A Study of DML's as a Full Range Speaker

[spedge]

This is the cheapest eps I have found so far in the uk.
https://ecclestons.com/product/handipack-polystyrene-sheet-1200mm-x-600mm/
How many are in the pack depends on thickness, but £30 for 24sheets 2ftx4ft 12mm including delivery is about as good as it gets, even cheaper if you pick it up yourself from Birmingham .
Steve.

 

[spedge]

They do a grey supertherm, but it does not contain graphite, I phoned to check.
Steve.

 

[Leob]

They do a grey supertherm, but it does not contain graphite, I phoned to check.
Steve.

My guess is that the person you spoke to doesn't really have a clue, and is quite sure that all grey EPS contains graphite.
Could they tell you what it contained apart from styrene that results in grey colour and enhanced thermal properties?

 

[spedge]

Leob.
the reason I phoned ,was that none of the information mentioned anything about graphite , which you would have thought would be important.
The person on the phone stated that the eps was graphite in colour, but contained no graphite ?
what can I say ?
Steve.

 

[Leob]

Leob.
the reason I phoned ,was that none of the information mentioned anything about graphite , which you would have thought would be important.
The person on the phone stated that the eps was graphite in colour, but contained no graphite ?
what can I say ?
Steve.

Having worked in retail sales myself, trust me, salespeople cannot be trusted

Regarding using hide glue for fixating the exciters, it is not working out at all. In my first attempt I simply used the same dilution I used for coating the panel. I figured I give it another shot, but this time with normal strength. Turns out that doesn't work either. Hide glue just will not bond to the plastic on the exciter, and they fell off after a couple of days.

 

[spedge]

Leob.
I have used pva to glue my exciters on all of my panels including aluminium , some have been firmly stuck for 10years.
Although I am happy to try all sorts of panel materials and glue, eps and pva are my personal favourite, and have been for over 10years now.
I have not made any comparisons but I think the low quality crate ply might come in as a close second ?
The recordings don't really do the sound any justice , but give an impression of the general sound available.
So far the pva is still stuck to the polypropylene, I have given it a few tuggs now and again to check it is still firm.
But two good signs it is holding well is no buzzing and a good extended frequency response.
Steve.

 

[homeswinghome]

I know, but I don't
I tested same exciters using same tape to mount them on my Polycarbonate plates, and have plenty of response above 10k, so I can only conclude that the plates are the issue. It is the same on the regular EPS plates from the same supplier as well, to not a difference with the GPS specifically.

I would be curious to try the building supply GPS to see how it differs to the plates I have. Like I said in previous posts, the GPS is sounding tighter and less "chorusey" than the regular EPS. The EPS can add a nice shimmer to some material, but the GPS seems to give a more accurate sound.
But I have decided to invest in vacuum bagging now to make carbon composite plates, so wont do more styrofoam experiments for now at least.

+ @spedge
Hello Leob, hello Steve,
Steve, this is an "old" question. You reach 20k with EPS. Leob can't and with the few tests I did with EPS I can't go to 20k.
Below 2 EPS I tested :

• a 175x130mm 7mm thick not coated from a packaging (quite dense) - red
• a 600x800mm 20mm thick 15kg/m³ PVA coated - green.

Where is the difference? with what you do?

@Leob : by the way, have you solved the HF question you have had previously?

Christian

 

[Leob]

@Leob : by the way, have you solved the HF question you have had previously?

I did test with same exciters mounted with the same tape on polycarbonate plates, and didn't get the HF drop. Like Steve said though, since the polycarbonate might have an exaggerated HF response, it is still not certain if it is the plates or elsewhere in the chain.
Plan is to make some carbon/nomex composite plates next and see how those fare as well.

 

[homeswinghome]

I did test with same exciters mounted with the same tape on polycarbonate plates, and didn't get the HF drop. Like Steve said though, since the polycarbonate might have an exaggerated HF response, it is still not certain if it is the plates or elsewhere in the chain.
Plan is to make some carbon/nomex composite plates next and see how those fare as well.

Would it be in the use of a tape (what I do also for quick test) vs PVA use? I have better HF results with the original tape (3M VHB) or epoxy glue. Not tested PVA at the exciter. This was already mentioned as a possibility some posts ago but I haven't seen a test about it... This is perhaps something to test. I am intrigued by the PVA gluing which seems works even on polypropylene.

 

[Leob]

Would it be in the use of a tape (what I do also for quick test) vs PVA use? I have better HF results with the original tape (3M VHB) or epoxy glue. Not tested PVA at the exciter. This was already mentioned as a possibility some posts ago but I haven't seen a test about it... This is perhaps something to test. I am intrigued by the PVA gluing which seems works even on polypropylene.

Had the same issue with the original tape and have tried a few different glues, but no major difference.

