Ohms FAQ

[B-string]

One important point to remember if you run cabs in series (special cable needed in most all cases) and one cab fails you will no longer have any sound. Running Parallel if one cab fails you can continue playing the one good cab (disconnect the failed cab as soon as you can).

 

[David Jayne]

Thanks.

I only want to use one cab on my rig, two 410 is too much, so I want to make sure I make the right choice with the 8 or 4 ohm cab so I can have as much volume as possible with just that one cab.

So, much difference between those two cabs?

Careful. You can kill that cab pretty easily with a DB750, either version. So I suggest you get the 8ohm version, in case you discover one isn't enough after all.

 

[B-string]

People may be confused about cab impedance thinking it changes the power the cab can handle maybe? If the cab is rated to take 800 watts but will only handle 400 cleanly, increasing the input power by "getting all the watts" (power) from the amp will NOT make it louder. The extra power will only be dissipated as waste heat and distortion. Counter productive and dangerous to speakers.

 

[Munjibunga]

You might want to put "hybrid amps" in your glossary to make a distinction between them and pure solid state amps.

 

[Munjibunga]

Thanks. Definitely backwards on that. Too much info bouncing around from all this research.
The amp in question is a hybrid. Eden WT300 Traveller solid state with a tube pre amp.
So, is it safer to run parallel making sure to keep it below the distortion level or run in series thereby lowering the wattage output of the amp?

Series rarely makes sense, and surely doesn't make sense in this case. Yes, run parallel and be happy!

It's not a simple matter to run cabs in series anyway. You need a special cable or box to put them in series. Many people make the mistake of believing that "daisy chaining" cabs is putting them in series when, in fact, that's topologically identical to running one cab from each output of a monaural amp.

 

[B-string]

The trouble with "hybrid" amps is there are some like MusicMan that have a SS preamp and a tube output. Most are tube pre with a SS output but not all.

 

[airborne_jeff]

I wanted to make sure that my thought process was correct in this and since I saw this thread was up I wanted to ask it. I am running an HA2500 currently. The head has dual outputs and is rated for 250 Watt@4 Ohm and 180 watt @8 Ohm. I am currently running a GK 115 (max 225 watt @ 8 ohm) , and was thinking of adding a 2x10 cab at 8 Ohms to it. From everything I have read, and everything I saw in this thread, that would mean the both cabs hooked up individually through the dual outputs would put the head to the 250 watt @4 Ohm setting. Each output effectively @125 watts.
Thanks in Advance

Jeffrey

 

[B-string]

Basically. The two "outputs" are not independent they are connected to the same point inside the amp head. When you hook up two 8 ohm cabs they MAKE a 4 ohm load for the amp head. The cabs will share the 250 watts, the amp connection does not "decide" anything. Get a second like 115 and you will be happier.

 

[airborne_jeff]

Probably a silly question, but why not a 2x10? I thought that the consensus for mid's and low end combination 2x10 and 115 were the way to go.

 

[B-string]

Probably a silly question, but why not a 2x10? I thought that the consensus for mid's and low end combination 2x10 and 115 were the way to go.

That is the myth not actual fact.
A 210 can be deeper and have less midrange than a 115. It all depends on the individual speakers and the box built for them. Size of the driver means very little until you start mixing driver sizes without being crossed over. If you stack them in vertical alignment they should play well with each other, but looks odd on stage. Matching cabs works much better, twice as much of what you like and controllable.

Not a silly question

 

[David Jayne]

I wanted to make sure that my thought process was correct in this and since I saw this thread was up I wanted to ask it. I am running an HA2500 currently. The head has dual outputs and is rated for 250 Watt@4 Ohm and 180 watt @8 Ohm. I am currently running a GK 115 (max 225 watt @ 8 ohm) , and was thinking of adding a 2x10 cab at 8 Ohms to it. From everything I have read, and everything I saw in this thread, that would mean the both cabs hooked up individually through the dual outputs would put the head to the 250 watt @4 Ohm setting. Each output effectively @125 watts.
Thanks in Advance

Jeffrey

You are correct about the output power/Ohms bit. But be aware that even though the amp has two speaker jacks, the amp is mono and those jacks are wired to the same place. For convenience only.
2x10 + 115 is not recommended. If you like your tone now but want more of it, get a second identical 115.

 

[musicman666]

^IME Matching drivers sounds much better than mis-matched drivers. To my ears mixed driver sizes can be very difficult to EQ properly and they don't reinforce each other like a matched set of drivers.

 

[acmebass]

thanks for the post!

You mentioned about different cab ratings,
what happens when you plug say, a 4ohm cab together with an 8 ohm cab, do they draw power evenly?
Tombowlus?

Power into each cab will be equal to V2​/Z,

Where V = voltage, and
Z = impedance

Therefore, the 4 ohm cab will receive twice the power of the 8 ohm cab.

Consequently, connecting a 4 ohm 2x10 in parallel with an 8 ohm 2x10 will be "incorrect," because the woofers in the 4 ohm cab will each receive twice the power of the woofers in the 8 ohm cab.

Connecting a 4 ohm 4x10 cab in parallel with an 8 ohm 2x10 will be correct, because the power will be distributed evenly between the 6 woofers.

The resulting load will be 2.67 ohms.

 

[ThisBass]

Power into each cab will be equal to V2​/Z,

Where V = voltage, and
Z = impedance

Therefore, the 4 ohm cab will receive twice the power of the 8 ohm cab.

Consequently, connecting a 4 ohm 2x10 in parallel with an 8 ohm 2x10 will be "incorrect," because the woofers in the 4 ohm cab will each receive twice the power of the woofers in the 8 ohm cab.

