No, composite material doesnt say much.
Also what looks like hinge maybe is not hinge and is fixed.
Part nr. for the driver is LF27723.
Attachments
@BurntCoil
Hello Burnt,
Thank you for opening this thread.
Let me introduce my opinion about the characteristics of an exciter for a DML (fully objectionable!) :
Christian
Hello Burnt,
Thank you for opening this thread.
Let me introduce my opinion about the characteristics of an exciter for a DML (fully objectionable!) :
- BL : never too high?
- inductance and voice coil mass : the relation to the panel characteristic is not fully clear to me but I remains in my first opinion that as involved in low pass filter (inductance with the electrical resistance, mass with the panel mechanical impedance), the designs giving the lower values may the right one
- electrical resistance : not convince that 4Ohm is the best target. For PA application may be but for home as we don't have a lack of power why not taking the option of increasing the cut off frequency made with the inductance
- the shape of the interface with the panel. The conventional one is the shape of the coil but is it the best one? Currently, I am in the idea of testing an area small as possible (contact point). The reason is that this area split how the panel works in 2 regions. The region out the contact circle, the region inside. So why not having only one. This is probably not easy with a standard exciter where a coupling part is needed but with a custom exciter... It opens possibilities. In on one of your design, there is a disc : what about the HF extension (no more internal area)
- the design has to be open so that the air around the coil is not trap at the risk of a noisy escape (shared on the main thread following the exciter noise comment from Steve)
- a last (? for now...) idea is the footprint of the exciter (its surface on the rear side) to be small as possible or arrange in the way the rear wave has the same FR as the front wave.
Christian
With my current quick made up one, the former and voice coil section is glued in. With this in mind I could look at how the contact point for excitation effects things on some A4 pieces of foam board and see if there is a noticeable difference
@BurntCoil
I look forward to seeing your build unfold. For now I will be trying a few small things for my design before releasing to my patreon supporters and will come back to it at a later point. Got many many designs in the pipeline so need to keep focus 🙂
- Paul
Thank you Christian, a very thoughtful input.
I agree that BL can not be too high, especially the B component. I want to get a high flux so that I can use fewer turns to tackle the high-end roll off we often see.
I also want as low an inductance and voice coil mass as possible. This is especially challenging when low panel mass with high stiffness is also a requirement for good DML performance.
Despite their similarity to conventional transducers I see exciters as being closer to impulse devices, large displacement is not required from them, and we can increase force applied to the panel per unit area by reducing the contact area. That is one of the reasons I have concerns about the flat coil mounted to the panel in Option 2 which then resulted in Option 3.
There is a direct relationship between the Force F delivered by BL, and the F per unit area delivered by the contact area. I am feeling my way to a mathematical model but my current understanding is incomplete.
I am not completely sure I understand your last point. If you have time to expand I would be grateful but if not don’t worry, you have pointed me at something else to think through.
Many thanks
Burnt
If 3d printing is something you would do, I recall @gomper did some interesting driver manufacturing and custom spider work in this thread - https://www.diyaudio.com/community/threads/creating-a-field-coil-driver-loudspeaker.352790/
Hello Burnt
Happy if it helps you.
The last point is probably of minor importance...
About one year ago, I made a comparison of the IR (front and rear) of a canvas vs an OB with a Visaton FRS8. From the OB, front and rear response are different. I came to the conclusion it is due to the mask made by the magnet, the way the sound has to go around. With an exciter, the rear wave is much closer. So the idea is the exciter not to be an obstacle to the rear sound. For example an exciter of low diameter but of higher depth (not good for your 90° turn DML) rather than a large diameter and low depth.
Christian
Good evening Christian,
Thank you that clarifies your question for me. Yes I see the issue now and have logged it as one to explore,
Many thanks
Burnt.
Thank you that clarifies your question for me. Yes I see the issue now and have logged it as one to explore,
Many thanks
Burnt.
Burntcoil.
Some good ideas already on this new site.
I like the thin spider , which looks similar to the photo I posted a while back ,of an old cone drive unit spider ,possibly from the 1950 ?
I'm not sure if it was made out of thin leather or maybe a form of gasket material.
There were screw mountings, so it was adjustable.
The point I was making about different exciters for different materials and why, ( I will have to do at another time as I am being beckoned away ) .🙄
Steve.
Some good ideas already on this new site.
I like the thin spider , which looks similar to the photo I posted a while back ,of an old cone drive unit spider ,possibly from the 1950 ?
I'm not sure if it was made out of thin leather or maybe a form of gasket material.
There were screw mountings, so it was adjustable.
The point I was making about different exciters for different materials and why, ( I will have to do at another time as I am being beckoned away ) .🙄
Steve.
Hi BurntCoil,
Neat thread - just saw it for first time. I recall I took the cone off of an old 5in driver once and connected the spider and voice coil to a panel and it sounded not too bad. It was very powerful as the magnet was huge compared to most DML exciters. A cheap way to go with off the shelf pistonic drivers you don’t mind pulling the cone off.
Happy Xmas everyone.
Neat thread - just saw it for first time. I recall I took the cone off of an old 5in driver once and connected the spider and voice coil to a panel and it sounded not too bad. It was very powerful as the magnet was huge compared to most DML exciters. A cheap way to go with off the shelf pistonic drivers you don’t mind pulling the cone off.
Happy Xmas everyone.
Hello Burnt,
For the bass, have you already had a look around "infraflex". You will find some links in this post #45.
Christian
I was looking at lowther phase plugs and was thinking, what a good shape it would be for an exciter ?
You could even have one on the front of the panel or even in push pull without bad phasing effects?
If a shaker type it could even go on a wall .
Oh no !
there goes another patent 🤣
Steve 😭
https://community.klipsch.com/index.php?/topic/77981-what-the-hell-is-a-phase-plug/
You could even have one on the front of the panel or even in push pull without bad phasing effects?
If a shaker type it could even go on a wall .
Oh no !
there goes another patent 🤣
Steve 😭
https://community.klipsch.com/index.php?/topic/77981-what-the-hell-is-a-phase-plug/
Hi Christian,
That does look like something worth investigating, thank you!
Burnt
Push-pull operation is certainly worth investigating I agree Steve. Option 2 is a push pull using the field rather than a physical component but the effect of driving both sides of the panel is interesting. Another one on the list.
Burnt
P.S. Patents are very overrated in my view. If you want competitive advantage not publishing the secret of your success is much more effective.