Using 4 ohm speakers instead of 8, car audio

[Opelmanz]

Dear Group,

I recently replaced the rear speakers of my car with 4 ohm speakers.
The old speakers were 8 ohms, and though older, sounded clearer than
the new ones. Am I trying to pump too much power to these new rear
6.5" speakers? The RMS rating of the speakers is only 30 w, and I know
that my lexus Es 250 has an amp, so maybe the speakers just don't have
a high enough RMS for my car. They sound crappy and are new so PLEASE
HELP!

 

[Jim Thompson]

Dear Group,

I recently replaced the rear speakers of my car with 4 ohm speakers.

WHAT possessed you to do that?

The old speakers were 8 ohms, and though older, sounded clearer than
the new ones. Am I trying to pump too much power to these new rear
6.5" speakers? The RMS rating of the speakers is only 30 w, and I know
that my lexus Es 250 has an amp, so maybe the speakers just don't have
a high enough RMS for my car. They sound crappy and are new so PLEASE
HELP!

Go back to 8 ohms and PRAY you didn't ruin your amplifiers.

...Jim Thompson

 

[Frank Bemelman]

Dear Group,

I recently replaced the rear speakers of my car with 4 ohm speakers.
The old speakers were 8 ohms, and though older, sounded clearer than
the new ones. Am I trying to pump too much power to these new rear
6.5" speakers? The RMS rating of the speakers is only 30 w, and I know
that my lexus Es 250 has an amp, so maybe the speakers just don't have
a high enough RMS for my car. They sound crappy and are new so PLEASE
HELP!

Easy, put the old ones back in. BTW, all 6.5" speakers sound like crap.

With 4 ohms speakers, theoretically you are able to put more power
into your speakers. At the same postition of your volume control,
you get more power now. This may cause that the loudness control
is much more active at normal soundlevels, giving your more bass
than desireable. There's also an increased risk that you damage your
radio, when played (very) loud.

 

[Paul Burridge]

Dear Group,

I recently replaced the rear speakers of my car with 4 ohm speakers.
The old speakers were 8 ohms, and though older, sounded clearer than
the new ones. Am I trying to pump too much power to these new rear
6.5" speakers? The RMS rating of the speakers is only 30 w, and I know
that my lexus Es 250 has an amp, so maybe the speakers just don't have
a high enough RMS for my car. They sound crappy and are new so PLEASE
HELP!

Maybe your new speakers *are* crappy and the impedance mis-match is a
red herring..

 

[Reg Edwards]

Maybe your new speakers *are* crappy and the impedance mis-match is a
red herring..

===================================

Yes, it's a red herring. There's an impedance mismatch whatever the
speaker impedance.

 

[Pooh Bear]

===================================

Yes, it's a red herring. There's an impedance mismatch whatever the
speaker impedance.

Oh, Good Lord. More assinine waffle.

Graham

 

[Pooh Bear]

Dear Group,

I recently replaced the rear speakers of my car with 4 ohm speakers.
The old speakers were 8 ohms, and though older, sounded clearer than
the new ones. Am I trying to pump too much power to these new rear
6.5" speakers? The RMS rating of the speakers is only 30 w, and I know
that my lexus Es 250 has an amp, so maybe the speakers just don't have
a high enough RMS for my car. They sound crappy and are new so PLEASE
HELP!

The speaker impedance is relatively unlikely to be an issue. If it was
you'd likely have found the amplifier had fried by now.

Most car audio uses 4 ohm speakers IME. If the speakers' rms rating wasn't
enough, they would have fried too.

It's obvious you're tinkering with stuff you don't understand so......take
some good advice from a car audio specialist and don't replace stuff
willy-nilly.

Graham

 

[Reg Edwards]

The most likely problem is that you bought cheap crappy speakers. Or
you are overloading them. Try turning down the volume a bit. If
things don't improve ask for your money back and buy 8-ohm speakers.

