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Old 22nd March 2012, 04:24 PM   #1
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Default How to use 1 Bass Amp and 2 Cabinets

I have Mark Bass III head which is 500 Watt/4 Ohm or 300 Watt/8 Ohm.
1) Can I use the head with two (separate) 300 Watt/8 Ohm cabinets? If I can, How Do I connect from head to the two cabinets?

Is it like

Head -> Cab1 -> Cab2 ?
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Old 22nd March 2012, 04:46 PM   #2
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500 Watt/4 output from the amp -> cab 1-> cab 1 ----- bear in mind that the two cabs must be in parallel to get 4 ohm load. Are there two 4 ohm jacks on the back of the amp? If so run a speaker cable from each jack to each speaker. Alternatly are there two speaker jacks on either cab? If so then come off the 4 ohm output from the amp to one cab then out the second jack of that cab to the other cab. With either configuration you will be wired for 4 ohm load on the amp. I looked for a picture of the rear of the amp but dident find one. If in doubt take a picture of the rear panel and post it. Make sence?
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Old 22nd March 2012, 05:16 PM   #3
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...and if you do only have 1 output, and each cab only has 1 jack, then build a parallel jack box. I recently made one for exactly the same reason. I have 4 cabs I wanted to do some mix and matching with, not all have 2 jacks, my amp only has 1 output. Just make sure you use heavy wires between the jacks.
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Old 22nd March 2012, 05:42 PM   #4
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What cabs are you running the amp into?

Some cabs are wired for
- serial (two speaker loads in a row),
- parallel (two speaker loads connected both at input and at ground),
- some allow for both.

If we know what cabs you are trying to drive, the answer could be more thorough and accurate.

Sometimes just a snapshot of what's printed on the cab where the jacks are would make the best connection clearer. You don't want improper connection to damage the amp or blow it up, best to be sure.

Do note that according to the manual I checked out online, 4 ohms is the minimum recommended load - so if by chance you are running 2x 4 ohm amps in parallel unintentionally, that's a 2 ohm load and exactly what you don't want.
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Old 24th March 2012, 01:25 PM   #5
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Click the image to open in full size.Thank all for response to my question.
My goal is to connect the Amp to 2 cabinets in parallel so that it can push 500 watts. is 500 watts louder than 300 watts?

1) My current cab has only one input jack
2) The MK III Head has only one output (I think). There are two jack but one is 1/4" and another is speakon jack. Please see attachment which show the rear view of the MK III
3) I am planning to build another 300 watts cabinet. Can I build this cabinet with two parallel jacks? One jack input from the head and another is for connection to the next cabinet.

Could you provide the instruction to build the Parallel Jack box. I would like to learn.

Last edited by BuildByHands; 24th March 2012 at 01:30 PM. Reason: want to attach a file. How?
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Old 24th March 2012, 01:54 PM   #6
sreten is online now sreten  United Kingdom
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Hi,

If you do 3) you don't need the parallel box.

rgds, sreten.
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Old 24th March 2012, 01:58 PM   #7
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Here ya go,

Click the image to open in full size.

That is assuming 4 8 ohm speakers. What do you plan to build?

As for 500 watts being louder than 300 watts, yes it will be, but how much louder remains to be seen. Don't expect it to be almost twice as loud. With two cabs it will certainly be more full sounding, and probably more powerful feeling, but actual dB increase, can't really say.
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Last edited by doozerdave; 24th March 2012 at 02:01 PM.
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Old 24th March 2012, 02:36 PM   #8
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Quote:
Originally Posted by doozerdave View Post
Here ya go,

Click the image to open in full size.

That is assuming 4 8 ohm speakers. What do you plan to build?

As for 500 watts being louder than 300 watts, yes it will be, but how much louder remains to be seen. Don't expect it to be almost twice as loud. With two cabs it will certainly be more full sounding, and probably more powerful feeling, but actual dB increase, can't really say.
If you've got two cab's like you've just drawn above, adding the second one will make it a LOT louder - and stacking them close together will give enhanced lower frequencies as well.

