ABM600- 2.67ohms

[BassAdder60]

Anyone ever had their ABM600 modified to run at 2.67ohms instead of 4 ohms ? 
 

Perhaps a question for Dave @ Ashdown? 

[Mudpup]

Why would you want to? (Serious question BTW)

[itu]

You want to mix 8 and 4 to get 2.67. Do you want to get more vol, or do you just happen to have two cabs?

 

If loudness is low, you can use nearly whichever load. But when you turn the master past 9 o'clock, you need to think about the power amp: the lower the impedance, the higher the current. When current rises, components start to warm up. Very big power equals very hot parts, and can lead to melt down.

[BassmanPaul]

I'm don't think that an amplifier can be modified to run a load it wasn't designed for. It would entail a rebuild of the power amp AND the power supply. It would be costly even if it could be done.

 

If you are considering this to enable you to run your existing cabinetry it would be far better get rid of the 4Ω box and get an identical second 8Ω cab.

Edited May 29, 2023 by BassmanPaul

[BassAdder60]

10 minutes ago, Mudpup said:

Why would you want to? (Serious question BTW)

My main rig now is a 212 4ohm cab and 112 8 ohm cab which I use with the Tonehammer 700 ( superb sound )

 

I either mod the Ashdown for backup duty or sell it and buy a different amp.

 

I know the obvious ie disconnect one cab and use just the 212 but that’s not what I’m trying to do. 
 

The Ampeg cabs all have the same 12” speakers and using it as a 2.67 ohm rig shares the power across three speakers and it’s an awesome sound and nice and tall too. 
I’ve sold all my Ashdown gear except the ABM600 head which was next to go but thought if it could be modded at Ashdown HQ I would keep it and use it for some gigs and alternate between the TH700

[BassAdder60]

9 minutes ago, itu said:

You want to mix 8 and 4 to get 2.67. Do you want to get more vol, or do you just happen to have two cabs?

 

If loudness is low, you can use nearly whichever load. But when you turn the master past 9 o'clock, you need to think about the power amp: the lower the impedance, the higher the current. When current rises, components start to warm up. Very big power equals very hot parts, and can lead to melt down.

I already have the cabs SVT212AV ( 4ohms ) and SVT 112AV ( 8 ohms )

Note the TH700 amp I now use runs down to 2.67 ohms as standard.

Bonus if I could get the ABM600 to do the same 

[Bunion]

The Genzler Magellan heads can be run at 2.67 for use with the 3 x 8ohm array might be worth looking at picking one of those up if it’s for a back up the 350 and 800 I believe have this capability 

[DGBass]

Ashdown's current ABM600 design is based on a 4 ohm minimum load recommendation and the whole output stage including the output board and components, cooling, thermal cut out switch, fuse values and transformer are geared for that. With most amps, exceeding design limits usually only ends one way, and thats an expensive repair bill. At a guess the first symptom that the amp wasn't happy at 2.67 ohms would be the thermal limit switch cutting in early dues to excess heat, something that i've never experienced on these amps run at 4 ohms. The transformer might also be prone to over current damage and thats if you didn't blow fuses first. They are quite strong amps and in real world use an ABM would probably run at 2.67 ohms at a reasonable volume for a short while at least before something would fail prematurely. There probably is a way to do it but I daresay it would cost a bit to re-design and build an ABM output stage that would be happy to run all day at 2 ohms or thereabouts. Definitely a question for the Ashdown engineers.🙂

[BassAdder60]

1 hour ago, Bunion said:

The Genzler Magellan heads can be run at 2.67 for use with the 3 x 8ohm array might be worth looking at picking one of those up if it’s for a back up the 350 and 800 I believe have this capability 

I’ve been looking at the Magellan 800 and I’m tempted to add it to my collection based on reviews and 2.67ohms of course 

[Mudpup]

I've had both an ABM600 and a Magellan 800. The Magellan doesn't sound anything like an ABM and isn't as loud in a band situation I'm my experience. Both were run at 4ohms into a pair of Barefaced BB2 cabs. The Magellan is one of the best class D amps I've had but it doesn't have as much kick as the Ashdown when it's getting loud.

[BassAdder60]

So it’s confirmed it’s not possible to mod and deemed a bad idea by Ashdown. 
 

Need to think about the ABM600’s future and maybe use it with my single 212 cab ( 4 ohms ) only or sell it ?? 

 

I have as said the Aguilar TH700 which is designed to run continuously at 2.67ohms so this was an idea that saved the ABM600 collecting dust !! 
 

 

 

 

[fretmeister]

Or get a 4 ohm Barefaced 8x10 and not worry about volume needs ever again. For anyone. Because we'll all be deaf!  

Edited May 31, 2023 by fretmeister

[BigRedX]

If it's just for backup and you like the sound of your main amp, why not get another one the same? Anything else will sound different even with the same cabs, and you'll probably be disappointed. 

