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

mightym · « **Reply #940 on:** 24 Apr 2010, 08:10 pm »

I have yet to build a panel, though one is planned/designed.

I was planning to try the double stick tape that is used to put down outdoor carpet's

It's a polyurethane based adhesive, readily available, has a mylar substrate ( IIRC ), and is 2" wide.

Has anyone tried this?

John

Raintree17404 · « **Reply #941 on:** 25 Apr 2010, 02:42 pm »

1st post here.

I have been attaching exciters to both Elmers Foamboard and gatorboard using Gorilla brand impact tough super glue and have had good results so far. I also use PE Insta-Set accelerator which makes for faster work mounting multiple exciters. Maybe the accelerator also helps with the strength by allowing a full set while pressure is maintained (the thinner the glue film the stronger the bond as I understand)? My PE $5/pair exciters have the plastic suspensions removed so it's only the voice coil foot supporting everything. I haven't had one come off yet and I've dropped one panel unintentionally from 2.5' to a hard floor, enough to deform the edge of the gatorboard.

At the moment I'm enjoying these using them nearfield hanging from a ceiling mounted bracket and braided fishing line. My small scale test set up is a combination of what others have done here along with some of my own design ideas (intentional & unintentional). For each channel I am using 2 panels 10"Wx30"H, 2 exciters wired in parallel. I had already tested 2 exciters (4 ohm each really?) in parallel with my T-amp and was surprised it did not balk at the low impedance load. The kicker is that I then unintentionally wired both panels parallel for a total of 4 exciters in parallel! Well the sound is just awesome and the little PE T-amp seems to handle the 1/2 ohm load (really?) like a champ. It will only go into protection at ear ringing levels. I can only guess that the 24 gauge speaker wire I'm using may bump the resistance up slightly. Music which sounds best as reported previously are vocals, acoustic, and live performances (almost any kind of music). If it's a good live recording it seems that the fake bass of many studio recordings is omitted. I have plenty of exciters to move to the next step, two 1'x7' panels for each channel to maybe get better bass extension, or four 1'x3.5' panels. I think 2 exciters per panel may be the key because getting plenty of highs is not my problem. Maybe the solution is more panels with two exciters, and not tons of exciters on one panel. If amp load is a problem I would think just use all channels available in a home theater receiver to listen as simple stereo. My Denon can do this but I haven't tried it yet since the T-amp sounds great nearfield. I'll try the Dennon with larger/more panels when I get the time.

usp1 · « **Reply #942 on:** 25 Apr 2010, 03:25 pm »

Raintree - Did you actually measure the high frequency reponse using test tones? I cannot seem to get more than about 12 khz out of gatorfoam with two exciters. (I did not try them in parallel though) Perhaps the 3M tape might have been the culprit as well and using gorilla glue might be the solution.

Raintree17404 · « **Reply #943 on:** 25 Apr 2010, 08:57 pm »

USP1...I never gave it a hard thought, just always went by what I thought sounds best. I found some test tones and will let you know what I'm getting with my gatorboard setup. I did plan on testing too some piezos firing up at the ceiling to see if there was any "air" in the music I may have been missing with the exciters. Once the kids are in bed I'll post my results.

Raintree17404 · « **Reply #944 on:** 26 Apr 2010, 02:44 am »

USP1...I went to several test tone sites, but liked this one best with the voiceover of the frequency being played.

