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

sedge · « **Reply #2500 on:** 16 Oct 2015, 02:28 am »

odal3
I should point out that 12ft is out of my listening area,my room is long and thin so the reflections get e little confusing ,I too have used slimmer panels and they do sound thinner

in the lower mid ,but as long as the lf driver blends in and fills the gap this can be minimised ,but still not as good as full width panel.
a solid contact between exciter coil and panel is a must for good hf ,an accidental knock to the panel can cause a drop of a few k or more but is easily spotted if as I do you use the mic in real time room mode all the time .
steve

sedge · « **Reply #2501 on:** 18 Oct 2015, 11:50 pm »

once again , for interest sake ,some pics of a plywood panel cut in two to make two 2ftx3ft panels , 1st the right panel, dotted line averaged peak hold is 2ft in front of exciter area, the lower plot is the mic moved 12ft to the back of room. notice dip at 200hz.

next pic left panel ,same as before.

next pic 2 panels L+R at 12ft only

last pic same as above except left panel moved 2ft forward, large 200hz dip gone.

even the half panel is pretty much full range ,in my room reflections from behind panel causing 200hz dip , moving a single panel 2ft forward moves the dip to 160hz.
can play quite loud but exciter gets warm ,impressive performance from single exciter on smallish panel, with real Lf performance (in my room anyway)
steve

Odal3 · « **Reply #2502 on:** 19 Oct 2015, 12:06 am »

Is the only difference between these panels and the ones you posted before the size? So how do you like them?

Remind me again how you mount them: I seem to recall that you put them on with pva glue after sanding the plastic exciter ring some. Do you locate them on Monacor position 1 or do you still put them in the middle as some of your earlier pictures?

Nickolay V · « **Reply #2503 on:** 19 Oct 2015, 12:23 am »

Hi!
Still, after all, what diaphragm material good ENOUGH :
XPS+PVA or honeycomb based (aramid honeycomb with Kraft Paper on both sides) ?
What diaphragm suspension better (for best high and low frequency):
attaching the entire perimeter or only on the (rounded) corners ?

Odal3 · « **Reply #2504 on:** 19 Oct 2015, 12:41 am »

@Nickolay - I think there are many different options and not sure if there is a clear winner other than personal preferences combined with what is easily available where you live. There is only one way to find out - try out some of the ideas found in the thread and compare it with your own ideas and report back. I have never had a chance to try out aramid honeycomb based ones.

In regards how to suspend the panels - my preference is to have the panels as free moving as possible. If attaching the whole perimeter, you may restrict the low frequency a bit so it may or not be what you like. My attachment point is a couple of cm below the upper two corners. Note that the attachment point change the frequency output some, so different panels/sizes may benefit from different placements.

sedge · « **Reply #2505 on:** 19 Oct 2015, 12:05 pm »

Odal3
Just got a saw and sawed them in half,wish I had thought about it a bit before hand as a 2ftx3ft using parts express method ends up with two edges the same distance from the exciter

Sound wise , the panels are too heavy to be really dynamic but would give an ordinary speaker a run for its money ,actually the panel would be a fraction of the price of any comparable sounding speaker.
Too laid back fore me,similar to the podium sound and other dml and nxts I have heard.
But impressive all the same,even with a low powered exciter.
As you say I usually use pva to glue the exciter to the panel with a little bit of scuffing of the foot with sand paper to help adhesion,I hope !
Only my very old panels have exciters in the middle ,before I New better.
The panel on the right is using monacor position,the one on the left parts express ,near field response shows not a lot of difference , far field response below 300hz is probably different because of room position?
I posted the pics so people could see the differences between the different types of panel and room response and that it is possible to get a nearly 20hz to 20k response from basic materials, sometimes at the price of ultimate sound ,we live and learn.
Nickolay v
I will answer you when I get a chance,I'm looking after my daughter's baby at the moment and it's not going well,I'm having brain meltdown

Steve

Nickolay V · « **Reply #2506 on:** 20 Oct 2015, 08:18 pm »

Hi FRIENDS !
I thank you for an good explanation.

sedge · « **Reply #2507 on:** 22 Oct 2015, 12:46 am »

