I have never managed to get a plate to distort really, apart from if there are issues with mounting. I did manage to burn some exciters from overheating, but then distortion eventually happened as a consequence of mechanical damage to exciter or mounting. So I don't think the plates can distort really, at least it is not enough to use a cluster of the most powerful models.
I have not done any calibrated SPL tests yet, but have a basic SPL meter now to use as reference, as well as a scope, so will test sensitivity and max SPL soon!
I have done rough SPL calibration when doing my most recent tests with REW, and tried to play really loud then to pick up as much distortion as possible, but I'm limited by what measurement mic can handle, so end up measuring around 100dB at 30cm, and then have very minimal distortion.
My best guess based on the level I give them then, is that a single plate with 4 exciters at least can get close to 110dB.
I print small blocks using TPU, which is a flexible thermoplastic. I find that they need to be soft but most foam that is appropriate softness will degrade with time. TPU is much more stable, and when printing I can make it hollow to adjust how soft they are.
I have not done any calibrated SPL tests yet, but have a basic SPL meter now to use as reference, as well as a scope, so will test sensitivity and max SPL soon!
I have done rough SPL calibration when doing my most recent tests with REW, and tried to play really loud then to pick up as much distortion as possible, but I'm limited by what measurement mic can handle, so end up measuring around 100dB at 30cm, and then have very minimal distortion.
My best guess based on the level I give them then, is that a single plate with 4 exciters at least can get close to 110dB.
I print small blocks using TPU, which is a flexible thermoplastic. I find that they need to be soft but most foam that is appropriate softness will degrade with time. TPU is much more stable, and when printing I can make it hollow to adjust how soft they are.
Weather getting better here, gone from freezing and snow to +18c in a few days 
So planning to take a sub and a couple of plates outdoors and do some measurements. I finally have a scope, and since I now can measure AC voltage properly I was planning to measure response with calibrated sensitivity, but turns out that is not that easy with a class-d amp
There is a sine wave at 240kHz from the switching in the amp, and while it is quite many dB down from the max output of the amp, it is constant regardless of amp level, and with an overpowered amp like this the signal is still 1.33Vrms. So turns out I need a RF filter to be able to check the output voltage with decent accuracy.
Not sure I will bother making a filter since absolute sensitivity figures are not that important to me, and at least after a little testing, trying to ignore the FR component from the scope readings, my meter read 105dB at 2.83V into 4 ohm at 1kHz. That would mean sensitivity of 102dB with 1W/1m, so I'm at least confident sensitivity is very good. I can have misjudged the RF component a little bit, but should still be over 100dB. When doing outdoor test I will also test with higher voltage to reduce the error from RF signal.
So planning to take a sub and a couple of plates outdoors and do some measurements. I finally have a scope, and since I now can measure AC voltage properly I was planning to measure response with calibrated sensitivity, but turns out that is not that easy with a class-d amp
There is a sine wave at 240kHz from the switching in the amp, and while it is quite many dB down from the max output of the amp, it is constant regardless of amp level, and with an overpowered amp like this the signal is still 1.33Vrms. So turns out I need a RF filter to be able to check the output voltage with decent accuracy.
Not sure I will bother making a filter since absolute sensitivity figures are not that important to me, and at least after a little testing, trying to ignore the FR component from the scope readings, my meter read 105dB at 2.83V into 4 ohm at 1kHz. That would mean sensitivity of 102dB with 1W/1m, so I'm at least confident sensitivity is very good. I can have misjudged the RF component a little bit, but should still be over 100dB. When doing outdoor test I will also test with higher voltage to reduce the error from RF signal.
Hi Leob, glad it's warming up for you there, we are having a lovely Autumn on the other side of the world.
That's great your plates are so sensitive, so in theory you won't need a lot of watts for your output needs even at party levels.
Glad you can do some playing with your system now you have the subs to try it all together.
I have found your suspension method is great as it lets you tune the plates by moving and adding more clamping blocks in different places, I got rid of a broad 8db peak around 500hz by adding a third clamping point on one long side. I also had a 8db peak at 9000hz that I removed by adding a little felt infront of the exciter.
I sourced some 12mm epdm tape which I am using as blocks to clamp them with now instead of the closed cell foam. It holds better and I think I was getting distortion from the plate and foam rubbing/buzzing at higher SPL levels.
That's great your plates are so sensitive, so in theory you won't need a lot of watts for your output needs even at party levels.
Glad you can do some playing with your system now you have the subs to try it all together.
I have found your suspension method is great as it lets you tune the plates by moving and adding more clamping blocks in different places, I got rid of a broad 8db peak around 500hz by adding a third clamping point on one long side. I also had a 8db peak at 9000hz that I removed by adding a little felt infront of the exciter.
I sourced some 12mm epdm tape which I am using as blocks to clamp them with now instead of the closed cell foam. It holds better and I think I was getting distortion from the plate and foam rubbing/buzzing at higher SPL levels.
I await your report including video with great interestWeather getting better here, gone from freezing and snow to +18c in a few days
So planning to take a sub and a couple of plates outdoors and do some measurements. I finally have a scope, and since I now can measure AC voltage properly I was planning to measure response with calibrated sensitivity, but turns out that is not that easy with a class-d amp
There is a sine wave at 240kHz from the switching in the amp, and while it is quite many dB down from the max output of the amp, it is constant regardless of amp level, and with an overpowered amp like this the signal is still 1.33Vrms. So turns out I need a RF filter to be able to check the output voltage with decent accuracy.
Not sure I will bother making a filter since absolute sensitivity figures are not that important to me, and at least after a little testing, trying to ignore the FR component from the scope readings, my meter read 105dB at 2.83V into 4 ohm at 1kHz. That would mean sensitivity of 102dB with 1W/1m, so I'm at least confident sensitivity is very good. I can have misjudged the RF component a little bit, but should still be over 100dB. When doing outdoor test I will also test with higher voltage to reduce the error from RF signal.
Hey there, I was just wondering if you do the coating for durability reasons or sound reasons?! I didn't find any info about that... many thanks for all the interesting information!