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

OB_Newbie · « **Reply #2220 on:** 12 Jan 2015, 08:19 pm »

Quote from: Odal3 on 12 Jan 2015, 05:06 am

I currently have them on 2.5 x 5ft birch panels. One has thickness of 1/8, which doesn't sound too good, and the other has 1/4 thickness.

BTW: Here are some measurements of the XPS panels. Shows similar fall-off on the LF as the ones you posted - birch panels shows a much smoother LF, but the XPS has better and tighter high end. Mic at 3 ft (used the umik-1) - the lines shows the same panel but just with different smoothing applied. Probably can't read too much into the chart because it is measured in my unfinsihed basement with concret floor, misc stuff and other reflective things.

Hey Odal,
Thanks for the measurements. I have to go back and look at Sedges RTA measurements. Think they are pretty similar to and the reason why he uses a TL woofer to fill in the panel's uneven response.

I bought a more precise RTA last week and got much more similar results in the LF range :

Close miced'. I seem to be getting better HF response but not sure as to its accuracy either.

Does anyone understand why the jagged LF response? Can only assume it is the panel flexing!?!?

The less flex the less jagged the LF response is? I think we perceive more bass output than is there due to the large spike around 80Hz?!? Probably also explains the bass quality issues that we hear?!?

Do you have measurements of your birch panels by chance? interesting to compare them.

sedge · « **Reply #2221 on:** 13 Jan 2015, 03:30 am »

Exspec
It is not easy to recommend a panel type that will suit everyone ,I can only say what I think I might do if I had two pairs of h frame panels and wanted to dip my toe into dml type panels,the easiest and cheapest to obtain would (in the UK ) be the 1inch thick polystyrene panels from B Q or wickes from 7 pounds for a 4x8ft sheet.
To keep my options open to experiment I would cut the sheet into 2 panels of say 3x4ft which leaves one panel of 2x4ft hopefully the 3x4 panels would get you easily down to your 200HZ Mark room cancellation permitting.
To start with I would use the panel full range and see whether you really need a tweeter ,the unaltered panels should give a good response up to at least 10k with a lower output up to 20k but this lower output would be radiated all round the room,not beamed to one point ,this can be improved at a later date if you think you like this panel.not bad 7 pounds for three or more panels.
Maybe try 5mm panels at a later date?
Forgot to mention that these panels are high output panels and only need one exciter per panel and can be powered from a small t-amp ,you may be surprised to find your h frames working hard to keep up.
OB_newbie
Please,please do not use square or round panels ,you can make them sound better by off setting the exciter ,but not good enough.
Steve

OB_Newbie · « **Reply #2222 on:** 13 Jan 2015, 04:47 am »

A few quick measurements tonight. 24 in. x 30 in. 1 in thick XPS panel using the new Dayton Audio DAEX32EP-4 exciter. Not much time on them but they sound amazing. The low freq. response is very much improved.

Hey Sedge, only my first test panels are square, they were precut and handy project panels. But I really like them... even square. I would have gone a tad taller on the fresh panels to test the thrusters but had a 2 ft. x 5 ft. panel on hand so halved it. Surprising LF output for such a small panel.

close miced' 1 ft.

Far field - 8 ft.

Odal3 · « **Reply #2223 on:** 13 Jan 2015, 06:07 am »

Since you asked...here are some comparisons between 2.5 x 5 birch panels with thruster exciter (purple) and 2 x 4 XPS panels (green) (re-coated with cheap exciter). Same measurement, just different smoothing. Panels measured at the exact same location, stand and volume settings. It's pretty obvious which area each panel excels. Exciters attached with VHB tape since I didn't have any good glue at home. Birch panels sanded down to 200 and as an experiment I put some diluted pva glue about 5" diameter around the attachment point for the exciter. This and the fine sanding helped smooth out the mids, added the bump between 3-4k, and the two smaller peaks over 10k. The unsanded/treated birch panels barely moved the needle above 8k. Next step is to round and taper the edges a bit more, which I hope will help smooth out the 10k dips. It made a lot of impact on my smaller birch boards. May also re-skin the whole front. If you compare the XPS line in these charts vs the one I posted before (which only had the pva applied to the backside), you can see the difference in HF around 20k Hz.

