Deliberately incorrectly doing tweeter impedance compensation - Page 2 - diyAudio
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Old 18th May 2012, 07:18 PM   #11
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[LEFT]excuse me for my ignorance but isnt this the same thing as making a 2nd order filter and altering the parallel circuit resistance, to alter the filter q?[ maybe ive missed somethng?/LEFT]
its sounds like adding L to a 2nd order LP in the shunt circuit, and using the dcr of the L to adjust notching. Almost a 1st order with notch centred at the 2nd pole. If so, thats exactly what i did with the xo on my visatons, 1 small mod from the vib130tl schematic to notch out the brebkup even more
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Old 18th May 2012, 11:32 PM   #12
sreten is offline sreten  United Kingdom
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Quote:
Originally Posted by speaker dave View Post
Do you have a phase curve to go with your figure 12?
Hi,

No I don't. But it will be as bad as you imagine. In Zaphs design the drivers
phase curve is also bad, but it the opposite way, and the two together
give the approximate phase response of a 4th order L/R acoustic function.

rgds, sreten.
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Old 19th May 2012, 12:20 AM   #13
tvrgeek is offline tvrgeek  United States
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I have been playing with the same tweeter, but not with the same luck as John has in this design. My samples roll off so low, I need the full transfer function from the crossover. I have also been totally stymied in managing the 26K breakup. It could be that I am still working with only the tweeter and have not dealt with the 120 degree phase difference my model implies. (using the Zaph midrange)
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Old 19th May 2012, 07:00 AM   #14
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ok. I gather it is just the same as i imagined, using series R TO CHANGE the R value, in the R+ jX.... sounds alot like what many designers have been doing for years...wheres the discovery?
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Old 19th May 2012, 12:14 PM   #15
DavidL is offline DavidL  United States
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Mondogenerator, not everyone knows all there is to know about speaker/crossover design and this is DIY and sharing so cut us some slack. It sure beats just having subjective "I know what I heard" discussions on here.Please share with us your knowledge too and we can further our discussion and maybe all learn something.
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Old 19th May 2012, 12:44 PM   #16
sreten is offline sreten  United Kingdom
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Quote:
Originally Posted by mondogenerator View Post
ok. I gather it is just the same as i imagined, using series R TO CHANGE
the R value, in the R+ jX.... sounds a lot like what many designers have
been doing for years...wheres the discovery?
Hi,

There is nothing new about using the arrangement for a low pass filter
to curb break up modes above the x/o point. But that is not the subject
of the thread, the subject is a similar arrangement in a high pass filter,
and only applies to impedance peak compensated high pass networks.

Only some designers use it for low pass, some still use high order filters,
and I've never seen a documented design that uses it for high pass.

As DBM says, its also applicable to mids if you are compensating their
impedance peaks as well as tweeters. Its not a "discovery", it is
something I've not seen described in any book / article.

Doesn't mean it isn't, but it is obscure and not well known.

rgds, sreten.
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Old 19th May 2012, 08:01 PM   #17
AllenB is offline AllenB  Australia
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Quote:
Originally Posted by speaker dave View Post
A notch typically puts a quick transition into the phase curve.
Funny, but I just posted an example of using a notch filter to control phase in another thread, showing with and without.
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Old 19th May 2012, 09:29 PM   #18
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apologies. It wasnt my intention to appear critical, i was trying to get my head round what the circuit looked like in my head. Im by no means an expert, but i have simmed such thing on occasion using boxsim, but im not sure ive really considered it thoroughly. It seems a little like all pass stages added to a bring phase back, in that the advantage comes with higher complexity, and all that entails.interesting subject though, and i hadnt seriously thought of this approach
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Old 19th May 2012, 11:23 PM   #19
AllenB is offline AllenB  Australia
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Quote:
Originally Posted by sreten View Post
Instead of simply compensating the tweeters impedance peak use this as a further way of manipulating the actual high pass function of the tweeter.
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Old 19th May 2012, 11:44 PM   #20
PLB is offline PLB  United Kingdom
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Hi Sreten,

Thanks for starting this thread. It is indeed an interesting approach to overcoming the tweeters impedance peak problem at its resonance. It occurred to me that with such a topology, you may also be able to implement the so called “Neville Thiele Method” Xover as described in this link, NTM Crossovers
where a notch is deliberately inserted into the HP filter response, to compliment that in the LP response.
With your observations in mind, it seems that the same circuit topology might be used to implement either a LR or NTM type Xover simply by changing the notch depths.

Regards

Peter
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