Mesa Subway 800 through 2 x 250 watt cabs, thoughts please?

[karlfer]

I have 2 x Aggi 250 SL incoming. Expensive but I couldn't find 2 x BF Super Midgets (and new they are simply too much).

I love the Mesa 800 but put it up for sale as it is STUPID loud, none of this max volume at noon on the rotary, it just keeps on giving.

The only trade that floated my boat is no longer an option. I have a guy coming round to see the Mesa tonight. Nice guy but legendary haggler & it ain't gonna end well .

So, I'd REALLY like to keep the Mesa, it's powerful, simple & easy to cart around BUT, I'm really twitchy at putting it through 2 x 250 cabs.

Circumstances of use.

Thankfully down to one band now. Singist insists on everything through PA & low backline volume. I really only need a DI box but that ain't gonna happen

The only control I really adjust "in gig" is the voicing thingy, from about 9 o'clock to sometimes around 1 o'clock.

Bass, mid, treble  around noon, gain & volume usually around 10 o'clock. After that, singist usually usually frowns & winges. All other tonal changes done on tone control on passive Precisions.

After all that rambling, I know I should be safe with the Mesa as I don't push my gear hard, but confirmation/thoughts appreciated?

Cheers doods/doodettes.

[ezbass]

Is the Mesa 800w rating at 2 or 4 ohms and what is the ohm rating of the 2 Aggies combined? Hopefully, the numbers will mean that the Mesa won’t be pushing out its maximum power.

[chris_b]

I'd have done this a slightly different way. Your D800 and an SC or BB2 now and save up for an SM later.

For 2 SL112's I'd try the TH500. IMO they are a perfect match. The D800 will easily drive the SL112's, They are conservatively rated so don't run the amp past about 1 o'clock on the volumes and you should be loud and safe. Probably leave the deep switch alone though. Save up for a third SL112 for the very loud gigs.

Edited August 18, 2018 by chris_b

[karlfer]

1 hour ago, ezbass said:

Is the Mesa 800w rating at 2 or 4 ohms and what is the ohm rating of the 2 Aggies combined? Hopefully, the numbers will mean that the Mesa won’t be pushing out its maximum power.

Mesa has a switch on the back, left 2 ohms, right 4/8 ohms. Both incoming cabs are 8 ohms.

28 minutes ago, chris_b said:

I'd have done this a slightly different way. Your D800 and an SC or BB2 now and save up for an SM later.

For 2 SL112's I'd try the TH500. IMO they are a perfect match. The D800 will easily drive the SL112's, They are conservatively rated so don't run the amp past about 1 o'clock on the volumes and you should be loud and safe. Probably leave the deep switch alone though. Save up for a third SL112 for the very loud gigs.

I was on for a TH500 but it's been trade Chris. I had to give tonight's visitor 1st refusal.

Your suggested vols won't be an issue, if I'd pumped that out through the Super Twin his nibs would have needed psychiatric assistance! I'll possibly need to drive the Aggi's a bit harder. I also thought about the deep switch as I do like to use it, more with jazzes tbh. In the great scheme of things though, out front I sound like the singer mixes it, so bit academic on stage.

Thanks guys, appreciated 

[BassManGraham]

The Mesa subway D800 delivers full power i.e.800W rms into 4 ohm load and/or a 2 ohm load. The 2 ohm switch allows you to link two 4 ohm cabs, and presumably switches in increased impedance so as not to overload output stage.  Personally I would never run an 800w amp into 500w speakers, even if I rarely run gain or master above 1 or 2 o'clock on any head.  I have always tried to add at least 50% to the handling capacity of bass speakers. So I typically run an 800W rms amp into 1200W rms capacity speakers. Sorry if that's not want you wanted to hear. Master volume on the Mesa seems more linear than other amps. I played one only last week in an A/B comparison with a Little Mark 500. Manufacturers power ratings vary considerably. For example a GK MB500 is way louder than a Hartke TX600. Wattage doesn't directly translate into volume or loudness which is dependent on speaker efficiency and cab placement etc etc. In summary it's a minefield. During my aforementioned demo at a major retailer the dude linked the Mesa D800 and LM Tube 500 into a 400w 4 ohm speaker and the speaker was not comfortable with either amp when driven over halfway!

