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4ohm Head into 8ohm cab


jackcoleby
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Can anyone help me. I've got a Line 6 HD 750 head, it's perfect for me and my band but I wana try a new/different cab. It's got 2 outputs with a minimum impedance of 4ohms. So 2 8ohm cabs or 1 4ohm cab. ATM I've just got the one 4ohm cab. What I'm wondering is, is it safe to attach 1 8ohm cab till I can afford another.

Thanks guys

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One 8 ohm cab will be getting around 500 watts if you run the amp flat out.

Are you really running the amp that hard? The more likely scenario is that you'll only be using around half or even less. I hardly every go over half power even in my loud bands, so if your cab is rated to handle anything from 300 watts to 500 watts then you should be fine.

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You might limit the output in terms of wattage, but you'll hardly tell the difference (if at all between a 4Ohm and an 8Ohm cab if they're the same cab).

It's 10x wattage to sound twice as loud innit? So halving the wattage used does little to perceived volume. You'd have to halve it another 4 times to perceive half volume.

I rewired my Acme Low B2s to be 16Ohm not 4Ohm and couldn't hear the difference. And they're real power guzzlers.

Edited by bigjohn
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General rule of thumb. If the total impedance of the cab(s) is higher than the impedance rating of the amp (so let's say, 8 ohm cab plugged into a 4 ohm amp output), you don't have a problem. If the impedance of the cab(s) is lower than that of the amp (like 2 x 4 ohm cab (making a 2 ohm load) plugged into a 4 ohm amp output), stop what you're doing before you smell burning.

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One note, if I may chime in- you'll notice [i]more air [/i]being pushed with 2 cabs... and if you get decent matched cabs (at 8 ohms each), they'll probably 'link up' and increase the apparent dB by a few: You'll tend to get a bigger-sounding bottom and generally more presence in the live mix- so there are benefits to using 2 cabs.

Edit: Also you get the full benefit of your amp's headroom at 4 ohms, another reason for more apparent lows and presence...

If I'm indoors with a line to PA, or playing a low-key gig, I almost always just bring one cab. We'll be playing in a funky small-town parade on back of a flat-bed tow-truck next month though, so I'll be stacking the TL-606s for that nuttiness...

Edited by Count Bassie
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[quote name='xgsjx' timestamp='1339929340' post='1696311']
I've never understood the point of a 4Ω cab unless the amp's min load is 2Ω or the cab is unlikely to need doubled up.
[/quote]

I use a 4ohm 4x10 cab. I fall into the second category you mention. I have no need for a second cab. I don't want to humph more than one cab of this bulk to a gig, I think that's a pretty stupid thing to do considering the size of venues that I play (and suppose I ever will play for the forseeable future). The point is that it's plenty loud enough and shifts plenty enough air for my needs. My head is 500W. My cab handles 1200W. It also means that I'm cool with sharing my rig if it makes the gig go smooth. Go on, max the amp if you like, I don't give a toss :)

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[quote name='jackcoleby' timestamp='1339424506' post='1688215']
Oh no, I'm not pushing it hard at all. Never been past half vol. my current cab is a Marshall 410 with a max of 1200 watts. But it's 4 ohm and I want to change to 2 8ohms. Just wondering if it's safe to run with just one 8ohm for a month or so.
[/quote]

The position of your volume knob doesn't mean much in terms of what the amp is currently outputting - there's many factors that dictate that - the signal level out of the bass, the pre-amp gain, eq, speaker load etc.

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I`m another 500 watts at 4 ohms into a single 4ohm 4x10 cab. I just don`t play anywhere requiring more gear - and if I did, I`d expect to go through front of house pa. My amp rarely goes above the 9 o`clock position on volume.

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[quote name='xgsjx' timestamp='1339929340' post='1696311']
I've never understood the point of a 4Ω cab unless the amp's min load is 2Ω or the cab is unlikely to need doubled up.
[/quote]

My Genz 2x12 is 4 ohm so I can use the full output (600watts) from my amp with just that cab, what else would you add to it? If anything it would be just another 2x12 in which case Id be using a head with a 2ohm minimum load (GBE1200) giving me 2 x 2x12 and 1200watts of power with maximum headroom available, Yowzer!!! In any other instance I take either a 1x10 or a 1x12 both rated at 8 ohm so no worries there, the only thing I cant do is take 2 1x12's (as I only have one!) and leave one in the van If the venue does not need 2 when I get there but the vertical style of the Genz 2x12 does not really make much difference as I dont presume many of us let people stack stuff on top of their amps anyway? The footprint is the same If you get my drift. :)

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[quote name='subsong' timestamp='1340034593' post='1697984'] With a bigger cab or a pair of cabs, you get a different tone than you would with a single one or a smaller one. It's just about what you like. I like having the option of both....... [/quote]

Unless you're using 2 of the same cab, then you just get more of the same. :)

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[quote name='xgsjx' timestamp='1340037020' post='1698048']
....Unless you're using 2 of the same cab, then you just get more of the same....
[/quote]

Depends on how they have been designed.

For example, apparently my Bergantino AE210 cabs together sound exactly like the AE410, but the AE212 was voiced with more bottom end than 2 AE112's.

I like lots of bass, but that's not enough of a bonus to make me want to lift 55 lbs.
[font=Arial][size=2] [/size][/font]

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[quote name='chris_b' timestamp='1340094174' post='1698858']
Depends on how they have been designed.

For example, apparently my Bergantino AE210 cabs together sound exactly like the AE410, but the AE212 was voiced with more bottom end than 2 AE112's.

I like lots of bass, but that's not enough of a bonus to make me want to lift 55 lbs.
[/quote]

That's a good point.

But does 1 AE210 sound the same as 2 AE210s (but just with less volume)?

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[quote name='xgsjx' timestamp='1340096522' post='1698900']
....But does 1 AE210 sound the same as 2 AE210s (but just with less volume)?....
[/quote]

Not sure, I've never used just one. But, to my ear, 1 AE112 does sound like a quieter version of 2 AE112's, although 2 cabs together changes the more than just volume.

I don't know how these observations apply to the cheaper, commodity, end of the cab world. At that level there seems to be less design input and more marketing input.

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