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Multi-Way Conventional loudspeakers with crossovers

In Pursuit of a 20-20k Dipole Loudspeaker
In Pursuit of a 20-20k Dipole Loudspeaker
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Old 1st January 2019, 11:04 PM   #1
CharlieLaub is offline CharlieLaub  United States
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Default In Pursuit of a 20-20k Dipole Loudspeaker

I thought I would kick off 2019 with this thread about dipole loudspeaker design and construction. Specifically, how to create a loudspeaker having a dipole radiation pattern across as wide a frequency range as possible, when it might make sense to abandon this goal in favor of some other criteria, and the justification for employing the "full range dipole" concept.

One area that has been neglected (in my opinion) is what is happening to the rear of the loudspeaker. In an open baffle or dipole speaker, there is sound emanating from the rear that ultimately reaches the listener via the room and this is just as important as what is coming out of the front of the loudspeaker. So when I talk about a "full range dipole" loudspeaker I mean to emphasize that the front and rear radiation pattern should be as similar as possible over all frequencies.

I have been working towards these goals for a few years now and have built and dismantled a few test systems to try out some different approaches. I hope to share what I have learned, why I prefer this type of loudspeaker, and when it might work well or not work well for audio reproduction. I hope that others will chime in with their own experiences in this area so that we can all learn from each other.

I thought I could put down some thoughts into a few posts, but ended up creating a pdf file to kick off the topic (see attached). I would love to read about what systems you might be developing along these same lines and get your feedback about my approach to such a system.
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File Type: pdf In Pursuit of the 20-20k dipole.pdf (701.6 KB, 362 views)
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Last edited by CharlieLaub; 2nd January 2019 at 01:23 AM.
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Old 2nd January 2019, 01:38 AM   #2
bentoronto is offline bentoronto  Canada
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In Pursuit of a 20-20k Dipole Loudspeaker
You make it sound as if the old BR box is "correct" and the OB is the problem.*

It really depends on which aberrations you want to live with. Fans of OBs prefer their ambient natural sound any day, whatever the speculative textbook curves (based on speculative rooms with speculative drapery, etc) may say.

While textbook thinking may lead some folks to agonize over low freq cancellation, it is better to think about the reality of bouncing waves and incoherent phases and addressing the rear wave, not fretting over it.

Long pipe to sequester rear wave

Nobody more sophisticated than Linkwitz was (and music lover too) and he turned out
to truly endorse the sound of OBs.

B.
* OBs, like with electrostatics, ribbon tweeters, and motional feedback, don't "compute" for commercial manufacturing and that force twerks our perception (aka "availability heuristic")
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Last edited by bentoronto; 2nd January 2019 at 01:41 AM.
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Old 2nd January 2019, 03:02 AM   #3
anatech is offline anatech  Canada
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In Pursuit of a 20-20k Dipole Loudspeaker
Hi Ben,
AnOB speaker is much less expensive to ship than any other speaker design. That is a very strong pull in favour of commercial profits.

Personally, I haven't heard an OB I liked yet. I like variations on speaker boxes, like sealed, bass reflex, horn and transmission line.

-Chris
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Old 2nd January 2019, 08:48 AM   #4
Juhazi is online now Juhazi  Finland
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I love dipole sound for acoustic instruments and vocal - folk and classical recordings usually have nice sound with minimal studio trickery. Jazz and pop from 1950-60's sound good too!

I skipped the dipole radiation below 200Hz like my ideal origin Gradient 1.3. Planar drivers in narrow baffle help a lot above 2kHz! Check the link in my signature!

Front- and backside radiation (mirrored left-right), other normalized
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Old 2nd January 2019, 09:05 AM   #5
Steve Luck is offline Steve Luck  New Zealand
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I was looking at AER Pnoe horns on a youtube video of there stand:

YouTube

but check out the solid clear acrylic panels with the tiny drivers fixed in the middle. inducters for bass are nothing new but from a high end audio manufacturer for full range? They claim any surface can become a speaker!

AER | the goldy
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Old 2nd January 2019, 01:12 PM   #6
ErikdeBest is offline ErikdeBest  Switzerland
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thanks for posting your findings Charlie!

Reading from your and Juhazi's experience I think I will stick to the B&G NEO10s for the 2nd system as well, actually only exchanging the woofers. You measured several drivers and apparently none is really as good as a planar.

What I am curious about and willing to try is dividing the bass (below say 400Hz) over two channels: the 4x WS25E up to 200Hz and a single 8" or 10" from 200Hz up to 600 (or higher): this woud reduce lobing in the bass and relieve the B&G NEO10 from bass duties.

Best, Erik
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Old 2nd January 2019, 02:01 PM   #7
CharlieLaub is offline CharlieLaub  United States
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It's not a bad idea to add another driver between the woofer and the Neo10. I am facing this exact same dilemma in one of my own planned builds, which will use the Dayton AMTPRO-4. My measurements of that driver in free air (attached) show that it has a passband that starts just below 1kHz, but do to the distortion signature I will cross over to it above 1kHz, e.g. 1.2k-1.6kHz. A large dipole woofer will barely get there, so I will probably use a moving coil midwoofer between 500Hz and 1.5kHz, and then use some spare 18" pro drivers below 500Hz. Doing this will work, but it adds another band into the mix since I don't expect the 18's to go low enough, although I might try to use some baffle on them to help that out.

Your Neo10 is a little easier to work with. It has an advertised free-air frequency response that extends down to 200Hz or so IIRC. But the response is drooping below 1kHz. Since you should be able to use a nude 8" to 1kHz without any issues, you might consider bumping your crossover from the 8 to the Neo10 to 700-800Hz to use the planar driver where it has more sensitivity (output). For example of the response from an 8" nude in free air, see attached measurement of a Dayton RS225.
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Old 2nd January 2019, 03:00 PM   #8
scottjoplin is offline scottjoplin  Wales
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Hi Charlie, thanks for the file. If the priority is symmetry isn't there a way to use two monopoles, or is the lack of box also worth preserving as SL hints?
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Old 2nd January 2019, 04:22 PM   #9
John Busch is offline John Busch  United States
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Default I'll make it easy for you!

Happy New Year Charlie and fello DIY peeps!

Hey Charlie, Send me 10 grand and I will build something for ya! Back to reality, this will be an interesting thread to watch! Looking forward to see how things evolve! Best
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Old 2nd January 2019, 04:28 PM   #10
CharlieLaub is offline CharlieLaub  United States
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Would you settle for this?

Click the image to open in full size.
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