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

Mini-Synergy Horn Experiment
Mini-Synergy Horn Experiment
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 27th November 2015, 11:33 PM   #1
natehansen66 is offline natehansen66  United States
diyAudio Member
 
Join Date: Mar 2011
Location: Rochester, MN
Default Mini-Synergy Horn Experiment

I've been interested in building a Synergy horn for 3, maybe 4 years now. The SH is what got me interested in high eff speakers, horns/wgs, etc. The more that I build and learn about audio the less I think a Synergy is ideal for home use......the ports near the comp driver exit being my main beef. Thinking and knowing are two different things and so before I write it off completely I figured I might as well build the dang thing. It's not like I haven't had a case of Synergy mids (Celestion TF0410MR) laying around for 3 years or anything . I've seen some data comparison of ports/vs no mid ports but not quite at the level of detail I'd like to see to make any kind of determination. Some of the best data I've seen is of Paul Spencer's big elliptical job. Looks to be high q resonances in the normalized fr polar, so to my way of thinking what look like off axis resonances are actually mostly present in the 0 curve.

OK........on to the experiment. First I want to say that yes, I do understand that the Synergy horn "should" be a rectangular section and I understand why. My reasoning to go elliptical is 1) I don't see a square section horn as being the ideal shape for the wave, and 2) I have an eoswg just laying around, but no square horns. Elliptical it is. The wg is an EOS job that I built a little over a year ago. 18" wide with a roughly 90x60 pattern, and a 1.5" radius roundover: DIY 18" elliptical waveguide. The drivers are the aforementioned 4" Celestions and a BMS 4524. I dont have any pics of the mid chambers at the moment, but they consist of a 2 counterbore frustum thats .4 deep and a .5 port thats .35 long. I didnt intend to make the port that long but my wg was thicker than I remember.The port is offset to the edge of the frustum, and the driver is mounted such that the port is at the edge of the driver over part of the surround. The center of the port is 1.5 from the cd exit which is as close as it can get. My thinking was that 1.5 plus my estimated distance to the phase plug/back plate on the BMS would put the cancellation notch where it would be workable for the xo. Ive done enough Horn Resp models over the years to know that this would get me close. Im using 3 mids for this, with the ports spaced equally, wired in series.


Sorry for the lousy smartphone pics. Data is coming next.
Attached Images
File Type: jpg IMAG0505.jpg (72.9 KB, 1660 views)
File Type: jpg IMAG0507.jpg (41.0 KB, 1630 views)
File Type: jpg IMAG0506.jpg (101.9 KB, 1620 views)
  Reply With Quote
Old 27th November 2015, 11:39 PM   #2
natehansen66 is offline natehansen66  United States
diyAudio Member
 
Join Date: Mar 2011
Location: Rochester, MN
My measurement environment in the basement isnt ideal and a 2.5ms gate is the best I can do with a measurement distance of about 3. NO eq. First, I measured the wg/hf driver without the ports. Then I added the ports and mid drivers and remeasured with the horn in the same location. I need to do some more measurements and check the vertical and oblique, but this is much better than I expected. The worst of the fr anomalies is at 20 over 10khz, and at 30 and beyond the level seems to fall by 1-1.5dB over the full bandwidth. I dont know how to explain that, other than maybe the wg itself was shifted a bit to the side from the no port measurement, causing it to be farther from the mic as I went off axis. Need to tighten up my measurements next session.

