I thought I'd show how big the magnet on the hdn8 is and how flimsy the the housing is .
It splits apart very easily even when you don't want it to😫
You can imagine how the plastic shell would vibrate noisily especially when used it on a panel.
It seems to work better on a stud wall, remarkably.
Steve.
It splits apart very easily even when you don't want it to😫
You can imagine how the plastic shell would vibrate noisily especially when used it on a panel.
It seems to work better on a stud wall, remarkably.
Steve.
Attachments
Hello
The specification file of the PUI ASX05404-HD-R is light and more "mechanical" than "electro-mechanical". Does somebody have information like the Bl (force factor), voice coil mass, inductance?... by PUI documentation or measurements?
Christian
Or you may follow the Dayton DAEX58FP, Dayton DAEX32QMB-4 some info in their spec? The driver itself "should be" idential.
https://www.daytonaudio.com/images/resources/295-210--dayton-audio-daex58fp-specifications.pdf
I never tried 5mm EPS.
I found 10mm a little too thin and cause some kind of "echo" on human voice speaking. So I prevent to order board thinner then 10mm.
I screwed on a block of wood to my hdn8 and held it onto the dry wall .
Not a bad response for a wall 😀
Anything below 40hz is just road noise and it rolls off at 10k.
The microphone was in the usual place behind my seating position.
I found an empty wall space about 1.5m from the microphone .
It sounded good too, but I was pressing the exciter block up against the wall, so could not get far enough away from the exciter to make a good comparison.
I would hope a better solid mounting would improve things a little ?
Steve.
Not a bad response for a wall 😀
Anything below 40hz is just road noise and it rolls off at 10k.
The microphone was in the usual place behind my seating position.
I found an empty wall space about 1.5m from the microphone .
It sounded good too, but I was pressing the exciter block up against the wall, so could not get far enough away from the exciter to make a good comparison.
I would hope a better solid mounting would improve things a little ?
Steve.
Attachments
Interesting. I first heard the “echo” you speak of with 25 mm XPS, and assumed it was because it was too thick! But then I tried thinner (12 and 5 mm) XPS and it was similar. Tried coating it with PVA to no avail. Tried EPS too (25 mm) and still heard the echo. I do wish I could find XPS or EPS that doesn’t echo but no luck for me yet with the ps foams readily available here.
Like for you, the echo I get is most apparent for voices. It sounds a little like the singer is at the bottom of a deep well.
Eric
Try this selective damping and see if it works:
Get hold of some very thin sticky felt...
Stuff used for the bottom of drawers..
Play some news reports or similar
Feel around the panel for the most active areas...I found 2... One above and one below the exciter
Cut patches of the felt and place them on the active areas at the back of the panel
Worked for me on cedar....
Worth a try
Eucy
I think the XPS "echo" you're saying maybe not quite the same thing as what I said on the thin EPS.
I will say the XPS echo is a kind of "honky" sound. It's relate to FR.
The thin board echo is actually an echo. When you playing a speaking voice then suddenly pause it. You'll hear the "decay". It's relate to impulse I think?
Higher density and heavy exciter used will make it more serious.
I don't know the science behind this. But my experience told me it's also relate to the panel material and size.
Strange that EPS echo happens on thin board. Not much relate to size. But plywood echo relate to size. Same ply board in 40x60cm have echo (free hanging), if I cut it down to 20x30 the echo will largely decrease.
I'm OK with this echo when playing music. My case is far from your "deep well" level. Just a little wet sounding.
But for movie watching it's quite bothering. Because the room sound is not quite match what I'm seeing.
Hkguy6.
When I used to use large panels, I used to use the pause button to listen to the panel resonance.
I'd play music with loud low frequencies, and when paused you could hear a shmmmm sound as the sounds died away.
When using smaller panels the sound stops instantly, to the ear.
I'm trying to remember, but I think the reason I used to coat my eps panels in vinyl silk ,was to dampen the panel sound.
This worked quite well, but I ended up with a heavy damped panel, which is not what I wanted.
I even tried it on my 1inch 70grade and 5mm xps.
What Eric seems to be talking about sounds like the combination of the 100hz to 300hz suck out problem and the problem of the sound from the back of the panel being blocked by the panel material itself.
This can give the impression that a singer is further back in the room or as some have said in the past, in the next room !
This is why I used to thin my panels in the exciter area, to give a more intimate closer sound to vocals.
Bringing the voices back into the room.
I mentioned this over on NXT RUBBISH years back.
Thinner materials or turning the panel around can improve this.
Very small thin panels don't block the rear sound very much ,which is probably why I like them ?
I have not thinned the graphite panels in the exciter area yet.
