gain and bass boost settings

[joshsvs]

i am trying to figure out the best settings for my amp.
i have a 4 channel amp with 2 channels bridged to power a 12" sub.
the amp has hpf,lpf,gain, bass boost adjustment.
ive noticed that bass of the sub can be increased by either increasing the gain or increasing the bass boost.
so which one am i better to use to adjust the loudness of the sub, and which will create better SQ?
and by turning one or the other up, which one creates a greater current draw in the amp?

[Ra1d]

gain is actual draw and 'bass boost' can just be a gimmick that adjusts the output frequency to make out your getting more bass. lpf and hpf, thats high pass and low pass and should be adjusted to within the hz range of your sub. basically your just need to match or tune your amp to the specs of your sub, which should be outlined in the operators manual. furthermore, you shouldnt need to put your gain over halfway, as it can create distortion. if you feel you need to put the gain over half to get your subs to perform, your amp is probably too small....

[joshsvs]

gain is actual draw and 'bass boost' can just be a gimmick that adjusts the output frequency to make out your getting more bass. lpf and hpf, thats high pass and low pass and should be adjusted to within the hz range of your sub. basically your just need to match or tune your amp to the specs of your sub, which should be outlined in the operators manual. furthermore, you shouldnt need to put your gain over halfway, as it can create distortion. if you feel you need to put the gain over half to get your subs to perform, your amp is probably too small....

yeah i know about low pass filters and high pass filters.
it was just gain and bass boost im not sure about.
and if i put the gain over about a third the sub is too loud so the amp is definately big enough

but is it better to have the gain turned up or the bass boost turned up?

[Joe Peeps]

bass boost off, set the level with the gain

i should add that bass boost increases the output at a particular frequency at the expense of other frequencies - on some amps this frequency is fixed, on others it is variable. its not like free power or anything - better off without it IMO.

Also, the gain is a means of matching the signal voltage from the HU to the amp - having it over half way wont "create" distortion (although generally the higher the gain the more potential for noise floor issues but this is not such a huge deal with subbass) but what can happen is people up the gain and introduce clipping and thus potentially cook their subs.

[| evaN |]

bass boost off, set the level with the gain

Thats how i prefer it. Bass boost off with the lpf filter at around 75hz. Anything higher and people with deeper voices come through the sub which sounds like crap

[clyde]

so with all your filters you have to set them to frequency range of the speaker? my amp that i have atm only has a set on/off switch for the lpf and hpf, and is a set value that i cant change. this because its a cheap amp? also my hu has filter settings as well. would i be better off using the hu controls or the controls on the amp? or dosent it matter?

[Joe Peeps]

so with all your filters you have to set them to frequency range of the speaker? my amp that i have atm only has a set on/off switch for the lpf and hpf, and is a set value that i cant change. this because its a cheap amp? also my hu has filter settings as well. would i be better off using the hu controls or the controls on the amp? or dosent it matter?

No, you dont have to set them to the freq range of the speakers. If your amp filters cannot be changed, then its better to use the HU ones - dont use both in your position

There is no hard and fast rules. Without knowing your set up and tastes we cant tell you were to put them, but wherever they sound best to you (underlap is sometimes preferable ie a sub LP of 80 say, and a HP of 100 for the fronts) the better the quality fronts your running, the lower you can High pass them. Everything is a compromise

[garfa]

more over some blokes gets their gains set correctly then ADD bass boost and make their subs get too much power, and this can result in the cone getting over excursed with damage to the vc and/or cone/suround or just plain melting of the vc.

ra1d: you set the x-overs more to the box than the sub. just because your sub can play to 40hz does not mean the box has a roll off of below that.
its should be more like ub-->box designed for sub-->x-overs set to around your sub in that specific box's limits-->adjust according to taste.
and as said before if the amp supprts upto 8v input and your h/u is 2v then it wil be over 1/2 gain probably. in theory the gain will only increase the possibilty of increasing the noise NOT creat it, just thought that needed clarification.

[Ra1d]

well yes naturally there are plenty of variables. correct me if im wrong but the majority of hu's under the $400 mark for example, generally have <2V pre-outs so i didnt factor that in. eclipse is the only deck ive had that was a contrary to this, having a 5+volt pre-out. when i said tune the amp by operators manual i assumed the average person would know to look at the specs relevant to their particular enclosure. take it easy....still learning over here

[Joe Peeps]

Relax man, noones having a go at anyone - he is just sharing his knowledge in a constructive manner. We are all constantly learning - instead of arcing up look at your post and Garfas post and learn from it.

we shouldnt give advice and make statements without full knowledge of the system without caveat so all is good, look forward to further contributions from you to the forum

[JBDrifter]

Hope this ain't against any rules or anything, but here's a link to another forum topic containing all the info plus directions on how to set gains properly that you'll ever need. Hope it helps.

Tutorial - Amplifier Gain & Crossover Adjustment - Mobile Electronics Australia