increasing upper rolloff corner

Cheers!

Referring to the formulas of Keele's low-frequenzy horn design using thiele/small driver parameters the upper rolloff corner is given due to the effects of driver moving mass:

fhm=2*fs/Qts

Is this the same for mid-range horns?
My thought was to increase the drivers fs in order of a small as possible rear chamber to get an extendet operating range du to higher upper roll off corner. (ie: 18Sound 8NM610, RCF MR8N301/MR10N301) Does this work with every driver?

gzg

thx _djk_, already know these papers....
Am I right, that only the free air resonance frequency of the driver and not the resonance frequency of the whole system (driver+rear chamber) has influence on the flh upper rolloff frequency?

what about the above mentioned drivers including a sealed rear chamber? which thiele/small parameter do I have to use to simulate them in a flh with hornresponse and what value would be correct in case of the rear chamber?
Anyone experienced with these drivers?

In the case of the drivers listed above that have chambers, it is the system resonance and the Qtc that dictate the mass corner. It should give the same result as the free air Fs and Qts.

You would have to contact the manufacturer of the driver to either get the enclosed rear volume, or the free air Fs and Qts of the driver. You are probably not going to reactance annul a mid horn design anyway, so just stick in a number and see what happens.

Could a Linkwitz transform be used to reduce qts and make the upper corner move higher up? I've previously asked about using these in bandpass horns to make them go lower in singles by increasing it but the answer was that the circuit wouldn't handle enough power and would waste too much energy, surely in a midrange horn where the power levels are lower this could work.

Fhm is the beginning of a 6db/octave rolloff. This can be balanced (to some extent) by the horn's narrowing dispersion with rising frequency to make the on axis response more flat. The power response still falls off, but this isn't a problem, it's the sensitivity which matters.

Fhvc (12db/oct) and fhc (18db/oct) are more serious extension killers. The 6.38mr3 has fhvc above 7khz. A 65cc front chamber will get you up to 4.5khz, this is where a good phase plug comes into it.

Kieran

doober wrote: Fhm is the beginning of a 6db/octave rolloff. This can be balanced (to some extent) by the horn's narrowing dispersion with rising frequency to make the on axis response more flat. The power response still falls off, but this isn't a problem, it's the sensitivity which matters. Fhvc (12db/oct) and fhc (18db/oct) are more serious extension killers. The 6.38mr3 has fhvc above 7khz. A 65cc front chamber will get you up to 4.5khz, this is where a good phase plug comes into it. Kieran

Thx Kieran! Now a lot of things seem to be clearer!
So, does it make sense to choose a driver with a low mass corner frequency and a high voice coil inductance corner frequency and squeeze the usable passband between these two in combination with a 6db/oct rising midhorn response to get it flat? (low horn cutoff = mass corner, high horn cutoff = inductance corner)
gzg