[Phil Starr]

you rally shouldn't have a problem. Amps and speakers are rated by completely differet techniques so their power ratings bear little relationship.

Amps are really simple beasts. They amplify the voltage until they reach the voltage of the power supply and this is their upper limit and the rating of the amp is worked out from there. That's the loudest sound an amp can make

Speakers break in two ways, put too much power in and they will overheat and eventually fry. Alternatively put too much bass through them and they will over extend the cone moving the voice coil out of the magnetic field and maybe even banging it against the back of the magnet. Their testing is simple enough, pass a signal through the speaker increasing the power and eventually it burns out. just below that is it's power rating.

When you play music however you don't pass a continuously high signal through the speaker. You play a note and it decays before you play the next, sometimes you play the notequietly sometimes louder and sometimes there are breaks. All this means that your average power to the speaker is way less than you think. Your loudest sound might need 100W to be clean but the average power for your speakers will be only 2W, they won't over heat. The main threat is bass over extension.

The other way o looking at it is the sound levels. You say you play at modest levels. Well even in a rock band going flat out you won't need to be louder than the drums. You'll usually get something like 99dB/W out of a couple of 12's so 150W will be loud enough to do almost anything other than massive bass boost or drown out the est of the band. In reality your quietish on stage sound means you won't be running at 800W ever.

There's no protection against idiots thrashing their gear with no respect for everyone else on stage or their gear but I don't think you need to worry, just be aware.

I'll use the car analogy. Your car may rev up to 5000 revs but if you thrash it round Brands Hatch never letting the revs drop below 3000 then it won't last long, drive it normally and you'll probably never get anywhere near 5000 revs and never need to worry about the limits. 

[karlfer]

Many thanks chaps .

Superb explanation Phil really appreciated!

[Dragonlord]

Set the amp at 2 ohm operation, this way it will put out 600W at 4 ohm, therefore 300W into each cab. With a little caution you should really be fine.

[deepbass5]

Dragonlord 👍

Thats what I do, always leave it set to 2 ohm, This was explained on the American site by the Guy who worked on the design

I only have two 4 ohm single 12" cabs rated at 350w a piece, run one most of the time low volume gigs and rehearsals, No probs, larger gigs just add the second cab giving me 2 ohms as phil said just be sensible and not over do the bass end.

[karlfer]

22 hours ago, Dragonlord said:

Set the amp at 2 ohm operation, this way it will put out 600W at 4 ohm, therefore 300W into each cab. With a little caution you should really be fine.

 

21 hours ago, deepbass5 said:

Dragonlord 👍

Thats what I do, always leave it set to 2 ohm, This was explained on the American site by the Guy who worked on the design

I only have two 4 ohm single 12" cabs rated at 350w a piece, run one most of the time low volume gigs and rehearsals, No probs, larger gigs just add the second cab giving me 2 ohms as phil said just be sensible and not over do the bass end.

Thanks for that guys, this set at 2ohms sounds a plan, HOWEVER, the 2 cabs are 8ohms, so would present 4 ohms?

Would that make a difference?

I really appreciate everybody's input,

cheers,

Karl.

[Dragonlord]

No, the switch makes it "safe for down to 2 ohm operation" as opposed to "safe for down to 4 ohm operation" with the switch off, it doesn't mean it has to be exactly a 2 ohm load (as it would be with say a tube amp). With the switch off the amp outputs 800W at 4 ohm, with the switch on it outputs 800W at 2 ohm and to achieve that the wattage at higher loads drops. At 4 ohm (which is indeed what your total load will be with two 8 ohm cabs) it becomes around 600W.

Edited August 22, 2018 by Dragonlord

[karlfer]

21 hours ago, Dragonlord said:

No, the switch makes it "safe for down to 2 ohm operation" as opposed to "safe for down to 4 ohm operation" with the switch off, it doesn't mean it has to be exactly a 2 ohm load (as it would be with say a tube amp). With the switch off the amp outputs 800W at 4 ohm, with the switch on it outputs 800W at 2 ohm and to achieve that the wattage at higher loads drops. At 4 ohm (which is indeed what your total load will be with two 8 ohm cabs) it becomes around 600W.

Another superbly helpful response, many thanks😀