Re: Baffled
Unless I have missread or missed earlier posts - no! Mine, and I beleive most BIBs for 168ESigs and similar size drivers are built with a single thickness and front baffle, usually 18mm thick with optional supra-baffle. Supra baffle serves 2 purposes - one of which is to move the magnet away from the internal panel such that the magnet can clear it, the 168 magnet will just clear the internal panel usung a 18mm supra baffle, obviously you could use a thicker supra if you wish.
And yes - it is common practice to flare any the internal baffle structure such that cone reflections are minimised, I usualy make the baffle hole cut with a jigsaw set at 45degrees.
pebbles said:
Unless I have missread or missed earlier posts - no! Mine, and I beleive most BIBs for 168ESigs and similar size drivers are built with a single thickness and front baffle, usually 18mm thick with optional supra-baffle. Supra baffle serves 2 purposes - one of which is to move the magnet away from the internal panel such that the magnet can clear it, the 168 magnet will just clear the internal panel usung a 18mm supra baffle, obviously you could use a thicker supra if you wish.
And yes - it is common practice to flare any the internal baffle structure such that cone reflections are minimised, I usualy make the baffle hole cut with a jigsaw set at 45degrees.
Variac said:
Greets!
Hard to say without speaker, room details. Anyway, I just used a cheap RadioShack 25 ohm pot alligator clipped in series and dialed it up until it sounded tonally balanced, then measured the resistance and made a fixed one to hard wire in. I guess the only warning would be to make sure your amp can handle the load and power losses if > ~8 ohms dials it in.
GM
Thanks Scott but I must plead ignorance. Where does the shift from 2pi to 4pi radiation space(not really sure what this is) occur, literally at the edge of the baffle? Does the size and shape of the suprabaffle determine which frequencies are compensated for. I'm afraid this has gone somewhat over my head and I need to search further back into this thread or to another source for homework on this. Suffice to say I will put my BIB on steroids. Thanks Chris for your input as well. Regards, AndrewScottmoose said:
It's the loss of sound pressure levels (SPLs) below the baffle-step point due to less energy being directed toward the listener. The frequency at which it occurs is determined by the baffle width. Have a read of this, if you're interested in the technical aspects: http://www.t-linespeakers.org/tech/bafflestep/index.html
Scottmoose said:
Scott, I was under the impression that, in a BIB design, baffle step loss was largely compensated for by the fact that a BIB cabinet operates against a wall (or in a corner) which effectively means it is operating in 2pi space. Is this not the case, or maybe only partly the case?
Cheers.
Mostly the case. You don't really want to be running the horn higher than ~300Hz if possible, so using a baffle to push the step point down to this zone is a good idea IMO. But it depends where they are in the room really, from both a gain & step-point perspective. Some won't need it, some will. As every, YMMV. Even if you don't get any benefit from them in that respect, the extra mass loading the driver-frame & stiffening the front baffle is good to have, and they should help with the wavelaunch, so long as it's been sized & shaped right.
Inverted BIB with a half twist
I'm looking to make a set of speaks for a friend on the cheap with limited tools and skills (read, "no skills). On the cheap side of things, I'm going with the Pioneer A11 and stock 4' cuts of particle board and pine.
He's in a really tall space right now, and even if he moved back to a small apartment (bound to happen sooner or later), 4' is really not going to load the ceiling, so I've inverted them. Not wanting to do anything fancy and wanting to get a bit of extra line length, I've added a second fold, at the bottom, just at 90 degrees, and have the mouth on the back, at the bottom. I figure this gets me a line of about 102" which is not half bad, and that plus a mouth opening of around 60"^2, it should be good for driver rolling with most of the 4.5" Fostex (though I doubt that'll happen; he's not the most discerning listener, and this is mainly to replace listening to either the speakers in his LCD TV or to a set of Creative 2.1 computer speakers).
I'm just building the one, first . . . want to test it before I buy more lumber and finish the pair. I'm waaay more picky than the intended audience. Besides, I want to play with them myself a bit.
