Ohm Mismatch Question

[Buckeyedog]

Dude, doesn't work. Please explain how 4 16 ohm speakers can be wired for 8 ohm. If you wire them all in parallel, you get a 4 ohm cab. Series/parallel will make a 16 ohm cab. The only way it can be 8 ohm is if you are only running 2 speakers. Thus, the magic dust!!!

 

[longfxukxnhair]

Its says right in the Mesa Road King manual that you can do a safe mismatch.

What the hell? Now I am confused.

Have fun with that.

I'll stick with matching, you guys can do math and roll dice.

I didnt say I was doing this. Just that the Mesa manual said that you can. Seems to me if you follow their instructions (that they have provided in writing) that they would be liable for any damage?

 

[chunktone]

Dude, doesn't work. Please explain how 4 16 ohm speakers can be wired for 8 ohm. If you wire them all in parallel, you get a 4 ohm cab. Series/parallel will make a 16 ohm cab. The only way it can be 8 ohm is if you are only running 2 speakers. Thus, the magic dust!!!

A 4x12 with 16 ohm speakers can be wired parallel for 16 4 ohms, series for 64 ohms, or series parallel for 16 ohms. You can't run all 4 and have 8 ohms if the speakers are 16 ohms.

 

[Buckeyedog]

Dude, doesn't work. Please explain how 4 16 ohm speakers can be wired for 8 ohm. If you wire them all in parallel, you get a 4 ohm cab. Series/parallel will make a 16 ohm cab. The only way it can be 8 ohm is if you are only running 2 speakers. Thus, the magic dust!!!

A 4x12 with 16 ohm speakers can be wired parallel for 16 4 ohms, series for 64 ohms, or series parallel for 16 ohms. You can't run all 4 and have 8 ohms if the speakers are 16 ohms.

Exactly right. I was asking Maddnotez this question because he said he has an 8 ohm cab that contains 4 16 ohm speakers.

 

[cardinal]

He's using another resistor to get the overall ohm rating where he wants it.

 

[sytharnia1560]

I believe it is called parallel wiring. No magic dust needed.

http://www.uncleikes.com/t-how-to-wire- ... r-cab.aspx

nothing in this link shows a way to get 8ohms from 4 16ohm speakers ... please point out your point

 

[ke2]

You need some kind of resistor to do it. I know Hartke makes a cab (Hydrive 112) that can be run at both 4 and 8 ohms

"Expanding on the already inclusive line of HyDrive bass cabinets, Hartke introduces the HyDrive 112, a specially tuned, ported bass cabinet that employs a single 12" neodymium hybrid cone speaker. And to make the HyDrive 112 more accommodating for a variety of settings and playing styles, the speaker has been engineered as a dual-impedance driver, allowing you to switch between 4 and 8 ohm impedances for additional flexibility."

But apart from that, I haven't seen any readily available standard speakers like this. And there no point. Most normal speakers are available in 8 and 16, and most amps that are designed for bigger cabs, have impedance selectors, to be able to get full power from the amp in either 4, 8 or 16 ohms.

 

[maddnotez]

I believe it is called parallel wiring. No magic dust needed.

http://www.uncleikes.com/t-how-to-wire- ... r-cab.aspx

nothing in this link shows a way to get 8ohms from 4 16ohm speakers ... please point out your point

It's diagram #2 idk how you can't see it.

In the diagram it uses two 8ohm speakers to equal 4 ohms. The same principle applies to 4 speakers.

I did it. I have four 16 ohm speakers wired to 8 ohms and have a multimeter that verifies it's 8 ohms total.


Parallel wiring each speaker load is cut in half. So for the two 8 ohm speakers,
the total load now becomes 4 ohms. This is again quite easy when dealing with
speakers of the same impedance, but becomes a challenge when working with different
impedance loads. This and the problem of the number of speakers that be connected before
the impedance becomes too low are the biggest drawbacks of parallel wiring.
However, it is still by far the preferred method due to the reliability and sound quality.
Most Pa cabinets offer a parallel jack on the back for connecting a 2nd speaker to the line.
These jacks are in parallel to each other.


In this example the two 8 ohm speakers are now a 4 ohm total impedance .

