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

Planars & Exotics ESL's, planars, and alternative technologies

DIY Walsh driver revisited
DIY Walsh driver revisited
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 1st February 2018, 05:22 PM   #1021
altie is offline altie
diyAudio Member
 
Join Date: May 2010
Location: Portland, OR
I might take a crack at this soon. I'm wondering about drivers to sacrifice for a wideband tweeter. The obvious choice would seem to be a compression driver.

In terms of wattage per dollar and voice coil size though, a cheapo woofer might compete. There seem to be two sacrifices with going that way:
- Much lower BL
- Higher impedance in the upper registers

I'm mostly wondering about the BL. Which is more important for a driver like this: total power output, or BL?
  Reply With Quote
Old 1st February 2018, 07:15 PM   #1022
altie is offline altie
diyAudio Member
 
Join Date: May 2010
Location: Portland, OR
So far the Pyle PDS541 - Pyle PDS541 1" Titanium Horn Driver 1-3/8"-18 TPI - is looking like the best option if the metric is magnet and voice coil per dollar. 60oz of magnet and 2in of aluminum voice coil for $32 from Parts Express.

A couple other questions have come to mind about compression drivers:

At what frequency would a carbon fiber cone start to become pistonic?
I'm assuming that any compression driver will have very little if any xmax. According to the patent, that's one of the advantages of the Walsh design - less vertical movement for a given volume of air moved, if I understand correctly. I don't think the patent covered the math to determine when the cone would become pistonic though, unless it was buried in one of the bits about "successive finite integration in reverse". Any rough ideas or empirical estimates?

Is a compression driver voice coil sufficiently rigid to bond to a CF cone?
I'm guessing that this depends a lot on material. Given Pyle's reputation as a budget supplier, they probably also are not using any more or higher quality VC material than they can get away with, I would guess. Will a 2" aluminum compression driver VC just bend out of the way when trying to drive a CF cone?
  Reply With Quote
Old 1st February 2018, 07:17 PM   #1023
altie is offline altie
diyAudio Member
 
Join Date: May 2010
Location: Portland, OR
Yet another option might be lathing down the edge of the CF cone so it'll fit in the magnet gap, and winding a custom VC on it. There are a couple of barriers I can see to this:
- I have been looking for the better part of a day and have not found ANY stats on wire gauge and number of turns on a compression driver VC.
- It would be a lot of extra work, which I'm trying to avoid in order to keep the project fun and interesting at least for the start.

Maybe I'll put that idea off until later if bonding to the aluminum VC doesn't work.
  Reply With Quote
Old 1st February 2018, 10:05 PM   #1024
Sandasnickaren is offline Sandasnickaren  Sweden
diyAudio Member
 
Join Date: Feb 2015
Location: Stockholm
Altie Ive built a couple of Walsh type speakers and one of things I've learnt is that you should use a driver that is intended for full range. Otherwise you risk ending up with speaker that only plays the lower range in pistonic mode. The impedans curve is good indicator. The challenge is to find one with a voice coil close to 50 mm or 2 inch.
This master thesis have theory on bending wave .
http://publications.lib.chalmers.se/...ext/154618.pdf
  Reply With Quote
Old 1st February 2018, 10:34 PM   #1025
altie is offline altie
diyAudio Member
 
Join Date: May 2010
Location: Portland, OR
Sandasnickaren, glad to see you back. I actually just picked up a pair of Peavey 22XT wideband compression drivers that have - you guessed it - 2 inch voice coils!

I'm planning on using the resulting Walsh drivers (or trialling them at least) as wideband tweeters similar to the 500-20KHz labeled response range (https://www.google.com/url?sa=t&rct=...u-i-CVIIoFBozo). I'm sure the addition of a big old cone to them will change the frequency response, but at least the driver itself doesn't seem like it'll have a problem impedance-wise with higher frequencies.

My reason for concern about pistonic behavior is that I would like to keep away from that operating regime. I had forgotten that I already looked into this with an old DML experiment: Carbon fiber + nomex honeycomb sandwich DML panel construction project. I still have those panels around, so maybe my first step will be to try using these compression drivers as exciters for those panels. They have to have substantially stronger magnets than the Daytons I was using before. IIRC from that experiment I ended up with a fundamental bending frequency of something like 100-200Hz. Does that sound right in your experience?

