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Multi-Way Conventional loudspeakers with crossovers

OmniDirectional - work in progress
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Old 4th March 2017, 05:41 AM   #41
jameshillj is offline jameshillj  Australia
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If you put some sort of barrier so that up-firing tweeter doesn't radiate forward, what you then get is only the treble that's arriving at your listening position via the ceiling and maybe some walls - this gives the arriving wave energy a certain delay that should dramatically improve the 'spaciousness' of your sound - look up 'the Romeyn' sound that's based on the work of that speaker guru (plus other things audio) Floyd Toole.
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Old 4th March 2017, 08:13 AM   #42
calneva is offline calneva
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I have been interested in this type of omnidirectional waveguide for some time, but I doubt they work they way they look.

They're commonly used in in-ground outdoor "omnidirectional" speakers. But these speakers tend to have very low SPL and I doubt the waveguide does much more acoustically than a cap would, to keep rain out:

Click the image to open in full size.

I also see them on tsunami warning towers. Those towers consist of discs with four compression drivers each firing into the center where they wrap around 180 degrees out the pseudospherical waveguide. They usually stack several discs:

Click the image to open in full size.

Inside (click to undistort the image):
Click the image to open in full size.

It's not that much different than a folded horn, whether you fold it 180 or only 90 degrees. I'm doubtful it can be done with these shapes without significant distortion at any reasonably high SPL.

Last edited by calneva; 4th March 2017 at 08:22 AM.
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Old 4th March 2017, 03:04 PM   #43
DonVK is offline DonVK  Canada
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Thanks for the interesting purpose specific examples you provided, I haven't seen these applications before.

You can make an omni that sounds good and has good SPL levels for home hifi speakers. There are very few commercially available, hard to find for listening tests, and tend to be expensive, that's one reason I'm building a pair.

The garden speaker is probably a single full range weatherproof speaker pointing down from the "dustcap", the lower freq (<2Khz) are mostly omnidirectional without help if the driver is large enough and the lower reflector probably helps to maybe 5Khz. Thats enough for garden background music. It probably takes a garden hose and dogs better than most speakers.

The stacked horn array is very interesting. I went looking for how they use it. It's unusual because they seem to use it for voice as well as the usual siren tone modulation pattern. Distortions probably not important as you run for your life :-)
https://www.youtube.com/watch?v=T4fcg8E_BPM
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Old 4th March 2017, 03:14 PM   #44
DonVK is offline DonVK  Canada
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Quote:
Originally Posted by jameshillj View Post
If you put some sort of barrier so that up-firing tweeter doesn't radiate forward, what you then get is only the treble that's arriving at your listening position via the ceiling and maybe some walls - this gives the arriving wave energy a certain delay that should dramatically improve the 'spaciousness' of your sound - look up 'the Romeyn' sound that's based on the work of that speaker guru (plus other things audio) Floyd Toole.
Interesting suggestion. The domes are directional with frequency, having reasonable wide cone at low freq (120deg@2Khz) and narrow cone at high freq (30deg@15Khz).

A barrier would cause reflections or scattering near the dome. However the proper shape could focus the sound much like a parabolic sound dish for listening. Only it would be used in a reverse sense, trying to focus the energy at the reflection point. I need to think about this one
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Old 15th March 2017, 06:28 AM   #45
DonVK is offline DonVK  Canada
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Default Aperiodic Bi-chamber Bass improvement

After listening to them for awhile, I decided to improve the bass response. The current 16L BR response is weaker than I like and seems to start fading at 100Hz although its F3=60Hz.

I'm restricting the volume to 32L so the design choices were ApBc, BP4, or BP6, there's not enough room to fold a quarter wave horn. The Aperiodic was just easiest, as I already have split the volume and have 2 x 16L chambers. All I needed was to join the chambers with an internal port and then port out the second chamber. So total of 3 x tuning ports (2x external 5x17cm, internal 12x2cm).

