Hello JohnoG,
The first difference I see is in the case of an exciter, the volume at the rear of the membrane in the voice coil area is not sealed. In the exciters I use (Dayton DAEX25FHE), there is a small hole at the axis but the main path goes to the internal end of the voice coil to go out by the external side and through the spider. It is this path in my opinion that generates the 2-3k peak.
@xsuper9988
Hi xsuper
Here is a quick test from today.
Red : DAEX25FSE-4 with a small rectangular piece of low density EPS (130x175mm, 5mm thick, row = no coating).
Green : the exciter alone (no membrane)
This EPS is not a good candidate for a real DML but it helps while doing some quick test. What is relevant it is the level it reaches showing what could give a good efficiency membrane.
Hi xsuper
Here is a quick test from today.
Red : DAEX25FSE-4 with a small rectangular piece of low density EPS (130x175mm, 5mm thick, row = no coating).
Green : the exciter alone (no membrane)
This EPS is not a good candidate for a real DML but it helps while doing some quick test. What is relevant it is the level it reaches showing what could give a good efficiency membrane.
This exciter has a quite large spider (voice coil 25mm, external diameter about 50mm). It is probably the reason of the emissions.
To see with exciters with an other design (ie metal suspension) what happens. By the way, is this emission a problem when a membrane is in front?
Thanks a lot for your help and testing
Is the Exciter model "DAEX25FHE-4"?
I found that it is highly efficient after 15K in free state
Then EPS is small and thin panel seems to be only up to 7K
I was originally optimistic about "DAEX25FHE-4"
But it seems that DML is not so simple in high frequency~
If I want more than 10K to have good results
The material of the panel seems to need more research
Maybe I have to look for more high-frequency test results?
DAEX25FHE-4 Framed High Efficiency 25mm Exciter
Dayton Audio DAEX25FHE-4 Specification Sheet
Can you record a video (Youtube, FB)?
Curious... what's going on here?
yes DAEX25FHE-4 Typo!
don't conclude about HF with the material in this test (simple small sheet of raw EPS used to give an idea of SPL with membrane compare to without).
Here is a picture of the exciter used.
The brown part all around the voice coil (transparent plastic) is the spider. It is glued to voice coil at its inner diameter (25mm, moving), to the exciter frame at the outer diameter (50mm, not moving)
Yes
I know
so i reply
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- =-=-=-=-=
I was originally optimistic about "DAEX25FHE-4"
But it seems that DML is not so simple in high frequency~
If I want more than 10K to have good results
The material of the panel seems to need more research
Maybe I have to look for more high-frequency test results?
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- =-=-=-=-=
Or is my English statement wrong?
i should say
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- =-=-=-=-=
But it seems that DML is not so easy to get good high frequency!?
Maybe I need to spend more time collecting data and testing?
Originally, I thought that I would have a good performance immediately after switching to "DAEX25FHE-4".
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- =-=-=-=-=
But it seems to be similar to the principle of the tweeter
Does it seem to only be able to find "hard", "thin", "light", "small"???
Can it have more efficient and high-quality high frequency by going this way???
It is estimated that my future data collection and testing may still need a lot
Thanks again for your data and sharing
Sorry for my misexpression
I mean this noise~
Can you record video (Youtube, FB)?
Thank you very much
Hi Christian.
Motor noise affects all cone drivers with coils.
Exciters are no different.
These are the areas that will probably produce noise.
1. if not securely mounted the terminals will put the exciter out of balance on excessive low frequency movements .
2. The breath hole can cause whistling noises caused by the coil former cavity.
3. The breathing hole cavity at the back of the spider will obviously produce noise.
4. The spider at the front will vibrate out of control producing out of phase noises.
5 .this I have gone on about for a very long time.
You have the cavity in the area behind the panel and magnet and former.
This acts as a cavity resonance similar to a bass reflex port.
You also have another problem within the coil area panel surface.
The hf from the coil former and foot is fired inwards to the centre of the coil.
