Finished my BIB horns with FE168 sigmas

gnugear

Member
2005-08-07 8:26 pm
Spent the weekend building my BIB speakers (thanks Godzilla for the help). Very simple and easy to assemble. I've had the Fostex 168 sigmas in a spiral horn that I made out of (don't laugh) extra thick foam core and it sounded horrible. These are MUCH better! :) Fortunately it gave me a chance to break in the speakers so I've already got over 100 hours on them.

The speakers have deep bass, huge sound stage and better imaging than my Paradigm Signature 2s (former Stereophile class A monitors).

I do notice some coloration with the sound though. I think it's that "cupped hands" thing that I hear mentioned a lot. Almost like a "plastic" sound. Are there ways to remedy that?
 

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>>> Spent the weekend building my BIB speakers (thanks Godzilla for the help).

Enjoy! I think if you double up the back of the cabinet to reduce vibration you will reduce or eliminate the cupped hand sound. If you feel too much midrange is coming out the top continue to add stuffing in small amounts. Go to this website:

http://www.phys.unsw.edu.au/jw/hearing.html

If your computer is connected to your stereo you can play the test tones from 250hz down. These are the frequencies you want coming out the top of your BIB. Stuff your BIB until you reduce the frequencies above 300hz. I posted the test tone link here:

http://www.zillaspeak.com/bib-howtobuild.asp

Scroll to the bottom.

Godzilla

PS. How much better do these sound than the Stereophile Class A Paradigms?
 

gnugear

Member
2005-08-07 8:26 pm
Compared to the Paradigms, they image better, produce a bigger soundstage, and have deeper bass. On vocals and acoustic guitar they just shine, but on some stuff I hear that midrange coloration. I could easily live with these over the Paradigms but I'll probably hang on to them just to have something different.

They kind of remind me of electrostatics!

Thanks for the tweak suggestions, I'll try them out tonight!
 

gnugear

Member
2005-08-07 8:26 pm
I used 3/4" baltic birch for the enclosure and followed these dimensions http://www.zillaspeak.com/bib-fostex.asp

I actually built the shorter one but will probably do the larger one next.

Height was 64", width was 7.5" and the depth was 10" (internal dimensions) and the space at the bottome of the fold was 5". The face is a just a solid piece of poplar from home depot. You need the extra thickness to keep the back of the driver from touching angled panel on the inside .... and it covers mistakes. :)

Hey Godzilla, I felt my cab last night and did feel a lot of vibrations on the back. Is it best to double it up or do some kind of bracing pattern?
 
gnugear said:
I used 3/4" baltic birch for the enclosure and followed these dimensions http://www.zillaspeak.com/bib-fostex.asp

I actually built the shorter one but will probably do the larger one next.

Height was 64", width was 7.5" and the depth was 10" (internal dimensions) and the space at the bottome of the fold was 5". The face is a just a solid piece of poplar from home depot. You need the extra thickness to keep the back of the driver from touching angled panel on the inside .... and it covers mistakes. :)

Hey Godzilla, I felt my cab last night and did feel a lot of vibrations on the back. Is it best to double it up or do some kind of bracing pattern?


FWIW, some of the Fostex/Nagaoka designs incorporate interesting combinations of double layers of material / standing rib* bracing, particularly on back panels of larger horn cabinets.

* several strips of material (usually plywood) laminated to form something like an approx 2x4" rib, attached edgewise to the rear panel

They also do some curious things with enclosure side walls - overlapping layers of uneven sized pieces to achieve a thicker compound panels.

It would be interesting to see measurements of the difference in resonance distribution / attenuation for such fabrications, compared to more conventional construction.
 
Hi all,

I have done some measurements for you (and me) at the inside of my FE168EZ BIB, using Room Eq Wizard and MCE2000 electret.
My BIB is made of 3/4" plywood, dimensions as per Godzilla site (long version) and full lined with a 2mm cork.

