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I want to use 2 amps with one bass....HELP...please...


bob_atherton
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Hi. I want to run two Barefaced 2x10 cabs with a Markbass LMIII for the top cab, and a Mesa WD800 for the bottom cab. The Markbass on its own gives me lovely articulation and sounds just right, but, looses the heft of using the Mesa on its own.

I want to also run both cabs at 4ohm to give me loads of headroom from the two amps. I thought this would be pretty straightforward but it would appear to be a bit of a minefield with reference to phase, ground loops etc. I never want to run just one cab at once so I guess I dont really need an ABY box, or do I..? Any help is very seriously appreciated. Thanks, Bob 

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I'd just run one amp that does what you want it to all by itself.

Quote

A crossover may also be worth looking into, to send the highs to the Markbass and lows to the Mesa.

That's valid when you have one cab that's optimized for the lows and one optimized for the highs, as in a PA sub and main, but not with two identical cabs.

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2 hours ago, bob_atherton said:

...I thought this would be pretty straightforward but it would appear to be a bit of a minefield with reference to phase, ground loops etc. 

 

Do you know you'll have these issues?  

 

I've ran several amps over the years doing what you say; for me it was using 1 amp as the tone shaping with other amp just as a slave to drive other cab(s).  

 

In fact I did this the other week just for fun to try a few amp/cab combinations out.  No issues with phase or ground loops by taking a line out from my valve Handbox amp (driving the 2 x 112 cabs) into the TC amp driving another 115 cab.

 

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Thanks for all the advice guys. I do have a HPF and a LPF. The point of running two identical cabs is to get the best integration between them. Back in the day I used to use my Rickenbacker 4001 with 'Ricosound' and put the bridge pickup through an H&H 100 watt into two 2x12 cabs and my neck pickup into a Hiwatt 100 and a Hiwatt 2x15 cab.  It sounded great and gave me quite a Chris Squire sort of sound. We also had a couple of roadies..!

 

What I want now is the capability to tweak the sound from both cabs to suit the venue. Both amps sound quite good but neither is perfect. I suspect that by using my suggested setup it will give me the best of both in a very portable setup. By using the cabs at 4ohm each it will give me a 1300 watt rig. Way too much power but with great headroom. I'll sort it out one way or another and let you know how it works out. Thanks again. Bob

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Hi Bob,

 

I use a couple of different rigs.

 

If the venue is large enough I bring the SVT-4 pro with Barefaced Big Twin II.

When I need tiny footprint I stack up two Trace Elliot 2x8" cabs and use a TC RH750 instead. I love its flexibility and built in tuner but class D amps are not for me.

That amp sounding pretty sterile by itself made me begin shaping my tone on the pedalboard instead, adding some valve heft at will.

For this I use either a Two Notes Le Bass preamp (which can also blend in valve overdrive) or/and an EHX Black Finger compressor.

This makes the TC amp sounds just as hefty as my SVT-4 pro and I can switch the hefty valve bit off whenever I want a modern ultra clean and articulate sound.

 

Just saying... Maybe you can fix it using just one amp.

 

Cheers, Marco

 

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9 hours ago, DiMarco said:

Hi Bob,

 

I use a couple of different rigs.

 

If the venue is large enough I bring the SVT-4 pro with Barefaced Big Twin II.

When I need tiny footprint I stack up two Trace Elliot 2x8" cabs and use a TC RH750 instead. I love its flexibility and built in tuner but class D amps are not for me.

That amp sounding pretty sterile by itself made me begin shaping my tone on the pedalboard instead, adding some valve heft at will.

For this I use either a Two Notes Le Bass preamp (which can also blend in valve overdrive) or/and an EHX Black Finger compressor.

This makes the TC amp sounds just as hefty as my SVT-4 pro and I can switch the hefty valve bit off whenever I want a modern ultra clean and articulate sound.

 

Just saying... Maybe you can fix it using just one amp.

 

Cheers, Marco

 

Hi Marco

 

Thanks for your reply. What I'm trying to achieve is a one size rig fits all gigs situation. I always take a spare amp and two cabs to any gig, along with spare bass and cable. 

It occurred to me that rather than have the MB LMIII sitting backstage, just in case, I should use it in the rig. I have found that the Bareface 2x10's require very little EQ to get me in the zone sound wise. The cabs let you know what the amp's tonal signature is much better than my old Markbass cabs did. With this in mind I have now ordered a 1x10 from Bareface and will use that on top of the 2x10 for small gigs and two 2x10's for larger gigs. I can set the 2x10's to 4 ohm and get the full power from each amp. It should, in theory, give me huge amounts of power and flexibility. I too use a pedal-board with a MB compressor, a HP/LP filter and a Tone Hammer pre. I do fantasize over getting another Hiwatt DR103 but my back is the voice of reason. It would also look a bit odd balancing on top of a vertical 2x10 cab!  

 

Cheers, Bob

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I am a big fan of a split rig when it suits the tonal needs.

I reckon it is only needed in 1 situation - where the FX and drives are extensive and it's easier to EQ a separate clean amp underneath rather than have 1 cab do it all.

 

So 2 outputs from the bass, or a splitter box then into different paths.

 

1: The drives and FX into an amp with some of the low end rolled off. Loads of mids and high end clank.