Kensai
I'm looking to make a set of speaks for a friend on the cheap with limited tools and skills (read, "no skills). On the cheap side of things, I'm going with the Pioneer A11 and stock 4' cuts of particle board and pine.
He's in a really tall space right now, and even if he moved back to a small apartment (bound to happen sooner or later), 4' is really not going to load the ceiling, so I've inverted them. Not wanting to do anything fancy and wanting to get a bit of extra line length, I've added a second fold, at the bottom, just at 90 degrees, and have the mouth on the back, at the bottom. I figure this gets me a line of about 102" which is not half bad, and that plus a mouth opening of around 60"^2, it should be good for driver rolling with most of the 4.5" Fostex (though I doubt that'll happen; he's not the most discerning listener, and this is mainly to replace listening to either the speakers in his LCD TV or to a set of Creative 2.1 computer speakers).
I'm just building the one, first . . . want to test it before I buy more lumber and finish the pair. I'm waaay more picky than the intended audience. Besides, I want to play with them myself a bit.
Kensai
An externally hosted image should be here but it was not working when we last tested it.
how short can the enclosure be shortenned?
so I've lurked on this thread, but finally have a question.
BTW , thanks scott for the info...
looking at the Hemp FR8c drivers specifications I end up with a total horn length of 161.43", 4.98 ft^3. But with a cabinet height of 81", and ceilings at 98", they'll dominate the room too much. can I shorten them by 20" without effect or not? if not, perhaps the idea as presented by Kensai would work?
any input appreciated.
stew
so I've lurked on this thread, but finally have a question.
BTW , thanks scott for the info...
looking at the Hemp FR8c drivers specifications I end up with a total horn length of 161.43", 4.98 ft^3. But with a cabinet height of 81", and ceilings at 98", they'll dominate the room too much. can I shorten them by 20" without effect or not? if not, perhaps the idea as presented by Kensai would work?
any input appreciated.
stew
ok..scott
well at 5 ft^3, the box won't be small , even if I shorten it.
so to keep with my "why not mdf" responses, and Baltic Birch is available in 60" X 60" chunks here...
if I make the internal width 10", the internal depth 14.14", then the height can be limited to 60". Am I correct? Also because the fold will create some length to the "horn" then I could actually get the enclosure to be no more than 60" tall as an outside dimension. Seem reasonable?
and how much will it raise Fc?
well at 5 ft^3, the box won't be small , even if I shorten it.
so to keep with my "why not mdf" responses, and Baltic Birch is available in 60" X 60" chunks here...
if I make the internal width 10", the internal depth 14.14", then the height can be limited to 60". Am I correct? Also because the fold will create some length to the "horn" then I could actually get the enclosure to be no more than 60" tall as an outside dimension. Seem reasonable?
and how much will it raise Fc?
It all depends.
Assuming you use the T/S parameter based calculation GM came up with to establish the ~optimum Vb, then this enclosure is not going to require 5ft^3 volume. It wants 22.6209 cubic feet. Per cabinet. The relatively high Vas & middling Q of the Hemp Acoustics driver mean it needs a lot of volume. Using a 60in tall box, with a 26in Zdriver, this means internal WxD dimensions of 21.5in x 30.375in. Fc is 36Hz, should be usable to 30Hz (before room-gain). A baby box 60in x 10in x 14in just isn't going to work I'm afraid -it's flat not big enough.
Something smaller than the ~ideal is possible, but it depends just how big you can go. This is assuming the HA parameters are accurate of course -they're far too pat to be believable.Qt is incorrect for the other claimed figures for a start.
Assuming you use the T/S parameter based calculation GM came up with to establish the ~optimum Vb, then this enclosure is not going to require 5ft^3 volume. It wants 22.6209 cubic feet. Per cabinet. The relatively high Vas & middling Q of the Hemp Acoustics driver mean it needs a lot of volume. Using a 60in tall box, with a 26in Zdriver, this means internal WxD dimensions of 21.5in x 30.375in. Fc is 36Hz, should be usable to 30Hz (before room-gain). A baby box 60in x 10in x 14in just isn't going to work I'm afraid -it's flat not big enough.
