A Study of DML's as a Full Range Speaker - diyAudio
Go Back   Home > Forums > Loudspeakers > Full Range

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 6th April 2015, 11:26 AM   #1
xrk971 is offline xrk971  United States
diyAudio Member
 
xrk971's Avatar
 
Join Date: Oct 2012
Location: Virginia
Default A Study of DML's as a Full Range Speaker

I had some cheap exciters that I got from PE a while back and tested them out a while ago with a full 20x30in FC panel here:

Foam Core Board Speaker Enclosures?

I found that a large 20in x 30in panel can sound quite good with nice bass extension and a snappy transient response:

Click the image to open in full size.

Impedance:

Click the image to open in full size.

Frequency Response & Harmonic Distortion:

Click the image to open in full size.

Impulse Response:

Click the image to open in full size.

The results were interesting in that it sounded nice - with surprising bass and good midrange. I thought nothing more about it until recently prodded by the master of DML, CLS. He has worked on this extensively and is a treasure trove of good info. I since have discovered that you can really do some cool things with them by playing with driver placement, cutouts, adding mass, adding felt, adding ribs, making them huge, making them multi-way FAST, etc. the options seemed almost limitless. Take for example, a large center channel and a super 40Hz capable multiway that CLS built here: PIEZO NXT type panel and PIEZO NXT type panel

I feel like this technology just isn't getting enough attention. There are several very large threads on this on the web. It might be tough for a newbie to comb through. I am a newbie at this so thought I would document my journey for the Full Range forum to follow. I think it really could be a great full range speaker with some careful experiments. This will be really useful with some modeling using CAD and FEA modal analysis - such as available in many CAD packages like SolidWorks. One can play with shapes, cutouts, mass loading, variation in thickness and materials, boundary clamping conditions, etc. The idea is to spread the modes evenly with not any one mode dominating and causing a spike.

First thing is to play with it to get a feel of what we are dealing with. What is nice is that it is relatively cheap to play with. Exciters cost $3 to $20 ea and can be made by removing or cutting out large holes in the cone from an old driver and leaving the spider and VC to attach to the panel. Foam core or corrugated cardboard doped with shellac or PVA seems to be the materials of choice.

Some interesting facts:

1. Although it has no baffle, it is not an open baffle (OB) dipole in behavior - that is, there is no huge bass rolloff and it hits surprisingly low (40 to 50Hz is easy) for a zero baffle driver.

2. It is not a dipole but behaves more like a bipole or an omni.

3. It has very quick snappy transient response - nice drum sounds.

4. It is sensitive to how you mount it or frame it or hold it.

5. You are building a driver in reality - a driver and zero enclosure.

6. You want to avoid symmetric shapes and symmetric exciter placement in order to reduce the effects of the main symmetric transverse drum head eignmodes. Think reflection anti-symmetric shapes like uneven trapezoids, pentagons, blobs, etc.

7. It operates more by having high velocities and large areas for good efficiency vs large displacements - thus small drivers and large panels can be surprisingly loud.

8. The impedance is essentially "flat" relative to normal drivers in that there are modal peaks (many of them) but they range from nominal Re value (say 6 ohms to maybe 8 or 9 ohms throughout the 40Hz to 20kHz range - this presents a very flat load to an amplifier.

Here is a photo of a basic panel I was testing (right before I cut off some edges to form a trapezoid) - panels is about 1 square ft in size and made of standard dollar store foam core board. I suspended it with two pieces of twine from the top corners between a ladder to reduce the effects of edge boundary clamping:

Click the image to open in full size.

Then I started to play with mass loading by adding blobs of modeling clay (8, 5, 4, 2, 1, 0) so you can see the effect on the resonance modes and the harmonic distortion. What is neat with this test is you can do it live while playing music and immediately hear what sounds more pleasing to the ear. Note the 50Hz bass extension. It is also surprisingly efficient with 85dB and a puny little voice coil. These are 0.5m and 0.71v for equivalent SPL at 2.83v and 1m.

Frequency Response and Harmonic Distortion for...

No added mass:

Click the image to open in full size.

8 pieces of added mass:

Click the image to open in full size.

5 pieces of added mass:

Click the image to open in full size.

4 pieces of added mass:

Click the image to open in full size.

2 pieces of added mass:

Click the image to open in full size.

1 piece of added mass:

Click the image to open in full size.

Impulse Response of 1 piece of added mass, note the sharp transient capability with relatively low after pulse or ringing:

Click the image to open in full size.

