Speakers question

[dimme]

I have one set of speakers, don't know their effect but they sure roar, that's for sure. It's a 3-way system containing one tweeter, one midrange speaker and one 12" bass speaker that goes down to 30Hz. Now since these speakers are old I have thought about upgrading the bass speakers.
I have had my eyes on a 12" speaker with a 7.5 lbs magnet 500W peak and 200W RMS power with 4ohm impedance. It's actually for a car but it can be mounted in home speakers, too right?

Now I don't know what impedance my current bass speakers have, if they are 8ohms, what difference will the 4ohm speaker make? I'm not looking for any hot shot high end bass speaker like cerwin vega or infinity kappa, just a good bass speaker element for some money (stress the some, I'm a student dammit).

Remember I'm a n00b in this. Give me as MUCH info as you can about it
I don't want to end up with a ruined speakers in my hands

EDIT, the speaker box is pretty big, measured it and it's a 94 litre (3.36 cubic feet I think, NOT SURE) box, yes it's big.

Thanks

 

[Luis G]

Welcome to OTC dimme, you might wanna check the perpetual welcome thread

 

[Luis G]

About the impedance question, it is better to match the impedance of all components, otherwise you might be stressing them, or you might be stressing the amp.

Since you're talking about OLD speakers, i'm pretty sure they have a cross-over, does it allows the change of impedance?

 

[dimme]

Originally posted by Luis G
About the impedance question, it is better to match the impedance of all components, otherwise you might be stressing them, or you might be stressing the amp.

Since you're talking about OLD speakers, i'm pretty sure they have a cross-over, does it allows the change of impedance?

I don't know if they have a crossover or not, never opened them. But if they are 8ohm speakers, I have to get 8ohm speakers to replace them? Doesn't a higher impedance put a higher load on the amp?

 

[outside looking in]

Generally speaking, a lower impedence puts a higher/more difficult load on an amplifier. Many amplifiers double their output power when you halve the impedence, and typically double their noise as well. Some amps put out ~50% more power, and many others just blow up.

If you don't know the rated impedence capability of your amps, along with the specific impedences of all three speakers, and any crossovers, as well as the way in which they are wired (parallel, series, mixed), then you do run a risk of burning up your amp if you replace an 8ohm speaker with 4ohm speakers.

Electrical considerations aside, yes, a 12" car speaker can be mounted in a home enclosure. There's nothing magical about the speakers that make them "car" or "home." However, every speaker (type/brand/size) has certain characteristics that define how that speaker behaves. Some have to do with the cone stiffness, or the suspension stiffness (which in part define the natural and damped resonant frequencies), or the rigidity of control the voice coil has. These characteristics are used to generate an "ideal" enclosure size and type for that particular speaker (this is more relevant for subwoofers than for midrange or tweeters).

The bottom line is that the chances of your home stereo enclosure happening to be well matched to a randomly picked car audio speaker are slim. Even if the car speaker is superior in every way, the end result could be worse sound if it happened to be particularly poorly matched to the enclosure.

The process of getting all the relevant numbers on a candidate speaker, doing some calculations, and comparing the result to the existing enclosure would be somewhat of a nuisance. Essentially, it's going to be a trial and error process (assuming electrically everything works out fine) regarding sound quality. Adding or subtracting filler could help tune the enclosure, or adding "bricks" to reduce volume (can't do much to increase it), or mucking about with the port length if it's ported.

Now, having said all that, I can tell you that when I was younger I did just such a swap, and it sounded much better than the cheap speakers that came in the enclosures, and I didn't have a clue what I was doing.

 

[Justintime]

Yeah as Oli said, halving the impendance will put a greater strain on the Amp, you could put 2 4 ohm speakers in series to make 8ohm and match the impedance of the amp, in parallel 2 4 ohm speakers would be 2ohms together and thats a real high demand on the output stage and may toast things if pumped too hard.
About the type of speakers, the car speakers may be 'designed' with the enclosure of a car in mind, and may not perform up to standard in a house, so best to play safe and get properly matched speakers to replace what you have.

 

[Justintime]

Heres a little trick i learned as a teen get 2 of those pvc pipes they use to mold pillars at work site and fill it with bedding material, close the back nd front up with wood, cut a speaker hole and insert the speaker in fron, lay it down with the speaker pointingto a wall, and stick a layer of sponge on the wall in front of it, i did this and got HUGE bass with 2 Kenwood 15" subwoofers and a 500W Pioneer amplifier, literaly shook EVERY window in the house and gave people headaches lol.

 

[Luis G]

Originally posted by Justintime
Heres a little trick i learned as a teen

Grandpa

 

[dimme]

Ok, thanks for the info.
I've seen different woofers but they all weigh differently, does the weight of the magnet have an effect on the sound of the woofer? have seen speakers with 116oz magnet that costs $40 and I have seen speakers with a 70oz magnet that costs $100. All 12" woofers.

I have only found ONE 8ohm speaker in my price range. What do you think of it?

Impedance: 8ohms
Sensitivity: 92db
240W max 120W RMS
30oz magnet
Vas 138 liter. Fs 27Hz. Qts 1,16. BL 9,2.

 

[outside looking in]

That Qts value looks rather odd. Are you sure that 1.16 is correct?

If so, the smallest you really want the enclosure to be is about 400 liters, for a sealed box.

With that Qts value, some strange things happen though when trying to get a more correctly tuned enclosure.

 

[dimme]

What does the QTS value do? The 4ohm version of the same speaker has a QTS of 0.82.
I'm using a 94 litre bassreflex box (ported) with a 4.33 inch bassreflex port.

 

[dimme]

BTW, opened the speakers today. The current woofer in there is a 12" "GAMMA HIFI BK 3013 A" 8ohm speaker. I couldn't find any specs on this one on the net so far. Do any of you have any idea?
Saw a GREAT 4ohm woofer today for $40 but it's 4ohms