Scottmoose said:
We are using the new Hemp driver - FR8C.
planet10 said:
For kicks I think I will apply some BSC and see what effect it has on the speaker. I have a Vidsonix crossover box that should enable rough BSC for one speaker (mono). I am only going to be able to get the L value for the circuit from the crossover box. I have a few resistors that hopefully I will be able to series/parallel to get the correct value. If someone is feeling helpful, a double check on my BSC math would be welcomed. Baffle = 16.25" and Re according to Hemp’s specs is 6.2 ohm.
dB - R - L
1 - 0.8 - 0.4
2 - 1.6 - 0.9
3 - 2.6 - 1.4
4 - 3.6 - 2.0
5 - 4.8 - 2.7
6 - 6.2 - 3.5
I would love to give back to the community. What modifications do we need to make to the existing cabinet?
OK, my 2 cents worth.
A simple LR shelving filter does not work well on these drivers. Why? Rising impedance. You will need a Zobel circuit to tame it. Otherwise all you do is dish out the mids - I know, I've tried.
I have built a variable BSC filter for the FR8c. So far values of about 15R+1mH sounds best on my open baffles, but it's not ideal. No Zobel on this one.
As for the rise seen in the new FR chart, who knows? The grapevine tells me that whizzer cone drivers are notoriously hard to measure, so who knows what was done to that graph or how it was measured. My measurements do not show that rise at all on OB. Just a 2.5K peak that may be voice coil related. Otherwise pretty flat out to about 14K. But I do not have an ideal measurement set up, so I could be all wet.
So far, I've been able to make the driver sound good, but never great. As Greg says, it's a wide BW mid that needs help at the top and the bottom. That's what I'm trying to do, but it ain't easy.
A simple LR shelving filter does not work well on these drivers. Why? Rising impedance. You will need a Zobel circuit to tame it. Otherwise all you do is dish out the mids - I know, I've tried.
I have built a variable BSC filter for the FR8c. So far values of about 15R+1mH sounds best on my open baffles, but it's not ideal. No Zobel on this one.
As for the rise seen in the new FR chart, who knows? The grapevine tells me that whizzer cone drivers are notoriously hard to measure, so who knows what was done to that graph or how it was measured. My measurements do not show that rise at all on OB. Just a 2.5K peak that may be voice coil related. Otherwise pretty flat out to about 14K. But I do not have an ideal measurement set up, so I could be all wet.
So far, I've been able to make the driver sound good, but never great. As Greg says, it's a wide BW mid that needs help at the top and the bottom. That's what I'm trying to do, but it ain't easy.
Hardman said:
1st you need to choose to add a single Karlson Slot on the back or 2 -- 1/2 slots on the sides (this seems to make most sense. Then download the excel Karlson Slot calculator and play with some slots
http://melhuish.org/audio/download/?C=N;O=D (K-Slot.xls)
Not a lot is known about the proper sizing so you guys are in an ideal opportunity to 1st/ see how well it works, 2nd/ get a bit of a handle on sizing. (i'd start small and grow the slot until it is too much -- then you can burn the boxes
)dave
panomaniac said:
Greets!
Good to know!
A previous version of this driver had a very low measured Le, so it seemed safe to assume the new model would have the same basic motor, but if this measured rise is due mainly to inductance, then yes, a zobel is required before any BSC or notch filter design be calc'd.
Hmm, on axis hasn't been a problem for me, but off axis is another matter altogether, so the driver ideally needs to be on a swivel to get repeatable results. Still, this doesn't account for yours not having the rising response and the BIB would tend to have too much bass in-room if his were ~flat to 14 kHz.
GM
planet10 said:
Well, if the early adopters got it right, then ~half of the sides tapered all the way to the bottom needs to be cut out: http://home.planet.nl/~ulfman/files/poppe_kcoupler.pdf
Looks like the Tommy Chang is 73" tall. No reusing BIB parts in this desing. We have one full sheet of 4' X 8' BB left, but it will take two to pull this design off. Hummm.
