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Old 10th September 2012, 02:00 PM   #581
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Quote:
Originally Posted by SEdwards View Post
Has anyone tried putting an exciter inside of a periodic structure? (sphere, cylinder, squashed version of them) This would eliminate boundary effects. I haven't read enough about excitors to have an idea of whether you can actually excite such a structure, though.
I have tried it in a cube shaped 6"*6"*6" structure but it sounded very bad..dosent work that way in my opinion
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Old 11th September 2012, 01:23 AM   #582
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Quote:
Originally Posted by Lunchietey View Post
How has it worked out for you? I figure it would be along the lines of a F.A.S.T. type system. ....
Pretty good I'd say. Some of the merits (already mentioned before) are good enough for me to give up horns and play with these cheapo drivers and various boards... etc.

I got 40Hz or so at the low end at the best case, but it's still not enough for me, so I use subs. Then, since subs came for help, there's no reason to push the main board all the way down. 80~100Hz is easy for a decent size board.

The top end is trickier. Sometimes you just can't get good enough top octave from some types of panels. A flattened drop above 10kHz is typical. If that's the case, then reinforcing the board (to get better rigidity) is the way to go instead of adding a super tweeter. Because one of the merits is the almost omni dispersion. Ver few super tweeter can do that. When done right, it can play beyond 20kHz. (It's pretty amazing to hear an HF unit in such size and dispersion.)

This thing looks easy (and funny or even laughable) at the first sight. It's also easy to get a fresh first impression by its refreshing sound. The hard part is refining it -- solving all kinds of problems while retaining the good parts.
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Old 11th September 2012, 05:04 AM   #583
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Sounds promising! On another forum, a member(Zygadr) discusses using VH EPS styrofoam, I live in the same city as him(30 min drive to that foam shop), so will be using that exact foam as a first material and 3mm ply as well for comparison. Hopefully even the size panel I'm looking at will do 80hz at mid 80db sensitivity , as then I can use 4 for front L&R and rear L&R in my main TV room for TV and basic stereo use with My dual 8" sub(aaron sub-120) which is a lovely punchy sub.

I am building a dedicated theatre with lots of power and high efficiency speakers so in my tv room its adequate. I will attempt an nxt centre panel as well for the tv room but as it will be a different size and shape I don't know how that will affect sound? I was thinking one of the large hollow areas of the TV cabinet(it's basically 3 cubes, the outer 2 have glass doors, the other has no door and has the current centre speaker) and making a panel(VH EPS) that is almost the exact size of the opening and removing the back of that 'cube' so its semi OB if that makes sense. Then fitting a black cloth grille over the whole thing for protection/invisibility.

My goal are stylish, very thin panel type speakers that will sound 'acceptable' and by that i mean if its any better than HT in a box 3" speakers then I'm happy

Last edited by Lunchietey; 11th September 2012 at 05:13 AM.
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Old 11th September 2012, 07:44 AM   #584
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Like many other things, bigger is better.

And, one of the major character of DML is very wide dispersion. So in the experiment stage, it'd be better to try it in a relatively open space first.

It can easily out-perform ordinary 3" speaker in a box in many ways, but stuffing it in a TV cabinet will probably degrade too much of its performance.

Have fun and good luck.
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Old 11th September 2012, 08:33 AM   #585
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Hmm, I figured putting it into a cabinet may be a problem, it will essentially be a 400mm deep frame but it will still create a 'cavity' and a long path for the sound to get around. Maybe if i line it appropriately I might be ok. Or maybe just have no centre? I could perhaps use that cavity for a subwoofer, and seeing as it will be directly btween the two panels may be good for imaging?

I have also considered some standard cone drivers for 80-250hz or so in flat panel designs, Visaton does a 31mm thick 5.25" woofer with highish qts that might be worth a look(4 per panel) with a simple 1st order crossover or something. Lots of experimenting to do!

Thanks for the info
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Old 12th September 2012, 09:04 AM   #586
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That's a bummer. I was hoping that with the decorrelated excitations we can get away with something like a pulsating sphere without cancellations (and with the ability to make it rigid with cross spokes). If I buy exciters at some point I'll surely experiment anyway.

@CLS - do you have any measurements of your giant panel?

Quote:
Originally Posted by Akrambash View Post
I have tried it in a cube shaped 6"*6"*6" structure but it sounded very bad..dosent work that way in my opinion
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Old 13th September 2012, 12:40 AM   #587
CLS is offline CLS  Taiwan
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Hi,

The only thing I have is very rough RTA to show the overall in room response. It's far from ideal to tell how this thing work. (Besides, my system is 2-way active / 3 front channels. Now this DML panel is only used in central above 80Hz or so...)

And DML is hard to measure correctly -- or, the traditional measurements don't reveal its performance properly. Like other wide dispersion devices, it's highly room/location-dependent. Correct or proper measurement for this thing is far beyond my capability.

About the shape, I think you don't want to enclose the vibrating sufaces. An excited flat surface is already splashing everywhere, so anything enclosed would be a waste of SPL (and further problem in resonaces inside that space).

Happy experiment anyway. Without doubt, it'd be an excellent toy with very high potential to get very good sound.
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Old 13th September 2012, 08:17 AM   #588
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Underfloor loading is the best for bass, you don't need sub woofers, if you have space under the floorboards and a detached house go with that!
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Old 13th September 2012, 08:57 AM   #589
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I don't have room under the floor(concrete on the ground) but theres loads in the ceiling!
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Old 13th September 2012, 09:29 AM   #590
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Your speakers would be very high or very tall, the space between floorboards is less than the space under floorboards, you could always try it. I have got 9 60 x 40cm full range planars hanging from the ceiling. They are not over floor loaded tho'. Just open backed.Do you live in a detached house if not the neighbours would be very unhappy. With plates shaking off shelves!
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