Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Multi-Way Conventional loudspeakers with crossovers

Nexus - World's Easiest Controlled Directivity Loudspeaker
Nexus - World's Easiest Controlled Directivity Loudspeaker
Nexus - World's Easiest Controlled Directivity Loudspeaker Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 25th December 2019, 09:35 AM   #21
Patrick Bateman is offline Patrick Bateman  United States
diyAudio Member
 
Patrick Bateman's Avatar
 
Join Date: Oct 2006
Location: San Diego
Quote:
Originally Posted by zmyrna View Post
What would it be like if 8 mid drivers were used in a circular arrangement? Round horn tweeter in the middle of course.
The whole thing seems very 'fractal', similar to these three speakers:

Click the image to open in full size.

Snell eXpanding Array, courtesy of forum member Speakerdave

Click the image to open in full size.

Horbach Keele Array

Click the image to open in full size.

Follgott's pseudo coaxial

Click the image to open in full size.

Beolab 90


Click the image to open in full size.

Here's a sim where I've gone from four drivers to six. Basically the more drivers you add, in a larger and larger array, you can control directivity to a lower and lower frequency. Please note that the response above 1khz is a mess, but all of that would be low-passed. The whole idea here, is that the midbass array extends the response of the waveguide down to 500Hz or even 200Hz. It's basically a combination of the epic polars you get with a waveguide, along with an array that's 'nested' around it. The idea is that most of us can't tolerate a 40" x 40" x 40" waveguide in our living rooms, so we can put a bunch of midbasses around the array to extend directivity control down to 350Hz or so. Similar to what a Unity horn does, but without being two feet deep. I think you might be able to make one of these speakers as shallow as 8-12" or so.

Nothing earth shattering here; Snell, Lexicon and B&O got here before I did. I guess the interesting part is how easy it is to combine it with a waveguide in the center, and how ridiculous the efficiency gets. I heard the Beolab 90 at CES and that speaker could melt your face off, it's LOUD. For my money, it's the best speaker I've ever heard.

If you're willing to discard the variable directivity that Beolab and Lexicon offers, it seems fairly straightforward to make something similar on a flat baffle, by adjusting the crossover points and the spacing to yield a specific beamwidth.

Last edited by Patrick Bateman; 25th December 2019 at 09:40 AM.
  Reply With Quote
Old 25th December 2019, 03:58 PM   #22
BradH is offline BradH
diyAudio Member
 
Join Date: Jul 2019
I hope those sims are encouraging enough for you to run with this concept. Back when you made your UICW I modeled a cabinet for it that had a nice panel look to it. If one was willing to stack CNC'd elliptical cuts then you could have a very nice roundover with high WAF.

This one is easy to assemble and only uses a couple sheets of ply (I don't remember if I was able to get both speakers to fit on one sheet...) It's designed for a sealed cab that used four 6.5" woofers down to 40hz. Sealed down to 40hz is the sweet spot for me. With the 5.25" MCMs you use it could be even smaller.
Attached Images
File Type: png UICW Cabinet.png (15.6 KB, 61 views)
  Reply With Quote
Old 25th December 2019, 08:01 PM   #23
Patrick Bateman is offline Patrick Bateman  United States
diyAudio Member
 
Patrick Bateman's Avatar
 
Join Date: Oct 2006
Location: San Diego
Quote:
Originally Posted by zmyrna View Post
What would it be like if 8 mid drivers were used in a circular arrangement? Round horn tweeter in the middle of course.
Click the image to open in full size.

Here's a sim with eight drivers.

It looks pretty cool, but this thing was a *nightmare* to get working. I can see why Horbach and Keele used an optimizer to figure out the shape and phase of their filters.

I don't think I could have achieved this response if I didn't know a thing or two about xovers. (In the polar response, note that these go all the way out to 90 degrees; the response that's 90 degrees off axis isn't great, but I am not concerned about that, I really only care about 0-45 degrees. I don't listen to speakers 90 degrees off axis.)

I have a feeling that the original design, a plain ol' dipole, is probably a heck of a lot less work and easier to get right.

BUT...

This design could be crammed right up against a wall, which the dipole can't do.

To get this response, here's what I had to do:

1) I went from four to eight drivers

2) I used the same spacing as Horbach and Keele did

3) I tried a bunch of different filters. Linkwitz Riley 6th order worked the best, but I wouldn't use it because it rings too much.

