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

A Study of DML's as a Full Range Speaker
A Study of DML's as a Full Range Speaker
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 14th November 2019, 07:06 AM   #811
JMatt is offline JMatt  South Africa
diyAudio Member
 
Join Date: Nov 2019
Quote:
Originally Posted by Veleric View Post
Jmatt,
Very cool (both panels). But can you explain what you hope to achieve? Solid XPS is already the most efficient panel I've heard. Are you trying to make it even more efficient? Do you have another specific goal(s)? Or are you just seeing what happens? (I'm asking just to better understand what you have in mind, not to "challenge" your idea in any way!).
If you want to really maximize stiffness/weight (maybe you do, maybe you don't), you could make (mirror images) of your ribbed panels and glue them together back to back.
Thanks,
Eric
Thanks Veleric, I'm just experimenting a bit with what I have available. Originally I wanted to try a XPS honeycomb with wood veneer on both sides but it's just too difficult to source here.
  Reply With Quote
Old 15th November 2019, 12:03 AM   #812
Veleric is offline Veleric  United States
diyAudio Member
 
Join Date: Feb 2016
Quote:
Originally Posted by geosand View Post
Now your other statement about f0 depending on panel suspension. I assume you mean dampening of the panel (at least around the periphery.) i.e., going from an infinite plane structure to a finite one. Can you explain to me does such damping increase or decrease the F0 and are their equations that may describe the effect on F0 by dampening.
geosand,
Finally getting back to this question:
When I noted that f0 depends on panel suspension, what I meant by "suspension" has more to do with how the panel is held in place (or not), than how or if it is damped. That, for example, is the panel hanging from strings or clamped in a frame? While it is true that such frame might include a damping effect, with or without damping, the suspension mechanism has a pretty significant effect on f0 (and much more than damping alone does).
Engineers may refer to "suspension", "boundary" conditions" or "constraints" and generally be referring to how a structure is held. Some typical boundary conditions are :
1) Free,
2) Pinned, or hinged or "simply supported"
3) Clamped, built-in, or cantilevered

The first (free) means no support at all. Hanging from strings is about as close to "free" as you can get. The edges of the panel are not held in place so move (and rotate) freely without constraint.

The second (pinned) means the edges are fixed in place, but are still free to rotate, as if there was a hinge that ran around the entire perimeter of the panel. A panel whose edges are clamped around the perimeter between two narrow plates with a thin but soft foam would approach this condition.

The third, (clamped) means the edge is not only fixed in place, but held to prevent rotation at the point where it is held. A panel whose edges are clamped around the perimeter with a wide steel frame would approach this condition.

Regarding f0, the "free" conditions gives the lowest f0 of the three idealized boundary conditions that I described, "hinged" would have a higher f0, and "clamped" the highest of the three. I modeled (using finite element analysis) a particular panel with the three described boundary conditions and got f0 values of 37 Hz, 53 Hz, and 97 Hz for the free, hinged and clamped conditions, respectively.

Generally, the more restrictive the boundary conditions are, the more f0 is increased, as in the previous examples. I did find, however, that pinning just the four corners led to a lower f0 (19Hz).

All that said, I myself can't say what boundary conditions are best. It would seem that reducing f0 would be good for producing bass. But, interestingly, this patent claims that low frequency output is enhanced with clamped edges compared to free edges. Go figure...

https://patentimages.storage.googlea...99052324A1.pdf

Eric
  Reply With Quote
Old 15th November 2019, 12:11 AM   #813
Veleric is offline Veleric  United States
diyAudio Member
 
Join Date: Feb 2016
Quote:
Originally Posted by JMatt View Post
Thanks Veleric, I'm just experimenting a bit with what I have available. Originally I wanted to try a XPS honeycomb with wood veneer on both sides but it's just too difficult to source here.
I presume you mean the XPS honeycomb is hard to source, (not wood veneer) right? Did you try wood veneer over plain XPS? I've been planning to try that or similar myself. I suspect the foam is so light already that it's weight is small compared to the wood veneer. So making the foam even lighter may be only of marginal benefit.
Thanks,
Eric
  Reply With Quote
Old 15th November 2019, 07:57 AM   #814
JMatt is offline JMatt  South Africa
diyAudio Member
 
Join Date: Nov 2019
Ironically no, the XPS honeycomb I can cut on my CNC but finding a thin veneer that doesn't have MDF backing or in smaller quantities is the difficult part.
  Reply With Quote
Old 15th November 2019, 06:17 PM   #815
Veleric is offline Veleric  United States
diyAudio Member
 
Join Date: Feb 2016
JMatt,
Not sure where you are at, but this is where I'll probably buy veneer if I decide to try using it. Not cheap, beasonable prices and small sizes, just about right the right size for DML panels.

