Amp light clipping / barefaced cab resistance?

[Hammer_]

Looking for some advice on setting up my amp/cabs. 
 

I have a helix > matrix gt1600fx into two barefaced big baby IIs. 
 

the cabs are rated 800w each and I am daisy chaining them off one channel from the amp. So in theory the amp should be providing 800w power?

 

however I’m getting the clip light flickering on at just over half power. I’d like to get a bit more volume/headroom out of the set up but I don’t want to push the amp too much as I don’t like seeing the clip light stay on for too long. 
 

does anyone know if I would be better running a single 8 ohm cab from each matrix channel, or daisy chain them with speakons running from a single channel. 
 

if the latter option is the right approach why do I feel like I’m not getting full 800w into 4ohm without clipping as I power up the volume?

 

cheers dudes. 

[Woodwind]

for the moment don't worry about numbers on a dial, but how loud are the two cabs sounding when the clip light engages?

 

The thought of two big babys running when an amp is clipping terrifies me volume wise.

 

Is the sound distorted or cracking?

 

Have you got a lot of bass boost going on in the eq of your helix?

 

It might be that with whatever eq you are running you have hit the maximum of what that power amp can deliver.

 

If you just run one speaker cab with the amp settings in the same place how much of a volume reduction is there?

 

[Reggaebass]

Can’t help you with the maths, I’ve got one bb ll , but 2 barefaced big baby’s is immense 👍

Edited December 5, 2021 by Reggaebass

[Bill Fitzmaurice]

Run each cab off its own power amp. I won't bother getting into the whys and wherefores but the watts don't matter.

Edited December 5, 2021 by Bill Fitzmaurice

[BassmanPaul]

Incidentally, speaker cabinets have Impedance not Resistance. Impedance is an AC measurement whereas Resistance is measured at DC.

[itu]

To the transistor amp the bigger impedance is usually easier load. Think it like a nail against your thumb: the smaller the Z, the sharper the head.

As our grand old man Bill F. already told us, please use one amp / cab, and your amp will love you.

Edited December 7, 2021 by itu

[Hammer_]

Thanks for your replies guys. I do have 2 matrix power Amps and had thought about running one amp one cab. 
 

one amp is a gt1600fx and the other is a gt800fx. I guess I could mix the 2 but would have different volumes on each. 
 

to answer the question about 2 x BBII yes they are loud. But I don’t feel the same heft and pure power like you do when playing in front of an ampeg SVT / 810 rig. 

 

I’ve got a big show coming up this weekend and want to try and ensure I’ve got a solid punch behind me that’s why I’m asking for thoughts on how to optimise my set up. 
 

thank you brothers. 

 

[Hammer_]

11 hours ago, Woodwind said:

Is the sound distorted or cracking?

 

Have you got a lot of bass boost going on in the eq of your helix?

 

It’s not distorted at all really. I’ve cut the low end below 100htz which helps. 

[Reggaebass]

A friend of mine runs 2 big baby ll cabs from one amp successfully for big reggae gig’s, but I’m not sure what amp he’s using at the moment, I don’t think you need 2 amps 

[Baloney Balderdash]

Are you playing up a stadium without PA support?

[Bill Fitzmaurice]

4 hours ago, Hammer_ said:

one amp is a gt1600fx

 

Isn't that a dual channel amp?

[Hammer_]

2 hours ago, Baloney Balderdash said:

Are you playing up a stadium without PA support?

No dude. Biggish stages where I move around and want to get the best/cleanest sound I can from my back line 

[Hammer_]

1 hour ago, Bill Fitzmaurice said:

Isn't that a dual channel amp?

Yes bro it is. 

[fretmeister]

8 minutes ago, Hammer_ said:

Yes bro it is. 

So put 1 cab on each channel.

 

Job done.

[pburrows]

Yes have tried that. If my understanding is correct.... both cabs 8ohm, sending each side of the 1600w power amp to 8ohm give 800 per side @ 8ohms, so the cabs do not get their full capacity? The cabs are rated at 800w. Is there any technical difference running them on one channel each, as opposed to daisy chaining them on one channel, therefore giving a 4ohm resistance?

