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
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 22nd December 2019, 08:39 PM   #1
Patrick Bateman is offline Patrick Bateman  United States
diyAudio Member
 
Patrick Bateman's Avatar
 
Join Date: Oct 2006
Location: San Diego
Default Nexus - World's Easiest Controlled Directivity Loudspeaker

I've spent the better part of the last year trying to make a speaker that could replace my Waslo Cosynes. I like the Cosynes a lot, but they're too big for my living room and my wife will certainly banish them soon.

I've made something like NINE attempts to replace it(1), and I keep failing. In particular, in my latest project, the waveguide was insufficiently small. Basically the speaker lost directivity control at 2khz.(2)

Frustrated by a pile of unfinished horns, I decided to do something different, and it worked out quite well.

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

It's the exact same drivers I used for Metlako and Celilo, but I'm uses a much smaller waveguide on the tweeter, and I've arrayed the midbasses.

Click the image to open in full size.

Click the image to open in full size.

The arrangement is largely inspired by DNA Sequence speaker. [url=https://patents.google.com/patent/US6801631B1]From the patent:/url]

"Few conventional speaker systems approach an ideal of a high efficiency point source directional loudspeaker system. In fact, most conventional speaker systems are low in efficiency, lack phase coherency, and do not act as an apparent point source system. A speaker system in accordance with the present invention closely emulates a single point source. Embodiments of the present invention achieve this result by an advantageous arrangement of transducers. The arrangement of transducers minimizes the amplitude of the sound waves that can cause room reflections and the resultant distortion therein."

(1) Metlako: A Small, Affordable Two-Way Unity Waveguide

(2)Celilo : A Small, Affordable Two-Way Unity Horn
  Reply With Quote
Old 22nd December 2019, 08:44 PM   #2
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 waveguide geometry is largely copied off of the JBL M2. I describe how to model that here:

JBL M2 for The Poors


I had a 'hunch' that you might be able to rotate the waveguide 26.57 degrees without screwing up the polars too bad, because the waveguide is already asymmetrical.
  Reply With Quote
Old 22nd December 2019, 09:14 PM   #3
Patrick Bateman is offline Patrick Bateman  United States
diyAudio Member
 
Patrick Bateman's Avatar
 
Join Date: Oct 2006
Location: San Diego
Before I post the polars of Nexus One, I wanted to post it's competition.

Click the image to open in full size.

Click the image to open in full size.

This is the polar response of my Waslo Cosynes. It has a waveguide that's about 24" across, and the measured response shows a beamwidth that's approximately 90 degrees, from about 500Hz to 10khz. There's some narrowing of the beamwidth in the midrange, likely an interaction between the midranges and the tweeter at the xover point.

Click the image to open in full size.

Click the image to open in full size.

Here's the polar response of Celilo II. I had high hopes for the speaker, it's nice and smooth, but the waveguide is too small. It's lost pattern control at 2khz.

Click the image to open in full size.

Click the image to open in full size.

Here's the polar response of my Kali LP6 with a roundover. For $149, you're going to have a hard time doing better than this. But I wish the Kali LP6 had the pinpoint imaging of the Cosyne. I believe that the Cosyne's holographic imaging may be due to the narrower beamwidth and directivity control.

Click the image to open in full size.

Click the image to open in full size.

Here's the polar response of Nexus One. It's a nice combination of the narrower beamwidth of the Cosynes, with treble smoothness that approaches the Kali LP6.

To me, it's a bit of a mystery why the directivity control goes all the way down to 50Hz. I'm not an expert on dipoles, but I thought dipoles only worked over a limited bandwidth.

I'm not sure if I just got lucky with the baffle diameter, or if there's some synergistic thing going on with the array spacing. Either way, this EXTREMELY simple speaker is quite close to a full range constant directivity, in a two-way, using less than $75 in drivers.

Go figure.

I'd love to say that this was the product of weeks of research and computer sims, but that couldn't be further from the truth. After the frustrating results of Celilo, I was about to cry "uncle" and just go and build another Waslo speaker, since mine weren't working as planned.