http://www.audiocheck.net/audiotests_frequencycheckhigh.php

This also gave me an idea of the relative loudness of the high frequency tones against the loudness of the voiceover. Drum roll please...16K and 17K were still quite loud, and the 18K was audible but the volume was limited, with nothing heard at 19K or above. You should have seen my two dogs bolt to the other side of the house. Actually I didn't know I could hear that high still with all the abuse I've given my ears over the years. I've had a 590 watt car stereo since I started college just over 20 years ago (2 Carver 120w/ch amps and a 75W/ch Proton) and still crank it up quite often. I've always appreciated music clarity at high volumes (largest woofers are 10", I like clean bass). I liked the sound of the T-amp with the gatorboard mounted exciters regardless of this test, but anyway it would be nice to see someone else verify my findings to help resolve the high frequency problems others are having. PE T-amps are cheap enough so when it sounded so good I was willing to run it hard to see if it would last. I have a second T-amp on the way to biamp the left and right channels, and maybe double the number of gatorboard panels per side. My Holy Grail quest seems to be bringing out the low frequency enough so I don't need a sub with my gatorboard speakers. I only plan to use them for stereo music listening. I'll leave the Denon receiver to the home theater task.

Try those exciters in parallel pairs only, and try two panels per channel in parallel if you dare. I would not risk an amp worth any more than a $45 PE T-amp with the supposed 1/2 ohm load I'm suggesting. Haven't burned one up yet though, and it seems to just go into protection mode when pushed over the limit. I suggest pushing to the limit so you know where it is and then play it below this level. One interesting thing at the 1/2 ohm load level is that the T-amp never seems to show high distortion near the limit like it does at 8 ohms. If I put a heatsink on this chip amp do I get more headroom/volume still?

Raintree17404 · « **Reply #945 on:** 26 Apr 2010, 03:01 am »

PE recommends mounting exciters with the gel type super glue, and the Gorilla super glue I used is supposed to have better shear strength than regular super glues. Understand that I've only been tinkering on this for 1 month so I can't attest to long term adhesion, but super glues are used for dentistry so I would tend to think it is a long term performer unless the gator board surface is what gives out first. The 3M adhesive tape possibly could be sapping some of the highs others are reporting? This is not high dollar stuff we are tinkering with, give it a try.

Also I have a pair of the "High Shove" exciters and I'm not really impressed. They don't sound any better to me and are only slightly more efficient. Their cost premium doesn't overcome the fact you can buy 16 pairs of the little guys for the same $$$, and with the "High Shoves" you are forced to construct a brace to support their motor structure. I prefer the stick and go type which speeds prototyping and saves cash. 4 pairs of the little guys are immensely louder than one pair of the "High Shove".

Raintree17404 · « **Reply #946 on:** 26 Apr 2010, 03:22 am »

If anyone is wondering I placed my $5/pr exciters at the locations recommended by NXT in the paperwork that came with the high shoves I bought too.

Exciter X(width) Y(height)
1 4/9X 3/7Y
2 4/7X 5/9Y

With my test tone results hitting 18kHz I'm not bothering with even trying the piezos. I don't need the burn and my laptop EQ can easily get me more treble at the top than I care for.

Raintree17404 · « **Reply #947 on:** 26 Apr 2010, 04:25 am »

Bass test tones, nearfield examination with PE T-amp (two 10"x30" gator panels per channel, 2 exciters in parallel per panel, both panels in parallel per channel).

http://www.testsounds.com/

50Hz audible but relatively weak
60Hz clearly audible and as satisfying as a test tone can be
100/125/250Hz clearly audible and 125 a bit louder than 250? (would have thought 250 would have been the jump point)
400 clearly audible and louder which confirms my current laptop EQ settings (just season to taste)

On this test tone site the high frequency tests sound good to 15000Hz, but 16000Hz and above getting crazy sounding oscillations that clearly are not that high of a pitch as the test tone selected. I didn't get this result at the other test tone sites so I'm not overly concerned.

usp1 · « **Reply #948 on:** 26 Apr 2010, 04:35 am »

Very interesting. I will try that when I have some free time...but does it have to be parallel exciters...my amp may not live to tell the tale.

