I don't see such a lot of confusion 
The Linkwit Transform, as has been said, is a "biquadratic" circuit, so it has a pair of poles and a pair of zeros. You can use it to "cancel" the poles of speaker and closed-box set using the LT zeros and change them for another pair (the LT poles) which produce a different Q and fs or fb. And that's all, no-so-simple Laplace equations but it's easy to see from the math pov.
As always... there are several constraints that must be filled in order to get the job done, but as you can put the poles wherever you want, you can change the transfer function of the speaker and shape its low frequency roll-of. And it doesn't matter if it is a woofer or a mid or a tweeter... all of them have a second order TF...
The Linkwit Transform, as has been said, is a "biquadratic" circuit, so it has a pair of poles and a pair of zeros. You can use it to "cancel" the poles of speaker and closed-box set using the LT zeros and change them for another pair (the LT poles) which produce a different Q and fs or fb. And that's all, no-so-simple Laplace equations but it's easy to see from the math pov.
As always... there are several constraints that must be filled in order to get the job done, but as you can put the poles wherever you want, you can change the transfer function of the speaker and shape its low frequency roll-of. And it doesn't matter if it is a woofer or a mid or a tweeter... all of them have a second order TF...
Hi,
I'm not confused about what a typical LT is, and a its not a bass boost
circuit for drivers placed in silly sized sealed boxes for no good reason.
Generally A LT inverses a drivers bass roll off response in a small
box and then replaces that roll off with the wanted bass rolloff.
SL typically juggles the box size, power available, driver capabilities
and the new roll off to get relatively compact subwoofers, and
the salient feature is the cancelled roll-off is underdamped.
If its overdamped there is no point or need to cancel it.
SL does not advocate low Q boxes, quite the opposite.
Most of his boxes are high Q underdamped, uncorrected.
You don't need zeros to EQ an overdamped box,
you do underdamped. No zeros it is not a classic LT.
Whilst you can still use poles and zeros on an overdamped
box, there is no good reason do so, you don't have to.
rgds, sreten.
I'm not confused about what a typical LT is, and a its not a bass boost
circuit for drivers placed in silly sized sealed boxes for no good reason.
Generally A LT inverses a drivers bass roll off response in a small
box and then replaces that roll off with the wanted bass rolloff.
SL typically juggles the box size, power available, driver capabilities
and the new roll off to get relatively compact subwoofers, and
the salient feature is the cancelled roll-off is underdamped.
If its overdamped there is no point or need to cancel it.
SL does not advocate low Q boxes, quite the opposite.
Most of his boxes are high Q underdamped, uncorrected.
You don't need zeros to EQ an overdamped box,
you do underdamped. No zeros it is not a classic LT.
Whilst you can still use poles and zeros on an overdamped
box, there is no good reason do so, you don't have to.
rgds, sreten.
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Why not???
If you have an overdamped box (or speaker, as in my tweeter's example) with a Q=0.3 and you want to take it up to 0.5, you DO NEED to cancel the current poles by using the LT's zeros and place a new pair in another position to accomplish the new spec.
Probably, you won't need to compensate for any hump in an overdamped system, but that is a different tale...
I'm personally not the least bit interested in DSP, I'm an Analog Kid.
Mike
Even if you stick to the analog domain for realization, there are several types of circuits that can be used to implement a biquadratic filter a la the Linkwitz Transform. Only the one that SL promulgated has no realization for some pairs of Fc and Q. There is only one other single op amp biquadratic filter realization that I am aware of, however, and most require 4 or more amplifiers.
Wow. most of this is way over my head, or at least its going to take me a while to process it all. But hey I'm glad to have sparked an intelligible conversation at least. I suppose it helps if you have a clear mental picture of what all these acronyms/abbreviations mean without having to flip back and forth to look up their explanations.
So basically I was just postulating that I might be able to also use the LT with mids/highs to create something like PC monitors with a very small enclosure or possibly something like a tablet/phone dock with a minimal profile. I didn't have any particular driver in mind at this point.
I didn't realize it was already common practice to apply the LT in other ways... I was focusing on the enclosure size attribute of an LTed sub-woofer, and not stepping back to realize that its just a filter function which I'm sure has many applications.
So basically I was just postulating that I might be able to also use the LT with mids/highs to create something like PC monitors with a very small enclosure or possibly something like a tablet/phone dock with a minimal profile. I didn't have any particular driver in mind at this point.
I didn't realize it was already common practice to apply the LT in other ways... I was focusing on the enclosure size attribute of an LTed sub-woofer, and not stepping back to realize that its just a filter function which I'm sure has many applications.
I'm with charlie here.
Nonlinear distortion testing of loudspeaker driver units
There really isn't any restriction-any driver in a closed box can have it's q and Fc moved, assuming you pay attention other design factors, excursion, power etc.
Nonlinear distortion testing of loudspeaker driver units
There really isn't any restriction-any driver in a closed box can have it's q and Fc moved, assuming you pay attention other design factors, excursion, power etc.
Hi,
Siily sized boxes means stupidly big boxes for the driver
leading to it being overdamped and only need boost EQ.
Linkwitz never did that and its not a LT.
rgds, sreten.
Sreten,
I'm not sure what you mean by
Mike
I'm not sure what you mean by
, but here's what I'm refering to: SB1980-3way, Look at "Woofer equalization" in part 2.
Mike
Look at the THOR, the most recent sub SL did. Oversized by about 100%. I have also used these wonderful Peerless drivers (now OBE in the paper/carbon form) and found them unhappy in a high Q box but very happy in a low Q box. This is the same driver referenced in the "critical sub" design.
Because SL did one thing a long time ago does not mean he still advocates it. He might have been years ahead of most of us, but that does not mean he too does not learn. After all, his first published sets used the now recognized as horrible KEF drivers. He has changed preferences from boxes to OB and has changed preferences in drivers every time.
Because SL did one thing a long time ago does not mean he still advocates it. He might have been years ahead of most of us, but that does not mean he too does not learn. After all, his first published sets used the now recognized as horrible KEF drivers. He has changed preferences from boxes to OB and has changed preferences in drivers every time.
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