PSA - Pressure Sensitive Veneer - 24 Inch X 32 Inch

I've actually been thinking about trying wood veneer over 3/16 foamcore poster board. The weight of the paper outer layers is a negative, but on the plus side they'd be a good surface to bond the veneer to. I gotta do some calculations to see if it makes sense or not.
Eric
  Reply With Quote
Old 15th November 2019, 08:18 PM   #816
geosand is online now geosand  United States
diyAudio Member
 
Join Date: Jun 2019
A wood veneer over a foamcore sounds very similar to gatorbaord/gatorfoam? What Ziggy found like 10 years ago that at first he really loved and really started this whole DML DIY efforts, but in the end abandonned it in favor corrugated cardboard w/shellac and then High Density EPS, which both also had HF issues. Till he passed he went back and forth between the CC and HD EPS and never stopped trying to find a better material. He also was never successful in coming up with a suspension/frame mechanism that he felt sounded better than just leaving his tall panels on the floor and resting it against his horn speaker to hold it up. i.e., a sort of free standing panel.

Gatorboard had no HF, I assume because its Critical Frequency was probably way too low. I haven't done the calcs but I would bet its Critical Freq was probably around 10Khz if not a tad lower.
  Reply With Quote
Old 15th November 2019, 10:50 PM   #817
geosand is online now geosand  United States
diyAudio Member
 
Join Date: Jun 2019
And thanks again Eric, I used to think that suspension was just another distinction of a type of damping without a real difference. But theoretically if a free panel gives lowest F0, you would still have to fight with potentially more damping to quell things...whether that's a good trade off or not, I guess that's where the experimenting comes in.


A few years ago my thought was to use a panel that was suspended in a frame via magnetic forces, i.e., the use of strategically placed small magnets along the bottom edge of the panel and 2 side edges to hold the panel vertically and side to side and then a few more magnets at like the front/back corners to keep it in place from front to back. That's about as free as we can achieve I believe and If I use some really small neo's might even be affordable as long as the panel wasn't too heavy...ahhh to have money to experiment... there's the rub...


Now that NXT patent I've read before as well (ok read is probably too strong as the language is so stilted toward patent legalese as to almost not be in english lol). None the less, It does seem to imply Clamping all around may be better, but they mention ignoring F0 and instead basing their theory around F1 which I don't understand at all and doesn't seem to jive with their LowEnd = 2.5*F0 equation...However, this may be a later paper and they have refined some of their theory and it may be based more toward heavy duty PA systems that need that extra built in toughness as opposed to home HI-FI.


The one thing I did notice was that they seem to mention several other key patents as being "enlightening" such as the early "Warnaka" patent which I believe may pre-date even Bertagni's stuff...I'll try to see if I can find some more of these foriegn patent docs NXT specifically mention that seemed to guide their own patents and theory...


Right now, I believe that NXT may have been playing a little loose with their theory and some of the later patents and research from others in academia seem to point that out and have some better clues/explanations...



So I think I have enough various different theory info and equations available now in terms of analysis of panels to determine which panel material might give me the best starting point for my design as well as best suspension...something which I have to do as I dont have the luxury of $$ or the wood/metal skills or equipment to endlessly experiment. Time I have, $$$ no :-( For me its start with whatever the theory says is a good place to go, then spend more time to experimentally play with various damping techniques to come up with a usable solution that will sound great. Thus all the tech questions...as always, you've been very helpful...and I'm sure I'll have a few more...
  Reply With Quote
Old 16th November 2019, 12:04 AM   #818
xrk971 is online now xrk971  United States
Got Foam?
diyAudio Member
 
