Ziggy said:
Since I didn`t have piezos I tried with traditional voice coil if flexible foam (closed cell polystyrene) can be used. And it looks like the answer is yes: Material can also be flexible and a bit soft without loosing high frequency response.
I wish someone could try this also with piezos
The other thing why I did the experiment with a foam slice was to test if distributed mode loudspeaker can be less distributed:
You move just one end of the foam like line source and the foam act as a kind of one dimensional transmission line: Soft foam absorbs high frequencies before they reflect from the other end and mid frequencies can be matched by selecting right curvature and damping material at the points of attach. But even if material absorbs something it still makes some sound.
Changed the speaker impedance setting on my amplifier to 6 ohms (didn't realise it had that option), so I wired up the panels for 5.4 ohms total impedance. A multimeter reading shows each panel at a DCR of 4.4 ohms, so I would presume that this is pretty close to 6 ohms as required.
RESULTS ON SOUND QUALITY? : after some sound pressure level readings compared directly to my two way horn system that are 103 db, I have approximately (this is with simple equipment and judgment by ear) 92db efficiency from the panels. Not bad at all.
The output is naturally much louder than my wiring mistake disaster previously.
Bass output has entered a new level - even deeper, richer and makes the overall sound fuller than they were (and that was fine already!).
So, I guess that's it. I have succeeded . The horns will be sold off from here on.
Basic summary of this whole experience and my recommendations and advice :
Don't disregard the NXT technology.........you will be very foolish to do so.
You MUST have a VERY LARGE suitable material as panels to obtain impressive bass, mids and highs.This is CRITICAL!
You MUST have multiple exciters(vertically and evenly spaced) to drive this size of panel and obtain the efficiency and reasonable power handling.
You MUST remove the exciters from their casings if you buy the ''Soundpads'' as your source for the exciters.
You MUST use the correct double sided adhesive tape to secure the exciter to your panel : 3M Adhesive Transfer Tape F9473PC.
RESULTS ON SOUND QUALITY? : after some sound pressure level readings compared directly to my two way horn system that are 103 db, I have approximately (this is with simple equipment and judgment by ear) 92db efficiency from the panels. Not bad at all.
The output is naturally much louder than my wiring mistake disaster previously.
Bass output has entered a new level - even deeper, richer and makes the overall sound fuller than they were (and that was fine already!).
So, I guess that's it. I have succeeded
. The horns will be sold off from here on.Basic summary of this whole experience and my recommendations and advice :
Don't disregard the NXT technology.........you will be very foolish to do so.
You MUST have a VERY LARGE suitable material as panels to obtain impressive bass, mids and highs.This is CRITICAL!
You MUST have multiple exciters(vertically and evenly spaced) to drive this size of panel and obtain the efficiency and reasonable power handling.
You MUST remove the exciters from their casings if you buy the ''Soundpads'' as your source for the exciters.
You MUST use the correct double sided adhesive tape to secure the exciter to your panel : 3M Adhesive Transfer Tape F9473PC.
Attachments
Ziggy,
Some problems I see.....
The exciters act much like a traditional point source at high frequencies. Since you have basically created a line source, the large spacing between the exciters is sure to create some combing effect.
You should really attach the back of the exciters to a solid object. This will help greatly in the lower frequencies. Not only will it help limit over-excursion, but it will also turn the panel into a more traditional linear driver at lower frequencies.
The plastic housing of the soundpads act as a mechanical high pass filter to limit low frequency excursion.
Some problems I see.....
The exciters act much like a traditional point source at high frequencies. Since you have basically created a line source, the large spacing between the exciters is sure to create some combing effect.
You should really attach the back of the exciters to a solid object. This will help greatly in the lower frequencies. Not only will it help limit over-excursion, but it will also turn the panel into a more traditional linear driver at lower frequencies.
The plastic housing of the soundpads act as a mechanical high pass filter to limit low frequency excursion.
theAnonymous1, yes, you are quite right and the rear brace will be used in the final assembly/frame.
Ran some test frequencies last night from 20hz - 20k and observed levels and panel behaviour.