 

For me the whole point of a backup is that is tis a like-for-like replacement for whatever I currently use and doesn't require any adjustment in order to get the sound I want.

[la bam]

An ABM600 and 2x12 cab cant possibly be too quiet can it?

 

[BassAdder60]

1 hour ago, la bam said:

An ABM600 and 2x12 cab cant possibly be too quiet can it?

 

Definitely loud enough with the 212 cab so it may be used with just one cab 

[Sparky Mark]

On 29/05/2023 at 20:08, Mudpup said:

I've had both an ABM600 and a Magellan 800. The Magellan doesn't sound anything like an ABM and isn't as loud in a band situation I'm my experience. Both were run at 4ohms into a pair of Barefaced BB2 cabs. The Magellan is one of the best class D amps I've had but it doesn't have as much kick as the Ashdown when it's getting loud.

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. 

Edited May 31, 2023 by Sparky Mark

[la bam]

20 minutes ago, BassAdder60 said:

Definitely loud enough with the 212 cab so it may be used with just one cab 

 

Yeh, I'm just confused if its loud enough with 1 cab, why youd need three or have to sell your amp?

[BassAdder60]

5 minutes ago, la bam said:

 

Yeh, I'm just confused if its loud enough with 1 cab, why youd need three or have to sell your amp?

The main cab is the Ampeg SVT212AV 4 ohm cab which when I got the ToneHammer 700 I decided to buy the matching SVT112AV 8 cab which together matches the 2.67 ohm rating the TH700 can run at. Amazing rig in so many ways. 
The Ashdown hasn’t been out of the house since so I was at the point of either selling it, using it with the SVT212AV cab only ( definitely good enough ) or discovering if Ashdown could mod it ( not possible) 

 

So that’s where I’m at and I might just use it on its own with my single SVT212AV cab and alternate between that setup depending on gig etc 

Edited May 31, 2023 by BassAdder60

[Phil Starr]

6 hours ago, BassAdder60 said:

So it’s confirmed it’s not possible to mod and deemed a bad idea by Ashdown. 

 

 

 

 

I don't understand why you haven't asked Ashdown directly. they really are very helpful

[Lozz196]

2 hours ago, BassAdder60 said:

The main cab is the Ampeg SVT212AV 4 ohm cab which when I got the ToneHammer 700 I decided to buy the matching SVT112AV 8 cab which together matches the 2.67 ohm rating the TH700 can run at. Amazing rig in so many ways. 
The Ashdown hasn’t been out of the house since so I was at the point of either selling it, using it with the SVT212AV cab only ( definitely good enough ) or discovering if Ashdown could mod it ( not possible) 

 

So that’s where I’m at and I might just use it on its own with my single SVT212AV cab and alternate between that setup depending on gig etc 

Sounds like an idea, use the ABM & 212 for smaller gigs, TH & both cabs for bigger gigs.

[BassAdder60]

17 minutes ago, Phil Starr said:

I don't understand why you haven't asked Ashdown directly. they really are very helpful

I did earlier this week and they said it’s not possible. 

[DGBass]

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. I'm probably not the first person who has expressed an interest to Ashdown for a class-d ABM or ADM if you like (Ashdown Digital Magnifier!) based around something like an 800 watt lighweight head with the all important ABM pre-amp in a neat modern rectangular lighweight box that will cope with 2/4/8 ohm loads. Impedance switching options also tend to appear where manufacturers offer cabs with 4 ohm options although I suspect the intention is to use just one 4 ohm cab rather than two or one 4 and one 8. Again the likes of Mesa offer this on selected subway cabs as do Aguilar on selected DB and SL cabs. Having two amps, a TH and an ABM is no bad situation to be in but which one will end up being the main and which the backup? I had a similar dilema between my ABM and an LMIII. Both good amps in their own right and although the LMIII was bought as a back up and was never needed, there were a few times its light weight got it the gig. My ABM won the day though and the class-d amp was sold on as it just couldn't deliver the same thump you get from an ABM. Ashdown might make 2 ohm capable top of the range amps( ABM's) at some point in the future but I fear I will likely be the owner of a bus pass before that happens😆  

[Woodinblack]

4 minutes ago, DGBass said:

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. I'm probably not the first person who has expressed an interest to Ashdown for a class-d ABM or ADM if you like (Ashdown Digital Magnifier!) based around something like an 800 watt lighweight head with the all important ABM pre-amp in a neat modern rectangular lighweight box that will cope with 2/4/8 ohm loads. 

indeed it is just for cab configuration. Not sure what the advantage of a class d abm is - they have other amps that are class D, the abm is a large transistor type.

[DGBass]

4 minutes ago, Woodinblack said:

Not sure what the advantage of a class d abm is

For me it would be the full ABM tube pre-amp thing in a lightweight smaller package with similar power. I don't think they've done anything yet with ABM level power and tube pre-amp tone in a small lightweight box?

[itu]

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!