Home Audio Setup

[Hessakia]

I figured someone here would know the answer to my question, but its not too terribly "highly technical."

I was thinking of some way to add bass to my home stereo system, and came up with a plan... take the sub output on my reciever and run it into another receiver. Since the 2nd receiver (most likly just an old stereo reciever) only gets the subwoofer frequencies (bass), i coudl run a pair of car audio subs (which create massive bass). I was wondering, using a stereo 100x2 reciever@8ohms (like almost all home audio is), and a pair of 4 ohm subwoofers, which would bridge the amp and push ~200x2 into the subs (or get 8ohm speakers and just have 100x2), how would this sound?

I realize that most car audio applications use massive amplifiers to push 500-1000 watts intoa single sub for bass, but i think it might be liek comparing apples to orangles when we're talking about home audio and wattage in a home stereo reciever and a car amplifier.

What do ya'll think?
Hess.

 

[Antisocial Virge]

Sounds ghetto

I don't think adding a 4ohm load on a 8ohm signal is called bridging. Bridging is when you combine both channels of a amp into a single output.

EDIT: Why don't you just pay $150 and get a real powered sub?

 

[Muadib]

Antisocial is right, furthermore, if the amp you are going to use cant handle a 4 ohm load, you can kiss it goodbye.

 

[spidey07]

That and car audio subs can't reproduce the deep bass needed for home theater. They're just not designed for it.

Sure it would work, but very very poorly.

 

[rimshaker]

Home receivers aren't very flexible when it comes to their output loads. When they say 8ohms, it really means 8ohms! On the other hand, car amps are more flexible in that some can handle 4ohm, 2ohm, even 1ohm loads. But flexibility doens't mean better quality in this case. Remember, car amps are designed running off a 12-14V source while the inflexible home receivers are plugged into 110-120V. Clearly the best power quality is found in home receivers. Uhhh, bottom line.. sorry... don't crossmatch components between home and car audio.

 

[jurzdevil]

my brother had his 2 jl audio 12w0s in his room when his car was in the shop for a month getting fixed. i forget the amp he had since they are all long gone but it was only 250watts rms and we ran it off of a 12volt car battery charger in his room. there was way to much air for the subs to sound cleaned. all they did was shake stuff off the wall. his two sony 10inch woofers in a tower sounded better. car subs are designed for a small volume of air in which they operate.


asking a different ohm from an amp does some scary things too. my cousins 800watt rockford fosgate amp was intended for 4 ohm abut he wired ti to 1 ohm and nearly burned down his saturn when the 4 gauge wire melted around the battery.

id stick with the previous suggestion of getting a powered home audio sub.

 

[Hessakia]

putting a 4 ohm on an 8 ohm amp (that is the the way it works in car audio), will pull more power from the amp source. I do have a nice powered sub (Acoustic Research PS120), but i was just curioius how it would work in an extremely loud situation (powered sub doens't do too good at higher volumes, such as parties).

Btw, when stuff gets rattled off the walls--that is bass (car audio subs rattle stuff--you can feel them, where home audio subs you can hear the bass), and that is actually what i'm looking for.

i'm thinkign of putting 1 JL 15W0 on a separate (older) amp that i have an trying it--the speaker itself is 8ohms, so its all good.


anything else?
hess.

 

[jurzdevil]

i guess you will get the best of both worlds. i say give it a try and see how you like it.never hurts to experiment!

 

[blahblah99]

Originally posted by: Hessakia
putting a 4 ohm on an 8 ohm amp (that is the the way it works in car audio), will pull more power from the amp source. I do have a nice powered sub (Acoustic Research PS120), but i was just curioius how it would work in an extremely loud situation (powered sub doens't do too good at higher volumes, such as parties).

Btw, when stuff gets rattled off the walls--that is bass (car audio subs rattle stuff--you can feel them, where home audio subs you can hear the bass), and that is actually what i'm looking for.

i'm thinkign of putting 1 JL 15W0 on a separate (older) amp that i have an trying it--the speaker itself is 8ohms, so its all good.


anything else?
hess.

If your going to do that, you will either

1) overheat the output transistors in the receiver and blow up the amp

or

2) thermal the amp into protection due to more current draw than the device was designed for


Look in your receiver manual... if they don't specify a 4ohm rating, then DO NOT run it at 4 ohms.

 

[SuperPickle]

People have covered possibly overloading that amp and while that's true, your specific amp may be able to take it and if you don't care about losing said amp, go for it--put a fan on it if it gts hot. As for comparing wattages of car to home audio, there really isn't much difference. Those big-ass high-current bass amps need to be big to handle the large speaker and/or long throw of the speaker in turn pushing lots and lots of air. A bigger problem I see with what you are suggesting is the timing of the frequencies being slightly out of phase with each other due to actuation timing of the amps and their respective speakers. This isn't going to be very noticable with the long wavelengths of low frequencies, but it may be there. Biggest problem overall is having low frequencies eminating from multiple sources is the creation of standing waves and the interaction between them. You may end up with strange pockets in the room where the bass is really loud in one area and some pockets where you think "who turned it down?"

There is something to be said about having only one (very large) source for bass. Conversely, louder at parties is damn cool too and saving some bucks to achieve that goal is always a plus.

 

[blahblah99]

Tossing a big fan to blow out the hot air is going to help, but theres a limit.

The amplifier was designed with output devices selected to operate UP TO CERTAIN AMOUNT OF CURRENT before any good sized heatsink/fan combination can keep it cool enough from failing.

Now, if you understood that, then also know that the amp designer CHOOSE those specific transistors because it matched the current and voltage requirements (along with other factors). Whether or not they rate the amplifier at the borderline of the operable region of the output transistors is only known to the designers, unless you hack into the amp and do your own research.

So when an amplifier is rated at 100WrmsxChannel, you do not know if operating at 100W continously is really pushing the limit of the transistors, or that rating is convervative. Now with the receiver being a "home theatre receiver", most likely it is rated on the borderline near the operational limit of the output devices since many unwary consumers only really care about what the wattage figures are.

Now lets say, for example, if you are pushing 100W into 8 ohms. Using P=V*V / R, you are outputting 28.28V to the speaker. Suppose you connect a 4ohm load on there (either by removing the 8 ohm and placing the 4 ohm in, or by paralleling two 8ohms). Your output voltage is still ~28.28V, but you have theoretically double the current the transistors need to push. Will the transistors be able to handle it? Maybe, with enough thermal cooling. Is it good for the amplifier? Nope.

I'm not saying your receiver won't be able to handle the 4ohm loads. It may or may not. Like I said, if your manual specifies a 4ohm rating, then by all means go ahead and use it with a big fan. If it doesn't specify a 4ohm rating, then don't do it.


Also, the phase shift your talking about is most likely coming from the passive crossover networks you are using, or if you have the speaker wire connected in reverse. It is not a problem in the amplifier itself since any decent amp will not introduce a phase difference between the input and output.