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Over Powering or Underpowering the subs, which is better?

  #1  
Old 10-21-2010, 12:48 PM
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Default Over Powering or Underpowering the subs, which is better?

I have been going through the pages of the forums and internet for a long time and still cant get a definite answer on this issue. But every other site gives different answers. I am a student and cant afford too much $$$ in the system. So I have been buying stuff when I can and finally I have a complete setup. I will be upgrading when I have enough saved later but for now this is my setup.

I have a sony xplod 10" sub, model: xs-L1037, rated 200 watts rms and 800 watts peak. I know this is not a good subwoofer at all, but I got it for a cheap price with the box. Read above, I am a student and cant afford new stuff.

I recently purchased a used dual amp, model: xia-2460, rated at 100 watts rms x 2 @ 4ohms and 300watts rms x1 @ 4 ohms(bridged).

I have a 8 AWG lines for power and ground.

Everything is connected properly.

Now my question is should I run the sub with only one channel running at 100 watts rms(under powering the sub by 50% since the sub is rated at 200 watts rms) or should I run it bridged at 300 watts rms(over powering the sub by 100 watts than suggested).

I listen to the hard and classic rock most of the times, thats why I went with 10" rather than 12" subs. Only time I listen to hip hop is when my friends are in the car. But never the less I love the songs with the double bass drums and bass riffs.

I am a hobbyist musician so, I know what the difference between fast tight bass and loud muddy bass. And I am also a computer engineer so, I am pretty good at wiring and cabling stuff. But I am new to the car audio setups.

Back to the question, should I underpower and increase the gain or overpower and decrease the gain on the amp.

I am running it off a sony xplod cdx-gt 420u head unit. And I drive 97 accord lx v6.

Any help is much appreciated, thanks.
 
  #2  
Old 10-21-2010, 11:34 PM
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welcome to HAF. you have a common question with one definite answer. The problem with internet forums is that most people have no idea what they are talking about. I'm an Acoustics Engineer with an Electrical Engineering degree and over 15 years experience in mobile electronics.

first, the terms "underpower" and "overpower" are misleading.

The answer to your question comes in the term "musical dynamics". you want enough power to reproduce dynamics, and when you start reaching the power ratings of the sub, you don't want clipping.

By using only one channel of the amp, you will be very likely to get clipping while trying to drive the sub at 100W. By bridging the amp you will be more likely to attain the desired power level you want to achieve (200W) without pushing the amp to it's limits.

it's a misconception that smaller subs are "faster" than larger subs. 60Hz is 60Hz. For the impact of a kick drum that we all love you need two things - musical dynamic power and minimum phase response.

I have a very impactfull kick drum with my pair of 12's, and they are very SQ oriented with musical accuracy down to the lowest octaves. I achieved this by controlling phase interference. Just placing a box in the trunk will usually yield very poor response. you need to control phase interference caused by reflections in the trunk. Rear corners, wall loaded, corner loaded, etc. can achieve this. Check out my build log (link in sig).

Lastly, don't get your hopes up. Not having a lot of money doesn't mean you can't sound good. First - buy used. Second - learn how to work with wood and tools in order to fabricate the ideal enclosure and environment for your sound system.

Cheers!
 
  #3  
Old 10-21-2010, 11:35 PM
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in short, bridge the amp if the sub is 4 ohm SVC
 
  #4  
Old 10-22-2010, 11:42 AM
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Thanks hope, I expected the reply from you.
I have bridged the amp giving 300 watts rms to my 200 watts rms sub for now with gain **** turned almost till half and it sounds pretty good. If I raise the gain, then the sound from the sub woofer starts to overpower the sound from the rear speakers and also I dont want to blow the sub. I am happy with the current settings, but I am definitely looking forward to add one more 10" sub, but that will come later.
I am experimenting with the placement of the sub box in different places of the trunk to get the best sound. Right now, I have it facing the trunk opening(how conventional), and it sounds not bad.
And as you said, I am buying used stuff.

Thanks again, you keep the hope alive.
 
