Hi everyone.
I have a few questions regarding subwoofers, amplifiers and mainly overload protection.
It is going to be a big post here, so I've marked all my questions in bold.
Since I'm new to PA systems and I'm only doing this as a hobby I still have a lot of questions regarding all the PA stuff.
My setup and how I run it:
Speakers:
I usually set up small events (~30-50 people) where heavy bass music is played (Techno, Psytrance, Hardstyle, Frenchcore and Uptempo etc.). That's why I bought the XTi 6002 (Class I amp). I've read in a lot of forums that there is a big increase in the quality of the sound compared to a D-Class (or other classes) amp. My goal is to get a huge "woah" regarding the sound quality from the attendees of my events and I think the decision to get a class I is leading towards that goal.
The problem now is, that the amp is can deliver a lot more power than my subwoofer can handle. So I've activated the limiter on my XTi 6002 at -3dB with almost instant attack (0.1s).
I thought -3dB is half the amount of noise, so it should cut the power in half (3000W). I'm pretty sure it doesn't work that way.
Is there any possible way to calculate at how much watts my amp is limited at what limiter (decibel) configuration?
I found the following calculator from crown (dB Power Ratio):
https://www.crownaudio.com/en-US/tools/calculators
The calculation is dB = 10 * Log (Pout / Pin). I think this is the right calculator to use, is it?
Is there any article that can describe this calculation and how decibels and power output are "connected" with each other?
I really want to know what I'm doing, so I won't break anything.
I recently did my first few events and I had the limiter set at -3dB and put the volume of the amp all the way up (because it will limit anyways, if I hadn't any limiter active I'd never do that). At the events I noticed most DJs tried to get more bass or volume and just turned up the gain, low-end EQ or volume on the DJ controller. At some point my limiter on the bass amp did his thing and stopped increasing the output.
However I didn't have any limiter active on my high frequency amp. So this one just kept going and got louder. This resulted in a lot louder high frequency and the bass felt like it wasn't even there.
I read on some forums that a subwoofer should be able to handle a bit more power than it's peak value (in my case 4800W). Is this the case and how much power over the peak value is too much? Would I even be fine with no limiter at all?
I just don't want to break my subwoofer. And if that means I have to set the limiter a bit more aggressive, I'm fine with that.
I'm also looking forward to getting another subwoofer and change my amp. For this the Crown I-Tech 4x3500HD looks nice (4-channel amp).
It delivers 4000W per channel at 4 ohms and I wouldn't have to upgrade my amp if I want to get even more subwoofers.
However, if I only connect 2 channels onto a 4 channel amp. Will the unconnected channels just do nothing or will the power be "transferred" to the other connected channels (so that I have double the power on the other two channels in this case)?
I'm pretty sure the power won't be transferred but I want to be 100% sure, so I better ask.
Cheers
I have a few questions regarding subwoofers, amplifiers and mainly overload protection.
It is going to be a big post here, so I've marked all my questions in bold.
Since I'm new to PA systems and I'm only doing this as a hobby I still have a lot of questions regarding all the PA stuff.
My setup and how I run it:
Speakers:
- 2x JBL PRX 412M for the high frequency
- 1200 W Peak, 600W Program, 300W Continuous
- 8 ohms
- 1x JBL SRX 828 for the low frequency
- 4800W Peak, 2400W Program, 1200W Continuous
- 4 ohms
- the t.amp E-1500 (for my tops)
- Running in stereo mode
- 950 Watts per channel
- Crown XTi 6002 (for my sub)
- Running in bridged mono mode
- 6000 Watts
I usually set up small events (~30-50 people) where heavy bass music is played (Techno, Psytrance, Hardstyle, Frenchcore and Uptempo etc.). That's why I bought the XTi 6002 (Class I amp). I've read in a lot of forums that there is a big increase in the quality of the sound compared to a D-Class (or other classes) amp. My goal is to get a huge "woah" regarding the sound quality from the attendees of my events and I think the decision to get a class I is leading towards that goal.
The problem now is, that the amp is can deliver a lot more power than my subwoofer can handle. So I've activated the limiter on my XTi 6002 at -3dB with almost instant attack (0.1s).
