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voice coming out of subwoofers

4K views 17 replies 8 participants last post by  SWortham 
#1 ·
i have 2 12" subs and i had them installed by some1 else cuz i dont know how... but is it right for Voice to come out of the subs? a friend told me id lose base if im getting voice..... and the way its set up is with the factory head unit and when i turn the back speakers off the subs turn off too... is that ok?
Also my tweeters blew ( i think).... will this cause any problems?
 
#2 ·
The reason your subs turn off with the rear speakers is the amp is getting its signal from the rear speakers themselves. Its called a high level output. If you had an aftermarket headunit with preouts, that wouldnt happen anymore. You have voice coming out of the subs because the crossover on the amp is set too high so higher frequencies are being sent to the sub. That or the voice is low enough that it gets pass through anyway. You have to set that lower.
 
#5 ·
a crossover? what is that and how is it installed
 
#6 · (Edited)
well there are two basic types: active or passive. either way, they are simple circuits designed to block out either high frequencies (called low-pass) or low frequencies (called high-pass) from a full-range signal, so that you can route the appropriate frequencies to the appropriate driver (speaker). for example, if you didn't block the low frequencies from going to the tweeter, it would blow pretty quickly since low frequencies require more speaker cone movement. you may have noticed on the back of a 2-way coaxial speaker there is a little cylinder through which the positive wire runs on its way to the tweeter. that's a very simple high-pass filter.

sending full range signals to your subwoofers will make it sound muddy (but it won't cause any damage). typically, you send low-pass frequencies to the subwoofer-- anything below 75-100Hz. voice is typically in the 300-3000Hz range, and in most setups is handled by the woofer or midrange.

active crossovers work on the unamplified signal, sending the high- and low-pass signals to the amp, and the amp sends them on to the speakers. passive crossovers work on the amplified signal, between the amp and the speakers. active crossovers are also known as signal processors or electronic crossovers.

the idea here is that each range of frequencies is reproduced by the appropriate driver, providing much more accurate and clean sound.
 
#7 ·
Here's a guide on crossover basics from Rockford fosgate

Crossover

It installs either before or after your Amplifier. Some Amplifiers already have them built in. You may want to consult your Amplifiers manual to see if it has one.
 
#8 ·
You're best off getting one that installs before the amp. As Jacksonj says, some amps (and some head units) have a crossover built into them.

As an aside: Boy we're lucky to have southpawboston contributing to this forum; He knows electronics and he's one of the best people I've read for presenting technical information for the layman.
 
#9 · (Edited)
Yes SPB is very helpful as is many others on this forum and we are lucky to have these forums :)

i have scanned through the manual and it says
Crossover Range:
high pass: .
low pass, 24db/octave: 40-460hz
 
#12 · (Edited)
Yeah, that'll help. And good work SouthpawBoston. :thumbsup:

I just wanted to add a few things...
The point at which you should cross it over kinda depends on your other speakers. Ideally you would cross it over at something even lower like 100Hz... but your door speakers may not produce enough low-end to produce a full sound when combined with the sub. And you wouldn't want any gap or a weak range of frequencies. So really I'd just tweak the crossover point a little until it sounds the best. 150 may be about right, so you could start from there.
 
#13 ·
If you still have the subs manual it will tell what their preferred operating frequency range is or you can look it probably find it on their product website maybe?
 
#14 · (Edited)
Well the preferred operating range for the sub probably won't help you. It's more about the door speaker's limitations.

And I can tell you why... it has to do with creating a good soundstage. Low frequencies can seem to come from all around you. The lower the frequency, the more 'omnipresent' the sound will be. But once you enter the 80Hz+ territory it starts to become more obvious where the sound is coming from. If you crossover the sub too high, you'll be sending frequencies to it which will sound kinda funny since you'll be hearing those frequencies behind you. It would sound better if they were coming from the front door speakers as if you're at a concert and you can hear the stereo separation. But there is a compromise that comes into play since you just don't want to push any bass out of the door speakers that they can't produce cleanly.
 
#15 · (Edited)
Maybe I'm not understanding his setup, but I was under the impression that he's spliced the signal from the rear speakers to an amp which is powering some subs, right? So the speakers are just getting their power from the stock headunit, so he can adjust the crossover to the subs and not worry about the rest. Of course you'd want to adjust the bass on the headunit down so that the interior speakers only have to worry about producing mid and high, something they are better suited for, the amp should take care of the bass for the subs.
 
#16 · (Edited)
Oh yeah, you're right. That could be kinda limiting. For example, how would you apply a high-pass filter on the speakers through the head unit without also applying it to the sub? It would be nice if the head unit simply had a separate output for the sub. Or you could install custom high pass filters for the fronts behind the head unit and for the rears inside the trunk.

Some of what I said still applies. Like I said, you should be able to tweak it until it sounds the best. [I'm not really audiophile kind of guy, this is just stuff I've picked up from my audiophile brother. So don't ask me for details, haha.]
 
#17 · (Edited)
SWortham said:
The point at which you should cross it over kinda depends on your other speakers. Ideally you would cross it over at something even lower like 100Hz... but your door speakers may not produce enough low-end to produce a full sound when combined with the sub. And you wouldn't want any gap or a weak range of frequencies. So really I'd just tweak the crossover point a little until it sounds the best. 150 may be about right, so you could start from there.
you're totally right about the crossover point being relative to the dynamics of what's already in the car. and ideally, i would agree with you point about crossing over lower, like 100 (or even 85). but in his case, he's got a 24db/octave cutoff slope. that's steep. that means that for frequenices above the high crossover point, they are going to drop off like a cliff. this allows the initial crossover point to be a bit higher. it's more common to have a 12 or 18db per octave slope. but you are right-- he has to tweak it and see what sounds best in his car. i just gave out a ballpark off-the-cuff number.

as for not having a gap between frequencies-- you actually do want a mid-bass gap, roughly encompassing the octave between 85 and 170 hz. it's been shown that a car in motion generates a mid-bass peak around that range. if you kept the audio system flat across that spectrum, you will hear a mid-bass peak, which is really road noise layered on top of the audio signal. having what's called a staggered crossover helps flatten out that perceived peak. for example, my old-school soundstream 5-channel amp has a built-in staggered crossover with non-adjustable settings. it sends a low pass at 85hz/12db/octave to the sub channel and a high pass at 170hz/6db/octave to the four main channels. the thing is, there's always been debate about the practicality of this type of setup. most hardcore SQ competitors don't care about how their stereo sounds on the road. their only concern is about how it sounds parked in the judging lane. a competitor will have points deducted if there is a gap perceived. but on the road, you want that gap.
 
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