Voigt vs BIB

rjbond3rd

Member
2007-01-24 2:28 pm
Resonator?! Action?!

Eeek! I have struggled with horn theory despite having lots of fine articles to read. My mother says I was dropped on my head as a baby.

Might someone be willing to answer the most basic of basic questions?

Half-wave resonator: does that mean that the length of the BIB is one-half the length of the cut-off frequency, let's call that X? Does it resonate at the cut-off frequency we're calling X, or does it resonate at X divided by 2?

Quarter-wave fundamental: isn't the fundamental the frequency we're calling X above? How can the BIB have two fundamentals? (eek, I know it can't but...)

Horn action: Yes, I am a dummy. What does it mean to maintain horn action? Does that just mean that the horn produces gain over a certain range of frequencies until the cut-off frequency?

With humility and apologies,
Robert
 
I must go back and look at some of my UK references - I thought the 1960's QWT designs had an open mouth (no restriction or port), eg Paraline, hence my confusion between the two types.

For the BIB closed cone, the driver position is to load the driver and supress resonances. Could the same be achieved by moving the driver to load the narrow part of the horn via a coupling chamber, as in most BLHs? (At the expense of simplicity of the design.)

So shortening the length of the BIB is going to raise the fundamental cutoff frequency. A dimly-lit, low energy light bulb starts to glow above my head ...

As ever, GM, thanks for answers and the pointer to the hyperphysics site.
 
I believe with the 'open cone' comment, GM's refering to a cone open at both ends, not open at one & closed at the other.

Yes, the length of the horn determines its low frequency cut off. It's typically designed to be 1/2 wavelength of the desired tuning frequency, which is typically that of the driver's Fs, so horn action occurs from that point upward, where it's always at least 1/2 wave long. The bottom octave below this is provided by QW (or TL if you prefer) loading.

And also yes, you can provide a air cavity / coupling chamber with it, although you'd obviously have to trunkate the horn somewhat because as-is it's an So=0 design, i.e. the throat has 0 surface area, which might make the coupling a trifle awkward. ;) What you'd end up with would be a normal, back-loaded horn with conical expansion.

Hope I got those right Greg?
 

rjbond3rd

Member
2007-01-24 2:28 pm
Aha! Okay, so that's why a BIB can produce tones lower than the driver's Fs. That was one key piece I was missing. Thank you, kind sir!

Horns have ruined me. It's hard to listen to boomy, boxy speakers after hearing the bass from a good horn matched to a good amp and room. (My current speakers are a German commercial variety which are merely inverted mini-BIB's with ACR-modified FE164's (I think). They should come with a warning label: Will haunt you forever.

Anyway, I've been trying to understand how they can sound so good in the bass. Thank you again!
 

gnugear

Member
2005-08-07 8:26 pm
I just purchased some Lowhter DX3 that will go into a BIB.

Will they produce more bass than the FE168 Sigmas that I currnetly have?

Also, I saw reference to a straight pipe that was better than a Voigt because the top doesn't come to a point. Can the same principle be applied to the BIB?
 
gnugear said:

Will they produce more bass than the FE168 Sigmas that I currnetly have?

Also, I saw reference to a straight pipe that was better than a Voigt because the top doesn't come to a point. Can the same principle be applied to the BIB?

I don't see why they would and more than likely won't make as much if 'cranked' to high SPLs.

I don't see why not, but you'll lose some gain BW, something you can ill afford with typical FR drivers due to their extremely limited linear excursion.

GM
 
rjbond3rd said:
Horns have ruined me. It's hard to listen to boomy, boxy speakers after hearing the bass from a good horn matched to a good amp and room.

I must admit my experience has been the opposite from having built one corner horn (a compromised Klipschhorn, a Wireless World design from the 70s) and listened to a couple of others in poor surroundings. Someday, I hope to hear some of the newer horns discussed here (or a good, old fashioned non-compromised horn) and find out what they can really do.