I liked the sound of the 5 and 1 mass the best and for a FAST with a 200Hz XO, the 5 mass might actually do fairly well. Of course, sound clips to follow once I have more time to work on this. Just to demonstrate how quick and easy this is, I did all these experiments in less than an hour including making the DML.
Attached Images
File Type: png Trapezoid-DML-80mass.png (396.1 KB, 768 views)
File Type: png trapezoid-no-mass.png (146.4 KB, 765 views)
File Type: png trapezoid-8-mass.png (146.4 KB, 760 views)
File Type: png trapezoid-5-mass.png (151.4 KB, 759 views)
File Type: png trapezoid-4-mass.png (151.7 KB, 754 views)
File Type: png trapezoid-2-mass.png (151.3 KB, 752 views)
File Type: png trapezoid-1-mass.png (143.7 KB, 754 views)
File Type: png trapezoid-1-mass-ir.png (40.5 KB, 750 views)

Last edited by xrk971; 9th April 2015 at 12:09 PM.
  Reply With Quote
Old 6th April 2015, 11:32 AM   #2
diyAudio Member
 
Join Date: Jan 2012
What happens if you add the mass in a radial pattern?
  Reply With Quote
Old 6th April 2015, 11:35 AM   #3
xrk971 is offline xrk971  United States
diyAudio Member
 
xrk971's Avatar
 
Join Date: Oct 2012
Location: Virginia
Good question, and although I have not tried it, it may just be the ticket. Several conventional driver designs use a pentagon of spokes to stiffen the cone. I can try this the next time I set up for experiments. Thanks for the suggestion.
  Reply With Quote
Old 6th April 2015, 11:48 AM   #4
diyAudio Member
 
Godzilla's Avatar
 
Join Date: Nov 2005
Location: New York
Subjectively, these seem to sound best on large glass windows well away from the corners. I no longer have them. I think they could be a good solution on my ceiling to notify the people above when they are making too much noise.
  Reply With Quote
Old 6th April 2015, 11:51 AM   #5
xrk971 is offline xrk971  United States
diyAudio Member
 
xrk971's Avatar
 
Join Date: Oct 2012
Location: Virginia
You have tried them on framed glass windows and they actually had bass? I would have thought the glass is too heavy and stiff. I have a glass wall on the front of my office at work. Maybe a couple mounted there would put some music into the hallways.
  Reply With Quote
Old 6th April 2015, 11:51 AM   #6
diyAudio Member
 
Join Date: Feb 2014
Location: Taiwan
I'll be following this closely as I am very interested in this.

Thanks for posting!
  Reply With Quote
Old 6th April 2015, 12:56 PM   #7
diyAudio Member
 
Join Date: Aug 2013
Location: Denver, CO, USA
XRK, if you'd like to try correlating modal analysis results with measured responses I can do a couple runs of your tests. I just need the weight, dimensions, and locations of the exciter and the masses. Any information needed to create an accurate model.

Unfortunately, I can't give you information about damping or relative amplitude. Only estimated frequencies and mode shapes. I suspect the mode shapes will be the most useful. Also, as we go we can try to refine material properties to get more accurate frequencies.
  Reply With Quote
Old 6th April 2015, 12:58 PM   #8
xrk971 is offline xrk971  United States
diyAudio Member
 
xrk971's Avatar
 
Join Date: Oct 2012
Location: Virginia
Quote:
Originally Posted by MuddJester View Post
XRK, if you'd like to try correlating modal analysis results with measured responses I can do a couple runs of your tests. I just need the weight, dimensions, and locations of the exciter and the masses. Any information needed to create an accurate model.

Unfortunately, I can't give you information about damping or relative amplitude. Only estimated frequencies and mode shapes. I suspect the mode shapes will be the most useful. Also, as we go we can try to refine material properties to get more accurate frequencies.
MJ,
Thank you for the offer! I will get back to you when I take another shot at this and measure the masses and their placement carefully.
X
  Reply With Quote
Old 6th April 2015, 01:54 PM   #9
Elias is offline Elias  Finland
diyAudio Member
 
Elias's Avatar
 
Join Date: May 2003
Location: Where you live
Where is a directivity plot ?

Then we'll know how usefull is this concept


.
__________________
Liberate yourself from the illusion of two speaker stereo triangle
Dipole Bass vs Monopole Bass Stereophonic Sound from a Single Loudspeaker 3 Speaker Linear Stereo Matrix Wavelets
  Reply With Quote
Old 6th April 2015, 01:59 PM   #10
BYRTT is online now BYRTT  Denmark
diyAudio Member
 
Join Date: Dec 2009
Thanks sharing very interesting.

Maybe stupid but could a exciter or more exciters exchange those 6,5" woofers on your trynergy build or even make the four insides in a Synergy horn vibrate with exciters instead of cone drivers.

Click the image to open in full size.
Picture linked from Trynergy thread found here Presenting the Trynergy - a full range tractrix synergy..
  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
Full Range Voice Range single speaker and enclosure loninappleton Full Range 23 8th May 2014 11:14 PM
Proposal for a full range speaker radio Full Range 20 23rd April 2014 05:03 PM
Design Study: Full Range Line Array Dumbledog Multi-Way 5 27th October 2013 12:45 PM
Full range speaker package. perceptionchanges Swap Meet 1 15th July 2013 03:08 AM
Full range active speaker zebra100 Full Range 10 24th August 2009 11:28 AM


New To Site? Need Help?

All times are GMT. The time now is 06:43 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2015 DragonByte Technologies Ltd.
Copyright 1999-2015 diyAudio

Content Relevant URLs by vBSEO 3.3.2