Here are my findings :
The response at the low end of the scale before ''grounding the exciters'' as theAnonymous1 has stated, is approximately 3db down at 40hz. At the top end, I can hear the 16k cut off and then nothing at 20k (not bad for 52 years of age, eh?).
At 50hz, there is a strong vibrational rattle which I initially thought was an exciter problem or wire touching the panel. It's actually the panel itself and will cease rattling the moment both sides are gripped lightly with my fingers, or touched at the back near the middle exciter. Interesingly, I only notice this on one panel and not the other.
Then again, the two panels do not have their exciters mounted in exactly the same positions - quite the opposite in fact - they were just placed anywhere that looked like a straight line and roughly spaced away from each other as a quick test and have remained there since.
I would presume that this resonance is pretty close to the panel's actual resonant frequency at this point in time, and I expect it to shift or hopefully be a non issue once everything is mounted and suspended in a frame with rear bracing against the exciters.
I have received the adhesive mounting rings from NXT yesterday, so it's all accurate measuring and positioning from here on in.
Once again, the speed of drum rim shots, trumpet/brass blasts are so intense and dynamic, it's hard to believe that this level of performance is possible from NXT technology.
I only hope that nothing is lost in the sound quality department in the final steps of finishing off the panels.
Ran some test frequencies last night from 20hz - 20k and observed levels and panel behaviour.
Here are my findings :
The response at the low end of the scale before ''grounding the exciters'' as theAnonymous1 has stated, is approximately 3db down at 40hz. At the top end, I can hear the 16k cut off and then nothing at 20k (not bad for 52 years of age, eh?).
At 50hz, there is a strong vibrational rattle which I initially thought was an exciter problem or wire touching the panel. It's actually the panel itself and will cease rattling the moment both sides are gripped lightly with my fingers, or touched at the back near the middle exciter. Interesingly, I only notice this on one panel and not the other.
Then again, the two panels do not have their exciters mounted in exactly the same positions - quite the opposite in fact - they were just placed anywhere that looked like a straight line and roughly spaced away from each other as a quick test and have remained there since.
I would presume that this resonance is pretty close to the panel's actual resonant frequency at this point in time, and I expect it to shift or hopefully be a non issue once everything is mounted and suspended in a frame with rear bracing against the exciters.
I have received the adhesive mounting rings from NXT yesterday, so it's all accurate measuring and positioning from here on in.
Once again, the speed of drum rim shots, trumpet/brass blasts are so intense and dynamic, it's hard to believe that this level of performance is possible from NXT technology.
I only hope that nothing is lost in the sound quality department in the final steps of finishing off the panels.
This project sounds interesting!
I don't think I have room for them, but the concept is fascinating.
They are fairly directional I assume?
Has anyone thought of a long, thin strip to make something more like a line array? That would lose the directionality without the 'combing' as I understand it.
For the high end, what about a silk dome tweeter crossed over to handle the highs? Or am I understanding the issue?
== John ==
I don't think I have room for them, but the concept is fascinating.
They are fairly directional I assume?
Has anyone thought of a long, thin strip to make something more like a line array? That would lose the directionality without the 'combing' as I understand it.
For the high end, what about a silk dome tweeter crossed over to handle the highs? Or am I understanding the issue?
== John ==
jqwinner, they are definately NOT directional. They are diffuse bipolar radiators that can still produce a stunning stereo sound field.
Believe me, I have found no desire for any extra supplement to the highs - there are plenty of them and a dome tweeter or any tweeter for that fact would be pointless.
Can't say that combing is audible but may be there just the same.
Believe me, I have found no desire for any extra supplement to the highs - there are plenty of them and a dome tweeter or any tweeter for that fact would be pointless.
Can't say that combing is audible but may be there just the same.
ziggy,
I don't want to thread-jack, but I have a quick question for you about gatorboard. Do you think it would be suitable as speaker enclosure material? I am attempting a mobile project which needs to remain extremely light, and I'm unsure if gatorboard would resonate poorly or would be too flimsy. Any idea on this?
Thanks!
