooting and repairing
speakers and these DQ-10s have been ideal for that (easiest access
to the drivers and crossover I've ever encountered).
- JP
--- In Dahlquist@..., "old.fatboy" <old.fatboy@...>
wrote:
Piezos bad ?let me know-took mine out of the equation on my first
tweak, reverse the polarity on the tweeter and completely
disconnect
the harsh piezo,at the Xover(just clip the lead at the 35 ohm
resitor)
the ScanSpeak 2010 seems to be a standard replacement for the
tweeter-once again with a 12 ohm resitor in parallel.
OK time for the tweak list, this is not all mine but a compilation
from other DQ10 fans must notably DMAN from AudioAsylum ( great
mentor when I began my project)
As for tweaks you can do spending little or NO money, here's a
few.
1. REMOVE the super-tweeter and its associated crossover stuff. On
the
schematic, that's parts labeled R6 and 7, C7 and 8, and L5 (and
the
driver,
of course). this yields a MUCH better top end with less hash in the
frequency extremes.
2. Change the phase of the tweeter. If you find the top end
becomes
rather
edgy after removing the parts described in #1, then try flipping
the
wires
on the tweeter. Whatever gives you the most listenable treble is
the
right
way around!
3. (okay, this costs a bit of money and requires disassembly of the
crossover and most of the speaker system). Add bi-wire capability
to
the
system. as you can see on the schematic (and rather obviously!),
the
crossover seems to be divided between the bass/midbass and the
mid/tweeter
layouts! The lines between C2 and L1 can be split, and L1 and C2
can
be set
up their own + terminals. At the bottom of the schematic, the
trace
between
each set of drivers (line joining the junction of L4, R5 and C6
can
be sent
to the - terminal of the C2 hook up, while the junction of L2 and
the
midwoofer can be sent to the - terminal next to L1's + hookup.).
Got it? I
hope so! I've done this to my system, and it allows me to use a
pair
of amps
(top and bottom, or vertical bi-amping) when I need "crazy loud"
volumes,
which is rare, but still, its nice to have...
4. Restuff the woofer enclosure with "acousta-stuff" dacron
acoustic
stuffing,cheap and helps the bass response.
One lb per enclosure
5. Mirror imaging older non-mirrored DQ-10's.You don't nee a kit
to
mirror image your DQ10's. Just remove the midrange and piezo
tweeter
from the panel,drill out the rivets,turn the panel around,and put
it
back together. then swap positions of the two panels,making sure
to
keep everything aligned properly
6. Stands to raise the speakers up to ear level for the mids and
tweets. Mine are homemade and stand 22".
A link to Frank Van Alstines news letter-magazine ,the Jan 1982
has
info on damping,
Frank is an opiionated old curmudgeon but is knowledgable.
Well thats all folks
John