I'll have to give that thesis a look again...
  Reply With Quote
Old 4th February 2018, 06:56 AM   #1026
jerryrigged is offline jerryrigged  United States
diyAudio Member
 
jerryrigged's Avatar
 
Join Date: Jul 2014
Location: Asheville, NC
Default *blink* OMG....I've started a novella....*L*

Altie, MHO on BL....I opted for a higher BL over just sheer wattage ratings. Generally, the 2 seem to go hand in hand, although that's not an absolute...

The 'logic' behind that being one is asking the 'motor' of the speaker to perform in a far different fashion than it was designed to perform. Instead of moving a relatively compliant diaphragm in a pistonic motion, we're wanting to compress the top of a truncated and rather stiff cone to create radial waveforms that descend and expand the widening skin of the cone.

As with a conventional driver, damping the waveforms at the greater circumference of the driven cone is highly desired....make that nasty IM stop 'n stay...

Easier to do (somewhat) with the typical cone surround, which for a Walsh is not....pistonic motion for the smaller cones I've opted to use exists, but is being damped to 'encourage' the radial excitation of the cone...

As for 2" dia. vc's, that was the size of the original Ohm Fs' and As', which were full-range drivers driving large base diameter cones of multiple materials. This arrangement, in my (perhaps flawed) opinion and approach, made use of the 'phase shift' from radial to pistonic due to the descent of LF waveforms into a 'region' of the cone where the vertical motion of the vc 'overruled' the radial radiation.

The crossover was physical in that sense....so, based on study of the heights, diameters, materials, and the basic profiles of the cones, I used an 'average' as a jumping off point to fabricate the current v3s', of which y'all have seen previously.

Thoughts on voice coils...
My 1st iteration, a pair that suffered 'vc heat death'; the entire coil of both fused....I was surprised that they had lived as long as they had, given the studied abuse applied...

The intent was to investigate the reported 'fails' of the F's and As'...they either cooked the vc's (db over-enthusiasm, too much too long....that is what fried my "v1's") or collapse of a cone segment (*L* 'transient telescoping': lf @ high db...my guess as to that malfunctions' cause). It's been reported that the early Ohms' 'sounded Great @ 200 watts....and cooked @ 201'.

My response to the former:
Apply a driver with a vc meant to withstand abuse; a Pyle PPA6 'professional woofer' with a 1" Kapton former, vented, 400 w. max., music/PA applications.

Since I don't run anything that can apply that level of wattage, the cone revision is totally different than its' original, and opinions/reviews tended positive marks (and the price was about what I wanted to spend on 4)

My recent cones up till now have been 5 mil aluminum...truth be told yet again, lithographic sheets gifted from a friend long ago back in Houston...
Again, the price was right...

I've acquired 2 mil aluminum since....and recently, 2 mil titanium...

Carbon fiber cones are intriguing, attractive on a number of levels...and at this point, would require acquisition of the means to create them Properly.
And the learning curve to make acceptable, accurate, and reproducible ones.

I've always made a minimum of 2 drivers. A single one exhibits the fact that one can walk around it, and the sound and response remain constant.

Duh...it's an omni, and should do such....and does, correctly.

Do a pair and one begins to experience why a Walsh driver, and the original Ohms, were and still are, *ah* 'subject to superlatives'....

Now...make 4....sit in the middle of them...apply program of choice.

Get back to me on what you think of it...

Oh, vc to cone attachment....I've left a narrow 'skirt' of the original cone on the circumference of the vc, creating a trough for the new cone to attach to, and a means of keeping your adhesive of choice from finding its' way down into the gap of the vc within the magnet. You will likely get upset if such occurs...
I know I was less than thrilled by that...the driver involved wasn't of any great value, but the time involved to get to that point was....

I don't see any huge difference in having the top terminus of the cone inserting into the vc, other than losing some degree of driven weight and mass of the entire assembly....
....which, IMHO, due to the physics of how and why the cone is being driven in the fashion it is, makes the mass & weight 'perhaps' not as much of an issue as a conventional driver, where that becomes more of a factor...

Just mind the glues' characteristics....you can and should be a Control Freak when it comes to 'sticky sh*t'....*L*
__________________
"Reality is that which, when you stop believing in it, doesn't go away." (Philip K. Dick)
  Reply With Quote
Old 4th February 2018, 07:05 AM   #1027
jerryrigged is offline jerryrigged  United States
diyAudio Member
 
jerryrigged's Avatar
 
Join Date: Jul 2014
Location: Asheville, NC
BTW, guys....It's nice to have some company around here....