I don't want to thread-jack, but I have a quick question for you about gatorboard. Do you think it would be suitable as speaker enclosure material? I am attempting a mobile project which needs to remain extremely light, and I'm unsure if gatorboard would resonate poorly or would be too flimsy. Any idea on this?
Thanks!
John,.......or should I call you ''John''.......you need to read up on the operating principle of Distributed Mode Loudspeakers to understand that this is not just your usual ''panel'' loudspeaker.
Yes, you can hear that sound is coming from them, but not in the same way as a Maggie or Electrostatic, Ribbon.
This is NXT technology and has to be carefully implemented to get anything decent out of it due to it's unique operation. There is a lot to it as you will find during the course of this thread(that's if you have read it all?)
Your comment ''my use would be for a home theater'' is a typical attitude that has been adopted by those that have not heard the technology operating past the point of simple cheap ''home theater'' set ups in your local electronics dealer.
Go and hear the Podium Loudspeakers or better still, read the reviews. Google ''PODIUM LOUDSPEAKER REVIEW'' and then tell me that they are for ''home theater''
On the possible ''combing effect'' mentioned, can this still apply to a DML?. How has Podium Loudspeakers avoided this? There is no mention of it in any of Shelley Katz's interviews or the technology in his design.
Yes, you can hear that sound is coming from them, but not in the same way as a Maggie or Electrostatic, Ribbon.
This is NXT technology and has to be carefully implemented to get anything decent out of it due to it's unique operation. There is a lot to it as you will find during the course of this thread(that's if you have read it all?)
Your comment ''my use would be for a home theater'' is a typical attitude that has been adopted by those that have not heard the technology operating past the point of simple cheap ''home theater'' set ups in your local electronics dealer.
Go and hear the Podium Loudspeakers or better still, read the reviews. Google ''PODIUM LOUDSPEAKER REVIEW'' and then tell me that they are for ''home theater''
On the possible ''combing effect'' mentioned, can this still apply to a DML?. How has Podium Loudspeakers avoided this? There is no mention of it in any of Shelley Katz's interviews or the technology in his design.
aphelion said:
In Germany many build so-called resonating enclosures, especially in combination with "historic" drivers. This is the archaetype of this speaker family:
http://www.auditorium-23.de/Speakers/Rondo.html
The side walls are 4mm (fir, I think). They are not heat-bent, but are on tension.
Ziggy don't know if it can help, but once i read a discussion about how a piano let's the sound out. it come out that if you aproximate mathematically quite all the waves from the resonating boards should null each other into the room. but then this simply doesn't happen cause they come out at different speed from different point from the entire surface of the piano wich is in an even position in a complex room and so on... don't know if it make sense, don't know if it's true at any...
i thought the panels to be dipolar, so they are firing front and back and not omnidirectional. but still with don't know what's the hotspot is like, can you tell us?
i thought the panels to be dipolar, so they are firing front and back and not omnidirectional. but still with don't know what's the hotspot is like, can you tell us?
el'OL, I guess that you can make a speaker box out of anything, but, with Gatorfoam, cabinet resonance will be a problem in larger sizes for sure. In a small bookshelf speaker, it could be o.k and can possibly even enhance bass quality.
I remember GALE SPEAKERS made a small cheap bookshelf speaker many years ago that actually worked better with thin particle board walls! Heavier/thicker and more dead sounding wood , sounded TERRIBLE with these drivers. !!!!!!!
human.bin, the sound of a piano is what made the designer of the PODIUM SPEAKERS work with NXT exciters and panels, so who knows?
Your question on ''sweet spot''........there isn't one. You can move across from one side of the room to the other(7 meters in my case) and still have a stereo image in front of you. Even when you stand directly between the panels .........STRANGE:
I remember GALE SPEAKERS made a small cheap bookshelf speaker many years ago that actually worked better with thin particle board walls! Heavier/thicker and more dead sounding wood , sounded TERRIBLE with these drivers.
!!!!!!!human.bin, the sound of a piano is what made the designer of the PODIUM SPEAKERS work with NXT exciters and panels, so who knows?
