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Impedance etc

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23 minutes ago, Huge Hands said:

Must be on later models - I have two early ones (were known as the Retro 2x10 back then) and there is no switch.  You had to get a loom fitted to change them from 4ohm to 12ohm apparently? 

The switchs are fitted as a matter of course these days. It's now called the Two10S, I got BF to add the switch to my first 210.

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4 hours ago, Quilly said:

1809085148_4_8ohm.PNG.14b87d011b464e88f74a042d4d001c27.PNG

Why don't more speaker manufacturers do this?...seems like such a no-brainer. 

Because IMO it doesn't give you any advantage. There's a whole thread on this already.

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You don't even have to search out other threads, why it's not useful in general has been explained in this thread, repeatedly, including just a few posts before this one. The only reason to want a 4 ohm/8ohm 112 cab is to allow using it with a valve amp that needs a maximum 4 ohm load and with an SS amp that won't take a 4 ohm load. 

Edited by Bill Fitzmaurice

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I was running an 8 ohm valve amp into a 4 ohm cab for a while with no issues (the amp also has 16ohm outputs), I stopped because I'm just nervous of damaging the amp. I bough a 4/12 ohm switch for the cabinet in question (8 ohm isn't possible for the configuration of cab). My question is : Is it better to run 8 ohm amp into 12 ohm cab OR use the 16 ohm amp out into 12 ohm cab. My hunch is the latter is probably better for a valve amp to prevent damage to the transformer. Still not ideal for the valves but better than the current set up.  

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On 07/05/2019 at 06:10, Quilly said:

Is it better to run 8 ohm amp into 12 ohm cab OR use the 16 ohm amp out into 12 ohm cab.

The speaker impedance ratings for valves is the maximum, that for SS is the minimum. Use the tap on a valve head that's equal to or more than the speaker impedance, use a total speaker load on an SS amp that's equal to or greater than the amp rating.

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1 hour ago, Bill Fitzmaurice said:

The speaker impedance ratings for valves is the maximum, that for SS is the minimum. Use the tap on a valve head that's equal to or more than the speaker impedance, use a total speaker load on an SS amp that's equal to or greater than the amp rating.

I’m using a 4 ohm bass cab with an 8 ohm guitar head and it sounds sublime with bass . Just for home use mind. Is that because I’m driving the tubes a bit harder ? 

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image.png.d47141b2aa29ffdc8a47a46739b3644d.png

I Cant understand why these arent readily available by multiple suppliers. 

 

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2 minutes ago, Quilly said:

image.png.d47141b2aa29ffdc8a47a46739b3644d.png

I Cant understand why these arent readily available by multiple suppliers. 

 

Because in order to work their "magic" they will dissipate a significant proportion of the amplifier's power as heat through the resistors required to match the input and output impedances. The more different the input and output impedances are the less efficient it makes your rig in terms of power being used to produce sound. Also the particular device pictured is only good for amplifiers up to 100 Watts, which makes it virtually useless for bass rigs.

A device rated for at least 300 Watts (which is what most bass players will need as a minimum) is going to be significantly bigger, heavier and probably require fan cooling. 

Most sensible people simply buy a rig where the amp and speakers are properly matched.

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I agree that the Z matcher is not an ideal choice for matching a cab to an amp. 

I don’t agree that you need a minimum 300 watts.  Though there’s plenty of threads about that already. 

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2 hours ago, xgsjx said:

I agree that the Z matcher is not an ideal choice for matching a cab to an amp. 

I don’t agree that you need a minimum 300 watts.  Though there’s plenty of threads about that already. 

For bass you probably would need to use a 300 Watt amp if you were going also use an impedance matcher, as any setting that isn't a 1:1 match is going dissipate at leat 1/3 of the amp's power as heat through the resistors rather than sound through the speakers.

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