Still Unsure: So 4, 8, 16 Ohm - Which Do I Need ?

Wazmeister

I know, I know this has been asked before... 

But, I don't get it yet...

So, Redplate RP50R Head - which would Ohm speakers would I choose and why ?

Cheers

ICBM

I'm not familiar with that amp, but conventional wisdom is that you ideally want the cabinet to be the highest impedance the amp can be set to, so you're using all of the transformer winding. While I don't think this really matters (at least for a decent quality transformer) it does still give you the most options for connecting a second cab, so I would still do it unless it restricts the choice of speakers in some way.

Wazmeister

Ok.... Most Redplate RP50s in combo come with a V30 8 Ohm, and indeed most of my other cabs seem 8 ohm.

I was just wondering why this is ?

ICBM

What impedance settings does the amp have?

If most of your other cabs are 8 ohm it's probably best to get another 8, assuming it has a 4-ohm setting - although you can safely mix an 8 with a 16 too (with the amp set to 4 ohms), you just get 2/3 of the power going to the 8-ohm one.

Wazmeister

impedance settings are 2 4 8 16 

ICBM

Given that and if your other cabs are 8-ohm, I would also probably go for 8. You can still even combine it with a 4-ohm cab if you like, with the amp set to 2.

Wazmeister

@ICBM - brill - as ever mate, thanks for all your help !

Voxman

ICBM said:

I'm not familiar with that amp, but conventional wisdom is that you ideally want the cabinet to be the highest impedance the amp can be set to, so you're using all of the transformer winding. While I don't think this really matters (at least for a decent quality transformer) it does still give you the most options for connecting a second cab, so I would still do it unless it restricts the choice of speakers in some way.

I found a couple of articles which are interesting:

http://blog.hughes-and-kettner.com/ohm-cooking-101-understanding-amps-speakers-and-impedance/

http://www.prestonelectronics.com/audio/Impedance.htm

But I still get confused by impedance, even after all these years. If you have the option of setting your head to 4 Ohms, 8 Ohms, or 16 Ohms, and you have the option of running a 4 Ohm, 8 Ohm or 16 Ohm cab presumably you'd want to match the cab and amp setting ie 4 Ohm to 4 Ohm, 8 Ohm to 8 Ohm, and 16 Ohm to 16 Ohm.  But would the volume and tone be the same in each instance?  

Wazmeister

@voxman - who knows mate ?! 

I'll stick to 8 ohm me thinks...

StuartMac290

ICBM said:

I'm not familiar with that amp, but conventional wisdom is that you ideally want the cabinet to be the highest impedance the amp can be set to, so you're using all of the transformer winding. While I don't think this really matters (at least for a decent quality transformer) it does still give you the most options for connecting a second cab, so I would still do it unless it restricts the choice of speakers in some way.

Interesting. One of my amps is a Bad Cat Classic Deluxe, with the Bad Cat 8ohm 12" proprietary speaker, and if I connect a 1x12 Bad Cat extension cabinet and drop the impedance to 4ohms on the amp accordingly, it sounds both quieter and duller.

I also have a Black Cat 30 head and an accompanying Bad Cat 2x12 cab, which runs at 4ohms with the speakers wired in parallel. I've often wondered if I'd be better wiring the speakers in series and running the amp at 16ohms. Any thoughts?

ICBM

Voxman said:

If you have the option of setting your head to 4 Ohms, 8 Ohms, or 16 Ohms, and you have the option of running a 4 Ohm, 8 Ohm or 16 Ohm cab presumably you'd want to match the cab and amp setting ie 4 Ohm to 4 Ohm, 8 Ohm to 8 Ohm, and 16 Ohm to 16 Ohm.  But would the volume and tone be the same in each instance?  

Theoretically, yes. The power output should be the same in all cases if the transformer winding ratios have been done correctly, although there are differences in tone between different impedances of the same speaker and between transformer taps due to the different inductance of higher or lower numbers of windings.

StuartMac290 said:

One of my amps is a Bad Cat Classic Deluxe, with the Bad Cat 8ohm 12" proprietary speaker, and if I connect a 1x12 Bad Cat extension cabinet and drop the impedance to 4ohms on the amp accordingly, it sounds both quieter and duller.

Could the cabs be wired out of phase? Although that would generally give a thinner rather than duller tone, as well as less volume. I would be surprised, if both are Bad Cat cabs anyway. Or could the output taps be connected wrongly? I've come across that before… running the amp into too low an impedance will sound quiet and dull.

StuartMac290 said:

I also have a Black Cat 30 head and an accompanying Bad Cat 2x12 cab, which runs at 4ohms with the speakers wired in parallel. I've often wondered if I'd be better wiring the speakers in series and running the amp at 16ohms. Any thoughts?

Don't know - it will probably sound a bit different. The only way to know is to try it.

ChrisMusic

ICBM said:

StuartMac290 said:

I also have a Black Cat 30 head and an accompanying Bad Cat 2x12 cab, which runs at 4ohms with the speakers wired in parallel. I've often wondered if I'd be better wiring the speakers in series and running the amp at 16ohms. Any thoughts?

Don't know - it will probably sound a bit different. The only way to know is to try it.

 And if you do @StuartMac290 ;, please let us know what you feel about the results, I am interested in this too.

webrthomson

I was looking at this today which seems relevent to the dicsussion

http://www.rig-talk.com/forum/viewtopic.php?f=3&t=185580