Your question on ''sweet spot''........there isn't one. You can move across from one side of the room to the other(7 meters in my case) and still have a stereo image in front of you. Even when you stand directly between the panels
.........STRANGE:Ziggy said:
I once visited someone who had built such resonating enclosures. Knocking on the side walls this thing resonated even more than the Podium Sound panel. Non-resonating this kind of enclosure would be a short TL that doesn´t go below 80Hz. These lower frequencies are produced by the resonances of the side walls.
That's right : resonance can be used to an advantage in some systems.
Here though, are speakers that are ''stepping out on a limb'' so to speak - they are not with the purist loudspeaker maker
I once read an article(think it was an old copy of stereophile - reader's comments) on a guy who was so hooked on horn loudspeakers, he insisted that even the poor people with no woodwork skills use CARDBOARD,FOAM, DRYWALL and ANYTHING they could lay their hands on to build large bass horns despite wall resonance!!which he deemed ''not an issue'' !!.
All this just so they could experience the benefits of horn loading
:
Here though, are speakers that are ''stepping out on a limb'' so to speak - they are not with the purist loudspeaker maker
I once read an article(think it was an old copy of stereophile - reader's comments) on a guy who was so hooked on horn loudspeakers, he insisted that even the poor people with no woodwork skills use CARDBOARD,FOAM, DRYWALL and ANYTHING they could lay their hands on to build large bass horns despite wall resonance!!which he deemed ''not an issue'' !!.
All this just so they could experience the benefits of horn loading
:UPDATE : more email correspondence with NXT :
Forget the honeycomb stuff - $2,000AUS. each!!
RIDICULOUS ????????
NXT definately recommends grounding the exciters for a'' more durable system''. So, the back spine will hold the exciters up against the rear panel with silicone rubber acting as a form of ''compliance''
Forget the honeycomb stuff - $2,000AUS. each!!
RIDICULOUS ????????NXT definately recommends grounding the exciters for a'' more durable system''. So, the back spine will hold the exciters up against the rear panel with silicone rubber acting as a form of ''compliance''
Here's an example of bass response : last night I was listening to a live broadcast from the Sydney Myer Music Bowl - 50th anniversary(delayed in Perth, West Australia).
The presenters were on stage outside for some time before the concert was to start.
I could occasionally hear a distant? rumbling thunder like sound which I could not localise around my area or outside the house.
I eventually came back inside and sat down to listen and finally realised that it was coming from the transmission. What was it?......aircraft, trains, thunder?
It turned out to be WIND NOISE sweeping accross the presenter's microphone!!!.......very low frequency, but obvious.
Man, I have never heard anything like that come through so clearly and distinctly. Now that's bandwidth towards the low end
The presenters were on stage outside for some time before the concert was to start.
I could occasionally hear a distant? rumbling thunder like sound which I could not localise around my area or outside the house.
I eventually came back inside and sat down to listen and finally realised that it was coming from the transmission. What was it?......aircraft, trains, thunder?
It turned out to be WIND NOISE sweeping accross the presenter's microphone!!!.......very low frequency, but obvious.
Man, I have never heard anything like that come through so clearly and distinctly. Now that's bandwidth towards the low end
Am noticing a gradual but noticeable break -in of the exciters as the sound has smoothed out, become more revealing in the midrange, more air and atmosphere.
I thought that ''break-in'' was a load of bull but I now think otherwise from what I am hearing. I have only been playing the panels at moderate levels but on a daily basis of 2-3 hours each evening.
The panels are not yet in their frames as I am sourcing a ''sane'' price for Australian Oak
Hope to have something purchased by early next month at the latest.
Still being totally gobsmacked with the sound.........really amazing, true to to the real sound of music.
I thought that ''break-in'' was a load of bull but I now think otherwise from what I am hearing. I have only been playing the panels at moderate levels but on a daily basis of 2-3 hours each evening.
The panels are not yet in their frames as I am sourcing a ''sane'' price for Australian Oak
Hope to have something purchased by early next month at the latest.
Still being totally gobsmacked with the sound.........really amazing, true to to the real sound of music.
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