Greetings all,
I plan on building the BIB cabinets for the FR125S.
I have downloaded the BIB calculator worksheet from Zilla Audio. The pre-calculated external dimensions given are width 9 inches, depth 12 inches, height 49 inches.
I just want to be sure that I have not missed something as most BIB designs I have seen appear to be quite tall.
The example below is of someone who has built a FR125S BIB and it looks to be around 6 foot tall.
http://www.diyaudio.com/forums/showthread.php?threadid=111789
The dimensions on the BIB calculator are around 4 foot tall.
Have I missed something in terms of understanding the design? I would prefer to maximise bass from these little drivers where possible. Should I build the BIB cabinet for the FR125S as per the BIB calculator or is there some advantage gained by lengthening the line that I do not understand?
Thanks,
Cangaceiro
I plan on building the BIB cabinets for the FR125S.
I have downloaded the BIB calculator worksheet from Zilla Audio. The pre-calculated external dimensions given are width 9 inches, depth 12 inches, height 49 inches.
I just want to be sure that I have not missed something as most BIB designs I have seen appear to be quite tall.
The example below is of someone who has built a FR125S BIB and it looks to be around 6 foot tall.
http://www.diyaudio.com/forums/showthread.php?threadid=111789
The dimensions on the BIB calculator are around 4 foot tall.
Have I missed something in terms of understanding the design? I would prefer to maximise bass from these little drivers where possible. Should I build the BIB cabinet for the FR125S as per the BIB calculator or is there some advantage gained by lengthening the line that I do not understand?
Thanks,
Cangaceiro
If I understand you correctly, if I input the drivers T/S parameters incl an Fs (70Hz) this will give me a default line length where:
Line length = speed of sound / Fs / 2
So if I set a lower Fs, then I will end up with a longer line (taller cabinet) and lower LF gain, but this is dangerous for the driver and you therefore recommend against this for both tuneability and safety of the driver?
Thanks for your reply ScottMoose. I'm just trying to understand your response more clearly as my knowledge of this subject if very small.
Line length = speed of sound / Fs / 2
So if I set a lower Fs, then I will end up with a longer line (taller cabinet) and lower LF gain, but this is dangerous for the driver and you therefore recommend against this for both tuneability and safety of the driver?
Thanks for your reply ScottMoose. I'm just trying to understand your response more clearly as my knowledge of this subject if very small.
Right.
You'll end up with a longer line, a lower tuning frequency and a little less LF gain; these things are relative however. The FR125SR has a lot of excursion, so within reason, you can just keep plugging in a lower Fs value for a longer, lower tuned horn. That's not dangerous for the driver per se. However, there are limits, & with that soft suspension, you could bottom it out at high SPLs on material with a lot of large LF transient swings. So the message is, if you tune low (frankly, WRT the FR125, I'd just stuff it into Terry's original cabinet & enjoy), & crank the volume up, keep an eye on the driver & if it bottoms out, back things off a trifle.
john blackburn said:
As I recall it's sm.
That's what I've used.
for a sort of split screen or multimedia view of the BIB, there is this:
http://www.zillaspeak.com/bib-howtobuild.asp
If you select the BIB 166 it gives multiple representations
quite attractively for BIB theory.
Regards line length, I too have wondered how extreme it can be.
Right now I'm gluing up a small BIB with the measures for a 50 cent Pioneer driver (I guess they were about 10 bucks before closeout.)
This one will be a little less than 3 ft when done.
I also have a 50 center in a BIB cab for the FE127e. Even though
the low end seems less refined in this combination, I have been very satisfied with certin music sources WRT instrumentation.
The experiment is to see if the BIB made to the correct scale from the calculator retains those interesting properties.
Then I will start on some driver mods.
Lon (still looking for the definitive Enable how to.)
So = cross sectional area of the sealed end of the horn (for a BIB, this is 0, as it comes to a point & has no surface area.)
Sl or Sm = cross sectional area of the terminus of the horn
Zdriver = distance of the centre of the driver from So.
Zdriver for the BIB = 0.217L where L = total horn length.
Sl or Sm = cross sectional area of the terminus of the horn
Zdriver = distance of the centre of the driver from So.
Zdriver for the BIB = 0.217L where L = total horn length.
I'm going through this whole experiment right now in a thread a couple of pages back (update soon). I made an oversized pair of BIB inspired pipe/horn boxes and am working my way through drivers to learn about what was happening.
The BIB calculator shows that the fr125 will work fine, but I tested the boxes with fostex 108e sigma and 126e first. I thought that making the csa a bit bigger might be beneficial, but according to my experimentation so far, the calculator seems a very safe bet to follow, as neither of the drivers I have so far seem to be a good match. (External dims IIRC - 52x8.25x14.25, very close to yours)
The 108, with it's high fs (probably even higher than published specs would indicate) had a rough time in those boxes, in exactly the same way that they would have a rough time in a ported box tuned too low for them. The 126 was not quite so bad, but severely limited in displacement unless used with a sub. The FR125 is the ticket, I just have to bite the bullet and spend some more cash.