4) 3rd order filters worked, but there was a big dip at the xover. That told me that things could be improved by moving the outer woofers BACK by 20cm, and then flip the polarity

5) And then I underlapped the crossover points

By going from four to eight drivers, directivity control is maintained all the way down to 250Hz. But to me, that's overkill. I think 500Hz is probably enough. Then again, maybe the additional directivity control would work well. Dunno.

Click the image to open in full size.

Click the image to open in full size.

I used the same spacing that's in the Horbach Keele paper

Last edited by Patrick Bateman; 25th December 2019 at 08:06 PM.
  Reply With Quote
Old 25th December 2019, 09:08 PM   #24
Patrick Bateman is offline Patrick Bateman  United States
diyAudio Member
 
Patrick Bateman's Avatar
 
Join Date: Oct 2006
Location: San Diego
Quote:
Originally Posted by BradH View Post
I hope those sims are encouraging enough for you to run with this concept. Back when you made your UICW I modeled a cabinet for it that had a nice panel look to it. If one was willing to stack CNC'd elliptical cuts then you could have a very nice roundover with high WAF.

This one is easy to assemble and only uses a couple sheets of ply (I don't remember if I was able to get both speakers to fit on one sheet...) It's designed for a sealed cab that used four 6.5" woofers down to 40hz. Sealed down to 40hz is the sweet spot for me. With the 5.25" MCMs you use it could be even smaller.
I think this is the most promising solution.

Click the image to open in full size.

For instance, here's Vituixcad's predicted response for a two way. There are four mids ringing a driver in the center. This is basically the same thing from post #1, but I've pushed the mids further out. The geometry, including the spacing, is virtually identical to the DNA Sequence speaker. Basically it looks like I packed my drivers really close together, but I didn't need to.

In the sim, you see the directivity broadening above 1khz. Of course, this is because Vituixcad treats the drivers as if they're omnipolar, and we'll fix that by putting a waveguide in the center, just as North, Follgott, Horbach and Keele did.

The sim predicts that the design will hold 90 degrees of directivity down to 650Hz. But I think that could be pushed down to 500Hz by curving the baffle, or adding a roundover.

Click the image to open in full size.

Picture the DNA sequence, but with a roundover, and that's the general idea. (Similar to what you described.)

The roundover generally seems to extend the directivity cutoff. It might even push it down to 400Hz.

Note that this speaker is a tweaker's dream, there's a million variables to tweak:

1) the setback of the waveguide changes the response and directivity
2) the crossover slopes have a *huge* difference, and this speaker is a prime candidate for biquad filters
3) all pass filters or FIR filters would be worth a look
4) delay changes things

Last edited by Patrick Bateman; 25th December 2019 at 09:12 PM.
  Reply With Quote
Old 25th December 2019, 09:46 PM   #25
bwaslo is offline bwaslo  United States
Old guy with soldering iron
diyAudio Member
 
bwaslo's Avatar
 
Join Date: May 2006
Location: Portland, Oregon!
Nexus - World's Easiest Controlled Directivity Loudspeaker
That's really cool. I like the directivity blend from waveguide to array to dipoile. So how do they sound? Can't see any mention of that in the posts! If I were you I'd make a second one and see how it sounds in stereo.

Sadly, for my little Portland house there's no way I can get dipoles far enough away from the wall behind (at least no where my wife would let me leave them sitting).
__________________
[W9MJE] Horn spreadsheet SynergyCalc/; SmallSyns SmallSyns;
Crossover design Xsim; Depot diffusor super-easy diffusors
  Reply With Quote
Old 26th December 2019, 09:13 PM   #26
Patrick Bateman is offline Patrick Bateman  United States
diyAudio Member
 
Patrick Bateman's Avatar
 
Join Date: Oct 2006
Location: San Diego
Quote:
Originally Posted by bwaslo View Post
That's really cool. I like the directivity blend from waveguide to array to dipoile. So how do they sound? Can't see any mention of that in the posts! If I were you I'd make a second one and see how it sounds in stereo.

Sadly, for my little Portland house there's no way I can get dipoles far enough away from the wall behind (at least no where my wife would let me leave them sitting).
Of the speakers I've made in the past year, I think Nexus One (this speaker) and the first two Metlako speakers sounded the best. There's something about using four (fairly) big midranges that really makes the speaker sound dynamic.