This causes peaks and cancellations, and distortions.
This can be very painful in the 10k area if not sorted.
6 . The lead out wires can also vibrate too much, or be too tight.
They must not touch the spider or they will buzz.
Large low frequency movements will cause problems with all these points.
Best not to go there.
These problems will change depending on panel materials chosen.
EPS for instance will only need the exciter to move a fraction to produce a room filling sound.
ply for instance will need the exciter to put a lot of pressure (pounding) on the panel, probably causing the former to buckle ( 7.).
Just thought of the nr 7 😊
I would have cut off the grey eps from the coil in the picture, but I want to glue it back into position.
I dropped the panel 🫣
Steve.
Motor noise affects all cone drivers with coils.
Exciters are no different.
These are the areas that will probably produce noise.
1. if not securely mounted the terminals will put the exciter out of balance on excessive low frequency movements .
2. The breath hole can cause whistling noises caused by the coil former cavity.
3. The breathing hole cavity at the back of the spider will obviously produce noise.
4. The spider at the front will vibrate out of control producing out of phase noises.
5 .this I have gone on about for a very long time.
You have the cavity in the area behind the panel and magnet and former.
This acts as a cavity resonance similar to a bass reflex port.
You also have another problem within the coil area panel surface.
The hf from the coil former and foot is fired inwards to the centre of the coil.
This causes peaks and cancellations, and distortions.
This can be very painful in the 10k area if not sorted.
6 . The lead out wires can also vibrate too much, or be too tight.
They must not touch the spider or they will buzz.
Large low frequency movements will cause problems with all these points.
Best not to go there.
These problems will change depending on panel materials chosen.
EPS for instance will only need the exciter to move a fraction to produce a room filling sound.
ply for instance will need the exciter to put a lot of pressure (pounding) on the panel, probably causing the former to buckle ( 7.).
Just thought of the nr 7 😊
I would have cut off the grey eps from the coil in the picture, but I want to glue it back into position.
I dropped the panel 🫣
Steve.
Attachments
Hi Steve
This problem seems to be most manifested by FR (full frequency cone speakers)
This problem seems to occur when FR uses too much EQ adjustment
Because many FR players use one speaker (one coil) for all frequency bands
So what I suspected before should be right?
One coil is responsible for too much bandwidth and there will be "coil sound" (noise)
Am I right?
Thank you so much for sharing
Hi jaxboy.
When you first mentioned your problem with frequencies above 8k ,I reduced the frequency on my system to 8k using my dsp.
This was to give me an idea of what you could hear.
I was surprised at how much I could hear .
You could hear the passion and pain in the opera clip I posted , so I should not have been surprised 🙂
It makes me feel good that I can loose so much of my hearing and still enjoy the music.
As for the squealing noise above 8k.
What happens if you blocked the hf above 8k, would this stop the squealing?
Steve.
This "coil sound" (noise) seems to be "distorted sound" right?
Hi-Fi Full Range speakers playing complex music
https://www.diyaudio.com/community/threads/hi-fi-full-range-speakers-playing-complex-music.234678/
Steve,
I don't hear any squealing above 8K. What I was trying to say was that anything above 8K to me would be non-musical and be heard as just a very high-pitched squeal if I were able to hear that high, which I am not. What opera piece? I'd love to hear it, if you could post it again, or at least tell me where you posted it. That's one of my favorite music types. It's good to have you back on here!
I don't hear any squealing above 8K. What I was trying to say was that anything above 8K to me would be non-musical and be heard as just a very high-pitched squeal if I were able to hear that high, which I am not. What opera piece? I'd love to hear it, if you could post it again, or at least tell me where you posted it. That's one of my favorite music types. It's good to have you back on here!
"DML is not so simple in HF" : well... to go up to 5k is not really a challenge with classic exciters, up to 10k depending on the material. I observed that the HF in my test set up (using standard douple side tape) is generally not as extended than in the 2 pairs I have (plywood with original 3M tape), canvas panel with epoxy glue.