[zygadr]

Hi doug s.
I'm not certain that the fs in the exciter world applies in the same way as a normal dynamic driver with a basket and cone. I could be wrong, but from experience the exciters I am currently using are from the frog shaped SpoundPax units which have an fs of 370hz. Yet, when placed on a panel,the bass response is much lower........going down to what seems like 50hz and that's only using two exciters.
The two high power high shove exciters that I linked a while back still have a specified frequency range from 100hz - 15kz/20khz (as do most of the others).
It all depends on what the panel material is constructed from I believe. Using 4mm marine ply with the standard exciters gives good low bass. Change to VHEPS and the bass is weak

As far as using multiple low power exciters, I can only say .........been there - done that. It is power handling and high shove, high BL that I think is the way to go. I recall having 6 standard exciters on Gatorfoam and still had problems with overheating exciters as they are only good for 5-10 watts. Even 6 wired together didn't really give any significant advantage when playing music loud (especially violent percussion).

So, I guess the only way to find out is to try the high power versions to see if bass is compromised?

[doug s.]

zygadr, you could be right - i have no experience; i am merely speculating.  but hi-power or not, if/when i ever do a panel speaker w/exciters, there will be at least 4 per panel...

doug s.

[zygadr]

Agreed doug. I allways had in mind 4 high power exciters per panel. One exciter will not do the job if we are to improve on past panel/exciter systems.

[j gale]

Just noticed that the HIAX25C10-8/HS has BL or force factor of 4.4 vs only 3.5 for the last 32mm unit linked to. HIAX25C10- HS looking better and better.

[zygadr]

Yes j gale it is a good contender!

However look at the specification sheet for the HIAX32C2O8:

http://www.parts-express.com/pedocs/specs/297-2114-hiwave-hiax32c20-8-specifications.pdf

Plus, it is ''self supporting''(no need for spine or reinforcement to avoid voice coil droop), 30W max power handling(on the HiWave website it shows as 20W - 40W !!!) and a 32mm voice coil.

It's BL  is 7.8    !!!!!!!

We can't forget that the above exciter is designed for industrial/commercial audio and to drive ''high impedance'', rigid substrates.
4mm plywood IS a ''high impedance substrate'' compared to cardboard or EPS.

Have a look  at the now not available exciter that was used in the Podium 1 loudspeaker : notice the resonant frequency and BL : 
http://www.hi-wave.com/downloads/datasheets/DS-HIAX25C15-8SF.pdf

[j gale]

Good points about the exciter used by Podium. I don't recall any complaints about the Podiums bass. Only one way to find out for sure.  HIAX32C208 is in stock, the other one is on back order anyway. I've been wondering about Podium's "sound bridges". Perhaps the synthetic  wine bottle corks ( rubber like) would be a good material. Should not be hard to cut into a suitable shape. If the frame dimensions were less than panel width, frame would be hidden behind panel except perhaps the bottom and then a simple slice of the cork is all that would be required. Podium article suggested that bass is improved by bridging the panel to the frame at just 4  points.

[bobloblob]

I am curious here about the interaction of the exciters and the panels.  It would seem to me that these operate as both DML and bending wave generators, and that exciters mounted as Sonic Impact did using the feet to attach them to a surface would tend to operate mostly as DML‘s since mounting totally to the panel would discourage bending waves at above bass frequencies, while mounting them to a spine behind the panel would allow the exciters to operate as bending wave generators at some higher frequency too.  In other words, how they are mounted would determine which way they make sound.  I don’t know whether that is true, nor more importantly whether it even matters.  Anyway, just curious about anyone else’s thoughts.

I think one that is “self-supporting “would therefore operate more as a true DML.  Yes?

[zygadr]

Wish I had the answers to the unknown areas of this technology.
Either way, no matter which way we mount the exciters, good sound is easily obtainable.

My quest for using higher power, high shove exciters became even more relevant last night when playing one of my favourite ''intense '' percussion CD's................I blew out both exciters on the left panel and stunk out my listening room  .
Fore one, my amplifier does not like 4 ohm loads, and secondly, I was pushing the volume level a bit too high for a couple of 5 watt exciters  . Guess it was bound to happen. No matter -  I have a couple more to replace the two I fried.
Just goes to show that to make the plywood panels sing loud, you need to have some power handling or the obvious is going to happen.

[doug s.]

Yes j gale it is a good contender!

However look at the specification sheet for the HIAX32C2O8:

http://www.parts-express.com/pedocs/specs/297-2114-hiwave-hiax32c20-8-specifications.pdf

Plus, it is ''self supporting''(no need for spine or reinforcement to avoid voice coil droop), 30W max power handling(on the HiWave website it shows as 20W - 40W !!!) and a 32mm voice coil.

It's BL  is 7.8    !!!!!!!

We can't forget that the above exciter is designed for industrial/commercial audio and to drive ''high impedance'', rigid substrates.
4mm plywood IS a ''high impedance substrate'' compared to cardboard or EPS.

Have a look  at the now not available exciter that was used in the Podium 1 loudspeaker : notice the resonant frequency and BL : 
http://www.hi-wave.com/downloads/datasheets/DS-HIAX25C15-8SF.pdf

HIAX25C10 is rated to 20khz, the hiax32c20-8 is rated only to 15khz...

doug s.

[zygadr]

What's a few Khz amongst friends ? 

