How do I get my system louder?

Posted on 27. Jul, 2009 by in Industry News

One of the greatest tools in the audiophile toolbox is math. What? Math sucks you say. Well I say get your calculators out and start working your brain. This will be fun, honest.

In retail, chat forums and lunch rooms across the country the single most common questions are “how do I get my system louder” or “how loud will these subs be”. I can personally guarantee you that you ask ten people this question, including the guys at the stereo shop, you will get 13 different answers and none of them will be basing their answers on facts. They simply do not know how it works. There are some basic physics at work here.

Volume, which is measured in decibels (expressed by dB), is a function of power, cone area, enclosure design, and transfer function. Oh, you knew that already? Ok, sure that last statement might seem a little obvious, but undestanding how they interact togethr is critical to calculating volume. That’s right, you can calculate exactly how loud you system will be. Enough BS, here is the worksheet. You won’t find this anywhere else, send your friends.

This formula requires a few specs. First, you need the sensitivity of the sub(s). This listed on the woofer spec sheet in dB. It is sometimes notated as the SPL of the sub. Next, you need to know how much power your amp puts out. An amp birth-sheet (usually included in the box) will have the actual power the amp displayed when it was tested at the factory. Not all amps come with these. If you do not have such a sheet, you can use the power ratings, or even better, you can test it yourself (that is whole other enchilada and we will get into that another time). Other specs you need are more simple- what type of car do you have- truck, hatchback, or sedan; and what kind of box is it installed in. The enclosure will make a big difference, if it is a crappy home-built box with lots of leaks, held together with carpet and liquid nails, it probably won’t function as well as a professionally-built enclosure (like the Q-Logic pre-fab enclosures- shameless plug) and how many woofers you have. Have fun.

Sensitivity =

Every time the cone area doubles, the output of the system increases by 3 dB, which is relative to a doubling of volume. If you have 4 subs, you would add 9 dB to the sensitivity rating of the subwoofers.

add 3 dB per doubling of cone area

i.e. 2 subs, 3 dB, 4 subs, 6 dB

Let’s consider sub sensitivity, with 3 dB per sub added and calculate the SPL. Each time the output power (wattage) of the amplifier doubles, the SPL increases by 3 dB. To figure this, use the following figures.

This represent 3 dB added per doubling of power starting at 1 watt/meter SPL.















Next we add in Transfer Function

add 12 dB for a standard car/truck

add 16 dB for a hatchback car

Now we figure in box type

For a sealed box, 0 dB, sealed offers no dB gain.

For a ported box, 3-9 dB depending on tuning frequency and air ripple. The higher the ripple, the more gain but at a cost of sound quality.

For a bandpass box, 6-12 dB again depending on the tune freq. and ripple.

For example, a 12″ Rockford Fosgate subwoofer has a sensitivity of 86 db at 1 watt/1 meter, and is capable of handling 300 watts.The sub is installed in a ported enclosure, so we are going to use a

the lower output rate for the ported box at 3 dB. Powering the subwoofer is a Rockford Fosgate Punch 300-1, which is rated at 300 watts to a single 4-ohm load. All of this is installed in a 2006 Honda Civic Si, which is a hatchback and gets a boost from the 16 dB transfer function. Using the formula, we get the following results-

86+ 24 (at 256 watts, it is close, but you could add in an extra dB if you want) + 16 (trans function) + 3 (box gain) = 129 dB estimated output. This estimation will be within +\- 3 dB of the measured output. This is simple physics, and it works.


80 Responses to “How do I get my system louder?”

  1. Mike

    02. May, 2014

    Ok I have a 1200 hifonics hooked up to 2 ’12 alpine type R’s in a imported box in a van. How should my setting be on the amp.? Dont understand why it its sounding the way I thought it would.

    Reply to this comment
  2. sequan

    29. Jun, 2014

    Hello ! Im starting my first system. I have 2 Q power 10′in subs in a Bandpass box with 2 port tubes at the top…the system is 4 ohms and handling 1200 watts total with 600 rms…… My uncle gave me a Sony Xplode amp that’s 760 watts 2 channel , big amp but I was wondering if I bridge it to 4 ohms would that make the sound that much lower since its only 760 watts and my original system is 1200 watts 4 ohms already ?