[chyc]

This is an interesting topic as it completely goes against everything I knew about amp/cabinet matching until today. To quote the manual

 

Quote

[W]here the speakers power rating is larger than
that of the amplifier channel, the clip or peak lights will illuminate repeatedly on the amplifier if
it is being driven too hard, this will often also result in an audible increase in distortion of the
sound from the speaker system. Where this happens, the volume level should be reduced.

 

I always thought that this is caused by the impedence being too low rather than the power rating of the cabinet. Also, if you have to back off the volume level, what would have happened if you'd used a cabinet rated at a lower power rating?

 

Confused.

[Bill Fitzmaurice]

2 hours ago, pburrows said:

 If my understanding is correct.... both cabs 8ohm, sending each side of the 1600w power amp to 8ohm give 800 per side @ 8ohms, so the cabs do not get their full capacity?

Once again, with feeling:

The watts don't matter.

[Dan Dare]

Bill's correct that the watts don't matter. See many other threads for explanations of how quoted/claimed wattage is not an accurate indicator of what an amp is capable of delivering in real world conditions. 

 

Just because your amp is set on just over half power, it doesn't mean that it is only delivering half of its power. It depends on the gain structure of the amp. The clip light may be being triggered by the input level (if, for example, your instrument is active or has particularly hot passive pickups). Lowering the input gain and increasing the master volume may help in that case.

[Chienmortbb]

The thing is that the impedance is probably the problem. It is likely that the cabinets drop below the minimum impedance that the amp can handle at some of the peaks at some frequencies.  I agree that using  one channel to each cabinet would almost certainly solve the problem. It would give each channel an easier time.

[BassmanPaul]

One thing to remember using an amplifier with two power amps is do not connect both amplifiers to the same cabinet. that's a recipe for disaster.

[itu]

Looking at the pot hats? They do not tell anything about the actual power level. They tell that they are set to certain direction. Nothing else.

 

Once more, if the amp was able to push power without limits, the cabs should be connected parallel until the impedance was something like a fraction of one. But...

 

When the impedance is getting lower, the current is rising in the amp. This heats the power amp. When the current is rising, at some point the amp reaches its limits and can not push power anymore. It may even melt. This may equal that the sound is affected, too: transients aren't sharp anymore, no more attacks (ADRS, anyone?). By the way, the attack is super important to instrument perception and sound.

 

Once more: If you think the impedance (from amp's point of view) is like nail, and the current capacity of the amp is your thumb, you get the idea of what lowering the impedance (nail getting sharper) means to your thumb (ouch!). It starts to hurt pretty soon, when the current rises while the impedance gets lower. Of course you can lower the impedance as much as you like, but the amp gets really hot while not producing any decent power anymore.

 

One thing that people tend to mess up is that W is not directly the same as dB, although they are faintly connected. The difference of power seems to be hard to understand, because the difference of 100 W - 1 000 W is very distinctive 10 dB, while 100 W - 200 W is only 3 dB. These things are not linear, my dear Watson.

[agedhorse]

An amp properly designed to drive a 2 ohm load will be just as effective as an amp properly designed to drive a 4 ohm load into their respective loads.

[Downunderwonder]

The amp supposedly does 480w per cab channel with 8 ohms per channel. That's your lot.

 

It would be pretty well equivalent to a BigTwin with a 1000W amp.

 

That's got to be crazy loud enough for most people!

 

Even one channel 800w split to two cabs I doubt you could hear a whole lot of difference because each cab will be making almost all the noise with the first 300w it gets. 

On 07/12/2021 at 05:49, Bill Fitzmaurice said:

Once again, with feeling:

The watts don't matter.

Unless you have too many and try to use all of them all at the same time, or too few.

 

[Chienmortbb]

15 hours ago, itu said:

One thing that people tend to mess up is that W is not directly the same as dB, although they are faintly connected

This is almost correct. If we assume that both amplifier amd speaker are substantially linear, then the correalation between watts and SPL is also linear. As we approach the limits of either amplifier of speaker the linearity can reduce.

[mybass]

On 06/12/2021 at 14:31, Hammer_ said:

Yes bro it is. 

I may have missed something here but…….Dual channel or stereo amplifier? A dual channel runs as mixing two inputs into a mono output signal whether using (one 8 ohm)or both speaker (16th ohms) outs to your two cabs…. A stereo amp will allow two separate load outputs for two separate speakers….8 ohm load per cab.