It's not just a question of almost twice the power, but you've also got twice the cone area pumping air - it won't be 'twice as loud', but it will be VERY worthwhile
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Old 27th March 2012, 01:14 AM   #9
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TalkBass.com - Bass Guitar and Double Bass Forums: Basses, Amps, Strings, Effects here is the answer to all the questions you will ever have on this topic....just keep a few things in mind:
1. you will rarely find a bass amp that will not operate below 8 ohms.
2. when you want more power, try more speakers first. (provided you stay at or above the amp's minimum ohm load)
3. watts doesn't mean much (really). an inefficient speaker can make your 500 watt amp sound like a 100 watt amp, and a highly efficient speaker can peel off your face with 100 watts.
4. most speakers will mechanically fail if you put the rated power into them. the watt rating on the speakers is a thermal rating, not the point at which you do damage to the cone. a safe rule of thumb for bass cabs is about half to 2/3 rated power. (there are exceptions, but few. see: fEARFUL)
5. vertically stack cabs, don't set them next to each other, and don't "bookend" the backline with them.
6. keep your driver size the same. if you have a 2x10 and want to add another speaker cab, use another 2x10. same with a 1x15, 4x10, 2x12, etc.
7. driver size has nothing to do with frequency response or tone. only the actual driver's specs and the cabinet design affect these.
8. never never never use anything but a purpose-built bass driver for bass guitar. subs and consumer-grade drivers just don't work well enough. (pa cabs are ok, but they're loaded with purpose-built pro drivers)
9. bass cabs are not like guitar cabs. they need to be properly designed to the driver that is in them. if you just build a box and throw in some speakers, you're more likely to be disappointed than thrilled with the results.
10. don't fall victim to GAS. (look it up). do your research, lurk talkbass for a while, save up and buy the right gear for you, the first time. then you can concentrate on playing and improving your skills and repitoire.

i wish i could read this post 15 years ago.......

as far as the OP, why not just buy a speakon to 1/4" cable? you hook up one 8 ohm cab to the standard 1/4" output, and another 8 ohm cab to the speakon output. done.
these two outputs on the amp will be parallel. most pro audio gear will be this way. if you do start getting into diy, please please please learn about ohms law! you'll be saving alot of time and money if you do.
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Old 27th March 2012, 02:13 PM   #10
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Not to get overly techie - but hey, why not? Here is my personal understanding of how these things work and and some factoids:

- All else being equal (read, speaker efficiency and frequency response), a doubling of wattage (i.e. 100 watts --> 200 watts) yields a +3db volume increase.

- To the human ear, all else being equal, if 'sound B' is 9-10dB louder than "sound A," than sound B will be perceived as 'twice as loud' as sound A. Or, in simple terms, to double perceive volume, you need a 10db increase in volume.

- To the human ear, all else being equal, if sound A is raised in volume, an inccrease of 3dB is the first point that the average person will say they 'perceived' the volume has increased. If you see the former point, than this only makes sense in light of volume being perceived on an exponential scale to the ear (just like frequencies are). To the OP, trying to work out speaker loads that will result in either 500W vs 300W maximum output power, if what I'm saying is true,, 300W of power will only be ~ -2dB loss of volume, may just be at the threshold of perceptable loss of volume, all else being equal (but in this case, invarable all else will not be equal!)

- If you do the math, If your current wattage is A, than you need 2x the wattage to get a noticeable increase in volume, and you need 8x wattage of A to get twice the perceived volume, all else being equal!

- Manufacturers of amps do not and are not required to follow any 'black line' standards for their published output power ratings. This comes up a lot with tube amps. Output power is often (or at least should be) published as a specified THD% or distortion. Tube amps can often sound clean to the ear with 5% THD, and there may be significant different in output power an amp can deliver with 5% THD and .1% THD. The increase in THD from that point is also slow and gradual (7%, 10%, 15% THD) with most tube power amps, where as with much traditional solid-state equipment (not sure about mosfet power amps or class D), I'm told things quickly transition from maximum and very clean output power to full-on clipping. This is often said to be one reason why people historically perceive that a tube amp with the same 'wattage' as solid state amp might sound 'louder' and still perceived as clean when the solid state amp is clipping and/or not as loud.

- speaker loads connected in parallel, and speaker loads connected in series, all else being equal often have a perceived difference in tonal response.

- Connecting speakers in parallel is often done in hi-fi equipment as it more or less 'smooths over' the inherent frequency resonances and dead spots of each individual speaker, in attempt to get the most 'linear' response possible from the speakers used. Hence, this is often the proffered method of connecting 2 or more speakers in something like a home-stereo, where the ideal is the most linear response to frequency over the audio frequency range (sorta similar to adding negative feedback in circuitry).

- Connecting speakers in series more or less lets each individual speaker's 'quirks' of frequency resonances and response be the most emphasized or noticeable; this is much the opposite of the above description of connecting speakers in parallel.

Do note the repeated use of the phrase 'all else being equal.' Sound is subjective, and isolating every variable (the ears listening, the room, the frequency, the speakers, the amplifiers, the voltage at the wall etc) is all but impossible. So these are inherent references and generalities.

Hope this info is helpful, and if anyone has superior info, please offer it! Additional info about speakers (and the source of some of the info typed above), though mostly from a guitarist context, is available here: Let's Talk Speakers
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