The first set is the wg/hf driver with no ports, and the second set is with ports and the mid drivers are hooked up to the amp and muted. I've also included sets with angles picked out that show the difference between ports and no ports.
Attached Images
File Type: png eoswg synergy no mid ports.png (125.3 KB, 1589 views)
File Type: png eoswg synergy with mid ports.png (128.8 KB, 1508 views)
File Type: png eoswg synergy 0deg.png (53.3 KB, 204 views)
File Type: png eoswg synergy 20deg.png (53.7 KB, 171 views)
File Type: png eoswg40deg.png (58.7 KB, 173 views)
  Reply With Quote
Old 27th November 2015, 11:49 PM   #3
natehansen66 is offline natehansen66  United States
diyAudio Member
 
Join Date: Mar 2011
Location: Rochester, MN
Here's the polars for the hf/mid combo. The xo is acoustically about 6th order at 1.2khz.......I didn't spend a lot of time optimizing it. I took the liberty of extending the gate out to 5ms and adding a 5 cycle freq dependent window to get a little better idea of the low end response. A 300hz hp looks like no problem, even for this small horn. When the hf driver is eq'd flat the levels are nearly matched. I put the horn on a stack of a couple sealed 15's and knocked up a quick xo. I've been in the basement listening in mono all afternoon and it actually sounds quite good as it is. There's something about this speaker that my main rig (which I've been optimizing for a year now) can't quite do.....and this is just a rough prototype! I was worried that pushing this little cd that low would be pretty bad but it's actually holding up quite well even at higher spl.

The whole point of this experiment was to see the effect on the hf response of the mid ports to see if it's worth building a larger set for my main system. Going in I was quite skeptical and I've built enough junk to not have any pride in saying it didn't work out. That said things are looking good so far.....
Attached Images
File Type: png eoswg synergy polars.png (109.6 KB, 330 views)
  Reply With Quote
Old 28th November 2015, 12:21 AM   #4
gedlee is offline gedlee  United States
diyAudio Member
 
gedlee's Avatar
 
Join Date: Dec 2004
Location: Novi, Michigan
Hi Nate,

Is the idea to improve the waveguides ability to go lower in frequency to a lower crossover point? But then how do you match the woofer directivity to that of the waveguide? And won't even a waveguide that size loose control below say 700 Hz.?

The ports made far less effect than I would expect as well, but then they are very small. You probably can't do good polars for the mids in your situation right? I would be very interested in seeing those.

PS. I'd love to plot those in my PolarMap program. You've sent me data before right?
__________________
Earl Geddes Gedlee Website

Last edited by gedlee; 28th November 2015 at 12:25 AM.
  Reply With Quote
Old 28th November 2015, 12:35 AM   #5
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 natehansen66 View Post
I've been in the basement listening in mono all afternoon and it actually sounds quite good as it is. There's something about this speaker that my main rig (which I've been optimizing for a year now) can't quite do.....and this is just a rough prototype! I was worried that pushing this little cd that low would be pretty bad but it's actually holding up quite well even at higher spl.
Neat!

Here's some things to try to take it to "the next level."

1) get HolmImpulse or Arta so you can measure phase
2) Measure the distance from the throat to the midrange taps. Now set the lowpass on the midranges to achieve an acoustic lowpass that's about 3rd or 4th order. The idea is to introduce a delay that's enough to keep the midranges from radiating until the tweeter "catches up"
3) Then start tweaking the lowpass slope and the low pass frequency until the phase 'snaps into' place


Basically if you juggle the xover slopes, the midrange distance, etc, you can get the phase and frequency to behave like it's a single driver. Be sure NOT to flip the polarity of the tweeter. You probably want to double check the impulse of the drivers to insure that they're labeled correctly too. (Occasionally you'll find that drivers labeled for positive polarity aren't.)



It's really easy to get the response flat, the key is to get the phase right

Once you do that, it's really eerie, the speakers seem to disappear.
  Reply With Quote
Old 28th November 2015, 12:40 AM   #6
xrk971 is offline xrk971  United States
diyAudio Member
 
xrk971's Avatar
 
Join Date: Oct 2012
Location: Metro DC area
Mini-Synergy Horn Experiment
Nice work! You sort of made yourself a Red Spade PSE144. Cool that you are noticing something about it that sounds better than your main rig. It's the controlled directivity of 400Hz on up from a point source. There is less splash from walls and other surfaces so SNR is higher. The sensitivity is high so the distortion is low. I remember the first time I made one and listened. It's a stunning sound - can't stop listening.

