Author Topic: how to run a Sunn 2000s amp through multiple cabs  (Read 6065 times)

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Offline ursula

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how to run a Sunn 2000s amp through multiple cabs
« on: August 03, 2010, 05:52:32 pm »
i recently purchased a sunn 2000s amp. im looking for a used 2x15 cab. what cabs would be best for this amp? i was hoping to run my head through two cabs eventually and i dont really knw how to go about this. any suggestons or recommendations? ive only recently taken an interest in gear so im kinda green when it comes to this stuff. ive been playing bass for 13ytears and recently joined a metal band that i got this amp for. ive been running through a 4x10 ampeg cab but i need that cab for another amp.
thanks, ursula beatrice stuart

Offline biltmore

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Re: how to run a Sunn 2000s amp through multiple cabs
« Reply #1 on: August 03, 2010, 05:59:09 pm »
Assuming that you have 8 ohm and 4 ohm outputs, you'll need 2 cabinets ... each one wired at 4 ohms.

Offline HRobert

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Re: how to run a Sunn 2000s amp through multiple cabs
« Reply #2 on: August 03, 2010, 06:02:54 pm »
Assuming that you have 8 ohm and 4 ohm outputs, you'll need 2 cabinets ... each one wired at 4 ohms.

I'd like to correct the statement.  If your amp has 8 ohm and 4 ohm outputs, you will need two 8 OHM cabs,  not two 4 ohm cabs.  Two 4 ohm cabs in parellel would give you a final load of 2 ohms, whereas two 8 ohm cabs in parellel are a final load of 4 ohms.

Offline EdBass

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Re: how to run a Sunn 2000s amp through multiple cabs
« Reply #3 on: August 03, 2010, 08:35:46 pm »
There are numerous threads covering this, if you do a quick search. Here's a thread with the "cliff's notes" version;
http://sunn.ampage.org/sdp/index.php/topic,4575.msg17281.html#msg17281

Offline pickinatit

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Re: how to run a Sunn 2000s amp through multiple cabs
« Reply #4 on: August 04, 2010, 07:53:44 am »
I have a 2000S with 4 ohm & 8 ohm outputs.  I have 2  215 cabinets that are each 4 ohms.  I wanted to be able to use a single cabinet but have the option to use both if the occasion warranted/allowed.  I though about re-wiring them to turn them into 2  16 ohm cabs, but instead, for my Birthday (at my suggestion) my wife had a local "Cable Company" (specialize in stereo and Hi-Fi stuff really) make me up a
"Series cable"  for hooking the two cabs in series for an 8 ohm load into the 8 ohm jack.  Works like a charm...allows me to keep the single cabs at 4 ohms each OR  use both cabs at an 8 ohm load.    WIN  /  WIN

Offline HRobert

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Re: how to run a Sunn 2000s amp through multiple cabs
« Reply #5 on: August 04, 2010, 08:14:48 am »
I have a 2000S with 4 ohm & 8 ohm outputs.  I have 2  215 cabinets that are each 4 ohms.  I wanted to be able to use a single cabinet but have the option to use both if the occasion warranted/allowed.  I though about re-wiring them to turn them into 2  16 ohm cabs, but instead, for my Birthday (at my suggestion) my wife had a local "Cable Company" (specialize in stereo and Hi-Fi stuff really) make me up a
"Series cable"  for hooking the two cabs in series for an 8 ohm load into the 8 ohm jack.  Works like a charm...allows me to keep the single cabs at 4 ohms each OR  use both cabs at an 8 ohm load.    WIN  /  WIN

I did basically the same thing.  I have a 67 Sentura II with 8 and 4 ohm outputs...but my 2 x 15 cabs are 4 ohms each.  Instead of a wiring type harness I built a "series box", a simple little box with 3 - 1/4" female jacks wired in a series configuration. The box, although a little bigger than really needed, is 3.25" wide x 4.25" long x 1.75" deep. I don't have a wiring harness to deal with as I can use regular speaker cables from the amp to the box, and from the box to the speakers.  I will post a picture later.

Rob
« Last Edit: August 07, 2010, 09:10:58 am by HRobert »

Offline biltmore

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Re: how to run a Sunn 2000s amp through multiple cabs
« Reply #6 on: August 04, 2010, 12:00:28 pm »
Crap, I meant 8 ohms! Thanks for the correction, Rob. Would love to see some pictures of your series box.

