Terry Cain's BIB -why does it work and does anyone have those Fostex Craft Handbooks?

Breaking In

I have not done it, but I read on one forum where one guy fastens the two new drivers so that they are facing and touching each other. He wires one of the two drivers correctly, and the other out of phase. This way they don't sound like they are playing very loud, even though they are.

Sincerely,

Benjamin
 
Re: Breaking In

BenjaminWebber said:
I have not done it, but I read on one forum where one guy fastens the two new drivers so that they are facing and touching each other. He wires one of the two drivers correctly, and the other out of phase. This way they don't sound like they are playing very loud, even though they are.

Sincerely,

Benjamin

Yes that is a known technique. You check for phase using an AA battery with two leads from the speaker. In phase, cone pushes out,
out of phase cone goes in. Then wire it that way to the amp. When you mount them face to face you'll still want a sound proof box and lots of stuffing in it.

Some free audio programs like Audacity have built in tone generators.

I found some clips here:

http://www.burninwave.com/#pinknoise


Last time I did the break in I took a 30 second clip of the noise in Audacity and then let it play with VLC in a loop. I do not have any scope equipment or tone generators. This is the simplified way.
 
Well. I've been applying everything you guys were telling me. They seem to be coming around quite quickly.

When I got them they had enough stuffing in them to fill a 30 gallon garbage bag.

I took all that out and thats when I finallly started getting some real bass.

So in fear of losing my bass again. I only used a minimal amount of stuffing to try and control midrage reflection. I put a little in the bottom. A little above the speaker and a little behind and below the speaker.

I put them in a wider room closer to the corners.

Toed them back out quite a bit. Almost no toe in at all. I had to have a little or they won't image.

I have also went from KT88's to EL34's in my amp.


So far it sounds pretty good. Still not quite as good as hoped. But I thnk there is more to be had. I have a bunch of acoustical panels. I am going to mount one to the ceiling above each speaker. This should cut out 90% to 100% of any reflective sound comeing out of them. I layed them on top of the speakers just to get an idea. It was the most dramatic tweak yet.

I am hoping the panels will be the last tweak. Some one told me I would have to tweak these forever before they would come around. I had no idea.

They also seem to be warming up as they break in. I had them running for about 3-4 days 24hours a day. I couldn't take it anymore and had to turn it off. So now they get a little break in time during the day.




Nick



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G'day Nick,

A helpful idea to assist with break in is to move the speakers face to face and reverse the + and - wires on ONE of the speakers.

This will reduce the level of bass because they will be running out of phase.
Do one day like this, then swap the wires back and reverse the + and - wires on the OTHER speaker so it has a turn playing backwards for a day.

Some blankets thrown over the top might be helpful too.

Cheers,

Alex
 
I have the Coral 4a-70 details here...

A fellow forum member ran them and got these figures, I hope it is helpful!

Hi Jon
I picked up a few recently and plugged into a Dayton woofer tester. Haven't worked out how to post the impedance graph image here, specs are
FULL RANGE SPEAKER
INPUT POWER 40 W MAX.
* Manufacturer: CORAL
* Model: 4A - 70
* f(s)= 121.10 Hz
* R(e)= 6.90 Ohms
* Z(max)= 27.10 Ohms
* Q(ms)= 2.455
* Q(es)= 0.838
* Q(ts)= 0.625
* L(e)= 0.19 mH
 
coral 4A-70 project - photo of boxes 1

hi,

went to visit bib's and took snap; 25mm black stained ply (donated) awaiting routing of driver hole; stands to bring driver to ear height in conceptual stage...

so, as it was suggested earlier that the mouth should face the floor to load the line - is the distance of the mouth from the floor more important than the distance of the driver from the floor?

thanks,


adam
 

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A weird idea ...

From another thread ... considering up/down firing drivers, and then omni-directional speakers ...

developing the omni-directional theme ...

What if one were to configure an internally-partitioned tower as shown?
Let's dub it the "Quad-BIB" - the idea being that 4 BIB-style compartments standing together?

(Leave aside the size implications!)

If one were to use (say) WR125ST's, and kept to the calculated L and Z, what would the effect be (sonically) in squashing the X-section to make a reasonably-sized and aesthetically-pleasing compound cabinet?

cheers

Doug
 

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Re: coral 4A-70 project - photo of boxes 1

arustyrednail said:

so, as it was suggested earlier that the mouth should face the floor to load the line - is the distance of the mouth from the floor more important than the distance of the driver from the floor?

Yes since without good pipe loading there's no driver protection below ~0.707x its Fs.

GM
 
coral 4A-70 project - sound absorbing stuff

hi,

thanks, gm;

and in other news:

by happy coincidence met an aquaintance who has returned to town and now works for www.allproof.co.nz - purveyors of all sorts of sound attenuation panels, foams, rubbers and associated materials.... applications for factories, studios and listening rooms.

had been looking at overseas suppliers of various products, very pleased to have an auckland contact for that sort of thing - Kerry Adams is the chaps name, music production background, audio enthusiast.

should make tuning the bib a little easier with a range of panel damping and stuffing stuff to try,

thanks,

adam
 
Re: Re: A weird idea ...

GM said:


Sorry, not able to visualize it in 3D.

GM

The diagram was intended as a plan view of 4 BIB's stacked together - "marching in a circle" as it were.

The inspiration came from consideration of mention made by Dave (@P10)
in this thread:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=145589,
"Sonotube FR speakers".

Dave made reference to EPI miniTowers, which were omni speakers, with a driver on each face.

My comment arose thus ...

Clear?

The implied benefit was an omni arrangement with good bass.

Doug