The use of a compression driver on a DML panel strikes me as an interesting pursuit...driving a panel would seem to indicate employing a driver without large excursions but significant force to excite the panel...

Anyway....have@it....
__________________
"Reality is that which, when you stop believing in it, doesn't go away." (Philip K. Dick)
  Reply With Quote
Old 18th February 2018, 09:52 PM   #1028
jerryrigged is offline jerryrigged  United States
diyAudio Member
 
jerryrigged's Avatar
 
Join Date: Jul 2014
Location: Asheville, NC
....and, backing into the attractive qualities of carbon fiber applied to cones....

High Strength 3D Printing – Markforged

Not that I've got the disposable $ to drop a P.O. tomorrow, But....a CF cone with top & bottom edges suitable for my applications & parameters, some interior resonance reduction structure(s).....

Anyone got a winning Lotto ticket that they're planning to 'party away' anyway? *G*

Yeah, thought so.......and can't say I blame anyone for that response....
__________________
"Reality is that which, when you stop believing in it, doesn't go away." (Philip K. Dick)
  Reply With Quote
Old 20th June 2018, 10:10 AM   #1029
jerryrigged is offline jerryrigged  United States
diyAudio Member
 
jerryrigged's Avatar
 
Join Date: Jul 2014
Location: Asheville, NC
Default ....back from the Shadows again....

Hi, y'all...*S*

Despite, and contrary to (perhaps) popular demand...I persist in my form and format....Unretired retired....which comes off as a form of retread, which we generally experience as tire tread chunks on your fav interstate....

So far '18 is being.....Different....*punch esrever....*clunk*

(Tape on the Revox spins up....Sunny, the Pit/Plott, wanders in....bumps take-up 10" reel.....50ish ft. spins out, spider-webbing pet who freaks and flies....)

*survey (ob)scene*Sigh*shrug*

Well, just another miserable day in Paradise.....

YouTube

...which leads me to Anne Dudley's epic comment...

YouTube

(...of which, her piano solo at the end...which, per one 'audiophile critical source', is considered 'then', and IMHO *cough* still the best 'mic'd and recorded piano' in existence'....the brain and beauty behind the AON...)

One fan responded with this....

YouTube

Great for 'tune-ups'....

Back sooner....
Attached Images
File Type: jpg 20180520_175800.jpg (474.9 KB, 172 views)
__________________
"Reality is that which, when you stop believing in it, doesn't go away." (Philip K. Dick)
  Reply With Quote
Old 21st July 2018, 07:45 AM   #1030
jerryrigged is offline jerryrigged  United States
diyAudio Member
 
jerryrigged's Avatar
 
Join Date: Jul 2014
Location: Asheville, NC
Default .....oh, no...I Still don't believe it....

YouTube
or
YouTube

You can: Break your lease ~ Bust a move ~ Push an envelope ~
or just

Push It.

....which may inform as to my idiosyncratic taste in music of late....
Have been, and will always be, a FON to (the) AON...and the talent of Ms. Dudley...

Have been either so busy or just merely dazed at the first half of 2k18 that the 2nd whip'round wouldn't surprise one byte if gravity takes a Fail and Earth goes AWOL. Who dealt this mess, anyway?

...Oh, well..."Let's Play PONG."

(For 50k credit...Next time you do the PhysReHab group exercise @ Your CardioKlasse'........bring the 'tooth' speakers with and hit Play.

I kept threatening to take over their AV rack...carried the appropo acoutremon in muh bag'o shiticks....

Meanwhile...found another 8024 eq, and added a MX882, as I feel the need for more oxygen-free copper in my life....not necessarily on my body, but near..,
__________________
"Reality is that which, when you stop believing in it, doesn't go away." (Philip K. Dick)
  Reply With Quote

Reply


DIY Walsh driver revisitedHide 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
300b driver revisited. losacco Tubes / Valves 9 28th October 2015 10:21 AM
DIY Walsh Driver cjh Planars & Exotics 40 20th June 2015 04:15 AM
Ohm Walsh 2 need advice Sk8Ter Full Range 1 4th September 2011 05:51 PM
Suitcase Stereo revisited--Please help DIY--My last resort. Jimmer2000 Class D 52 17th August 2011 05:20 AM


New To Site? Need Help?

All times are GMT. The time now is 10:42 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki