The voice coil cavity is basically a helmholtz resonators, adding extra holes will only change the frequency slightly.
Opening this area up as much as possible to prevent the closed cavity is one option or using a phase plug is another.
The rear hole in the exciter magnet does whistle and I presume the ones in the coil do too.
I notice that the tectonics bmr uses very big holes in the sides of the coil former to open up this area , obviously for this very reason.
I'm sure many cone drivers use the same types of measures.
Some cone drivers use a not so fine mesh over the coil area (it is basically open) to prevent this resonance.
It is a problem that all coil drivers over the years have suffered from, it is not new.
The ten watt exciters are much lighter than the more powerfull exciters, so they use a standard cone type spider.
But over time they will sag if some sort of support is not used.
The support should also stop the exciter wobble from being out of balance because of the lead out wires and lead out mountings .
This can be very damaging on loud low frequencies if not dealt with.
I have had no problems using a rear brace, as long as it does not obstruct or block the sound too much.
Like you , I did not use bracing on my very large eps panels, I just turned them over if the sag became a problem .
I would not use super glue to restrict the coil movement.
Steve.
Steve...I don't recall actually calling it a tweeter ...if I did then I'm a silly canary
And I initially adopted them on my cedar panels before I even thought of using the ply
The ply tests came about by trying small samples of laser ply after having poor results from standard 3mm builders ply..
The poplar ply seemed to perform the best out of about six samples so I bought some. I was pleasantly surprised by how efficient and clean sounding it was.
Back to the dome...the most obvious effect to my ears is a noticeable increase in the clarity of vocals...
It does assist with the hf but I'm too old to hear the difference🤒 Far younger ears than mine have noticed the effect.
And yes, I was more than satisfied with the hf without the dome... But aaahh the clarity boost is great, and it has the same effect on the cedar. As I've said previously, it seems to bring the vocals forward.
Don't I recall you saying something similar about a piece of folded paper???
Eucy
Steve . I'm sure I do but they're buried in a pile of files
It would be easier to set up another test, but honestly, you don't need to measure it as far as the vocal clarity increase is concerned, because even I can HEAR it.👂👂. I'm not even sure how clarity is identified in a fr graph.
The best way is to make two identical panels, put the dome on one, play some mono tracks, switch between the panels and just listen. QED imo.
Cheers
Eucy
I agree with using identical panels as I use this method all the time when testing.
So are we talking about the tin can effect which can cause problems with clarity in the voice coil area?
The dome blocking or damping this problem, but also giving some output?
This is a separate problem from the coil cavity problem.
The paper idea, has to be positioned properly, while watching the frequency response, or it could make things worse .
This only affects the sound from the coil surface area ,not the panel.
your dome could be doing the same sort of thing?
Steve.
Steve... I'm not sure if everyone has exactly the same idea as to what the tin can effect actually sounds like, but if it is a hollow sound then no, it's not that.
When I listen to vocals with no dome, even when they sound ok/normal, I can tell there's wood in the way which to my ears 'just' takes a certain edge of the crispness of the vocals. It stands to reason that 3 or 4 mm of wood in front of the driver will have some dampening effect.
But it's also not just with wood. I noticed exactly the same thing with the Corflute.
Put the dome in place and the zing is there. It doesn't make it harsh, just really makes the panel thickness disappear in both the wood and Corflute panels
Eucy
Last edited:
Digging a bit on the web leads me to this article : Identifying Legitimately High Fidelity Loudspeakers: Vented vs. Non-Vented Woofers. It explains the way the air escapes from volume inside of the voice coil. Below is a drawing from the article. Quite self explaining.
The holes are listed in the article as a countermeasure.
In the case of the exciter, not sure there is really a vent. The "vent" diameter is very small. Might be the air goes mainly in the second direction of the drawing (to difficult to escape by the central tube).
Hello Eucy,
Clarity of vocals : do you know on which frequency range the dome is acting for that?
Searching information about the voice coil, I found this patent US20020094095A1 which is mainly about :
Christian
- the frequency cutoff between the voice coil mass and the panel mechanical impedance (no mention of the inductance effect ? doesn't exist?)
- the mode(s) inside of the coil area
- the possibility to increase the mechanical impedance with a longer contact line (some confirmation by other readers welcome) rather reducing the voice coil mass. (does it explain some 32mm exciters are appreciated compare to 25mm one?)
- a straight contact line is possible. This was suggested here (Tagis 4530) in a certain way
- there are also some data about membran made with Rohacell with glass veil (I introduced this material sometimes ago ie see 4694 or 4610)
- the mass in symmetry to the exciter to make a balance panel (already mentioned as an advantage of the 4 exciters combination)
Christian
Last edited:
Woofer magnets are vented mainly for VC cooling. In such a case the dust cap must be solid in order to force air through the VC and spider as in the pic. If you accidently put a permeable dust cap onto a vented magnet, then VC cooling is compromised, and power handling suffers.
If the magnet is not vented, then the dust cap has to be permeable to air. If the dust cap was impermeable, then the air would be trapped under the dust cap, and cone excursion would be drastically limited.
I can see that I really have to do side by side tests ... When I get time
But based on established frequency ranges, it must be acting in the 3k to 4k range. It doesn't increase sibilance (to my ears at least) on tracks I have tested so if it is boosting above 5k it's not enough to cause problems... That aspect may be track related of course, and most released tracks have been distributed to crunch sibilance anyway.
At the higher end, I have found the boost to be about 3dB
If you like, I'd be happy to make a pair to your dimensions and post them to you just to get the ball rolling 👍. They don't take long with the right equipment
Eucy
When considering frequency range and what we hear this chart of vocals, instruments by frequency ranges might prove helpful.https://onlinelibrary.wiley.com/doi/pdf/10.1002/9781119164746.app2
With the exception of violin, piano and pipe organ sounds above 3k- 5k are harmonics. Harmonics help create an instruments character and timbre so they are obviously important. I hope that is useful.
With the exception of violin, piano and pipe organ sounds above 3k- 5k are harmonics. Harmonics help create an instruments character and timbre so they are obviously important. I hope that is useful.
And this #5136 from HCSebastian where clarity is more associated to 2kHz (listed in the history file)
My 3-4k range assumption is based on a number of internet sources demonstrating how to achieve clarity in vocals thru equalisation... Boosting the 3-4k range was/is a common approach.
Time and more testing will tell I guess
@Veleric + REW users
Please find attached the REW "tuto" file already shared. I added some pages to show how I have wired the loopback time reference (see previous post about in panel wave speed)
Christian
PS : please find in my signature in the left panel the link to my page Homeswinghome under github.com where the files I have shared in this thread are going to be stored (history file and REW tuto available). Let me know if it doesn't work... correction of English also welcome.
Please find attached the REW "tuto" file already shared. I added some pages to show how I have wired the loopback time reference (see previous post about in panel wave speed)
Christian
PS : please find in my signature in the left panel the link to my page Homeswinghome under github.com where the files I have shared in this thread are going to be stored (history file and REW tuto available). Let me know if it doesn't work... correction of English also welcome.
Last edited: