Hello!
You guys seem to know very much about the BiB
(I'm a wee dazed of what I read in this 131-page thread....)
As you may or may not know, I've posted a thread asking for
possible designs for a Philips AD3800/AM driver.
Now, this is a dual-cone ("whizzer") type of driver,
and I was wondering if a BiB would be a good way to go.
But with a needed baffle opening of 183mm (that's slightly
over 7"), I cannot stick to the original TC' dimensions.
Can I just widen the whole lot and make an 8" internal BiB?
And with an Fs of 72Hz, what linelength should it be?
ooooh, I wish I had more background in this (or knew how
to calculate this sort af things)
Can anybody help me on this one?
regards
Empee
You guys seem to know very much about the BiB
(I'm a wee dazed of what I read in this 131-page thread....)
As you may or may not know, I've posted a thread asking for
possible designs for a Philips AD3800/AM driver.
Now, this is a dual-cone ("whizzer") type of driver,
and I was wondering if a BiB would be a good way to go.
But with a needed baffle opening of 183mm (that's slightly
over 7"), I cannot stick to the original TC' dimensions.
Can I just widen the whole lot and make an 8" internal BiB?
And with an Fs of 72Hz, what linelength should it be?
ooooh, I wish I had more background in this (or knew how
to calculate this sort af things)
Can anybody help me on this one?
regards
Empee
My apologies. I've just done a quick glance around the 'net. We're looking at classic jobs from the 1960s right? Are yours the 800ohm version by any chance? That means no T/S parameters (unless you can measure them yourself?).
I can give you a decent line length and Zdriver, however, with Vb we're in the realms of guesswork I'm afraid, not knowing the driver's Vas or Q. Anyway, I'd use a 105in line with a Zdriver of 21in. Beyond that, take a shot in the dark. I'd go for a hefty Vb as it's better to be too large than too small, so Sl=200in^2 might get you somewhere.
Got one other idea up my sleve. Not something I'd usually advise, but could be worth exploring at least. Back shortly.
I can give you a decent line length and Zdriver, however, with Vb we're in the realms of guesswork I'm afraid, not knowing the driver's Vas or Q. Anyway, I'd use a 105in line with a Zdriver of 21in. Beyond that, take a shot in the dark. I'd go for a hefty Vb as it's better to be too large than too small, so Sl=200in^2 might get you somewhere.
Got one other idea up my sleve. Not something I'd usually advise, but could be worth exploring at least. Back shortly.
We don't want to tune the driver too low, so roughly, using Martin King's alignment tables, you could try a TQWT with So=Sd, Sl=3Sd, internal length of 75in, driver at 0.377 line length (from So). That's about as far as we can go with the tables though without any driver parameters; I'm wary about shooting in the dark.
Finally, you could try (I can't believe I'm saying this) a Voigt pipe. I don't like these cabinets at all, but unless someone can provide a set of parameters, we're just guessing anyway, so it's unlikely to be worse than anything else you could build.
A few years back, I seem to remember that Herb Jeschke actually built a pair of 8 foot tall VPs for a pair of big old Philips 800 ohm drivers. Going by memory, they were 96in tall or thereabouts, with a base that was 12.5in wide x 12.5in deep (internal). St (driver position, or more accurately the cross-section of the pipe at the driver-centre, which was usually taked to = driver surface area) was usually approximately 0.47 line length. I beleive the formula was St = L / 2 + (cube root of So / Sl). Vent area was also normally taken to roughly equal to the cone area of the driver a la the original, pre T/S alignment, bass reflex patent (Greg, put me straight on these if I'm wrong).
Best
Scott
Finally, you could try (I can't believe I'm saying this) a Voigt pipe. I don't like these cabinets at all, but unless someone can provide a set of parameters, we're just guessing anyway, so it's unlikely to be worse than anything else you could build.