Red Spade Audio PSE-144
  Reply With Quote
Old 28th November 2015, 12:53 AM   #7
natehansen66 is offline natehansen66  United States
diyAudio Member
 
Join Date: Mar 2011
Location: Rochester, MN
Earl - the idea here was to test the effect of the mid ports on the hf response with a wg I already have built. If/when I build a wg specifically for a Synergy horn it will be large enough to maintain directivity to about 300hz where it will hand off to a couple of side by side 15s. That said, I was surprised to see that this wg is still at almost 90 at 500hz. The resolution isn't there at 500hz of course, but I've done enough comparison of outdoor vs indoor data and I've found that at least the rough polar is accurate....even if the details are obscured.

I have sent you data in the past, but that was an outdoor measurement session with a speaker hanging off the back of my deck. Outdoor measurement season has ended in Minnesota . You need about 6ms of clean impulse for your sw, right? The best I can do - when I have my living room cleared out - is about 4ms at a 4' distance. If that's workable for you I'll see about doing that in the next month or so.

Patrick - I can measure phase just fine with a dual channel measurement in REW. However, it's my understanding that you need a fair amount of overlap between the hf and mid to get a linear phase xo (without resorting to FIR filtering). As it is I've got maybe 100 or 200 hz overlap before I hp the compression driver.

I have some ideas about making the effect of the ports even less, and some tests of this new configuration on a flat baffle have shown to have the effect of extending the mid response a bit. I'm going to try that at some point to see how it works out. I've also got some foam throat plugs cut for this wg that I'll try and see if that lessens the effect.
  Reply With Quote
Old 28th November 2015, 12:58 AM   #8
natehansen66 is offline natehansen66  United States
diyAudio Member
 
Join Date: Mar 2011
Location: Rochester, MN
xrk - Seems Paul and I are on a similar path.........he just made one first! I've been thinking about an EOS Synergy for a long time but now I have the ability to make it happen. FWIW my main rig is a high eff job with about a 120 pattern down to 300hz so it's no slouch.

Using three mid drivers is a bit odd as far as wiring goes. I've got them wired in series now because I doubt the test amp I'm using is stable under 2ohms. My main amps are Hypex uCd180 and I'm told by an engineer there that it will be stable under 2ohms. We'll see when I get there!
  Reply With Quote
Old 28th November 2015, 04:18 AM   #9
AllenB is offline AllenB  Australia
diyAudio Member
 
Join Date: Oct 2008
Quote:
Originally Posted by natehansen66 View Post
I don't see a square section horn as being the ideal shape for the wave,
A sperical sector is fine having a square cross section, the issue is the round cone. It can be done.
  Reply With Quote
Old 28th November 2015, 04:52 AM   #10
natehansen66 is offline natehansen66  United States
diyAudio Member
 
Join Date: Mar 2011
Location: Rochester, MN
Quote:
Originally Posted by AllenB View Post
A sperical sector is fine having a square cross section, the issue is the round cone. It can be done.
I don't follow........are you assuming we're driving it with a spherical source and the transition from round to square is the issue? Or that we have a plane wave source (more or less) and we need to transition it to spherical? The latter is my understanding of the purpose of the OS profile. To do the transition as quickly as possible with low diffraction from plane to spherical. I think Earl's phase plug patent covered the transition to a square section.

This is one area (of many!) where my understanding is rudimentary at best
  Reply With Quote

Reply


Mini-Synergy Horn ExperimentHide 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
Synergy Horn probabilities? speakrsrfun Multi-Way 5 13th September 2015 10:18 AM
omnnidirectional synergy horn? Slothrop Multi-Way 25 26th January 2015 05:37 PM
Dynamikks Synergy horn angeloitacare Multi-Way 4 22nd July 2013 08:35 PM
Unity/Synergy horn 454Casull Multi-Way 9 10th June 2013 06:35 PM
synergy like horn, using CD rvrazvan Multi-Way 5 4th November 2011 09:28 AM


New To Site? Need Help?

All times are GMT. The time now is 12:08 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki