Leob,
I have generally only tried single and paired (series) combinations of exciters. Based on that experience, I would not expect more exciters, or "higher power" exciters to be louder than a single exciter, at the same volume setting on your amp. Or even that more exciters would lead to lower harmonic distortion at a given volume. Possibly, at high volumes, more exciters should be able to handle the same spl without overheating. But I find that harmonic distortion increases before overheating becomes an issue. Personally, the only reason I can so far justify two exciters on the same panel is to get the impedance up to 8 ohms.
Eric
Sebastian,
All I can say is "wow"! You are so much more optimistic than I am! My approach is to start with the most simple, and add features to fix any problems. Your approach was to combine everything you read or could think of, and see what you get! For me, the difficulty is that your construction is far too complex for me to assess, as it has far more features than I can begin to comprehend.
Regarding multiple exciters, what I can say is this: if multiple exciters are placed far apart, the impulse response will be worse (slower decay) than a single exciter. But the opposite can be true if the exciters are placed close enough together, in the right place, on the right panels.
My suggestion to you would be to try more simple designs first. Then see if modifications improve it. Otherwise it's hard to tell what's doing what.
Eric
Yes, multiexciter design is the possibility to handle more power and for that more volts are needed and in consequence the membrane displacement will increase leading to a higher distortion. There is almost nothing in this thread about the behavior of the materials used according to the sound pressure. The contamination test at different SPL might be a possibility but need a specific environment (no neighbors) and ear protections!
As I use for now tweaked cheap class D amp, 4 ohm load is not in my concerns. I haven't thought of 2 exciters because of the impedance. The question how they combine comes before the need to reach 8 Oms.
Eric,
Your words are better than mine! If it is a first shot, there is a complexity that will be very difficult to manage.
A chance with DML is that almost everything good or bad happens at the membrane so at the origin of the signal. I mean it is very different than with pistonic loudspeakers where the recombination of the different paths matter plus the reflexion on the boundaries.
I think, even if i haven't experienced it, this is a possibility for EQ.
Where EQ won't correct the system is where a complete frequency is missing in the dips.
Christian
What I want to find out is how much SPL I can get from a single plate, with no limitation to the amount of amp power used. I'm not hoping to improve efficiency nor reduce distortion.
But of course, the more powerful system the less likely it will be that I will push it to distort/overheat.
Question is how much the plates can handle. Tectonic seems to use 4x75w per plate, but I have a feeling that EPS will not be able to handle that much power.
My proposal of test would be :
Make a panel of the dimension you target.
Find some SPL meter (phone application, dedicated one, USB mic calibration...)
Decide the total harmonic distortion you accept (10%?). Remark : harmonic distortion might be mainly 2nd order which is perhaps more acceptable... an other property of DML?
Decide the high pass filter you intend to have (displacement is linked to the frequency) and implement it
Then make FR with REW increasing the volume up to the distortion. A limitation in the sweep is needed not send high power in high frequency.
Protect yourself and your environment!
This is more a kind of brain storming... simplification or other way might be possible.
Leob.
Eps is the most efficient material I have found , which produces vastly superior low level detail than any other panel material I have tried.
My ten watt exciter will drive a 6ft or 1ft panel to ear bleeding levels, far louder than any in home systems costing vast amounts of money.
I would never be able to turn my volume control anywhere near the half way point without suffering hearing loss.
And this is from a ten watt digital amp.
With eps and other plastic materials, you have to be very careful that the coils do not heat up too much and melt the panel (I was not in the room at the time this happened ! )
I suppose I treat my panels as I would a horn mid tweeter ,vast amounts of power are not needed.
But if you are using heavy inefficient panel materials, then obviously this is a problem.
I'm sure there is a compromise somewhere between robustness and sound quality for outdoor use like the tectonic panels.
Steve.
Eps is the most efficient material I have found , which produces vastly superior low level detail than any other panel material I have tried.
My ten watt exciter will drive a 6ft or 1ft panel to ear bleeding levels, far louder than any in home systems costing vast amounts of money.
I would never be able to turn my volume control anywhere near the half way point without suffering hearing loss.
And this is from a ten watt digital amp.