Offline D.M.N.

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Re: how to run a Sunn 2000s amp through multiple cabs
« Reply #7 on: August 04, 2010, 01:18:56 pm »
Yeah, I have a 4 ohm 2x15 as well, but I have a slightly different question: if you have a 8&4 ohm 2000s, how could you use only one 4 ohm cab? Or would you have to rewire the cab to 16 ohms and switch the output taps on the transformer?
House of the Rising Sunn........
-----------------------------------
1969 2000s
1972 2000s
1970 1200s
1968 1000s
1969 200s
2010 2000s DIY 2x15
1971 2000s 2x15
1969 2000s 2x15
1972 2000s 2x15
1968 1000s 2x15
1970 1200s 6x12

Offline HRobert

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Re: how to run a Sunn 2000s amp through multiple cabs
« Reply #8 on: August 04, 2010, 09:37:10 pm »
Yeah, I have a 4 ohm 2x15 as well, but I have a slightly different question: if you have a 8&4 ohm 2000s, how could you use only one 4 ohm cab? Or would you have to rewire the cab to 16 ohms and switch the output taps on the transformer?

Very simple...you just plug the single 4 ohm cabinet into the 4 ohm output.  The outpot transform is wired to recognize the load.  In the past I've run a single 4 ohm cab throught the 8 ohm output with no problems.  The problem arises when you run two 4 ohm cabs, which give you a 2 ohm load, on an amp designed to only go as low as 4 ohms.

Rob

Offline D.M.N.

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Re: how to run a Sunn 2000s amp through multiple cabs
« Reply #9 on: August 05, 2010, 02:07:52 am »
Ah, that's simple enough then. I wasn't sure if the 8 ohm primary output needed something plugged into it as well. Thanks!

Oh, on a side note, just clarifying, am I correct in believing that if you run a 16ohm cab into a 8ohm output, it doesn't do damage, you just don't receive full power? Please correct me if this is wrong, I'd hate to do damage.
House of the Rising Sunn........
-----------------------------------
1969 2000s
1972 2000s
1970 1200s
1968 1000s
1969 200s
2010 2000s DIY 2x15
1971 2000s 2x15
1969 2000s 2x15
1972 2000s 2x15
1968 1000s 2x15
1970 1200s 6x12

Offline EdBass

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Re: how to run a Sunn 2000s amp through multiple cabs
« Reply #10 on: August 05, 2010, 09:29:22 am »
Ah, that's simple enough then. I wasn't sure if the 8 ohm primary output needed something plugged into it as well. Thanks!

Oh, on a side note, just clarifying, am I correct in believing that if you run a 16ohm cab into a 8ohm output, it doesn't do damage, you just don't receive full power? Please correct me if this is wrong, I'd hate to do damage.

That's correct for transistor amps, not tube amps. For a tube amp to function optimally (and safely) you want a matched load; 8 ohm load to the 8 ohm tap, 4 ohm load to the 4 ohm tap, etc.

Once again, the search function is your friend. This was from Jan. of this year;

Speaker impedance isn't an exacting science, not nearly as cut and dry as the ohm rating of a resistor for example, which is generally a <5% variance from the marked rating.
Speaker impedance ratings are "nominal"; for example an 8 ohm driver can fluctuate from just a couple of ohms to 100+ in actual use depending on frequency, power, cabinet, etc.

But, there is a reason that tube amps have output transformers, and a reason they are tapped off at specific impedances. The output transformer is used to match the load (speaker) impedance to the output stage impedance (tubes) for optimal performance.
A 2.67 ohm load on your amp probably won't cause any damage, your tech is right about tube amps being pretty flexible, but the mismatched load can hinder the amp from working up to it's design specification.

Which can be good or bad depending on what you are trying to accomplish. When I was a kid my goal was to be as loud as I could get, and using my basic high school electronics class skills I would hook up as many speakers as I could to whatever amp I could get my hands on with little regard for sound quality. I understood impedance, but took extensive liberties in pursuit of "loud".
Eventually I figured out that for me anyway, quality was a more desired attribute than quantity.
IMO it's easy to get loud, not so easy to sound good doing it.

