• Welcome to ASR. There are many reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!

By-passing speaker's passive crossover for DSP crossover - need to insert capacitor/s?

Hayabusa said:
You can set the starting frequency if you do sweep with REW.
Click to expand...

I know, in this case it is not so much the frequency but the power rating of the voicecoil. You can put 20Hz on a tweeter as long as the power remains (well) below the continuous rating of the tweeter. When you have the mic up really close you don't need much power yet have enough acoustic level to get meaningful results from a mic.
 
Music1969 said:
And at low power level, it’s ok to do 20Hz to 20kHz with both tweeter and woofer?
Click to expand...

Yes, but pointless to sweep a tweeter from 20Hz as it won't do much. The woofer you can sweep wideband.
 
Music1969 said:
Ok thanks. So if passive crossover is 1.5kHz then starting frequence sweep for tweeter at 1.3 kHz sound like a good idea?

And for woofer finishing sweep 1.7kHz should be ok to start?
Click to expand...

When your XO (12dB/oct) is -3dB at 1500Hz you can start the sweep at 500Hz or 300Hz if you want to know its response. Just measure the tweeter really up close at a low output level.
 
solderdude said:
When your XO (12dB/oct) is -3dB at 1500Hz you can start the sweep at 500Hz or 300Hz if you want to know its response. Just measure the tweeter really up close at a low output level.
Click to expand...

Thanks again!
 
solderdude said:
When your XO (12dB/oct) is -3dB at 1500Hz you can start the sweep at 500Hz or 300Hz if you want to know its response. Just measure the tweeter really up close at a low output level.
Click to expand...

And what SPL is considered low level?

50 dB at very close range is OK?
 
At very close range (say 2 cm) 80dB SPL is fine, at 1m it would be about 45dB SPL.
Very safe to sweep the tweeter from as low as 10Hz at this level (80dB SPL at 2cm !!!) and is enough to get a good S/N ratio for the mic and surrounding sounds in the room.

Your speaker can produce 80dB @ 5m distance at 1W, this is about 94dB @1m (assuming anechoic conditions) so 80dB SPL @ 2cm will require about 0.4mW = 0.004W That won't destroy the lowest power tweeter on the planet.

It is the same reason why you can hear amplifier background noise with your ear against the tweeter but not at 1m or listening position
 
Last edited:
solderdude said:
At very close range (say 2 cm) 80dB SPL is fine, at 1m it would be about 45dB SPL.
Very safe to sweep the tweeter from as low as 10Hz at this level (80dB SPL at 2cm !!!) and is enough to get a good S/N ratio for the mic and surrounding sounds in the room.

Your speaker can produce 80dB @ 5m distance at 1W, this is about 94dB @1m (assuming anechoic conditions) so 80dB SPL @ 2cm will require about 0.4mW = 0.004W That won't destroy the lowest power tweeter on the planet.

It is the same reason why you can hear amplifier background noise with your ear against the tweeter but not at 1m or listening position
Click to expand...

If I find the actual/ideal crossover by measurement, then capacitor in-line with the tweeter wouldn't be required, is that correct?
 
When you have the amplifier and filter 'fixed' onto the rear of the speaker it won't be needed.
When there is the slightest chance you could make a mistake with wiring or filter settings I would use a series capacitor calculated to about 500Hz crossover with the tweeter. It will protect the tweeter from disasters in such case.
 
solderdude said:
When you have the amplifier and filter 'fixed' onto the rear of the speaker it won't be needed.
When there is the slightest chance you could make a mistake with wiring or filter settings I would use a series capacitor calculated to about 500Hz crossover with the tweeter. It will protect the tweeter from disasters in such case.
Click to expand...

This below should be ok? Based on the calc for 500Hz and 5ohms for an amp outputting 100W into 8 ohms


1592657515253.png


@Hayabusa
 
Peak-to-peak voltage Vpp ~ 3 x Vrms (2 * sqrt(2) * Vrms = 2.828 * Vrms)

Either buy a nonpolar capacitor or wire two polarized electrolytic capacitors in series back-to-back (e.g. amp -> +C1 -> -C1 -> -C2 -> +C2 -> tweeter). That haves the value of the capacitors so for example two series 100 uF capacitors become one 50 uF capacitor.
 
Last edited:
Music1969 said:
Hi Don, do you mention this because I miscalculated something?
Click to expand...

No, I tend to use Vpp and not Vpk just to build in a safety factor. 100 W average (technically not Wrms) is about 28.28 Vrms = 40 Vpk = 80 Vpp.

I added a line about placing caps in series to create a nonpolar version.
 
DonH56 said:
No, I tend to use Vpp and not Vpk just to build in a safety factor. 100 W average (technically not Wrms) is about 28.28 Vrms = 40 Vpk = 80 Vpp.

I added a line about placing caps in series to create a nonpolar version.
Click to expand...

Thanks!

I feel lucky to have some of the ASR big puns offering all this advice.

Much appreciated to all.
 
Music1969 said:
Thanks!

I feel lucky to have some of the ASR big puns offering all this advice.

Much appreciated to all.
Click to expand...

Punnily appropriate... :)
 
Another silly question: the passive crossover had an old circuit board with the various components.

Now removing the passive crossover I will just have wire between drivers and binding posts.

If I'm inserting this protective capacitor in-line with tweeter, is it ok to just have it in between wire, just hanging this inside the speaker?

No risk of catching fire with the wool or wooden speaker cabinet?

Or is there a better way than just letting the capacitor hang there in between 2 wires inside the cabinet?

What is good practise for inserting this capacitor.

Thanks again
 
You must log in or register to reply here.

Similar threads

H
From Passive Crossover to Pro DSP/LSM – What’s the Best Route?
Replies
5
Views
204
haloo2
H
U
combine active and passive crossover in the same speaker
Replies
15
Views
2K
dualazmak
dualazmak
B
Need help with compact line array design crossover and box LMS or leap
Replies
0
Views
183
BC event
B
T
Are these any good?
Replies
4
Views
642
Mart68
M
M
Choosing crossover point from response curve
Replies
8
Views
587
staticV3
staticV3
Back
Top Bottom