[OB_Newbie]

Its been longer than I expected but I finally got around to measuring two 24x24x1 XPS panels.  One with shellac and one without. The measurements don't really look that different, but the shellac version does sound less "fuzzy" (as someone else has described it). I was going to play with the dimensions next but since people insist PVA is better than shellac, I think I will try that first.

This freq. response looks very odd to me.  To much bass. smoooooth mid and too rolled off highs.  What are you using to suspend the panels?   What about distance and position of mic in regard to panel?  Are the panels off the ground, etc?

Just curious and looking for an explaination for the response.

[sedge]

I agree with OB,something is not right with this plot ,you seem to have at least a 10db boost in the LF and at least a 10db cut above the 4k mark  a few posts ago I showed the fr plot of one of my bog standard 1inch panels at 12ft,the fr should be pretty flat from about 300hz to 10k,near field the hf and LF would improve.
Steve

[dbishopbliss]

I am measuring a single panel, 1 meter away (3 ft, 3in) with the mic pointed at the center of the panel. 

The panel is resting in a 1x3 frame on some sponge pieces at the bottom and some fabric at the top to keep it from falling out. The panel does not touch the sides of the frame. The frame is 72" high and 26" wide.  The frame has a brace at 32" and 58".  The frame is 4 feet off the back wall and is about 8 feet from the side walls.

It looks sort of like this:

+-------------+
|             |
|             |
+-------------+
|             |
|    PANEL    |
|    IS       |
|    HERE     |
|             |
+-------------+
|             |
|             |
|             |
|             |
+-------------+



Also, I do have smoothing on the plots.  It appears to be different (more) than the plots I posted earlier, but the overall trend is the same... it starts to roll off around 5K.

[sedge]

Dbishopblis
There is ,I believe,something very wrong with this fr plot,I have been trying to rack my brain to think of reasons for such a poor HF response,even foamcore has a better response than this!,if you are sure the exciter is getting the full flat un_equalised signal maybe you could measure the response at 1inch in front of the exciter   area to see what the exciter is actually putting out.
Shellac has not over damped the panel though it starts to roll off at 4k,the raw panel struggles to get to 5k.
I noticed that on you plot on page 122 that your raw panel response has a peak at about 5.5k and then rolls off ,so your earlier raw panel plot had e better hf response ,if you are using tape to stick the exciter to the panel I would check that the tape isn't coming away from the panel,when I used to use tape to stick the exciter to the panel ,I always new when it was about to fall off because the hf above about 10k would start to roll off rapidly,even before rattling could be heard,the same could happen even if glued .
Does the foot of your exciter unscrew ,if so check that it is tight.
Even if the panel was a very low quality (with lots of holes in the surface)I would still expect a much a better response than this.
That is all I can think of at the moment,hope this helps sort things out,but if not maybe someone else has a better idea.good luck.
Steve

[dbishopbliss]

I'm using DAEX32U-4 as my exciters.  I am using the tape that comes with them to mount to the board, no extra glue or anything.  I will check the tape, but since both exciters have similar responses, perhaps it is just a bad combination. I will measure 1" away and at the listening position as well to see if things change. 

I don't think it is my measurement setup (REW, with a calibrated Mic from PE).  Especially since the measurement of the metronome is what I expect.  I have a Jordan with a Ribbon tweeter I will measure as well just to be sure. 

[snerdly]

So after about a week of listening I'm very impressed with  the 2x2 panels.....if there be an easy way to detach and reattach the exciters then experimenting could move forward much quicker.I'm wondering if the skin(glue,whatever) I  wonder if the harder the skin the better? I need to get a large panel cut up so I can experiment more.I can see myself falling into a never ending research.

[dbishopbliss]

Shellac is one of the hardest finishes (don't remember where I read that). My glue is drying now so I can compare it to shellac finish soon.

By the way, do people sand AFTER the glue dries? I sanded the skin off before applying the glue, but I was wondering if people sand again.

[OB_Newbie]

Shellac is one of the hardest finishes (don't remember where I read that). My glue is drying now so I can compare it to shellac finish soon.

By the way, do people sand AFTER the glue dries? I sanded the skin off before applying the glue, but I was wondering if people sand again.

The process is to completely sand off the XPS skin, treat with glue:water, I do 2 coats front and back using a drier to speed the drying process.  I just hand sand where the exciter will be placed just to give s smooth surface to attach to.

[sedge]

Dbishopblis
I don't know how hard shellac eventually becomes,the drying time is very slow even when using a hair dryer,I would describe it more as ageing,after a few months it still sounds too heavy to me,give it 10 years and I might change my mind.
As for the frequency plots,I have looked at some of Odal3's plots in his gallery,in the hf they look a little too similar to yours,so unless we can come up with some better plots that give a good response up to at least 10k I would start to suspect the type of exciter being used.
Looking on parts express site ,the photographs show the detachable foot(not a good idea for HF)you can also see what looks like a second metal spring suspension behind the plastic outer,these things are all adding mass to the coil and a lot of plastic between the coil and the panel,this  is the only reason at the moment I can think of the poor fr plots .
the beauty of the lighter exciters is that the coil is glued as close to the panel surface as possible .also with the extra weight and extra power in the LF,consideration has to be given to the structural integrity of eps,especially if you boost with eq ,it can take only so much before tearing apart in the exciter area,eventually.
Hopefully good fr plots will prove this wrong,but I would still have my suspicions with this type of exciter.
Steve

[sedge]

Dbishopblis
Could we also have the plot with the response down to 20hz ,just curious whether the two humps in the lower mid range are the ones usually seen bellow the 100hz mark with the smaller exciters.
It's always best to see the whole picture even if your not using this area of the frequency response.
If anyone else has new good quality plots could you please post them,if it's not too much trouble as this would be a great help In trying to sort the problem.
Thanks.
Steve

[OB_Newbie]

Shellac is one of the hardest finishes (don't remember where I read that). My glue is drying now so I can compare it to shellac finish soon.

