imaging and stage depth

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:
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Scottmoose said:
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.
 
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

Member
2004-06-21 8:04 am
big smoke
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.
 
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

Member
2006-12-04 3:31 am
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.
 

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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

Member
2003-02-04 12:23 am
US
Thank you all for your comments.
It gave me a few directions to look into.

Rdf:
I did try moving them in front of the rack and it does help a little but not a lot.

Hm and Scottmoose:
Damping might be part of it for sure. I have experimented quite a bit but noticed more impact on other things than soundstage but I will certainly (re)do some experiments.

Kirbyt:
Nice ones!
Your situation seems rather similar to mine, so I am happy to hear they work well for you.
Did you try them without the suprabaffle? What are the main effects of adding one?

Godzilla:
Room acoustics certainly could be part of it. My living room where these are is quite big, about 4x10m and has a large open connection to the top floor, which adds a space of roughly the same volume. The walls are almost all covered with plasterboard over insulation foam.
The ceiling is relatively low (2.3m) and has wooden beams across it at about every 30cm. The floor is massive oak again on top op insulation foam.
I wouldn’t know how to change this I am afraid but thoughts are always welcome

ScottG:
I will try your experiments and see what they bring.

This quote from the linked thread sounds a lot like what I experience:

I bet another thing occured:

..centered imaging remained about the same (maybe better, maybe worse - likely moved forward near the plane of the speakers), but off center imaging probably sounds a lot closer to the speakers (perhaps even as if its comming from the speakers).

The cleaner vocals was likely a product of removing ambiant information from the track and leaving just the vocals/instruments. (..kinda like scrubbing out the sound stage.) My guess is that there would be very little change for tracks with close mic vocals and little or no hall-sound/reverb (..possibly a little better).

The funny thing is that topic seems to be restricted to the fullrange forum. The other so-called "progressive" forums dealing with "real" speakers never seem to talk about this (..except for the question "what happened to imaging depth?").
 
Scottmoose said:
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.

Well, I have done a lot of experiments the last few days and things have certainly improved.
I have played around mostly with damping and placement and especially Scott G's advice about not stuffing near the driver gave good results.

But.
Like Scottmoose suggested in the above quote a Bib might not be optimal in my case. In the end I really really prefer the boxes freestanding and not just because my equipment is in the way (right now they are about 1m from the back and side walls).
And Bibs, designed as they are to be in a corner, might be improved upon.

So my question is: What to build?

I want to keep the Fostexes and I want them to be freestanding,
I play all kinds of music from solo Flamenco guitar to Jazz to Large Symphonies to Rush to Opera.
I looked at the Chili and I liked what I saw
or a MLTL?
or....?

Any advise is very much apreciated!
Peter
 
Scottmoose said:
I hate to say this, but you might have picked the wrong boxes for your situation I'm afraid.

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.


peterr said:
Room acoustics certainly could be part of it. My living room where these are is quite big, about 4x10m and has a large open connection to the top floor, which adds a space of roughly the same volume. The walls are almost all covered with plasterboard over insulation foam.
The ceiling is relatively low (2.3m) and has wooden beams across it at about every 30cm. The floor is massive oak again on top op insulation foam.


Hi again,
After a short email exchange with Scott and Dave I now have a set of drawings for Chili and for Curved Chili (KimChi). Both of these are for the Fostex 167.
I am seriously looking at building something like this but in my case it would be for the 168eSigmas.

The whole reason for making these would be the fact that the Bibs I have now are (like Scott said) not optimal in my room. I can’t put them in the corners because it puts them too far apart, I actually get the best sound with them freestanding (except for bass of course).

