Hey folks,
There seems to be more discussion on enclosure size, amp power and sub selections going on in the board these days. One topic I wish to address is choosing your setup with a though to dynamic headroom allowances.
We all know that clipping is not a good thing for amps and speakers. The signal wave forms are distorted and not musical at all. The voltage spikes an amp will try to reproduce (but cannot) will deform the audio signal, clip the amp and send high peak voltages (similar to DC) to our speakers. DC or a wave form that closely resembles DC, is very tough on voice coils. They cause the cone to not move as much air through the cooling vents and eventually leads to thermal shorting of the voice coils. Having said that, what to do about this issue?
The Bass Engine is most often, the least understood part of the system. Many do not adjust sub amp gains properly, overdrive the subs with clipped signals or use the wrong enclosure for a given sub. Any of these errors in the equation can lead to premature sub failure, poor SPL/SQ and high distortion levels. Even if you have a premium system, improper setup of the gear can result in sub failure... an expensive repair.
One thing that is commonly practiced in high end HT and Pro sound applications, is to use an amp that can deliver more clean power than the sub is normally rated for. (Ie: 100 watt RMS sub, 150 - 200 RMS amp) When the system is set up properly, the amp will not destroy the sub with that added power. In fact, just the opposite is true! The amp is coasting along at a steady continuous power level and the sub is getting a clean signal.
When signal spikes (Test CD's especially) have several dB more energy than normal music, the amp can take them in stride, pass a larger (but clean signal) to the sub for a short duration of time. (PEAK ratings) The sub will respond well if the enclosure is not too far off of recommended specs for the sub.
Results:
1. No clipping at the amplifier
2. Cleaner and more SPL Peaks can be managed safetly by the subs
3. Damage to subs is eliminated (unless factory defective)
4. Amp lasts longer too
In summary, it is good to use an amp with a higher RMS (Continous) power output ratings on less powerful subs. If the enclosure is properly designed for the sub and the amp gain is correctly set to allow for peak transients, we get a great sounding Bass Engine.
Finally, I am sure a few of you will get this information immediately. For others, it will spawn more questions and issues not addresed to this point. Bring them to the table and let's all learn something new together.
Swez COFFEE
Replies (5)
saintanddolphin on 04/24/2004 07:56:32
Hey Swez.Good article.Should be an FAQ.
I think there may be variables to the extra wattage.Say you have a pair of "economical subs"(I really dont want to call them junk) but a clean, powerful,and efficent amp.Would the same apply or do you need to take in to account the quality of your subs production?
How much is too much?
I think this is one of the least understood concepts in product selection.Considering what I have read on this forum,there are a lot of posters that are suffering from not enough headroom.
Mike COFFEE
asplundher on 04/24/2004 11:45:11
One thing to take into account too, is the decreased power handling that a larger enclosure will bring. Say if the subs rated power is 100rms in a small box yet, decreases to 50rms in a larger enclosure to get deeper bass. If still driven with 100rms, you get the same aspects as Swez pointed out. Design and Power go hand in hand.
Tinker18 on 04/24/2004 11:48:24
the kappas are 350 rms, and the jbl 600.1 is pushign 300 to each. the recommended enclosure size is about 1-1.5 cu feet i think, so if i put them in a 3 cu foot box, thats sealed with its own chambers, would i basically be getting the same effect?brand while we are talking about boxes, i wanna build my own box, in between my bucket seats with one sub the back of the truck and one facing the front, both at angles toward the ceiling, but not much of an angle, only like 30 degrees, would this complicate things, as far as sound or cancellation or anything?br
swez on 04/24/2004 19:50:37
Hard to say if the SQ will be as good as both subs facing the same direction. You will have some phase cancellation as bass waves bounce off solid objects. They will collide eventually in the cabin at certain fequencies. How much effect that will have on over all sound??? I dunno.
Certainly worth a try and you may want to experiement with changing wiring polarity of one sub to see which sound best.
Swez
cplkittle on 04/25/2004 21:50:33
another consideration that I did not see mentioned is that subs need the backpressure from a sealed enclosure to prevent over excursion. If the recommended enclosure size is 1.25 and you up it to around 3.0.. serious caution should be taken to avoid overexcursion.
