Synergy attempt without compression driver - diyAudio
Go Back   Home > Forums > Loudspeakers > Multi-Way
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Multi-Way Conventional loudspeakers with crossovers

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 10th February 2016, 01:19 PM   #1
onni is offline onni  Sweden
diyAudio Member
 
Join Date: Mar 2013
Default Synergy attempt without compression driver

I've been intrigued by the Synergy concept for some years but have some resistance against using compression drivers. The very high sensitivity makes them noisy with my amplifiers. But primarily I've gotten really nice results with the ScanSpeak R2604 in a waveguide which makes me want to try it.

A first sketch:
Click the image to open in full size.
Inside. The woofers are Faital Pro 8FE200.

Click the image to open in full size.
Outside view.

The size is about 50 x 35 x 30 cm (W x H x D, 20" x 13" x 12"), i.e. a quite compact synergy.

These are the horisontal polars of the R2604 in an early waveguide (210x130x85 mm):
Click the image to open in full size.

Click the image to open in full size.
Measured waveguide (the brown one).

Click the image to open in full size.
On axis, with phase.

Click the image to open in full size.
On axis with PEQ and LT.

Click the image to open in full size.
On axis with PEQ and LT.

Click the image to open in full size.
Distortion at 85 dB with 1.2 kHz bessel (for Harsch XO).

Click the image to open in full size.
Distortion at 94 dB with 1.2 kHz bessel (for Harsch XO).The R2604 should be better loaded in the bottom end with a 50 cm wide waveguide (synergy horn) and that should reduce the distortion to enable a 1.2 kHz crossover and 95 dB maximum level.

The plan is to 3D-print the first part of the horn (throat) and then use wood for the last part.

I'm quite new to Hornresp, but have tried a little:
Click the image to open in full size.

Click the image to open in full size.

Throat velocity (separate model) is 9 m/s at 2.83 V and diaphragm displacement is 1 mm. I've used 2 x 1" holes for each woofer in 19 mm MDF using minimal volume filler (measured the Vtc for the woofers at 350 ml).

The plan is also to have a leaky supercardioid setup for the woofers to stretch the directivity of the speaker down to below 200 Hz.

I'll post 3D-models later to show what I plan to print

/Anton
Attached Images
File Type: png r2604 synergy.png (6.3 KB, 1195 views)
File Type: png sketch2.png (4.8 KB, 1188 views)
File Type: jpg R2604 WG raw.jpg (52.1 KB, 1186 views)
File Type: jpg R2604 WG LT+PEQ.jpg (53.1 KB, 1183 views)
File Type: jpg R2604 WG dist 85dB.jpg (72.6 KB, 1182 views)
File Type: jpg R2604 WG dist 94dB.jpg (73.8 KB, 1178 views)
File Type: jpg R2604 WG LT+PEQ impulse.jpg (48.1 KB, 1304 views)
File Type: png hornresp power.png (17.3 KB, 1182 views)
File Type: png hornresp input.png (20.6 KB, 1186 views)

Last edited by onni; 10th February 2016 at 01:40 PM.
  Reply With Quote
Old 10th February 2016, 01:37 PM   #2
onni is offline onni  Sweden
diyAudio Member
 
Join Date: Mar 2013
Default CSD

I forgot the CSD plot for the R2604 in the printed waveuide:
Click the image to open in full size.

All measurements look very good to me, except the rising distortion below 1 kHz which should be (at least partly) fixed by a larger waveguide.

/Anton
Attached Images
File Type: jpg R2604 WG CSD 94dB.jpg (82.5 KB, 1167 views)
  Reply With Quote
Old 10th February 2016, 03:26 PM   #3
xrk971 is offline xrk971  United States
diyAudio Member
 
xrk971's Avatar
 
Join Date: Oct 2012
Location: Metro DC area
Nice.

How are you going to get the woofer bandpass to go past 1k (preferably 2k) in order to have a good overlap with 1k XO for tweeter? The steep cliff at 1k will make it impossible to do, say a Harsch XO at 1k. Or, with a larger WG, you expect the ring radiator dome to go well below 1k?

Will you print the whole thing WG and all? Commercial printer or in pieces then glue together?
  Reply With Quote
Old 10th February 2016, 04:52 PM   #4
diyAudio Member
 
Join Date: Apr 2011
I struggled mightily to make 8FE200s work in a 2-way synergy. I could get response out to 1.3 Khz (using a volume plug) but no matter what I did, I had a null around 900 hz. The configuration that minimized this null was with no enclosure around the back of the 8Fe200s and with those drivers draped with absorption. That was how I prototyped it but my celebration was premature.

