Newbie cab ohms question

[flateric]

I have a mix of bass cabs for gigging, wanting to use one to shove behind the drummer to help him keep time,
1. 400W 4 x 10 Hartke cab, 8 ohm
2. 200W 1 x 15 Hartke cab, 8 ohm
3. 250W 2x10 + horn Hartke cab, 8 ohm

I'm using a Peavey Tour 450 head which runs about 300W at 8 ohm and 450W at 4 ohm.

So if I run the 1 x 15 and the 2 x 10 in series to give 16 ohm, then run the 4 x 10 in parallel, this should give 5.333 ohm load which will not damage the amp, is that correct?

Are the lower power rating cabs the best ones to run in series together? How would I need to change the speaker wiring since
the rear panel facillitiates only chaining speakers in parallel, not series?

[newey]

flateric-

Neither you nor this question are newbies- you've been around and we've had similar discussions before.

I think you're on the right track with the idea to run the 2 lower-wattage cabs in series with the other in parallel.

I assume the Peavey is solid-state, no? Does it have separate speaker jacks for 8Ω and 4Ω? If the 4Ω is a separate jack, you'd want to use that one to run a 5.33Ω load, it's always better to run a larger load than one too small.

Although the Peavey, if it's SS, probably won't care too much what you do to it so long as some load is hooked up!

I'll see what I can dig up from the archives on this. IIRC, JohnH had a nifty idea for using a switched jack for series/parallel cab connections.

[flateric]

You are right, I have been around for a bit, but I love to check with you guys first before I do something stupid The peavey is solid state, it has 2 identical speaker outputs on the back, to run 2 cabs in parallel.
The Hartke cabs have 2 jack sockets on the rear panel to daisychain to another cab in parallel - for the 2 cabs I want to run in series I guess a small mod to the wiring will facilitate this, plus the use of a shorted jackplug at the end of the signal chain to complete the circuit.

[flateric]

Proposed setup:

[flateric]

If I have my wiring correct, a simple 3PDT switch installed in the rear speaker jack panel should allow the cab to be switched between parallel and series.

[JohnH]

Hi flateric - I think your arrangement is OK and your switch seems right. Your ss amp is happy with any load with more than 4 Ohms. The main problem that might be evident is that 2/3 of the power will come through the 4x10, and only 1/6 through each of the others. Hence the output from the secondary cabs may be too low to be useful. Id suggest a temporary wire-up to check first, before committing to installing the switch.

Also, to save changing the cabs (which might harm resale value), you could do this with a simple hardwired box with an input socket and three outputs. (we know you like making small boxes!)

John

[flateric]

eminently sensible suggestion as ever sir John,


this would avoid any internal cabinet tinkering but i suspect i will get an unacceptable power drop off when running all 3 cabs at same time.

[sumgai]

♭eric,

John's assertion about power delivery to each speaker is correct, but there's a 'gotcha' in the pudding - it assumes a commensurate drop in perceived level coming out of the speaker, but that's true only if all three speaker cabs have the same SPL ratings. IOW, if one of the three cabs has an SPL rating of just 3dB more than the others, it will sound appreciably louder for the same power input.

Now, that being said, I'd look to see if one of the cabs is stronger than the others. If not, then proceed as planned. If there is a stronger cab, then you might want to place that one behind the drummer. (Although I wouldn't place a 10" anything behind him, I'd place a #10 boot right where it'd do some good.)

If all three seem to sound about the same loudness, and if you're concerned that the drummer must have as much 'power' as you can safely deliver, then try this: split the wiring in the 4-speaker cab. That box has 4 8Ω units, wired in series-parallel. Break them apart so that you have a stereo box of two 4Ω halves. Now go out and hook up each half in series with one of the 8Ω boxes. That gives you 12Ω, right? Put those two strings in parallel, and you'll have 6Ω worth of power draw, with equal output from each pairing.

Position on the stage as appropriate.

And if you're gonna insert a series/parallel switch into a box, use something rated for high current, like at least 10 amps, and more would be better. Otherwise, the switch will burn out its contacts all too soon. (Use Ohm's Law to determine how many amps will be flowing at maximum power delivery.)

HTH



sumgai

[ashcatlt]

You want to help the drummer keep time? Get a drum machine.

But seriously, whatever you do you must be sure to display the following logo prominently on the cab you stick near him:

Join Here

[sumgai]

^^^^^ +1,000!!!

[flateric]

I put together a quick little splitter box in the end to avoid rewiring the cabs.

Now we can look round for a metronome to buy the drummer

[Yew]

If you got several mechanical metronomes with drumsticks attached, you could make a drummer

[cynical1]

Jun 26, 2011 15:38:46 GMT -5 Yew said:

If you got several mechanical metronomes with drumsticks attached, you could make a drummer

I don't know...it's easier winding up the drummer then the metronomes...just toss him a 40 oz. Mickey's and he's wound for several hours...

HTC1

[ashcatlt]

I've been threatening to build a robot with our rack built in with AI drum part generation. It would be ethanol powered. We wouldn't have to carry anything but our guitars and just buy it Everclear shots every once in while.

[flateric]

I'm thinking of the money I could save on solder.

[cynical1]

Jun 26, 2011 16:21:40 GMT -5 ashcatlt said:

...and just buy it Everclear shots every once in while...

Just like a real drummer...