There seems to be more discussion on enclosure size, amp power and sub selections going on in the board these days. One topic I wish to address is choosing your setup with a though to dynamic headroom allowances.
We all know that clipping is not a good thing for amps and speakers. The signal wave forms are distorted and not musical at all. The voltage spikes an amp will try to reproduce (but cannot) will deform the audio signal, clip the amp and send high peak voltages (similar to DC) to our speakers. DC or a wave form that closely resembles DC, is very tough on voice coils. They cause the cone to not move as much air through the cooling vents and eventually leads to thermal shorting of the voice coils. Having said that, what to do about this issue?
The Bass Engine is most often, the least understood part of the system. Many do not adjust sub amp gains properly, overdrive the subs with clipped signals or use the wrong enclosure for a given sub. Any of these errors in the equation can lead to premature sub failure, poor SPL/SQ and high distortion levels. Even if you have a premium system, improper setup of the gear can result in sub failure... an expensive repair.
One thing that is commonly practiced in high end HT and Pro sound applications, is to use an amp that can deliver more clean power than the sub is normally rated for. (Ie: 100 watt RMS sub, 150 - 200 RMS amp) When the system is set up properly, the amp will not destroy the sub with that added power. In fact, just the opposite is true! The amp is coasting along at a steady continuous power level and the sub is getting a clean signal.
When signal spikes (Test CD's especially) have several dB more energy than normal music, the amp can take them in stride, pass a larger (but clean signal) to the sub for a short duration of time. (PEAK ratings) The sub will respond well if the enclosure is not too far off of recommended specs for the sub.
Results:
1. No clipping at the amplifier
2. Cleaner and more SPL Peaks can be managed safetly by the subs
3. Damage to subs is eliminated (unless factory defective)
4. Amp lasts longer too
In summary, it is good to use an amp with a higher RMS (Continous) power output ratings on less powerful subs. If the enclosure is properly designed for the sub and the amp gain is correctly set to allow for peak transients, we get a great sounding Bass Engine.
Finally, I am sure a few of you will get this information immediately. For others, it will spawn more questions and issues not addresed to this point. Bring them to the table and let's all learn something new together.
Swez COFFEE
Replies (5)
saintanddolphin on 04/24/2004 07:56:32
Hey Swez.Good article.Should be an FAQ.
I think there may be variables to the extra wattage.Say you have a pair of "economical subs"(I really dont want to call them junk) but a clean, powerful,and efficent amp.Would the same apply or do you need to take in to account the quality of your subs production?
How much is too much?
I think this is one of the least understood concepts in product selection.Considering what I have read on this forum,there are a lot of posters that are suffering from not enough headroom.
Mike COFFEE
asplundher on 04/24/2004 11:45:11
One thing to take into account too, is the decreased power handling that a larger enclosure will bring. Say if the subs rated power is 100rms in a small box yet, decreases to 50rms in a larger enclosure to get deeper bass. If still driven with 100rms, you get the same aspects as Swez pointed out. Design and Power go hand in hand.
Tinker18 on 04/24/2004 11:48:24
the kappas are 350 rms, and the jbl 600.1 is pushign 300 to each. the recommended enclosure size is about 1-1.5 cu feet i think, so if i put them in a 3 cu foot box, thats sealed with its own chambers, would i basically be getting the same effect?brand while we are talking about boxes, i wanna build my own box, in between my bucket seats with one sub the back of the truck and one facing the front, both at angles toward the ceiling, but not much of an angle, only like 30 degrees, would this complicate things, as far as sound or cancellation or anything?br
swez on 04/24/2004 19:50:37
Hard to say if the SQ will be as good as both subs facing the same direction. You will have some phase cancellation as bass waves bounce off solid objects. They will collide eventually in the cabin at certain fequencies. How much effect that will have on over all sound??? I dunno.
Certainly worth a try and you may want to experiement with changing wiring polarity of one sub to see which sound best.
Swez
cplkittle on 04/25/2004 21:50:33
another consideration that I did not see mentioned is that subs need the backpressure from a sealed enclosure to prevent over excursion. If the recommended enclosure size is 1.25 and you up it to around 3.0.. serious caution should be taken to avoid overexcursion.
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