Hi,
Does anyone know the driver characteristic responsible for the annoying 5kHz peak in the response of the Fostex 206E.
There are other peaks at 2.5kHz and 10kHz acording to the fostex plot, but they are not annoying me at all, maybe because all I can hear is this emphasised SSSSS!
It was evident before I cut the dustcaps out, it was equally evident with no dustcaps. I can't kill it with a cylindrical phase plug, and now my mind is dissolving into madness, and I can no longer see the light
!
Is damping the whizzer the solution, of does the nasty artifact originate elsewhere, perhaps a main cone break up mode?
I would also be curious to know which bump in the 206 impedance curve is the whizzer resonance, and the origin of the other (1kHz and 2.5kHz)
Apart from the 1kHz bump, it all looks a bit harmonic to me.. 2.5k, 5k, 10k.
Anyone shed any light on this for me?
Does anyone know the driver characteristic responsible for the annoying 5kHz peak in the response of the Fostex 206E.
There are other peaks at 2.5kHz and 10kHz acording to the fostex plot, but they are not annoying me at all, maybe because all I can hear is this emphasised SSSSS!
It was evident before I cut the dustcaps out, it was equally evident with no dustcaps. I can't kill it with a cylindrical phase plug, and now my mind is dissolving into madness, and I can no longer see the light
!
Is damping the whizzer the solution, of does the nasty artifact originate elsewhere, perhaps a main cone break up mode?
I would also be curious to know which bump in the 206 impedance curve is the whizzer resonance, and the origin of the other (1kHz and 2.5kHz)
Apart from the 1kHz bump, it all looks a bit harmonic to me.. 2.5k, 5k, 10k.
Anyone shed any light on this for me?
Could you supply an image of the frequency response chart showing the resonance modes?
This would be useful in trying to answer some of your questions. Keep in mind that Fostex has a habit of overlapping cone and dustcap/whizzer resonance modes. Instead of one resonance, there may well be a cone problem and a whizzer problem at the same frequency.
Mark
This would be useful in trying to answer some of your questions. Keep in mind that Fostex has a habit of overlapping cone and dustcap/whizzer resonance modes. Instead of one resonance, there may well be a cone problem and a whizzer problem at the same frequency.
Mark
Bob,
How brave are you?
One of the guys following the Walsh thread got brave and did what you see in the attached pic. Here are his words.
"I re-enabled my Fostex drivers per your template posted at the diy forum. Easy to do since the blocks are acrylic and wipe off with alcohol. Apparently, I was off by about 18 sets of blocks! This time I enabled the inside of the cone and whizzer as well as the outside, except that on the inside of the whizzer I "Mambonied" felt triangles. I also, Mambonied the back of the cone.
Right now I'm experiencing sound as if it were not coming from the speakers. Sounds now appear to come out of solid objects. The sounds in the background are now clear. And the sibilance is now gone; violins and close miked female vocal recordings don't cut my ears off anymore. The musical picture is/sounds more complete. I think this is quite remarkable coming from a near full range driver"
[*LINK REMOVED*]
Be glad to help you scare yourself, just to preserve your sanity. I will be treating a Lowther shortly .
Bud
How brave are you?
One of the guys following the Walsh thread got brave and did what you see in the attached pic. Here are his words.
"I re-enabled my Fostex drivers per your template posted at the diy forum. Easy to do since the blocks are acrylic and wipe off with alcohol. Apparently, I was off by about 18 sets of blocks! This time I enabled the inside of the cone and whizzer as well as the outside, except that on the inside of the whizzer I "Mambonied" felt triangles. I also, Mambonied the back of the cone.
Right now I'm experiencing sound as if it were not coming from the speakers. Sounds now appear to come out of solid objects. The sounds in the background are now clear. And the sibilance is now gone; violins and close miked female vocal recordings don't cut my ears off anymore. The musical picture is/sounds more complete. I think this is quite remarkable coming from a near full range driver"
[*LINK REMOVED*]
Be glad to help you scare yourself, just to preserve your sanity. I will be treating a Lowther shortly .
Bud
Might have to give this a shot on my next pair of drivers.Do you have any measurements of SPL response or electrical impedance before and after treating the driver?
It would be interesting to see what changes in driver performance occured. Intermediate measurements would also be interesting to be able to assess which modification produced which change in response.
It would be interesting to see what changes in driver performance occured. Intermediate measurements would also be interesting to be able to assess which modification produced which change in response.
Hi Chris,
You guys know lot's more about what Fostex has used than I.
