Terry Cain's BIB -why does it work and does anyone have those Fostex Craft Handbooks? - Page 109 - diyAudio
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Old 9th August 2006, 11:54 AM   #1081
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Hi Zek

You're not doing anything wrong. I deliberately tuned them somewhat below Fs, to a 53Hz 1/4 wave length as you observe, to squeeze a bit more LF out of them. Tuning a little below Fs is fine, providing you don't go too far: 0.707 Fs is the limit, but I really wouldn't want to try going that low with them -the midbass will vanish. 10-15% below Fs is my limit, depending on the driver. This was the best compromise I came up with for the Monacors. Works very well. If you prefer, you can tune to 60Hz of course.

Best
Scott
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Old 9th August 2006, 12:57 PM   #1082
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Hi zek
I have the length you have simulated. Scottmoose gave me these dim's a while ago.

It works fine in my room (50sqm) without sub. I have used a sub before but got tired of matching them with main speakers. My room is impossible with normal boxes.
This BIB, I am very satisfied with but will try more expensive drivers soon.

width 12.7 cm

depth 26.2 cm (with internal baffle)

height 142.5 cm

Speaker 64.5 cm down from closed end

All these are internal measures.

Good luck! Peter
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Old 9th August 2006, 01:30 PM   #1083
zek is offline zek  Serbia
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Thank you Scott & Peter,

It seems that both sims work well with this little driver.

Peter,
your width/depth ratio seems too high - it is recommended D= W*1,41 + internal baffle, but your's is about ~2
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Old 9th August 2006, 01:46 PM   #1084
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Hi zek!
Yes I forgot to mention. I had them cut in a furniture factory and they screwed it up plus I did some mistakes when recalculate it from inches.... I thought ,what the heck, build it and see what's the outcome.
It works ok as far as I'm concerned. Maybe that's why I have some avesome bass from tiny 10 cm speakers. I don't know but the ye old rule of bigger cabinets are better....
Of course I have not heard one with correct dim's.

Build the the correct one and give us some of your impressions.

Regards Peter
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Old 9th August 2006, 02:33 PM   #1085
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As Terry Cain said to me after I told him about the first BIBs I built, 'displacement has merits with horns and their variations: Bigger is Better and Longer is Stronger.'

Greg's explained why this is the case earlier in the thread. Either way, big cabinets rule. I include MLTLs, ML TQWTs and a few other big BR designs in that, because they have enough Vb to do the drivers justice. No point piddling about with these little mini-monitors, except for sticking on a desk, or keeping in the office.
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Old 9th August 2006, 03:23 PM   #1086
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“Bigger is Better and Longer is Stronger.” My wife always says something similar… just not regarding speakers.

As for little mini monitors… I recently built a pair of small sealed cabs with 3” TB’s in them. I’ve built these before (years ago) and really enjoyed them. But after listening to larger speakers like my Straight Pipe (Fostex 127e) and sealed (Pioneer/Piezo) the little TB’s don’t seem to do it for me these days.

Since the giant killer SI amp has been my favorite little piece of gear (totally unmodified) the speakers need to be pretty efficient. Fostex and Pioneer B20 work fine but the little TB’s struggle to get loud enough for late night listening. I find the dial on the SI amp needs to be set between 2 or 3 o’clock whereas using the other speakers it’s set between 10 and 11.

I’ve still not built my BIBs! One pair sits in my garage half finished (Fostex 168S) while the other (TB 4” Bamboo) sits in the basement, boards leaning against the wall. Oh, and a more conventional box for the 127e is sitting unglued on my workbench.

The 3” TB’s (315 aluminum cone) are tizzy on top, need power, drums seem very recessed and sound smallish and overall in a sealed box, they lack bass. Powered sub fixes the bass but not the other shortcomings. I wonder if the 817 3” sounds better? And the 4” Bamboo is a perfectly fine driver that works much better with the SI amp.

Peace,
Godzilla
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Old 9th August 2006, 04:08 PM   #1087
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Hmm, this gets me thinking, since I have a deeper box, can I move up the speaker a bit? Would that would give me some stronger/deeper bass? And maybe less mids coming out from mouth?
Also I have found camping mats that would be ideal in speakers. They consist of soft rounds cut in half and are hollow in between the half rounds. Gives a very irregular surface like Deflex pads. Pardon my English, but I will take some picture and put it here later. I Will give these mats a shot in my BIB's.

Cheers
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Old 9th August 2006, 05:17 PM   #1088
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Greets!

Max gain and BW is when a pipe/horn is end loaded, so it will increase the LF and all its harmonics. Remember, the lower the frequency, the wider its BW, ergo to reduce the higher frequency amplitude, move the driver towards the mouth to reduce the LF gain, though there's a point of diminishing returns once the acoustic load on both sides of the driver is ~equalized. Beyond this point it turns into an increasingly narrow bandpass (BP) alignment. Rarely do you get to 'have your cake and eat it too' in audio.

I assume you're referring to the 'eggcrate' style since it looks like the backside of a styrofoam egg container: http://www.allegromedical.com/foam-e...ad-191438.html

GM
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Old 9th August 2006, 05:37 PM   #1089
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Quote:
Originally posted by Godzilla
“Bigger is Better and Longer is Stronger.” My wife always says something similar… just not regarding speakers.
haha

Quote:

The 3” TB’s (315 aluminum cone) are tizzy on top, need power, drums seem very recessed and sound smallish and overall in a sealed box, they lack bass. Powered sub fixes the bass but not the other shortcomings. I wonder if the 817 3” sounds better? And the 4” Bamboo is a perfectly fine driver that works much better with the SI amp.
Also, I have worked a little on my 871 BIBs. I have 1 more coat on the BIB and a couple coats of paint on the suprabaffle, but 2 nights ago I used some tie-downs and listened for a while using my tube amp. There was no stuffing in the enclosures nor was the grill cover fabric behind the driver, but I was suprised by the gain increase. I was using my S-5 electronics tube amp ~8watts, and that was plenty. Bass was much better than my aperiodic enclosures that I built for them, but it was obvious there was a lot of frequencies coming out the mouth.

I'll post some pictures later this afternoon of what they look like now.


Thanks,

Josh
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Old 9th August 2006, 05:49 PM   #1090
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I wondered how long it would be before the minds went to work. You wouldn't catch me thinking of such things. Oh no. They have never entered my mind, at any time.

Peter, there's nothing wrong with your English. I feel quite humbled when reading the posts of people such as yourself, for whom it is not a first language, describing things so lucidly. My only second language is a bit of latin.

As Greg says above, I wouldn't advise shifting the driver. It's positioned where it is to supress a harmonic, and also to reduce the dip in the midbass as much as is possible with this sort of enclosure. You might want to try increasing the stuffing in the point above the driver, which should help kill some of the unwanted HF. Although in a positive tapered pipe / horn like the BIB, I'm not sure if the usual QWR rule applies: the point of maximum velocity for the LF occurs at the terminus, and closer to the sealed end with increasing frequency. Greg?

Regards
Scott
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