Raintree17404 · « **Reply #949 on:** 26 Apr 2010, 05:31 am »

I don't know for sure exactly what the secret is because I have only tried one configuration so far. It sounded so good on the Elmers foamboard that I transfered it to gatorboard which is all but the biggest expense item. As far as I can tell the gatorboard doesn't materially sound better (or worse for that mattter), just that it's more durable and better looking in black. I too would not expose an amp of any real $$$ value to less than 4 ohms unless it is rated lower (few non-car audio amps are). Buy a $45 T-map and see for yourself. It's a great little amp you can take anywhere with a tiny set of speakers and it will push out great sound (beach, office, nearfield listening, and more than nearfield if you don't need concert volume levels). It runs on 8 alkaline/rechargeable AA batteries and will whoop any 8 C/D battery boombox I have ever heard. For using with my 2808 Denon receiver, using all channels, I need to figure out how to get to at least 4 ohms before I'll even consider giving it a try. Is there an easy way to test impedance? All I have is a multimeter to test. From the little I've read running speakers in series clips high frequencies, how much I'm not sure. I'm guessing if it's clipped and "not there" that you can't even boost it with EQ to recover.

Raintree17404 · « **Reply #950 on:** 26 Apr 2010, 05:55 am »

This 1/2 ohm setup I think I have constructed breaks all the rules with amps (I'd love to test to find out for sure). My little T-amp should be toast but it's not and it keeps playing along willingly and loudly. I double checked yet once again, and yep it's 4 exciter drivers wired in parallel per channel.

To test frequency response for yourself you could always put a 4ohm resistor in series. It would kill your volume level but you could at least test to see if it truly is the parallel wiring that gives the HF response you are looking for. I can see a system with 4/6/8/10 of the $20 PE T-amp modules partnered with a large scale power supply the size of a typical amplifier.

doug s. · « **Reply #951 on:** 26 Apr 2010, 12:50 pm »

wouldn't four paralleled 4-ohm drivers result in 1-ohm load, not 0.5-ohm?

doug s.

Raintree17404 · « **Reply #952 on:** 26 Apr 2010, 02:36 pm »

Doug...you are correct, my mistake. Two 4 ohm loads in parallel = 2 ohms. Both those two ohm loads in parallel = 1 ohm. I still don't know how this little amp pushes this load without frying. Even if the PE buyout exciter is mispec'd and is actually 8 ohms like its Dayton DAEX25 brethren, that still would be a 2 ohm load.

sedge · « **Reply #953 on:** 27 Apr 2010, 11:23 pm »

Zygadr
Could you tell us what happened with your thin styrene panels ?
I sill only have the one 5 ml thick panel which I have put various coatings on and am still impressed with the sound .I also tried a 2/3 from corner to corner position and this sounded clearer [to be confirmed later]but lost LF output.I think this is why the styrene ceiling tiles have one exciter in the middle[LF ] and one exciter on the edge [HF]plus xover to stop cancellation ?
I have been concentrating on my thin ali panels and am thinking of using at least 2 or more panels per channel [one exciter per panel],this would solve the cancellation [on the panel]and volume problem in one go.When I added a second exciter to the panel I seemed to loose volume [cancellation effects ]the far field response seemed ok though.?
As I have said before these panels easily go all the way up to and beyond 20k.
Last night I was comparing the ali panel on the left with the styrene panel on the right ,the ali panel sounded more laid back and relaxed ,and the styrene panel more alive and vibrant ,in the end I ended up listening to them both at the same time in stereo till 3 in the morning ,they sounded great together .
I am about to go and have another listen and predict another late night

.
Night all
sedge

zygadr · « **Reply #954 on:** 28 Apr 2010, 02:00 am »

sedge, forget that ''ali '' shit.

Use the 10mm VH grade polystyrene with four exciters mounted vertically, evenly spaced.
Use a back brace..............hold the backs of the exciters to the brace with silicone sealant AND use blobs of silicone on all four corners of the poly................and stick that on top of a wooden frame with an opening slightly smaller than the poly size.

This is the best way..........the only way. There is no other.............do we all get it now???