With eps and other plastic materials, you have to be very careful that the coils do not heat up too much and melt the panel (I was not in the room at the time this happened ! )
I suppose I treat my panels as I would a horn mid tweeter ,vast amounts of power are not needed.
But if you are using heavy inefficient panel materials, then obviously this is a problem.
I'm sure there is a compromise somewhere between robustness and sound quality for outdoor use like the tectonic panels.
Steve.
Christian.
I'm not sure if you managed to listen to the last zip recording.
But I've noticed some problems with the recording itself.
I think it is a combination of the junk in the room , the fact that the low frequency drivers are too loud ,and that I think there is an automatic voice control AVC operating which is softening the sound ?
But at least I have shown that it is still possible to record our panels ,to demonstrate how they perform.
When I finally get my new phone ,I will sort out better apps for recording.
This recording was done on my wife's phone using a Samsung voice recorder which I found already installed on her phone.
Steve.
I'm not sure if you managed to listen to the last zip recording.
But I've noticed some problems with the recording itself.
I think it is a combination of the junk in the room , the fact that the low frequency drivers are too loud ,and that I think there is an automatic voice control AVC operating which is softening the sound ?
But at least I have shown that it is still possible to record our panels ,to demonstrate how they perform.
When I finally get my new phone ,I will sort out better apps for recording.
This recording was done on my wife's phone using a Samsung voice recorder which I found already installed on her phone.
Steve.
That is pretty much the plan, but of course a lot of considerations in what to test when it comes to plates, exciters, mounting, etc. Like I said initially, it might take me a couple of years to complete this project when dabbling with it in my spare time.
Phones cannot measure high SPL at all, and when it comes to PA levels, my USB measuring mic will be probably be insufficient as well. But I don't really need to be super accurate in measuring performance all the way to the top SPL. If I measure within the limits of my setup I hope that will give me enough information to interpolate and listen for the top range of SPL.
I think we have a little bit different references when it comes to what is loud
Unless you somehow get over 100dB sensitivity, 10w will certainly not be very loud for me, even in a small room. I have mistreated my ears enough through the years, so already had that hearing loss I guess
With the 50w exciters I can push the EPS so loud that it is unbearable even for me. But that is standing right in front of the speaker in a small room. I really wouldn't want to be in that room with a 2000w line array speaker though.
It does seem a bit unexplored how much power EPS can handle. With carbon sandwich we know that they can handle a lot of power as well as having similar sensitivity to EPS.
I have seen some running multiple exciters successfully on hard to drive materials like acrylic, but since you don't need many watts to make EPS loud, I guess for most applications the question if the EPS plate can handle 300w of exciters are not that relevant.
Hello Steve.
Not yet listen. By the end of the afternoon probably. About recorder on phones : I thought 2 years ago to use them to record some sweeps and them get the FR by post treatment. Unfortunately some apps use filters for a better record of voice. Not always possible to disable it. You should probably make a test with a pink noise to see if there is such filter. It is why I moved to hand recorder. There is also an app (some euros to pay) that is dedicated to audio measurements and I think record.
Christian
Steve
Everything fine for me in this way to post records. Unzip it and then play with audacity. No problem.
I don't have experience in such records.
A bit too warm I agree.
I was wondering if there is a kind of room signature in the bass and ambiance that the record emphasizes.
Seeing the tracks under audacity, one channel seems having a little attenuation.
May I suggest you to post for the next one in addition some information about the conditions : which panel, sub on...
Christian
@HCSebastian @Veleric @spedge @Leob
Please find below the FR of 2 quick basic tests.
First is a 3.9Ohm resistor in serie with the exciter : a little bit less than 3dB lost over the complete frequency range (green is without resistor, red is with resistance). The 2 FR are not from the same days (but same panel XPS 9mm 20x30cm I use currently for testing) so slight differences might come from panel or microphone placement.
Second is 2 exciters on this panel. The second exciter was added as close as possible from the first one (which is at 2/5 position) on the diagonal. Nothing highly scientific... (green as above, blue 2 exciters). The changes are not so big. At least there is no big change in HF. The difference @20k is not relevant as it is also in the FR with the resistor added.
Eric, you might be right! The FR with 2 exciters is even smoother in a certain way. DML are full of surprises!
To keep in mind : the exciters are close of each others.
