Wow - I can't get over how many posts can occur over 24 hrs!
I'd like to get back to the question Scottmoose posed to GM (?) earlier:
"(for example, Sl=100in^2, and the possible difference between 10in x 10in WxD, and 5in x 20in WxD). He didn't think it'd be significant as the CSA down the line doesn't change (assuming no folds of course) between the two of them. Any thoughts you could add on that one?"
I've asked the question before about the 1.4142 W x D ratio. I understand that it may be the best ratio in a MLTL but can't figure out how it applies to a BIB. You can acheive a 1.4142 W X D ratio at the mouth of a BIB but the ratio can't be maintained in the rest of the BIB (2 walls are parallel and 2 wall aren't). Am I missing the boat here or are you only referring to the mouth?
I'd like to get back to the question Scottmoose posed to GM (?) earlier:
"(for example, Sl=100in^2, and the possible difference between 10in x 10in WxD, and 5in x 20in WxD). He didn't think it'd be significant as the CSA down the line doesn't change (assuming no folds of course) between the two of them. Any thoughts you could add on that one?"
I've asked the question before about the 1.4142 W x D ratio. I understand that it may be the best ratio in a MLTL but can't figure out how it applies to a BIB. You can acheive a 1.4142 W X D ratio at the mouth of a BIB but the ratio can't be maintained in the rest of the BIB (2 walls are parallel and 2 wall aren't). Am I missing the boat here or are you only referring to the mouth?
Neither. It's not really the best ratio in an MLTL BTW -I'd rather go with golden ratio for that, though the damping makes it less significant in these cabinets than in, say, a reflex box.
You've missed the fact that I asked Greg and Martin different things -my fault for not being particularly clear. What I asked Martin was about the angle of flare rate in a TQWT assuming no folds, if there might be potentially a change in the harmonic resonances (which he reckons it won't), and how best to model this in MathCad. My question to Greg was in re the WxD ratio specifically WRT the BIB -turns out when you draw a bend out to scale, assuming two parallel walls, & the sloping internal baffle equidistant from front, rear and floor, whatever the other two walls angle is, it comes out to sqrt (2), or the 1:1.4142. I paraphrase from Greg here as he has a gift of explanation I lack, shall we say.
You've missed the fact that I asked Greg and Martin different things -my fault for not being particularly clear. What I asked Martin was about the angle of flare rate in a TQWT assuming no folds, if there might be potentially a change in the harmonic resonances (which he reckons it won't), and how best to model this in MathCad. My question to Greg was in re the WxD ratio specifically WRT the BIB -turns out when you draw a bend out to scale, assuming two parallel walls, & the sloping internal baffle equidistant from front, rear and floor, whatever the other two walls angle is, it comes out to sqrt (2), or the 1:1.4142. I paraphrase from Greg here as he has a gift of explanation I lack, shall we say.
Dave Cigna said:
Greets!
Correct. More factual than intuitive. Think about it, there's this supersonic A/C pulse 'train' vibrating along the entire length of the pipe that's powerful enough to shoot out the terminus a considerable distance before moving back into it, so if we insert a discontinuity in its expansion, it causes a shockwave (standing wave or eigenmode) back to the point where it started, so every other cycle it's going to hit the back of the driver hard enough to modulate it at that frequency. Since this shockwave will have its own harmonics, the driver will be modulated by a series of frequencies at varying amplitudes, just like it does when it gets reflections from an undamped rear wall right behind the driver, only a lot more intense because the fundamental will be a lot lower in frequency due to the typically much longer pathlength.
It's primarily for this reason you need a big filter chamber for simple stepped pipe BLHs, to cushion/damp this contant bombardment. With longer/smoother bend horns a smaller filter chamber can be used, though the trade-off is more out of phase mids exiting the mouth to comb filter with the driver's output, trading one type of comb filtering distortion for another, so it's up to the designer to choose what proportions of these two types sounds best and lay it out accordingly and why I long ago concluded that the best BLH is either none, or at most, BW limited to mid-bass/lower mids duty ('scoop' bins).
As always though, YMMV.
GM
Bravo, everyone!! Great input and work from evvybuddy!
Halellujah Noel
Be it Heaven or Hell
We're out of here and down to San Miguel for a cheapie cheapie six day-er, so best wishes to The BIBsters, and much more folded fun and brand new noise-makers in the dayz to come.
warm wishes,
DrD, J-Dog, & Buster
Halellujah Noel
Be it Heaven or Hell
We're out of here and down to San Miguel for a cheapie cheapie six day-er, so best wishes to The BIBsters, and much more folded fun and brand new noise-makers in the dayz to come.
warm wishes,
DrD, J-Dog, & Buster
Neofone, before I start cutting timber.
