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Discussion in 'Amps and Cabs [BG]' started by PatO, Oct 3, 2010.
on the MarkBass LMII (or any other amp for that matter) are the speaker outs parallel or series?
Parallel. Example: if you hook up two 8 ohm enclosures, your amp will "see" a 4 ohm load.
next question: plugging 1 cab into another cab then into the amp = series?
Nope. Once again, this is a "daisy-chain" which maintains the parallel configuration.
Edit: This applies to the majority of components I've encountered. Always check your manual for specs. and installation instructions.
so there is really no way to attach multiple cabinets in series without some serious rewiring?
Why would you do that?
99 % of amps on the market have parallel outputs, because it's the only useful way to wire them.
When you put cabs in series, you decrease the output of the amp by raising impedance.
Generally the two inputs commonly found on most cabs are wired in parallel.
Which cabs do you have, what are their impedances, how do you wish to connect them, and why?
I wouldn't, I am just slowly starting to understand the math involved in amp/cab pairings and power ratings.
Thank you for all the answers Talkbass. I think I have all the correct numbers on my little cheat sheet now. Next move is going to be framing this page of info and putting it on my wall.
Have you browsed through this sticky yet?
AMPS FAQ!! Info on OHMS, Allsize RIGS-OverUnderPowerCabs DIY TechTalk-Links
yeah I have. It's pretty intimidating, but I still go through there almost everyday and fact check myself
Fill us in on the big picture, please. What enclosures are you planning to pair with the LM II?
the big picture is mainly me trying to figure out the cause/effect in terms of power and sound when using different cab configurations.
I have two bag end cabs each rated at 8 ohms and am currently borrowing an aguilar also rated at 8 ohms. The LMII sends 300w at 8ohm and 500 at 4ohm.
so my understanding is that when using 1 cab, I'm pushing 300w at 8ohms into it. When using 2 cab (wired parallel out of the amp) I'm using 500w at 4 ohms. When using all three cabs (with the Bag Ends daisy chained) I'd get 375w at 5.33ohm.
the formulas I have for figuring these out are:
Power Output = amp rated power x (ohm rating / ohm load)
Total ohm load = (cab1 ohm x cab2 ohm)/(cab1 ohm+cab2 ohm)
provided I'm right in the above statements, the last thing for me to figure out is how the power is distributed among the cabs.
You CANNOT use all 3 together !
Daisy chaining the cabs is still running in parallel.
All 3 cabs together is a 2.67 ohm load.
so putting the two bag ends into 1 speaker out on the amp is not making the ohm load into the amp 16? it stays an 8 ohm load even though 2 cabs both rated at 8 are going into the same output?
Yup... remember the earlier posts? All those combinations of hooking up cabs puts them in parallel, nothing in series.
2 8 ohm cabs hooked up = 4 ohms. 8x8/8+8=4. Add a third 8 ohm cab, you figure it as a 4 ohm load (1st 2 speakers) connected in parallel with the 8 ohm load (3rd speaker). 4x8/4+8 = 32/12 = 2.6666 ohm load, lower than your MB 4 ohm minimum load.
Alternate formula is 1/(1/x + 1/y + 1/z...) where x y and z are the impedences of the individual speakers. so you have 1/(1/8 + 1/8 + 1/8) = 1/(3/8) = 8/3 = 2.66666 ohms.
Never put a lower load on the amp than its rated for.
As far as how the power distributes, its the inverse of the impedence. 4 ohm speaker gets 2x the power an 8 ohm speaker would get. Since all 3 are 8 ohms, they'd all get an even split of the power (if you had an amp could go down to 2 ohms).
Yes, typically. Apply that to your figurin'
OP you can only use two 8 Ω cabs OR one 4 Ω cab with your MarkBass LMII.
That amp can't handle a speaker load below 4 ohms.
Neither............2 8 ohm cabs daisy chained off a single output is a 4 ohm load.
An easier option is to buy or build your own Series Y-cord adaptor like this:http://procablesnsound.com/items/speaker-cables/power-y-adapter-70001-detail.htm
Thanks a ton folks!
I will not be 3 cabbing the LMii, but I sure as hell have been and will continue to run all 3 with my Mesa M6 Carbine. Granted, 2 15's and a 12 is a little excessive in most situations. At least now I (pretty much) understand the math involved.
If anyone ever wonders why this is the best community for bass players, you folks have proved it this morning.