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 Post subject: Tuning the amp
PostPosted: Sun Dec 03, 2006 4:59 pm 
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Location: Winnipeg
There may be post that already has answered this, so ill take my chances asking it.

I need to know a little about tuning my amp hooked up to the set of 12's its hooked up to. Right now my bass doesn't sound right, i don't think its tuned well at all for my car. Anyways its a 94 geo hatchback 2 door. My amp is a monoblock and i haev 2 12" pioneer subs. My amp has a dial for the sensitivity, as well the lpf, and a switch to put to lpf or hpf. I need to know what i should set it to, this same setup sounded amazing (with a different deck) in my other cavalier, but not nearly the same effect in this car. the bass doesn't sound deep enough just really loud.


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PostPosted: Sun Dec 03, 2006 7:31 pm 
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Make sure the subs are wired in phase (+ to + & - to -).

LPF should be on and set it around 80Hz if it gives you an option. You can fiddle with it to find where you like it most but 80Hz is a good starting point.

Set the sensitivity about halfway. There is a proper way to set it but halfway should get you in the ballpark. Do a quick search on here to get the proper way or look up the JL Audio tech pages on their website.

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 Post subject:
PostPosted: Sat Dec 16, 2006 6:29 pm 
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are your subs dvc or svc if the are dvc the amp should not work
you should start the gain or sensitivety at half for starts then tune the lpf (low pass filter) at 60hertz turn your deck up to the loudest you will listen to it and slowly turn the gain up

make sure the box is facing back to the hatch caveliers and hatchbacks chang the sound of any subs


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 Post subject:
PostPosted: Sun Dec 17, 2006 9:13 pm 
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what does svc and dvc mean? they are wired up in series....i think, the amp is wired to the one sub then from that sub to the 2nd sub. and the box is a sealed enclosure. ok so when i get out there ill tune it to about 60hz, and the gain to about half. should i tune my decks sub cutoff to 80hz (the lowest). yeah right now i have the subs facing the hatch. when i say they dont sound right i don't mean they sound pitiful, just not quality like they did in my cavy. but yeah my main question was what ppl find to be the best low pass filter setting for our hatchbacks, so yeah ill try 60 hz, thanx.


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PostPosted: Mon Dec 18, 2006 7:51 am 
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svc = single voice coil, dvc = dual voice coil.

that bit about a dvc sub meaning that your amp won't work is bad info. it's the combined impedance of the voice coils vs. the lowest impedance your amp will drive that matters.

the lpf means low pass filter frequency and it is just a filter that will pass frequencies below it's set point. your sub and enclosure will have a tuned frequency that will allow the speaker to play up to a certain frequency, say 100 hertz. if you set the lpf to 60 hertz it will play up to 60hz (the -3db knee point where bass response is reduced by half output) and then the speaker's output will start to attenuate at whatever rolloff the filter is designed for due to the amp limiting the frequencies it will pass.

you don't want to throw a lot of power at the sub in it's enclosure above the tuning point, it's just a waste of power that will heat up the voice coil without producing any (much) sound. that point is dictated by the speaker's interaction with the enclosure and it's port arrangement (assuming that it's a ported enclosure.) if it's a bandpass style box, applying a lot of power above the box's design spec can be dangerous to the speaker.

the useful function of the low pass filter is to allow you to tune the amp's output to the sub's mechanical/ acoustic cutoff point. it also allows you to match the sub's output to your main speaker's cutoff point for the proper crossing over of low frequencies to the upper bass/ lower midrange pint of the overall system.

80 hz is a good place to start. depending on the sub and enclosure, you might be able to take the sub up to something around 120 hz to closer match the crossover point of the main speakers. unless you run something like an 8" mid bass, setting the lpf to 60 hz is most likely to just produce a glaring gap in the frequency range between 60 hz and 120/ 150 hz. if you're using the standard fit 4" speakers in your metro's system i can safely say that the speakers won't reproduce anything below 150hz. even with your sub amp's lpf set to 120hz you'll get a big dip in the system response between 120 and 150 hz.

you might get a better sound from your system in the little hatchback if you raise the lpf set point. you can also play around with the sub position to find the best coupling (and best bass response.) in a metro 3 door i prefer loading a single sub to the driver's side and facing the speaker across the space pointing at the passenger's side. my second choice is in the center facing up to acoustically couple with the roof. experiment with the sub's placement to find the bass sound wave re-inforcement you like best.

