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Running a 16 ohm and 8 ohm cabinet at 5.33 ohms

Mr.Sharkfist

Mr.Sharkfist

Nov 8, 2015
105
53
Holland, MI
#1
Hello, I have a question regarding the safety of running a 5.33 ohms load? Both of my bass Amps can handle a load of 4 ohms which I've seen on other threads is "close enough" to 5.33 ohms to run an 8 ohm and 16 ohm cab together, but my question remains. Is this safe? For example on the Hughes and Kettner website it says you can do this safely on its page about impedance but the Orange AD200B manual says that mismatched impedance is a no-go. So I just want to know which is it? Is it safer with solid state heads? Thanks in advance.
 
#2
It depends on the amp. What kind of amps exactly? Need more info.

If it's a normal solid state amp, then you're fine since you're above the 4 ohm minimum. If it's a tube amp, might be a different story.

BUT. Even if it's 'safe' for the amp, it's not a good idea because the 8 ohm cab will get twice the power and possibly blow because you will be turning the amp up trying to hear the 16 ohm cabinet.
 
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#3
mmbongo said:
It depends on the amp. What kind of amps exactly? Need more info.

If it's a normal solid state amp, then you're fine since you're above the 4 ohm minimum. If it's a tube amp, might be a different story.

BUT. Even if it's 'safe' for the amp, it's not a good idea because the 8 ohm cab will get twice the power and possibly blow because you will be turning the amp up trying to hear the 16 ohm cabinet.
Click to expand...
It's two tube amps. A Marshall 1992LEM is what I'm using to run the 8 ohm and 16 ohm cabinets. That and an Orange AD200B. I usually just use a 4 ohm cab for the Orange but I'd like to use the 8 ohm and 16 ohm cab sometimes too.
 
#6
Tube amps use an output transformer for the speakers and react differently to speaker loads than solid state amps.
The Orange has two 4 ohms and one 8 ohms speaker outputs. I would heed Orange's guidance and not connect a 16 ohms speaker to that amp.
  • 1 x 8 cabinet connected to the 8 Ohm output
  • 1 x 4 Ohm cabinet connected to one of the 4 Ohm outputs
  • 2 x 8 Ohm cabinets each connected to one of the 4 Ohm outputs
Although you didn't specify which H&K amp you have, it looks like the resultant 5.33 ohms from a 8||16 ohms stack should be okay.
I'm not aware of any 16 ohms bass speakers. What are you planning to use?
 
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#7
abarson said:
Tube amps use an output transformer for the speakers and react differently to speaker loads than solid state amps.
The Orange has two 4 ohms and one 8 ohms speaker outputs. I would heed Orange's guidance and not connect a 16 ohms speaker to that amp.
  • 1 x 8 cabinet connected to the 8 Ohm output
  • 1 x 4 Ohm cabinet connected to one of the 4 Ohm outputs
  • 2 x 8 Ohm cabinets each connected to one of the 4 Ohm outputs
Although you didn't specify which H&K amp you have, it looks like the resultant 5.33 ohms from a 8||16 ohms stack should be okay.
I'm not aware of any 16 ohms bass speakers. What are you planning to use?
Click to expand...
The 16 ohm cabinet is a vintage Marshall 4x12 JCM 800 bass cabinet. I'm using this with an 8 Ohm Ampeg 4x12 into a Marshall 1992LEM
 
#8
Nominal load is around 5 ohms

So they should be both be on the 4 ohm tap.

The impedance is only slightly higher which is non issue.

5 ohm load would be less current on a solid state output section.
5 ohm load would be less current on a 4 ohm transformer tap.
 
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#9
808State said:
Nominal load is around 5 ohms

So they should be both be on the 4 ohm tap.

The impedance is only slightly higher which is non issue.
Click to expand...
From an electrical view of things 5.33 Ohm (which is the presented load by the cabs in parallel mode) is just as close to 4 Ohm as it is to 8 Ohm.

configuration - A
5.33 Ohm on the 8 Ohm tap
33.33% of 8 Ohm equals 2.666 Ohms
8 Ohm - 2.666 Ohm = 5.333 Ohm

configuration - B
5.33 Ohm on the 4 Ohm tap
33.33% of 4 Ohm equals 1.333 Ohms
4 Ohm + 1.333 Ohm = 5.333 Ohm

For both configurations (4 Ohm tap and 8 Ohm tap) the impedance "mismatch" on the output transformer does equal 33.33% for a load that equals 5.33 Ohm
 
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#10
My biggest issue is that with an 8 ohm speaker and a 16 ohm speaker, assuming you're running them in parallel (8 in parallel with 16), you'll get far more of your power going into the 8 than into the 16, so I would wonder if your 16 would be adding much to the total sound level. Use your ears for that one. And also, watch the power handling on the 8 ohm.... since again I would think it would be reacting more to the amp's power output.
 