 

[russoloco]

The diagram shows TWO 16 ohm speakers wired in parallel to get 8 ohms for a left channel AND TWO for a right channel. 4-16 ohm speakers CAN NOT be wired to get 8 ohms for ALL 4 speakers, that is not possible. As far as impedance mismatching it is fine for most guitar amps unless the OT is a piece of crap and you crank the amp. You will have some bandwidth and power loss that is all. In fact, JBL relabeled all of their 16 ohm speakers back in 70's to 8 ohms (or visa versa) to accommodate solid state devices and the tube amps didn't care.

 

[dfrattaroli]

If you look down the page a bit you'll see a diagram where Mesa shows you can run not just one mismatch but two at the same time. Pretty sure they know a thing or three about this topic.

http://mesaboogie.com/news/2013/06/mesa ... up-part-1/

 

[maddnotez]

The diagram shows TWO 16 ohm speakers wired in parallel to get 8 ohms for a left channel AND TWO for a right channel. 4-16 ohm speakers CAN NOT be wired to get 8 ohms for ALL 4 speakers, that is not possible. As far as impedance mismatching it is fine for most guitar amps unless the OT is a piece of crap and you crank the amp. You will have some bandwidth and power loss that is all. In fact, JBL relabeled all of their 16 ohm speakers back in 70's to 8 ohms (or visa versa) to accommodate solid state devices and the tube amps didn't care.

You may be looking at the wrong diagram.

Diagram #2 does not show 16 ohm speakers.

I copied the verbiage in my last post that shows they are showing an example of cutting two 8 ohm speakers into 4 ohm loads. Cutting them in half. Not sure where you got the diagram with the 16 ohm speakers from. It is not what I am looking at.

It is absolutely possible, if you disagree you should try it yourself and see.

Here is the verbiage again:

Parallel wiring each speaker load is cut in half. So for the two 8 ohm speakers,
the total load now becomes 4 ohms. This is again quite easy when dealing with
speakers of the same impedance, but becomes a challenge when working with different
impedance loads. This and the problem of the number of speakers that be connected before
the impedance becomes too low are the biggest drawbacks of parallel wiring.
However, it is still by far the preferred method due to the reliability and sound quality.
Most Pa cabinets offer a parallel jack on the back for connecting a 2nd speaker to the line.
These jacks are in parallel to each other.


In this example the two 8 ohm speakers are now a 4 ohm total impedance .

This example shows how to get a 2x12 cab with 8 ohm speakers to a 4 ohm load. The same principles apply to a 4x12, 8x12, 704x12, ect. I am not a scientist but I know this because I did it. I followed the diagram and ended up with 8 ohms out of 4 16 ohm speakers.

If you do not beleive me that is fine but it is very possible and if you try it for yourself you will see.

 

[sytharnia1560]

I believe it is called parallel wiring. No magic dust needed.

http://www.uncleikes.com/t-how-to-wire- ... r-cab.aspx

nothing in this link shows a way to get 8ohms from 4 16ohm speakers ... please point out your point

It's diagram #2 idk how you can't see it.

In the diagram it uses two 8ohm speakers to equal 4 ohms. The same principle applies to 4 speakers.

no it doesn't. 4 16 ohm speakers wired in parallel will give you 4ohms, series/parallel will give 16ohms. Can you link any wiring diagram that shows 4 16ohm speakers totally 8 ohms ... just one link please

the only way you get 8ohms from a quad of 16ohms is if its wired stereo

 

[Buckeyedog]

I believe it is called parallel wiring. No magic dust needed.

http://www.uncleikes.com/t-how-to-wire- ... r-cab.aspx

nothing in this link shows a way to get 8ohms from 4 16ohm speakers ... please point out your point

It's diagram #2 idk how you can't see it.

In the diagram it uses two 8ohm speakers to equal 4 ohms. The same principle applies to 4 speakers.

no it doesn't. 4 16 ohm speakers wired in parallel will give you 4ohms, series/parallel will give 16ohms. Can you link any wiring diagram that shows 4 16ohm speakers totally 8 ohms ... just one link please

the only way you get 8ohms from a quad of 16ohms is if its wired stereo

This! You (Maddnotez) are talking TWO 8 ohm speakers run in parallel makes a 4 ohm load. That is correct! HOWEVER, you can't then say FOUR 8 ohm speakers (or 8 or 10 or 50) run in parallel also makes ONE 4 ohm load. The math doesn't work.