I thought -3dB is half the amount of noise, so it should cut the power in half (3000W). I'm pretty sure it doesn't work that way.
Is there any possible way to calculate at how much watts my amp is limited at what limiter (decibel) configuration?
I found the following calculator from crown (dB Power Ratio):
https://www.crownaudio.com/en-US/tools/calculators
The calculation is dB = 10 * Log (Pout / Pin). I think this is the right calculator to use, is it?
Is there any article that can describe this calculation and how decibels and power output are "connected" with each other?
I really want to know what I'm doing, so I won't break anything.
I recently did my first few events and I had the limiter set at -3dB and put the volume of the amp all the way up (because it will limit anyways, if I hadn't any limiter active I'd never do that). At the events I noticed most DJs tried to get more bass or volume and just turned up the gain, low-end EQ or volume on the DJ controller. At some point my limiter on the bass amp did his thing and stopped increasing the output.
However I didn't have any limiter active on my high frequency amp. So this one just kept going and got louder. This resulted in a lot louder high frequency and the bass felt like it wasn't even there.
I read on some forums that a subwoofer should be able to handle a bit more power than it's peak value (in my case 4800W). Is this the case and how much power over the peak value is too much? Would I even be fine with no limiter at all?
I just don't want to break my subwoofer. And if that means I have to set the limiter a bit more aggressive, I'm fine with that.
I'm also looking forward to getting another subwoofer and change my amp. For this the Crown I-Tech 4x3500HD looks nice (4-channel amp).
It delivers 4000W per channel at 4 ohms and I wouldn't have to upgrade my amp if I want to get even more subwoofers.
However, if I only connect 2 channels onto a 4 channel amp. Will the unconnected channels just do nothing or will the power be "transferred" to the other connected channels (so that I have double the power on the other two channels in this case)?
I'm pretty sure the power won't be transferred but I want to be 100% sure, so I better ask.
Cheers
Run within linear capability, the topography of the amp makes virtually no difference regarding the sound quality in a DJ application. That said, most DJs do not run amps within their linear capability.
"Almost instant" would be more like .1ms (milliseconds).
An attack of .1s (100ms) should still allow some peak level of a 100 Hz signal (10ms cycle) through before clamping down.
The crown calculator works just the way it should, a 3dB reduction cuts power in half.
If you wanted to limit the 6000 watt peak power (154.9volts into 4ohms) to "2400W Program", the threshold should be dropped to -4dBFS (dB Full Scale), or voltage dropped to 98.
http://www.sengpielaudio.com/Calculations03.htm
Sengpielaudio explains more of the concepts than you have asked about.
Depending on the way the limiter works, that may have stopped SPL increasing, but increased the average level delivered to the drivers.
Yes, that's the way "equal loudness" works ;^)
This all depends on individual driver construction, signal frequency, and peak duration.
No doubt the SRX 728 could withstand 9600 watt peaks of .2ms duration, but 1200 watts of continuous sine wave (3dB crest factor) is probably over the top. You can probably find tracks in the genres of music you play that have the LF signal already compressed to only a 3dB crest factor, in which case -3dB (3000 watts) could still smoke your drivers.
If your HP (low cut) filters are set properly (around 30Hz BW24 for your SRX728) don't worry about the peaks, and go for a longer attack time with a lower average level.
The Crown I-Tech 4x3500HD uses two channels bridged to deliver 4200 watts into 4 ohms.
It uses considerable current limiting, which may allow more peak power to be delivered if half the amp is unused.
It has separate peak and rms limiters, and far more DSP options than the XTi 6002.
That said, you are not going to get a huge "woah" from the audience when the bass drop hits, and the current limiter removes it.
Art
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Yes, The correct solution there is to limit the tops at the point where the subs "run out of gas" or are into limiting.
No power won't be transferred. You could use the other two channels to power the tops of course.
As for putting more power into your existing sub I don't think that is a good idea, you're right at the program rating now which is as much as I'd risk, even that may be too much with certain genres with sustained synth tones.