I will say that the semi translucent nature of the paper, as we see it, would be typical of a thin, calendered, low rag content, high wood pulp content paper, when the conformal coating, I, and the brave soul who did this work, use.
I am trying to entice him to join in so you can all grill him in detail but that will be up to him.
Here is the other pic he sent to me and it shows the thickness of the felt he used and also the inner cone pattern. Scary thick felt pieces from my perspective, but I really have no idea how bad the problems he had were and this might be just the ticket for whizzer cones.
Dave, is it time to start an EnABL thread, that begins to collect all of the different posts in one spot? Is that even possible? Hate to have Chris fall out of his chair just trying to keep track of me jumping about.
Bud
You guys know lot's more about what Fostex has used than I.
I will say that the semi translucent nature of the paper, as we see it, would be typical of a thin, calendered, low rag content, high wood pulp content paper, when the conformal coating, I, and the brave soul who did this work, use.
I am trying to entice him to join in so you can all grill him in detail but that will be up to him.
Here is the other pic he sent to me and it shows the thickness of the felt he used and also the inner cone pattern. Scary thick felt pieces from my perspective, but I really have no idea how bad the problems he had were and this might be just the ticket for whizzer cones.
Dave, is it time to start an EnABL thread, that begins to collect all of the different posts in one spot? Is that even possible? Hate to have Chris fall out of his chair just trying to keep track of me jumping about.
Bud
Martin,
I do not have any quantitative data from this treatment. I have some data from other speakers and it is fairly generic, seems to have happened to all of the 2 or 3 hundred drivers I have gone through in 40 years of fooling around. Go here and look at the dissected CSD plots, at the end of the paper, from a "phenolic ring" cone tweeter as was popular in inexpensive speakers in the 80's.
http://www.positive-feedback.com/Issue21/standingwaves.htm
I will say that high frequency drivers will gain guite a bit more efficiency if you apply more than one coating of conformal /speed control material.
Other tests I have run, with an early generation Lincoln Audio test set up, show no observable alteration in the amount or distribution of harmonic distortion, throughout the first nine categories.
Bud
I do not have any quantitative data from this treatment. I have some data from other speakers and it is fairly generic, seems to have happened to all of the 2 or 3 hundred drivers I have gone through in 40 years of fooling around. Go here and look at the dissected CSD plots, at the end of the paper, from a "phenolic ring" cone tweeter as was popular in inexpensive speakers in the 80's.
http://www.positive-feedback.com/Issue21/standingwaves.htm
I will say that high frequency drivers will gain guite a bit more efficiency if you apply more than one coating of conformal /speed control material.
Other tests I have run, with an early generation Lincoln Audio test set up, show no observable alteration in the amount or distribution of harmonic distortion, throughout the first nine categories.
Bud
BudP said:
Yes it is... in this case probably gather together copies of all the relevant posts into a single thread, and if you write an intro post once that is created i can make it show up 1st. A list of relevant existing post numbers and the thread they are in is a good starting point.
Like Chris the EnAble has been hard to keep up with... i keep getting further & further in the Ohm F thread because i really want to go thru it in one sitting.
dave
BudP said:
So you're guessing the more mottled and darker than normal "caramel" color to the paper are a result of your recommended conformal coating applied over the treatment blocks?
From personal experience with other drivers, I'd think that a wooden phase plug could certainly be worth trying along with the EnAble pattern treatment.
could you please PM me?
BudP said:
Bud, OT or not.........can you look here
http://www.diyaudio.com/forums/showthread.php?postid=1187086#post1187086
and tell what you think.......in that thread.........
TIA
Hi Chris,
Did the PM go through, I am never sure I have the procedures quite straight.
As for the color of the cone, I do not know. Just the shiny surface and semi transparent nature of the cone, you can see the Mamboni triangles through the whizzer cone, are familiar.
Phase plugs and other post emitter surfaces all seem to benefit. I have no experience with phase plugs per se but I can see what I would do for many of the ones I have looked at.
The main thing to keep in mind is that this is a three vector pattern and seems to need to be placed just before any major deviation in surface is encountered. So, if the phase plug is an oblate shape, just before its surface becomes tangential to the emitting longitudinal compression wave front, is the most useful place to put the pattern. At the start and actual finish, if there is a distinct one at all, are also places to treat. These will be very small in benefit compared to the one at the tangential circumference.