Since I have little clue what I'm doing when measuring, and my basement is not the best measurement place, one has to be careful to not draw too detailed conclusions from it.
OB_Newbie - play around with dampening on your panels either by tape, Sedge pva/shellac method, cedar rings, moongel or whatever you have at home, where you lean/attach suspension points. It makes a huge difference regardless if you suspend the panels or have them standing. It will help smooth out the response especially in the LF but also in some other regions. You may be able to eliminate or move the dips/peak around 62.5Hz.

Odal3 · « **Reply #2224 on:** 13 Jan 2015, 06:19 am »

Sedge, did you have similar frequency distribution for your EPS panels before you added shellac? Wondering if the shellac can take down the "hump' on the mid. If I remember it correctly, you added it only on the backside in small increments, right?

sedge · « **Reply #2225 on:** 13 Jan 2015, 03:06 pm »

This is a bog standard 1inch thick 2x5ft panel 1ft from panel

This is the same panel 12ft into room

This is same panel 12ft into room with TL s filling in bellow 300hz ,no EQ used !!!

These pics are from my gallery ,as you can see there is no hump on this panel ,but I have seen similar shapes on other panels.
The room will probably have a varied effect in the 90 to 300hz area depending on panel and room ,I would use my TL s to fill in bellow that 300HZ roll off on large and small panels ,this normally stays the same fore all.
I wouldn't use damping to flatten the hump ,the hf can be increased by rigidly gluing the exciter to the panel and helped more by thinning of the panel in front of the exciter area ,the hump in the 80hz area is the panel exciter resonance ,which moves up or down fr depending on panel.
I only used shellac on one 15inch poly panel years back ,it was mostly used on cc and only on the back.
To my ears the shellac helped the sound spread across the panel at the back but seemed to damp it if applied to the front,I carried on using this method with pva and the poly panel.
If you want a better performance in the lower end you could try robs vh panel ,it could look similar to the wood panel in the LF.
STEVE

Seem to have lost the captions under the pics again ,please see gallery fore explanations !!!
Now fixed!!!

Odal3 · « **Reply #2226 on:** 14 Jan 2015, 06:34 am »

I appreciate the info and thanks for all the advice. Today it was no experimenting - just enjoying the music

sedge · « **Reply #2227 on:** 14 Jan 2015, 12:55 pm »

Oral3
Have not done any testing or modify to my new 5mm 24inch x34inh panels since months before Xmas,to much going on,hope to start doing some work on them soon,I hope!!
Do your wood ply panels get hot when playing music at realistic levels ?,this is one of the main reasons I stopped using them.

Expect
Regarding the MTM ,if using two 2ft wide panels per speaker ,your exciters would be about at least 2ft apart,while this might be ok for tectonic filling a hall,for smaller environments I'm not so sure,unless you use small panels,the point I would like to make is that the exciter panel already has a tweeter at its centre,this is why I recommended using the single full range panel first ,if you still wanted to add a tweeter you always have the option to cut the panel in half.
Whatever you decide to do please keep us informed.
Steve

Odal3 · « **Reply #2228 on:** 14 Jan 2015, 04:20 pm »

I have never noticed the panels or exciters getting hot (not even warm) but I haven't really looked for it either. Note that I mount them freely with no spine etc so there is no trapped air.

sedge · « **Reply #2229 on:** 14 Jan 2015, 05:01 pm »

Oral3
I only used one exciter per panel and they could get too hot to touch ,are you still using four exciters ,if so what positions?
Steve

OB_Newbie · « **Reply #2230 on:** 14 Jan 2015, 09:24 pm »

Quote from: Odal3 on 13 Jan 2015, 06:07 am

Since you asked...here are some comparisons between 2.5 x 5 birch panels with thruster exciter (purple) and 2 x 4 XPS panels (green) (re-coated with cheap exciter). Same measurement, just different smoothing. Panels measured at the exact same location, stand and volume settings. It's pretty obvious which area each panel excels. Exciters attached with VHB tape since I didn't have any good glue at home. Birch panels sanded down to 200 and as an experiment I put some diluted pva glue about 5" diameter around the attachment point for the exciter. This and the fine sanding helped smooth out the mids, added the bump between 3-4k, and the two smaller peaks over 10k. The unsanded/treated birch panels barely moved the needle above 8k. Next step is to round and taper the edges a bit more, which I hope will help smooth out the 10k dips. It made a lot of impact on my smaller birch boards. May also re-skin the whole front. If you compare the XPS line in these charts vs the one I posted before (which only had the pva applied to the backside), you can see the difference in HF around 20k Hz.

Since I have little clue what I'm doing when measuring, and my basement is not the best measurement place, one has to be careful to not draw too detailed conclusions from it.
OB_Newbie - play around with dampening on your panels either by tape, Sedge pva/shellac method, cedar rings, moongel or whatever you have at home, where you lean/attach suspension points. It makes a huge difference regardless if you suspend the panels or have them standing. It will help smooth out the response especially in the LF but also in some other regions. You may be able to eliminate or move the dips/peak around 62.5Hz.

Thanks for the measurements Odal. Ply looks pretty good... HF not withstanding. My aging ears would probably be "ok" with it... probably just a touch of lost clarity and transparency I imagine. Nice, relaxed and smooth sounding I'm sure.

I have been thinking of trying a ply panel and possibly mount a small tweeter (like : Dayton Audio ND16FA-6) with a single cap to augment the panel. Just to fill in the HF just a little where the wood panel falls down. Might also add just a touch of needed presence yet still retain the nice full-range DML panel sound! Does anyone know if it has been tried in the past? Many of us do this with OB full-ranger drivers by adding a super tweeter with a very small cap.

As for treatments, I have been using Steve's wonder panel treatment since the beginning. Last panel I did 2 coats on the back and 1 in the front. All of my panels other than the first 2x2 panel have 6 in diameter rounded corners and all edges are rounded with a 3/8" quarter round router bit and hand sanded straight and uniform. I'm super happy with the fidelity and amazed that a piece of foam can sound this good!!!

Still deciding what to build next to test... hmmmmm... when will the fun stop...
1 - Straight small wood panel.
2 - A 2 panel per side "array" with a ply panel on the lower position and XPS as the upper panel. This hopefully would allow the ply panel to augment the XPS in the LF and vise versa on the HF. No idea how they will sound playing together but curious.
3 - The strange combination mentioned above... a panel with a small hole fitted with a traditional tweeter. Rather go with a tweeter that radiates front and back but limited options. PE has some but have very little frame area in the back and would radiate to the sides so not really bipolar.

Probably start with 1 and move down the numbered list if I'm not happy with the results.

Question. For SMALL wood ply panels. How much is the high frequency response extended vs. a large ply panel? Also imagine that the sensitivity is not as good as XPS but fairly close given the smaller panel?!?

Odal3 · « **Reply #2231 on:** 14 Jan 2015, 10:19 pm »

How small? For a 4 x 2 panel with a 1/4 thickness you need either 4 low watt exciters (I have the 5 watt ones) or1 of the new high power exciters to sound OK (but keep in mind several exciters may affects the HF). I havent tried anything in between. I use a small TPA3116 amp to drive them and they play loud enough for me. The charts shows the diff in sensitivity: the xps panel has one 5 w exciter and the larger birch panel has one 40 w exciter. They show about the same db level around 100hz and the xps panel plays about 10 db louder from 200hz to 2k.

Edge treatment (maybe also front and back too???) and how the exciters are attached seems to affect the HF more than size at least when comparing 4x2 panels vs 5 x 2.5

Looking forward to hear about your new projects. The one thing that makes this so rewarding is that it is so easy to experiment and then immediately knowing the result.

I don't like too forward sounding speakers either since it is fatiguing to my ears after a while. I just need the birch boards to go little higher and I will be happy. As of now, I'm slightly missing some of the "airy" sound

OB_Newbie · « **Reply #2232 on:** 15 Jan 2015, 12:18 am »

Quote from: Odal3 on 14 Jan 2015, 10:19 pm

How small?

