DIY Flat Panel Speaker Love

[rmeinke]

Re: DIY Flat Panel Speaker Love

:D Link to the mother of all DML threads - http://www.audiocircle.com/index.php?topic=70541.0

This thread ain't to bad either...

[Kornbread]

Re: DIY Flat Panel Speaker Love

The work has eased up, time to play.

Relieved, rounded and angled the corners to allow for more movement and release of stored energy as has been mentioned in past posts. Listening to the usual songs that brought out the nasal quality didn't seem quite as bad, but that is very much subjective.



The measurements with the corners relieved are very similar to the ones with only the tabs holding the corners. Some dips are now deeper and a few peaks are not quite as high.

Measurements with corners relieved.


With corners relieved vs tabs only in corners.


Waterfall plot and spectrograph. These seem to have become less and less lumpy as the panel has been allowed to move more freely.

[Kornbread]

Re: DIY Flat Panel Speaker Love

... and something not posted before, for what it's worth, group delay.

solid panel mounting.


with corner tabs


with corners relieved



rmeinke, I'm not subscribed to AC, if you think it would be of help over there, you are welcome to post my measurements but, if you wouldn't mind, please give credit for the measurements.

[Gary.M]

Re: DIY Flat Panel Speaker Love

This looks like a very nice panel. To make the best possible panel you will need to treat the flutes. Its work, but this has been the best approach over at AC when cardboard was thee material of choice. I've treated many... unfortunately, it takes a long time to harden from my experience.

One note Gary, try not to soak it... afraid the flutes might lose their shape. Kornbread is correct, it does soak in pretty quickly. Yours looks thicker but just watch it closely. It might be worth reading over the AC thread on treating cardboard panels but what I explained was the standard approach at the time.

Update on the PVS:water treatment... checked my treated panels and now after a week, they are CRISPY! Might be as firm as the shellac already with only a week of curing. The shellac took months and months to fully harden.

Will test a sample piece both with pva and shellac.

[Kornbread]

Re: DIY Flat Panel Speaker Love

Was treating some new material while listening to tunes on the DML and ... well ... Grrrrrrrrr.... these things are proving to be fragile.

[Kornbread]

Re: DIY Flat Panel Speaker Love

Thinned lacquer by 1/3 and very liberally brushed it onto both sides of single ply cardboard 36"x51". The DAEX32EP-4 was placed 14.4" from one side and 21" from top, if I calculated correctly this should be about the 2/5th's position. The corners were rounded using the lid from a 5 gallon paint pail as a template. The panel is hung using duct tape placed at 1/3 points across width with string holding that to the ceiling. The panel still smells very strong, I believe it will stop off gassing after it has completely dried.

Listening impressions; sounds more natural and relaxed than the exp. The whispeness (run your finger down an exp panel and you have the sound) is almost gone, mid bass seems warmer. Without the whispey, nasal, <insert your description here< treble and midrange sound cleaner.

This was the only functioning exciter remaining so I didn't listen to it long or at any volume in fear it might quit before taking measurements. This means I was unable to make a direct comparison of the treated cardboard vs the modified exp panel. Even at this low level the exciter did make the same sound heard before the others quit, (sounded as if it had come partially unglued from the panel) ... it had not. The fragility of these exciters are quit frustrating.

After looking at the measurements of this cardboard panel in free air vs the different measurements taken during the modding process of the exp panel one might come to the conclusion that some dampening of the panel and/or bracing of the exciter is more beneficial to an even frequency response than either solid or free air mounting.




Measurements.


Lacquer treated single ply cardboard suspended from ceiling frequency response. After some thought it occurred to me I'd seem a similar frequency response graph before while reading ... a popular high end audio magazine ... of a super expensive tube amp. There was a hump in response around 70 hz, valley around 200hz, (the sharp panel nulls at 200, 350, 450 and 700hz might combine to sound like a large valley in response around that area) followed by a hump at 1-2k, (large panel peak ~1-2kh) another valley in tube amp response around ~5kh (large dips in panel response at 3, 5 and 9kh) but the panel ends with a spike around 13kh where the super expensive tube amp tapers off the top end. It's not a perfect match, but there is something to be said for that type of response curve being pleasing to the ears.


Treated cardboard vs exp with corners relieved and tabs holding corners.


Treated cardboard waterfall plot and spectro.


These are just my measurements and ramblings ... YMMV ... Your Mileage May Vary ...