Once you get involved with this pattern you do tend to treat all surfaces, just to learn the benefits, and one of the benefits is a reeducation of your correlator. Well, "benefits" I suppose, as you will become a bit short on tolerance for drivers that are not as well behaved as the EnABL'ed units are. Something of a pain some times.
Dave,
How should I go about this collection process? Just find and note all of the post numbers in the various threads, copy them to an email along with the initial text you mentioned? Or do I need to copy and reformat the actual posts themselves and send that plus the beginning one?
Bud
Did the PM go through, I am never sure I have the procedures quite straight.
As for the color of the cone, I do not know. Just the shiny surface and semi transparent nature of the cone, you can see the Mamboni triangles through the whizzer cone, are familiar.
Phase plugs and other post emitter surfaces all seem to benefit. I have no experience with phase plugs per se but I can see what I would do for many of the ones I have looked at.
The main thing to keep in mind is that this is a three vector pattern and seems to need to be placed just before any major deviation in surface is encountered. So, if the phase plug is an oblate shape, just before its surface becomes tangential to the emitting longitudinal compression wave front, is the most useful place to put the pattern. At the start and actual finish, if there is a distinct one at all, are also places to treat. These will be very small in benefit compared to the one at the tangential circumference.
Once you get involved with this pattern you do tend to treat all surfaces, just to learn the benefits, and one of the benefits is a reeducation of your correlator. Well, "benefits" I suppose, as you will become a bit short on tolerance for drivers that are not as well behaved as the EnABL'ed units are. Something of a pain some times.
Dave,
How should I go about this collection process? Just find and note all of the post numbers in the various threads, copy them to an email along with the initial text you mentioned? Or do I need to copy and reformat the actual posts themselves and send that plus the beginning one?
Bud
A few comments about the EnABL'd Fostex.
First to answer the original query of the thread, based on my experience with big (10db+) whizzer induced peaks, I think the best way to reduce them is to insert a notch filter. The second way it to diffuse the peak with a big plug, light bulb sized or bigger like the one used on the Beauhorn. The energy in the frequency is still there but is mitigated by the diffusion. I can't find the link but, there is a website where a guy experimented with different shapes and measured them (see also Tony Gee's site). If I recall correctly the best was the mushroom shape at diffusing the peak. The third way is to decouple the driver from the baffle. It is possible the 5kHz peak is baffle exaccerbated.
The Fostex lit states that the cone is made from banana pulp. I applied a few coats of C37 lacquer (the genuine stuff from Enomosser) a few years ago. Over time the color of the cone changed to what it is now, brownish like an aged banana. The result of lacquering was a dulling/smoothing of the sound from an already relatively smooth sounding Fostex driver, 168 Sigma. After reading Bud's and Manboni's descriptions, I thought I'd give it a try especially since I was not using the drivers. The end result is nothing short of fantastic.
In retrospect I wish I would have taken a basic frequency response measurement to see if the actual response was affected. FWIW, the response now is far from flat, but no "big" peaks and infinitely listenable.
If I were to make a guess, I don't think that either treatment is the solution for a big peak at 5kHz. I think that the treatment will make a good sounding driver sound better, and perhaps an okay sounding driver good, but will not act like a notch filter.
First to answer the original query of the thread, based on my experience with big (10db+) whizzer induced peaks, I think the best way to reduce them is to insert a notch filter. The second way it to diffuse the peak with a big plug, light bulb sized or bigger like the one used on the Beauhorn. The energy in the frequency is still there but is mitigated by the diffusion. I can't find the link but, there is a website where a guy experimented with different shapes and measured them (see also Tony Gee's site). If I recall correctly the best was the mushroom shape at diffusing the peak. The third way is to decouple the driver from the baffle. It is possible the 5kHz peak is baffle exaccerbated.
The Fostex lit states that the cone is made from banana pulp. I applied a few coats of C37 lacquer (the genuine stuff from Enomosser) a few years ago. Over time the color of the cone changed to what it is now, brownish like an aged banana. The result of lacquering was a dulling/smoothing of the sound from an already relatively smooth sounding Fostex driver, 168 Sigma. After reading Bud's and Manboni's descriptions, I thought I'd give it a try especially since I was not using the drivers. The end result is nothing short of fantastic.
In retrospect I wish I would have taken a basic frequency response measurement to see if the actual response was affected. FWIW, the response now is far from flat, but no "big" peaks and infinitely listenable.
If I were to make a guess, I don't think that either treatment is the solution for a big peak at 5kHz. I think that the treatment will make a good sounding driver sound better, and perhaps an okay sounding driver good, but will not act like a notch filter.