The results match HornResp simulation and I get response to 40Hz with an 8" woofer. In fact its +10db higher than the BR at 40Hz. Its an audible improvement. This ApBc also has a dip at 175Hz in the near field measurement. The graphs below at @1m with room acoustics.
Attached Images
File Type: jpg DSCN1846 reduced.jpg (286.9 KB, 329 views)
File Type: jpg omni BR at 1m.jpg (124.5 KB, 325 views)
File Type: jpg omni ApBc @1m.jpg (130.0 KB, 67 views)

Last edited by DonVK; 15th March 2017 at 06:53 AM. Reason: corrected intra-port dimensions + room measurements
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Old 20th March 2017, 06:55 PM   #46
arcgotic is offline arcgotic  Romania
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Interesting speaker!
How does it sound? The stage is OK when you sit at best LP?

I have an idea for the tweeter horn, I will draw something to explain soon.
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Old 20th March 2017, 07:21 PM   #47
DonVK is offline DonVK  Canada
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It sounds good and it surprises people when they see the shape and listen to them. You can walk around the room and get good spacial sound from both speakers nearly everywhere. There's even a few special alcove spots where the reflections can mislead you (like acoustic fun house mirrors). The better position for stereo phantom image (using L+R ) is anywhere in the "sweet line" (not a spot) between the speakers about 2m back and at least 1m from the back wall.
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Old 21st March 2017, 01:33 PM   #48
fluid is offline fluid  Australia
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Quote:
Originally Posted by DonVK View Post
After listening to them for awhile, I decided to improve the bass response. The current 16L BR response is weaker than I like and seems to start fading at 100Hz although its F3=60Hz.

I'm restricting the volume to 32L so the design choices were ApBc, BP4, or BP6, there's not enough room to fold a quarter wave horn. The Aperiodic was just easiest, as I already have split the volume and have 2 x 16L chambers. All I needed was to join the chambers with an internal port and then port out the second chamber. So total of 3 x tuning ports (2x external 5x17cm, internal 12x2cm).

The results match HornResp simulation and I get response to 40Hz with an 8" woofer. In fact its +10db higher than the BR at 40Hz. Its an audible improvement. This ApBc also has a dip at 175Hz in the near field measurement. The graphs below at @1m with room acoustics.
Don if you also wanted the top end a bit flatter you can use a fairly simple filter to equalize the mass rolloff of the compression driver on the horn. It is usually a 6dB filter at around 20kHz which takes out some of the gain from the horn. Often called HF compensation.

I would think that it would help to reduce that 2Khz peak with your current crossover.

This thread has a circuit diagram for a different CD but it might give you an idea and you seem pretty handy with spice.

Impressive new compression driver from Peerless - Techtalk Speaker Building, Audio, Video Discussion Forum
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Old 21st March 2017, 03:03 PM   #49
DonVK is offline DonVK  Canada
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Thanks, and I agree they still need more EQ to flatten the FR. The electronics are not a problem for me, and I will get to that eventually when things settle. I measure and graph raw for the basic cabinet improvements, but I listen with S/w EQ to flatten things. I'm still evaluating how it radiates and works in the room.

I reduce the 2Khz bump (in S/W) as it makes the speaker sound way too bright. I'm also still not happy (but happier than before) with the bass performance. I think I need a 10inch woofer or maybe 2x8inch to give me better room projection and another 3db down to 40Hz.

Thanks for Peerless link. I think the HF peak/dip may be a function of the waveguide load. I've seen another post with the same waveguide, different CD, and same FR shape.
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Old 21st March 2017, 03:17 PM   #50
fluid is offline fluid  Australia
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I would be tempted to seal the cabinet you have and use some other drivers in separate smaller cabinets that you can place near your existing ones. Linkwitz has used some fairly cheap Peerless woofers for this and they seem to work quite well, Dayton has similar ones.

It is very hard to get a driver to go above 1 to 2 Khz properly but also have significant output below 100Hz.

If you were willing to go active I think you could get a much better response overall and is easier than changing passive components when tweaking. Downside is the need for more amps.
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