Piezo replacement in Dahlquist DQ-10

[emaidel]

The most bitterly criticized element of the Dahlquist DQ-10 has always been its use of the cheap piezo super tweeter. Though Jon Dahlquist has been quoted as saying that, since it doesn't even begin to work until 12,000 HZ, no one would hear the difference anyway, that hasn't silenced the flood of critics who find the use of such a cheap driver in such a fine loudspeaker nothing short of audio heresey.

Not long ago, I had to replace one of the piezos in my DQ-10, and found a Chinese-made unit from Parts Express for an astonishingly low price of only $1.44 (as opposed to the ridiculously high price of over $26 for a "factory original" from Regnar, in NY). After installing the new Chinese super cheapie, I was unable to detect any sonic differences between it, and the still-functioning original. Still, to have such a cheap driver in these speakers which I respect and admire so much never sat well with me, and so I started an online search for a different, replacement super tweeter. I found, and purchased, a pair of Eminence APT-80 units from Parts Express, for roughly $25 each.

The Eminence drivers have a superficial resemblance to the piezos in that both have plastic diffusion lenses, with identical mounting dimensions, but the similarities end there. The Eminence looks to be a compression driver, with the attached lens, and a substantial magnet (about 1 lb. - a lot for a tweeter) that dwarfs the lightweight peizo.

And so, once again, I disassembled my DQ-10's (a not too difficult, but tedious procedure), unsoldered the leads to the peizos, and installed the Eminence drivers. The results are pleasant, but not at all what I had expected.

Even placing my ear directly up against the driver (and this was the case with the piezo as well), I can't detect anything coming out of it. If I place my hand over the regular tweeter, I still can't seem to hear anything coming out of the super tweeter, but if I place my hand over both the tweeter and the super tweeter, then there is a decidedly different tonality to the speaker system.overall. Whether this is due to the super tweeter operating, as Jon Dahlquist has been quoted as saying, only above 12,000 HZ, I can't say. It sounds more to me as a lower treble "fill" than upper-end sparkle, but then that may be that the crossover is that effective at sending only super high frequencies into the unit, and the result isn't necessarily more "sparkle," but "air" and "openness."

That which matters though is whether or not the Eminence drivers made any worthwhile difference. The answer to that is, "yes they do, but it's not night and day." Given that, even though I'm pleased with the results of having replaced the cheapie piezos, I'd have to say that Jon Dahlquist knew what he was doing when he used them in the first place.

On another note, I have to give kudos to Parts Express for their incredibly expeditious shipping. I paid for standard, Fedex rates which stated "2 to 5 days," but received my tweeters in only one day!

[Feanor]

The most bitterly criticized element of the Dahlquist DQ-10 has always been its use of the cheap piezo super tweeter. Though Jon Dahlquist has been quoted as saying that, since it doesn't even begin to work until 12,000 HZ, no one would hear the difference anyway, that hasn't silenced the flood of critics who find the use of such a cheap driver in such a fine loudspeaker nothing short of audio heresey.

Not long ago, I had to replace one of the piezos in my DQ-10, and found a Chinese-made unit from Parts Express for an astonishingly low price of only $1.44 (as opposed to the ridiculously high price of over $26 for a "factory original" from Regnar, in NY).
...

Wouldn't make a difference to me. :( I'm deaf above 10 kHz; (I've tested this with test tones and SPL meter).

What's the DQ crossover for the primary tweeter? Just a wild notion, but maybe you could replace the primary and supertweeters both with, say, a ribbon like this Aurum Cantus (http://www.parts-express.com/pe/showdetl.cfm?Partnumber=276-400). That would make a real difference.:23:

Alternatively you could keep the primary and replace just the super but preferably drop the crossover down to something like 5000 Hz.. Of course the form factor is different and a lower crossover would need some calculations.

[emaidel]

Thanks for the suggestion, but one thing I've never been dissatisfied with is the tweeter or midrange response of the DQ-10's. I might look into something like that ribbon tweeter when, and if, the drivers blow.