Christmas Greetings All.
Before I start cutting timber for my holiday project I would like to confirm measurements I have for a Neofone BIB.
http://www.diyhifisupply.com/images/neo note.JPG
Line length: 128 in
Zdriver: 25.75 in
Sm: 55 sq in
I don't recall where I got these measurements from, probably somewhere deep within this thread.
Can anyone confirm or deny these specs'.
Thanks
Verk.
Christmas Greetings All.
Before I start cutting timber for my holiday project I would like to confirm measurements I have for a Neofone BIB.
http://www.diyhifisupply.com/images/neo note.JPG
Line length: 128 in
Zdriver: 25.75 in
Sm: 55 sq in
I don't recall where I got these measurements from, probably somewhere deep within this thread.
Can anyone confirm or deny these specs'.
Thanks
Verk.
Sorry I've been absent for a few days guys -work's taken up a bit of time recently.
As per a request for the neophone, here's one.
Line length 128in.
Zdriver 25.75in
Sm (or Sl if you are so inclined) 55in^2.
I'd like to think this driver is a good one, though I doubt we'll know until someone gives it a whirl. Expensive risk. The specs are nice though, which is a good start.
Cheers
Scott
PS, Greg -how are you doing it in the BLH sheet? I'm assuming set a tapered CC from So to the driver centre point, and the throat as the same area as the driver end?
S.
Scottmoose has attached this image:
Click the thumbnail to see the original image.
As per a request for the neophone, here's one.
Line length 128in.
Zdriver 25.75in
Sm (or Sl if you are so inclined) 55in^2.
I'd like to think this driver is a good one, though I doubt we'll know until someone gives it a whirl. Expensive risk. The specs are nice though, which is a good start.
Cheers
Scott
PS, Greg -how are you doing it in the BLH sheet? I'm assuming set a tapered CC from So to the driver centre point, and the throat as the same area as the driver end?
S.
Scottmoose has attached this image:
Click the thumbnail to see the original image.
I posted this in a much earlier response to Scott and others, but apparently didn't save the link. 
Not to de rail the Neofone convo but...
With the Cary amp (thru the 168S BIBs) the Stereophile test tones are stronger at 40hz compared to the SI amp which barely makes a sound.
With the Cary - 31.5hz is clearly audible… 25hz is also clearly audible but much quieter… 20hz is also audible if I turn the volume up but just a subtle rumbling.
The SI doesn’t produce anything below 40hz which is down substantially compared to 50hz… does anyone understand? LOL! People in the office think I’m nuts playing these tones.
I haven’t listened to music yet… but my initial curiosity about the bass has been confirmed… it’s weak thru the SI amp. This was not noticeable enough for me to bring in the Cary to compare when I had the Fostex 127e’s hooked up in the Straight Pipes or the Pioneer/Piezo in the sealed cabinets.
So the BIBs are extremely revealing of amplification…
Truly,
Godzilla
PS… On Pink Floyd’s ‘Us and Them’ the sound was thin thru the SI… thru the Cary there is an undulating bass right in the beginning and throughout the song which solidifies the entire presentation. The sax in the beginning sounds small and thin (kazoo like) thru the SI… thru the Cary is sounds like the sax is in the room.
Bass, midrange and treble are all improved using the MUCH more expensive Cary. My bubble has burst over the SI :-(
With the Cary amp (thru the 168S BIBs) the Stereophile test tones are stronger at 40hz compared to the SI amp which barely makes a sound.
With the Cary - 31.5hz is clearly audible… 25hz is also clearly audible but much quieter… 20hz is also audible if I turn the volume up but just a subtle rumbling.
The SI doesn’t produce anything below 40hz which is down substantially compared to 50hz… does anyone understand? LOL! People in the office think I’m nuts playing these tones.
I haven’t listened to music yet… but my initial curiosity about the bass has been confirmed… it’s weak thru the SI amp. This was not noticeable enough for me to bring in the Cary to compare when I had the Fostex 127e’s hooked up in the Straight Pipes or the Pioneer/Piezo in the sealed cabinets.
So the BIBs are extremely revealing of amplification…
Truly,
Godzilla
PS… On Pink Floyd’s ‘Us and Them’ the sound was thin thru the SI… thru the Cary there is an undulating bass right in the beginning and throughout the song which solidifies the entire presentation. The sax in the beginning sounds small and thin (kazoo like) thru the SI… thru the Cary is sounds like the sax is in the room.
Bass, midrange and treble are all improved using the MUCH more expensive Cary. My bubble has burst over the SI :-(