The BIB calculator shows that the fr125 will work fine, but I tested the boxes with fostex 108e sigma and 126e first. I thought that making the csa a bit bigger might be beneficial, but according to my experimentation so far, the calculator seems a very safe bet to follow, as neither of the drivers I have so far seem to be a good match. (External dims IIRC - 52x8.25x14.25, very close to yours)
The 108, with it's high fs (probably even higher than published specs would indicate) had a rough time in those boxes, in exactly the same way that they would have a rough time in a ported box tuned too low for them. The 126 was not quite so bad, but severely limited in displacement unless used with a sub. The FR125 is the ticket, I just have to bite the bullet and spend some more cash.
I have the CSS drivers in my first ever diy speakers, a pair of 9 litre MDF ported boxes, but the woodwork leaves a lot to be desired and they still need stands making.
Rather than make stands for boxes that look like they have been nibbled by wolves I could try some bibs for about the same "footprint". If I pay for the cutting doing properly they should look much nicer and I've heard another speaker type/design as well.
John
Rather than make stands for boxes that look like they have been nibbled by wolves I could try some bibs for about the same "footprint". If I pay for the cutting doing properly they should look much nicer and I've heard another speaker type/design as well.
John
John, the bass output from a BIB will absolutely stomp all over the ported boxes.
That's what I was counting on, and listed several reasons why oversizing might just work well. In fact, the large csa was not my real downfall anyway, I think. I was totally expecting a 50 hz tuning but I was surprised to realize a very strong 40 hz tuning. The point of the project was to make mains that did not need a sub, and 40 hz with no sub is a bit too much to ask from a 4 inch fostex. At a 50 hz tuning it might have barely scraped by.
Anyway, the fr125 could probably be used well in a line longer than mine (and the OP's) but I don't see the point in making a 4 inch driver go lower than 40 hz. If you need to go lower than 40 you need different speakers. ymmv
Thanks Scott - and btw I will have some measured fostex specs from my drivers to add to the pool in the next couple of days.
That's what I was counting on, and listed several reasons why oversizing might just work well. In fact, the large csa was not my real downfall anyway, I think. I was totally expecting a 50 hz tuning but I was surprised to realize a very strong 40 hz tuning. The point of the project was to make mains that did not need a sub, and 40 hz with no sub is a bit too much to ask from a 4 inch fostex. At a 50 hz tuning it might have barely scraped by.
Anyway, the fr125 could probably be used well in a line longer than mine (and the OP's) but I don't see the point in making a 4 inch driver go lower than 40 hz. If you need to go lower than 40 you need different speakers. ymmv
Thanks Scott - and btw I will have some measured fostex specs from my drivers to add to the pool in the next couple of days.
Great thanks ScottMoose. I think I understand better now.
So if the T/S recommended Fs is 70Hz, then would going for something like 40-50Hz be OK or do you think that would be a step too far?
I have no idea what is reasonable, although I'm guessing that going below 50Hz might be asking to much from this driver.
So if the T/S recommended Fs is 70Hz, then would going for something like 40-50Hz be OK or do you think that would be a step too far?
I have no idea what is reasonable, although I'm guessing that going below 50Hz might be asking to much from this driver.
Speaker Clearance
Hi,
I sketched up a BIB for the CSS FR125 a couple of weeks ago. I based the speaker on 5/8" thick material.
The BIB calculator gave me internal dimensions of 10.54" deep x 7.45" wide x 48.09" high. I used 10.5625" x 7.5" x 48". Z driver was 20.875".
I noticed that there was not much clearance between the rear of the speaker (3" less 5/32") and the angled piece of wood.
I don't have any FR125s and never made the BIBs but I thought I would mention this.
You would gain some clearance with 3/4" material and/or adjusting Zdriver.
I'll try attaching a diagram.
Hi,
I sketched up a BIB for the CSS FR125 a couple of weeks ago. I based the speaker on 5/8" thick material.
The BIB calculator gave me internal dimensions of 10.54" deep x 7.45" wide x 48.09" high. I used 10.5625" x 7.5" x 48". Z driver was 20.875".
I noticed that there was not much clearance between the rear of the speaker (3" less 5/32") and the angled piece of wood.
I don't have any FR125s and never made the BIBs but I thought I would mention this.
You would gain some clearance with 3/4" material and/or adjusting Zdriver.
I'll try attaching a diagram.
Attachments
One solution is to make a front baffle double thick.
I've done this to give the same sort of clearance. The suggestion came from GM.
The speaker cutout is done to size and the inner baffle has a cutout an inch wider. If both cutouts are chamfered it makes a wave guide.
When I did mine, I left the 'steps' in the cutouts which is another approach.
Right now I cannot give a good opinion of the double baffle. With one driver it seemed that I was losing mids. With the current setup,
I have the mids but lower frequencies are undefined.
But this post is just about the option you may want to consider.
GM likes the FR125. Perhaps he will chime in here.
I've done this to give the same sort of clearance. The suggestion came from GM.
The speaker cutout is done to size and the inner baffle has a cutout an inch wider. If both cutouts are chamfered it makes a wave guide.
When I did mine, I left the 'steps' in the cutouts which is another approach.
Right now I cannot give a good opinion of the double baffle. With one driver it seemed that I was losing mids. With the current setup,
I have the mids but lower frequencies are undefined.
But this post is just about the option you may want to consider.
GM likes the FR125. Perhaps he will chime in here.
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