  #5  
Old 10-22-2010, 12:17 PM
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thanks for the complements.

instead of buying a second matching 10" sub, buy one nicer 10" sub. then your next purchase is one nicer sub amp - increasing build quality along the way. note that pairs of subs need to be equal.

the amp may be bridged for "300W RMS" but the sub will never see that. The actual power output varies with the volume level and recording level (i.e. input signal level at the amp), the impedance load (which varies with frequency for any speaker/sub), power supply voltage (output is more at 14V than at 12V), and the gain setting on the amplifier. The only way you'll ever see 300W RMS is if you play a 0dB test tone with gains set just before clipping while giving the amp 14.4 VDC at a frequency where the sub's impedance is at 4 ohms. This can occur during dynamic peaks in music, for a brief instant. And that's the key - you don't want to clip during those dynamic peaks, and you want them reproduced with sufficient output and clarity.

keep up the good work and remember that great sound systems are tweaked and honed over time, and the result of a lot of labor and love during installation.
 
  #6  
Old 10-23-2010, 03:54 PM
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Thanks for the detailed information hope. I am sure it will be useful for everyone else who have the questions similar to mine. I am looking forward a better 10 inch sub.

I am going to mount the amp today. I will be mounting it on the sub box. I am using a triangle ported sub box for this sub. I will certainly update on any kind of updates or changes that will come on my setup.

Thanks again.
 
  #7  
Old 10-23-2010, 04:08 PM
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PS to the above post:
I am trying to mount the amp to the back of the box, first on a MDF board and then the board to the box.

Before mounting it, I would want some advice on where to mount it?

option1:
The box itself has a kind of a slope of 75 degrees on any side of the box, have no flat surface on the top to mount the amp there. so I am going to mount it on the back of the box and hope that the amp will not take much vibrations. The box itself is going to be Velcro-ed to the trunk. Its not a huge heavy box so the velcro should hold it snug to the trunk.

option 2:
Velcro the amp mounted on the MDF to the side of the trunk.

Either way its going to sit on the vertical position. I can velcro it to the trunk floor horizontally as well. But I do not want any thing to hit the amp and snap the wires when I have stuff in the trunk. Come on, a student has all kinds of things in the trunk as car is kind of a second home for the student.

What do you say friends?
 
  #8  
Old 10-24-2010, 01:58 PM
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sub enclosure vibrations aren't of concern to the amp, so no issues there.

velcro won't hold in an accident or stop a thief. i always recommend securing a sub box with L-brackets.

mounting an amp to a sub box limits you in two ways - 1. removing the sub box (i.e. for additional trunk space) is now a huge chore, and 2. a thief can easily steal your whole system in under 30 seconds.

velcro isn't recommended for holding amps to anything - it will shift loose and it can short, spark, and start a fire.

you're right to mount the amp to a board, you just need to get the board screwed to something. the back seat, the side of the trunk, or the sub box are all viable options. if you mount the amp to the sub box, the box should be screwed to the trunk floor (careful of the fuel pump and spare tire!)
 

Last edited by keep_hope_alive; 10-24-2010 at 02:02 PM.
  #9  
Old 10-25-2010, 10:30 AM
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Yup, took your advice.
bolted the amp on the board and bolted it to the back of the sub box.
This setup makes it easier to get access to the amp controls from the back seat door that opens up to the trunk.

Just need to get some brackets to bolt the box to the trunk, Yah the sub box is still velcro-ed to the trunk floor right now.
I am not so comfortable with making holes in the trunk. If I am not confident then I will screw the amp board to the back seat. That way at least I know I am not poking holes through any important part of the trunk.
 
  #10  
Old 10-25-2010, 12:49 PM
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the floor of the trunk is usually a cardboard type material, even some short screws into that can work (again watch the screw length and location with the fuel pump and spare tire)

going through the trunk floor is the most secure, and doing so requires you pre-drill the hole to verify location relative to any suspension, fuel tank, etc. a bracket to the side of the side of the trunk may be easier as there are support braces that are accessible on both sides (not the rear quarter panels).

you can also use some construction adhesive and glue a 1x4 to teh floor then screw into that through the false floor. that way you aren't drilling through the floor.

where is the amp grounded?
 

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