Something smaller than the ~ideal is possible, but it depends just how big you can go. This is assuming the HA parameters are accurate of course -they're far too pat to be believable.Qt is incorrect for the other claimed figures for a start.
Scott, thanks for the link re BSC, that was very helpful. Unfortunately I have been informed that the 168 ez's I ordered are out of stock; a 2-3 week wait....Damm. However I have emailed a few OS distributors who may be quicker.
Interestingly there are a pair of used Lowther PM6a's with new fabric surrounds on EBay down here and I reckon they could be had for about the same price as the Fostex. I cant find much info(any) specification wise so I have no idea what size BIB they would need nor do I have any idea whether they would be suited to one at all. What sort of boxes would suit these ? Regards, Andrew
Interestingly there are a pair of used Lowther PM6a's with new fabric surrounds on EBay down here and I reckon they could be had for about the same price as the Fostex. I cant find much info(any) specification wise so I have no idea what size BIB they would need nor do I have any idea whether they would be suited to one at all. What sort of boxes would suit these ? Regards, Andrew
I'd be very wary about 2nd hand Lowthers, especially if, as you say, they've had a new surround fitted. If the factory did it, they'll be fine, but if someone else (a possible monkey) has been fooling with them, I'd suggest avoiding. Lowthers need TLC, although if you got them for peanuts (sorry) you could always send them back to Lowther, either for a service, or, better yet, an upgrade for new units, at a much reduced price. Lowthers will work in most things if you design it right, so your call.
Re: ok..scott
Surely there are some furniture and marine grade plys in 4x8 up there. Most of them would cost an arm down here, but it should be cheaper for you. It would be kind of a PITA, but you could probably edge glue the birch ply to make it work. It would probably be easier than more ambitious back horn designs.
I'd be curious to see a model of a short BIB. I wonder if you'd lose enough low freq. extension that the Mileva would start to look more ideal.
pj
Nanook said:
Surely there are some furniture and marine grade plys in 4x8 up there. Most of them would cost an arm down here, but it should be cheaper for you. It would be kind of a PITA, but you could probably edge glue the birch ply to make it work. It would probably be easier than more ambitious back horn designs.
I'd be curious to see a model of a short BIB. I wonder if you'd lose enough low freq. extension that the Mileva would start to look more ideal.
pj
furniture grade ply...
I am very partial to Baltic Birch. Availability is 5' X 5" sheets, that's it.
Scott, I guess I didn't notice your spreadsheet does one column or the other (metric vs imperial) , not both simultaneously, that's where I got the 5 cu ft number, but the volume is 608 litres or so which is 37077 cu. inches.
using GM's 140 " tall dimension results in a 27.37" X 19.36" enclosure. with z=30.38", so a pretty huge enclosure...guess I'll be looking for a different driver
I am very partial to Baltic Birch. Availability is 5' X 5" sheets, that's it.
Scott, I guess I didn't notice your spreadsheet does one column or the other (metric vs imperial) , not both simultaneously, that's where I got the 5 cu ft number, but the volume is 608 litres or so which is 37077 cu. inches.
using GM's 140 " tall dimension results in a 27.37" X 19.36" enclosure. with z=30.38", so a pretty huge enclosure...guess I'll be looking for a different driver
Nanook... if you want a shorter cabinet you can look at the Half Chang using either the Fostex 206e, 207e or Pioneer B20 (plus a helper tweeter). This cabinet is about 50 inches tall and uses an 8 inch driver like the hemp you wanted to use.
My BIBs are about 65 inches tall using the Fostex 165k. Im sure the 168S will also work in this shorter than optimal cabinet too. I have the older 168 and it worked great. Just less extension into the lower depths i suppose (without having listened to both speakers - but the charts suggest less extension).