A few years back, I seem to remember that Herb Jeschke actually built a pair of 8 foot tall VPs for a pair of big old Philips 800 ohm drivers. Going by memory, they were 96in tall or thereabouts, with a base that was 12.5in wide x 12.5in deep (internal). St (driver position, or more accurately the cross-section of the pipe at the driver-centre, which was usually taked to = driver surface area) was usually approximately 0.47 line length. I beleive the formula was St = L / 2 + (cube root of So / Sl). Vent area was also normally taken to roughly equal to the cone area of the driver a la the original, pre T/S alignment, bass reflex patent (Greg, put me straight on these if I'm wrong).
Best
Scott
Greets!
FWIW, back in pre-T/S days many DIYers used Altec's nomographs to build cabs based on only the driver's frame size and published Fs, which I SWAGed to ~8*Sd for Am (aka Sm) when L = 1/2 WL of Fs (BIB tuning) in a At (aka So) = 0 conical pipe firing into a corner.
I only built a few because it was assumed that a large driver had to be used to keep from overdriving them due to TT 'rumble' (we were mostly clueless about line level filters), ergo too big even back when 2 ft^3 was considered bookshelf sized, but the cavernous, pipe organ like room excitation was, er, exciting, especially to young adult females!
Maybe size really does matter, my speakers have always been big, with a low Fb (for the times), and never had any speaker size related SAF issues.
I seriously doubt that they would measure well whether outdoors or in-room by today's standards, but driven with a tube p-p amp that has bass control (adjustable DF) and with a bit of mouth/corner damping as required, any 'boominess'/obvious tonal imbalance could be smoothed over, so EQ is your 'friend' down below ~100 Hz.
GM
FWIW, back in pre-T/S days many DIYers used Altec's nomographs to build cabs based on only the driver's frame size and published Fs, which I SWAGed to ~8*Sd for Am (aka Sm) when L = 1/2 WL of Fs (BIB tuning) in a At (aka So) = 0 conical pipe firing into a corner.
I only built a few because it was assumed that a large driver had to be used to keep from overdriving them due to TT 'rumble' (we were mostly clueless about line level filters), ergo too big even back when 2 ft^3 was considered bookshelf sized, but the cavernous, pipe organ like room excitation was, er, exciting, especially to young adult females!
Maybe size really does matter, my speakers have always been big, with a low Fb (for the times), and never had any speaker size related SAF issues. I seriously doubt that they would measure well whether outdoors or in-room by today's standards, but driven with a tube p-p amp that has bass control (adjustable DF) and with a bit of mouth/corner damping as required, any 'boominess'/obvious tonal imbalance could be smoothed over, so EQ is your 'friend' down below ~100 Hz.
GM
AD3800
http://www.hupse.nl/radio/speakers/AD3800.htm
I've not had a set of 3800s, but the AD2800 http://www.hupse.nl/radio/speakers/AD2800.htm i've had had the same lattice basket (unlike the link) and cone, but with a smaller motor, and i do have numbers for those. Here is the average of 4 fairly closely matched units.
Fs 80.86
Re 3.78
Qms 6.67
Qes 2.73
Qts 1.93
Vas 32.83
Cone mass 7.65
Sd 213.82
dB 90.18
comp cm/dyne 5.08E-07
BL 2.33
Measured with low V. Higher V will give lower Fs, Qt, and larger Vas.
dave
http://www.hupse.nl/radio/speakers/AD3800.htm
I've not had a set of 3800s, but the AD2800 http://www.hupse.nl/radio/speakers/AD2800.htm i've had had the same lattice basket (unlike the link) and cone, but with a smaller motor, and i do have numbers for those. Here is the average of 4 fairly closely matched units.
Fs 80.86
Re 3.78
Qms 6.67
Qes 2.73
Qts 1.93
Vas 32.83
Cone mass 7.65
Sd 213.82
dB 90.18
comp cm/dyne 5.08E-07
BL 2.33
Measured with low V. Higher V will give lower Fs, Qt, and larger Vas.
dave
Nice one Dave. From that, I'd say that Qt, even accounting for a high voltage driver and larger magnet will likely still be too high for a BIB. I think the highest we've done was by Greg -one for the B200, which is up at around 0.7 I believe (off the top of my head). Terminus is a monster 350in^2.
