I'm looking for solutions to the big "thump" that occurs when using an active XO during a power outage. I'm pretty careful to turn off my amps before turning off the XO so that's not a problem, but when a brown out or complete outage occurs, my speakers let out a pop that sounds like a gun shot. It dosn't seem to bother the drivers I have now in the system, but I'm going to add some ribbon tweeters and I just don't know if they'll be able to take it.
So I had a thought...suppose I plug the XO into a UPS that's good for say 15 minutes. That would keep the XO powered at least until the amps discharged. Does that sound like a possible solution?
Anyone else here with experience with the active XO/ribbon tweeter issues?
thanks again,
Allan
So I had a thought...suppose I plug the XO into a UPS that's good for say 15 minutes. That would keep the XO powered at least until the amps discharged. Does that sound like a possible solution?
Anyone else here with experience with the active XO/ribbon tweeter issues?
thanks again,
Allan
hey Zach,
The UPS works like a charm. I bought a beefy one (45 minutes of backup @ 450 watt/800Va) and plugged my preamp and the XO into it.
For a trial run, I connected the preamp and the XO to the UPS, and then the UPS along with the amp to a power strip with an on/off switch so I could cut the power to all three at once. With a great deal of wincing trepidation, I flipped it off and it was quiet as a mouse. That would've normally caused a huge pop from the drivers, but there was nothing but silence as the amp powered down and the XO and preamp kept on running. Very cool!
The UPS works like a charm. I bought a beefy one (45 minutes of backup @ 450 watt/800Va) and plugged my preamp and the XO into it.
For a trial run, I connected the preamp and the XO to the UPS, and then the UPS along with the amp to a power strip with an on/off switch so I could cut the power to all three at once. With a great deal of wincing trepidation, I flipped it off and it was quiet as a mouse. That would've normally caused a huge pop from the drivers, but there was nothing but silence as the amp powered down and the XO and preamp kept on running. Very cool!
It only thumps when it's turned off before turning off the amp; eg. during a power outage or when I'm not thinking. My current XO are Marchand XM1's (2-way) but I've got an Ashly XR2001 (3-way) coming shortly. I talked to Ashly today and they said it would do the same thing and I've heard the same stories about Behringer CX3400's - it's the nature of the beasts evidently. If they're turned off in the correct sequence, there's no problem.
I don't know about other models of active XO's, maybe the Behringer digital XO's don't have the same issues - not sure.
Allan
I don't know about other models of active XO's, maybe the Behringer digital XO's don't have the same issues - not sure.
Allan
AJ said:
Hi AJ,
I prefer to use a large value cap to protect my tweeters (not ribbons) when driving them actively. This then also protects them from power amp turn on/off thumps, power amp dc offset, power amp faults and inadvertent missconnection (i experiment a lot!)
There is a sound quality penalty associted with this approach though.
Konnichiwa,
This suggests the absence of muting circuitry. Very naughty.
Best build/fit your own. All you need is to hunt down on the net a suitable circuit with a 555 that gets re-triggered with every mains cycle (I had to design my own discrete circuit back in Eastern Europe when I build PA Amp's and X-Overs).
If more than a pre-set number of mains cycles (eg set time constant to 60mS for 3 mains cycles cut out or are below trigger (brown out) level the muting (shunt) relais (which "hard" mute the outputs) are immediatly released. You need relais that release quickly, normally closed (NC) contact type.
You may even find that muting circutry is in place but has no triggering for brown/black out and you could add this on. I know the older Behringer Digital EQ muted quickly before it started to kake farting noises etc, so the same MAY apply to Behringer Digi X-Over, in which case there would be a lot of relais on the Output PCB.
Sayonara
AJ said:
This suggests the absence of muting circuitry. Very naughty.
Best build/fit your own. All you need is to hunt down on the net a suitable circuit with a 555 that gets re-triggered with every mains cycle (I had to design my own discrete circuit back in Eastern Europe when I build PA Amp's and X-Overs).
If more than a pre-set number of mains cycles (eg set time constant to 60mS for 3 mains cycles cut out or are below trigger (brown out) level the muting (shunt) relais (which "hard" mute the outputs) are immediatly released. You need relais that release quickly, normally closed (NC) contact type.
You may even find that muting circutry is in place but has no triggering for brown/black out and you could add this on. I know the older Behringer Digital EQ muted quickly before it started to kake farting noises etc, so the same MAY apply to Behringer Digi X-Over, in which case there would be a lot of relais on the Output PCB.
Sayonara
I don't recommend the 555. Here's an appropriate circuit from the renowned Rod Elliot:Kuei Yang Wang said:
http://sound.westhost.com/project104.htm
I've been using Marchand Active crossovers for years, they do have a little thump, but nothing like what you describe. I find the best way to deal with this is to never turn off the crossover, mine's been on continuously for about 3 years, no reason to ever turn it off, in fact my amps are always on as well.
Konnichiwa,
The function of this is indentical to the 555 Based circuit with more parts and a less accurately defined trigger voltage and timing. But yes, it will work fine. As remarked, you can do the same thing in many ways, including fully discrete.
The essence is the following operation:
1) The circuit has a turn on Delay (a few seconds).
2) The circuit once turned on will switch off within in a very short time span (<< 100mS), unless re-triggered by an external pulse signal (eg. AC from the secondary of the mains transformer via a diode).
3) The trigger level is clearly defined such that if the the supply (AC) voltage drops below a certain level (brown out) the relais is released instantly.
The 555 can be set up as having very few added components in this operation and as doing it reliable and without significant supply voltage and thermal drifts of parameters. In that it is superior to either Rod Elliotts design or my old discrete one, though all will work just fine in practice.
Sayonara
paulb said:
The function of this is indentical to the 555 Based circuit with more parts and a less accurately defined trigger voltage and timing. But yes, it will work fine. As remarked, you can do the same thing in many ways, including fully discrete.
The essence is the following operation:
1) The circuit has a turn on Delay (a few seconds).
2) The circuit once turned on will switch off within in a very short time span (<< 100mS), unless re-triggered by an external pulse signal (eg. AC from the secondary of the mains transformer via a diode).
3) The trigger level is clearly defined such that if the the supply (AC) voltage drops below a certain level (brown out) the relais is released instantly.
The 555 can be set up as having very few added components in this operation and as doing it reliable and without significant supply voltage and thermal drifts of parameters. In that it is superior to either Rod Elliotts design or my old discrete one, though all will work just fine in practice.
Sayonara
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