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cabs, resistance, series and parallel


Al Heeley
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My current gig setup is a Peavey Tour 450 head which runs about 300W at 8 ohm and 450W at 4 ohm.
This powers a 400W 4x10 Hartke cab and a 200W 1 x 15 hartke cab.

Just bought a 250W Hartke VX 2x10 + horn from a basschat member which would be handy to position just behind the head of our drummer to help him keep time.

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 to these two, this should give total 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 panels of the Hartke cabs facillitiate only chaining speakers in parallel, not series?

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assuming your cabs are all 8ohms you have it right. There will be no problems with power handling with what you suggest.

The easiest way to rig up speakers in series is to wire up a special lead or adaptor box. Any competent repair shop should be able to do this. I don't know of any commercially available leads.

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This shows current standard parallel wiring at the back panel of the Hartke cabs, if I rewire as per Series diagram then I should just need a shorted jackplug inserted at the end of the signal chain to complete the circuit if series extension to 3rd cab is not being used..
Proposed setup:

Edited by Al Heeley
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[quote name='Al Heeley' post='1280718' date='Jun 24 2011, 11:16 AM']This shows current standard parallel wiring at the back panel of the Hartke cabs, if I rewire as per Series diagram then I should just need a shorted jackplug inserted at the end of the signal chain to complete the circuit if series extension to 3rd cab is not being used..
Proposed setup:
[/quote]
Looks good

However, to keep the speakers in the series chain in-phase, you'll need to wire it:

Input from amp (+) to speaker cab #1 (+), Speaker cab #1 (-) to Speaker cab #2 (+), then Speaker cab #2 (-) back to amp (-)

Hope that this makes sense?

HTH,
Ian

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[quote name='Al Heeley' post='1280547' date='Jun 24 2011, 04:24 AM']Just bought a 250W Hartke VX 2x10... to position just behind the head of our drummer to help him keep time.[/quote]Bad idea. Splitting low frequency cabs will result in all sorts of phase sourced cancellations. What you should do is simply turn the 1x15 (which I assume is below the 4x10) to face the drummer. That will provide him with the mids he needs to hear, while keeping all the lows sourced from the same point. By the same token should you ever run the bass into the monitors it should be high-passed on the board at 100 Hz, providing the mids to the band to hear you while not causing phase cancellations in the lows. If you must have the 210 near the drummer it should be driven by a separate amp with the lows rolled off for the same reason.

Edited by Bill Fitzmaurice
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[quote name='Al Heeley' post='1280547' date='Jun 24 2011, 09:24 AM']Just bought a 250W Hartke VX 2x10 + horn from a basschat member which would be handy to position just behind the head of our drummer to help him keep time.[/quote]
Isn't that the guy who's supposed to help everyone else keep time? :)

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[quote name='Bill Fitzmaurice' post='1280951' date='Jun 24 2011, 01:25 PM']Bad idea. Splitting low frequency cabs will result in all sorts of phase sourced cancellations. What you should do is simply turn the 1x15 (which I assume is below the 4x10) to face the drummer. That will provide him with the mids he needs to hear, while keeping all the lows sourced from the same point. By the same token should you ever run the bass into the monitors it should be high-passed on the board at 100 Hz, providing the mids to the band to hear you while not causing phase cancellations in the lows. If you must have the 210 near the drummer it should be driven by a separate amp with the lows rolled off for the same reason.[/quote]
I'm not sure I fully understand this, Bill. Are you saying that a 1 x 15 in series with a 2 x 10 (proposed setup) is different to having a 4 x 10 in parallel to a 1 x 15 (current setup)?

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.

Edited by Al Heeley
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[quote name='Al Heeley' post='1281084' date='Jun 24 2011, 09:58 AM']I'm not sure I fully understand this, Bill. Are you saying that a 1 x 15 in series with a 2 x 10 (proposed setup) is different to having a 4 x 10 in parallel to a 1 x 15 (current setup)?[/quote]
I'm saying forget about the 210, use the 115/410 as you have been, aiming the 115 at the drummer, and never split bass cabs.

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

Worth a try for 5 mins of soldering, just to get all 3 cabs working off same amp.

[url="http://www.colomar.com/Shavano/patbox-split-amp.gif"]http://www.colomar.com/Shavano/patbox-split-amp.gif[/url]

Edited by Al Heeley
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