Sebastian, there is no inconvenience appearing with those basic tests in what you want to do. The points remaining "out the of the main path" in your design are the impact of the braces and the polyurethane. Keep us inform on those points.
About the electrical arrangement, why not to start with the one the most suitable for your amplifier (tube?)? But it is perhaps not a criteria.
Christian
Please find below the FR of 2 quick basic tests.
First is a 3.9Ohm resistor in serie with the exciter : a little bit less than 3dB lost over the complete frequency range (green is without resistor, red is with resistance). The 2 FR are not from the same days (but same panel XPS 9mm 20x30cm I use currently for testing) so slight differences might come from panel or microphone placement.
Second is 2 exciters on this panel. The second exciter was added as close as possible from the first one (which is at 2/5 position) on the diagonal. Nothing highly scientific... (green as above, blue 2 exciters). The changes are not so big. At least there is no big change in HF. The difference @20k is not relevant as it is also in the FR with the resistor added.
Eric, you might be right! The FR with 2 exciters is even smoother in a certain way. DML are full of surprises!
To keep in mind : the exciters are close of each others.
Sebastian, there is no inconvenience appearing with those basic tests in what you want to do. The points remaining "out the of the main path" in your design are the impact of the braces and the polyurethane. Keep us inform on those points.
About the electrical arrangement, why not to start with the one the most suitable for your amplifier (tube?)? But it is perhaps not a criteria.
Christian
Came across mention of using Zobel networks to neutralize inductance of a voice coil. Anyone has thoughts about using that with the larger exciters to get better HF response?
Can it really be so simple that I just need to add a capacitor and a resistor to the exciters to make them good for full range?
Can it really be so simple that I just need to add a capacitor and a resistor to the exciters to make them good for full range?
What do you expect to happen when the power is too much for the plates? Just curious.
Eric
Christian.
my good recording apps without AVC were on my broken phone,I was just testing to see if it up loaded ok.
it is not easy to record speakers in an ordinary room.
normally I would have to make a recording then listen to it on my headphones to see how it sounded and then adjust the position of the microphone until I get the sound right ,this could take a few recordings.
I would also have to adjust the sub as well.
It is a compromise of getting as little of the room sound as possible, but not getting too close to the speakers.
If you get too close you tend to loose the ambience, and it starts to sound a little closed in.
If you set up the sound to what you think is good by ear before recording , I found that the microphone picks up strange sounds that our brains seem to ignore ?
When I first started recording my panels I'd make the recording thinking they sounded great, but when I played It back It sounded like I recorded It in the bathroom !!
It makes you understand why they have recording studios.
I new the sound was not right with the last zip recording ,but that is all I have at the moment, until I get a new phone,
I only hope it sounds as good as my old galaxy note 4 ?
Steve.
Ps.
You are correct about the channel volume levels, I noticed this on my old phone as well.
It might be a phone thing ?
my good recording apps without AVC were on my broken phone,I was just testing to see if it up loaded ok.
it is not easy to record speakers in an ordinary room.
normally I would have to make a recording then listen to it on my headphones to see how it sounded and then adjust the position of the microphone until I get the sound right ,this could take a few recordings.
I would also have to adjust the sub as well.
It is a compromise of getting as little of the room sound as possible, but not getting too close to the speakers.
If you get too close you tend to loose the ambience, and it starts to sound a little closed in.
If you set up the sound to what you think is good by ear before recording , I found that the microphone picks up strange sounds that our brains seem to ignore ?
When I first started recording my panels I'd make the recording thinking they sounded great, but when I played It back It sounded like I recorded It in the bathroom !!
It makes you understand why they have recording studios.
I new the sound was not right with the last zip recording ,but that is all I have at the moment, until I get a new phone,
I only hope it sounds as good as my old galaxy note 4 ?
Steve.
Ps.
You are correct about the channel volume levels, I noticed this on my old phone as well.
It might be a phone thing ?
Distortion....I think it takes more than a couple of hundred watt to make anything more spectacular than that happen
However I just realized I have not yet tried using two 50w exciters on one EPS panel. With a single exciter I have to turn the amp up over 70% to start noticing distortion...at which level the amp of course is expected to start distorting as well. But with both exciters on one panel I should be able to get similar wattage as 4x DAEX25FHE-4.