Nickolay v
As Odal3 has said , getting hold of the right material is the main problem ,so it's down to what you can get hold of, I personally prefer eps but my supply has dried up ,only poor quality types are in the local diy stores at the moment,luckily I have my 5mm xps which is another good sounding material.
I wouldn't recommend heavy materials , this would include cardboard and similar honeycomb types as well as paper coated poly panels, it's probably easier if you say what you can get hold of ,then we might be able to give a few suggestions for getting the best sound.
If it's a full range panel you are after the 3mm plywood I am playing around with at the moment is interesting , I have decided to give it a little longer , to see if I can improve it a little,the fr of the panel is very impressive but the sound doesn't match the lighter panels,but am sure some would be very happy with them.
I have tried successfully to extended the fr of smaller light panels but the sound has always suffered so now tend to let the panel do what it does best and leave it at that.
Will post my findings.
Steve

mildperil · « **Reply #2508 on:** 23 Oct 2015, 04:24 pm »

Hello everyone,

I have been lurking for a couple of weeks now and though I should introduce myself and thank you for all for sharing all your findings so far.

I am in the UK and have been playing with exciters in a fairly lo-fi way for a few years. I run workshops with a company called Technology Will Save Us (TWSU), where we have people assemble a little chip amplifier board and then build DML speakers with exciters, all in 3 or 4 hours.

Anyway, I also build a lot of portable and bespoke sound system for artists and performers, and particularly, recently, sound systems for bikes for communal rides (Brighton Naked Bike Ride for example

). I though that DML had the potential to make a super lightweight portable system, so for the first time I started to take the technology seriously and that lead me to this forum, and it has been addictive reading ever since. I haven't made it to the end yet (about page 106).

I have been doing quite a few experiments (enough to realise DML have the potential to be seriously good), which I will probably go into later, but I thought I would let you know about another exciting(no pun intended) development. In the quest for some High Density Polystyrene I emailed a packaging company. The guy who replied was very friendly and said he would be happy to help, so I went along and he couldn't have been more helpful when I explained what I was doing. He even refused to take any money for the samples which were as big as I could fit in my car

. So in return for his generosity, I promised to send him an exciter and a little class D amp to play with. Anyway I just spoke to him again on the phone, and I think I have succeeded in getting him hooked

He has invited me back on Monday for Indian food and an afternoon of playing with materials, and teaching him what I know. He owns a EPS factory and a cardboard factory

So, with this amazing opportunity, I would like to ask, what would the ingenious and knowledgable folks of this forum like to try if they had they had the run of an EPS/cardboard factory? How can we optimise these materials when we actually have access to the machines that make them?

Ben

sedge · « **Reply #2509 on:** 26 Oct 2015, 02:16 am »

I moved the plywood panels to my living room to find out if the fr would hold up in a larger room this is a pic of them.

this was my first plot in the room at 10ft in front of panels.

I moved the mic out of the way and accidentally found a spot 2ft further back that cancelled the suck out in the lower midrange .

personally I preferred the sound of these panels from the exciter side as in this pic.they sounded more lively this way,but this is my own personal taste .

this I a genuine full range panel ,room treatment for the suck outs in the lower mid would be an obvious thing to do and as I have said before an lf driver to take the strain in the low end ,not that the low end is week but just to save the exciters from damage, unless you use more powerful exciters of course ,the top end fr can be EQ ,but wasn't offensive ,the sound was impressive ,similar to the podiums I felt,but not as good as my poly panels for the reasons I have stated before.
I did take more plots but they looked very similar to other plots already posted while moving them around the room.
3.5mm is easy to get hold of ,not very expensive easy to cut in half , just glue on the exciter with pva and that's it ,my wife also tells me it is loud,thank you for that dear

Ben
you engineered panels to fit on bikes for the Brighton naked bike ride ,interesting to know how you got to the bottom of that one

I did get samples of polystyrene but it was going to be expensive because of the quantity that had to be ordered ,I used B&Q and wickes in the end but their quality has gone down so unless they get more good stuff in I'm stuck with what I have got left
keep us informed
steve

Odal3 · « **Reply #2510 on:** 26 Oct 2015, 02:46 am »

Please give your wife a big thank you from all of us for letting you experiment in the living room!

It's very interesting hearing about your impressions of the different panels. Are the pillows to keep the panels steady?

sedge · « **Reply #2511 on:** 26 Oct 2015, 01:47 pm »

I wouldn't quite say my wife let me test my panels ,she went out for the day and came back to the living room from HELL!!!! not a happy bunny, but once she had calmed down a bit I managed to get her to have a little listen(even with the head ache ) she said they sound very detailed and spacious and liked them ,then told me to get them out of the room!

more pics in the room without the pillows ,I just wanted to see if they would stop some of the reflections from the ceiling ,not a lot is the answer ,went to a room treatment seminar at Whittlebury hall audio show in sept this year and was interesting to learn that you can get sound panels to tune in to cancellation frequencies in the lower mid range , all quite expensive and intrusive in the room,ceiling,walls corners,floors. my tls in my room helping in this area sorts out this problem cancelling the cancelations ? it just works

this last one was with the mic about at least 1 mtr from the panel

steve

mildperil · « **Reply #2512 on:** 26 Oct 2015, 08:58 pm »

Today I managed to get hold of some 5mm 600mm x 800mm Re-Board. I have read that others on this forum have tried the 10mm thickness, has anyone else tried the 5mm?