xrk971's Avatar
 
Join Date: Oct 2012
Location: Metro DC area
A Study of DML's as a Full Range Speaker
I flipped my panels around so that the exciters are front facing. I added some plastic modeling clay to the magnet to give it more mass in hopes of giving it more bass authority. The highs sound clearer now. Playing Bruce Springsteen 'Blood Brothers' - sounds fantastic. Then Ahmad Jamal's 'Ahmad's Blues' - very nice drums and pianos, and could hear ambience in night club very clearly (superb recording from 1955?), then next up was Lana DelRey's Summertime Sadness (Asadinho mix) - can actually hear some bass dance drums. What surprised me most is how well it played Metallica's 'Enter Sandman". Metal guitar and drums is usually hard to get right - not perfect, but very enjoyable. Patricia Barber's 'Manha de Carnaval' was refreshingly very lifelike - like you are there. Steely Dan's 'Hey Nineteen' sounded a bit too bright and forward. Buddy Guy's 'Five Long Years' was very good - nice visceral feel of his pain when he cries "You've got to know what I am talking about." These speakers really have some highs avaialble and great mid range. I measured about 3.5 vrms and that was about as loud as I could play it comfortably, about 85dB at listening position with my sound meter.

I almost forgot to mention, I am powering them with my very best reference amp and that seems to make a very nice difference. Source are FLAC or WAV files from Jriver on PC through Focusrite 2i4 DAC feeding a Yarra/Melbourne preamp, which drives a 50w SE Class A amp with microwave transformer 67mH 0.5DCR choke reactive load and SLB power supply with 37Vdc and 4.7A bias current (Hugh Dean's Glass Harmony). So, give it your best amp, you might be surprised how good it sounds!
A Study of DML's as a Full Range Speaker-dml-xps-test-gh-melb-10-jpg


A Study of DML's as a Full Range Speaker-dml-xps-test-front-class-08-jpg

A Study of DML's as a Full Range Speaker-dml-xps-test-front-putty-09-jpg
Attached Images
File Type: jpg DML-XPS-Test-Front-Class-A-08.jpg (82.0 KB, 199 views)
File Type: jpg DML-XPS-Test-Front-Putty-09.jpg (85.7 KB, 200 views)
File Type: jpg DML-XPS-Test-GH-Melb-10.jpg (407.3 KB, 134 views)
__________________
XRKaudio https://www.etsy.com/shop/XRKAudio

Last edited by xrk971; 16th November 2019 at 12:25 AM.
  Reply With Quote
Old 16th November 2019, 12:29 AM   #819
geosand is online now geosand  United States
diyAudio Member
 
Join Date: Jun 2019
Thanks XRK for those sources. I'm looking for good test material. Can someone also provide some digital sources (stream/FLAC/CD) that can show the amazing difference between a Cone Speaker and a DML either in the spacious soundstage area or especially in the barely imperceptible things that you can clearly hear in a DML but pretty much can't in a cone speaker, because of resolution or other issues. I.e., What I effectionately call the "WTF recordings". Those recordings you have heard a million times over on some great cone speakers of any design and then you tried them on your inexpensive experimental DML panel and there magically appeared sounds you have never heard before.
  Reply With Quote
Old 16th November 2019, 01:01 AM   #820
xrk971 is online now xrk971  United States
Got Foam?
diyAudio Member
 
xrk971's Avatar
 
Join Date: Oct 2012
Location: Metro DC area
A Study of DML's as a Full Range Speaker
Try YouTube. Quality is not half bad many times.

Here are some:
YouTube

YouTube

YouTube

YouTube

YouTube
__________________
XRKaudio https://www.etsy.com/shop/XRKAudio
  Reply With Quote

Reply


A Study of DML's as a Full Range SpeakerHide 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
Full Range Voice Range single speaker and enclosure loninappleton Full Range 23 9th May 2014 12:14 AM
Proposal for a full range speaker radio Full Range 20 23rd April 2014 06:03 PM
Design Study: Full Range Line Array Dumbledog Multi-Way 5 27th October 2013 01:45 PM
Full range speaker package. perceptionchanges Swap Meet 1 15th July 2013 04:08 AM
Full range active speaker zebra100 Full Range 10 24th August 2009 12:28 PM


New To Site? Need Help?

All times are GMT. The time now is 03:05 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Copyright ©1999-2019 diyAudio
Wiki