Connecting a 4 ohm 4x10 cab in parallel with an 8 ohm 2x10 will be correct, because the power will be distributed evenly between the 6 woofers.

The resulting load will be 2.67 ohms.

Yes and no!

There are three speakers in total. Probably each speaker is of 8 Ohm nominal.
The conclusion is that each speaker receives the same voltage.

The equation
V2​/Z
equals to all of the three speakers.

A 15" speaker comes with extended cone surface area in opposite to 10s and therefore an increased efficiency and increased bottom. So the 15s sound is more to the front in the mix of 15+10+10.

Any different "theoretical" conclusion would mean that the combination of 110+210 plays louder then 15+210.
Or 110+110+210 plays louder then 215+210.
Or 110+110+110+210 plays louder then 215+115+210.
Or 610 plays louder then 215+215+210

I cant imagine how a 610 stack would accomplish to beat a wall of 415+210

If the 210 is louder and deeper then a 115 means compellingly that a stack of 810 is deeper and louder then a stack of 2x215.
Shall that be the truth of math on world wide known TB ?

 

[B-string]

Yes and no!

There are three speakers in total. Probably each speaker is of 8 Ohm nominal.
The conclusion is that each speaker receives the same voltage.

The equation
V2​/Z
equals to all of the three speakers.

A 15" speaker comes with extended cone surface area in opposite to 10s and therefore an increased efficiency and increased bottom. So the 15s sound is more to the front in the mix of 15+10+10.

Any different "theoretical" conclusion would mean that the combination of 110+210 plays louder then 15+210.
Or 110+110+210 plays louder then 215+210.
Or 110+110+110+210 plays louder then 215+115+210.
Or 610 plays louder then 215+215+210

I cant imagine how a 610 stack would accomplish to beat a wall of 415+210

Completely WRONG! If the 15" has a high Fs and short Xmax it will produce LESS low end than a low Fs and high Xmax 10".

 

[airborne_jeff]

This is why I like this place, good food for thought. Maybe I will just sell everything, and get a fearful and have it all...

 

[ThisBass]

The resulting load will be 2.67 ohms.

In general (mostly) to all of us bass players the total of ohms is significant above the nominal.
Sometimes a bit less greater, sometimes a little bit more greater but in general the average ohms is above the nominal.

So I point out that the mixing of 8 ohm and 4 ohm in parallel is in "average" total something >3ohm

Average does not mean the average of cabs.
Average means the average of impedance curve related to the average frequency spectrum of the instrument.

As an example
Load impedance to the amp is significant increased if bass bands at EQ are gained significantly.
Load impedance to the amp is significant increased if low mids at EQ settings are significant scooped.

Impedance of a cab isnt something like a constant number to the amp at all times.
depending on sound settimgs and the frequency spectrum of the instrument the amp sees a lot of different impedance values.
In general the "average" impedance is above the nominal!

2.67 Ohm?
Yes, on the display of a computer machine!

Don't get me wrong but the calculation (rather estimation) of load impedance is one of the most misunderstood points of amp technique at all forums all over the world.
So I do declare this party opened!

 

[acmebass]

Yes and no!

There are three speakers in total. Probably each speaker is of 8 Ohm nominal.
The conclusion is that each speaker receives the same voltage.

Nope. I was referring to two 2x10 cabs. That's four drivers, not two.

An 8 ohm 2x10 does not have 8 ohm drivers in it. It can be done with two 4 ohm drivers, or two 16 ohm drivers, but it's impossible to wire two eight ohm drivers in such a way as to get a resulting impedance of eight ohms.

I wish you were right...

The rest of your post is extremely generalized, and makes no sense to me.

Thanks,
Andy

 

[KJung]

Yes and no!

There are three speakers in total. Probably each speaker is of 8 Ohm nominal.
The conclusion is that each speaker receives the same voltage.

The equation
V2​/Z
equals to all of the three speakers.

A 15" speaker comes with extended cone surface area in opposite to 10s and therefore an increased efficiency and increased bottom. So the 15s sound is more to the front in the mix of 15+10+10.

Any different "theoretical" conclusion would mean that the combination of 110+210 plays louder then 15+210.
Or 110+110+210 plays louder then 215+210.
Or 110+110+110+210 plays louder then 215+115+210.
Or 610 plays louder then 215+215+210

I cant imagine how a 610 stack would accomplish to beat a wall of 415+210

If the 210 is louder and deeper then a 115 means compellingly that a stack of 810 is deeper and louder then a stack of 2x215.
Shall that be the truth of math on world wide known TB ?

You are a bit confused here Cone diameter is one of the least important features of a driver when discussing power handling, low end extension, etc. Yes, all other things being equal (which they never are), a 15" driver will have higher sensitivity than an otherwise identically spec'd 10" driver (I think anyway), but that is a separate issue.

 

[ThisBass]

Completely WRONG! If the 15" has a high Fs and short Xmax it will produce LESS low end than a low Fs and high Xmax 10".

If you compare apples to beans you are right.
But if you compare apples to apples you are wrong.

If I'd try to compare home theater speakers to PA speakers I would do a very bad mistake.

If I'd compare similar designed speakers so I don't feel I would do something wrong because I'm trying to compare apples to apples.

It's very often figured that a 210 is better at the lows then a 15. And even a 210 plays louder then a 15.
Refering to different speaker designs this argument may be true, but that is not a valid point that should be discussed.

There are a very lot of different speakers availible at the market with very different specs for very different design goals and tastes and applications at very different sale prices.

So comparing apples to apples is not as easy as it very often looks like!

Nearly every high performance 15 speaker knocks off a 210 of same speaker series if the cab is well designed.