Forget flea power amps...............go T AMP as suggested earlier by Raintree, or use an amp with some guts at medium power.

emailtooaj · « **Reply #955 on:** 30 Apr 2010, 01:46 am »

Zygadr
Did you get your VH grade poly off the internet, or do you get it localy?
I've tried to find VH grade poly here in redneckville and thier response is... "We gots the can that you can spary!"

Do you have a link to the product(panel) you are using?
Also, what are your panel sizes? I see your using 10mm.
The exciters your using, are they Dayton $12/pair from PE. Or are they
the PE cheapo $5/pair? I bought like a dozen of the cheapo's, so I have pleanty to work with.

Are you treating/coating the panel with anything like resin or spay plastic? Or are they just strait up, plain VH Polystyrene?

I would love to repilcate what you have built and compare it to some of the materials I've been using to experiment with. I wanna hear what you are hearing!

On a side note...has any one messed with Gatorplast panels?
If so what was/is your thoughts?
I know Gatorfoam has been tried

Word!!
AJ

Raintree17404 · « **Reply #956 on:** 30 Apr 2010, 01:56 am »

zygadr - you mention using 10mm VH grade polystyrene. I received a free foamboard specifier kit from The Gilman Brothers Company http://www.gilmanbrothers.com/kit.html and it included a sample of 12mm / 1/2" "Stylite" described as a fine-celled extruded polystyrene foam (it is unfaced). To get the kit just send them an e-mail and it arrives at your doorstep in less than a week. Amazingly this free kit includes 27 different foam board types in 8.5"x11" format. They also offer the Stylite product in 5mm / 3/16" and 10 mm / 3/8" thicknesses. I'm curious if this is the same VH grade polystyrene you are using? Stylite is quite rigid and even at 1/2" thick is definitely lighter than 3/16" gatorboard of the same HxW (and I would assume more efficient). But while it is rigid it is significantly more flexible than gatorboard since it does not have the reinforcing faces. Do you recommend the 10mm / 3/8" and not the the 5mm / 3/16" due to too much flexibility (or warpage potential) in a larger size format? I'm trying to figure out if the thinner panels are better in smaller WxH sizes. Am I understanding correctly that you are recommending an unfaced fine-celled polystyrene board, correct? I doubt using super glue for this unfaced polystyrene surface would be a good idea, it's not all that durable (yet rigid it can be relatively easily scarred with a thumbnail).

emailtooaj · « **Reply #957 on:** 30 Apr 2010, 02:48 am »

Nice find Raintree

I'm gonna give them a call tomorrow and see what the deal is.
Try out thier sample pack possibly.

I was looking at McMaster Carr site and came across this...
http://www.mcmaster.com/#polystyrene-foam/=6vn93s
Only problem is they just sell High Density in 1" thickness.
Guess you could try to cut the thickness is half?

zygadr · « **Reply #958 on:** 3 May 2010, 07:42 am »

Bloody hell!.................so many questions

Firstly, I use the more expensive, now discontinued sonic impact sound pad exciters.The cheaper one's are just as good.

VH grade polystyrene sheet is like any normal polystyrene sheet BUT................it's HARDER........that's all.Put two pieces side by side and there is an obvious difference......one is more fragile where the other is not........it's simply a'' higher quality grade''

Both types however do not have the rigidity of gatorfoam.............but that's where the trade off is.

With the VH poly, you have a much lighter, therefore MORE EFFICIENT

panel that has far better output and high frequencies.............our biggest problem all the way along.

I use 10mm because that is the thinnest available(it comes in 10mm and 25 mm).

A 6 foot x 3 foot sheet is perfect.

If you can't get the VH, then maybe try the standard stuff in 10mm..........no thicker

Good luck.

zygadr · « **Reply #959 on:** 4 May 2010, 07:19 am »

The Australian distributor for ''EPS''.........EXPANDED POLYSTYRENE SHEETS(notice the referal in light gray, to double the price for the ''HARD'' grade):

http:www.foamsales.com.au/products/polystyrene/polystyrenesheets/