An open ended, untapered pipe like a big Alpha might be about the best box option at present. Fudging around the data, I plugged some info into Greg's Alpha TL spreadsheet. Assuming a Qt of about 0.8, a Vas of about 40 litres, and tuning the box to 50Hz (too low, but it's non-resonant, so it shouldn't damage things) you could try one ~54in long, 264in^2 CSA, 0.6lbs ft^3 of fibreglass damping. Alternatively 64in long, 193in^2 CSA, 1.3lbs ft^3 of Dacron. Best I can suggest really.
An open ended, untapered pipe like a big Alpha might be about the best box option at present. Fudging around the data, I plugged some info into Greg's Alpha TL spreadsheet. Assuming a Qt of about 0.8, a Vas of about 40 litres, and tuning the box to 50Hz (too low, but it's non-resonant, so it shouldn't damage things) you could try one ~54in long, 264in^2 CSA, 0.6lbs ft^3 of fibreglass damping. Alternatively 64in long, 193in^2 CSA, 1.3lbs ft^3 of Dacron. Best I can suggest really.
800 ohm versions. Nice. Very nice indeed. Wish I had some.
Yes and no. You could use the way Greg explained based on the old Altec formulas, then damp it down, but the price, as he notes, will be a gigantic footprint. As in a 700in^2 footprint.
Assuming that you can't live with a box that size, then a fudged Alpha might work, and I gather that Herb's old traditional 8 foot tall Voigt Pipe, heavily stuffed, was very well recieved when people heard it. I'm normally no fan of the trad VP, but I'll see if I can dig some more information out if you like as I admit I'm curious myself; given that it's been tried this might be a safer bet than the Alpha. Meantime, you can spot it in a couple of pictures here, and there's some reference to it too. http://melhuish.org/audio/oswaldsmill.html
Final way, as Dave observes, is open baffle which suites high Q drivers well.
Best
Scott
Yes and no. You could use the way Greg explained based on the old Altec formulas, then damp it down, but the price, as he notes, will be a gigantic footprint. As in a 700in^2 footprint.
Assuming that you can't live with a box that size, then a fudged Alpha might work, and I gather that Herb's old traditional 8 foot tall Voigt Pipe, heavily stuffed, was very well recieved when people heard it. I'm normally no fan of the trad VP, but I'll see if I can dig some more information out if you like as I admit I'm curious myself; given that it's been tried this might be a safer bet than the Alpha. Meantime, you can spot it in a couple of pictures here, and there's some reference to it too. http://melhuish.org/audio/oswaldsmill.html
Final way, as Dave observes, is open baffle which suites high Q drivers well.
Best
Scott
Hi folks,
look at this beautifful fullrangers from Hungary
http://www.sonido.hu/eng/home.htm
What do you think about some BIB with Sonido drivers
look at this beautifful fullrangers from Hungary
http://www.sonido.hu/eng/home.htm
What do you think about some BIB with Sonido drivers
Wow !!
I gotta admit (and my girl is gonna kill me for this)
that I kinda like the idea of 8 foot tall speakers in the livingroom
WAAAAAAAAAH!!
as it no big investment to build a pair of MDF
(a quick calculation shows less than 80 euro's)
Could you please calculate the dimensions for my AD3800AM ?
(Metric, please....)
thanks in advance!
I gotta admit (and my girl is gonna kill me for this)
that I kinda like the idea of 8 foot tall speakers in the livingroom
WAAAAAAAAAH!!
as it no big investment to build a pair of MDF
(a quick calculation shows less than 80 euro's)
Could you please calculate the dimensions for my AD3800AM ?
(Metric, please....