[hifitommy]

there were mods for the dq10s that included ribbons as replacements for the piezo (?randall research). i am sure a satisfactory ribbon can be had for much less than the one in the link.

its possible that people are just appalled at an inexpensive driver like the motorola piezo is included in a state of the art design (the dq10 was just that) even if it fit the bill.

of COURSE i would be prouder of one with a ribbon but perhaps without a valid reason. having a complete transmission of all available frequnecies is conducive to better frequency and transient response in a given loudspeaker.

well, here is a quote from a stereophile review of a bryston 3b amp:

Footnote 1: The Dahlquist DQ-10 was introduced about the same time (ca 1975) as the original Bryston 4B. Like many Brystons, my DQ-10s have survived the intervening decades, but not without modification: a Randall Research modification kit replaced the piezoelectric tweeter with a ribbon driver; all capacitors in the crossovers were replaced with polypropylene film types, with much guidance from Walt Jung; and, after the Bryston 3B-ST turned them into dust, Miller Sound re-coned both woofers. The good news is that these changes have increased the speakers' power-handling capacity, and made them faster and more dynamic. The bad news is a loss of the soundstage depth found in the stock factory design.—Larry Greenhill

so perhaps the piezo isnt so bad.

and i think it was carl machisoto (now of NOLA) that did the design for jon.

[Mr Peabody]

You might try a test tone the goes 12k or higher or a frequency sweep off a test disc to see if you hear anything. If you have the old CD Carver gave out with a listen to the Amazing loudspeaker it has some upper frequency tracks. It sure would seem there ought to be more program in that region. But even if not to cover those frequencies for harmonics can be important.

I remember when the full range truckbox speakers came out using a woofer in front and a Piezo on top. The Piezo sounded like hell but were virtually indestructible.

[emaidel]

There is no doubt that something is coming out of the super tweeters, whether the Eminence units or the piezos. As I stated, after covering up the tweeter with one hand, and then the super tweeter with the other, there was a very noticeable difference in the overall sound of the speaker. When I placed my hand over the super tweeter, the preponderance of sound then seemed to be coming from the woofer, but after moving my hand away, most everything seemed to come from the panel with both the super tweeter and the mid bass driver.

Also, after extended listening, I find the overall sound of the DQ-10's to have improved noticeably since installing the Eminence super tweeters, though the degree of improvement varies from one source to another. On well recorded discs (CD's or SACD's), there is now greater upper-end detail, and a smoothness to strings and, in particular, voices. The speaker is by no means brighter, but just more listenable.

I guess it would be worthwhile to test my hearing, as I'm soon approaching that day when I'm elligible for Medicare - 65. I think I still hear very high frequencies, but I'd like to know for sure.

[Mr Peabody]

Ah, got it.

I was at the ENT a year or so ago and they tested my hearing as a routine thing since I couldn't remember it being done for years. I was very interested in what frequency any drop off may have happened. They told me my hearing was good but the test was only a certain frequency range, I can't remember what it was, something like 500 Hz to 10k maybe. I asked about testing range and they told me they only test the range they did because that's where vocals and most noises occur. I wonder if that's typical? They weren't even going to entertain the idea of letting check my range.

[hifitommy]

usually only go to 5kHz!!! the medical community doesnt give a rodent's derriere about whether we can hear all musical signals. only speech and normal sounds.

if you want to see if the piezo or replacement ribbon driver has ouput, put on a sterephile test cd or even better, the rives disc. then put your ratshack or other SPL meter at it face. you will very likely see a response from the meter even if YOU cant hear it.

i tried that with one of those ultrasonic 'animal training' sound generators available in the junk catalogs and it was amazing how loud it showed the output to be. i also have no doubt that emaidel/Aging Smartass is correct in his assessment of the sound when covering the piezo. the very high frequencies are part of what we perceive spatiality from. sometimes we identify that as 'air'.

[wedmiston]

I agree that it's always seemed odd that such a design coming from Jon would include an inexpensive driver like the piezo. Having said that, I always come back to a few notions regarding the DQ-10:
1 - If people were willing to shell out $1100 a pair back in 1976, Jon could have easily put in a more expensive driver and upped the price another hundred I suspect.
2 - Having spent so much time designing both the driver placement, baffles, alignment and crossover, it strikes me a self-defeating for him to include a crappy driver unless it was justified
3 - Finally, Jon was generally considered a pretty brilliant guy when it came to speaker design. I don't find myself in an "equal place" to question his design decisions, especially when he had Saul Marantz greenlighting and bankrolling most of his ideas with his name associated with them.
4 - The design of the 10 just BEGS people to tinker with it...been happening ever since it was introduced. That doesn't mean it SHOULD be tinkered with.
5 - Since the DQ-10 was essentially a hand-built unit, changes could have been made in relatively short order..but weren't

In the fairness of disclosure, I too have had to occasionally fight the urge to mess with some aspect of the design, but other than upgrading the caps and refoaming the woofs, I avoid it, because I always question as to whether the $ spent will result in any perceptible (critical) difference.