NXT.......rubbish??....THINK AGAIN!

buzz · « **Reply #920 on:** 15 Apr 2010, 12:51 pm »

Hi Z,

Interesting! What was old is new again

Has anyone had a chance to use the "High Shove" exciters yet?

I am curious if the sensitivity is high enough for tube amplification.
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=300-377

sedge · « **Reply #921 on:** 15 Apr 2010, 05:37 pm »

Zygadr
The drive units that look very similar to the exciters [phew ,that was a close one!!!!]

looks as if it is only used as a Lf driver in piston mode?

Emailtooa
Polystyrene will be very efficient ABS not so.
I did try a 12inch ABS panel it sounded ok but not great ,but don’t let that stop you trying a larger panel if you can get hold of one.
Until you try you don’t know.

emailtooaj · « **Reply #922 on:** 16 Apr 2010, 01:39 am »

Sedge
Thank you for response!
When I mentioned using an ABS backing on Polystyrene sheet, I actually ment to refer using a very thin ABS sheet(1/32"), or even a type of film. Thoughts?

I had a brain fart earlier this week

, Has anyone tried shaping a polystyrene sheet? My thoughts are that by shaping the panel you are kinda tuning the panel for the desired freq responce. I'm gonna draw what I think it would look like and post it so I can get some feed back and ideas.
I found a local styrene sheet distributor that I plan on visitng next week and buying some material and try this theory out.

Has anyone tried different types/grades of polystyrene? If so what would you recommend me to buy.

My "approach/idea" to achieve MOT out of the panels is to view it as a sound board. Kinda like a piano's sound board!?
Anybody think I'm crazy yet

zygadr · « **Reply #923 on:** 16 Apr 2010, 04:49 am »

The ''high shove exciters'' have a 3 db increase in sensitivity over the standard type.

So, this makes them about 79.6 db from memory.

If you use more than one.......say two pairs paralelled, then series wired, you should get around(theoretically speaking

) 91.6 db.

However, this is all dependant on the material used. Heavy material will kill the output, so the above means nothing.

If your tube amplification is in excess of 25 watts per channe(30-40 watts preferred) and you use VH grade(VERY HARD) polystyrene sheet(very light), you may just scrape it in if you have a big room and like to listen to your music reasonably loud.

In my opinion, they are only good for medium powered solid state.............but that's just my opinion from my experiences so far.

DanTheMan · « **Reply #924 on:** 16 Apr 2010, 06:24 am »

91 dB from a panel? Wow

doug s. · « **Reply #925 on:** 16 Apr 2010, 11:46 am »

Quote from: zygadr on 16 Apr 2010, 04:49 am

The ''high shove exciters'' have a 3 db increase in sensitivity over the standard type.

So, this makes them about 79.6 db from memory.

If you use more than one.......say two pairs paralelled, then series wired, you should get around(theoretically speaking ) 91.6 db.

However, this is all dependant on the material used. Heavy material will kill the output, so the above means nothing.

If your tube amplification is in excess of 25 watts per channe(30-40 watts preferred) and you use VH grade(VERY HARD) polystyrene sheet(very light), you may just scrape it in if you have a big room and like to listen to your music reasonably loud.

In my opinion, they are only good for medium powered solid state.............but that's just my opinion from my experiences so far.

if one exciter is 80db/1w, using four nets 86db/1w. eight gives you 89db, sixteen gives you 92db, etc.. of course, this is for a single speaker - add 3db for a stereo pair.

doug s.

ondesx · « **Reply #926 on:** 16 Apr 2010, 05:22 pm »

Here is an example of a couple of panels (only one represented) each made with four 2-Way tiles (one driver for highs and one for medium-lows)... Look here if interested http://www.parts-express.com/pe/showdetl.cfm?Partnumber=249-462

I must confess that the sound is not so good... I try them only for mids, but it isn't easy to match with the other drivers.

I think something is wrong with some materials and/or drivers for NXT panels. But I don't know what...

zygadr · « **Reply #927 on:** 18 Apr 2010, 06:17 am »

When you paralell 2 drivers, as long as they are spaced within 1/4 wavelength of each other, you will obtain a 6 db increase not 3 db.........3db from the drop in impedance and another 3 db due to doubling of SPL from using two drivers together.

That information was posted as a link way back...............I'm not going to post it again.............half the reason why this thread has gone to crap. I have repeated myself and information so many times that I'm sick of it.

Feel free to look up my posts filed under my profile and you'll eventually see the article I am referring to.

In the mean time, keep attaching exciters to bricks, sides of battle ships, trees..........whatever.

By now, anyone seriously interested in building a pair of panels that sound better than they have a right to would have done so already, as they would have ''remembered'' what works and what doesn't...............congrats to them!

vaugi · « **Reply #928 on:** 18 Apr 2010, 08:42 am »

Thought this might be interesting re: exciter placement

http://www.amina.co.uk/product_theTechnology.html

zygadr · « **Reply #929 on:** 20 Apr 2010, 06:48 am »

Yeah, without acting like a smart ass, I've done that..................didn't work as good as the vertical array................this method is hard to beat as many have found.

doug s..................my apologies.....despite the documentation I was referring to, I think you are correct in the 3db increase(and not 6db as I had suggested) in paralelling drivers.

