How does bass boost work?

[Hyun]

In my effort to understand how bass boost works for my amplifier, i emailed my manufacturer. I got curious because the manual states that every boosting of 3dB up to a max of 18dB at the 45Hz level (called Bass Boost) requires twice the amount of power.

 

I was worried because it may draw more power for the amp and pump too much and maybe blow speaker.

 

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The reply is as follows:

 

To first understand the bass boost you must first understand that it is essentially a narrow Q single band equalizer, essentially when you increase the level it does in fact affect the levels of surrounding frequencies to some extent in a very narrow bandwidth. The next thing needed to know is the 3 db rule, 3db is a noticeable increase in output to the human ear, in order to gain 3db of output you must either double the power or double the speaker surface area. You are not sending more power to the given speaker you are just increasing the power which is focused at that specific signal range.

 

As long as the amplifier is adjusted properly you will not have a problem with overpowering the sub, you will in fact have better control over it which results in greater dynamic range and accuracy.

 

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I suppose, as they say, think of it as a single channnel EQ and u'll appreciate what it does. does anyone else have comments about how they use bass boost in their car, how they tune their sub, and the sub-to-midbass transition/crossover ...?

[K2000]

sometimes back i was asking this question in another forum, most of them do not recommend to turn on bass boost

[Sarong1]

My mono happens to have this bass boost function. I have recently attempted to give a bass boost at 25Hz but slightly merely. The effect is noticeably feelable but I think it should be attempted with caution. Too much of which will sink the rest of the freq, making the focus from the bass irregular or difficult to dictate where its coming from, I am talking about SQ. We may discuss in greater details when we meet.

 

Side track a bit, quite some time back during my EQing discourse, I realised that the bass and sub effect that I have audited in many cars have not been well-represented or displayed. I am indeed WOW by the effect of the sub but am not truly impressed if I am listening to it as a total reproduction of the music, that, I am refering to the harmony of the subranges in relation to the intergrity of the music.

 

During the EQing process, I have selected a wide range of genre, especially from classical music (Telarc) to determine if my bass level was just nice. The music i chose also included Track 11 from the IASCA CD 2005.

 

What I have learnt today is without the assistance of Time Alignment. Like what I have shared during the recent meetup, the experience that you have learnt from EQing by yourself will enable you to resolve problems that most people are still doubting today.

[Hyun]

i resorted to using bass boost, despite saying i wont use it, because:

 

i felt my sub needed more rumble. playing frequencies, i get flat responses at 50 hz, 63 hz, 40 hz. but as i drop to 31.5 hz and 25 hz the sub drops in response .. about 50-60% output at 31.5hz compared to 50hz, and at 25hz the effect is like 10-15% or so.

 

i only want to boost 50hz and below, the non-audible ranges. if i boost up the audible ranges, there would be that boomy sound that's audible.

 

to solve this problem there were 3 ways, as we mentioned. 1) increase gain. 2) bass boost. 3) using EQ.

 

3) my EQ only had a 50hz band so that was out of the question - i cant boost sub-40hz without touching 50hz and 63hz.

 

1) increase gain doesn't work because the entire sub output goes up. despite setting LPF at 44hz with -24db/oct slope, one octave up from 44hz is 88hz. therefore i still get an increased output at 63hz, 70 odd hz when i increase gain despite having a 44hz LPF. this generates increased audible boom which i dont want.

 

that leaves method 2) bass boost at 45hz. my amp doesn't have 25hz bass boost like yours has, so i have to make do with 45hz boost. the benefit of bass boost, for my scenario, was that it works just like what i needed - a single band EQ. it boosted 45 hz and the surrounding, with palpable effect down to 25hz, miniscule effect at 20hz, and it doesn't affect 63hz too much. at 80hz it hardly has effect. therefore i'm able to boost non-audible bass, and use the 44hz LPF at -24db/oct to chop off the audible range.

 

the overall GAIN has not increased - so that makes it easy to chop off the 63-80+hz region using the LPF, because that range has not been boosted too much. whereas comparing with option 1) of increasing overall gain, the LPF would not be able to chop 63-80hz equally well, because gain has increased - 63-80hz output has risen due to gain.

 

the key difference here is that gain affects all frequences - including the unwanted ones above 50hz, making it hard to chop them off with LPF. bass boost affects a more isolated band, leaving the unwanted freqs still relatively "ungained" and easy to chop off.

 

 

that's my understanding of how to handle bass boosting so far, after some experimentation. i do not know how the technicalities work, how bass boost may or may not ruin SQ, why people advise not using it etc. maybe someone else might know.

 

p.s. Sarong, i saw your thread on "which frequencies do what" :) useful. thanks!

[Sarong1]

Hyun, a lot of the sub ranges need a high wattage (powerful) amp to pump out. That is one reason why subwoofer amps are generally higher in power rating compared with those that are merely driving the front component.

 

Since your system is riding on a single amp, the consumption by your front and sub add together could be more than your current amp can handle, that I am not sure.

 

That was the reason why it would be better if a delicate amp is used to drive your sub. Granted that your sub is not power hungry, you need the power to sustain the sub ranges in some instances, i.e. the control of your sub.

 

Kermit was also using the same sub as you. Previously, he was using a 4-ch amp to drive his front and the sub, but the amp was just too weak to sustain both the front and the sub effectively. He has got no choice but to get a old school Hifonics to drive his sub now. What he has achieved now is the control, its not lagging and can deliver and tarik back on time (much faster than our home delivery services).

 

My advice for you, if you want to maximise the potential of your sub, is to get another sub-delicate amp if you want the sonic effect below 40Hz...

 

Remember, manupulating too much of your 63Hz, 50 and 40Hz will create the boomy effect. Tune it with caution.

[Hyun]

yup i'm trying to enhance sub-50hz without touching too much of 50+hz. but without a sub EQ it's pretty darn difficult :(

 

Kermit .. err i get confused with nicks.. who's Kermit? driving which car? only about 2-3 people using this sub hor ..

 

as for whether the power can be sustained, on paper by right it can, but whether there is control or not, as u witnessed that day, maybe not. i should play some sub tracks if Kermit wont mind, on his car, and then on mine, and see how much dampening difference there is.

 

u mentioned really low freqs require lots of power .. all the more i'm afraid i'm pumping too much into the sub. without an ampmeter, a bit hard to agar-agar. right now i'm putting in 400W but at a gain of about 2 o'clock on the dial out of a minimum of 7 o'clock and max of 5 o'clock - so that's about 70% of a full turn. estimating about 70% x 400 = 280W. the sub is 175W RMS. any1 got a portable ampmeter?

[Sarong1]

Kermit is driving the Peugeot.

 

Given that the wattage supplied to your sub is at 280W, you will also need to remember that there are considerably loss of wattage along the way. So effectively, there aren't lots of power fed into your sub really.

 

Your sub will the most draw 175W from your amp I suppose.

 

I will coerce Kermit to drop by this coming Wed.