Exciting new line of fullrange drivers from Feastrex - Page 2 - diyAudio
Go Back   Home > Forums > Commercial Sector > Manufacturers > Feastrex

Feastrex Hand crafted speakers

Reply
 
Thread Tools Search this Thread
Old 3rd January 2006, 06:00 AM   #11
diyAudio Member
 
cdwitmer's Avatar
 
Join Date: Apr 2003
Location: Tokyo
Thanks very much, Bill. I will pass this on to the manufacturer. This particular driver does not use Permendur. However, their actual measurements of gap flux density are higher than what the diagram suggests . . . it makes me wonder about how accurately their drawings represent the actual internal construction of the driver. (I note, for example, that their drawings do not indicate a shorting ring, even though I know they use them.)

I'm sure you know far more about drivers than I do, but I certainly endorse your view on the need for saturation at the gap. For optimum performance, saturation at the gap is essential. On the other hand, if achieving saturation outside the gap area does anything useful (especially if the gap itself isn't saturated), then I don't know what that might be . . .

Gratefully,

Christopher Witmer
__________________
"Avoiding deportation from Japan for over a quarter century!"
  Reply With Quote
Old 3rd January 2006, 11:22 AM   #12
Bill F. is offline Bill F.  United States
diyAudio Member
 
Bill F.'s Avatar
 
Join Date: Nov 2001
Location: SW MI
Quote:
On the other hand, if achieving saturation outside the gap area does anything useful (especially if the gap itself isn't saturated), then I don't know what that might be . . .
I was wondering about this, too.

Unless its gap faces are always saturated (practically impossible with healthy LF signals in the VC) there is a certain amount of field reversal and iron modulation in all dynamic bass and wide-band drivers. This flavors the sound to varying degrees, perhaps even in a pleasing manner in some cases.

Faraday rings can help with iron modulation only in the mid/treble and up as they couple with the VC field less and less efficiently as frequency drops. I can think of only three real ways manufacturers are currently combating LF iron modulation. In decending order of effectiveness: ATC's SLMM, 18Sound's AIC, and JBL's Differential Drive.

In the case of this Feastrex driver, at least the flux bottleneck is high up the pole, quite near the gap, which I imagine would allow less iron modulation than if it were at the base of the pole, as in so many other drivers.

Also, by reducing flux in the gap, it probably allows a higher Qts and therefore more bass.

Anyway, none of this is to say that this Feastrex doesn't sound great. I just raise the question about the flux bottleneck because it goes against conventional wisdom, and I'm quite sure it wasn't a cost-saving maneuver in this case!

Bill
  Reply With Quote
Old 5th January 2006, 12:10 AM   #13
Vikash is offline Vikash  United Kingdom
diyAudio Moderator Emeritus
 
Vikash's Avatar
 
Join Date: May 2003
Location: UK
Hi Bill,

Nice work there, but I wouldn't be sure the illustration you based the sim on is anything more than just to give a visual of the concept.

Firstly the specs state 1.8T in the gap vs the simulated 0.5-0.7T. Also for something where cost is not a huge constraint (I assume) they would have missed some simple angles in the motor design that would achieve more symmetrical fields too.

Also the sim. design is cut through the centre which could be a reason for the magnitude of the bottleneck. What if you draw the other half slice of the motor, hence full thickness pole piece as in the mfg. dia.
__________________
"The human mind is so constituted that it colours with its own previous conceptions any new notion that presents itself for acceptance." - J. Wilhelm. (But I still think mine sounds better than yours.)
  Reply With Quote
Old 5th January 2006, 01:36 AM   #14
MJK is offline MJK  United States
Account disabled at member's request
 
Join Date: Feb 2002
Location: Clifton Park, NY
Quote:
Firstly the specs state 1.8T in the gap vs the simulated 0.5-0.7T.
You believe everything a manufacturer tells you? I don't. I wonder how they determined they had 1.8T in the gap.

Quote:
Also the sim. design is cut through the centre which could be a reason for the magnitude of the bottleneck. What if you draw the other half slice of the motor, hence full thickness pole piece as in the mfg. dia.
My guess is, and Bill can confirm, that the model is axisymmetric in which case the math accounts for the part not shown on the other sied of the centerline axis. Looks like a very nice program, I used to use ANSYS for magnetic field calculations when I was working for an MRI S/C magnet manufacturer.
  Reply With Quote
Old 5th January 2006, 01:59 AM   #15
Vikash is offline Vikash  United Kingdom
diyAudio Moderator Emeritus
 
Vikash's Avatar
 
Join Date: May 2003
Location: UK
Quote:
Originally posted by MJK
You believe everything a manufacturer tells you? I don't. I wonder how they determined they had 1.8T in the gap.
You believe everything a simulation tells you?

