WHAT'S THE IMPEDANCE OF MY BASS CAB?

[fernandobicho2]

I think you're right!

So, if the drivers measure it's 4.4 (5.72) falling into 6 ohm category,

this cab can't be a 4 ohm cab.

Right?


(people say the multimeter measures always above and not below, so a 4 ohm cab could show 3 ohm in the multimeter, or so)

[Downunderwonder]

The way you describe your cab's wiring sounds all wrong. It should have a parallel pair of series sets OR a series of parallel pairs, either way gives the same individual DCR for the cab and equal distribution of power.

[ThisBass]

Originally Posted by Arjank

What I meant to say is that a driver with an Re of 4.4 ohms would fall in the 6ohm category. And 3.1ohm e.g. would fall in the 4ohm category. And 5.9 e.g. would fall in the 80hm category.

And yes, an amp could die when the impedance drops below 3ohms in a broad frequency range and the amp is only 4ohm stable......

I never did a measurement to the Deltalite but,
as a midrange purpose the Deltalite impedance should be 6..6,5 Ohm.

A broad frequency range of the impedance curve must always be considered in correlation to a given spectrum.
For general purpose the spectrum of pink noise is a good bet.
Or even not a good bet cause the meaning of "general purpose" means "in general".

But most of the time a real bass signal is different to pink noise.

[dincz]

Originally Posted by ThisBass

But most of the time a real bass signal is different to pink noise.

I really hope you're right

[ThisBass]

Originally Posted by fernandobicho2

I think you're right!

So, if the drivers measure it's 4.4 (5.72) falling into 6 ohm category,

this cab can't be a 4 ohm cab.

Right?


(people say the multimeter measures always above and not below, so a 4 ohm cab could show 3 ohm in the multimeter, or so)

No, it isn't right.

The Deltalite spec. is 5 Ohm DC.

That is 5*1.3 = 6.5 Ohm.
The Deltalite is in the 8 Ohm category, right?

The SWR is in the 6 Ohm category, right?

A 4 Ohm amp burns off with the SWR cause the impedance is 6 Ohm, right?

But a 4 Ohm amp would not burn off with the Deltalite because the impedance is in the 8 Ohm category?

...right ???

Originally Posted by fernandobicho2

(people say the multimeter measures always above and not below, so a 4 ohm cab could show 3 ohm in the multimeter, or so)

I have no idea just this moment. I have to keep a look to the calibration sheet first but, if your multimeter is of high accuracy you don't have to worry about peanuts.

[FrenchBassQC]

It says right on the grill what is the cab ohm this is at least what I can see here:

http://www.musiciansfriend.com/ampli...peaker-cabinet

They have both cab showed here anyway.

[ThisBass]

Originally Posted by FrenchBassQC

It says right on the grill what is the cab ohm this is at least what I can see here:

http://www.musiciansfriend.com/ampli...peaker-cabinet

They have both cab showed here anyway.

but where is the 6 Ohm cab ?

or:

where is the 4.4 Ohm DC cab ?

[ThisBass]

Originally Posted by dincz

I really hope you're right

I'm really sure.

I did some measurements in the past cause we wanted to know the impedance.
We wanted to know the impedance measured with pink noise according to different bands and also the full range band.

And we also wanted to know the impedance with real bass signals depending on different eq settings.

The results are "horrible"
Everything is possible. It all depends on your fashion what you do with the cab.

at OP:
BTW I would not bother about a 4.4 Ohm DC reading.
Maybe the driver is a bit below what we suggest as a 8 Ohm driver but, I would not doubt it is a "nominal" 8 Ohm for bass guitar purpose.
I don't know the Zmax of the cab. But I'm sure that the cab's impedance curve in correlation to the frequency spectrum of the bass guitar will give you the desired "8 Ohm feeling".

[Arjank]

Originally Posted by ThisBass

I'm really sure.

I did some measurements in the past cause we wanted to know the impedance.
We wanted to know the impedance measured with pink noise according to different bands and also the full range band.