 

[spedge]

Hi Christian.
It would seem I can only guarantee the hf performance with my exciter ?
The green 20mm eps line starts a downwards trend at just over 2k, and a smooth roll off from about 3.5k to 10db down at 10k ?
with my exciter , neat 15kg/m3 has no problems until after about 10k ,which can be sorted.
If you are using tape , this is also reducing the hf above 10k .
I presume the microphone was at least 1m distance ? Because of the drop below 300hz ?
The red 7mm line is all over the place, this does have a peak at 10k, but is still well down .
I have no suggestions for these response curves, as they are already beyond my help.
If I glue my exciters on in the morning using pva , with a little help from a hair dryer, they can be tested that evening.
But the hf will not reach its full potential until at least a few days later !
This is easily measured.
Is the frequency response of the green 20mm line any better at 50mm in front of the exciter ?
Steve.

 

[homeswinghome]

Hi Christian.
It would seem I can only guarantee the hf performance with my exciter ?
The green 20mm eps line starts a downwards trend at just over 2k, and a smooth roll off from about 3.5k to 10db down at 10k ?
with my exciter , neat 15kg/m3 has no problems until after about 10k ,which can be sorted.
If you are using tape , this is also reducing the hf above 10k .
I presume the microphone was at least 1m distance ? Because of the drop below 300hz ?
The red 7mm line is all over the place, this does have a peak at 10k, but is still well down .
I have no suggestions for these response curves, as they are already beyond my help.
If I glue my exciters on in the morning using pva , with a little help from a hair dryer, they can be tested that evening.
But the hf will not reach its full potential until at least a few days later !
This is easily measured.
Is the frequency response of the green 20mm line any better at 50mm in front of the exciter ?
Steve.

Hi Steve
Yes the mic was at 1m for the red curve and 1.5m for the green.
Unfortunately I have no record at close distance

 

[spedge]

Leob.
Your measurements don't make much sense to me ?
Bog standard 25mm eps should be pretty flat to about 10k
So 10db down by 2k and 30db down by 10k ?
You can't be measuring correctly or there is something wrong with the exciter of mounting ?
your other measurements also have similar heavy roll off also ?
This cannot be a coincidence
they should not have similar measurements.
Steve.

Christian.
just accidentally found this post while trying unsuccessfully to find my 10mm low grade eps plots.
we seem to have been hear before with other measurements .
Maybe we need to find the exciters that do reach 20k or so, and name and shame those that don't even get close ?
Steve.

 

[Eucyblues99]

Christian.
just accidentally found this post while trying unsuccessfully to find my 10mm low grade eps plots.
we seem to have been hear before with other measurements .
Maybe we need to find the exciters that do reach 20k or so, and name and shame those that don't even get close ?
Steve.

Could the problem be that EPS is too soft through the thickness to hit the HF - have you compared it to XPS?
Eucy

 

[spedge]

Eucy.
I have posted many plots over the years showing the good hf response that EPS can have if the exciter is capable.
Even my very soft EPS low grade panel , when coated in pva reaches 20k.
I took measurements of the uncoated panel as well for comparisons.
I think the uncoated panel struggled to reach 8k without the coating ?
If you can get the EPS panel to reach about 10k with its usual 10k peak and dip afterwards , there are easy ways to sort this out.
Steve.

 

[spedge]

Just found post 5168 ,on page 259 which has a plot of my low grade(soft) EPS panel with a thin pva coating.
Steve.

 

[spedge]

Sarath.
At the moment I am in the middle of testing the eps panels.
The first picture is the low grade panel drying near the fire after coating with pva.
The second picture is them playing before coating.
The third picture is the response of the 70grade eps panel before doing anything to it.
The fourth picture is the low grade panel before doing anything to it.
Both at about 30cm.
The peak before rolling off with the low grade is at about 8k.
And the peak before rolling off with the 70grade is about the 13k mark.
I will explain the difference in sound and performance at another time, as I have noticed certain things as I've moved along.
Steve.

just found the post for the low grade and the 70grade uncoated panels, things are easily lost in this forum !
Steve.

 

[JohnnoG]

Hi Steve
The new sample boards are now awaiting courier pickup.
I hope they are able to deliver a good account for themselves.

 

[Peter M.]

Hide glue will not bond to plastic or metal, or very weakly at best. It is great for glueing wood and making canvas on a frame more taut. It is my favorite wood glue.
It bonds strongly to glass, so much so that it can pull the surface of the glass clean off as it shrinks when drying.
It shrinks a LOT as it dries, and will easily turn any unsupported thin flat panel it bonds to into to the shape of a potato chip.

 

[homeswinghome]

Christian.
just accidentally found this post while trying unsuccessfully to find my 10mm low grade eps plots.
we seem to have been hear before with other measurements .
Maybe we need to find the exciters that do reach 20k or so, and name and shame those that don't even get close ?
Steve.

Hi Steve,
To have more criteria for the exciter choice would help but up to now I have no real way... My basic criterias are high BL, low mass, low inductance. Previous posts shown the role of the inductance. My tests around the voice coil mass haven't shown it is very critical.
When I come back to the comparison of specifications :

• The TEAX25C10-8/HS you use (see post #3433)
• The Dayton Audio DAEX25FHE4 commonly used

The TEAX has a lower mass (1g vs 1.6g) but no evidence it is an advantage
Their inductances are similar at 0.1mH... but the TEAX is 8Ohms which means the cut off frequency is higher. This might be a good point.

The problem is the TEAX or HIAX seems not easy to find. Do you know some suppliers or equivalences?

Extract of the specifications