DIY Flat Panel Speaker Love

[Zene]

Unb ... your 16" x 24" 1" XPS panel (no treat) with a DAEX 25 has a very impressive graph. I need a low output (no bass) panel. Do you still recommend that combination or might I go smaller with same exciter? Sanding is difficult here in apt.

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[Zene]

Be nice to know how to cancel?

[Zene]

Guys ...Don't forget pb types propogate more sound than say mdf as it is more flexible. Damping, if you remember, is not my first choice. The stiffer you can make it the less it will transmit sound. A "T" or I-beam shape does just that. Ultimate would be triangle shaped, but prob not worth the effort. Laminating different matetials only adds to the vibrating mass. It lowers the frequency, but does not go away

[bradley.s]

They look good. Once I figure out what I'm doing on regular speakers I'm going to give flat panels a shot. I look forward to seeing how you wind up dampening them.

[benjicon]

So finally finished these, really happy with the result. Suspending them with the fishing line worked perfectly. The xps appears to be floating in the enclosure. I used a small dowel in a tight hole as the tightening mechanism, i tied the fishing line through the dowel and i can tighten and loosen the top and bottom ones to center it up. Works a treat.

I used to have the panels just leaning against a wall, now they're in the enclosure they're is a big volume increase, the sound is very bright so I'm going to play with some damping behind the xps. If i simply grab the sides of the xps while listening the brightness dips and the sounds is more even. I haven't braced the Exciter on this version, this was very much a practice version, i made a bit of a mess of the edges of my panels so I'm going to do the panels again fresh and with that new version I'll brave the Exciter, test out lining the back of the enclosure with felt and test some other damping

Thanks to everyone who contributed to this thread, it was a wealth of information.

[Unbiasedsound]

Unb ... industrial grade high density pb is second only to a hard wood for acoustical damping for a wood product. Panzer wood comes to mind. It was used on Panzer tanks in WWII to deaden the impact. Of course there are better damping materials such as lead and gold. Tar is great, too. Forgot; you needed lower cost and not too messy. Can easily tell as it is 49" x 97" compared to regular 4' x 8' pb, and not nearly as flakey.
Mdf and Hdf are amoung the very worst as it rings like a bell. I know it's used in every speaker box you can imagine, but that is no indorsement of it's acoustical properties. Mfg's use it because it is cheap, machines well, glues great and holds fasteners. Customers insist on it because it looks nice and is heavy (so heavy = better?). I know mdf well as I have personllly built tens of housands of boxes from it. The majority were for car stereo and the no-knowledge boom-boom crowd could care less how it sounds. Even audiofools think it's great. They have been sold a bill of goods by sales for years. If you think I'm raving, I am not. It is just frustrating not being able to convince people to the importance of a good sounding box or even a frame in your case.
Damping and bracing inferior panels has been tried, but that just lowers the peaks.

I guess you are right about mdf having a lot of vibrations....I use to think mdf was better then particle board when it came to damping properties but I guess not....I just learned about constrained layer damping with a visco elastic damping material to further reduce vibrations.

I will be testing this damping technique on my splines/brace and even frame.

[benjicon]

[benjicon]

Thanks Unb, Thats what I was thinking, Only problem I can foresee with gluing them directly to the back particle board is that it would be permanent and then with the other side of the exciter 3M'd to the XPS if I ever needed to get to the wiring where the exciter goes to the terminal I'd be screwed. I might try and create a wood block with a circular recess that will snugly fit the magnet inside then screw that wood block to the backing so I could unscrew it if I needed access to the exciter at the back of the XPS. The trick will be finding a biscuit cutter thats close to the diameter of the magnet.

I did some further research today trying to find a neat way to suspend the XPS with fishing line, I have the little cotter pin eyelets at the top and bottom of each panel, I'm going to drill directly through the 4x2 frame and recess a few of these little guys ... https://www.homedepot.ca/product/pro...u%201001142184 .... top and bottom then tie off the line to a tension peg that will allow me to raise and lower the xps panel and keep it level. I'll get some pics of this soon.

[Unbiasedsound]

The brace/spline should be pretty solid....With your design you can just glue the back of the exciter directly on to the particle board....if it does not reach just cut a small piece of particle board the same size as the magnet and glue it on the back until it reaches the back board.

[benjicon]

Thanks Unbiasedsound , that was a great explanation. Makes perfect sense.

i have finished making some mounting enclosures for my 2'x2' xps panels out of 2x4 and particle board. At the top and bottom of my xps panels i drilled 3mm diameter holes, partially filled them with epoxy and then placed small cotterpins in each hole leaving only the loop showing, my intention is to suspend the panels in the enclosure via fishing line tethered to 2 points at the top edge and 2 points at the bottom edge.. in my mind this should give minimal contact on the surrounding edge and still allow some reflected sound from the reverse side.

Unfortunately now you've highlighted the importance of magnet braces i have to work out a way to support the magnet.

How firm do you recommend the brace to be? Should it be rock solid? Or can it be as simple as gluing some foam rubber between the back of the magnet and the inside of the enclosure?

[Unbiasedsound]

A exciters voice coil is basically supporting the magnets weight, which is one of the main reasons why they cant make larger exciters with larger magnets as the magnets weight will make the voice coil sag more the larger/heavier the magnet becomes. A brace and frame is needed to add support. The brace will hold the magnet in place while the frame will hold the panel material in place basically like a conventional cone or BMR driver. Voice coil sag=voice coil rub=Distortion

Also a free (without a brace) floating exciter moves both the panel material and the magnet since there is no (brace) support holding the magnet in place. At higher volumes the magnet will vibrate causing distortion....By holding and supporting the magnet in place with a brace the magnet will no longer move instead transferring all the vibrating energy into the panel material basically once again like a conventional cone driver. This will reduce distortion and increase accuracy.

This is why I always stress why a BRACE and a FRAME is very important.

[benjicon]

Hi Guys, just catching up on some of the latest posts here. Someone mentioned that "bracing the exciter magnet" was a considerations some of you have been making, Whats the benefit of doing this ?

[Unbiasedsound]

Today I want to talk about a DML Center Channel panel.....One of the best characteristics of DML and BMR is there MIDRANGE capabilities when it comes to voice intelligibility the designs are endless just do what you feel works best for you.

[Unbiasedsound]

With DML, does the surface texture of the panel facing the listener matter? Is there a difference between a hard polished surface vs a surface more like a paper cone driver.

Just do what ever you feel is best for you.

[bradley.s]

With DML, does the surface texture of the panel facing the listener matter? Is there a difference between a hard polished surface vs a surface more like a paper cone driver.