You can't do it that way. You need a signal(sinewave)generator and some other stuff, depends on how you want to set it up. I use a softwareprogram (Hobbybox), my Focusrite soundcard, an amplifier(hifi) and a resistor to measure the frequency depended impedance of a loudspeaker. This system then measures the impedance at several points from e.g 20 - 500hz or whatever range you like.

[Arjank]

Originally Posted by ThisBass

I never did a measurement to the Deltalite but, as a midrange purpose the Deltalite impedance should be 6..6,5 Ohm.

I took a look at the Eminence specs and the impedance curve is slightly beneath 6ohms between 200 and 400hz. Above 400hz the impedance gradually rises.
If you use the Deltalite 2510 as a mid it will surely be no problem because when you add a simple passive highpass filter e.g. 47uf in series with this driver the impedance will increase below 400hz.

[ThisBass]

Originally Posted by Arjank

You can't do it that way. You need a signal(sinewave)generator and some other stuff, depends on how you want to set it up. I use a softwareprogram (Hobbybox), my Focusrite soundcard, an amplifier(hifi) and a resistor to measure the frequency depended impedance of a loudspeaker. This system then measures the impedance at several points from e.g 20 - 500hz or whatever range you like.

Singular Sine Waves will give you the wrong answer to the "impedance" question.
What you know is a impedance according to a singular point but,
what we want to know is the impedance according to a whole spectrum what is IMO a total different story.

There is only one exception to the rule:
Karlheinz Stockhausen composition/arrangement for sinus generators.

But be sure I'd never give my 70's svt for backline.

Try to imagine a sine wave at 81Hz, and the cab's impedance at 81Hz is above 30 Ohm connected to the valve amp output with 330 Watt full power.

Try to imagine the 2nd Harmonic of low E is appro 81Hz. Try to imagine most of power of any bass guitar is hold by the 2nd Harmonic, which is 81Hz for note E.
Try to imagine why a valve amp probably dies with sine wave 81Hz at full power at any vented cab.
Try to imagine why a valve amp does not die with note E even with most of power at the 2nd Harmonic 81Hz.

[ThisBass]

Originally Posted by Arjank

I took a look at the Eminence specs and the impedance curve is slightly beneath 6ohms between 200 and 400hz. Above 400hz the impedance gradually rises.
If you use the Deltalite 2510 as a mid it will surely be no problem because when you add a simple passive highpass filter e.g. 47uf in series with this driver the impedance will increase below 400hz.

In a general Audio purpose Energy/Power decreases vers. increasing frequency.

So you are right with the specs cause the impedance between 200..400Hz is slightly beneath 6 Ohm but, for a midrange Audio Signal pupose there is most of the energy/power in there.

[Arjank]

Originally Posted by ThisBass

Singular Sine Waves will give you the wrong answer to the "impedance" question.
What you know is a impedance according to a singular point but,
what we want to know is the impedance according to a whole spectrum what is IMO a total different story.

No it's not, it's the thing that I told. You indeed measure single points, but connect all the "dots" and you have the impedance curve from the whole spectrum......
All the impedance curves you see from manufacturers (the ones with the peak at the resonance frequency) are the thing that the AMP sees when the speaker is connected to it. These curves are all measured at single (frequency) points.

[ThisBass]

Originally Posted by Arjank

No it's not, it's the thing that I told. You indeed measure single points, but connect all the "dots" and you have the impedance curve from the whole spectrum......

What do you mean by that?

measuring singular dots with same voltage?

or

measuring single dots with decreasing Voltage(Amplitude)/Octave and then calculating RMS Current:

Irms = SQRT(I(f1)^2 + I(f2)^2 + I(f3)^2 ...)

Vrms = SQRT(U(f1)^2 + U(f2)^2 + U(f3)^2 ...)

and Impedance:

Z=Vrms/Irms

How do you decrease Voltage(Harmonic Amplitude) / Octave ?

[Arjank]

Originally Posted by ThisBass

What do you mean?

measuring singular dots with same voltage?

