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Old 23rd July 2007, 12:24 AM   #11
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Yes, I read through the article again. Thing is, he should be clearer on the project page. A two way active filter sounds like it is for a two way speaker.
At the end of the bi-amping article he does provide a handy calculator for the crosover frequency component values.
A nominal 2500Hz should be good for most 2 ways.
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Old 23rd July 2007, 08:18 AM   #12
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Thanks MJL21193, reassuring to know its wasnt just me who read it like that.

Right I have got some 1k resistors on order now, coupled with the 47nf capacitors already installed (this way I only have to repalce half the components) gives a calcualted Xover frequency of 2394Hz, which if I had come up with in the first place would of made me a little more confident!

I guess then that some of the informaiton between 300Hz and around 2KHz was missing then when I was doing initial listening tests (only way of explaining how the tweeter didnt jump out of the cabinet?) which means I have even more listening pleasure to come!

On a side note, about the hum, I have found if I give the monoblock enclosure a tap, the noise builds up quite considerably and then dies down again a few seconds later, as simple as a dry joint?

And I thought I was almost finished!

Beleive it or not started this project as a little interim whilst I was waiting for the granite in my tube amp to be machined!
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Old 23rd July 2007, 09:02 AM   #13
AndrewT is offline AndrewT  Scotland
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Default Re: Setting up a ESP active crossover with gainclone

Quote:
Originally posted by Dan_Steele
.........I havent yet removed the existing crossovers (but have tested the channel with two separate speakers i.e low output fed into whole crossover on speaker so not to feed 300Hz into 2Khz Xover etc)
you were lucky that you kept the passive crossover in the feed to the tweeter.
Your active rolled off the lower signal at ~300Hz and fed it to a crossover set at ~3kHz. The bass/mid was playing all the signals below 300Hz at correct level.
The frequencies above ~300Hz were sent to the crossover and it filtered out the information below ~3kHz, with the result that the treble driver played the signals above 3kHz at the correct level.

You were only missing the information between 300Hz and 3kHz. This is the band where all intelligible speech is and much of our musical info is in this band as well.

Yes, the project would seem a little flat played like this but, it saved your tweeter.


It might be worth retaining a big cap in the tweeter feed to protect it from faults coming from the amp.
Aim for the cap to roll-off about two octaves below the active filter to preserve much of the phase just below the passband.

You may still find that a simple two way filter sends the wrong information to the two drivers. The passive crossover may also equalise the signals sent to the drivers and you might find that the sound is not quite right, at best, or pretty damn terrible if the drivers are heavily equalised by the passive crossover. Be prepared for further research and much experimentation
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Old 23rd July 2007, 09:03 AM   #14
Nordic is offline Nordic  South Africa
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Glad you got yours working... mine is still motorboating...
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Old 23rd July 2007, 09:07 AM   #15
AndrewT is offline AndrewT  Scotland
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Quote:
Originally posted by Nordic
Glad you got yours working... mine is still motorboating...
motorboating.
What are your high pass filters set to?
Input, NFB & PSU?
Are the decoupling set to reasonable values?
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Old 23rd July 2007, 09:44 AM   #16
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Default Re: Re: Setting up a ESP active crossover with gainclone

Quote:
Originally posted by AndrewT

It might be worth retaining a big cap in the tweeter feed to protect it from faults coming from the amp.

This is good advice. I'll be doing this on my own.
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Old 23rd July 2007, 09:49 AM   #17
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Hi andrew,

Quote:
you were lucky that you kept the passive crossover in the feed to the tweeter.
Well thats what I did first of all, but then removed it alotgether and fed the 300hz into the tweeter with nothing in between (yes it seems stupid now!) - But nothing bad 'seems' to have happnened, the tweet still sounded as crisp as ever - i will put the pass xover back in to verify this ~ I think (and hope!)I may have been lucky!

With regards to implementing tweeter protection with the cap, can you point me in the direction of what this is refered to as so I can do some reading on the topic to better understand how to implement it - calculating values etc. It would cetainly help me sleep easier, even tho I connect the tweet after the amp is powered on, I do flinch slightly just incase something untoward has happened since the last time it was powered up.

Nordic, motoboating always makes me giggle - do a search for its definition of urbandictionary.com !
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Old 23rd July 2007, 10:34 AM   #18
AndrewT is offline AndrewT  Scotland
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Hi,
the series cap is effectively a high pass filter, but it's purpose is to filter out DC from the amp.
Look up single pole passive filter.
The turn-over frequency (=roll-off = F-3db) is set to about 800Hz if the tweeter is doing duty from 3kHz upwards.
25uF is about right for an 8ohm driver. 22uF or 27uF could also be used. It's not a passband filter (that's in the active crossover) so absolute accuracy is not required.
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Old 23rd July 2007, 12:16 PM   #19
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Thanks andrew for your help,

I have a few 22uf solens left over from the tube amp (630V met. polyprop) will insert one of those and listen out for any degrading in the sound.

If its a 4 Ohm driver (will measure tonight) what are the likely if any effects of the 1800Hz roll off as opposed to the suggested 800Hz
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Old 23rd July 2007, 12:27 PM   #20
AndrewT is offline AndrewT  Scotland
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I think 1800Hz is too close to the 3000Hz of the active filter.
The two filters start to add together and the carefully engineered phase and attenuation built into the active crossover have been defeated.

However, there is only one way to KNOW. Try it.

Alternatively, for a 4ohm driver just parallel a second protection capacitor i.e use 50uF.

Have you found the formula yet?
F=1/2/Pi/R/C
F= frequency in Hertz, R=impedance in ohms (at the frequency being considered), C=capacitance in Farads.
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