I was interested to note that Jeff Listed a( either or) tweeter option for the revolution design ( the Be version and the textile dome ) Is this common ?
When I looked at the output of the drivers they were similar - so it made me wonder if- with in -a tweeter Family with similar outputs what should I expect ? are they essentially interchangeable in a crossover design ?
If yes then what are the key measures to look for ?
If not what is the dis-qualifier?
In the case of the revolutions are there others - in the family - that would also work well ?
When I looked at the output of the drivers they were similar - so it made me wonder if- with in -a tweeter Family with similar outputs what should I expect ? are they essentially interchangeable in a crossover design ?
If yes then what are the key measures to look for ?
If not what is the dis-qualifier?
In the case of the revolutions are there others - in the family - that would also work well ?
Impedance curve for the (closed box/sealed chamber) tweeter, as well as same frequency response… at least from Fc to at least 2 octaves above…
interestingly both share a a impedance bump at about 650hrtz but the fabric dome (sb 29sdac -coo4 has approx twice the amplitude - how am i to understand this - is it inconsequential ?
The impedance peaks at resonance are different, yes. The different Q values correspond to that. But the crossover is likely well above the resonance peak, so not really pertinent.
If you look at the response curves, as noted earlier by AllenB, there are slight differences, mainly above 10 kHz.
I haven't heard either version, so can't comment on SQ.
If you look at the response curves, as noted earlier by AllenB, there are slight differences, mainly above 10 kHz.
I haven't heard either version, so can't comment on SQ.
SO if i am to understand this -one would compare the impedance curve ABOVE the crossover point and if these reasonably match- the tweeters are candidates for substitution - is this correct ?
I see that frequency response is also considered - (Two octaves above cross ) Jeff seems to use the BE version to correct a slight flaw in the textile tweet response - baring a complete re-work of the crossover this seems like a useful tool
I see that frequency response is also considered - (Two octaves above cross ) Jeff seems to use the BE version to correct a slight flaw in the textile tweet response - baring a complete re-work of the crossover this seems like a useful tool
Variations in impedance can vary the interaction with the crossover and result in additional response variations.
The impedance looking back into a first order crossover increases at lower frequencies whereas looking back into a second order filter it decreases.. so there may be somewhat less interaction for the second order filter down towards the resonance impedance peak.. The crossover also doesn't do much at much lower and much higher frequencies.
Simming will give you the answers in more detail.
(Some would mention the impedance's effect on the amplifier, but if anything this is secondary, and possibly insignificant. Unless we are talking about a higher output impedance..)
The impedance looking back into a first order crossover increases at lower frequencies whereas looking back into a second order filter it decreases.. so there may be somewhat less interaction for the second order filter down towards the resonance impedance peak.. The crossover also doesn't do much at much lower and much higher frequencies.
Simming will give you the answers in more detail.
(Some would mention the impedance's effect on the amplifier, but if anything this is secondary, and possibly insignificant. Unless we are talking about a higher output impedance..)
I gave a somewhat brief answer but didn’t go into the details.
The summary I gave was the result of my investigations; on WHY the soft dome was a suitable drop-in replacement for this particular speaker, which I theorised, and then built to serve as a reference 7L speaker.
2020 Jeff Bagby Revolution Mini SD
Context is important- Jeff’s design was commissioned by SB Acoustics to use the SB29BAC so that version came first. but after a mistake was made resulting in an oversized cabinet for the MW13P-4, another variant was born (SB15CAC-4); as well a desire to use a cheaper tweeter. I traced the impedance curves for both the SB29BAC and SB29SDAC and they are indeed identical. So that is important in a passive crossover (but irrelevant in an active) The frequency response in almost identical, save for the top octave (10-20Khz).
But Jeff didn’t see it as a proposal to warrant changing the crossover. Knowing Jeff doesn’t like to throw extra parts at a crossover unless there’s a good reason to, my guess is that from a dispersion perspective the rising top octave probably results in a more nicer listening window (average over +/- 30 degreees horizontally; +/- 10 degrees vertically)
The summary I gave was the result of my investigations; on WHY the soft dome was a suitable drop-in replacement for this particular speaker, which I theorised, and then built to serve as a reference 7L speaker.
2020 Jeff Bagby Revolution Mini SD
Context is important- Jeff’s design was commissioned by SB Acoustics to use the SB29BAC so that version came first. but after a mistake was made resulting in an oversized cabinet for the MW13P-4, another variant was born (SB15CAC-4); as well a desire to use a cheaper tweeter. I traced the impedance curves for both the SB29BAC and SB29SDAC and they are indeed identical. So that is important in a passive crossover (but irrelevant in an active) The frequency response in almost identical, save for the top octave (10-20Khz).
But Jeff didn’t see it as a proposal to warrant changing the crossover. Knowing Jeff doesn’t like to throw extra parts at a crossover unless there’s a good reason to, my guess is that from a dispersion perspective the rising top octave probably results in a more nicer listening window (average over +/- 30 degreees horizontally; +/- 10 degrees vertically)
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