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Old 4th February 2009, 09:09 AM   #111
APi is offline APi  Finland
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Join Date: Nov 2004
Location: Oulu
Quote:
Originally posted by Ziggy
If the material you have can be rolled, it's probably near on useless
Actually not.

I used self-made voice coil with the polypropylene foam sheet sized something like 150 x 10 cm. I had a voice coil glued on the 10cm end of this slice.

Actually got pretty nice sound when found the right curvature and how to attach the other end on something that minimize standing wave resonances on the foam. The sound was very airy, clean and even hights worked well.

But it´s very critical how you attach and curve the panel. You either get great sound, just resonances or pretty much nothing.
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Old 5th February 2009, 01:38 AM   #112
Ziggy is offline Ziggy  Australia
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APi, very interesting!.........what was driving the voice coil?......a magnet?
Can you please provide more detail as it is difficult to understand how this system operates.
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Old 5th February 2009, 02:31 AM   #113
Ziggy is offline Ziggy  Australia
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O.K...........here we go : HOW DOES MUSIC SOUND THROUGH THE PANELS?

Firstly, let me state that I have read all the reviews on the Podium loudspeakers, and my comments are NOT IN ANY WAY influenced or biased by them. This is my opinion only based on what I have heard and compared to the two way horns that I currently own and built myself some time ago.
All listening was done from FM radio transmissions and cd's that I own and am familiar with.
I will try to keep this as short as possible.

CLASSICAL/ORCHESTRAL MUSIC : very open, strings are realistic, sometimes so real sounding that cellos and double bases have a distinctive ''growl'' and rasp as the bow moves accross the strings. Minute details like shuffling, the conductor humming along with the music!!!!!, breathing of the players and many other micro dynamics are so startling that I had on occasions mistaken these as system problems before realising that they were noises on the recordings. The clash of cymbals at the back of the orchestra were sensational.

JAZZ : WOW!! have never heard a clarinet sound like a REAL CLARINET until now. Every whistle of air through actual wooden reeds was so obvious it was a sheer delight. The same for saxaphones and brass instruments.Cymbals here again were amazing!....like being there.Double bass, especially plucked sounded superb.

ACOUSTIC GUITAR : unbelievable!!!!.......the panels just love this type of music.

SOLO PIANO/PIANO : I am speechless........damn!........what have I been listening to all these years???? You can , in ''good'' recordings and boy, there are some BAD one's out there, clearly and easily distinguish the felt hammers smashing away at the strings on the body of the instrument. A run of notes from the bottom octaves to the top notes is a continuous crystaline progression of unmistakable ''piano'' notes. There is no point where the tonality changes due to differences in driver material or crossover points and their components. Remember, this is a 'GIANT FULL RANGE CROSSOVERLESS PANEL''.

VOICES : .........get my drift?


GENERAL COMMENTS : extremely revealing - especially in the midrange.
Hard to position?.........can't truly say. I hear a huge, wide, deep soundstage that fills the whole room. Will experiment with different positioning later. This is not important with this type of speaker from what I have experienced so far.
Is it's performance ''music dependant''?.........I say they are unforgiving and will slap you in the face with a mediocre/poor recording(some recording engineers should have been sacked for some of the stuff that I previously thought was ''reasonable''). A good recording will stun you in it's clarity, realism and involvement.
Transients - FAST, FAST, FAST

faster than a speeding bullet. Everything is tight and held together like concrete.
Bass : as mentioned before, your true ''boxless panel sound''here. When the bass is in the recording, you will know about it - at times I just shook my head in disbelief.
Is it perfect?.....no it's not. No speaker is but IMHO I think I have created something that I have been looking for in sound reproduction since I was in my teens!

It can get only get better from here as they reach completion and finishing off
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Old 5th February 2009, 04:09 AM   #114
APi is offline APi  Finland
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Quote:
Originally posted by Ziggy
what was driving the voice coil?......a magnet?
Can you please provide more detail as it is difficult to understand how this system operates.
Yep. I made an ad-hoc voice coil:


simply by twisting a bit less than 10 rounds of thin copper wire from a coil.
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Old 5th February 2009, 04:48 AM   #115
APi is offline APi  Finland
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Quote:
Originally posted by Ziggy
what was driving the voice coil?......a magnet?
Can you please provide more detail as it is difficult to understand how this system operates.
Yep. I made an ad-hoc voice coil:
- A bit less than 10 rounds. Can´t recall exact number.
- Different rounds of wire were twisted together as a thin cable.
- 1/3 of the round was glued on the 10cm end of the foam slice and a bit of duct tape was used to seal the package in case glue wasn´t strong enough.
- This 1/3 was close to bar magnets but not touching. I used refrigerator door as an base where to attach those!
- Magnetic flux was from the door into the foam so that force created moved the foam like speaker cone.
- 2/3 of the wires were not in the magnet field nor glued but just circulated the current back.
- Duct tape was also used to attach this 2/3 on the door and set gap between magnets and the coil.
- Since the foam was curved the result was a kind weird combination of different vibration modes and it took some time to make it sound pure without too much standing waves.