You have TWO 8 ohm speakers that make ONE 4 ohm load. Then another TWO speakers would make another ONE 4 ohm load. Those TWO 4 ohm loads now have to be connected to make all 4 speakers work. So you run those in parallel, you get a 2 ohm load. Run those in series and get a 16 ohm load.

Now move to 16 ohm speakers. You have TWO 16 ohm speakers run in parallel makes ONE 8 Ohm load. The other TWO speakers in a 4x12 would then also make ONE 8 ohm load. Those TWO 8 ohm loads need to be connected to make all 4 speakers work. Run those in parallel, you get an overall total of 4 ohms. Run those in series and you get a 16 Ohm load.

If your cab does have an overall 8 Ohm reading, then either you have 8 ohm speakers or only 2 speakers are working. Unless like the guys say above, you have added some resistors or something, it's just not possible. Please check it out. I want to make sure your cab is functioning properly.

 

[russoloco]

Also, you can't just take a resistive measurement of speakers with a simple multimeter. You'll need one that measures inductance and even then inductance is totally frequency dependent. Yes 2-8 ohm speakers in parallel will get you 4 ohms. But you can't get 4-8 ohm speakers to give you a 4 ohm load. It's just not possible. The same math applies. With 4-8 ohm speakers you can make a 32ohm load, an 8 ohm load or a 2 ohm load if all 4 speakers are used. Not much else is possible.

 

[Buckeyedog]

Let's go another direction. The formula is R=1/(1/R1+1/R2+1/R3+1/R4)

So we have R=1/(1/16+1/16+1/16+1/16)

Now R = 1/(4/16) or R = 1/(1/4) or R = 1/.25 which is R = 4 Ohm load.

If you add more speakers to the mix, the overall load becomes lower and lower. It does not remain constant!

 

[maddnotez]

Well I'm glad this has came up. A million chinese people can't be wrong. I'm gonna open my cab up tomorrow and check it out. I'm pretty sure that's the diagram that I used and ended up with 8ohms. The meter I have had an ohm setting. I may have used the wrong word and it's an ohm meter. How can that not give an accurate reading? Isn't that what it is for: measuring ohms?

 

[Buckeyedog]

Well I'm glad this has came up. A million chinese people can't be wrong. I'm gonna open my cab up tomorrow and check it out. I'm pretty sure that's the diagram that I used and ended up with 8ohms. The meter I have had an ohm setting. I may have used the wrong word and it's an ohm meter. How can that not give an accurate reading? Isn't that what it is for: measuring ohms?

Cool man, and let us know! Did you check it at the jack? Plug in a speaker cable and then go tip to sleeve with your mutimeter. It won't be exactly 16 or 4 ohm, but it should be somewhat close.

 

[sytharnia1560]

Well I'm glad this has came up. A million chinese people can't be wrong. I'm gonna open my cab up tomorrow and check it out. I'm pretty sure that's the diagram that I used and ended up with 8ohms. The meter I have had an ohm setting. I may have used the wrong word and it's an ohm meter. How can that not give an accurate reading? Isn't that what it is for: measuring ohms?

they may not read exact numbers, it really depends on the meter .... from memory 8ohms might read between 6 and 7, 16ohms might be 13 to 14

 

[Buckeyedog]

Well I'm glad this has came up. A million chinese people can't be wrong. I'm gonna open my cab up tomorrow and check it out. I'm pretty sure that's the diagram that I used and ended up with 8ohms. The meter I have had an ohm setting. I may have used the wrong word and it's an ohm meter. How can that not give an accurate reading? Isn't that what it is for: measuring ohms?

they may not read exact numbers, it really depends on the meter .... from memory 8ohms might read between 6 and 7, 16ohms might be 13 to 14

Pretty sure this is right on.

 

[maddnotez]

Ok I am prepared for my Rig-Talk beatings. Ty guys for proving me wrong.

I'm guessing my ohm meter was bad. I checked with my friends and indeed was reading 13ohms which means 16 for the amp.

Not happy about it but at least I was running the amp lower than the cab and not the other way around.