My BIBs are about 65 inches tall using the Fostex 165k. Im sure the 168S will also work in this shorter than optimal cabinet too. I have the older 168 and it worked great. Just less extension into the lower depths i suppose (without having listened to both speakers - but the charts suggest less extension).
scottmoose, godzilla and GM
thanks for the encouragement. (and help)
50" tall is max outside dimension, due to the sheet size of Baltic Birch availble here. I really don't want to use anything else, but would consider other marine grade plywood that is voidless. Almost all "choice grade" wood products are exported to the good old USof A, rather than sold to the Canadian market
My intent was to try a BiB, because of the longevity of the thread and the apparent good results many have had. I already have the Hemp Acoustics FR8c drivers, so I figured a quick and easy build would be good.
These speakers are an experiment for one of my kids' boyfriends, who has an idea of what quality is about. I can get other drivers, I just want to make sure that it is to his taste before commtting any real money on drivers. As he uses his system for both HT and music, I'm hoping to get him into something that is good (but reasonable priced). He's not against spending money , but would like a known quantity. Currently using a mass market HT reciever (which he's willing to change if need be). Currently using some no-name or HT included non-0descript speakers. He'll also need a cenmtre channnel as well. TV is a DLP projector, so shielding may not be an issue.
so that's really the issue.
He did hear the planet10 Fonkens when I had them here, and really enjoyed them, but the HT reciever will most likely sound pretty bad (or rather the Fonkens would sound bad being driven by the reciever). I'm not sure how much or to quality point he'd be willing to go, but he did say he'd be willing to buy a different reciever or amp. He has heard good 2 channel at my place . I'm usually not this carefull, but this guy could end up marrying my daughter (and long term familia peace would be a good thing).
thanks for the encouragement. (and help)
50" tall is max outside dimension, due to the sheet size of Baltic Birch availble here. I really don't want to use anything else, but would consider other marine grade plywood that is voidless. Almost all "choice grade" wood products are exported to the good old USof A, rather than sold to the Canadian market
My intent was to try a BiB, because of the longevity of the thread and the apparent good results many have had. I already have the Hemp Acoustics FR8c drivers, so I figured a quick and easy build would be good.
These speakers are an experiment for one of my kids' boyfriends, who has an idea of what quality is about. I can get other drivers, I just want to make sure that it is to his taste before commtting any real money on drivers. As he uses his system for both HT and music, I'm hoping to get him into something that is good (but reasonable priced). He's not against spending money , but would like a known quantity. Currently using a mass market HT reciever (which he's willing to change if need be). Currently using some no-name or HT included non-0descript speakers. He'll also need a cenmtre channnel as well. TV is a DLP projector, so shielding may not be an issue.
so that's really the issue.
He did hear the planet10 Fonkens when I had them here, and really enjoyed them, but the HT reciever will most likely sound pretty bad (or rather the Fonkens would sound bad being driven by the reciever). I'm not sure how much or to quality point he'd be willing to go, but he did say he'd be willing to buy a different reciever or amp. He has heard good 2 channel at my place . I'm usually not this carefull, but this guy could end up marrying my daughter (and long term familia peace would be a good thing).
Re: scottmoose, godzilla and GM
You're welcome!
Looks like a BIB isn't 'in the cards'.......
Hmm, BB ply is 60" square, so if getting closer to the edge is OK, this MLTL may work, though like any MLTL there's the issue of blending a smaller CC to them if he doesn't set them to 'small' and XO to a sub when used for HT:
L = 57.5"
CSA = ~113"^2 (recommend 13.5" W x 8.375" D)
zdriver = 20.875"
zport = 45"
port = 4" dia. x 0.75"
density = 0.2 lbs/ft^3 down to the port
If 'boomy' in-room, either more damping and/or a longer vent can be used to roll it off.
GM
You're welcome!
Looks like a BIB isn't 'in the cards'.......
Hmm, BB ply is 60" square, so if getting closer to the edge is OK, this MLTL may work, though like any MLTL there's the issue of blending a smaller CC to them if he doesn't set them to 'small' and XO to a sub when used for HT:
L = 57.5"
CSA = ~113"^2 (recommend 13.5" W x 8.375" D)
zdriver = 20.875"
zport = 45"
port = 4" dia. x 0.75"
density = 0.2 lbs/ft^3 down to the port
If 'boomy' in-room, either more damping and/or a longer vent can be used to roll it off.
GM