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#12
dkelley said:
My biggest issue is that with an 8 ohm speaker and a 16 ohm speaker, assuming you're running them in parallel (8 in parallel with 16), you'll get far more of your power going into the 8 than into the 16, so I would wonder if your 16 would be adding much to the total sound level. Use your ears for that one. And also, watch the power handling on the 8 ohm.... since again I would think it would be reacting more to the amp's power output.
Click to expand...
Yeah, it sounded like it was alright and had some good volume but I'll make sure to look out for that.
 
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#13
ThisBass said:
From an electrical view of things 5.33 Ohm (which is the presented load by the cabs in parallel mode) is just as close to 4 Ohm as it is to 8 Ohm.

configuration - A
5.33 Ohm on the 8 Ohm tap
33.33% of 8 Ohm equals 2.666 Ohms
8 Ohm - 2.666 Ohm = 5.333 Ohm

configuration - B
5.33 Ohm on the 4 Ohm tap
33.33% of 4 Ohm equals 1.333 Ohms
4 Ohm + 1.333 Ohm = 5.333 Ohm

For both configurations (4 Ohm tap and 8 Ohm tap) the impedance "mismatch" on the output transformer does equal 33.33% for a load that equals 5.33 Ohm
Click to expand...
Interesting, I didn't know that. So that mismatch on the power transformer is safe?
 
#14
ThisBass said:
From an electrical view of things 5.33 Ohm (which is the presented load by the cabs in parallel mode) is just as close to 4 Ohm as it is to 8 Ohm.

configuration - A
5.33 Ohm on the 8 Ohm tap
33.33% of 8 Ohm equals 2.666 Ohms
8 Ohm - 2.666 Ohm = 5.333 Ohm

configuration - B
5.33 Ohm on the 4 Ohm tap
33.33% of 4 Ohm equals 1.333 Ohms
4 Ohm + 1.333 Ohm = 5.333 Ohm

For both configurations (4 Ohm tap and 8 Ohm tap) the impedance "mismatch" on the output transformer does equal 33.33% for a load that equals 5.33 Ohm
Click to expand...
Damn... mathing too much for me right now. I'm developing a console C# app for work right now and come here to get away from thinking.

heh heh
 
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#16
Mr.Sharkfist said:
The 16 ohm cabinet is a vintage Marshall 4x12 JCM 800 bass cabinet. I'm using this with an 8 Ohm Ampeg 4x12 into a Marshall 1992LEM
Click to expand...
yeah, don't

it would probably be safe for the amp but no way am i running my own vintage '78 100w marshall tube head with anything besides an exact impedance match, especially at demanding loud volume. tube marshalls by reputation are less tolerant of impedance mismatches than tube fenders.

on top of that, like folks are saying the 8Ω cab would get way more of the amp power than the 16Ω cab so it would be goofy and unbalanced, one cab would be louder than the other.
 
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#19
Mr.Sharkfist said:
Interesting, I didn't know that. So that mismatch on the power transformer is safe?
Click to expand...
What I try to tell is that the amount of "mismatch" is just the same for both configurations in question.

There was no question asked if a mismatch of -33.33% was more safe for the 1992LEM than a mismatch that equals +33.33%.
By default I'd expect the transformer (and amp design) of the 1992LEM robust enough to handle safely +/- 33.33% mismatch at the OT.
Just to ensure safe operation it may be a good idea to contact Marshall and ask them a question if +/- 33.33% of mismatch at the OT is within safe operation margins for the 1992LEM.
 
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#20
Never use two taps at once unless the manual says that it’s alright. For example, don’t plug a 4 ohm cab into a 4 ohm tap AND an 8 ohm cab into an 8 ohm tap.

The nominal resistance of the cab is an indication of how hard it is to push current into it. Daisy chain a 16 ohm cab and an 8 ohm cab. More power will flow into the lower resistance 8 ohm cab, chances are it will be louder. Cabinet sensitivity plays a roll as well, to what extent depends on the cabs.
 
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