By the way, do people sand AFTER the glue dries? I sanded the skin off before applying the glue, but I was wondering if people sand again.

Hows it coming along with the PVA:water treated panels dbishopbliss?  Curious how things are going and how they sound compared to shellac!?   

[dbishopbliss]

My work schedule has suddenly taken over my life requiring 14 hour days so I haven't had time to do measurements, etc. 

That said, the PVA/H2O panel is noticeably quieter than the shellac panel.  At the same time, it does seem smoother than the shellac, but I'm not sure if that is because of the difference in volume or the treatments.  Also, I am noticing a buzzing coming from the PVA/H2O panel.  At first I thought it was the frame but I've swapped frames and played with the mounting and the buzz is still there so I think I will try another exciter when I have time.  Perhaps that will fix the volume issue as well.

[Nickolay V]

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 ?

[TXATC]

Howdy all! Back from the nowhere zone. Unfortunately I haven't finished out the home theater yet, broken tools and family obligations and whatnot. I did however have time to let my neighbor have a listen to my front mains and center.

He is the sound tech for a well known Christian comedian. He is responsible for stage and studio sound. He sat there for about an hour just running through his reference playlist on my speakers. He said he couldn't believe how fast they were. Also said that his reference in the studio were $700 apiece and placed about 2 feet from either side of his head. He wanted to stay and listen longer but his wife told him they had to go lol. Kept saying that they were every bit as good as what he used in the studio without the fatigue. He said he would have no problem listening to them for hours.

Anywho. Tools are repaired and I will be completing the HT setup this weekend. Hopefully my suspension idea(Don't remember if I mentioned it earlier or not) will pan out. I will let you all know how it goes as soon as I am finished. Good to see this is still going. Keep on keepin on!

Semper Fi!
Tex

[oldschoolVlad]

My congrats, TXATC! Just one question - whats the type of your pink panther XPS board? There must be something like this marked on the board : FOAMULAR® 250. Just wonder what are the properties of that XPS to get something similar.

[sedge]

as a matter of interest ,I thought some people might like to see the response of different types of panel, so here is the fr response of a 6ft x2ftx1/8th inch thick ply wood panel at a distance of 2ft in front of the exciter, the exciter is stuck on with tape(for a short time anyway)with no foot , so the coil is directly mounted to the panel.



this pic is the same 2ft distance from the exciter but from the side(panel rotated not mic) I left the peek hold of the previous pic for reference .
as can be seen the hf goes higher (I was holding the mic while trying to take the pic and the mic must have moved off a bit but the peak hold shows the response ) while the rest of the fr drops off as expected .


and same as before from the exciter side for completeness (panel rotated) this is a good full range panel but a more powerful exciter is needed than my 10 watt exciters.



this panel radiates hf in all directions , I presume the hf is louder from the side because the edge of the panel is 1ft closer to the mic?
hope this is of interest to someone.
steve
 

[Odal3]

Thanks for sharing. I don't know why,  but I can't get the HF as you and OBnewbie reports at a distant. It doesn't matter if foam with glue, ply or powerful large/smaller exciters  or large,small panels. It gets extended to the 10k plus range at very close mic distance but then drops quickly when moving back the mic a couple of feet. Drop is about 10 db when smoothed (but with peak spikes higher). The only thing I can think of is HF cancellation. Still sound great - maybe I should stop measuring.

[sedge]

odal3
this is a pic of the 12ftx2ftx1/8th inch ply panel at a distance of 12ft, the hf holds up well , I also moved the mic 1ft to the left and 1ft to the right this filled the dip in the lower midrange but didn't alter the fr much above 250 hz


this is the response of a 5mm x86cmx60cm poly type test panel at 2ft .



this is the same panel at 12ft the hf has reduced ,but when I move the mic to the left and right the hf stays the same, I moved the mic all the way to the wall and the response above 300hz stayed almost the same but filled in the lower mid again,room problems don't seem to have much effect on fr above the lower midrange? whats left of my hearing tells me this panel has good hf but the mic says no?is this as you say room cancellation that the mono  mic is picking up but that my ears have no problem sorting out?


this is a bog standard 1inch x2ftx6ft eps panel at 12ft with some help from my tls up to about 300hz,  I have sanded it but not done anything else so far, i moved the mic as before left and right ,not much changes in the upper part of the fr plot again but once again the placing of the mic changes the response in the lower midrange ,the plywood panel does not suffer from this problem as much? I would describe this as fast and lively panel and would not be keen on using EQ to increase this,the sound is quite natural as is.but I will try my mods on this panel to see if I can bring it out naturally .


 steve

[Odal3]

Good to see you're still at it!!! 
And many thanks for posting the additional plots - the last ones is pretty much what I get too. Sometimes slightly more extended, or other times slightly less.

The not as wide panels I built for the living room sounds OK, but I miss the bass from the larger panels. Hanging them on the wall didn't help with the bass either, but that's OK since they even got my mother in law's approval.
I have started to experiment with very small panels for "tweeter" duties, or putting a second small exciter at one edge but haven't had a chance to do any measurements yet.

[Odal3]

@Oldschoolvlad - owens cornering is what we in the US have used. See for example here: http://insulation.owenscorning.com/homeowners/renovation/products/insulpink/