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Gentlemen, I think I have it!!!!!!!!!!!!! As we have struggled to better the Gatorfoam, I had an idea which goes way back to the roots of this NXT panel saga.[/b]We're champing at the bit!!!!!Jack
el'OL..................................... ...correct!The piezo, as I have found, matches the output of the panel's sensitivity perfectly and blends in better than I could have dreamed for I was expecting to have to use resistors, capacitors and or step up transformers, but by sheer luck NONE of this is required.Having designed ESL's for many years, I have some reservations about the capacitive load of a piezo element. It's a high impedance device and as such acts as it's own crossover. By this I mean that it's a better impedance match at high frequencies than lower frequencies. The driving amplifier is going to "see" more capacity at higher frequencies and be more reactive. Some amplifiers can be unstable and oscillate under capacitive reactance.In real world applications ESL's can be 4 or 5 mfd, If possible, measure the piezo load just to see what you have. It's probably nothing to cause concern, just something to keep in mind.Otherwise, congratulations!!!Jack
Measured the piezo : 0.025uf.Don't think that this should be a problem?
j gale..............that is the million dollar question! I feel that I may have fallen in to the brighter is better (as opposed to accurate) trap? One thing that concerns me.If a one wishes to look at this project from a "purist" standpoint, there would be a problem of aesthetics.I know for a fact that the magneto dynamic exciters are capable of upper end frequencies beyond 20,000 hertz. The problem, (as it has been all along) is one of coupling the exciter to the outside world, so to speak. Like it or not, "Nomex" has been the material of choice thus far. It's very low mass and quite rigid. If one looks at the construction of this product, it's elegantly simple but not easily copied by the average person. I must admit, I've laid in bed at night thinking of a way to make my own version of NomexShelley Katz still had to do a bit of a balancing act with the Podium 1, by adding an hp capacitor in one or two exciters despite the Nomex. All in all, I think Shelley has been very good about revealing as much as he has. The Podium point 5 uses no other passive components to my knowledge, if so I stand corrected.Hey, I have a piezo horn laying around here someplace. I still may give it a shot anyway. As a horn tweeter, it totally sucks. One other thing, it may be rated for no more than 20 watts, I can't remember.Jack
However, this time the cone will be taped to the back of the panel, more towards the edge, rather than the middle with the rest of the exciters.
I know that over the ''other forum'' they were promoting the rounding of corners.Are you aware of improved results with this technique?I say this beacause those guys over there have ''lost the plot''...........big time.I haven't been checking the "other" forum with any regularity, my thoughts are that they're stuck in a rut.I can't say with any real evidence that rounding the corners will improve performance without actually trying it. From a physics standpoint I believe rounding the corners may have audible benefits.The epicenter of the bending waves emanating from the exciter are concentric until they hit the edge of the board. The waves grow in amplitude as they travel away from the epicenter. (Bigger board, more bass).Here's what I think may be happening. The waves hit the edge of the board and have nowhere else to go but bounce back in the opposite direction.Thus a need for dampening. I don't think it's such a big deal on long edges, but when the waves hit a corner there must be a great deal of turbulent reflections running into each other at 90 degree angles. After all, the board is getting smaller as the waves get closer to the corner.Have you noticed the increase of vibrations at the corners? These may not necessarily be "good vibrations". (Apologies to The Beach Boys).It stands to reason that the concentric waves will behave in a more predictable manner when running into a curved edge. A gentler cross wave reflection should result. Some might be thinking of using a round board instead of rectangular, but I don't think it's an efficient idea.The reason being that we are using in line multiple exciters and it would just take up too much real estate on the board. No sense in wasting radiation area and losing out on bass. No need to go elliptical either for the same reason.I'm going to do a caveman test on a board, by sprinkling salt on a horizontal board with one exciter. I'll then sweep an audio signal generator and note results. Then repeat the test with a rounded corner board.BTW.... You could be right about the tape. It could come in handy to be able to walk into a store and buy a roll.Jack
I find it frustrating yet humorous that the people who have disregarded, slagged and brushed off this DIY success story without even giving it a decent go or try and have relied on measurements and the negative attitudes of others and other forums to convince themselves that this is just a load of B.S.!!