Generally, I prefer the sound of wide directivity to the sound of narrow, and both those speakers have that in common.

I'd like to keep this speaker close to the wall, so I intend to rebuild it as a ported box.
  Reply With Quote
Old 26th December 2019, 09:37 PM   #27
Patrick Bateman is offline Patrick Bateman  United States
diyAudio Member
 
Patrick Bateman's Avatar
 
Join Date: Oct 2006
Location: San Diego
Click the image to open in full size.

The DNA speaker is tilted backwards by 26.57 degrees, just as the midranges are tilted by 26.57 degrees.

Click the image to open in full size.

Nexus One was measured with the speaker baffle 100% vertical, no tilt.

I ran some sims in VituixCad, using a 26.57 degree tilt, and it didn't make a whole lotta difference that I could see. It's possible that I missed some aspect, but to me the graphs were nearly identical.

There ARE a few improvements from tilting it back:

1) By tilting the baffle backwards by 26.57 degrees, the midranges are now 10% closer together.

Click the image to open in full size.
Gradient uses this same trick in their "Helsinki" speaker. Basically tilting the drivers backwards allows you to pack them tighter together, vertically.

2) Conversely, one could take advantage of that 10% to space the midranges out further on the vertical axis

3) Gradient has a paper explaining why they use that tilt. IIRC, it puts one of the major reflections on the ceiling *behind* the listener instead of the wall.

4) Dipole woofers need some room to "breathe." Tilting the baffle backwards puts the woofer in the DNA sequence over a foot further from the wall than the midranges and tweeters are.

On the downside, tilting the baffle puts the top woofers nearly half a wavelength out of phase with the bottom woofers at the xover point. I'm kinda surprised that the sims don't show any downsides to this.
  Reply With Quote
Old 26th December 2019, 10:18 PM   #28
Nissep is offline Nissep  Sweden
diyAudio Member
 
Join Date: Aug 2011
Why not add even more but smaller drivers in a full ring around the center waveguide? we know how well the midrange taps on a synergy horn filters out distortion.
So cheap 40mm speakers from China would probably work. I have tried some “no name” 40mm inverted done speakers with small band pass port in front of it, and the acoustic filter gave me a nice ~300-1000hz response.

Danley have a illustration of this kind of arrangement on a flat baffle where each ring of drivers becomes larger in size.

And to extend the directivity lower in frequency than driver distance in a array can provide. Look at what Dutch & Dutch does with the 8c.
  Reply With Quote
Old 27th December 2019, 08:22 AM   #29
zmyrna is offline zmyrna  United Kingdom
diyAudio Member
 
Join Date: Nov 2009
Location: London
Thanks very much PB. As usual though, can't open your photos and files ☹️
  Reply With Quote
Old 27th December 2019, 04:51 PM   #30
Patrick Bateman is offline Patrick Bateman  United States
diyAudio Member
 
Patrick Bateman's Avatar
 
Join Date: Oct 2006
Location: San Diego
Quote:
Originally Posted by zmyrna View Post
Thanks very much PB. As usual though, can't open your photos and files ☹️
I've seen a few people say this, and they're all in foreign countries. I'm not 100% certain, but I think my image provider may be blocked in certain countries. For instance, the UK has a law where you have to 'opt in' for p o r n.

And since I'm using one of the world's biggest image hosting companies (imgur) I believe it may be blocked on that grounds, in certain countries.

I'll do some research and see if there are some who escape this. I used to use Google Picasa, but Google made it unusable, just like they broke gmail, maps and RSS. Google has a habit of taking good software and breaking it.

And of course, Yahoo's flickr is terrible these days too, and photobucket has been worthless for ages.
  Reply With Quote

Reply


Nexus - World's Easiest Controlled Directivity LoudspeakerHide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Depth of soundstage - controlled directivity or in-wall? stretchneck Multi-Way 166 15th July 2018 02:25 PM
Any controlled directivity DIYs? mirekti Multi-Way 63 7th October 2015 02:22 PM
Klang + Ton 2/2007 Nexus loudspeaker article needed supernet Multi-Way 4 31st March 2008 12:31 AM
Blending controlled directivity treble with dipole midrange? 454Casull Multi-Way 21 17th September 2005 01:28 AM


New To Site? Need Help?

All times are GMT. The time now is 03:16 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2020 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2020 DragonByte Technologies Ltd.
Copyright ©1999-2020 diyAudio
Wiki