Dahlquist DQ-10 flashback

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#103
planet10 said:
We got out first DQ-10 in 1978, they had the Advent woofer as did all the other pairs we sold.

dave
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Actually this jogged my memory: serial number 01-400 used the 12" CTS woofer. Mine were # 343-344. Which were probably all made before 1975. I changed them to a better faster woofer - not an Advent. I did help a guy tear down his set of DQ-10s and the woofer sure did not look like Advents, but he didn't get them new, so they may have been changed.
 
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#105
rayma said:
Magnepan uses series crossovers, for good reasons.
https://www.tubecad.com/2017/11/blog0402.htm
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Hi thank you very much indeed I will try to study this article
My thinking is that the DQ10 drivers are nice but nothing out of this world So the exceptionality must come from something else
And the xover is the first suspect
I will study this for a possible 2 way Thank you so much again
 
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#106
I think that dome mid was unusually good for its time, the woof also very nice, I think only the piezo was not that great. The xover, but also the research into the baffle size, location, and spacing of the drivers was well ahead of the stuff the drivers in a box used by most manufacturers at the time.

You can see that sort of spacing of drivers, and attention to baffles, and xover in the ProAc, Dynaudio speaker lines (and many more), and many diy projects at this site.
 
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#107
from here
https://www.stereophile.com/content/dahlquist-dq-12-loudspeaker

"The Phased Array technique, first used in the DQ-10, mounts the drivers in an arc with the tweeter farthest from the listener. The radiating plane of each driver will thus be at an equal distance from the listener's ears, resulting—all things being equal—in a time-coherent signal. Although this concept seems rather commonplace today, it was innovative in 1973. The new line of Phased Array loudspeakers shares another common heritage with the venerable DQ-10: minimization of cabinet diffraction. In both the DQ-10 and the new models, great care has been given to the shape and structure of driver baffles and enclosure. "
 
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#108
rayma said:
Magnepan uses series crossovers, for good reasons.
https://www.tubecad.com/2017/11/blog0402.htm
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Hi i am really sorry but i have had family issues .... i am reading now this and i have the feeling that the text of the paper contains some bombs just at the beginning Imho worth of some discussion
In SPICE simulations, no distinctions between the two crossover types can be discerned.
But then, SPICE simulations of crossover usually use resistors, not actual loudspeaker drivers. Real speaker drivers, in sharp contrast, are nothing like a SPICE resistor model. Does this make a difference? I believe it does, possibly a big difference.
About 30 years ago, I knew an electrical engineer with a PHD from Stanford, whose doctoral dissertation was on electronic filters; he had retired from Hewlett Packard and was devoting his efforts to loudspeaker crossovers. He told me that after years of analysis and experiment no crossover—no matter how elaborate and complex—could beat the simple, first-order series crossover.
His theory was two-part: first, any crossover order higher than the first must give rise to phase aberrations; and, second, by shunting the loudspeaker drivers with capacitors and inductors in the series crossover the drivers see needed dampening where they needed it most, i.e. outside their bandwidth limits.
In other words, the woofer gets shunted by the capacitor's falling impedance as the frequency extends beyond its high-frequency range, just as the tweeter gets shunted by the inductor's falling impedance at the tweeter's resonant frequency.
In contrast, he argued, in the parallel crossover, the woofer becomes unloaded at high-frequencies, as the inductor's increasing impedance decouples the woofer from the amplifier's low output impedance. (Goodbye damping factor of 2,000.) And the tweeter finds no useful damping resistance at its resonant frequency, as the crossover capacitor's impedance has climbed to too high a value to prove useful.
Was he right ?
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Good question.
 
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#110
rayma said:
Yes, the first order series crossover is Magnepan's "secret sauce", but it can work for other 2-ways also.
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Hi thank you so much again and a secret maybe for an ignorant like me not for you clearly 🙂👍👍👍
Then the question ... if this design provides some advantages why is not more popular ? from what i see its a matter to change only connections between same parts ... it could be done quite easily for a speedy check Very strange
I think you said this and i am quoting again
In SPICE simulations, no distinctions between the two crossover types can be discerned.
But then, SPICE simulations of crossover usually use resistors, not actual loudspeaker drivers. Real speaker drivers, in sharp contrast, are nothing like a SPICE resistor model. Does this make a difference? I believe it does, possibly a big difference.
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if accurate models of actual drivers are not available i cannot understand the reason for simulation
Simulation results are reliable as long as accurate models for all parts are available Am i missing something ?
Then saying that no difference are evident from simulation is almost misleading (Like the like the joke of the man who sees poorly and says there is no puddle and then falls up to his knees in it Actually the original version is much more rude ... it is not a puddle)

Anyway the more important conclusion is that series crossovers can indeed provide some benefits
Am i wrong when i say that a parallel xover can be transformed in a series one only changing connections between same parts ?
I am leaning towards a 2 way because they are already quite complex for me I guess i will have to do without the very low bass
Life is often a compromise
Thank you very much again
 
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#112
ginetto61 said:
Hi thank you so much again and a secret maybe for an ignorant like me not for you clearly 🙂👍👍👍
Then the question ... if this design provides some advantages why is not more popular ? from what i see its a matter to change only connections between same parts ... it could be done quite easily for a speedy check Very strange
I think you said this and i am quoting again
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Only if you had a "textbook" electrical parallel crossover would that work. The vast majority of parallel crossovers reconfigured to series would yield quite different transfer functions. There is no speedy check A/B comparison here. 🙂

Dave.
 
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#113
Davey said:
Only if you had a "textbook" electrical parallel crossover would that work. The vast majority of parallel crossovers reconfigured to series would yield quite different transfer functions. There is no speedy check A/B comparison here. 🙂
Dave.
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Hi thanks a lot for the very valuable advice Always looking for an easier way to get things done 😕
Still i wonder why very very few designers choose the series type if some benefits can be gained. I am confused.
If i understand well SPICE can be used to sim some xover circuits as well ? i also understand that no models are available for drivers and i have to treat them as resistors But it will be a start I have to get back to SPICE then
 
#114
rayma said:
The 6dB crossovers are not too popular in general, since they require very good, wide band drivers,
and volume levels can be restricted.
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Thank you very much indeed A weak brain like mine gets confused when i think that a 1st order xover was a selling point of high end speakers
What were they doing ? maybe there is a trade of ? give up with something to get something else ?
 
#118
hi thank you for the very helpful advice
to sum up using 6dB xovers can put more stress on dome drivers that Could be used outside their optimum range
So even just a 2kHz cut at 6dB at higher SPLs could put a lot of stress on a 1" tweeter
I have to try to sim something with Spice as a start
 
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#119
No, that really doesn't sum it up at all. Possible increased tweeter stress is but one of many aspects of first-order crossover design.
There are numerous references (through many many years) outlining the advantages and disadvantages of first-order crossovers. (Quite a few on this very forum.)
To designate these as a "naive design choice" is quite.....naive.

Dave.
 
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#120
Hi i see But why in life we end always with ... it depends ? there must be a better approach in everything and also in crossover design
The approach that provides the most important pros and the less important cons
I have to say that when i see a 2 way xover with almost 40 parts (just to say) i am sincerely disturbed Really
Are all these parts really needed Or maybe it's a problem of drivers not fit for the task ?
I listened to a pair of Epos ES11 speakers I loved their sound And this is their xover
https://funem.files.wordpress.com/2012/04/dsc_8881.jpg
you may say ... so go and clone them Problem is that the woofer is proprietary and not availbale on the market If not i would do immediately
What i really did not like is the plastic baffle ... ridiculous Better a 2" MDF one By far With bracing
 
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