imaging and stage depth

[peterr]

Hi All,

I have been using a pair of Fostex 168ESigma BIBs for the best part of a year now and generally I am quite happy with them.

If you read the giant BIB thread you will see that is almost exclusively about low frequency reproduction and how well the BIB does this. I agree they do very well in this respect but I find I am less impressed with what they do in other areas. Especially imaging and stage depth (of MY pair) are not as good as I hoped. I built them as a first entrance into the world of full range drivers so I am unsure about what is BIB related and what isn’t.

I have experienced a lot with placement and damping but although it makes a difference it doesn’t bring what I am looking for. Is this something others have experienced too? And if so have you been able to improve things?
When I started this project I thought (perhaps wrongly so) that full rangers generally image very well. Is this true at all?
Would a different box (MLTL?) be any better at it?
I really hope somebody can shed some light here.
Thanks,
Peter

My BIB:

[Scottmoose]

Well, looking at the picture, you need to get them positioned right. For a start, they're corner horns, so they need those to work properly. Imaging is very much a strong point with these cabinets in my experience, so it could be that there's something wrong elsewhere in your system or room.

[peterr]

Originally posted by Scottmoose
Well, looking at the picture, you need to get them positioned right. For a start, they're corner horns, so they need those to work properly. Imaging is very much a strong point with these cabinets in my experience, so it could be that there's something wrong elsewhere in your system or room.

Thanks for the quick answer, Scott. I have tried them in the corner but if I do that they are 4 meters apart and I get a big empty hole in the middle.

[Scottmoose]

I hate to say this, but you might have picked the wrong boxes for your situation I'm afraid. Therein lies the problem with speaker design / choosing what to build: there is no one-size-fits-all solution, and everything comes into play -system, preferences and the room (particularly the latter in the case of something like a corner horn, which uses the room as part of the cabinet).

You might want to look at one of the double horn cabinets like Chili. Currently the curved front version is not on the site, but drawings have been completed. For the 168, the throats will need changing to 0.75in long (thickness of the build material) and 0.5in deep (each) front-back. Won't go as low, but it'll probably suit your room better.

[rdf]

Hi peterr. If that picture is any indication I'ld start by moving the equipment rack. Another experiment is checking the impact on imaging of moving the speakers forward of the rack. In my experience the strong interference and reflections caused by having so many obstructions between listener and speaker will be a major factor.

[hm]

Hello,
or it might be:
to much mids 300 - 400 Hz coming
through the horn to late with to much area,
this can be a lost of soundstage.

[Scottmoose]

There shouldn't be any coming out. If there is, the cabinets haven't been damped right. The bend attenuates a lot, but not everything. As a general rule, the front of the internal baffle & one side-wall (1st half of the horn) need lining with damping material from the top to roughly 6in below the driver. And the internal base needs a nice layer of the same. Final tweaking can be done with a pennant of material hanging down the 2nd half of the horn flare.

[kirbyt]

I recently made some bibs housing fostex 168 sigmas and my initial impressions are quite good, especially given that I've heard these drivers need a bit of time to loosen up, i only have maybe 60+ hrs on them right now. My cabinets are not in an ideal room (large open area in my house) nor right in the corners (right tight to the wall though) but I find the imaging to be pretty decent. Previous to the bibs, I've been listening to klipsch cornwalls, had some coral flat 10's (placed in cabinets not well suited so no real comparison here) some hammer dynamics and my tannoy monitor golds (which I have not listened to for awhile) all on the same equipment. My bibs are based on the latest measurements on the bib sight And I have supra baffles, as well my front baffle of the cabinet is two layer which pulls the driver almost completely out of the horn throwt. I dont know if this helps at all but I thought I'd share it.

[Godzilla]

Those look really nice! I feel BIBs produce a large and involving image. But i also realized when i moved my BIBs from one room to another that imaging suffered due to very bad room acoustics. Treating walls with sound absorbing materials prevented major echoes and minimized a lot of wall reflections. Maybe you have some room issues that might be a problem for any speaker in that space. Since the BIBs fire a lot of sound upward you may consider treating your ceiling above the BIBs or the side walls where you can. I think once you figure how room accoustics are making things worse you can then focus on making it better... and getting back your imaging!

Godzilla

[ScottG]

Originally posted by peterr

I really hope somebody can shed some light here.
Thanks,
Peter

My BIB:

2 Things:

1. They are way to close to your front wall. This seems to be a pertinent thread to your dilemma:

http://www.audioasylum.com/cgi/vt.mpl?f=hug&m=130282

2. Make sure there is no "stuffing" near the driver itself. See my #19 post here:

My Fostex FE 108EZ project, Part 2