I don’t want to make the same mistake twice so before I spend money (and time) on this I would like to get a better understanding of what I can expect.
I hope to get some answers to the following:
1. Can anyone describe or at least predict what the difference in character between Bib and Chili and between Chili and Kimchi will be?
3. Will they need bafflestep compensation if I use them freestanding?
4. Scott do you have a FR simulation for the 168eS? Is it very different from the 167 one?
5. Is the difference in port length the only change compared to the 167 version?
6. Will it need a series R (as has been suggested on another thread)
7. From what I have seen the curved versions are identical to the non-curved ones in all other dimensions. Does this mean that I can build the Chili and turn it into a Kimchi later simply by mounting a set of curved add-on pieces to make up the difference? (According to Dave a curved 168eS version doesn’t exist yet)

Sorry to bother you with all these (no doubt stupid) questions but I hope you can help me decide what to do,
Peter
 
It sounds like you are moving on, but I thought I'd share some observations. All the fullrangers I've tried have imaged incredibly well. I don't worry too much about imaging (it doesn't exist much in real life in my opinion, but rather is an artifact of the recording process). My Hemp BIB's are freaky in L-R imaging, but they lack front to back soundstage depth. I'm amazed with fullrangers, as all other speakers of heard develop a hole in the middle when placed too far apart. My BIB's are in the corners of the long wall in my room, and the center image is solid as can be. They image better any multiway I've heard (which range from overly focused and tight to the infamous six foot wide mouths to completely discombobulated). I suspect a coax would be really, really good too, I just haven't had experience with one. I'm salivating over the big new KEF's. I need to go to law school and get a real job.

Have you experimented with toe in? Mine are toed in so the axis cross in front of me. They seem to work fine toed out too, but my wife sits way out of the sweet spot in her chair (I'm selfish and she doesn't care). When they are over toed, the sound way out of the sweet spot is far better. When they are under-toed (axis crossing behind me) listeners outside of the sweet spot hear way too much of one channel and no hf from the other. Toe yours in and out. Make sure everything is symmetrical too. Then, make sure you're not contending with some weird hf reflections (have you got a coffee table?). It's unlikely to be the problem, as fullrangers are so directional they eliminate much of that concern, but it's worth looking into.

Finally, I don't know what to do about my lack of soundstage depth, but I don't care too much. A couple of weeks ago I listened to some B&W 802's run by Classe amps and sources, all hooked up with MIT wire. The image was crap. I'm not complaining.

pj
 
peterr said:
7. From what I have seen the curved versions are identical to the non-curved ones in all other dimensions. Does this mean that I can build the Chili and turn it into a Kimchi later simply by mounting a set of curved add-on pieces to make up the difference? (According to Dave a curved 168eS version doesn’t exist yet)

If the port change is all that is needed then i'll just add the note to the drawings... i need to consult with Scott to see how this differs from a slightly different much earlier pass at the 168eS. The BVRs have proven to be quite versatile, be nice to keep the cabinet count down.

dave
 
pjanda1 said:
My Hemp BIB's are freaky in L-R imaging, but they lack front to back soundstage depth.

I have a set of Fonkens here that image very well (stock drivers). I have another set with treated drivers and they make the 1st set sound flat & 2 dimensional -- they make the back wall fall away.

dave
 
planet10 said:


If the port change is all that is needed then i'll just add the note to the drawings... i need to consult with Scott to see how this differs from a slightly different much earlier pass at the 168eS. The BVRs have proven to be quite versatile, be nice to keep the cabinet count down.

dave

It would be great if you/Scott could indeed confirm this.
At the moment I feel a little too much in the dark about what to expect compared to the Bib. I want to build it but I hope to get some confirmation that it would be worthwile beforehand.
Peter
 
peterr said:


It would be great if you/Scott could indeed confirm this.
At the moment I feel a little too much in the dark about what to expect compared to the Bib. I want to build it but I hope to get some confirmation that it would be worthwile beforehand.
Peter

We will. You are the 2nd person in need of this cab.

These seem to much prefer being pulled out into the room, they will not go down quite as far, but will have a lot less ripple. There shouldn't be as much work tuning them.

The curvey ones are more focused, the curve acting to integrate the driver & the 2 mouths and the curve shape improving the wave launch (the output wants to be a spherical bubble and the curve helps a high aspect ratio more closely achieve this goal. You see the same on the back of the A166, A126 and the Frugel-Horn.

dave