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post #1 of 16 Old 06-26-2016, 11:51 AM - Thread Starter
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Question on Amplifiers

With much assistance from the excellent threads here, I'm about to finish my first subwoofer build. I'll be using the iNuke 6000DSP to power one 18" DS4-18; I might add a second sub at some point, but just one for now.

So here's my question: If I only have one sub, do I HAVE to run the amp in bridge mode? Or can I run the sub off of one single channel if the other channel is unloaded?

Many thanks!
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post #2 of 16 Old 06-26-2016, 12:24 PM
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iNuke 6k can't be bridged. It's basically two bridged 3ks in a single chassis.
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post #3 of 16 Old 06-26-2016, 01:53 PM
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+1

It does not "hurt" an amp in any way to not use one of the channels. Actually, with most amplifiers the the two or more channels share a power supply so you get better performance from one channel than both channels at the same time.

My brother has been using a 5.1 channel AVR in a stereo 2.1 channel mode for 15 years with no problems. He connected some speakers he had laying around for 5.1 and it worked fine.

Enjoy your new sub!
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post #4 of 16 Old 06-26-2016, 02:21 PM - Thread Starter
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Ah! Thanks to you both!

I had thought I had read somewhere that you shouldn't run a pro amp with a channel unloaded, but that seemed pretty daft
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post #5 of 16 Old 06-26-2016, 03:18 PM
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6000dsp is a decent match for that sub, so you are on decent track.


the 6000 isn't an "amps monster" so you may need to limit the output just a hair in order to prevent the amp from power cycling during the most extreme bass output, particularly if running smallish sealed and boosting the lowend, when you add the second sub.

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post #6 of 16 Old 06-26-2016, 10:39 PM
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Quote:
Originally Posted by *tl View Post
I had thought I had read somewhere that you shouldn't run a pro amp with a channel unloaded, but that seemed pretty daft
Nah, it's rubbish. Because of the modularity of my PA, it was often run with one channel of an amp unused and those amps were used harder than anyone ever will in an HT. Some I still have and in use.
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post #7 of 16 Old 07-08-2016, 08:08 AM
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The iNUKE 6000dsp can drive more power per channel when using just one channel than using both combined per channel. It's limited to around 1100-1200 per channel both channels driven, but can hit upwards of 2000 watts with just one channel used.

So you are good.
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post #8 of 16 Old 07-08-2016, 08:55 AM
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only one channel was measured at a time for these tests. summary is your max output potential on a given channel drops by about 1db if you run two channels instead of just one.

1 of 2 channels into 4 ohms


2 of 2 channels into 4 ohms
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post #9 of 16 Old 07-08-2016, 09:25 AM
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Quote:
Originally Posted by notnyt View Post
only one channel was measured at a time for these tests. summary is your max output potential on a given channel drops by about 1db if you run two channels instead of just one.

1 of 2 channels into 4 ohms


2 of 2 channels into 4 ohms
Hmm, I based my comments on this thread: http://forum.speakerplans.com/behrin...opic69202.html

"The Behringer was happy to drive 1 channel at 4 Ohms with no reduction in output at 1 minute. Power output was 2.27kW at 1kHz and 2.12kW at 31Hz."
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post #10 of 16 Old 07-08-2016, 12:03 PM
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Quote:
Originally Posted by murphy2112 View Post
Hmm, I based my comments on this thread: http://forum.speakerplans.com/behrin...opic69202.html

"The Behringer was happy to drive 1 channel at 4 Ohms with no reduction in output at 1 minute. Power output was 2.27kW at 1kHz and 2.12kW at 31Hz."
for practical purposes, this is starting to split hairs.


at least as important is to remember that subwoofers are not resistors.


here is 88.3 volts (2000 "watts") into a ds4-18 in 6 cubic feet sealed. I added a 1st order highpass which the inuke has built in around 7hz or so and a 4th order low pass at 80hz as would commonly be used in matching to mains.


what this graph shows is that the worst case scenario for the amp is around 14hz where it is required to produce about 1225 watts of power. so in this application the user will get 88.3 volts (2000 "watts") of output but the amp will only have to survive 1225 real watts and that is with a sustained output 14hz signal.





for the worst case scenario (14hz tone) 'not's testing indicates that it will survive this level with one channel driven no problem and will be right on the borderline with two channels driven.
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post #11 of 16 Old 07-08-2016, 12:18 PM
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@Archaea is running one um18 per channel on inuke 6000 dsp amps in 4 cubic foot enclosures (roughly).


https://www.avsforum.com/forum/155-di...l#post37805121


he set the limiter for 1750 "watts" into 4 ohms, which is 83.66 volts rms. this was arrived at empirically by trying to find the max output for the limiter that would prevent shutdown under maximum drive with both channels driven.


the red line is roughly how amp power models in his rig with the same 1st order hp at 7hz and 4th order lp at 80hz. both channels driven is fine at this level. going much higher causes the amp to power cycle during maximum demo output sessions.


so model it up and keep the power under notnyt's measured results during the worst case scenario and the amp should be ok (at least for the duration of notnyt's testing). :-)


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post #12 of 16 Old 07-08-2016, 12:21 PM
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Quote:
Originally Posted by LTD02 View Post
so model it up and keep the power under notnyt's measured results during the worst case scenario and the amp should be ok (at least for the duration of notnyt's testing). :-)

Or set the voltage limiters right under what I tested at and blast away These have great limiters when configured properly.
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post #13 of 16 Old 07-08-2016, 01:13 PM
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Quote:
Originally Posted by LTD02 View Post
for practical purposes, this is starting to split hairs.


at least as important is to remember that subwoofers are not resistors.


here is 88.3 volts (2000 "watts") into a ds4-18 in 6 cubic feet sealed. I added a 1st order highpass which the inuke has built in around 7hz or so and a 4th order low pass at 80hz as would commonly be used in matching to mains.


what this graph shows is that the worst case scenario for the amp is around 14hz where it is required to produce about 1225 watts of power. so in this application the user will get 88.3 volts (2000 "watts") of output but the amp will only have to survive 1225 real watts and that is with a sustained output 14hz signal.





for the worst case scenario (14hz tone) 'not's testing indicates that it will survive this level with one channel driven no problem and will be right on the borderline with two channels driven.
Please understand that this is a bit over my head, so I may not understand it correctly. Is your graph based on the actual driver and cabinet, which combined, give resistance relative to frequency? If that's the case, then I would assume that it's not dipping below 4ohms very often or at all, correct?
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post #14 of 16 Old 07-08-2016, 02:45 PM
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Quote:
Originally Posted by murphy2112 View Post
Please understand that this is a bit over my head, so I may not understand it correctly. Is your graph based on the actual driver and cabinet, which combined, give resistance relative to frequency? If that's the case, then I would assume that it's not dipping below 4ohms very often or at all, correct?

that is exactly right. thumbs up.


when resistance changes with frequency we refer to it as "impedance", but the equations otherwise work the same.

if the speaker were a pure resistor, then the impedance would be flat at 4 ohms (or whatever the driver dc resistance is) and the power would also be a flat line that could be calculated using ohm's law.


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post #15 of 16 Old 07-11-2016, 07:57 AM
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^^ what program did you use to model this? Winisd? I want to model my own, but tried winiSD and didn't make it very far.
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post #16 of 16 Old 07-11-2016, 08:23 AM
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^^ what program did you use to model this? Winisd? I want to model my own, but tried winiSD and didn't make it very far.
that's winisd
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