@Andre Bellwood
Christian
Let me be clear, it is not a boost in the idea to get really more HF. It is just a trick that restore the level of one exciter (where there is a suspicion of destroying interference of several exciters)
Yes for sure. I suggested plywood just as a test material for a better understanding of what happens, what can be expected from the exciters. The better HF result from the twinwall polycarbonate compare to EPS in itself a proof that our understanding is right : lighter material, higher efficiency, lower HF.
The design of the exciter seems the only way... if there is a way. For exemple lower the inductance, increase the BL, reduce the mass ? If I remember, BMR engine has some pretty interesting features.
Don't give up! Finding the right academic paper have already help us to enter in unknown areas. Think to the topic just above. 2 years ago I had never said to be able to evaluate the low pass filters of a DML, to have some figures about efficiency neither to run some FEM or FDM simulation.
Christian
Good that you said all this, rather than I. Someone had been mudding the water for so long about those 10W 25mm Dayton Audio exciters.
Oh, about my liking or not the Dayton Audio exciters, they are not made for any serious work. Sure, you can add a few of them on one panel, but all you get is bit more sound, not quality. On the question of frequency response, you just can't get more than the exciter is designed for, can you, when you add the load?
And, stay away from those terrible patents!
And, that 2/5, 3/5 just like that YT guru..
I thought that the better HF from the polycarb twinwall was to do with it being a thinner, stiffer material. And it's non composite anisotropic.
I never considered the mere density could be the reason for better HF!
Here we go down another rabbit hole...
I think that the compressive strength is a major factor. With low density eps for example, the very high accelerations at hf cause the foam to compress locally rather than follow the exciter movement. Also damping affects HF more than LF. I doubt it has to do with the density itself, I would expect low density to assist at HF with compressive strength and damping held constant.
What about very small rocks, did anyone try that? Very small rocks will float, according to the witch scene from Monty Python.
Steve,
I agree in principal with moving microphone concept. And it works if you use noise and an averaging RTA for the measurement. But many people normally use the frequency sweep mode in REW for frequency response measurements. Such a measurement gives a lot of detail like distortion, impulse response, wavelet spectrograms, etc, that you can't get from the moving microphone/RTA method. And, it calculates the filters needed for DSP adjustments automatically. I don't think REW can do that using the results of a moving mic/RTA measurement. (Can it?)
But if you try moving the mic during a REW frequency sweep test, you don't average the results, rather, you just get a result where the response at each frequency is from some random position, which is obviously not what you want.
So I think the averaging of multiple sweep measurements makes sense from the standpoint that you can (I think) average the results and let REW derive the dsp filters from the average. (Somebody correct me if I wrong, I don't have/use DSP myself).
Probably it would be good practice to follow up with a moving mic/RTA measurement to double check the frequency response after making any dsp corrections.
Eric
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That's always been my suspicion too. But just a suspicion, not proven for me yet.
Well, a DML would never reach full range by itself, even if you made the exciter yourself. Max it would reach is low-HF and high-LF, quite questionable with commercially available exciters currently. All commercial DML makers help their products with twitters and subwoofers. One maker claims that they had created a panel sub, though.
But, can you even go there with DAEX25CT 10W exciters?
And, it'll be a Study of DML as a Full Range Speaker for the elderly.
The panel is not the main problem here, but the exciter. That's why the commercial DML makers make pupose-built exciters for their products. Those exciters are not for sale to the general public.
AER also is a DML maker, claims their exciters reach 40-30000hz.
The AER bbx exciter just touches the panel only at one point.
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Yep... And tinnitus helps😁...oddly though, even though I'm HF compromised in frequency tests, I can hear the difference in music... I've read about this phenomenon before... It's something to do with harmonics
Eucy
Phew!
I was really only referring to Steve's drawing and assuming the mounting points were essentially rigid, or at least super damped..essentially infinite masses, and hence blocking panel movement at those locations, and therefore really not weighted points in terms of panel operation in the normal sense of the term.
Eucy
No. Most exciters start dropping like a rock below 100hz. This is why I recommend using a conventional cone powered subwoofer for frequencies below 100hz.
I’ve heard that too, but I doubt it. Harmonics go in the other direction. It takes non-linearity to introduce eg period doubling rather than frequency doubling, and that would probably not be a good thing. Sure it’s not marketing hype from supertweeter sellers?