[IMGDEAD]http://img132.imageshack.us/img132/4879/fe168ez2bj8.th.jpg[/IMGDEAD]

The first measurement is the usual setting, a small layer on the base. At the 2nd one, I added a large volume of pillow material on the base.

[IMGDEAD]http://img72.imageshack.us/img72/3619/insidethebibaf7.th.png[/IMGDEAD]

As you can see, no effect (small differences due to the electret position) on the "accident" in the 300/500 area...

I tried also to line the internal bafle (visible side), again it changed nothing but the LF... so the phenomena seems to be not so simple to explain.

Perhaps that is all about harmonics, or just vibrations transmitted thru the plywood (internal bafle ?) as you can hear medium frequencies when you put your ear in contact to the panels...

I dont know but I really don't care as soundstage and imaging are good enough and I don't have the "cupped hands" sound... only big LF resonances due to a bad room, another story... :(
 
flush mounted?

I can't see if the Fe167 above is flush mounted.

I've just been learning how to handle my small router gizmo and wonder if I should do the procedure on the BIB.

Working free hand, the flush cut I did on an MLTL came out kinda ragged. I haven't got any bearing bits.

procedure made my workspace smell liek a camp fire.

I have to find that jig in my old audioXpress/Speakerbuilder mags.

There's a way to make a template and use a bearing bit to get a nice smooth job done.
 
Re: flush mounted?

loninappleton said:
I can't see if the Fe167 above is flush mounted.

I've just been learning how to handle my small router gizmo and wonder if I should do the procedure on the BIB.

Working free hand, the flush cut I did on an MLTL came out kinda ragged. I haven't got any bearing bits.

procedure made my workspace smell liek a camp fire.

I have to find that jig in my old audioXpress/Speakerbuilder mags.

There's a way to make a template and use a bearing bit to get a nice smooth job done.

If you're talking about flush mounting a round driver like the Sigma series, it would likely be even easier to just make 2 concentric passes with a simple circle jig (i.e. Jasper jig, or shop made compass style).


With a shop made jig in MDF (the best use for this material yet!), and a router with plunge base or accurate depth of cut gauge, you can use a wide mortise bit and make a single pass for the outer rebate, and then follow with the inner cut for the driver opening.

10 minutes and you're done.
 
Re: Re: flush mounted?

chrisb said:


If you're talking about flush mounting a round driver like the Sigma series, it would likely be even easier to just make 2 concentric passes with a simple circle jig (i.e. Jasper jig, or shop made compass style).


With a shop made jig in MDF (the best use for this material yet!), and a router with plunge base or accurate depth of cut gauge, you can use a wide mortise bit and make a single pass for the outer rebate, and then follow with the inner cut for the driver opening.

10 minutes and you're done.


I did use a rabbet bit on some small round speaks. But Fostex are all square flange.


After about an hour of looking through old Speakerbuilder mags, I found the article for any interested:

It's called Easy Driver Flush Mounting by Rodney Buike Volume 32 Number 6 June 2001 page 62.

Buike may have put this up on the web someplace. If I had good tools, I would have done this already. To get the shape (that is not exactly sharp cornered, you need a router stand and shaper bit to get that fine snug fit.

I just followed an outline. Bit even with only about an 1/8 bite I was getting a lot of smoke on my particle board baffles.


Every now and again, it's fun to go throught he old mags and look at the designs.

For example I saw some 'wings' like GM described for my MLTL.

But it still looks like a stretch to accomplish for who knows what sound difference.

For the free hand work, I guess I'll just have to get a fresh bit for $6
and take an even shallower pass first.
 
Re: Re: Re: flush mounted?

loninappleton said:



I did use a rabbet bit on some small round speaks. But Fostex are all square flange.


I did refer to the Sigma series (as shown) - so far all examples I've seen are round.


......

For the free hand work, I guess I'll just have to get a fresh bit for $6
and take an even shallower pass first.

Don't waste your money on anything less than a cabinet grade carbide bit, and as large a cutting diameter as your template collar or jig will allow. For the smaller diameter bits (i.e. 1/4" or less), try the spiral upcutting bits.