Jump to content
Why become a member? ×

Can anyone simplify second cab ohms?


Cat Burrito
 Share

Recommended Posts

I'm the least technical or science-y person I know and I am just about confusing myself further than ever now.

I have an Ampeg PF50t head (50w all tube into 4 or 8 ohm, apparently). I have been playing it into a cab from the same series, the PF115HE which is 450w RMS at 800w (typed as if I actually know what that means!).

Recently I have been wanting to add a second cab, particularly as I like the sound of 8x10 cabs and I picked up a PF410HLF, again from the same series.

There is one input out the back of the head but I know you can daisy chain between the two cabs. It certainly sounded good in the kitchen - loud too! Watching various videos on YouTube I am getting confused as to whether this could damage the amp in any way or is a good idea. Googling around it does rather seem like a 2x10 paired with a 4x10 would be a more obvious pairing than the 4x10 with a 1x15 but I was hoping someone could clarify in the simplest of terms whether I could damage any kit here or if it is fine as is. It certainly sounded good but I am an absolute rank amateur when it comes to the technical side of kit.

Thanks in anticipation.

Link to comment
Share on other sites

[quote name='markstuk' timestamp='1490109712' post='3262235']
8 + 8 equals 4 :-) you're fine
[/quote]

Thanks, I find your confidence reassuring - I don't need to get why, just that I am not going to damage anything. :)

Out of interest should the head be switched to 8 ohm or 4 ohm? I'm thinking it should be on 8.

Link to comment
Share on other sites

Think the mis-match by many is based on the speaker size and air movement rather than ohms.
Many agree that you keep speaker sizes all the same.
However i have been using all sorts of cabs over the years and my fav set up is a 1x15" cab witha 2x10" cab and you get a great balance of sound giving a clearer top end from the 10's that my 15 just doesn't have.

My advice is try the combination you fancy and if it sounds good to you then it works.
The theory of speaker size differences is irrelevant if it sounds good to you.

Have fun. A 4x10 is a beast of a cab tho.

Dave

Link to comment
Share on other sites

Thanks Dave. I have a picture of a bassist upstairs who is playing a 1x15 with 4x10 combination but had read the same re speaker size. I may yet switch the 1x15 for a 2x10 so I have the option of 2,4 or 6x10 depending on the venue but for now it works well.

I also emailed Ampeg's support service and they were almost but not quite as quick as Mark to reply.

Link to comment
Share on other sites

Here's how to work it out.

In parallel (which pretty much all amp outputs and daisy chain sockets on cabs are), you work it out like so. For two 8ohm cabs:

1 / (1/8 + 1/8) =
1 / (0.125 + 0.125) =
1 / 0.25 =
4

If wiring in series, then simply add them, i.e., 8 + 8 = 16.

Link to comment
Share on other sites

Part of the usual reason for not using a 4x10 and 1x15 together is that the 4x10 typically handles more power and is more sensitive (louder for a given amount of power). So with a high-powered head you can be feeding too much power to the 15" and not even hear it distort because the 4x10 is louder, and the 15" often ends up blown. With the PF50 this will be a non issue.
If you've already got the two cabs and they sound good together there is a case to be made for not overthinking things!

Edited by Beer of the Bass
Link to comment
Share on other sites

[quote name='Beer of the Bass' timestamp='1490133630' post='3262584']If you've already got the two cabs and they sound good together there is a case to be made for not overthinking things![/quote]

I'm all up for not overthinking things :)

(PS good post - I actually followed that!)

Link to comment
Share on other sites

What Ω are your cabs each?
You never said in the post & everyone's assuming that they're both 8Ω. If one is 8Ω & the other is 4Ω, then that makes 2.66Ω, which could damage your amp. If they're both 4Ω cabs, then that's gonna be a 2Ω load
Given the choice & if I liked the sound of the 1x15, I'd have went for a 2nd 1x15 & made a 2x15 rig (better dispersion than the 4x10). If you prefer the sound of the 4x10, then get a 2nd 4x10 if you need more.
A 2x10 in your set up means that 2 drivers are gonna be running twice as hard as the other 4 (this is if all cabs are 8Ω).
Your way around it is if you have a 4Ω 4x10 & an 8Ω 2x10, but your amp may not handle this.

Link to comment
Share on other sites

[quote name='xgsjx' timestamp='1490170100' post='3262717']
What Ω are your cabs each?
You never said in the post & everyone's assuming that they're both 8Ω. If one is 8Ω & the other is 4Ω, then that makes 2.66Ω, which could damage your amp. If they're both 4Ω cabs, then that's gonna be a 2Ω load
Given the choice & if I liked the sound of the 1x15, I'd have went for a 2nd 1x15 & made a 2x15 rig (better dispersion than the 4x10). If you prefer the sound of the 4x10, then get a 2nd 4x10 if you need more.
A 2x10 in your set up means that 2 drivers are gonna be running twice as hard as the other 4 (this is if all cabs are 8Ω).
Your way around it is if you have a 4Ω 4x10 & an 8Ω 2x10, but your amp may not handle this.
[/quote]

They're both 8 Ohm cabs - I checked on the Ampeg website before posting my first reply..

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...