Rear-Loaded Horns ("Scoops") Impedance response

[Brian Steele]

Just a quickie - what does the impedance response of a well-designed rear-loaded bass horn really look like? I've seen some theoretical response curves online that look like the classic multiple dip and peak response I expect, but then yesterday I measured the impedance response of one actually in use in a club here (one that the club's quite happy with, btw) and looks like what you'd expect from a classic simple vented alignment...

 

[1audiohack]

What did you see/measure?

Can you post a view of the measurement?

 

[Brian Steele]

What did you see/measure?

Can you post a view of the measurement?

Unfortunately I didn't keep a copy of it (I can take another measurement in a day or two, if necessary), but it was the classic "double hump" impedance response you'd expect of a vented alignment, along with the rising impedance at higher frequencies caused by Le.

 

[GM]

And why I call scoop bins BVRs [big vent reflexes].......... A proper BLH will have the three impedance peaks of a band-pass.

GM

 

[Brian Steele]

And why I call scoop bins BVRs [big vent reflexes].......... A proper BLH will have the three impedance peaks of a band-pass.

GM

Which leads to the question - if these things have the impedance response of a simple vented alignment, this suggest that their response is likely that of a simple vented alignment, so is there any reason to use them instead of a simple vented alignment?

 

[GM]

Not really, yes, being a ~1/8 horn segment they have about a 1/2 - 1 octave of up to 6 dB gain to provide a lot of mid-bass 'slam' like a properly aligned Karlson K15 and with a similar roll off to a 40-50 Hz Fp. Hardly HIFI, but fine for small bands, etc..

GM