)thanks in advance!
The Trad. Voigt Pipes you mean? Oh boy. If you insist:
243.84cm tall
36.25cm wide x 36.25cm deep at the base. Comes to a point at the top.
St (distance of driver from the top) 106.75cm.
Vent 36.25cm wide, 14.75cm tall.
I want to stress at this point that I cannot vouch for this cabinet, other than to say that it's been tried before, and was apparantly well liked, judging from the comments in the aforementioned link. Response will not exactly be flat, if I know anything about it, but likely no worse tahn anything else. That said, as you observe, 18mm MDF is pretty cheap, so you won't be loosing much by trying it aside from about £20 for the material and another £5 or so for some firberglass or whatever cheap damping material takes your fancy, so it's probably worth a punt. BTW, it won't actually be quite 8ft tall -assuming you use 8ft sheets, it'll be limited by how tall the angled back panel can go. I believe the originals had wings attached to the sides to lower the point of baffle step, so that could also be a tweak worth trying.
Have fun & do take some pictures!
Scott
243.84cm tall
36.25cm wide x 36.25cm deep at the base. Comes to a point at the top.
St (distance of driver from the top) 106.75cm.
Vent 36.25cm wide, 14.75cm tall.
I want to stress at this point that I cannot vouch for this cabinet, other than to say that it's been tried before, and was apparantly well liked, judging from the comments in the aforementioned link. Response will not exactly be flat, if I know anything about it, but likely no worse tahn anything else. That said, as you observe, 18mm MDF is pretty cheap, so you won't be loosing much by trying it aside from about £20 for the material and another £5 or so for some firberglass or whatever cheap damping material takes your fancy, so it's probably worth a punt. BTW, it won't actually be quite 8ft tall -assuming you use 8ft sheets, it'll be limited by how tall the angled back panel can go. I believe the originals had wings attached to the sides to lower the point of baffle step, so that could also be a tweak worth trying.
Have fun & do take some pictures!
Scott
BIBs have nice proportions and can be finished as fine furniture or even art. They certainly deserve to be considered ‘musical instruments’ because they provide audible advantages over conventional box speakers. They can be used with better sounding low powered SS, Digital or Tube amps because they need little power to play loudly.
My first pair of BIBs will flank a bookcase in my office. Height will not be an issue at all and in many other instances floor space is really the limiting factor. My second BIB will flank a media wall unit – height will not be an issue there either. Wherever floor standing speakers or monitors on stands are being considered, a BIB might be a better choice both visually and sonically.
I hope to finish mine in the month of September… grrrrrrr…
Godzilla
My first pair of BIBs will flank a bookcase in my office. Height will not be an issue at all and in many other instances floor space is really the limiting factor. My second BIB will flank a media wall unit – height will not be an issue there either. Wherever floor standing speakers or monitors on stands are being considered, a BIB might be a better choice both visually and sonically.
I hope to finish mine in the month of September… grrrrrrr…
Godzilla
Hi everybody!
Just a brief question: I'm drawing on paper my future BIBs, waiting for drivers delivering..... I'm considering to leave one side unglued for easy stuffing and tweaking (as I posted before), but it sounds more difficult than leaving just the base "open"....(considering a 1,8" thick material the side should be quite heavy...)
Does anyone experienced if it's so unconfortable working through base and top and rear-driver hole considering a 66" height 'circa'?
Thanks. Ciao. Fab.
p.s. more thoughts about my spreadsheet?
Just a brief question: I'm drawing on paper my future BIBs, waiting for drivers delivering..... I'm considering to leave one side unglued for easy stuffing and tweaking (as I posted before), but it sounds more difficult than leaving just the base "open"....(considering a 1,8" thick material the side should be quite heavy...)
Does anyone experienced if it's so unconfortable working through base and top and rear-driver hole considering a 66" height 'circa'?
Thanks. Ciao. Fab.
p.s. more thoughts about my spreadsheet?