Speaker Impedance

[Chris]

Is it possible to drive a 6 ohm speaker with an amp that only outputs
2, 4 and 8 ohms? Will this damage the speaker or the amp?

Thanks,

Chris

[B. Earp]

> Is it possible to drive a 6 ohm speaker with an amp that only outputs
> 2, 4 and 8 ohms?

yes (technically, what you're saying is that the amp can drive a minimum of
2 ohms).

[Richard]

"B. Earp" > wrote in message
...
> > Is it possible to drive a 6 ohm speaker with an amp that only outputs
> > 2, 4 and 8 ohms?
>
> yes (technically, what you're saying is that the amp can drive a minimum
of
> 2 ohms).
>
Do note however that some Tube/output transformer based amps can have
specific output taps to match the anticipated impedance load. All the taps
can drive any speaker but the dampening factor and other factors may not be
maximized. In the case of a solid state amp it is usually a UL heat test
rating that determines how low the output impedance can be rated.

Richard.

[B. Earp]

Richard > wrote in message
...
>
> "B. Earp" > wrote in message
> ...
> > > Is it possible to drive a 6 ohm speaker with an amp that only outputs
> > > 2, 4 and 8 ohms?
> >
> > yes (technically, what you're saying is that the amp can drive a minimum
> of
> > 2 ohms).
> >
> Do note however that some Tube/output transformer based amps

uhh...no one, including you in your original response said anything about
output transformers or tubes...we're talking HT here

> can have
> specific output taps to match the anticipated impedance load.

you're talking about 99% of tube amps and AFAIK one solid state car
amp...and since you bring tube amps into the picture, a 6 ohm speaker can
still be driven off 4 or 8 ohm taps with very little problem, in fact
connecting a 4 ohm speaker to 8 ohm tap doesn't pose much of a problem
either

> All the taps
> can drive any speaker but the dampening factor and other factors may not
be
> maximized.

power output can be slightly reduced, power consumption can be slightly up,
bandwidth and/or frequency response may vary a little (depends on speaker
and amp)...but the answer to the original poster's question is still 'yes'
with a capital Y.

> In the case of a solid state amp it is usually a UL heat test
> rating that determines how low the output impedance can be rated.

the output impedance of an amp is easily calculated, and I know you really
meant to say minimum load capability, however, you're still confusing the
topic...we were talking 6 as in between 4 and 8, not the minimum, and
finding the minimum is simple...does the amp crap out when driving a 2 or 4
ohm resistive load? (meaning hardly puts out any power while using lots of
it)...say a 200@8 amp only puts out 100@4, and blows a fuse into 2 ohms,
guess what its rating is

[B. Earp]

Richard > wrote in message
...
> "I know you really meant to say minimum load capability, however, you're
> still confusing the topic.."
>
> Not really.

so if you haven't really changed the subject to minimum impedance, are you
thereby still saying that an amp that can drive 2/4/8 ohms cannot drive 6
ohms, like in your original answer?

> In the States the max power output of an amp is extablished by
> FTC approved methodology.

silly me, you were thinking about a third subject - maximum output power

> In order to spec an amp it must go through UL
> certification. The vender must pay for each certification test. The
> certification is based upon the ability of the amp to provided a specified
> output into a given impedance load.

gee, that sounds real official, but what difference does it make to what an
amp is capable of delivering?

> If the vender does not pay to have it
> tested at 4 ohms it cannot be promoted at that impedance (even if it would
> pass the "heat load" test).

Let's say the vendor pays to have an amp tested at 2 ohms and 8 ohms, and
the amp performs nicely, but tragedy strikes and the vendor can't afford to
have it tested at 4 ohms:

a) would the amp be capable of driving anywhere from 2-8 ohms, or
b) would the amp be capable driving only 2 and 8 ohms?

> Most speakers present a complex impedance load
> depending upon frequency and most present a lower impedance load at
critical
> lower frequencies than the published figure (this number is not regulated
by
> the FTC or any other regualtory body that I know of).

alrighty then, how many 6 ohm nominally rated speakers have you seen dip
below 2 ohms, and with the kind of width that would cause a 2 ohm capable
amp to freak out?

> But in general, I
> agree with your assertion that it is typically OK to ignor this issue,

1. I didn't say anything about ignoring something
2. after a whole bunch of BS, you turn around and say that an amp that can
drive 2/4/8 ohms CAN drive 6 ohms...agree with assertion blah blah
blah...this isn't about opinion, you know

> especially if one is using efficient vented speakers

what does a speaker's enclosure or efficiency have to do with either an
amp's minimum impedance driving capability or its maximum output power?

> and very high levels for extended periods are not experienced.

ok so plug it into a timer just to be safe

> If your amp starts to smell or you
> blow fuses or clipping causes the drivers to bit the dust you just might
> have a problem.

thanks, I didn't realize that...by the way, you forgot above to mention
ambient heat

> With today's high output amps this is not seen too often.

and the cause of that is...

> Richard.

keep it real, Richard

[Richard]

"B. Earp" > wrote in message ........"

Gee B.Earp, you seem to be itching for a fight. That is not my intention.
Let me keep this simple. In an audio situation impedance is only of
significance when it relates to the max power delivery of an amp at its max
rated power. A given amp, with a fixed load sees a given impedance at a
given frequency. Typically the lowest impedance seen is at the lower audio
frequencies. If an amp is to used at a specific load it must deliver its
rated power without overheating. This is what the UL certification is all
about. The value used to describe that power output is based in the States
on FTC criteria. If an amp is rated for 8 ohms it can be marketed as such.
If it also wants to be marketed as suitable for lower impedance loads it
needs to be tested again pursuant to FTC and UL criteria. Obviously an amp
rated for 8 and 2 ohms can be used in a typical ohm situation also, it is
just not permitted to publish the output specs at 4 ohms if the
certification has not been performed. I myself have never seen this.

Richard.

[Chip Orange]

Since he asked 2 questions, and you only gave one answer, it's a little hard
to figure out what you meant.

"Richard" > wrote in message
...
>
> "Chris" > wrote in message
> om...
> > Is it possible to drive a 6 ohm speaker with an amp that only outputs
> > 2, 4 and 8 ohms? Will this damage the speaker or the amp?
> >
> > Thanks,
> >
> > Chris
>
> No.
>
> Richard.
>
>

[Richard]

"Chip Orange" > wrote in message
...
> Since he asked 2 questions, and you only gave one answer, it's a little
hard
> to figure out what you meant.
>
> "Richard" > wrote in message
> ...
> >
> > "Chris" > wrote in message
> > om...
> > > Is it possible to drive a 6 ohm speaker with an amp that only outputs
> > > 2, 4 and 8 ohms? Will this damage the speaker or the amp?
> > >
> > > Thanks,
> > >
> > > Chris
> >
> > No.
> >
> > Richard.
> >
1. Yes because an amp does not output impedance, and it does not output its
power into any one impedance. The lower the impedance of the load the higher
the power delivered by the amp, but this is limited by the ability of the
amp to dissipate heat and limitations in the design of the power supply. If
an amp is rated to deliver its rated output into 2 ohms it can safely drive
a 6 ohm load even if a maximum output level is not published for that load.

2. Since an amp rated for 2 ohms can safely drive a nominal 6 ohm load it
cannot damage the speaker or the amp unless you exceed the heat and physical
limitations of the speaker (this has nothing to do with its impedance) or
you exceed the thermal limits of the amp.

Richard.