Terry Cain's BIB -why does it work and does anyone have those Fostex Craft Handbooks? - Page 2 - diyAudio
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Old 18th October 2005, 03:34 AM   #11
GM is offline GM  United States
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Greets!

Right, the room dominates down low and let's not forget that we are primarily amplitude based animals, so between a falling hearing acuity with decreasing frequency and basically keying off the peaks, the response can be quite ragged and still sound fine. Good thing, or we wouldn't be able to listen to a typical truncated horn design or wide BW audio in a typical room.

GM
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Old 18th October 2005, 04:21 AM   #12
dmason is offline dmason  United States
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Thanks, Greg, that makes all the sense in the world, and explains the balanced sound we are getting using a 168Sig in one of these. The 168 measures real ratty from 5KHz up, but, after the requisite thousand hour cook time, it is truly a music maker.

I will be very interested to hear a BIB using a driver far more suited to this load. Offhand, the Supra 165 appears best. Correction, linear Xmax is actually 6mm. Bigga id betta! I placed an order for a pair of 165LB tonight. SHould be here next week.
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Old 18th October 2005, 06:36 AM   #13
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Would FE208 sigma work better? I was thinking of using it in a similar design (see Make the room part of the horn). I thought about it without seeing anything similar before. The idea came to me by thinking of simply unfolding the back loaded horn recommended on Fostex website and place it in a tall enclosure. Then place it close to the ceiling and use the corner as the last section of the horn.
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Old 18th October 2005, 08:43 AM   #14
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Quote:
Originally posted by Michael Speaker
Would FE208 sigma work better? I was thinking of using it in a similar design (see Make the room part of the horn). I thought about it without seeing anything similar before. The idea came to me by thinking of simply unfolding the back loaded horn recommended on Fostex website and place it in a tall enclosure. Then place it close to the ceiling and use the corner as the last section of the horn.
I doubt it. That Q of the 208ESigma is very low -too low for this kind of load I think, though you could artifically raise the Qms with a little series resistance. I think, if you went for an enlarged one, of the Fostex drivers, the 207 would be the best bet. Your reasoning seems correct in the unfolding of the horn, though I wouldn't angle the mouth forward, I'd either keep it pointing straight up, or perhaps angled slightly backward as Terry suggests.

Martin, that's all very interesting! Looks like you've cracked it (again)! I know you've been wary of adding updated worksheets to your site for a while due to the less-than honest sorts -I don't blame you! Any thoughts about a possible future public release (when they are ready of course)? I know you licence the technology / worksheets to Bob and probably some others -perhaps you could make some kind of charge for selling the sheets to the home user or something like that? Perhaps do something like Bob does via paypal or an equvelant, or even via snail-mail. You might be able to put up different packages for instance, similar to how you have them at present, but in a charged service -a set of sheets for TL, another for horns etc etc and perhaps an overall package price, while either leaving the existing sheets available as they stand on the site, or even removing them. I know this method has problems too, but it's just a thought -I've been trying to think how you could get some decent compensation for all your work over the past few years. I know I'd cheerfully pay for the lot, and I'm sure that many others here would do the same.

Dan -that's a 6mm Xmax for the Supravox? I like the sound of that -should be onto a winner there, and I understand those drivers have a good reputation amongst those who have heard them. I'm going to complete my boxs temporarily with the FFs I have (might as well try it out); I'd be very interested to hear how the Supravox's compare to the Sigmas. Whichever you reckon seems to work best, I might go for. My room is similar in size to yours, so this should be good. My bet is the Supravox with it's higher Q, though the 62Hz Fs might mean it's going to be tuned lower than it's comfortable with in these pipes. Oh yes, I'll let you know of any other design[s] I can come up with for them later.

Regards to all
Scott
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Old 18th October 2005, 09:50 PM   #15
paba is offline paba  Canada
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Default Fostex Craft handbooks

The only place i've seen them on the web is with AUDIO SHOP EIFL CORPORATION (Japan)

click here and scroll down half way...
http://tinyurl.com/d5cr8

but you should check with the store if they still have it, web pages go old and don't get updated sometimes.

paba
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Old 19th October 2005, 01:37 PM   #16
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If you contact them, let us know if you hear back. I had contacted them about some drivers a short while ago and never heard back. However, I had better luck when I first contacted them a year or so ago.
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Old 20th October 2005, 10:39 PM   #17
scottw is offline scottw  United States
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Hey,

Quote:
Originally posted by Scottmoose

Never neutral, and they've got a heavy character, but they do some things very well, I have to admit.

Could you elaborate on this a little for me?


You got 28ish Hz from a 166e?


Thanks,

scottw
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Old 20th October 2005, 11:47 PM   #18
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Default Re: Terry Cain's BIB -why does it work and does anyone have those Fostex Craft Handbooks?

Quote:
Originally posted by Scottmoose
Clearly, it's not the fault of Martin's software: his MathCad worksheets don't lie, though they don't take room-gain into account. So it must be what we (or I!) am / are inputting into them.
If I understand correctly, they also don't handle dissipative
loss. After building maybe 50 rear loaded designs over the
years, I have concluded that undamped lines behave as
predicted, but not usually as I want. When you start damping
them out with stuffing or lining or whatever, the characteristics
relax and you have a lot more leeway in the specifics of the
dimensions and so on. Damping (or lack of) also can be used
to compensate for room character and placement.

That's the good news - that anybody can play with the damping
or anything else to improve the sound. In my conversations with
Terry I see that like myself he very much favors experiment -
he tries lots of things and some of them work out.

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Old 21st October 2005, 12:12 AM   #19
MJK is offline MJK  United States
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Quote:
If I understand correctly, they also don't handle dissipative
Nelson,

Actually the MathCad worksheets account for the damping provided by Dacron fiber. You can define the amount and location of fiber in the line. Calculated results correlate very well with measurements.

I also like to experiment and try a lot of things to see how they effect the response, but I choose to do it analytically and only build one speaker design. This is extremey fast and efficiently produces an optimum enclosure that meets my initial design goals. In one evening, I can look at many different designs and down select to the one or two most promising ideas. These ideas get refined even further to determine which design I want to finally build.

I learn more with each design and am continuously improving the calculation methods. Final tweaking is done on the finished speaker by listening, but this is typically only pulling the last little bit of performance out of the design.
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Old 21st October 2005, 10:00 AM   #20
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Quote:
Originally posted by scottw
Hey,

Could you elaborate on this a little for me?
You got 28ish Hz from a 166e?
Thanks,
scottw
Well, they do some things very well. Imaging is usually good, and they are subjectively a very fast sounding speaker, as you'd hope from single drivers anyway. With regard to the bass -yes and no. Say rather I got 28Hz out of my room. These things have to be pushed right against a back wall or into corners to work, for reasons Martin has explained in a previous post (and his reasoning seems likely to me -nobody else has ever explained how / why they frequently work well in practice). How low you go will rather depend on how large your room is. I got a usable 28Hz, anything over 30Hzish was loud and clear. The FE166E is not an ideal load though -its Q is too low. These were just an experiment I roughed up (Terry asked if I'd ever measured a pair, and I told him no, but I would rough some up and see what they were like).

I've got a better-built pair in the works currently, but I'm waiting on drivers. The best of the Fostex 6"-7" range for the load would be either the FE168ESgima, or the FE167E, which have a higher Qts than the FE166E. That said, the FF165K has the highest mechanical Q of the lot at 10.92 I believe, so as I have a pair, I might try those -however, that might be a dead end as its overall Q is very low however at 0.20. That might be fixable with some series resistance to boost the Qes though. The Supravox 165 with its higher Q Dan is trying out ought to be a the best match of all, though my only (slight) concern is that it's high Fs will mean the pipes as they stand are tuned way too low for it, and might push it outside of its operating parameters. it has a 6mm Xmax however, so it could be happen enough; a try it and see situation.

You ask about the character of the cabinets. Well, they will always have a dip at circa 100 - 150Hz -that's a consequence of the driver positioning, and there's nothing you can do about it. However, as they drive the room's vertical as well as horizontal modes, this is often flattened out by the boost you get from the vertical mode in this region, so the dip is not as pronounced as an anechoic simulation might suggest. (I'm guessing that's the reason, but I don't think I'm far off: 8' will give you gain at around 135Hz) However, this is really the key issue: the lower you go, the more you are listening to your room, activated by the cabinet, rather than the speaker driver itself, so what character you hear will be dependant on your own room, rather than the speaker itself -more so than any other design I can think of, off-hand.

As for the rest -there's ripple, more than other cabinets, like Martin's Project 2 ML TQWT or Bob Brines FT1600 Mk2, but they have somewhat different priorities; they're a cheaper and simpler construction (not that the other two are complicated), and they go lower. Without BSC or added series resistance, they're also more sensitive, so will match well to low-power SET amps, and allow you to play rock or complex orchestral pieces at window-rattle levels with such amps; not something you'd get very often.

Cheers
Scott
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