But I will at some point do this , not that I have noticed any problems so far ?
But my room is in a pretty bad state at the moment and could be masking this problem?
Steve.
When I used to use large panels, I used to use the pause button to listen to the panel resonance.
I'd play music with loud low frequencies, and when paused you could hear a shmmmm sound as the sounds died away.
When using smaller panels the sound stops instantly, to the ear.
I'm trying to remember, but I think the reason I used to coat my eps panels in vinyl silk ,was to dampen the panel sound.
This worked quite well, but I ended up with a heavy damped panel, which is not what I wanted.
I even tried it on my 1inch 70grade and 5mm xps.
What Eric seems to be talking about sounds like the combination of the 100hz to 300hz suck out problem and the problem of the sound from the back of the panel being blocked by the panel material itself.
This can give the impression that a singer is further back in the room or as some have said in the past, in the next room !
This is why I used to thin my panels in the exciter area, to give a more intimate closer sound to vocals.
Bringing the voices back into the room.
I mentioned this over on NXT RUBBISH years back.
Thinner materials or turning the panel around can improve this.
Very small thin panels don't block the rear sound very much ,which is probably why I like them ?
I have not thinned the graphite panels in the exciter area yet.
But I will at some point do this , not that I have noticed any problems so far ?
But my room is in a pretty bad state at the moment and could be masking this problem?
Steve.
Yesterday I did make a recording of the single 5mm eps coated in vinyl.
It was of large drums and percussion to demonstrate the low end power and sound.
But noticed it sounded a bit thin.
When I played it through my deq it showed that the microphones in my phone roll the frequency off in the low end.
I think my old note 4 was better in the low end?
It is well down below 100hz and stops at about 50hz.
When I use the subs ,I use them to compensate for this roll off.
But not much good if I want to demonstrate the in room low frequency performance of the panel itself.
Steve.
It was of large drums and percussion to demonstrate the low end power and sound.
But noticed it sounded a bit thin.
When I played it through my deq it showed that the microphones in my phone roll the frequency off in the low end.
I think my old note 4 was better in the low end?
It is well down below 100hz and stops at about 50hz.
When I use the subs ,I use them to compensate for this roll off.
But not much good if I want to demonstrate the in room low frequency performance of the panel itself.
Steve.
Hkguy6.
When I first heard the podiums at their first showing in the UK, I preferred the sound from the back of the panels .
I tried the same with my panels, which was fine to start with , but I quickly noticed problems.
The exciter covers the area in front of the exciter area, which not only blocks the sound from this area but also has what I would describe as a phazy sound caused by the exciter coil suspension being very close to the panel surface.
And if the exciter is pushed harder on a heavy panel ,exciter noise is more obvious, it is not hidden behind a panel.
I could measure these destructive frequency variations as well as hear them.
Steve.
When I first heard the podiums at their first showing in the UK, I preferred the sound from the back of the panels .
I tried the same with my panels, which was fine to start with , but I quickly noticed problems.
The exciter covers the area in front of the exciter area, which not only blocks the sound from this area but also has what I would describe as a phazy sound caused by the exciter coil suspension being very close to the panel surface.
And if the exciter is pushed harder on a heavy panel ,exciter noise is more obvious, it is not hidden behind a panel.
I could measure these destructive frequency variations as well as hear them.
Steve.
I made some quick recordings of the hdn8 on a spare patch of wall.
I screwed the exciter into a small piece of wood I had lying around.
Then I had to try and hold it onto the wall, which wasn't easy because of its weight.
So the quality is a bit patchy especially on the second recording.
The arms were failing 🥵
Obviously screwing the exciter into the wall would be much, much better sounding.
But this was to give you all an idea what could be possible.
Even with the bad room noise it still sounds pretty good on the recording, I think.
It definitely sounds better to me in the room.
This is an outside wall, stud wall, so it would be very possible to turn the wall into a speaker
When I get time I will sent the recordings to my computer to zip and send.
Steve.
I screwed the exciter into a small piece of wood I had lying around.
Then I had to try and hold it onto the wall, which wasn't easy because of its weight.
So the quality is a bit patchy especially on the second recording.
The arms were failing 🥵
Obviously screwing the exciter into the wall would be much, much better sounding.
But this was to give you all an idea what could be possible.
Even with the bad room noise it still sounds pretty good on the recording, I think.
It definitely sounds better to me in the room.
This is an outside wall, stud wall, so it would be very possible to turn the wall into a speaker
When I get time I will sent the recordings to my computer to zip and send.
Steve.
