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General => Car audio => Topic started by: blacfist on 04 February 2008, 20:28
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Hello 2 all,
ive fitted many systems in my time, but never come across this particular problem b4. ill describe it:
its a very basic setup, 4 channel head unit playing all the speakers inside the car, then a bridged 2channel amp running a single 12'' sub in a ported box.........simple really.
the system was playing perfectly till i decided to add some extra adjustment to the bass. i bought a passive (but powered) inline subwoofer filter. again, a very simple design. this unit adds no increase in sonic output just cuts out midrange sound from the bass signal (50/80/125 hz). the moment i placed this unit into the system, everything went 2 hell!! there was virtually no sound output from the sub at all with this unit in the system, so i decided to put things back the way they were. that made no difference. when the volume was turned up at the amp or at the headunit, the bass just popped and when it was turned back down again, it continued to make this sound. the sub was moving back and forth a lot and the lights in the car dimmed like the amp was working really hard.
any ideas?
thanks folks
bf
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i recon maybe ya filter has made ya amp throw a fit and possably f00ked it. filters do as described, restrict power flow to certain frequencys. so if ya amp is trying to push all its umppff throught ya filter and ya filters restricting it, it may of caused ya amp to of had a heart attack!
is your sub pulsing when you swich you head unit on? (without turning it up)
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hello,
yeah, pulsing, thats exactly the word for it!!
and yeah, it seems 2 do that constantly once the volume has been turned up, even after its been turned right back down again.
the filter goes b4 the amp, so its head unit - filter - amp - sub. as far as im aware, the filter itself should not have made any difference to the amp as such, the amp will just play wotever frequencies are put up it, does that make sense or have i got it wrong?
thanks again
bf
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from past experience`s with home and studio set ups filters always go between the amp and sound sorce, aka the speaker/sub etc.
when wireing old skool componants b4 filters built into amps, we used to use a xover, which worked... amp xover speaker/tweeter, a box of resisters and coils basicly that stopped certain frequencys getting to the designated componant, to stop you blowing them up!
have you got pics of your filter m8??
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hi,
no this unit goes b4 the amp, via standard phone plugs. i bought it on ebay, this is a link to the ad:
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&rd=1&item=220194698157&ssPageName=STRK:MEWN:IT&ih=012
thanks for help
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AAAAAAHHHHHHHHHHHHHH I SEE...
THATS PROPPA OLD SKOOL!!!!! oh the xr3 memorys!!!
this is what was used before rca outs were common on head units!!
so you have attached these to ya rear speaker outs of your head unit, then plugged the rca from that to ya amp correct?? (which is the correct way)
in which case, i would say the same sinario i suggested as b4, as you have turned it up, the resistance on the speaker out from head unit has caused it to throw hissy fit! (if you say it does this when you disconnect the crossover)
or
you have a dodgy earth..
or
there is a fault within the Xover which has inturn messed up your amp, aka your rca inputs, (these are very sensative to the correct impedence)
or
there is bare wire touching metel somewhere (maybe on the cage of ya head unit or in dash, are ya speaker connections insulated?)
the sub is pulsing because it it picking up power from somewhere that is not stable...(or a disterbance in power delivery,) like a serge of power going on then off again but really quickly??? if so that says to me a power sorce (amplification of some sort) is goin ape sh1t some were along the line. it could even be "bleeding" which is where 1 power sorce bleeds into another, (e.g like if your listning to radio at home and you turn on a light the radio wick "pop/ click) same princable.
i would suggest wiring just speakers to you head unit and if you have the pulsing then you know its ya head unit. if not ad ya amp and see if it pulses, so on & so on. do the same with all componants until eventually you will add something that causes the problem.
questions,
what head unit have you got?? does it not have a pre- out? (RCA out)
are your cables balanced, sheilded, even directional?? cheak your rca lead aint got arrows on it, i have had "directional" rca`s b4, never plugged em in the wrong way round but ya never know! (If there sheilded you wont have "bleeding")
have you tryed unbridgeing your sub to see if pulseing stops?
also i noticed you say you powered the Xover.. these are powered purly my the M.A`s of power that run through your speaker cable.
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ok
i understand completely
however, this crossover does not have a speaker level input, its rca in and rca out. then it has 2 cables for power. so you may have got it slightly confused with something else. it only works via rca inputs. the headunit is a new blaupunkt acapulco which has 2 sets of preouts as well as the usual 4 channels of speaker level outputs. the headunit works fine as far as the speaker outputs are concerned and was installed by myself on saturday, no issues there. but i take ur point on the pulsing thing.
as i said, all was perfectly well b4 this x/cross unit went and i kinda wish i hadnt messed with it (but thats life, u live and learn!!)i do get the feeling that the x/cross is entirely 2 blame!
ill spend some time approaching the problem with the aid of ur suggestions and we'll c wot happens. im gonna try another similar amp as well, if it works then the amp is buggered. i think the x/cross will find itself in the bin in either case.
again, many thanks for your thoughts. much appreciated
cheers
bf
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gotcha.... (my bad on the rca in out thing, didnt notice)
even so... if you want to filter out certain frequencys, i would recomend always putting a standerd Xover (unpowered) between the amp and sub. (in the same princable as speakers are built to split bass mid and treble to the relevant componant)
or buy an amp with hpf/lpf/full swiches already built in! its so much easyer!! :smiley:
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hi
tried another amp..........which works fine. havent put the filter back into the mix, im a bit scared!!
but im thinking that the 'input' side of the filter may well have been for speakers, not battery power!! the guy who sold seemed 2 think it was for battery power, but i get the impression he never actually used the unit himself so he'd never have known exactly how 2 wire it up!!
anyway, ill get the other amp repaired and give the filter another go, just without powering it up - rca in and out only. c wot happens!!
cheers
bf
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Can you not post up a piccy of the filter unit?
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sup heyho
the link above is 2 the ebay sale i bought it from. a good pic and description
actually, im not sure how 2 post pics here yet. ill try 2 figure it out.
thanks
bf