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Hey folks, I’m Duane and I just registered here, this being my first post.Without reading all through this thread, I hope you don’t mind me asking:How many of you have tried using two exciters per panel - directly opposite from each other - one on each side of the panel, and wiring them so that while one “pushes”, the other “pulls”? What might they sound like set up that way?Asking ‘cause that’s what I have in mind. I recently bought several Dayton “Thrusters” and a few pieces of 2’x2’ Foamular to play with. Ready to start shaping..
Have you guys seen these speakers by techtonichttps://www.tectonicaudiolabs.com/professional-audio/dml-speakers/Looks like they use a thin piece of aluminum for their DML panels
How many of you have tried using two exciters per panel - directly opposite from each other - one on each side of the panel, and wiring them so that while one “pushes”, the other “pulls”? What might they sound like set up that way?
I have in my pocession, two DIY, 79''tall by 28 inch wide by 1/4 inch thick prototype NXT panel speakers. They will soon have a seventh NXT ''exciter'' mounted to the rear of each panel(all in a vertical array, evenly spaced but no one exciter in the exact middle of the panel). Impedance : 4.67ohms.Due to 7 exciters per panel, I estimate a sensitivity of 95db, maybe a bit more.For those who are interested, I have followed the design of PODIUM LOUDSPEAKERS in the U.K. BUT, ........mine are somewhat larger with more exciters per panel than their biggest model(Model1 : 5 exciters per panel).I have posted on this forum as it is the closest thing that relates to this type of speaker ( sort of).The panels are made from GATORFOAM which is a polystyrene core sandwiched between a very thin wood fibre composite material known as LUXCELL (a kind of wood veneer ).The exciters create a DML (DISTRIBUTED MODE LOUDSPEAKER) speaker which is essentially a large surface made to vibrate with random modal excitations.I am stunned at how good these things sound but it's been a long hard road finding the right panel material and positioning the exciters to obtain optimum fidelity.They can produce immense bass at times(but not sub woofer like) and have a transparency, speed and midrange resolution to die for.They still need mounting in frames (no time lately ) so they rest vertically up against the edge(with a piece of spongy foam) of my horn speakers at the momentI can post some pics. if anyone is interested?
Can you give us exact dimensions and positions of the Exciters? And what kind of exciters?
Not visited the thread for quite a while so just catching up...... Unless the exciter design is very poor, a DML's HF extension is determined by the panel material's compressive strength and internal damping properties, not the exciter performance. Aluminium honeycomb panels are excellent and Nomex honeycombs are also a good compromise for high comp strength and low panel mass. The low panel mass of, paper skinned, aluminium honeycomb panels gives 93/94dB @1W sensitivity when used with a decent exciter. Aluminium honeycombs with high quality skins give flat HF extension to 25kHz and decent output above 30kHz.DML panels have to be VERY big to make bass flat bass below 150Hz. Panels are packed with modes at higher frequencies but there are only 3 fundamental modes at low frequencies ( length, width and the lowest diagonal mode ). Panels are sparsely modal at LF and densely modal at HF.......consequently LF performance is seriously lumpy.When developing a DML, try measuring the off axis polar response and at multiple different mic distances too; DMLs are strange things and don't behave anything like conventional moving coils. DMLs are simultaneously in phase and out of phase with themselves at the same time!! Small changes in mic position can have a huge effect on measured performance.
Typical you use white glue. But there are pva-based craft glues that should work just as good. Mix it with the same amount of water and glue and use a foam roller to apply it to the panels. You can use a hair dryer to help drying.There are different suggestions how many times you should treat the panel for best sound. Most treat once or twice. Someone suggested to treat the side with the exciter twice and the other side once.After this the panel feels a bit like sand paper.
