Opinions on powering a 4x10 and a 2x10 in series

kai_ski · #1 10-25-2010, 02:28 PM

I did an extensive search, but some people insist on listing their gear (by model name) in their sig so google-based search wasn't helpful and the three-letter limit on the TB search engine is a PITA.

Right now my rig consists of a pre/power combo using an Avalon U5 and a Face Audio F500TS (700W @ 8 ohm, and ~1000W @ 4 ohm, bridged.) I have been using it to power a pre-Fender SWR Goliath III (700 W), which to my ears sounds incredible and I love the tone. I find myself playing more and more outdoor gigs, and while the rig sounds great, it's sometimes a little hard to hear myself with a drummer, two guitars and keys. Recently, a used Goliath JR III (350 W, pre-Fender with the same style grill as my Goliath III) showed up on the local classifieds, and I thought it might be cool to run it on top of the headcase to get some ear-level projection.

Obviously the poweramp is two channels, so I could run the two cabs parallel, but is there any issue with bridging the channels in the amp and running them in series?

How does running two cabs in series effect their individual power handling capabilities? Is it a scenario of A+B=C (700 W + 350 W = 1050 W) or will 1000 W through both cabs be putting undue stress on the woofers in the 2x10? Both are 8 ohm cabs.

JimmyM · #2 10-25-2010, 02:50 PM

if you run them in series, you're going to get less power to each cab. i think you meant you were going to run them bridged but in parallel. which, unfortunately, you can't do. the head has a 4 ohm limit bridged, and two cabs running in parallel creates a 2.67 ohm load. the best thing to do is run each cab on each side and adjust the volumes to where they're putting out comparable volumes.

Bass_Pounder · #3 10-25-2010, 02:58 PM

Quote:

Originally Posted by kai_ski

Obviously the poweramp is two channels, so I could run the two cabs parallel, but is there any issue with bridging the channels in the amp and running them in series?

How does running two cabs in series effect their individual power handling capabilities? Is it a scenario of A+B=C (700 W + 350 W = 1050 W) or will 1000 W through both cabs be putting undue stress on the woofers in the 2x10? Both are 8 ohm cabs.

If both cabs are 8 ohms, running them in series will produce a 16 ohm load for the amp, cutting your power output by about half what it is at 8 ohms.

I think you are confusing your terminology.

Running a cab of of each channel of the power amp is just that - not parallel.

Connecting the two cabs at the same time to the same channel IS parallel, whether you run them both off the channel, or if you daisy chain the cabs together.

Your amp will handle a 4 ohm load when bridged, so you can run both cabs together.

However, you will be limited to 2X the power of your lowest rated cab (2 X 350W= 700 watts). You are limited by the capabilities of your smaller cab which will run out of gas alot quicker than your bigger cab.

It is more advisable to run one cab off of each channel, and use the amp controls to balance the power to the cabs as Jimmy said.

kai_ski · #4 10-25-2010, 03:01 PM

okay, thanks for the clarification. i always switch that terminology around for some reason. I'll probably just hold out for another 4x10 to have a balanced system.

JimmyM · #5 10-25-2010, 03:09 PM

Quote:

Originally Posted by kai_ski

okay, thanks for the clarification. i always switch that terminology around for some reason. I'll probably just hold out for another 4x10 to have a balanced system.

best option by far.

gregwatts2008 · #6 10-25-2010, 03:10 PM

For me, the Goliath sounds better on the floor, not raised or on wheels. I play a GK 1001 RB II with a Goliath cab and it rumbles. If yours has wheels, turn it over on its side and you will notice a difference.

kai_ski · #7 10-25-2010, 03:30 PM

no wheels. it sounds great when I can get it far enough away from me, but when i have to stand close it's just a tad difficult to hear with piano/vox/guitars hitting my ears out of the monitors. if i could play based only on feel, then i wouldn't change a thing because i can feel every damn note with this thing.

JimmyM · #8 10-25-2010, 03:33 PM

since it's not on wheels, try tilting it up toward your ear. you won't lose any floor coupling by doing that, and you'll hear the rest of its range a lot better vs it blasting your knees.

BigOldHarry · #9 10-25-2010, 03:40 PM

Quote:

Originally Posted by kai_ski

...I'll probably just hold out for another 4x10 to have a balanced system.

I don't agree: I have run my Epi 4x10 + an Epi 2x10 (both 8 ohms) with my Ashdown 400 watt head - I ran them "parallel", as in not daisy-chained, and it sounded great... Plus it was nice having two speakers near ear level!

ErnieD · #10 10-25-2010, 04:03 PM

I've been told here and have tried this. Have the 410 be 4 ohms and the 210 be 8 ohms, so that each driver is getting equal watts. I did this with a couple Eden XLT cabs 210/410 and it worked well.

To Big O' Harry, if your only sending about 200 watts into each of your cabs with that Ashdown head, I don't suppose that's a whole lotta watts going into those Epi cabs to make the 210 pump much more than the 410. So that should work fine for you.

With a pre/power amp setup at gig this past Saturday, I placed a GB Neox112T above my UL410-II, both 8 ohms. Ran it on two channels where I sent more volume to the 410 and just the amount of volume to the 112T to hear myself up by my ears. Worked real well. Then I switched to bridge>UL410 only.

This was the best scenario with the Crown amp bridged @ 8 ohms into the UL410 alone, I stepped up abit from the rig and it was great. Don't think I'll use a second cab often.

RickenBoogie · #11 10-25-2010, 05:08 PM

^it's 4 ohms min bridged, so can't do an 8 and 4. And, I agree, 2 410's IS the best option.

kai_ski · #12 10-25-2010, 07:38 PM

Actually I don't think it's 4 ohms min bridged (I don't know where that came from.) Each channel has a rating down to 2 ohm so I would think it would be safe to run it bridged down to 2 ohm. The company is local to me so I could call to make sure.

billfitzmaurice · #13 10-25-2010, 08:24 PM

Quote:

Originally Posted by kai_ski

Each channel has a rating down to 2 ohm so I would think it would be safe to run it bridged down to 2 ohm.

It isn't safe, and there's no point in doing so anyway. Run each cab off its own channel.

babebambi · #14 10-26-2010, 12:52 PM

What Bill said!
Bill's advise usually saves you money and headache down the road.

Richard Lindsey · #15 10-26-2010, 02:20 PM

Quote:

Originally Posted by kai_ski

Actually I don't think it's 4 ohms min bridged (I don't know where that came from.) Each channel has a rating down to 2 ohm so I would think it would be safe to run it bridged down to 2 ohm. The company is local to me so I could call to make sure.

No, as a rule, if an amp can do a minimum load of 2 ohms/channel, it can only do a minimum of 4 ohms bridged. 2 ohms bridged would be like 1 ohm/channel.

kai_ski · #16 10-26-2010, 03:26 PM

Quote:

Originally Posted by Richard Lindsey

No, as a rule, if an amp can do a minimum load of 2 ohms/channel, it can only do a minimum of 4 ohms bridged. 2 ohms bridged would be like 1 ohm/channel.

thanks.