Richard
My piezos work but I can not hear them with the crossover and by themselves. I can hear the difference when the supertweet is disconnected. The reason -the ST is partially out of phase with the tweeter and hence CANCELS some response from the tweeter in the crossover region. See the response below taken at the listening position, some 8ft way, which is at at the DQ10 sweet spot. The sweet spot is VERY small and is the axis at which all the drivers are in phase and sound the best.
The orange is without the ST, the red with.You will see a dip of about 3dB at 13.5kHz WITH the ST. You can also see the ST response rises above15khz so it not only partially out of phase it is also too hot.
If you unbolt the ST and move it forward this dip goes away at some point BUT since the ST is now sticking out of the baffle it creates diffractions in the response of the other drivers.
I believe it best to just eliminate the ST and go with a tweeter that has extended high frequency response.?

FWIW running the piezo directly from the amp is not valid test of a DQ10 deployed ST. Without a crossover it will have response down the low kHz range which I hope is audible to all of us. It does prove they are working though.?

Leif
Greetings. Can you measure those drivers rather than sending them?I am afraid the cost and danger to ship them would be too great. If you can measure an impedance as well as on axis repose taken at 1M would be great. If you have REW the raw MDAT file is best so I can post-process it.?
Thanks.

Samuel
Thanks for the feedback. I don't have an easy way to generate polars with accuracy. Since the drivers for the most part are of similar size and/or have similar polar responses within the region of crossover and I don't plan on altering the driver placement or crossover any more than is necessary, knowing the exact polar response is of secondary usefullness.

You comment on ferrofluid in the DT94 is interesting. While I have heard for years it negatively impacts sound, can you describe what it does to the sound, or perhaps provide measurement. my main concern removing it is that this may not be very reproducible or something many people want to do. I would be interested in giving it try though. I am also concidering the Tymphany?D19TD05-08 though that would require a 2-3 element impedance compensation network.

The OEM mid are the tough ones to replace. If they and tweeters were not so stiff due to drying adhesives and coatings I would just leave them alone. ?One of my tweeters and mids had failed voicemail leads that were repaired. Can you confirm that both the properly functioning mids and tweets have dual impedance peaks, like vented enclosure?

we
Good feedback and questions. Right now my intent tends towards between A and B with focus on fixing a few of the problems I have identified. This was a breakthrough design for its time and want to honor Jon's design intent. That having been said I believe some things can be improved. The most obvious is the elimination of the Piezo Super tweeter.

C right now is unlikely as to do this right would require a fresh start from scratch.?

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Hi Charlie?

Charlie - first off, this is a great undertaking and interesting to follow, thanks!!! I am curious as to your goal...is it to:

1. Find current day, equivalent (new condition, closest match to original specs) replacements for original drivers, or (refresh the speaker)
2. Find drivers that might deviate in design (for the better) from original drivers (goal is to improve speaker BUT also control costs and minimize Xover mismatch)
3. Go all out and find the best options for each driver (cost less critical, performance and specs rule) (goal is a "new and improved" DQ-10, no limits)

If you liken it to guys who restore cars, some are purists - they must replace everything with as close to original as possible to honor the goal and design of the original, and only deviate when ts absolutely necessary. A noble pursuit and I (for the most part) lean that way. If you start to wander too far from the original you're progressively abandoning the whole reason for owning that speaker in the first place. On the other end (C), there are some who feel the original drivers are now (and maybe always were) inferior to those currently available, and seek to "upgrade to improve" on the original design. Option B is somewhere in the middle...improve what we can....accept what we can't, maybe?

Also worth pondering...I suspect Jon and Saul could have fitted the 10 with more expensive, esoteric drivers, but mass manufacturing limitations at the time, along with selecting widely available components that allowed them to turn a profit and achieve a sustainable margin. These parts also had to be durable and reliable so they didn't have people complaining of failures. Since the 10 was a mass-marketed product, all these elements factored into their ultimate design choices. I'm always reminded that Jon was designing a "Quad ESL for the everyman."

But swapping old for new isn't always a taboo thing. As long as a driver syncs with the original in "design and intent," but over time has become even better performing and maybe even cost less (think any electronics over time), then it seems reasonable (and possibly smart) to consider those components. But realistically, I doubt many owners today would seriously consider dropping $225 for a tweeter to replace one that cost $35 back in the day, for a speaker that only fetches $500-600 a pair in the resale market. I could be wrong, but I wouldn't do it. Not saying you're considering this....just saying that if the goal is to identify drivers that are cost-effective substitutes, then the two you suggest might be good options (performance aside for now). IMO, the real value-add of your effort is helping those of use who own a pair (or in my case two) and eventually want or need to replace a driver, have a list of objectively-evaluated and tested comparables to work from without have to do massive retooling of the Xover.

I don't think there's a "right" approach. Regardless of your choices the debates of "this driver vs that one" will rage on anyway. But many of us not schooled in engineering will find your mission quite interesting and useful no matter.

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Richard, initially I am looking for a suitable dome mid and tweeter replacement. Some users have also commented that it would be nice to replace the Phillips AD5060 cone mid. Since mine is working great that is lower down on the list.

Just a quick update, while I have made some progress and evaluating options for DQ10 upgrade/ changes I am having issues finding driver candidates that are available. Many of the ones that look the best are on backorder, some of them for many months.
I am considering just using the drivers I can find (?These are inexpensive , available, and should be close to drop in replacements. Although they are likely not higher quality than what were in the speakers when they were new, they are modern maybe better designs, and they are not 45 years old!
Thoughts?

I decided to go with the 10" steel legs. The wooden ones seemed a bit too "furniture" looking and weren't as carefully manufactured in terms of positioning the angle with the mounting plate. Anyway, after finishing the job, my initial reaction was "looks a bit stark." 24 hours later and now I'm actually liking them...they seem a good compliment to the mid-century modern design like the DQ-10. Final step will be to find a dark walnut paint to get them to match the rails.

As for height, I think any taller would make them start to look "gangly and too tall" and add to instability.

If interested they are out on Amazon for $28/4 legs.

https://www.amazon.com/dp/B08S6Q3J8J?ref=ppx_yo2_dt_b_product_details&th=1

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Ideally speaker stands should put the tweeters at ear level. ?I made mine patterned after the early 3 post Dahlquist stands but made the taller putting the bottom of the speakers at 12 1/2” off the floor. ?I expanded the base dimension by 10% as well. ?That said, one should never look a gift horse in the mouth so I’d go with the higher WAF option.

Recently bought two sets of legs off Amazon for my DQ-10's. One set is 10" tall and the other is 8" tall. The 10" legs are a matte black finish and made of welded steel (see attached photo). I would want to paint them a dark walnut brown to match the rails. The wooden legs are 8" and a lighter brown than the walnut rails (could possibly stain them darker). The steel legs are? slimmer with a diameter of just over 1" at the widest part (at mounting plate); the wooden ones are closer to 2" in diameter where they attach to the metal mounting plate.

Is there a preferred height? I'm having trouble thinking such a small difference matters. It appears based on the files out here the stands raise the bottom surface 11.4 inches from the floor.

FWIW the wife likes the wood ones (they do seem to match the mid-century modern style of the 10's more than the plain steel) so I'd encounter a bit less resistance putting these in any room I choose.

Thanks for letting me know.

Sold.?