Ohms question

[BassmanPaul]

Originally Posted by ThisBass

That was meant to be a joke

Then, per forum rules, you should have added a smilie!

[ThisBass]

Originally Posted by B-string

Speaker are rated for nominal impedance, the point in the pass-band they present the maximum load on the "amp". This is the figure of concern and a simple resistance formula can apply. In reality speakers have inductive and capacitive reactance (to a much smaller degree) as well.

IF you limit the "speakers" to a frequency much higher than lowest part of the impedance curve then you will need to calculate that new impedance. From there you can use the same resistance formula to obtain the new load presented.

Depending on different frequency bandwidth spectrum the result for the impedance differs as well.
So if you want to know the current consumption (or impedance) of any cab (or speaker) you have to estimate the frequency spectrum at first.

I'm convinced that a bass signals' frequency spectrum differs very strong in relation to classical audio program.

[ThisBass]

Originally Posted by BassmanPaul

Then, per forum rules, you should have added a smilie!

missing a smilie, yeah I remember that was sometimes leading to misunderstandings/problems at bassic forum.

But thought the math was very very (-) stupid and therefor don't need anything else.

[B-string]

Originally Posted by ThisBass

Depending on different frequency bandwidth spectrum the result for the impedance differs as well.
So if you want to know the current consumption (or impedance) of any cab (or speaker) you have to estimate the frequency spectrum at first.

I'm convinced that a bass signals' frequency spectrum differs very strong in relation to classical audio program.

True and if you add a crossover with a HF driver you now have two peaks and valleys in the impedance curve for the system response.

[Munjibunga]

Originally Posted by bassmeknik

yep, 2.67 ohms (or 2 2/3 ohms if you prefer)

We can just say 2.7 ohms or 3 ohms. The impedance changes with frequency, and taking it out to two (or even one) decimal place implies that the impedance varies in the thousandths place when it actually varies as much as whole ohms.

[B-string]

I would agree to maybe 2.7 Too much difference in loading between 2.7 and 3.0 ohms.....yes really.

[Stick_Player]

Let's make it easy!

[JHAz]

Originally Posted by B-string

I would agree to maybe 2.7 Too much difference in loading between 2.7 and 3.0 ohms.....yes really.

IDK. While paying attention to impedance capabilities of amps is important, just looking at a couple of Emi drivers (raw) I see the nominally 8 ohm 12 inch Basslight has max impedance of about 80 ohms at just under 50 Hz, dropping to about 7.5 ohms at 20 Hz and down to maybe 5.5 ohms at 200 hz then smoothly rising all the way to 50 ohms at 20 KHz. All over the map and out of its minimum pretty fast. Similarly the 4 ohm BP102 10 incher maxes at 80 ohms at about 40 Hz, down to 7.5 or so at 20 Hz, and down to 3ish between maybe 120 and 220, then rising to a plateau at say 35 ohms by 10 KHz. Depending on what the cab does to the impedance, plus how much of my playing centers in the low impedance range, a nominal half ohm or something can't really be that big a deal, can it? Unless the driver hangs around the low end of its impedance for much of its frequency range.

[ThisBass]

Originally Posted by B-string

True and if you add a crossover with a HF driver you now have two peaks and valleys in the impedance curve for the system response.

HF driver crossovers are working at appro 2..4 kHz.
The Power at 2..4 kHz and above is very weak so the "impedance" above 2 kHz is negligible/obsolete.

[ThisBass]

Originally Posted by JHAz

IDK. While paying attention to impedance capabilities of amps is important, just looking at a couple of Emi drivers (raw) I see the nominally 8 ohm 12 inch Basslight has max impedance of about 80 ohms at just under 50 Hz, dropping to about 7.5 ohms at 20 Hz and down to maybe 5.5 ohms at 200 hz then smoothly rising all the way to 50 ohms at 20 KHz. All over the map and out of its minimum pretty fast. Similarly the 4 ohm BP102 10 incher maxes at 80 ohms at about 40 Hz, down to 7.5 or so at 20 Hz, and down to 3ish between maybe 120 and 220, then rising to a plateau at say 35 ohms by 10 KHz. Depending on what the cab does to the impedance, plus how much of my playing centers in the low impedance range, a nominal half ohm or something can't really be that big a deal, can it? Unless the driver hangs around the low end of its impedance for much of its frequency range.

There are a lot of speakers out there with same nominal but different impedance curves.

Sometimes you'll get nearly the same impedance with
3 x 8Ohm (speaker type A)
and
2 x 8Ohm (speaker type B)

[bassmeknik]

Originally Posted by Munjibunga

We can just say 2.7 ohms or 3 ohms. The impedance changes with frequency, and taking it out to two (or even one) decimal place implies that the impedance varies in the thousandths place when it actually varies as much as whole ohms.

yep

[B-string]

Originally Posted by JHAz

IDK. While paying attention to impedance capabilities of amps is important, just looking at a couple of Emi drivers (raw) I see the nominally 8 ohm 12 inch Basslight has max impedance of about 80 ohms at just under 50 Hz, dropping to about 7.5 ohms at 20 Hz and down to maybe 5.5 ohms at 200 hz then smoothly rising all the way to 50 ohms at 20 KHz. All over the map and out of its minimum pretty fast. Similarly the 4 ohm BP102 10 incher maxes at 80 ohms at about 40 Hz, down to 7.5 or so at 20 Hz, and down to 3ish between maybe 120 and 220, then rising to a plateau at say 35 ohms by 10 KHz. Depending on what the cab does to the impedance, plus how much of my playing centers in the low impedance range, a nominal half ohm or something can't really be that big a deal, can it? Unless the driver hangs around the low end of its impedance for much of its frequency range.

It is all splitting hairs, basses do not produce single frequencies at any time. You can tell your amp that you were only playing an open A as an example, it will not make the smoke go back in.

[ThisBass]

Originally Posted by JHAz

IDK. While paying attention to impedance capabilities of amps is important, just looking at a couple of Emi drivers (raw) I see the nominally 8 ohm 12 inch Basslight has max impedance of about 80 ohms at just under 50 Hz, dropping to about 7.5 ohms at 20 Hz and down to maybe 5.5 ohms at 200 hz then smoothly rising all the way to 50 ohms at 20 KHz. All over the map and out of its minimum pretty fast. Similarly the 4 ohm BP102 10 incher maxes at 80 ohms at about 40 Hz, down to 7.5 or so at 20 Hz, and down to 3ish between maybe 120 and 220, then rising to a plateau at say 35 ohms by 10 KHz. Depending on what the cab does to the impedance, plus how much of my playing centers in the low impedance range, a nominal half ohm or something can't really be that big a deal, can it? Unless the driver hangs around the low end of its impedance for much of its frequency range.

Originally Posted by B-string

It is all splitting hairs, basses do not produce single frequencies at any time. You can tell your amp that you were only playing an open A as an example, it will not make the smoke go back in.

As an HF Technician I'm most of the time thinking in frequency bandwidth relations, but do less in time related signals like most of folks do it (the ordinary school physics).

Understanding Audio is most of the time frequency bandwidth related but it's most of the time not a valid term to do particular interpretation in time axis signals.
Equally it is not a valid point to do relations to a explicit frequency like 440 Hz (...ähm most of the time it it so)

But sometimes you have to combine all together (frequency and time related) to combine to one truth.

[bigtexashonk]

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