I'm thinking my typical small panel 24" x 34" like Sedges. I'm thinking at that size 1/8" might work?!?

Quote

The one thing that makes this so rewarding is that it is so easy to experiment and then immediately knowing the result.

Amen brother!!!!! I've never had so much fun with DIY speakers in my life! Almost instant gratification with these panels!!

I ordered the low FS exciter today. Think they ought to sound better on light-weight XPS than the high FS exciter. We shall see! Gunna get some ply soon to. Really looking forward to hearing a smaller ply panel with the new exciters!

Odal3 · « **Reply #2233 on:** 15 Jan 2015, 06:17 am »

Quote from: sedge on 14 Jan 2015, 05:01 pm

Oral3
I only used one exciter per panel and they could get too hot to touch ,are you still using four exciters ,if so what positions?
Steve

My new panels only have 1 exciter on monacore pos 1 (only one exciter wad on the measured panels). My old 2x4 birch panels have 4. One with monacor and one as the panel in my gallery. When measuring the ones with 4 I see dips in the mid , but they still sound good.
btw: I noticed that you and OB measured at one foot so I redid my measurements with the mic closer. This extended the HF much higher.

sedge · « **Reply #2234 on:** 15 Jan 2015, 12:07 pm »

Oral3
The cancellation waves moving through the panel is one of reasons why I don't use multiple exciters.
If you hold the Mic close to the panel and wave it back and fourth across the panel and exciter you will see the wave move up and down the fr response.
I don't remember the hf rolling off on my 3mm ply ,if anything I seem to remember a large hump in the 10 to 20k area but otherwise a fairly smooth response,but a smooth response does not automatically mean a great sounding speaker.
Steve

mightym · « **Reply #2235 on:** 16 Jan 2015, 10:56 am »

This is hard for me, I lost my own father last summer.

I received the following E-Mail this morning from Darren Zygadlo, Robert's son, I am referring to the OP here Zygadr.

This came through a Google group we were both members of:
------------
Hello all,

I am Robert's son Darren. I am very sad to announce the sudden passing of my father on January 11 2015.

I know he spoke to you all about his passion for HIFI.

Please know he will be missed dearly.
------------
I thought this group ought to know too. I spent a number of hours tidying up my own fathers forum relationships after he passed, it wasn't easy for me, and I feel for Darren. I will miss Roberts enthusiasm, and infectious interest in this topics discussion.

John

sedge · « **Reply #2236 on:** 16 Jan 2015, 12:58 pm »

John
Thank you very much for informing us of Robs passing which I read with shock and sadness ,as you said his passion and enthusiasm will be sorely missed .
Steve

OB_Newbie · « **Reply #2237 on:** 16 Jan 2015, 03:18 pm »

Thank you for letting us know John. I did not spend the same amount of time on this thread like you guys but am terribly saddened by this news. We are bound by a like interest and passion and he will be sorely missed by one and all.

Thoughts and prayers go out to his entire family.

RIP Rob. Thank you for introducing me to these silly and absolutely amazing panels and for all the help and guidance you provided me and many others over the years. THANK YOU!!!

Richard

j gale · « **Reply #2238 on:** 16 Jan 2015, 04:12 pm »

I am shocked too and saddened by the news about Rob. We have lost so many recently that inhabited the various audio forums. I guess proof that the majority of those who fell in love with and pursued the experience of being able to listen to recorded music that is as moving as live music, are a privileged generation. Lots of remarks about ageing ears. Rob's enthusiam and sometimes frustration kept this discussion going.I will miss that. I hope that there is another with the passion to keep it going. Thank you Rob for such a good time. Jim

Odal3 · « **Reply #2239 on:** 17 Jan 2015, 02:06 am »

That is sad news. Rob and his passion for audio and our beloved panels will be more than missed. My thought goes out to his family.
Will listen to my Z Panels tonight and be grateful how Rob inspired me and many others to be part of this great community. And as Jim said, thank you Rob for such a good time.

Jonas