Help me convert old speakers to actives

[AlmaAtaKZ]

First step - just ordered this

Then will have to buy a cheapo Win notebook and a Umik2.

Then can start the first conversion, passive to actives using existing drivers and Hypex Fusion FA123 amps.

Thinking later to replace existing drivers with a coax HF/MF and a pair of high-excursion LF.

 

[AlmaAtaKZ]

 

[Cbdb2]

If only I knew these!

do you have an AC volt meter that works up to 10khz? thats all youll need

 

[AlmaAtaKZ]

do you have an AC volt meter that works up to 10khz? thats all youll need

No, I do not have one.

 

[Cbdb2]

have soldering iron already. Multimeters look cheap on Amazon, so will get one once ready to start.

get one with a 20khz bandwidth

 

[AlmaAtaKZ]

I am starting with:
- reading the book
- installing and configuring REW (Mac)
- ordered a Dayton UMM 6 mic
- will measure the existing speakers in their current passive config (all and individual drivers)

 

[AlmaAtaKZ]

get one with a 20khz bandwidth

I made myself a promise not to buy anything unless I understand the need. I do not yet understand the need for it. Could do with an explanation. Is it to figure out the passive crossover point? Why is it necessary? Or nice to have?
I thought I would measure the individual drivers and from their response will figure the future active crossover point. Why do I need to find the passive crossover point?

 

[Salt]

You can see the xover frequency by measuring the woofer's frequency response while covering the tweeter (et vice versa, but complete damping the woofer's output is more difficult).

 

[AlmaAtaKZ]

You can see the xover frequency by measuring the woofer's frequency response while covering the tweeter (et vice versa, but complete damping the woofer's output is more difficult).

I thought I would just disconnect the drivers at the crossover output. I am thinking it will change the crossover performance, but will the measurement be still largely valid?

 

[Cbdb2]

If you want to use the existing xover as a guide, what I would recomend: When I converted a 2 way to active all I used was a multimeter and tones from my PC. More accurate than a mic in a room. I measured the voltage at each driver with tones, a couple of measurements per octave for the range the driver covers. Measure the input to the speaker each time ( I used 1 volt AC) to make sure this dosnt change than measure and record the voltage at the driver. This will not only show you the xover points and slopes but also any other driver anomolies that the xover might be fixing. Than you recreate this xover with an active one add the amps and measure it the same way to try to get the same voltages. Than if you want measure it with a mic and adjust for flatness or taste.
With my desktops the xovers included slopes before and after the xover freq. to adjust for the drivers changing efficiencies with freq. The drivers werent flat.
The other suggestion I have is to do 1 speaker completely first and then you can compare your results by listening to a before and after.

heres my measurements, plotted on a log log scale. You can also see the woofer is 6db hotter than the tweeter.

 

[AlmaAtaKZ]

understand. And a good tip to convert one speaker and compare.
I did not plan to copy the existing crossover and did not feel the need (rightly or wrongly) to know the old crossover as a guide. My thinking was measure the drivers and then apply ‘the best’ crossover in dsp.

 

[Cbdb2]

I made myself a promise not to buy anything unless I understand the need. I do not yet understand the need for it. Could do with an explanation. Is it to figure out the passive crossover point? Why is it necessary? Or nice to have?
I thought I would measure the individual drivers and from their response will figure the future active crossover point. Why do I need to find the passive crossover poin

If you want to do any electronics or measure any electronics get a decent multimeter, it will last your lifetime. If you measure the drivers with a mic your measureing the F response of the xover/driver combination (plus room effects). The bookshelfs I converted did measure flat acoustically but look at my xover measurements, no where near flat because the drivers arnt flat either. so if you want to recreate the passive xover, the best place to start, you need to measure the signal at he xover output. I dont know REW well enough to know how accurate its meters are, you want something thats within 1 db or so. A multimeter is .01db accurate?

 

[Sokel]

If you want to do any electronics or measure any electronics get a decent multimeter, it will last your lifetime. If you measure the drivers with a mic your measureing the F response of the xover/driver combination (plus room effects). The bookshelfs I converted did measure flat acoustically but look at my xover measurements, no where near flat because the drivers arnt flat either. so if you want to recreate the passive xover, the best place to start, you need to measure the signal at he xover output. I dont know REW well enough to know how accurate its meters are, you want something thats within 1 db or so. A multimeter is .01db accurate?

To his defense,to get a nice 20kHz BW true RMS DMM with tight tolerances is not cheap.
A simple one can do too for the basics but yes,is mandatory.

 

[Cbdb2]

understand. And a good tip to convert one speaker and compare.
I did not plan to copy the existing crossover and did not feel the need (rightly or wrongly) to know the old crossover as a guide. My thinking was measure the drivers and then apply ‘the best’ crossover in dsp.

So you will measure the drivers without the xover? You would have to or you get the above problem. That will work but your room might effect your measurements. But why reinvent the wheel. The manufacturer has already done the research (hopefully, Monitor makes good soeakers so probably) as to best xover point and slope. For example, do you know the breakup freq. of the woofers and how to avoid it with the xover?
Your method sounds like a lot of trial and error.

 

[Cbdb2]

To his defense,to get a nice 20kHz BW true RMS DMM with tight tolerances is not cheap.
A simple one can do too for the basics but yes,is mandatory.

True but a cheap one that isnt true RMS and measures something at 20khz can still be used to compare sinewave voltages, as in the out is 3db lower than the input.
You might be suprised at how good some of the cheap ones have gotten.

 

[AlmaAtaKZ]

I will try to measure FR and distortion per driver, then hope to crossover to completely avoid the bad areas

 

[Sokel]

True but a cheap one that isnt true RMS and measures something at 20khz can still be used to compare sinewave voltages, as in the out is 3db lower than the input.
You might be suprised at how good some of the cheap ones have gotten.

I have some and true,can't live without my cheap-ish Extech EX520 even if it's trueRMS only up to 1kHz.
A nice DMM can literally save lives.

 

[Salt]

understand. And a good tip to convert one speaker and compare.
I did not plan to copy the existing crossover and did not feel the need (rightly or wrongly) to know the old crossover as a guide. My thinking was measure the drivers and then apply ‘the best’ crossover in dsp.

This
is exactly the direction I would go.
But some bit of knowledge is required

 

[AlmaAtaKZ]

Tool (toy) one is here. This should be able to serve all my measurement needs - enough power and transparent. Gain adjustment should come handy, too.

 

[AlmaAtaKZ]

The mic