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 Post subject:
PostPosted: Mon Dec 18, 2006 12:30 pm 
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t3 ragtop wrote:
you don't want to throw a lot of power at the sub in it's enclosure above the tuning point, it's just a waste of power that will heat up the voice coil without producing any (much) sound.


Actualy its the reverse ;)...lots of power below tunning will pop the sub and above tunning is OK. Below tunning the subwoofer doesn't "see" the enclosure anymore and acts as it would if you applied that power to it out of an enclosure.

I think Ricahard was talking about a bandpass enclosure though where it gets a little more tricky. Bandpass has a great (and bad) tendency to filter out the sound of distortion because of its nature to filter out upper harmonics (which is usualy where you will hear the distortion) out of the passband...you don't hear the sub stressing until its too late.

I still say set the LPF at 80Hz and work from there. Unless you have truly incredible front speakers that play well down to 70 or so Hz a 60Hz point will leave you with a nasty hole in the spectrum. Not to say it can't be done though...my old system was low passed at 40Hz and the fronts played down to 50Hz very well. What kind of music do you listen to? Most rock music likes a setting a little higher like 90-100Hz....stuff with low bass like reggae can benefit from a 60-70Hz low pass as it cleans up the muddier upper bass harmonics. 80Hz is a nice compromise and is a good starting point. Use music you know well to set it and you'll be happy with the outcome.

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 Post subject:
PostPosted: Mon Dec 18, 2006 2:24 pm 
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yep m, i was thinking of a bandpass box. i was reading this thread after reading one in the vert section and got stuck on bandpass enclosures (which i really don't care for.)

i even missed the original author's statement that he's using a sealed box in his application. :lol: in that case you can always crank up the applied power to compensate for the enclosure's reduced acoustic output.

you're advice is always sound and you're right that 80 hz is a good place to start. in the end i expect that the lpf frequency will be higher to compensate for that hole in the system that the main speakers will surely leave given that the factory locations take a 4" speaker for the mk2/3 models. the mk4/ 5 models take a 5 1/4" (or even a 6 1/2") speaker and have a bit more bass extension when you use a good quality speaker.

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1991 Blue Geo Metro Convertible highly modified 1.0L Turbo3 5 spd. - 1991 Red Geo Metro Convertible customized with a Twincam 5 spd.

My Turbo3 Project
My Cardomain Page -Ol' Blue
My YouTube Channel
My Photo Gallery
SAAB Sonett II


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 Post subject:
PostPosted: Wed Dec 20, 2006 2:20 am 
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alright so im gonna tune it to around 80 then with the dip in mind, and for the different styles of music rap to rock ill just change the lpf on the deck from there if i need to tune it lower to like 50 or 60 for the rap that really benefits from tuning it low.

so under tuning the amp is bad, so ill watch out for that. its just some songs i find myself turning the bass down alot because theres too much bass in areas where it sounds bad, almost like its in places not meant.

http://www.infinitysystems.com/caraudio ... EF&Cat=MEL

those are the 4 speakers i have so they must be pretty good since they can reproduce as low as 85hz. btw i would recommend infiniti's they sound amazing, very very good highs.


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 Post subject:
PostPosted: Wed Dec 20, 2006 1:19 pm 
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The spec is largely useless without an accompanying response chart. The 4" speaker will likely do 25Hz and do it loudly when you have it cupped to your head like a headphone. In a car your not going to get under 150Hz with that thing at any kind of realistic volume. Not saying the speakers are bad but just illustrating the limitations of a driver that small. Even speakers 3-4 times the price of yours are gonna crap out somewhere under the 150Hz mark unless they are built as a subwoffer...then you might get down to 100Hz with a well designed enclosure.

That being said you may not notice the hole in your frequency spectrum if you're not used to having it to begin with. I'd say tune it as best you can and then enjoy the music that you have. You can always upgrade later if you get to the point that you want more...and we can show you the way down that road too ;).

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