question for you guys to settle debate

[davidwm88]

Alright today i was at a table with friends when a coversation about car audio came up. First I was joking and said I wanna put a wall of subs in my room, like car audio shops. Then one kid says, just hook your subs to a home audio amp instead of using power supplies. I dont think this will work because of impedence but he swears by it and says he is using a 10 inch , forgot which one, as his bass right now. Can you do this?

Also he said you can tune a sub to 80 hz and it will sound good. I said that would sound like shit. I said you cant play 80 hz but tuning it would be extremely bad. What is the opinon on this? I admit I am not sure what tuning a sub to 80 hz would do and if you could explain it would be great. thanks agian guys.

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[squeak9798 5,000+ posts]

Alright today i was at a table with friends when a coversation about car audio came up. First I was joking and said I wanna put a wall of subs in my room, like car audio shops. Then one kid says, just hook your subs to a home audio amp instead of using power supplies. I dont think this will work because of impedence but he swears by it and says he is using a 10 inch , forgot which one, as his bass right now. Can you do this?

Yes, as long as the home audio amplifier is stable into the impedance the subwoofer will present. Most home audio amps are only stable down to 4ohms (though some are stable down to 2ohm, very few into 1ohm), so it sort of limits what subs can be used....but yes, it's entirely possible.

Only time a power supply needs to be used to when trying to power a car audio (12VDC) amplifier in your house.

Also he said you can tune a sub to 80 hz and it will sound good. I said that would sound like shit. I said you cant play 80 hz but tuning it would be extremely bad. What is the opinon on this? I admit I am not sure what tuning a sub to 80 hz would do and if you could explain it would be great. thanks agian guys.

80hz for a subwoofer tuning would be absolutely horrible. WAY WAY too high.....it wouldn't be able to safely play much lower than 60hz with any kind of output without the risk of damage.

 

[jgarcia9102 10+ year member]

i see squeak is responding here, but ill just say that unless you have a low pass filter or you will be running vocals through the subs. as far as the reciever being able to handle the lower impediance, idk, i suppose you could always run a DVC sub at 8ohm, or just make sure you some how get 8 ohms....

EDIT: ^ squeak got here first anyways.....

 

[davidwm88]

I have a question of my own about impedence. I know its "oppostion" to ac current but say you had a dual 4 ohm coil and a dual 2 ohm, does that mean the dual 4 can take more current? Also why do you have to match the home amp with the sub impedence? This is the only thing I am fuzzy with when it comes to car audio.

 

[davidwm88]

No, why did he humilate himself with impedence

 

[davidwm88]

Well, I dont know what I can say but he is wrong and should give it 2000 watts to get rid of the rattle. But still can you explain the impedence quesiton I had? Do you h ave msn or Aol instand messaging so we can talk instead of leaving messages?

 

[squeak9798 5,000+ posts]

Ok so say you hooked up a dual 4 ohm to an 8 ohm home audio amp, what would happen?

Wire the coils in series for a final 8ohm load and you could run that sub off of the amp just fine.

and what is the difference between a dual 4 and dual 2 subs?

Their impedances.

 

[davidwm88]

I understand that thank you. But what does a dual 4 have over a dual 2. The more resistence you have the less current can go through so wouldnt you want a low resistence sub to get the most power to it?

 

[davidwm88]

I see, thanks again for the help. This is one of the few forums where people dont flame you for asking questions that might seem stupid to some people.

 

[davidwm88]

Lol, well I just though of another question. When i tell him this tommorrow he is going to say it doesnt matter if the amps impedence is to high it still works. What do I say to that? Like what will technically happen to the sub. And what happens when you tune a sub to 80 hz, distortaion? thanks agian

 

[JimJ 5,000+ posts]

He'd be wrong by talking about the amp's impedance...very rarely are we concerned about the amp's output impedance. Generally, we're talking about the impedance of the load (speakers). If the load is high (like 16 ohms or so), the amp will not be able to output anywhere near its potential, but they'll be no harm done.

Tuning way too high sounds like ***, to put it bluntly. Technically speaking, you introduce a nasty peak in the frequency response, and the vast majority of the subbass spectrum gets attenuated by the enclosure's rolloff. The highest I'd tune for something that you'd listen to music with is 33Hz in a vehicle, and lower at home...

 

[squeak9798 5,000+ posts]

Lol, well I just though of another question. When i tell him this tommorrow he is going to say it doesnt matter if the amps impedence is to high it still works. What do I say to that?

If you are referring to the amp's lowest stable impedance.....well then, he would be wrong. If you try to play the amp well below it's stable impedance range you run a very high likelyhood of damaging the amplifier. If you, for example, ran a 1ohm load on an amplifier only stable down to 4ohm, you would be putting the amplifier under far more stress than it was designed to handle.

And this isn't limited to home audio amplifiers. Running any amplifier very far below it's lowest stable impedance will result in too much stress being placed on the amplifier causing it to either fail or go into protection.

Like what will technically happen to the sub. And what happens when you tune a sub to 80 hz, distortaion? thanks agian

It wouldn't really perform like a sub...more like a midbass due to it's very peaky response in the midbass region due to the enclosure, and very limited low frequency extension. It would generally sound like butt aswell.

 

[Raven 10+ year member]

I'm not sure if your friend is using the proper terms; I think he's talking about setting a low-pass filter to 80 Hz rather than tuning a ported enclosure to 80 Hz, which is what "tune a sub to 80 Hz" implies ...

X2. I read that and immediately thought "low pass filter" and not "ported box tuning". For a low pass filter, 80hz is fine. For box tuning, 80hz is absurd and wrong. Which he meant is something I'm not entirely sure of.

 

[regal8r 5,000+ posts]

I have a question of my own about impedence. I know its "oppostion" to ac current but say you had a dual 4 ohm coil and a dual 2 ohm, does that mean the dual 4 can take more current? Also why do you have to match the home amp with the sub impedence? This is the only thing I am fuzzy with when it comes to car audio.

impedance is opposition to ANY electrical current, whether it be ac or dc, and all the impedances of subs do is give u different wiring options, it doesnt affect power handling at all.

 

[squeak9798 5,000+ posts]

impedance is opposition to ANY electrical current, whether it be ac or dc,

That's not true. Impedance is the opposition to the flow of alternating current (AC). Resistance is the opposition to the flow of direct current (DC). Impedance fluxuates, resistance remains constant.

This is why speaker's have a Re (or DCR), which is the DC resistance of the speaker as measured with a simple DMM. Then they also have a Z (or Znom), which is the nominal impedance of the speaker with an AC input.