Like you, I was trying for a small, tight box for each 8FE200, just big enough to fit the magnet and with the back wall of the box parallel to the horn wall. My conclusion was that reflections from the back wall were arriving 180 degrees out of phase at the port through the horn wall and cancelling. Others have shown successful use of the 8FE200 in larger enclosures. My advice is make sure you have enough space behind the drivers for enough absorption to absorb the back wave at the resonant distance.
  Reply With Quote
Old 10th February 2016, 04:59 PM   #5
onni is offline onni  Sweden
diyAudio Member
 
Join Date: Mar 2013
Quote:
Originally Posted by xrk971 View Post
Nice.

How are you going to get the woofer bandpass to go past 1k (preferably 2k) in order to have a good overlap with 1k XO for tweeter? The steep cliff at 1k will make it impossible to do, say a Harsch XO at 1k. Or, with a larger WG, you expect the ring radiator dome to go well below 1k?

Will you print the whole thing WG and all? Commercial printer or in pieces then glue together?
Good point! I'll probably need to print volume fillers as well. One upside of using the R2604 is that the membrane is in the horn throat and not deep inside a driver, so the notch from the reflection should be high in frequency.

I'll print the throat, maybe first 7-8 cm.

/Anton
  Reply With Quote
Old 10th February 2016, 05:46 PM   #6
koja is offline koja  Canada
diyAudio Member
 
Join Date: Oct 2009
Location: Ontario
very interesting work. I also share interest in extrapolating on Synergy approach and was thinking of inserting a tweeter in the back of this horn which Hoerst did with Visaton B200:
Horn-Sat
not quite sure how something like that could be done but the thought crossed my mind when I was messing with playing B200 through cardboard boxes (when breaking it in for use in my OB), and that driver does classical music and deeper voices like you would not believe it. but off a flat baffle and run FR it is just awful.

if there was a way geomerically to combine two drivers in a horn where the back radiaton is adding to the front outputs for increased sensitivity, that could also be interesting for CD use.

Last edited by koja; 10th February 2016 at 05:50 PM.
  Reply With Quote
Old 10th February 2016, 05:51 PM   #7
diyAudio Member
 
Join Date: Apr 2011
re' just printing the throat

I've done a rectangular wooden conical horn synergy with a square throat from BWaslo's spreadsheet. I did the round to rectangular conversion with modelling clay like most others. Unsatisfied with this and inspired by XRK's thread I just 3D printed an insert for the horn that does that conversion much more smoothly than I did with clay. Now I've got to scrape off the clay and slide the adapter back into the throat in its place and measure to see what improvement I got.

I think this insert approach is easier to execute than joining a wood section to a plastic printed section, provided one is comfortable working with wood in the first place. The hard part, for me at least, was doing the CAD for the adapter and prior to that, choosing an appropriate profile. I did this in Sketchup and generated the shape heuristically rather than mathematically. It looks a little rougher than it actually is or I would like but is at least a proof of concept. I just exported STL from the Sketchup drawing and sent it and $30. off to "Sculpteo". I felt very lucky when I got the piece back a few days later.

Some pictures below. The adapter is roughly 2" by 3.7" by 1.5" for a 90x45 horn. The third image is the google file itself showing the adapter in the horn. It ends about .5" short of the mid ports with final thickness of perhaps 1/32".
Attached Images
File Type: jpg front of adapter.jpg (70.7 KB, 203 views)
File Type: jpg back of adapter.jpg (63.6 KB, 224 views)
File Type: png RO Throat Transition.png (124.1 KB, 228 views)
  Reply With Quote
Old 10th February 2016, 07:22 PM   #8
onni is offline onni  Sweden
diyAudio Member
 
Join Date: Mar 2013
Quote:
Originally Posted by nc535 View Post
I struggled mightily to make 8FE200s work in a 2-way synergy. I could get response out to 1.3 Khz (using a volume plug) but no matter what I did, I had a null around 900 hz. The configuration that minimized this null was with no enclosure around the back of the 8Fe200s and with those drivers draped with absorption. That was how I prototyped it but my celebration was premature.

Like you, I was trying for a small, tight box for each 8FE200, just big enough to fit the magnet and with the back wall of the box parallel to the horn wall. My conclusion was that reflections from the back wall were arriving 180 degrees out of phase at the port through the horn wall and cancelling. Others have shown successful use of the 8FE200 in larger enclosures. My advice is make sure you have enough space behind the drivers for enough absorption to absorb the back wave at the resonant distance.
Alright, I'm going for a leaky cabinet and maybe there is a point in putting the vents directly behind the drivers.