From the Amina specs/brochure, 4 ''high shove exciters''(which they use) are only 85 db at 1w/1m

I think that this is the only problem with these exciters.............they are low sensitivity AND low power...........impossible to win that war with high quality low powered amplifiers and suboptimal panel materials

sedge · « **Reply #930 on:** 21 Apr 2010, 02:55 pm »

Ondesx
Have you tried mounting your panels vertically on a central beam, such as a piece of 2by 4 say 8ft tall[ceiling permitting ] so that the edge of the panels are left to freely vibrate .
If you have read all of this site[ok half of it has been deleted

] you would know that if you rigidly mount an exciter panel in a box you will kill the sound .
I do not know how good your ceiling panels sound but if you freely mount them [my panels are just hanging in mid air] this will give them a chance to sing .
You may also have to modify the units a little to get that little bit extra out of them ?
Hanging them in mid air is so easy and cheep but is also the best sound .
All the best
sedge

sedge · « **Reply #931 on:** 21 Apr 2010, 03:23 pm »

Vaugi
Very interesting site ,I see they are using a ali honeycombed panel with a doped paper surface ,which you apply a 2mil thick plaster coating .
I wonder if the plaster coating makes it sound better or worse?

I must admit to trying to put a thin layer of plaster on my inch thick 12inch wide styrene panels ,but with my skills as a plasterer, you can imagine what that looked like

.
I am wondering if I should try this again with the 5mil panel?[maybe a little thiner this time]

Any thouhts
sedge

ondesx · « **Reply #932 on:** 21 Apr 2010, 04:08 pm »

Quote from: sedge on 21 Apr 2010, 02:55 pm

Ondesx
Have you tried mounting your panels vertically on a central beam, such as a piece of 2by 4 say 8ft tall[ceiling permitting ] so that the edge of the panels are left to freely vibrate...

Hi Sedge,

Thanks for the input !...
Well, this is my first try with "commercial" panels including 2-way exciters.
I must admit that the tiles are firmly installed in the frames. And may be that is the reason why they don't sound as clear as expected (I did some experiments with single exciters and various materials leading to much better sound indeed, it remains a try with some honeycomb sample sheets I'm waiting for). I will try to "free" them a little, one of these days, to see what would happen.

But anyway I remain convinced that there is something wrong, since even the match with the other subranges remains an issue and that a simple dipole, respecting some very simple specs, will sound much better for less effort... Moreover, matching of dipoles seems to be much easier. Even with monopoles for very low frequencies isn't a drawback. That's why I'm working on an hybrid monopole/dipole design with an active configuration (both for amps and xover).

Stay tuned.

usp1 · « **Reply #933 on:** 21 Apr 2010, 04:54 pm »

After putting my panels away for awhile, I went back to them to show a friend how they sounded. Alas, the exciters were on the floor in a bunch since they had come of the panels. It looks like the original recommendation of 3M F9473PC tape does not make for a lasting solution. Oh well...now I have to decide if I want to keep the extra exciters I bought or sell them off.

zygadr · « **Reply #934 on:** 22 Apr 2010, 02:21 am »

usp1..................I removed the 6 exciters from my Gatorfoam panels just the other day.
At one time this was a difficult job and needed a very thin wedge or hobby knife to cut away and lever the exciters.
This time they came off VERY easily

.............just goes to show that the back brace is essential......at least if the exciters are to remain in position.

Either way, I'm done and dusted with them................too many problems, too many critics and no answers or solutions.

usp1 · « **Reply #935 on:** 22 Apr 2010, 01:39 pm »

zygdar _ It was fun while it lasted. The problem of affixing exciters is probably easy to solve but the rolled-off HF are more of an issue for me. I am sure one can rig up a super-tweeter bu that looses the simplicity of design. I keep checking this thread to see if some of the more knowledgeable and experienced members (including you) have a solution to the problem.

zobsky · « **Reply #936 on:** 22 Apr 2010, 05:54 pm »

The cheapo piezo tweeter , perhaps ?

zygadr · « **Reply #937 on:** 23 Apr 2010, 01:53 am »

zobsky is correct - mount a dismantled piezo (cone assembly only) to the back (not front, and no holes through the panel!) of any panel material and your high frequency problem will be dramatically reduced.
Just wire up the piezo paralell to any of the existing exciters, no crossovers or resistors etc. required.

I once mounted them in a mirror image pair, off to the far sides of the panels and found the result more than adequate in the high frequency department.

1. you will still be using a DML radiator in the form of a vibrating piezo cone, which does also output through the panel(slightly)
2. a piezo is considered to be a DML transducer anyhow

So, there is no bastardisation of the DML principle here............just an additional implementation.

panomaniac · « **Reply #938 on:** 24 Apr 2010, 02:45 pm »

You haven't given up on the adhesive, have you? I was getting keen to have another try. Thought it had all been sorted out.

usp1 · « **Reply #939 on:** 24 Apr 2010, 03:11 pm »

Given how expensive the 3M F9473PC is, it was very disappointing that it did not work. It was much stronger than the double sided tape I used for my first few panels (the exciters used to fall off very quickly with that tape). Without a brace, there is a domino effect. Once one exciter falls off it pulls the other exciters down.