But I decided to throw Nexus together, because I've been curious about using arrays to control directivity instead of waveguides.
  Reply With Quote
Old 22nd December 2019, 09:39 PM   #4
tmuikku is offline tmuikku  Finland
diyAudio Member
 
Join Date: Sep 2004
Location: Savo, Finland
Send a message via ICQ to tmuikku
Way cool! Are you planning to run it open baffle or was this just a test? Probably not going to work placed into a corner like your other speakers have been recently?
  Reply With Quote
Old 22nd December 2019, 09:48 PM   #5
John Sheerin is offline John Sheerin  United States
diyAudio Member
 
Join Date: Nov 2003
Location: California
>To me, it's a bit of a mystery why the directivity control goes all the way down to 50Hz. I'm not an expert on dipoles, but I thought dipoles only worked over a limited bandwidth.

It's because it's a dipole. They maintain the dipole pattern as frequency drops, but you lose sensitivity. You can EQ the system to get more output within the limits of the driver's linear operating range, but there's some limit to that. They start to have polar problems as you go up in frequency. So that is probably why you remember them as only working over a limited bandwidth.
  Reply With Quote
Old 22nd December 2019, 10:00 PM   #6
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 John Sheerin View Post
>To me, it's a bit of a mystery why the directivity control goes all the way down to 50Hz. I'm not an expert on dipoles, but I thought dipoles only worked over a limited bandwidth.

It's because it's a dipole. They maintain the dipole pattern as frequency drops, but you lose sensitivity. You can EQ the system to get more output within the limits of the driver's linear operating range, but there's some limit to that. They start to have polar problems as you go up in frequency. So that is probably why you remember them as only working over a limited bandwidth.
Hmmm. If that's the case, then this arrangement seems like it has merit. Basically there's three phases:

1) In phase one, the loudspeaker directivity is controlled by a waveguide. (About 1350Hz to 20khz)

2) In phase two, the loudspeaker directivity is controlled by the array (One octave, about 675Hz to 1350Hz)

3) As the wavelengths exceed 710hz, they wrap around the baffle, and there's dipole cancellation to the sides
  Reply With Quote
Old 22nd December 2019, 10:06 PM   #7
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 tmuikku View Post
Way cool! Are you planning to run it open baffle or was this just a test? Probably not going to work placed into a corner like your other speakers have been recently?
Check out these two videos, you can hear that the speaker is quite directional:

Nexus One

Here's a video of Nexus One

Metlako II

Here's a video of Metlako II (Metlako: A Small, Affordable Two-Way Unity Waveguide)

If you listen to them back-to-back, you hear that Nexus I is quite directional, even in the midrange and midbass.

Right now I'm reluctant to touch *anything*, since it seems to work nicely. But here's some ideas I have:

1) I'd like to make the waveguide deeper, so that the beamwidth is narrower in range from 4-8khz

2) I'd like to add a roundover

3) I'd like to try it as a vented box, a sealed box and a cardioid. Basically see which performs the best.

The box is ridiculously simple to build, so it shouldn't be too much trouble to try.
  Reply With Quote
Old 22nd December 2019, 10:18 PM   #8
TNT is offline TNT  Sweden
diyAudio Member
 
Join Date: Apr 2003
Location: Sweden
You are the *DIY* champion here I think!! Way to go!

//
__________________
More distortion to the people!
  Reply With Quote
Old 23rd December 2019, 12:52 PM   #9
TMM is offline TMM  Australia
diyAudio Member
 
Join Date: Sep 2007
Location: Australia
Send a message via AIM to TMM
I think the rotated arrangement of 4 drivers has a fundamental flaw that is seldom (if ever?) addressed - being that i've only ever seen people sim/measure this arrangement on axis horizontally and off axis vertically, or on axis vertically and off axis horizontally. If you measure at a compound angle (simultaneously off axis both horizontally and vertically) it is far less well behaved since it then effectively becomes a non-rotated cross arrangement with axially aligned 'top' 'bottom' 'left' and 'right' drivers.

I guess it still gives an advantage when placed in a rectangular prism shaped room and listened to on-axis, as the most significant reflections are only off-axis in either horizontal or vertical axes, not both at once. Doesn't work so well for non-rectangular rooms or if listened to off axis.

Last edited by TMM; 23rd December 2019 at 01:01 PM.
  Reply With Quote
Old 23rd December 2019, 08:56 PM   #10
BradH is offline BradH
diyAudio Member
 
Join Date: Jul 2019
Directivity is clear by the video. Fingers crossed that a sealed version turns out well. Curious about the compound angle eluded to by TMM
  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 09:08 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