Quote:
Originally Posted by nc535 View Post
re' just printing the throat

I've done a rectangular wooden conical horn synergy with a square throat from BWaslo's spreadsheet. I did the round to rectangular conversion with modelling clay like most others. Unsatisfied with this and inspired by XRK's thread I just 3D printed an insert for the horn that does that conversion much more smoothly than I did with clay. Now I've got to scrape off the clay and slide the adapter back into the throat in its place and measure to see what improvement I got.

I think this insert approach is easier to execute than joining a wood section to a plastic printed section, provided one is comfortable working with wood in the first place. The hard part, for me at least, was doing the CAD for the adapter and prior to that, choosing an appropriate profile. I did this in Sketchup and generated the shape heuristically rather than mathematically. It looks a little rougher than it actually is or I would like but is at least a proof of concept. I just exported STL from the Sketchup drawing and sent it and $30. off to "Sculpteo". I felt very lucky when I got the piece back a few days later.

Some pictures below. The adapter is roughly 2" by 3.7" by 1.5" for a 90x45 horn. The third image is the google file itself showing the adapter in the horn. It ends about .5" short of the mid ports with final thickness of perhaps 1/32".
Sure looks easier! My approach will however be very sensitive towards shape of the throat as the wave is in no way flat when entering the horn compared to a (good) compression driver. The R2604 is however quite light, which should make the connecting easier.

This is from a simulation I've done of a WG that should perform better than the one I've measured:
Click the image to open in full size.

Simulated result:
Click the image to open in full size.
Constant directivity from 2 kHz to 10 kHz. The low end should improve with a larger WG.

/Anton
  Reply With Quote
Old 10th February 2016, 08:01 PM   #9
onni is offline onni  Sweden
diyAudio Member
 
Join Date: Mar 2013
Default New hornresp attempt

I tried to get the response for the 8FE200 up to 2 kHz and arrived here:
Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

I've assumed that the throat adapter only needs to be 5 cm long. I also reduced the holes to 21 mm diameter (from 25.4 mm). Looks like this:
Click the image to open in full size.
Probably even better to make them oblong from diffraction point of view, but that reduces the possible length of the throat adaptor.

Another possible look:
Click the image to open in full size.

/Anton
Attached Images
File Type: png hornresp input2.png (19.6 KB, 1142 views)
File Type: png group delay2.png (16.5 KB, 1088 views)
File Type: png hornresp power2.png (16.8 KB, 1089 views)
File Type: png particle velocity2.png (12.7 KB, 1089 views)
File Type: png 21mm holes at 58mm.png (3.0 KB, 1086 views)
File Type: png sketch3.png (5.8 KB, 1087 views)
  Reply With Quote
Old 10th February 2016, 08:29 PM   #10
diyAudio Member
 
Join Date: Apr 2011
that looks very doable. You wouldn't get the same results using a compression driver, because, as you said, you'd have to add perhaps another 3 cm to the reflection distance. The L12 on my 8FE200 proto was 2.25" which suggest that your 5.8 cm is practical.

I noticed in doing these horn response sims that if, for example, you changed both your "Ap1" and "Lp" parameters to half the values in your posted model, you would get the same results - both for the frequency response curve and the offset throat particle velocity. If you can thin out the horn wall at the port location (e.g. frustrumize), then you can use a smaller hole and thus better polars If one takes this to the extreme, you end up with an extremely thin horn wall and an extremely small hole. What is the catch?
  Reply With Quote

Reply


Hide 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
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Synergy horn using inexpensive compression drivers? unaHm Multi-Way 44 3rd December 2014 09:44 AM
compression driver throat adapter length for synergy horn bqc Multi-Way 7 2nd August 2014 10:16 PM
Is this THE driver for a compact home Synergy DIY? mayhem13 Multi-Way 0 13th June 2014 08:02 PM
Next attempt: Synergy horn pair unaHm Multi-Way 0 18th May 2014 06:14 AM
FS: Silver Iris Coaxial 15" driver pair (sans XO and compression driver) theAnonymous1 Swap Meet 0 24th April 2007 01:09 AM


New To Site? Need Help?

All times are GMT. The time now is 09:30 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2016 DragonByte Technologies Ltd.
Copyright 1999-2016 diyAudio

Content Relevant URLs by vBSEO 3.3.2
Wiki