Frequency response for that particular exciter was probably taken through glass or something ridiculously similar.
Low end response and especially high end response is very material dependant.

[doug s.]

What's a few Khz amongst friends ? 

Frequency response for that particular exciter was probably taken through glass or something ridiculously similar.
Low end response and especially high end response is very material dependant.

i understand.  but...  i would wanna start w/the widest frequency band as spec'd by the mfr.  however it's rated, (and who knows?), whatever substrate you are using, the 20khz unit will go higher than the 15khz unit.  as i said before - need more power?  add another exciter or two!     altho, in my case, at my age, i probably can't hear much above 15khz anyway!   

doug s.

[zygadr]

 

The 32mm voice coil would be the reason for the drop in high frequency response perhaps?. It's all a compromise I'd say?

[zygadr]

Just picked up two 4 foot X 2.7 foot,  2.7mm( ) thick premium plywood sheets from our Carpentry section here at work.

They are dead flat,very lightweight and attractive........far superior to the stuff I saw at the hardware store!

It will be interesting to see how much more efficient these sheets are compared to what I have at the moment  - 3mm standard ply and 4mm marine ply.
Despite my early good impressions of the 4mm marine ply, it has turned out to be noticeably less efficient and heavier than the 3mm standard ply...........and that's only a 1mm difference in thickness!

 At first, the marine ply did not seem to be all that different but after last night's percussion session,there was a definate mismatch between the two panels. Then when I blew one up there was a HUGE mismatch!

 Man!..........this technology is sooooooo weird!!!!

Will report when I assemble the new sheets with exciters.

[zygadr]

The 2.7mm thick premium plywood panels are in operation!

I was not expecting much of a difference beteween the standard grade 3mm ply and the premium 2.7mm............I was wrong!.
Even at that small thickness, the sheets stood rigidly upright with one edge leaning on some old bookshelf speakers placed on the floor.The edge in contact with the panel had some foam rubber isolating the sheet from the box.

There was suddenly a marked improvement in mids and highs as well as a slight but noticeable gain in output. Panel noise was not evident as far as I could tell.

Overall the following summary on sound quality using two paralelled el-cheapo exciters :
Using a selection of classical and Jazz CD's and digital radio broadcasts, the sound eminating from these panels is nothing short of impressive...............very impressive.
The highs and mids had an incredible crispness,clarity and extension that was a pleasure to behold. Strings within the orchestra sounded exactly as they do in real life - open, clean yet steely and agressive when the music called for it.
Once again, woodwind and brass were magnificent - you could hear their tonality and the rush of air through each performers breath on closely miked recordings. It was like being there.
Drums of course sounded brilliant as they allways do with DML's..............likewise with piano that sounded as real as you can get.
Minute details were emerging from recordings that I never realised were there before...........fantastic transparency!

I could go on and on but there is no need. What we have here is a great panel material that is let down by standard low power exciters. Time to go HIGH POWER/HIGH SHOVE and move on!

[zygadr]

Another factor discovered while researching various documentation on NXT/DML literature :

The 1.33:1 ratio (4ft X 3ft ) is apparently the most efficient ratio to use in respect to output level. The tall Maggie like panel shape is not the way to go in DML's.

[zygadr]

More info :
I have just emailed HiWave (formerly NXT) and asked the question as to which of their exciters would be best suited to drive thin plywood panels.
The two exciters mentioned are the ones that we have been discussing here on this thread.

Best to obtain the correct information before any funds are spent on multiple exciters.

[zygadr]

Sent another email a couple of days ago requesting an answer to my first email. I got a response from HiWave stating that a reply would take 5 working days and that they are ''looking forward to working with me''. It seems that they will be helpful in this last attempt at perfecting a DML ?....................I eagerly await their response!

[hblester3]

 Ziggy the news is exciting, maybe they will also give recommendations about exciter placement also. Still could not wait so I got 2 1/4 x 2 x 2 Birch plywood and stuck cheap exciters on and hung from the ceiling sounds good will have make a trip and find some thinner quality ply while waiting on exciter selection and hopefully placement and panel size. Thanks for all the info this is fun can only get better.

Hubert

[zygadr]

Hey Hubert!......my pleasure!
I was beginning to think that I was alone on this current quest as no one had responded to my latest posts.

The 2.7mm ply is really sounding very good indeed..........I am very surprised at the natural tonal quality and broad band response. the highs are truly outstanding and the low notes appear on que when they are present on the recording (the way it should be!).

As I sent the email on my work P.C., I will have to wait untill tomorrow to see if there is any reply...........I am hoping that there will be something this week some time.

I have had luck with NXT in the past so let's hope that the relationship continues in a positive way. 

[zygadr]

HiWave (NXT) have replied!!!!!!!!!

they have recommended the following exciter which I have already linked before as a possible contendor :

http://www.parts-express.com/pe/showdetl.cfm?partnumber=297-224

The HiWave representative stated the following :   ''I'd actually recommend HIAX32C30-4B ''balanced exciter''as this has a detachable (threaded)coupler ring which could be more easily and reliably adhered using a 2-Pack adhesive to a material such as plywood.This exciter is used for in wall speakers, classroom whiteboards and MDF kitchen doors and so should give you the improved performance you desire''.

I replied with thanks and asked about the significance of BL(force factor) and ''HIGH SHOVE'' types of exciters.