Attachments
I am not able to find this measurement for now but I remember from my tests of 25mm XPS some peaks in frequency (300 or 500Hz?) with an important delay (10ms?). It was at my beginning with DML. At this time I was wondering if it was an effect of the room but more possibly it is like if some energy is stored in the panel and released lately. Is it the signature of a too low damping?
A spectrogram with REW should show something.
Christian,
I thought the impulse response would show something very distinctive for the material with the "echo", but I did not see anything. Rather the impulse response was surprisingly similar to that of plywood panels, even though the sound was very different to my ear. Certainly part of that difference is in the overall frequency response, but I think it was more than that, but I don't know exactly what or how to measure/observe it in REW.
Are you saying that you observed a delay for a particular frequency? I don't know how you would measure that. If I recall correctly you were doing some delay measurements some time ago but I do not recall the details.
I think the delay would have to be more than 10 ms to be heard as an echo. From Wiki:
https://en.wikipedia.org/wiki/Precedence_effect
Eric
Hello Eric,
Have you already tried the spectrogram representation in REW?
If not : the spectrogram is like you enter the IR in a bank of filters of different frequencies. One axis if the frequency. The second axis is the time so that you can see the output for a given frequency according to the time. It informs about the time when something occurs which is no possible with a "simple" FFT (FR).
If it can help, have a look on the slide 6 of the attached presentation (a presentation I wrote some months ago to help Cheapvega in the use of REW).
In the slide 6, you can see for example that the maximum at about 120Hz occurs late (time in vertical axis).
Let me know if it is something you use or if you want more support (in the limit of my knowledge of course...).
This kind of analysis is similar to the 1st stage of the hearing mechanism. The cochlea works like a filter bank. It has the sound as input and a multiple of outputs according to the frequency which are sense by neurons. What happens after is more mysterious.
Christian
Good point. I have taken cursory looks at the spectrograms at various times. I don't recall seeing anything particularly different for the echo-y PS compared to ply panels, but I may not really have looked carefully enough, or, more importantly, had any real idea what I was looking for! Thanks for resharing your tutorial. I just re-read that as well as the REW help file. I'll take a closer look at the spectrograms and see if I spot anything interesting. Especially if I can see any difference in character between my PS and plywood panels.
Thanks
Eric
Eric,
I added 2 slides in the tuto so that you have examples of spectrograms :
- 9 : the IR/FR/spectrogram of a perfect pulse (Dirac = only one sample at 1 at t=0, all the other at 0). You will see the maximum of the filter outputs are perfectly aligned at t=0s. The FR is also perfectly flat.
- 10 : the IR/FR/spectrogram of my 3mm plywood panel (outdoor measurement). The peak of level at 400Hz occurs at 1ms so with a little delay. For 100Hz and 50Hz it is even later. The dash line shows the maximum.
In an other place, I still have my XPS board. It might be interesting I make a new measurement with them when I will go back there. This echo phenomena is probably one reason I switch from XPS to PWD (energy stored in the panel and released "too late").
In my list of thinks to too (to long list...) there is investigating the possibility of an EQ that aligns all the peaks (sounds like Rephase tool I guess).
In addition the dirac .wav fil in a zip file. Just unzip it and import in REW as a impulse response in a wave file.
The good question : in all of that what do we hear?...
Christian
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i had not planed on this recording , so forgive the amateur chaos ,but the mic was behind my seating position just over 3m.
i started off speaking near the microphone and walked to inbetween the two panels .
on the left is the graphite eps and on the right is the 4mm proplex.
the eps was turned down about 9db to match volumes.
even though this is very loud the sound is still clean and open sounding , except right near the end when i turned the volume knob up as far as it would go, it was alread up to about 9 so not a lot of difference but that little bit more was enough to distort the amp or panel ?( if only they could go up to 11
).
it was probably the proplex panel as my exciters are pushed to their limits trying to driving them.
even at the back of the room with all my junk in , it still sounds unstressed and clean, with no impression of how loud it is, DML is weird , in a nice way.
both panels are 2ft square , the low end seams quite throng in this recording with no sub.
steve
i started off speaking near the microphone and walked to inbetween the two panels .
on the left is the graphite eps and on the right is the 4mm proplex.
the eps was turned down about 9db to match volumes.
even though this is very loud the sound is still clean and open sounding , except right near the end when i turned the volume knob up as far as it would go, it was alread up to about 9 so not a lot of difference but that little bit more was enough to distort the amp or panel ?( if only they could go up to 11
).it was probably the proplex panel as my exciters are pushed to their limits trying to driving them.
even at the back of the room with all my junk in , it still sounds unstressed and clean, with no impression of how loud it is, DML is weird , in a nice way.
both panels are 2ft square , the low end seams quite throng in this recording with no sub.
steve