ThisBass, you're from Germany right?
The software I use is Hobbybox(from Germany).
Here is a link to the manual, in there you can read about impedance measurements and other very important measurements that you can do with it.
It's in german language.
http://www.audio-software.de/HobbyBox51.pdf

[ThisBass]

Originally Posted by Arjank

ThisBass, you're from Germany right?
The software I use is Hobbybox(from Germany).
Here is a link to the manual, in there you can read about impedance measurements and other very important measurements that you can do with it.
It's in german language.
http://www.audio-software.de/HobbyBox51.pdf

yeah Germany that's right.

Nice tool

This tool provides a very lot of nice features but, there is nothing on board to measure impedance for a given "real live" signal.
That don't makes me wonder ...

[Arjank]

Originally Posted by ThisBass

yeah Germany that's right.

Nice tool

This tool provides a very lot of nice features but, there is nothing on board to measure impedance for a given "real live" signal.
That don't makes me wonder ...

The impedance curve of a loudspeaker doesn't change when you feed it a " real live" audio signal. There are other factors that may alter the impedance, e.g. loads of amplifier power lead to powercompression, voicecoil heats up etc...But these will increase the impedance, they will not lower it. The cabinet itself alters the impedance curve of the loudspeaker and so do passive crossover components....

[ThisBass]

Originally Posted by Arjank

The impedance curve of a loudspeaker doesn't change when you feed it a " real live" audio signal. There are other factors that may alter the impedance, e.g. loads of amplifier power lead to powercompression, voicecoil heats up etc...But these will increase the impedance, they will not lower it. The cabinet itself alters the impedance curve of the loudspeaker and so do passive crossover components....

Your argumentation reminds me on a forum discussion I had two years ago.

Yes you are right the impedance curve does not change.
I don't consider compression losses or something else.

I consider the impedance curve and a given spectrum.

Sometimes a spectrum has most amount of energy/power at the lows. (The bass guitar for example)
Whereas sometimes a spectrum has more amount of power at low mids.
Depending on signal nature and eq settings the individual users spectrum differ significant

Depending on impedance curve the amplifier sees different impedance values depending on the signal spectrum.
The Impedance curve by itself does not change.


BTW mine argumentation is poorly discussed even by AES/EIA societies but, it's a well known problematic.

By the other hand the AES/EIA recommendation reading is:
"the impedance curve of driver shall be stated."

so it's up to you what to do with the "nominal 8 ohm" driver.

[Bassmec]

Originally Posted by Arjank

The impedance curve of a loudspeaker doesn't change when you feed it a " real live" audio signal. There are other factors that may alter the impedance, e.g. loads of amplifier power lead to powercompression, voicecoil heats up etc...But these will increase the impedance, they will not lower it. The cabinet itself alters the impedance curve of the loudspeaker and so do passive crossover components....

I can measure it accurately, I have the all tube old school former Celestion lab technology to do so right here:

but you are over there somewhere, so I will have to factor in a very long lead length which will introduce unacceptable errors.
So why not just take an ancient loudspeaker test engineers word for it EH! 8 Ohms nominal son!.

[megafiddle]

Originally Posted by ThisBass

Your argumentation reminds me on a forum discussion I had two years ago.

Yes you are right the impedance curve does not change.
I don't consider compression losses or something else.

I consider the impedance curve and a given spectrum.

Sometimes a spectrum has most amount of energy/power at the lows. (The bass guitar for example)
Whereas sometimes a spectrum has more amount of power at low mids.
Depending on signal nature and eq settings the individual users spectrum differ significant

Depending on impedance curve the amplifier sees different impedance values depending on the signal spectrum.
The Impedance curve by itself does not change.


BTW mine argumentation is poorly discussed even by AES/EIA societies but, it's a well known problematic.

You are correct that the actual load or impedance that an amplifier sees is dependant on the signal.

However, the rated nominal impedance is a minimun value. The impedance will be at least this high
under all signal conditions. The minimum value used occurs just above resonance and is often similar to
the minimum value at zero Hz (the DC resistance value). This actual value rarely will be 4, 8, or 16 ohms
exactly. A standard value of 4, 8, 16, etc is selected as the nominal value.

Amp manufacturers need to be aware of this. When rating an amp to handle an 8 ohm cabinet, the amp
needs to be able to actually handle 6 ohms, as the actual impedance could be that low.