Running two attenuators on the same amp

[fizbin]

...no not in series. Let me explain - say I've got two 8 ohm attenuators (in reality a Muzzle and a THD) and two 8 ohm cabinets. Is there anything potentially damaging or inherently wrong with running one attenuator to each cab and setting the amp impedance at 4 ohms? The impedance of the two attenuators in parallel should be 4 ohms, the same as if it were two speakers loading against the amp right?

Please limit responses to qualified amp-knowing-persons-who-know-about-amp-guts-and-ohm's-law-and-stuff.

Thanks,
Jay

[gw_bluesman]

I do not have an answer for you, but why not run ONE attenuator and daisy-chain the 2 speaker cabs?

I have at times used an attenuator on a gig and while I only run one cab, I cannot imagine using two and having to adjust each one should I need to re-adjust my volume during the show.

Good Luck !!

[fizbin]

I do not have an answer for you, but why not run ONE attenuator and daisy-chain the 2 speaker cabs?

I have at times used an attenuator on a gig and while I only run one cab, I cannot imagine using two and having to adjust each one should I need to re-adjust my volume during the show.

Good Luck !!

Because then I'd need a 4 ohm attenuator. For the sake of this discussion assume I have only two 8 ohm cabs and two 8 ohm attenuators and want to run both cabs at the same time.

(actually I also have a 4 ohm Muzzle, but at times will be using it in another amp at the same time, so consider it off the table for purposes of this discussion)

[gw_bluesman]

Because then I'd need a 4 ohm attenuator. For the sake of this discussion assume I have only two 8 ohm cabs and two 8 ohm attenuators and want to run both cabs at the same time.

(actually I also have a 4 ohm Muzzle, but at times will be using it in another amp at the same time, so consider it off the table for purposes of this discussion)

Ok, got ya .... I didn't factor that in ... I assume you may be using a THD Hotplate?

I have several attenuators .... ie: Weber Mass, Mini-Mass, home-made Airbrake that all support 4/8/16 Ohms.

I also have an Kendrick Trainwreck Airbreak that I am about to put up for sale. While these were Ohm rated (mine is listed as 2 Ohms, I used it with my Super Reverb) they can actually cover a fairly wide load. I wrote Mike at Dr. Z and he said mine was fine for 2/4/8 Ohm load. He did not recommend it for a 16 Ohm load.

Personally, I hardly if ever use my attenuators anymore since I have several amps and 3 speaker cabs so I try and match the rig to the gig.

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Getting back to your situation .... One other point hit me and that is if you are using an attenuator to better manage your rig volume / drive your amp harder ... why not just use one cab?

FYI - For every pair of speakers, you get "speaker coupling" which adds approx. 3db. By eliminating 1 cab, you will be able to in effect lower your volume allowing you to drive your amp harder (assuming that's the tone you are after) and you can then even use your 8 ohm attenuator as it will match your 8 ohm speaker cab.

If I'm missing the point, my short answer would be to use caution and get 1 attenuator (that will match your load).

Regards and good luck !!

[mike80]

I'll try to answer this the best I can.

In theory, it should work the way you have described. Two 8 ohms loads in parallel will be 4 ohms. An attenuator is basically a load, so I don't really see a problem using it like that.

Gw bluesman makes a good point though with the 2 cabs and volume.

[fizbin]

I'll try to answer this the best I can.

In theory, it should work the way you have described. Two 8 ohms loads in parallel will be 4 ohms. An attenuator is basically a load, so I don't really see a problem using it like that.

Gw bluesman makes a good point though with the 2 cabs and volume.

Thanks for the info...

I use single 1x12 cabs. It's more than just volume. 2 1x12s at the same relative volume as a single 1x12 just sounds better. I can project sound in more directions at the same volume (I angle them slightly apart) which sort of distributes the highs in a much better fashion than using one cab, especially a 1x12. Even with a single 2x12 or 4x12 the sound (especially the highs) tends to get projected in only one direction. I've found (my opinion of course) that 2 open back 1x12s angled slightly apart gives me the room filling sound that I like best.

[doctorx]

As was said, in theory it should work. The important thing here is that the amp sees the proper impedance. So, if the amp wants to see 4 ohms, two 8 ohm attenuators in parallel = 4 ohms.

It would give better peace of mind if the amp was well built and the OT is robust, but give it a try and monitor the sound of the amp closely and also how how it runs.

[fizbin]

..., but give it a try and monitor the sound of the amp closely and also how how it runs.

Curious - what should I be listening for in the way of the amp having a hard time or damage being done? Will I smell smoke or something?

Amps are a stock Ceriatone DC30 and 36w. I might try it with either. That allows me to run my 4 ohm Muzzle the normal way on the other one, have someone over to jam using my other amp, get the sounds I like, and keep a reasonable volume level in my basement.

[mike80]

That makes more sense with 1x12s. When someone mentions cabs and managing volume, I tend to think 4x12.

What you'll want to listen for is basically a sound that doesn't sound natural. A lot of distortion that shouldn't be there, or a fuzzy sound.

You'll know when the amp is having a hard time just by the way it sounds.

[doctorx]

Curious - what should I be listening for in the way of the amp having a hard time or damage being done? Will I smell smoke or something?

Amps are a stock Ceriatone DC30 and 36w. I might try it with either. That allows me to run my 4 ohm Muzzle the normal way on the other one, have someone over to jam using my other amp, get the sounds I like, and keep a reasonable volume level in my basement.

As I said, technically and in theory it should work fine. It is an unusual setup though and, well, "Taint nacheral" ;) to do this.

I don't think anything funny will happen, in a way it's a good idea. You could put one cab over by the bass player for instance and let him adjust the volume to suit him. Or if one cab has a different speaker than the other and is more efficient you could balance the volume between them.

When I said to monitor I meant to just be a little more aware of possible funny sounds and/or the amp running hotter than normal. Attenuators are supposed to supply the proper impedance to the amp but that's not always the case.

Trust me if something does go screwy you will know it.

I have a couple of attenuators myself and could put together a rig like this, I might try it.

[planetal]

Do both attenuators have 2 outputs? You could use one 4 ohm attenuator into 2 8 ohm cabs.. that will give your amp and attenuator a 4 ohm resistance. I'm pretty sure the hotplate has 2 speaker outs...
either way you do it (2 attenuators into 2 cabs.. or 1 attenuator into 2 cab).. you will be fine...

You have 2 8ohm taps only.. or do you also have 1 4ohm tap on the amp?

[fizbin]

Do both attenuators have 2 outputs? You could use one 4 ohm attenuator into 2 8 ohm cabs.. that will give your amp and attenuator a 4 ohm resistance. I'm pretty sure the hotplate has 2 speaker outs...
either way you do it (2 attenuators into 2 cabs.. or 1 attenuator into 2 cab).. you will be fine...

You have 2 8ohm taps only.. or do you also have 1 4ohm tap on the amp?

I have a 4 ohm, but it might be in use on another amp at the same time. I'm hoping to not have to buy another attenuator and cover what I need with two 8 ohm attenuators in parallel.