I can't believe how jaw-droopingly good it is with a single Dayton DAEX25FHE-4 exciter powered by A TPA3116 board, and just clamped one one corner

. I have been pleased with my polystyrene panels, sanded and PVA coated, but 5mm Re-board just seems a different league. The clarity and cleanliness of the high frequencies, are as good as I've heard anywhere (I can't hear about 15kHz, so it might roll off a bit and I wouldn't know). The 5mm seems light enough that the efficiency isn't far off EPS, and it has a bit of flex for the low frequencies. I can imagine the 10mm would be a bit too heavy a rigid for a single exciter (I have tried a similar material in 10mm and it wasn't quite as good as the Re-Board). The main draw back seems to be that I haven't been able to fine it in sheet sizes larger than 800mm x 600mm

I can't imagine that I could get Polystyrene to sound as good but I did manage to get hold of a good size piece of 10mm ultra high density EPS from my friend with a packaging company, so I'm looking forward to doing the treatment.

Also this evening I came across an old test I did (for a completely unrelated idea) of corrugated cardboard soaked in epoxy resin. At the time I dismissed it as too flimsy, but it seems to have cured much harder in the time I have been ignoring it, so I held an exciter against it, and wow, it is really good!.

It started me thinking, about making my own panel using corrugated packing roll like this http://www.amazon.co.uk/600mm-Corrugated-Cardboard-Paper-Roll/dp/0788631136. it is essentially the wavy bit in the middle of corrugated without the paper skins either side. You would paint epoxy onto this wavy centre and then lay a skin of paper either side (it could be wall paper or some other attractive, decor friendly type). It would hopefully end up as very incompressible (the key for good high frequency in my opinion) attractive DIY cardboard.

Ben

Has anyone else tried making their own panel material from scratch (sort of)?

Odal3 · « **Reply #2513 on:** 27 Oct 2015, 12:45 am »

Ben - good to see more people on here!

No good ideas how to pre-manufacture foam panels other than incorporating the "skin" when made.

Did you use panels for the bikes?

sedge · « **Reply #2514 on:** 28 Oct 2015, 10:52 am »

Mildperil
Not sure if anyone has tested the 10mm or the 5mm re board, do you have some way to measure the panels performance, the more different panels tested the better , each type of panel will have its strengths and weaknesses ,who is the supplier you are using,do you have to buy in bulk?
Keep up the good work.
Steve

Gregory Roig · « **Reply #2515 on:** 29 Oct 2015, 01:47 pm »

Hey Everybody,
Gregor here, a newbie. I posted a new topic "DML open baffle for pro sound" but might as well continue here. Am interested to learn as much as possible about creating LOUD DMLs for pro sound reinforcement.

Should I use a thicker material with more exciters for more SPL? Any recommendations...?

sedge · « **Reply #2516 on:** 30 Oct 2015, 02:26 am »

Hi gregor
A Pro sound panel would be a totally different beast to anything I would use at home but it will make a great forum ,have read your post and will join in,just need to know more info on exactly what you want to use them for,not bass guitar I presume,what fr needed and so on.
Not sure about using this site though.
Steve

Gregory Roig · « **Reply #2517 on:** 30 Oct 2015, 12:07 pm »

Steve,
Thanks for the reply. Please see my post at topic "DML open baffle for pro sound use" where I've given some parameters.
Really appreciate the help.
Gregor

Gregory Roig · « **Reply #2518 on:** 31 Oct 2015, 02:36 pm »

Hey,
Has anyone tried a variety of mediums and or thicknesses in a single panel? I know nothing of the physics of such a configuration but wondered if it might help in the randomization of FR. Probably crazy...

Gregory Roig · « **Reply #2519 on:** 31 Oct 2015, 02:42 pm »

Sedge/Steve,
What kind of SPL are your 2 x 3 panels capable of (please reference to 1W/1M) and using how powerful an exciter? Looks like real potential for me. I could fine tune them using a graphic and/or parametric equalizer...