ABM600- 2.67ohms

[agedhorse]

13 hours ago, Sparky Mark said:

In the real world I'm not at all surprised that the ABM600 outperforms many amps with higher advertised outputs. The ABM600 is probably running with extremely low % THD at its rated output whereas many amps are now rated at relatively high %THD. When I owned an ABM600 it was much more powerful than my 800 watt head. I believe Ashdown when it states its peak power of 1200 watts whilst others might struggle to produce peak levels even 20% above their published continuous outputs. 

The peak power of ANY 600 watt rms amp IS 1200 watts. It’s just two ways of describing exactly the same thing. It’s just a math conversion between units. 

[agedhorse]

8 hours ago, itu said:

I think that...

 

Because people mix power (W) and loudness (dB), these kind of questions come up every now and then.

 

Wattage means how much energy a power amp can push to the load (a cab). If the load stays the same, doubling the power will increase loudness around 3 dB. This is pretty much the lowest difference you can hear: from 500 W to 1000 W the difference is up to 3 dB (if the load stays the same).

 

Power (wattage) consists of impedance (Z, meaning resistance, inductance, and capacitance; this is frequency dependent), voltage (V, volts), and current (A, amperes).

 

Volts and amperes can be easily calculated, as we already know both the impedance of a cab and the wattage of an amp. Let's say it's 400 W, and Z = 8 ohms.

 

I = U / R [A = V / Z]

and

P = U x I [W = V x A]

 

P = U x U / Z, or U x U = P x Z

400 W x 8 ohm = 3200 VV => U = 56.5 V

 

I = P / U => 400 W / 56.5 V = 7 A

Now is this clear? Here we have an 8 ohm cab, and an amp that pushes up to 7 amperes to that cab.

 

The next step is to understand, what happens, when impedance is halved (the equation assumes that the power amp is capable to push double wattage to that 4 ohm cab):

800 W x 4 ohm = 3200 VV => U = 56.5 V

BUT the big thing here is this:

Current has to double, as

I = P / U => 800 / 56.5 = 14 A (!)

That amount of current means far bigger components that can handle big currents = heat. It is not so uncommon that the amp is not able to cool itself down with such currents. In worst case the amp section may melt. When we go further down to lower impedances, 2 ohms equals 28 A, and 1 ohm equals 56 A!

 

A very rough wire diameter table would look like this:

7 A - 1 mm2, AWG 18 

14 A - 2.5 mm2, AWG 14

28 A - 6 mm2, AWG 10

56 A - 25 mm2, AWG 4 (components have to be enormous!)

 

You should understand this: it is far easier to increase voltage than reduce impedance. If the amp is not capable of pushing energy to a super low Z cab, 8 ohm cab may actually be the louder one!

Your wire size examples are for long runs of wire and based on a combination of voltage drop,  temperature rise and continuous duty cycle. They are generally accepted sizes based on installed building applications with common insulation types. 
 

Components and component interconnections are sized differently for each application. For example I work with 50A transistors that have leads roughly equivalent to 2.5mm dia wire. It’s because the leads are short and the parts are used in <50% duty cycle applications. 

[Sparky Mark]

1 hour ago, agedhorse said:

The peak power of ANY 600 watt rms amp IS 1200 watts. It’s just two ways of describing exactly the same thing. It’s just a math conversion between units. 

Agreed, but there have been instances where some amplifiers don't actually achieve their advertised continuous outputs when tested.

Of course the output test method is critical so I wonder whether some amp manufacturers publish numbers that are just as unlikely to be achievable in the real world as automotive manufacturers' advertised fuel efficiency figures?

[Jakester]

12 hours ago, DGBass said:

2/4/8 ohm switching is available on quite a few modern class-d and hybrid amps these days eg. Mesa Subway comes to mind. From what I can see from manufacture blurb there isn't any power advantage running at 2.67 or  even 2 ohms so it does seem purely a cab configuration feature. 

 

Interestingly (to me, at least!) I came across the GK Legacy amps and they appear to offer switchable impedance down to 2ohms, to allow different combinations of cabs. Their combos also deliver full power at both 4ohm and 8ohms with power being 'diverted' between the cabs as necessary. I guess we'll see features like this more often in future.

[chyc]

Ashdown do actually offer something from their ABM family called the Geezer Butler Head of Doom. This is as far as I can tell an ABM 600, but with the option to daisy chain them, so with a thick enough wallet you can have as many cabinets as needed. I would suggest that there are better ways of doing this, but it must be quite a sight on stage!

 

Diagram below taken from Ashdown's own website shows a setup potentially running at 1Ω

 

 

 

 

[Woodinblack]

6 minutes ago, chyc said:

Diagram below taken from Ashdown's own website shows a setup potentially running at 1Ω

 

No, don't confuse the things - that shows them running 4 speakers - if they were all 4Ω and in parallel then yes that would be 1Ω, but they aren't, they are 4 separate 4Ω speakers being driven by 4 separate amps, driven from the same source.

And note this is perfectly possible with 4 separate ABMs (or even 2 separate ABM1200s) just that it has a mod to make this easier.

[BigRedX]

Poor old Ashdown still thinking that these kinds of rigs actually contribute to anything the musicians or the audience hears. 

[bartelby]

11 minutes ago, BigRedX said:

Poor old Ashdown still thinking that these kinds of rigs actually contribute to anything the musicians or the audience hears. 

 

 

I think Ashdown, and lots of other companies, still market for the visuals of massive rigs. 