    Reply to this comment
  3. sequan

    11. Jul, 2014

    I have 2 10″ Q power sub’s 4ohms in a bandpass box with 2 port tubes that’s 1200watts….. Can my 760watt 1/2 channel sony amp power them good? This is my first system…??

    Reply to this comment
  4. trenton henley

    11. Sep, 2014

    what do u think about me pushing one kicker 15”comp with a pioneer 760 watt amp good idea or not?

    Reply to this comment
  5. Jason

    23. Oct, 2014

    This isn’t very accurate, because I have the pioneer w1200 pro’s that have 105db sensitivity, and they each take 500rms, for a total of 1000.
    135+12db car gain= 147
    147+3(ported box) + 3(second woofer)= around 155decibels…
    I highly doubt I’ll hit anywhere close to 155 decibels offf 2 12′s on 1000 watts in a trunk car lol, Steve Meade does 157 with 4 18′s on 30k.

    I personally think the sensitivity ratings don’t really appl to cars as much because rattling trunk and car panels etc, so 105db would probably be closer to a 93 db sub.

    Reply to this comment
  6. Tama

    26. Oct, 2014

    I have a pioneer fa-x755bt head unit,pioneer Gm-d8604 class FD 1200watt max champion series amplifier and a 12inch 1400watt pioneer subwoofer. The thing is since I’m in Fiji there isn’t much tech support with the quality of sound as they just sell whatever enclosures they have. As for me I designed and built mine with my bear hands according to the manuals in the boxes. I made a ported box and was really impressed with the sound and the quality. My question is would I be able to connect a second subwoofer of the same type and not harm my amp? I also have a problem. I have a new battery installed but my lights still go dim when the bass hits, what rating should the capacitor installed be?
    At the moment I’m running the pioneer sub with a 10inch boshman sub and the amp seems to be holding perfectly with no signs of overheating.

    Would really love the help from the experts.

    Reply to this comment
    • Chris@QLogic


      18. Nov, 2014

      There are many factors left out that I would need to know.

      What is the resistance of your woofers?
      What kind of car do you have and what size alternator does it have?
      What size wire are you running for power and ground?

      Maybe you don’t need a capacitor it just depends on a few factors.

      Reply to this comment
  7. brett

    17. Nov, 2014

    OK question I have a Hispanics Brutus next 1200 Watt mono block amp and two Rockford fosgate 12 ” P2D4 in a Turbo bass pro box what should my amp be set to for perfect sound quality and power and they are wired down to one ohm.

    Reply to this comment
    • Chris@QLogic


      18. Nov, 2014

      This is a question that can not be answered over the internet unless you have the correct tools to do the adjustments. You would really need a DMM or an Oscilloscope with a audio test CD to do it properly. I recommend you go to a local car stereo shop in your area and have them tune it for you. If you would like help finding someone in your area let me know and I would be more than happy to help.

      Thank you so much for the question!

      Reply to this comment
  8. brett

    17. Nov, 2014

    Sorry hifonics *

    Reply to this comment
  9. Chris@QLogic


    18. Nov, 2014

    @Jason It is possible but we always have realize this is in all in theory. There are many factors that can change these number for example how the wave moves through the car and even if there are any waves that actually cancel each other out.

    I hope this helps!

    Reply to this comment
  10. Nick

    19. Nov, 2014

    Hey Jefferson,
    I Just Bought Two Kicker CVR’s In A Kicker CVR Enclosure And I’m Running Them Bridged on A Legacy 4 Channel 1600w Amp. I Can’t Seem To Get The Tuning Right On The Amp, I Turned the Low.pass Filter Almost All The Way Down And They Hit Hard But It’s Not Really Quality. Bad Amp For The Subs Or Something Else? Thanks


    Reply to this comment
    • Chris@QLogic


      21. Nov, 2014

      Hey Nick, Jefferson doesn’t post here any more but I would more than happy to answer you question. I would say that you could probably make that amplifier work but you may run into two issues.