HOWEVER; That post was addressing a "too low" impedance situation. The situation you described is a “too high” impedance example, and IMO a load that’s too high in impedance is potentially more destructive than too low impedance.
Running a tube amp with no load plugged into the speaker jacks can cause very expensive damage. While the phrase “no load plugged into the speaker jacks” may sound like zero ohms, it’s in fact just the opposite, it’s about a bazillion ohms, If you short the jack; connect the ring directly to the sleeve, that’s  close to zero ohms.

With that in mind, here’s yet another post from earlier this year that I found in a couple of seconds using the search function.

Should have mentioned this but you NEVER want to have your head set to a higher load than the speakers because you risk blowing hte output transformer. ie. an 8 ohm head going into a 4 ohm cab

Its OK the other way around, say a 8 ohm head going into a 16 ohm cab, you will just lose a little bit of volume because you're not using the amp efficiently but it won't hurt it.

I think you have that backwards. What you posted seems as if you are trying to apply SS amp wisdom to a tube amp, and they are different animals indeed.

Additionally, many people knowledgeable about tube amps say that running a tube amp at a higher impedance than the load is better then running it at less. That is, it's better to run a 4 ohm load at the 8 ohm setting than vice versa, which is decidedly not the case with transistor amps.

Tube amps are pretty rugged and will generally tolerate a mismatch pretty well. Speaker ratings are “nominal”, which in kind of like an average, and an 8 ohm cabinet can actually show an amp anywhere from <3 to >50 ohms depending on frequency, power, etc..
But IMO, as Isaac points out, a lesser load is preferable to a higher load.

Leo Fender’s amp designs had a jack that shorted out when there was no speaker plugged in as a protection device.
That is; without a plug in the jack it was a dead short; an 8 ohm tap going into a +/- ZERO ohm load – to keep from damaging the amp. If Mr. Fender felt “higher was better” as you posted, he would have left the jack open when there was no plug as a safety measure.

As is mentioned in the above posts, tube amps are pretty rugged, and will take pretty much abuse before they give up their magic smoke. I think it usually takes an extreme impedance mismatch at fairly high output levels to cause permanent damage, however your amps performance can be easily compromised by mismatching loads.

Offline D.M.N.

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Re: how to run a Sunn 2000s amp through multiple cabs
« Reply #11 on: August 05, 2010, 12:41:09 pm »
Ah, well, that answers my question more than adequately. Thank you very much Edbass, always good to have you weigh in.
House of the Rising Sunn........
-----------------------------------
1969 2000s
1972 2000s
1970 1200s
1968 1000s
1969 200s
2010 2000s DIY 2x15
1971 2000s 2x15
1969 2000s 2x15
1972 2000s 2x15
1968 1000s 2x15
1970 1200s 6x12

Offline HRobert

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Re: how to run a Sunn 2000s amp through multiple cabs
« Reply #12 on: August 06, 2010, 03:59:47 pm »
Here are some pictures of the "Series Box" that I put together so I can run both of my 4 ohm, 2x15 cabs with my Sentura II.  This box puts two like-resistance cabinets in series so that the load is doubled....like running two speakers in series.  I have two 4 ohm cabs.  I can use one 4 ohm cab using the 4 ohm out on the back of my Sentura, or by using this box I can run both in series at an 8 ohm load. Using this allows me to use regular speaker cables, and I don't have to have a special three legged cable made..

The Series Box has three jacks; the Amp-In input jack (from the speaker output on the amp), and Speaker jacks A & B.  The wiring is set up like this, please refer to the picture:  The RED wire connects the TIP of the AMP-IN jack to the TIP of of the SPEAKER "A" jack.  The GREEN wire connects the GROUND of the SPEAKER "A" jack to the TIP of the SPEAKER "B" jack. The BLACK wire connects the GROUND of the SPEAKER "B" jack to the GROUND of the AMP-IN jack....thus completing the series circuit.  

The project box is from Parts Express, part number 320-704, and is 4.3" x 3.2" x 1.7", comes with a cover with 4 screws, and is priced at $5.33.  The three female mono jacks were about $.75 each. The wire is, if I remember correctly, 16 gauge multi strand.  A very economical way to solve a load problem.
« Last Edit: August 15, 2010, 08:05:49 am by HRobert »

Offline biltmore

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Re: how to run a Sunn 2000s amp through multiple cabs
« Reply #13 on: August 06, 2010, 10:01:34 pm »
Thanks a ton for posting that, Rob!!! I may just have to build one myself ... even though I don't need it at the moment.