Thanks for all the input.
BudP, I am going to have a good read through the standing wave link. Cheers for that.
But
Not quite that brave yet. Maybe I will be if I can't find a more subtle solution!
ultrakaz,
I think this might be my initial fix for the problem, since I have tried damping the whizzer with blue tack in various weights and locations including dots on the whizzer, whizzer edge, inside the VC, etc. The only difference was lower overall treble sensitivity and increased system bass associated with the change in moving mass, along with the associated raise in system Q. The bloody peak remaineds. I'll experiment more with mass loading later (mechanical tone control!)
Maybe it could be a serious main cone mode since the whizzer is mechanically coupled with no steep roll off? I wouldn't have thought so since the main cone should still be well down at 5 kHz.
I killed the slight sibilance of my 166E's with the simple installation of Dave's phase plugs, but I think the 206 is a harder nut to crack.
Get that thread going, so we can read all the experiences, and maybe draw some real correlations to treatments and effect on frequency response.
Thanks agaibn for all the input.
Keep it rolling.
Bob
BudP, I am going to have a good read through the standing wave link. Cheers for that.
But
Not quite that brave yet. Maybe I will be if I can't find a more subtle solution!
ultrakaz,
I think this might be my initial fix for the problem, since I have tried damping the whizzer with blue tack in various weights and locations including dots on the whizzer, whizzer edge, inside the VC, etc. The only difference was lower overall treble sensitivity and increased system bass associated with the change in moving mass, along with the associated raise in system Q. The bloody peak remaineds. I'll experiment more with mass loading later (mechanical tone control!)
Maybe it could be a serious main cone mode since the whizzer is mechanically coupled with no steep roll off? I wouldn't have thought so since the main cone should still be well down at 5 kHz.
I killed the slight sibilance of my 166E's with the simple installation of Dave's phase plugs, but I think the 206 is a harder nut to crack.
Get that thread going, so we can read all the experiences, and maybe draw some real correlations to treatments and effect on frequency response.
Thanks agaibn for all the input.
Keep it rolling.
Bob
ultrakaz said:
I have to say that I agree. I have recently installed phase plugs which definately improved the balance of the driver but the notch filter is still needed to tame the shout in the midrange. I use a low damped SE tube amp with mine so I am going to reduce the L to .6mH and the parallel resistor to 2 ohms. I am using the alternate BR cabinet from the 206E PDF. Not optimum but nice none the less. Strongly considering building Mr. King's "virtual cabinets".
ultrakaz,
Thanks for posting and settling the question of the rotted banana cone colors.
Your comment about the 5 kHz peak in the driver is spot on. That is only addressable with a notch filter. If you were to see it in a waterfall it would look like a mountain ridge with small hills on both sides. The pattern would mitigate the length of time the ridge remained formed and would control the other sympathetic resonance's but that is all.
I am certain Mamboni's process is better at controlling this sort of thing than EnABL. Running those resonant ridges into jungle territory is bound to confuse and weaken them far more than the EnABL process will do.
That is why I am on about using both for every instance that they fit and you just proved that they work together even in the areas I was worrying about, the small light cones. Now I guess I will have to try some domes to see what happens there.
We have to make sure that the Mamboni process does not get steamrollered by EnABL hoopla. I really don't think that an all EnABL treatment would have worked nearly as well for you.
You are a brave man.
Bud
Thanks for posting and settling the question of the rotted banana cone colors.
Your comment about the 5 kHz peak in the driver is spot on. That is only addressable with a notch filter. If you were to see it in a waterfall it would look like a mountain ridge with small hills on both sides. The pattern would mitigate the length of time the ridge remained formed and would control the other sympathetic resonance's but that is all.
I am certain Mamboni's process is better at controlling this sort of thing than EnABL. Running those resonant ridges into jungle territory is bound to confuse and weaken them far more than the EnABL process will do.
That is why I am on about using both for every instance that they fit and you just proved that they work together even in the areas I was worrying about, the small light cones. Now I guess I will have to try some domes to see what happens there.
We have to make sure that the Mamboni process does not get steamrollered by EnABL hoopla. I really don't think that an all EnABL treatment would have worked nearly as well for you.
You are a brave man.
Bud
A new thread has been made from copies of posts in this and 2 other threads on EnAble + Mamboni
http://www.diyaudio.com/forums/showthread.php?s=&threadid=100399
dave
http://www.diyaudio.com/forums/showthread.php?s=&threadid=100399
dave
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.