      First, most likely that amplifier does not make enough wattage to power those woofers properly. The amp may say 1600W max but the realistic output of that amplifier will probably be much lower. If you want to give me a model number I would be more than happy to help you figure out the correct output power.

      Secondly, a 4 Channel amplifier was really designed to run door speakers and not woofers. The crossovers that are built into that amplifier are really not made to do what you are trying to do. There are ways to get around this but I would need to know a lot more about your system first.

      I hope that this helps and if you have any other questions you can message me here or on twitter at @CarAudioChris on twitter:

      Reply to this comment
  11. cameron

    29. Nov, 2014

    I have a 15″, powered by a 200W 2channel amp. How do I make it beat harder?

    Reply to this comment
  12. Casey

    16. Dec, 2014

    Man I ain’t trying to be a jerk but your not the greatest at explaining something. So explain where the +24 came from and on the ported volume it says 3-9db. What would cause a box to have lower db cause it doesn’t state a volume range like for example from .5-.6 volume be +3db. Like for my sub the recommended ported box should be 1.25 volume. So what would that be in the range of 3-9db? And you didn’t explain how the wattage converts to db. I have a 12″ sub with the spl rating of 85db. It handles 850 watts rms. my amp pushes 700 @ 2ohms. I want to run the sub at 600 rms so I should be in any danger at all with possible over doing my amp. And I have it in a c6 corvette. So since it doesn’t have back seats and it’s all one open can with a trunk, how does that categorize it?

    Reply to this comment
  13. @CarAudioChris


    18. Dec, 2014

    Hello Casey,

    I am sorry for the confusion on this article. Jefferson is no longer here so let me see if I can help you out on your car. I though maybe it would be better if we attacked your questions one at a time but I wanted to see if you could list out each questions individually and I will respond accordingly.

    Thanks a bunch my friend and I hope that I can get this answered for your as soon as possible.

    Reply to this comment
  14. matt

    28. Dec, 2014

    I have alpine type r and a 800watt phoenix gold amp in my ext cab truck …I’ve hears alpines do alot more work than wat mine is doing my box too big or do I need to make a different one..I have a huge side ported slot style port .plz an thank yu ..matt

    Reply to this comment
  15. Trevor

    08. Jan, 2015

    i have 2 15s what amp should i get for them

    Reply to this comment
  16. rivera82

    17. Jan, 2015

    I have a 09 versa hatchback I just got in stall a 400 watts 4 channel Jensen amp and 2 10′ inch Kenwood subwoofers they each are 500watts and my stereo is a pioneer do you think is a good idea running the subwoofers with just that amp that’s running with the speakers inside the car,I mean I notice it those sounds good and people tells me is not bad but should I get a amp for the subwoofers or is ok with the amp I have?

    Reply to this comment
    • @CarAudioChris


      19. Jan, 2015

      A 4 channel amp isn’t a horrible choice but it definitely isn’t ideal. I would leave it as it is right now and start to save up for a more suitable sub amplifier. What are the specs on that woofer? I recognize it but I am not sure which it is.

      Reply to this comment
  17. rivera82

    20. Jan, 2015

    To tell you the truth I don’t know what are the specs on the woofers all I know that each are 500watts thats all sorry but I’ll take your advice and thank you!

    Reply to this comment
    • @CarAudioChris


      20. Jan, 2015

      Is there any way you could get me a model number? You may have to pull the speaker out but it would be the best idea to make sure and purchase the correct amplifier.

      Thank you!

      Reply to this comment
      • rivera82

        21. Jan, 2015

        Hey one question,ok every time I accelerate or press the gas pedal and the car starts to run and it makes this squeaky and beepy annoying sounds and someone told me its cause maybe my stereo was install wrong or some cables or connections are set or install wrong or maybe some cables are touching each other any ideas or tips or advice on how to stop those noices or sounds to stop wen the car is running and I press the gas pedal?

        Reply to this comment
  18. rivera82

    21. Jan, 2015

    Ok I will I’m gonna go ahead and find out the model # and let you know asap thanks Chris

    Reply to this comment

Leave a Reply