Distribution of power

[lownote]

If I daisy chain two cabs of different specs in terms of numbers of drivers and power but the same ohm-age, how does the head distribute the power between to the two cabs?  For example, say I couple a Phil Jones C8 (8x5") 800w 8 ohms with a Cab 47 (4x7") 300w 8 ohms. Does one cab get more power than t'other? 

[paul_c2]

Same ohms ------> same power delivered to both.

[Bill Fitzmaurice]

The head doesn't distribute power. The relative impedances of the cabs does.

[Killed_by_Death]

6 hours ago, lownote12 said:

ohm-age

Impedance

It's called Impedance instead of Resistance, because it changes due to frequency changes.

Two 8-Ohm cabinets will receive a roughly equal amount of Power from the amp, but how they each respond to that Power will be different.

 

[paul_c2]

40 minutes ago, Killed_by_Death said:

 

Two 8-Ohm cabinets will receive a roughly equal amount of Power from the amp, but how they each respond to that Power will be different.

 

Good point - if the sensitivity is wildly different between them, the apparent sound volume out of them will also be different.

[Dan Dare]

A C8 is less efficient than a CAB47, so the perceived volume from each will not be the same. Also, I'm pretty sure the C8 is 4 ohms. It's effectively two C4s, which are 8 ohms each,  in one box.

[Bill Fitzmaurice]

2 hours ago, Killed_by_Death said:

 

It's called Impedance instead of Resistance, because it changes due to frequency changes.

It's called impedance because ohmage is what you pay to Clapton. 😊

Besides which, impedance and resistance aren't the only things measured in ohms. There's also capacitive and inductive reactance. You'll never see a proper engineering document that doesn't say which of those four is being referred to with respect to a value in ohms.

[Killed_by_Death]

1 minute ago, Bill Fitzmaurice said:

You'll never see a proper engineering document

You're probably correct.

Although, I did see many Engineering documents when I was heading up a Document Control center on a refinery construction project, but those were mostly about Piping & Tanks.

 

[Bill Fitzmaurice]

Usually you'll see R and Z listed in ohms, with R referring to DC resistance and Z impedance. C for capacitance is measured in microfarads, uF, Le for inductance is measured in millihenries, mH. You seldom see capacitive reactance, Xc, or inductive reactance, Xl, both measured in ohms, other than in a spec sheet for a given capacitor or inductor. You do see the result of Xc and Xl in Z, as impedance is the sum of R, Xc and Xl.  R is a constant value irrespective of frequency, but both Xc and Xl vary with frequency, and along with them Z.

[Killed_by_Death]

 

People should use nF more, 47 nF or 22 nF, not 0.047 µF

 

[Merton]

34 minutes ago, Killed_by_Death said:

Although, I did see many Engineering documents when I was heading up a Document Control center on a refinery construction project, but those were mostly about Piping & Tanks.

 

Oooh now you’re getting into fun stuff. Material grades and specs, pipe schedules, NDT specs and standards, welding requirements etc etc 🤓

[Killed_by_Death]

 

Molybdenum alloys were the biggest PITA, special welding circumstances & preparation.

I was flummoxed to know that Steve Harris uses Monel string!

 

[Merton]

Haha! I had a similar experience when I had the same revelation 🙃

[Lfalex v1.1]

3 hours ago, Killed_by_Death said:

Impedance

It's called Impedance instead of Resistance, because it changes due to frequency changes.

 

 

Which can, in turn, be illustrated by a graph, which shows the Modulus of Impedance; the way in which Impedance varies by frequency.

*Please note I have no affiliation with Modulus, nor am I on their payroll etc. etc.

** Other manufacturers of graphite necks are available.

😉

[Killed_by_Death]

 

Young's Modulus is the one I'm accustomed to, for stiffness, I like to experiment with necks.

 

[Bill Fitzmaurice]

1 hour ago, Killed_by_Death said:

 

People should use nF more, 47 nF or 22 nF, not 0.047 µF

 

It depends on the application. 22nF or 47nF would be common in electronics, but never in a crossover. The value range there mainly runs between 2uF and 100uF.

[Killed_by_Death]

 

I just find it irrationally annoying to me when folks add a decimal point & then use a smaller unit of measure. It's like commenting that you had 3,000 milligrams of Sodium. NO, you had 3 Grams!

 

[Count Bassy]

1 hour ago, Killed_by_Death said:

 

I just find it irrationally annoying to me when folks add a decimal point & then use a smaller unit of measure. It's like commenting that you had 3,000 milligrams of Sodium. NO, you had 3 Grams!

 

What about the otherway round though.

0.005 Metres instead of 5mm?

[Killed_by_Death]

 

I know a guy who likes to inform people he can only have 3,000 milligrams for Sodium/day, but I doubt he described driving distances in Feet, LOL!

 

[Bill Fitzmaurice]

1 hour ago, Killed_by_Death said:

 

I just find it irrationally annoying to me when folks add a decimal point & then use a smaller unit of measure. It's like commenting that you had 3,000 milligrams of Sodium. NO, you had 3 Grams!

 

That goes to marketing. Selling a bottle of 1000 mg pills makes it sound like you're getting something much better than a bottle of 1g pills.

[Killed_by_Death]

 

Feeling fancy yesterday, so we bought Evian in 1 Liter bottles, & labeled as such.

 

[Bill Fitzmaurice]

Shame, you could have got 1000 milliliters for the same price.

[Lfalex v1.1]

Surely 61.024 ci? 😉

That said, I use Metric for "small" measurements, and go back to Imperial for longer distances; Kilometres are meaningless relative to miles...

Edited May 19, 2021 by Lfalex v1.1

[Killed_by_Death]

 

When I returned to the U.S. from Asia I was still speaking CID displacement for engines & got strange looks. It's all Liters now, I recall it starting with the 5.0 Liter Mustang GT:

This wasn't mine, but I have one VERY similar.

 

[BassmanPaul]

If you add an 8Ω load in parallel with a 4Ω load (2.67Ω total) the 4Ω load will get two thirds of the available power.

In series (12Ω total) the 4Ω load will get one third of that power.