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Multi-Way Conventional loudspeakers with crossovers

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Old 23rd January 2021, 11:49 PM   #131
iamvalheru is offline iamvalheru  Canada
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Agreed, there is a difference between being technically accurate and commercially viable.
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Old 23rd January 2021, 11:58 PM   #132
diypole is offline diypole  United States
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Yes, you always want to give people the things you think are most important to the sound in something they can afford.

Many, many, many designs ignore the laws of driver beaming and use drivers far higher than they should be.
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Old 24th January 2021, 01:07 AM   #133
diypole is offline diypole  United States
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Quote:
Originally Posted by scottjoplin View Post
Yes probably, I'm referring to edge diffraction having the same effect as a very early reflection and blurring the image.
I agree with Charlie on minimum baffle diffraction, and would only add that there's a transition point at a frequency relative to the size of the driver/baffle.

The frequency that a driver begins to become directional and start beaming, which is when it equals a third of the wavelength it is producing.

Take a 4" driver that begins to become directional at 1127hz or so, crossed to an 8" mid at 1000hz.

Dipole diffraction/cancellation effects are actually much worse than a baffle of the same width in a closed box. With the 4" we expect a null and then a hump below it when the front and back come back into phase with each other before entering pure dipole cancellation.

But because the driver is becoming directional we do not see as deep a null as we expect, because not enough energy is reach the edge.

But we do see the half wavelength hump where they add, right about when the driver is becoming omnidirectional and radiating into full space at 1127, or thereabouts. Personally I deal with this in the crossover, as it is close to the crossover frequency.

I like to say the 8inch is running off the baffle, because nude or with minimal baffle it is operating entirely below the point where it is omnidirectional, and the compression wave in the front is completely cancelled when it meets the rarefaction from the rear. There are no diffractive effects.

Even though dipole effects are magnified diffractive effects, they are minimalized strategically with driver/baffle sizes and crossover points. Only the lower registers of the 4 inch will experience regular diffractive effects before it becomes too directional and does not illuminate the edge at all, and as Charlie points out, these effects have been driven as high in frequency as possible...pretty much completely eliminated with careful design.
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Old 24th January 2021, 07:25 AM   #134
Juhazi is offline Juhazi  Finland
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Gradient Helsinki 1.5 is controversial with the sideways bass dipole. The cookie cardioid midrange in itself works quite well I understand, and matches the waveguide tweeter's dispersion. I have never heard it playing.

There are some articles about 1.5 and making it sound good in a room is not easy. I don't like the idea at all. Dpiole front and backwave are supposed to hit the nearby walls and fill the room with bass without localization (below Schröder). Crossover to mid is around 250Hz.

Gradient Helsinki 1.5 loudspeaker | Stereophile.com
"When I first set up the Gradient Helsinkis, with only a small amount of toe-in, the low frequencies sounded rather phasey. This was minimized by increasing the toe-in angle to 45°. Once the speakers had been moved next to the sidewalls, I was reminded that there is something very attractive about the sound of low frequencies produced by an aperiodic design—as I had found with the Gradient Revolution, which also has a dipole-mounted 12" woofer. "

With Gradient Revolution, the user can rotate the bass module in relation to mid-tweeter top. And yes, Atkinson got better room response with Revolution than with Helsinki!
Gradient Revolution loudspeaker | Stereophile.com
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Old 24th January 2021, 07:37 AM   #135
Juhazi is offline Juhazi  Finland
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About timing and aligning acoustic centers - with multiway dipoles it is almost impossible to get perfect match at 0 and 180deg. It can be done with planars, but harly with cones or mixing cones and planars.

I searched my measurements of AINOgradient and studied them with different time windows, but various reflections and differences in dsp settings make analysis tricky. Anyway, I decided to optimize frontal response in matching 12" low mid cone and planar upper mid around 600-800Hz. LR4 slopes give prettier measurements but still I prefer the sound of LR2. Perhas because of less group delay ove xo and smoother vertical response...