Anyway, 2 by 30 watts in a car can cause a gradual loss of hearing to
both you and the passengers.

 

[Mac]

Oh, Good Lord. More assinine waffle.

Graham

What are you talking about? You aren't suggesting that the source
impedance of the stereo system is 4 or 8 Ohms, are you? Most likely it is
nowhere near that high, so it would seem Reg is totally correct. In fact,
I have rarely seen him be anything but correct on issues such as impedance
mismatches and transmission lines and so-on.

--Mac

 

[Paul Burridge]

Oh, Good Lord. More assinine waffle.

Respect your elders! Reg is right, actually. But it's not normally an
audible factor in this type of problem.

 

[Pooh Bear]

What are you talking about? You aren't suggesting that the source
impedance of the stereo system is 4 or 8 Ohms, are you?

Absolutely not. More likely 100 milliohms max.

Most likely it is
nowhere near that high, so it would seem Reg is totally correct.

No - because 'matching' is not required or relevant. Any more than you 'match'
a heater fan to a car battery.

In fact,
I have rarely seen him be anything but correct on issues such as impedance
mismatches and transmission lines and so-on.

Audio speaker circuits are *not* matched circuits. Thay are voltage driven LF
circuits. If you stick a 4 ohm speaker on the end in place of 8 ohms then
twice the current flows for the same signal conditions.

Graham

 

[Pooh Bear]

Respect your elders! Reg is right, actually. But it's not normally an
audible factor in this type of problem.

Matching is a total irrelevance for speaker circuits.

Graham

 

[Mac]

Absolutely not. More likely 100 milliohms max.


No - because 'matching' is not required or relevant. Any more than you 'match'
a heater fan to a car battery.

Hmm. Reg never said matching was required or relevant. In fact, he has
gone on record many times in this newsgroup saying that impedance matching
is not a concept used by power amplifier designers.

In fact, I don't think you actually disagree with Reg at all. He said two
things:

1) The impedance mismatch issue is a red herring.
2) Whenever speakers are connected to an amp there is a mismatch.

If you do disagree, which statement do you disagree with?

Audio speaker circuits are *not* matched circuits. Thay are voltage driven LF
circuits. If you stick a 4 ohm speaker on the end in place of 8 ohms then
twice the current flows for the same signal conditions.

Yeah, yeah, yeah. I mean, some amps can't drive 4 ohm loads, but I get the
picture and I don't disagree.

Graham

--Mac

 

[Paul Burridge]

Matching is a total irrelevance for speaker circuits.

Did someone say it wasn't, then? I must have missed something!

 

[Bob Eldred]

Dear Group,

I recently replaced the rear speakers of my car with 4 ohm speakers.
The old speakers were 8 ohms, and though older, sounded clearer than
the new ones. Am I trying to pump too much power to these new rear
6.5" speakers? The RMS rating of the speakers is only 30 w, and I know
that my lexus Es 250 has an amp, so maybe the speakers just don't have
a high enough RMS for my car. They sound crappy and are new so PLEASE
HELP!

If the amplifier is decent, it won't make any difference what the speaker
impedance is over a large range. In fact ALL speakers have a rising
impedance curve as frequency increases. A poor amplifier may be taxed in
driving the larger current required for four ohms and that may be your
problem but I doubt it. Most likely your problem is crappy speakers not
impedance.

Clarity in speakers has to do with cone motion and cone breakup into various
modes of vibration at audio frequencies. Woofers or low frequency drivers
are notoriously poor at reproducing the mid range and high frequencies
necessary for clarity and fidelity. Be sure to use speakers designed for the
intended range of operation. Secondly speakers have design parameters like
cone resonance, fs, Vas, Qm, Qe, R and a few others. In a proper speaker
system, these parameters are accounted for and designed in just like with
any other technical device. To ignore these parameters and grab a cheap
replacement is to invite trouble and crappy sound. I guess that's what
you've got. The best bet is to use the intended replacement speaker unless
you want to do a custom design.
Bob