Scottmoose said:Something's just occured to me -exactly which driver are we talking about here? The FR8? Or the new FR8C? The published specs are different. Assuming both are accurate (I'll believe that when I see it) the old driver had a lower Vas 88 litres, rather than the new unit's 95.5-odd. Motor seems the same, but the old unit's (equally smoothed out) response looks like it has slightly less of a rise. 2KHz: new unit ~99db. Old unit ~95db. Cone material's changed too.
We are using the new Hemp driver - FR8C.
planet10 said:Add a parallel RLC shelving filter. The L controls where the LF are let loose, the C where the top is. The size of the R determines how much the mids are shelved down. (with your sensitivity to the top you may get away without the C, in which case it becomes what we know today as a BSC filter).
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
As to the ripple, since you are prepared to abandon the box, cutting a k-slot would be a beneficial experiment to the entire community.
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:
We are using the new Hemp driver - FR8C.
Hmm, if the older FR8's parameters significantly deviates from the new FR8C's then it might also add to the anomalies you're hearing. The design on Zillaspeak is for the older Hemp driver.
Hardman said:I too have played around with the CSS subwoofers and really like them. I have both drivers currently. Just need to find some time to put them into a box. I know you are a fan of push-push enclosures, any designs for the SD12 or SDX15 (I guess if I weren’t so lazy I could just look on your site)?
I just added ShadowSD12 plans to the Spawns page -- an excellent companion woofer for Tommy Chang (here a pic with Curvy Chang)
dave
Attachments
Hardman said:I would love to give back to the community. What modifications do we need to make to the existing cabinet?
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: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.
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.
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: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.
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
Originally posted by planet10 I just added ShadowSD12 plans to the Spawns page -- an excellent companion woofer for Tommy Chang (here a pic with Curvy Chang)dave
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
Hardman said:I am a little hesitant going horn again, but willing to give it a shot....I liked this sub so much I ordered a driver for myself.
Keep in ming that a BVR is really a bass reflex done up in horn-like clothing. Also note that anyone who wants the Subduction drivers i can supply (and discuss a forum break)
dave
Re: FR8C parametres measured by me.
Thanks! My meter says 0.5mH as opposed to your 0.35
I think my meter measures at 400Hz, I'll check.
Will try to do some T/S measurements here tomorrow.
Originally posted by salas FR8C parametres measured by me.
...
Thanks! My meter says 0.5mH as opposed to your 0.35
I think my meter measures at 400Hz, I'll check.
Will try to do some T/S measurements here tomorrow.
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
Re: My 2 cents
So you have the old version then? I don't think FR8c has been out that long.
dave
bigdh31 said:I have been listening to the FR8 for 8 months and have been enjoying them.
So you have the old version then? I don't think FR8c has been out that long.
dave
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
Re: not out for very long....
You've EnABLed them?
dave
Nanook said:My super secret reversible EnABLed speakers sound quite excellent driven by my Amp 6 Basic [/B]
You've EnABLed them?
dave
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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