[chyc]

23 minutes ago, Woodinblack said:

 

No, don't confuse the things - that shows them running 4 speakers - if they were all 4Ω and in parallel then yes that would be 1Ω, but they aren't, they are 4 separate 4Ω speakers being driven by 4 separate amps, driven from the same source.

And note this is perfectly possible with 4 separate ABMs (or even 2 separate ABM1200s) just that it has a mod to make this easier.

That's a fair distinction. I did wonder if I needed to write that it was the equivalent of a setup running at 1Ω, and yes there are better, and cheaper ways of doing it.

[Lozz196]

13 minutes ago, bartelby said:

 

 

I think Ashdown, and lots of other companies, still market for the visuals of massive rigs. 

Plus they sound good. 

[Woodinblack]

27 minutes ago, BigRedX said:

Poor old Ashdown still thinking that these kinds of rigs actually contribute to anything the musicians or the audience hears. 

 

I don't think so, they did a signature thing for Geezer Butler, and I am sure as a result they sold a few units and their company carried on trading. I almost bought one once when I saw a clearence one. I doubt anyone ever needed that setup, but the unit itself looks really cool (and you can see with the EVO V, a lot of people thought so!) and that is 80% of the job!

[fretmeister]

55 minutes ago, BigRedX said:

Poor old Ashdown still thinking that these kinds of rigs actually contribute to anything the musicians or the audience hears. 

 

Ashdown are not Apple. They don't come up with an idea (or pinch it from Star Trek) and then worry about how to market it.

Ashdown build things their customers want. 

 

If that approach starts to affect sales, then they will change. But they are customer driven more than innovation driven. If you want to blame anyone, blame the customers.

[BassAdder60]

Ashdown are also I believe more pro A/B amps that can be easily repaired throughout its life, something they still stand by today.

Class D for them is in some cases a disposable amp should it seriously go wrong IE power module dies etc

 

However the other big brands are heading down that Class D road for very good reasons and that is the public want light weight gear now.

 

We are slightly off topic but the question about modding an ABM600 to 2.67 ohms  was purely out of interest if possible, it’s not. 
Mesa, Genzler, GK, Aguilar and more are offering amps to 2ohms or 2.67 ohms which today is fantastic for mixing 8 and 4 ohm cabs or running more combinations. 
 

The ABM600 is a superb amp and will remain with me for now sitting on my 4ohm Ampeg SVT212AV 600w cab. 

Edited June 1, 2023 by BassAdder60

[bartelby]

1 hour ago, Lozz196 said:

Plus they sound good. 

 

As an owner of 3 Ashdown amps & 3 Ashdown cabs, I'm not going to argue there

[Phil Starr]

4 hours ago, Jakester said:

 

Interestingly (to me, at least!) I came across the GK Legacy amps and they appear to offer switchable impedance down to 2ohms, to allow different combinations of cabs. Their combos also deliver full power at both 4ohm and 8ohms with power being 'diverted' between the cabs as necessary. I guess we'll see features like this more often in future.

Hi Jake

 

from the GK Legacy manual 

 

 

Theoretically the power should double as the impedance halves but like most amps this one won't quite double the power into 4 ohms. I would imagine the limit is the power supply current. If the power supply is limited to 800W then ultimately so is the amp so you'll get roughly 800W into anything lower than 4 ohms. 

[BigRedX]

As others have said output power of your amp is no real measure of loudness.

 

You'll probably get better results by having better designed cabs with more efficient drivers in them.

Edited June 1, 2023 by BigRedX

[itu]

7 hours ago, agedhorse said:

Your wire size examples are for long runs of wire...
 

...It’s because the leads are short and the parts are used in <50% duty cycle applications. 

True, and well said. My modest thought was to give an idea, that the change in impedance requires something from the amp, too. Yes, in this case pretty much exaggerated.

 

Could you please tell main differences between a tiny home amp and some 50 A workhorse? Copper traces, components...

 

That duty cycle is of interest, and many - including me - tend to forget this.

Edited June 1, 2023 by itu

[agedhorse]

The current in an electrical power circuit is generally considered to be continuous (there are a few exceptions, every region is slightly different) and the distances are much longer than what is being dealt with on a PCB or interconnection wiring.

 

50 amps of building power circuit would require at least 8 times the copper area as an audio circuit or internal power wiring for an audio device). This is because the audio circuits are designed around a minimum 12.5% duty cycle, and the voltage drop is based or wire cross-sectional area its length and the current in the wire. Power electrical current is based on 100% duty cycle (80% in the US for non-continuous loads). 

[agedhorse]

On 01/06/2023 at 03:32, BassAdder60 said:

Ashdown are also I believe more pro A/B amps that can be easily repaired throughout its life, something they still stand by today.

Class D for them is in some cases a disposable amp should it seriously go wrong IE power module dies etc

 

However the other big brands are heading down that Class D road for very good reasons and that is the public want light weight gear now.

 

We are slightly off topic but the question about modding an ABM600 to 2.67 ohms  was purely out of interest if possible, it’s not. 
Mesa, Genzler, GK, Aguilar and more are offering amps to 2ohms or 2.67 ohms which today is fantastic for mixing 8 and 4 ohm cabs or running more combinations. 
 

The ABM600 is a superb amp and will remain with me for now sitting on my 4ohm Ampeg SVT212AV 600w cab. 

There are companies that have no problem supporting 15-20 year old class D amps as well, making them non-disposable. 
 

it depends on the company and not the technology used ime.