Ok, I am signing up for this one! I am a little hesitant going horn again, but willing to give it a shot. Back around the first of the year I built an SD12 sealed (.57 or so Qtc) sub for another friend. I liked this sub so much I ordered a driver for myself. I have been sitting on the driver for a while waiting for such a design as this to come along. I like a tight transient bass response, and dislike the bass boom from ported designs. My limited experience with MLTL has been positive. What will Shadow sound like?
This K slot thing is starting to sound like work .
Chris
Ok, I am signing up for this one! I am a little hesitant going horn again, but willing to give it a shot. Back around the first of the year I built an SD12 sealed (.57 or so Qtc) sub for another friend. I liked this sub so much I ordered a driver for myself. I have been sitting on the driver for a while waiting for such a design as this to come along. I like a tight transient bass response, and dislike the bass boom from ported designs. My limited experience with MLTL has been positive. What will Shadow sound like?
Originally posted by planet10
1st you need to choose to add a single Karlson Slot on the back or 2 -- 1/2 slots on the sides (this seems to make most sense. Then download the excel Karlson Slot calculator and play with some slots
http://melhuish.org/audio/download/?C=N;O=D (K-Slot.xls)
Not a lot is known about the proper sizing so you guys are in an ideal opportunity to 1st/ see how well it works, 2nd/ get a bit of a handle on sizing. (i'd start small and grow the slot until it is too much -- then you can burn the boxes
dave
This K slot thing is starting to sound like work
. Chris
My 2 cents
I have been listening to the FR8 for 8 months and have been enjoying them. I just built a 78 liter box with a 4 inch wide by 3 inch port tube.
They do sound bright and at times irritating for the first 100 hours or so. After that they sound more balanced and the bass becomes pretty decent. If you are evaluating an enclosure and/or BSC circuit you need to burn in the driver well first.
I have been driving them with a 41hz Amp6 and am very satisfied with the combo. I did end up using a rear mounted fill tweeter to bleed a little energy out of the FR8 above 10k and to help with the beaming issue. I just put a 1 mfd capacitor in series with the tweeter. I did not use any BSC circuit with them.
I have been listening to the FR8 for 8 months and have been enjoying them. I just built a 78 liter box with a 4 inch wide by 3 inch port tube.
They do sound bright and at times irritating for the first 100 hours or so. After that they sound more balanced and the bass becomes pretty decent. If you are evaluating an enclosure and/or BSC circuit you need to burn in the driver well first.
I have been driving them with a 41hz Amp6 and am very satisfied with the combo. I did end up using a rear mounted fill tweeter to bleed a little energy out of the FR8 above 10k and to help with the beaming issue. I just put a 1 mfd capacitor in series with the tweeter. I did not use any BSC circuit with them.
Attachments
not out for very long....
My set are the "C" version, and I got em at Christmas (er "holiday" time) '06 for review. I bought the test samples.
I must agree that they do sound a little shrill initially, but smooth out after 100 hrs+.
The c37 has helped (I think) as have the phase plugs. My super secret reversible EnABLed speakers sound quite excellent driven by my Amp 6 Basic
My set are the "C" version, and I got em at Christmas (er "holiday" time) '06 for review. I bought the test samples.
I must agree that they do sound a little shrill initially, but smooth out after 100 hrs+.
The c37 has helped (I think) as have the phase plugs. My super secret reversible EnABLed speakers sound quite excellent driven by my Amp 6 Basic
kinda EnABLed
I did a reversible physical mod that results in what I believe to be the EnABL process. Can't afford to mod drivers (unless the results are completely known), but can modify their environment
As the EnABL process or result effectively minimizes cone/surround defraction problems...I shared my idea with BudP and am still "testing"
I did a reversible physical mod that results in what I believe to be the EnABL process. Can't afford to mod drivers (unless the results are completely known), but can modify their environment
As the EnABL process or result effectively minimizes cone/surround defraction problems...I shared my idea with BudP and am still "testing"
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