Here some in- and outdoor measurements - more in the thread found in my signature.
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Old 24th January 2021, 12:27 PM   #136
Juhazi is offline Juhazi  Finland
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And step responses 0 and 180 for LR2 and LR4 crossovers. Notice the 180deg irregularities and bend in step at cardioid response. Backside responses green. Same measurement series as in previous post.
Attached Images
File Type: jpg step 0 180deg lr2.jpg (165.4 KB, 79 views)
File Type: jpg ainogneo83 out 0 180 step LR4.jpg (185.3 KB, 12 views)
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Old 24th January 2021, 01:07 PM   #137
iamvalheru is offline iamvalheru  Canada
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So, for a 4-way dipole, LR2 is preferable for all drivers, but what about BW3?

Also, if typical listening off axis angle in 15-30 degrees, try to optimize in that region?
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Old 24th January 2021, 03:14 PM   #138
iamvalheru is offline iamvalheru  Canada
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Would curving the top half of the H-frame negate the issues of the incomplete dipole radiation of the low midrange (the 15" woofer)?

Not perfect, but I assume way better than a flat surface perpendicular to the driver.


D
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File Type: png Round H-frame.PNG (23.9 KB, 20 views)
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Old 24th January 2021, 04:32 PM   #139
Juhazi is offline Juhazi  Finland
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Quote:
Originally Posted by iamvalheru View Post
So, for a 4-way dipole, LR2 is preferable for all drivers, but what about BW3?

Also, if typical listening off axis angle in 15-30 degrees, try to optimize in that region?
No rules! With DIY you are free to try everything, just try to understand what and why you do, and learn more from experiments. I think measurements are most important, but when all basics are in good form, final touches in sound are subjective. And there is always something left to make better...
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Old 25th January 2021, 09:26 AM   #140
ErikdeBest is offline ErikdeBest  Switzerland
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Quote:
Originally Posted by Juhazi View Post
Gradient Helsinki 1.5 is controversial with the sideways bass dipole. The cookie cardioid midrange in itself works quite well I understand, and matches the waveguide tweeter's dispersion. I have never heard it playing.

There are some articles about 1.5 and making it sound good in a room is not easy. I don't like the idea at all. Dpiole front and backwave are supposed to hit the nearby walls and fill the room with bass without localization (below Schröder). Crossover to mid is around 250Hz.

Gradient Helsinki 1.5 loudspeaker | Stereophile.com
"When I first set up the Gradient Helsinkis, with only a small amount of toe-in, the low frequencies sounded rather phasey. This was minimized by increasing the toe-in angle to 45°. Once the speakers had been moved next to the sidewalls, I was reminded that there is something very attractive about the sound of low frequencies produced by an aperiodic design—as I had found with the Gradient Revolution, which also has a dipole-mounted 12" woofer. "

With Gradient Revolution, the user can rotate the bass module in relation to mid-tweeter top. And yes, Atkinson got better room response with Revolution than with Helsinki!
Gradient Revolution loudspeaker | Stereophile.com
I was about to post about the Gradient Revolution I am still going to post a link to the user manual, where the concept is explained Golden Ear winner Gradient Revolution

I like the Gradient Revolution because one can indeed test different configuration without needing to rebuild the speaker. In a Dutch forum there was a similar question regarding the 90deg turned woofer. The developer of the daudio.nl dipole speakers commented that the 90 degrees turned woofers could indeed work well, but very room and position dependent - what is indeed the lesson from the Gradient Revolution. So, maybe one can indeed have a dipole speaker closer to the backwall by playing with the bass, but I think there is a consensus that the midhighs need to be pointed to the listener (or couple degrees tilt in). For best results the mid highs must be far from the backwall.

Some people did a "drastic" separation of the wide and volumous woofer, putting them in a corner (still dipole) or with a sealed subwoofer. So they were able to have only a narrow and undeep speaker in the room.

Dipol Line Array und Dipol Corner Woofer, Projekte der Nutzer / Eigenentwicklungen - HIFI-FORUM
products | Daudio - dipole – design – audio

(at Daudio look at the Daudio M2, I know they use a SB with a SD of 118cm2 , so must be a 6" unit).
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