FEMM really is I need to start playing with it again.
__________________
"The human mind is so constituted that it colours with its own previous conceptions any new notion that presents itself for acceptance." - J. Wilhelm. (But I still think mine sounds better than yours.)
  Reply With Quote
Old 5th January 2006, 10:46 AM   #16
MJK is offline MJK  United States
Account disabled at member's request
 
Join Date: Feb 2002
Location: Clifton Park, NY
Quote:
You believe everything a simulation tells you?
If I know the basis for the simulation, and have confidence in the analyst doing the simulation, then I have a good feeling for what accuracy and inaccuracy is present in the results. No simulation is perfect, the best simulations are only good enough to give an accurate result for a specific set of questions.

Do I believe a glossy marketing data sheet with one very detailed result but no T/S parameters (which are kind of fundamental properties)? To be polite, I will only say I am skeptical and would not spend the money on the drivers yet without more trustworthy information. I would spend the money on AER or Lowther drivers first with much more confidence.
  Reply With Quote
Old 5th January 2006, 11:46 AM   #17
BTW is offline BTW
diyAudio Member
 
Join Date: Nov 2002
Location: Singapore
Quote:
Originally posted by MJK


Do I believe a glossy marketing data sheet with one very detailed result but no T/S parameters (which are kind of fundamental properties)? To be polite, I will only say I am skeptical and would not spend the money on the drivers yet without more trustworthy information. I would spend the money on AER or Lowther drivers first with much more confidence.

I have a pair of Japanes Exact drivers which are realted somewhat to the Feastrex drivers. It's an excellent driver much more transparent and faster than the Coral Beta 8 which I also own. I would say in addition to AER, Lowthers..... you can put the Exact and probably the Feastex in the same category. Ultimately which single driver you finally choose will depends on the type of cabinets and taste..
  Reply With Quote
Old 5th January 2006, 11:59 AM   #18
MJK is offline MJK  United States
Account disabled at member's request
 
Join Date: Feb 2002
Location: Clifton Park, NY
Quote:
I would say in addition to AER, Lowthers..... you can put the Exact and probably the Feastex in the same category. Ultimately which single driver you finally choose will depends on the type of cabinets and taste..
For me, the final choice comes down to who has at least one reputable US distributor and who has the best technical information available to determine if the driver will align with my interests. If they have a US distributor and the distributor is difficult to deal with then that also rules out the driver, I had this happen when I wanted to buy AER and Supravox drivers a few years ago. Personally, I would not order an expensive driver all the way from Japan period. There are just too many risks both technically and logistically. But that is just my opinion.
  Reply With Quote
Old 5th January 2006, 12:09 PM   #19
BTW is offline BTW
diyAudio Member
 
Join Date: Nov 2002
Location: Singapore
Quote:
Originally posted by MJK


For me, the final choice comes down to who has at least one reputable US distributor and who has the best technical information available to determine if the driver will align with my interests. If they have a US distributor and the distributor is difficult to deal with then that also rules out the driver, I had this happen when I wanted to buy AER and Supravox drivers a few years ago. Personally, I would not order an expensive driver all the way from Japan period. There are just too many risks both technically and logistically. But that is just my opinion.
Fair enough, but do note they will be exhibiting at the CES over the weekend hopefully some reputable US dealer will pick up the line... If that happens, I'll really look forward to reading more reviews about the drivers..
  Reply With Quote
Old 5th January 2006, 12:42 PM   #20
Bill F. is offline Bill F.  United States
diyAudio Member
 
Bill F.'s Avatar
 
Join Date: Nov 2001
Location: SW MI
Hi Vikash,

Quote:
Nice work there, but I wouldn't be sure the illustration you based the sim on is anything more than just to give a visual of the concept.

Firstly the specs state 1.8T in the gap vs the simulated 0.5-0.7T. Also for something where cost is not a huge constraint (I assume) they would have missed some simple angles in the motor design that would achieve more symmetrical fields too.

Also the sim. design is cut through the centre which could be a reason for the magnitude of the bottleneck. What if you draw the other half slice of the motor, hence full thickness pole piece as in the mfg. dia.
I agree that we shouldn't make too much of an illustration that may not reflect the full reality of the actual motor. Whatever the actual proportions, though, if the pole is drastically undercut (as they seem to illustrate) and there isn't significant tapering toward the gap, then there must necessarily be a flux bottleneck below the gap. Also, as Christopher mentioned, the pole cap is not in fact permendur. I can't see how they could achieve anywhere near 1.8T in the gap under these conditions.

Again, though, let me say that I still admire the drivers as audio objects d'art, whether or not they rigidly conform to spec, and I'd love to see more boutique manufacturers crop up. Actually, I'll likely join a new ultra-high-end effort later this year... (and we'll always supply lots of accurate specs and measurements).


Quote:
My guess is, and Bill can confirm, that the model is axisymmetric in which case the math accounts for the part not shown on the other sied of the centerline axis.
Correct, Martin.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



New To Site? Need Help?

All times are GMT. The time now is 12:04 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2