[Kornbread]

Re: DIY Flat Panel Speaker Love

Here is the frequency response of the treated cardboard vs modified exp panel. The difference in frequency response is very noticeable. Blue is the treated cardboard, red is the modded exp. To me it looks like the modded, lightly dampned/tab mounted and exciter braced exp panel had a more even frequency response.

[Gary.M]

Re: DIY Flat Panel Speaker Love

Kornbread, do you know what the failure mode of the DAEX32EP-4 is? Is it a mechanical failure, or is there a loss of electrical connection?

[Kornbread]

Re: DIY Flat Panel Speaker Love

Don't know if it's mechanical or electrical but have an idea what may be going on. How would I check? I've asked PE if they might have an exciter expert <<<(sounds kinky):eek: chime in on our thread, maybe he, or she, could offer some insight.


edit..... Checked the non-functioning exciters with my handy dandy radioshack digital multi-meter, both show an open circuit.

[Gary.M]

Re: DIY Flat Panel Speaker Love

OK, then something is causing the wires to the voice coil to disconnect, or the voice coil is burning out. If you push the driven part in and out gently does it move freely without making any rubbing noise?

[Kornbread]

Re: DIY Flat Panel Speaker Love

OK, then something is causing the wires to the voice coil to disconnect, or the voice coil is burning out. If you push the driven part in and out gently does it move freely without making any rubbing noise?

No noise, smooth.

[Gary.M]

Re: DIY Flat Panel Speaker Love

My guess is that the voice coil lead out wires are going open circuit. I think someone else has reported this on other exciters. I hope Parts Express is watching this thread as it should be fed back to the manufacturer.

[rmeinke]

Re: DIY Flat Panel Speaker Love

My guess is that the voice coil lead out wires are going open circuit. I think someone else has reported this on other exciters. I hope Parts Express is watching this thread as it should be fed back to the manufacturer.

This is exactly it. The thin leads from the exciter to voice coil breaks. I have had better luck with the Thruster than the Ultra but they both appear to suffer from this issue. The leads are solid copper and not flexible,woven tinsel leads like we see on the DAEX30HESF-4.

I'm ordering a few DAEX30HESF-4 along with a number of some DAEX25FHE-4... want to try the smaller voice coil exciters to go along with the bass shakers. The smaller the VC the more extended the high frequencies are so hoping to build some smaller panels specifically for playing 200Hz (approx.) and up.

[rmeinke]

Re: DIY Flat Panel Speaker Love

Thinned lacquer by 1/3 and very liberally brushed it onto both sides of single ply cardboard 36"x51". The DAEX32EP-4 was placed 14.4" from one side and 21" from top, if I calculated correctly this should be about the 2/5th's position. The corners were rounded using the lid from a 5 gallon paint pail as a template. The panel is hung using duct tape placed at 1/3 points across width with string holding that to the ceiling. The panel still smells very strong, I believe it will stop off gassing after it has completely dried.

Listening impressions; sounds more natural and relaxed than the exp. The whispeness (run your finger down an exp panel and you have the sound) is almost gone, mid bass seems warmer. Without the whispey, nasal, <insert your description here< treble and midrange sound cleaner.

This was the only functioning exciter remaining so I didn't listen to it long or at any volume in fear it might quit before taking measurements. This means I was unable to make a direct comparison of the treated cardboard vs the modified exp panel. Even at this low level the exciter did make the same sound heard before the others quit, (sounded as if it had come partially unglued from the panel) ... it had not. The fragility of these exciters are quit frustrating.

After looking at the measurements of this cardboard panel in free air vs the different measurements taken during the modding process of the exp panel one might come to the conclusion that some dampening of the panel and/or bracing of the exciter is more beneficial to an even frequency response than either solid or free air mounting.

Dang Kornbread... you beat me to the punch with the cardboard panels.

I'm still waiting on panels to dry a bit more. I am really surprised how fast the PVA treated cardboard has cured. How much stiffer is the lacquered panels compared to the untreated? I can only assume that as the lacquer dries the high frequencies will improve if even a little.

Hoping to get my old shellaced panels up and running too. This is a lot of fun...

[rmeinke]

Re: DIY Flat Panel Speaker Love

I had to laugh a little Kornbread... your first panel was solidly clamped between a solid wood frame now on this one seems to float in the air with strings and is as little damped as possible me thinks. :-)

All good learning though...