The other end of the foam was attached on a chair... Again by duct tape.

When curvature was close to 180 degrees this worked the best. Actually sound was far more realistic than with my right hifi speakers. Not that much bass but still enough for this kind of ad-hoc prototype. Frequency balance was almost the same in entire room and the best thing was sound didn´t come from a point source: sound was "airy" and very PLEASANT.

I have 1 meter long DIY ribbon. It produces incredible amount of details and I have used it as a kind of reference speaker. But I was very surprised how close this foam prototype managed to produce trebles. It didn´t ring if I could find the optimum setup and high frequencies were accurate without being localized which was very weird. I started to preferred this "airy and pleasant" sound over hifi speakers and the DIY ribbon. It shouldn´t work that well but did.

I did have some problems with foam resonances but what can you expect with this kind of prototype?

Twisted copper wire is not that flexible even if i did some zigzags and if you let too much low frequencies in the coil it just doesn´t move that free. Also tried some stuffing between the chair and the foam and it made a big difference.
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Old 5th February 2009, 07:54 PM   #116
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Ziggy what kind of amplifier are you driving them with? do they like tubes? how many watts required?

i think i'm joining the belivers here, gonna make the order for the soundpads one of thiese days. but i'm still puzzled about the name of the material here in italy.
one seller proposed me KAPAMOUNT, this is ligthweight 5mm material, looks like expanded foam beetween two plain sheets. really light and stiff. said it has the property of acoustic amplification. i don't think he really knew what it was trying to sell. have you ever heard of that?
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Old 5th February 2009, 07:59 PM   #117
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Ziggy,

Looks like you're making progress. I'm curious if you can give thoughts on the efficiency gained when you went from 1 to 6 exciters and also took them out of the plastic molding (which adds dead weight plus arms that damp out vibrations)

My biggest issue currently is the low efficiency combined with the poor power handling. With 1 exciter, I can barely get up to a decent volume that's on the quiet side without hitting the limits.

A nearby sign store supposedly sells gatorfoam. I'll have to check that out when I get a chance.

-Paul
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Old 5th February 2009, 10:55 PM   #118
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Ziggy, did you read this one also? http://jamnaudio.com/Reviews/podium1-6moonsprevp1.pdf

tells they are spreading frequencies in the model 1.

Ziggy? did you try some Bowie records on them?
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Old 5th February 2009, 11:44 PM   #119
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http://www.acp-composites.com/ACP-CAT.HTM

http://www.acp-composites.com/acp-lp.htm

carbon fiber laminates with foam/balsa/nomex honeycomb core

Very rigid and light weight.
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Note to myself: Never again use fingers to check if there still is voltage left in a capacitor...
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Old 6th February 2009, 04:30 AM   #120
Ziggy is offline Ziggy  Australia
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Hi Guys, will reply one by one......

APi : Great little invention. what you have is a distributed mode loudspeaker happening there. Work some more on it and report back.

human.bin : I'm using a high quality Pioneer receiver :VSXLX70 $3,000 AUS. I normally use my home built 845 SE valve amplifier, but it has been disassembled and ready for a new circuit configuration. I can't wait to hear these panels on a valve amplifier

I don't think the panels need too many watts, but the amplification must have good GAIN such as an active preamp and decent output from the source.

KAPABOARD is made by the same people who make GATORFOAM - ALCAN COMPOSITES.There are a few varieties of this board but ......YES !!!........this material will be O.K to use. Try to use the lightest and stiffest board in the range.

Yes, I have also read that review too.

bpilgrim99 : one exciter on a huge sheet of Gatorfoam was surprisingly loud, but, only when it was removed from it's casing(big difference in highs and loudness). However, it was not loud enough for any reasonable levels .

When a total of six are used, there is a marked increase in output - generally, according to the internet articles I have read, about 3db per extra driver added. However, this can vary depending on how they are wired and we are not talking about direct radiators here - we are talking about EXCITERS where the rules may not apply in the same way??.

I would guess that I have an estimated 10db increase (from 76db for one driver to 86db for 6 - but, it sounds VERY MUCH LOUDER than this. Why?.......because the sound drop off with distance does not affect these panels like direct firing loudspeakers. They actually sound louder as you move further away ).

BUT, STUPID ME! : I have discovered that I have wired my drivers incorrectly

Instead of wiring the 6 as two pairs of three then paralell or series these to get either 5.4 ohms or 12 ohms impedance, I wired 5 in paralell, then the lst exciter in series!!....what was I thinking?
This caused the exciter in series to get hot, put out more volume than the rest(which ran cool).

So, I will rewire this weekend - CORRECTLY!.......for 12ohms, as 5.4 is too low for my amplifier.

This will THEN give me a true indication of sensitivity increase.

''Spreading frequencies''.......he's using a crossover....... I'm avoiding this completely

Peter M. : thanks for the link.............a sample to try would be nice?? A bit expensive otherwise
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