2: Into a different amp & cab with the treble and some of the mids rolled off. Like a reggae dub sort of thing.

 

The important bit is compression. Different amps and using drives means the note decay in each rig will be very different. The clean low amp will decay far more quickly than the other. So compressors on each to make sure the note delays at the same time is important to make it sound like 1 rig and not 2 bassists.

 

It takes a lot of experimentation to get the note decays to match. When it does, it's lovely.

 

All the FX / drives etc stand out well and they never affect the low end at all. No cross-overs needed, just EQ each amp separately. They will sound terrible in isolation and awesome when combined.

 

However, after using a rig like that for 20 years my overall conclusion is that unless you need that variety of FX and drives it is just unnecessary. Modern bass drives have very good clean blends for a start, the bass drive market is now saturated with options.

 

Unless you are duplicating Billy Sheehan's sound or playing a load of Muse songs in your set then you don't need it and it's a waste of time. I say that as a massive fan of that sound.

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I've just had a look at the cab specs. Switchable 4 or 12 ohms.

 

The Mesa WD800 will run at 2 ohms - there's a little switch on the back.

 

So just use the cabs in 4ohm mode giving a total of 2ohms and make sure the amp switch is set correctly. Full power and headroom available.

 

Job done.

 

 

If the amp fails then use the Mark Bass and flick the cabs to 12 ohms each giving 6 ohms total. Impedance is not a static thing anyway so you really won't notice that much difference between 4ohms and 6 ohms. Just turn it up a little if you need to and get to the end of the gig.

 

 

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5 hours ago, fretmeister said:

I've just had a look at the cab specs. Switchable 4 or 12 ohms.

 

The Mesa WD800 will run at 2 ohms - there's a little switch on the back.

 

So just use the cabs in 4ohm mode giving a total of 2ohms and make sure the amp switch is set correctly. Full power and headroom available.

 

Job done.

 

 

If the amp fails then use the Mark Bass and flick the cabs to 12 ohms each giving 6 ohms total. Impedance is not a static thing anyway so you really won't notice that much difference between 4ohms and 6 ohms. Just turn it up a little if you need to and get to the end of the gig.

 

5 hours ago, fretmeister said:

 

I've spent most of the day testing and tweaking and I'm very pleased, and surprised , with the results.

If I run my Mesa at 2 ohm into the cabs set to 4 ohm then it sounds a lot more wooly and thick compared to the cabs set to 12 ohm and the amp to 4 ohm, at the same perceived volume. The later sounds more articulate and open.

 

At this point I had the cabs daisy-chained with speakon to top cab from amp and then connected to bottom cab from top cab with speakon.

 

I then connected both cabs direct from the amp, no daisy-chain.  This improved things again. I have absolutely no idea why but it sounded clearer and tighter. The two cabs set like this give me loads of volume and headroom. I have band practices tomorrow and Friday and first gig, outdoors, with the new cabs on Sunday.

 

I'm hoping that this configuration will work out well, we will see.

The two things that have baffled me are why does the amp sound so different and worse set to 2 ohms? and why, after decades of daisy-chaining my speaker cabs does it sound better with both cabs connected directly to the amp? 

 

Thanks again guys for all the great help. I now think that just the Mesa WD800 will be my only amp with the MB LMIII as my back up/spare. Happy days...! 

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The only way they'd sound different direct versus daisy chained is if the cables are seriously undersized. All cables have some voltage drop, and when you daisy chain that drop is higher compared to when each speaker has its own lead to the amp. But with the length and gauge of correctly sized speaker cables the voltage drop in either configuration should be virtually unmeasurable, let alone audible.

 

I keep seeing these references to getting more headroom with lower impedance loads. I imagine the reason for this notion is the higher power output into a lower impedance load. That notion should be divested. What happens with a lower impedance load is that for the same voltage output from the amp you get more SPL from the speaker. That's all well and good, but you also draw more current from the amp, so from the standpoint of current you don't have more headroom, you have less.

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To the OP: Have a look at Tecamp Bonafide and other true two channel bass amps. Eden and SWR did them, plus others no doubt. There’s a Bonafide for sale at bassdirect I think.

 

Also, the orange bass butler preamp is designed around a similar idea.

  

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On 07/09/2021 at 07:05, Bill Fitzmaurice said:

I keep seeing these references to getting more headroom with lower impedance loads. I imagine the reason for this notion is the higher power output into a lower impedance load. That notion should be divested. What happens with a lower impedance load is that for the same voltage output from the amp you get more SPL from the speaker. That's all well and good, but you also draw more current from the amp, so from the standpoint of current you don't have more headroom, you have less.

I know what you mean but I doubt too many others 'speak enough engineer' to get it.

 

If I may comment in simpleton and you can correct as you feel:

 

Getting all the power out of the amp is a fool's errand. Most often ( and surely the OP is in this boat ) the amp will have plenty enough power to drive 'half' the minimum load to where the cab is giving its all.

 

Headroom is the potential to add more power to get more volume.

 

Lowering the impedance by itself is never possible.

 

If you are adding more speakers then you are getting more efficiency. Well and good with any amp so long as impedance limits are respected. Output goes up.

 

Flipping switches to rearrange the cab impedance doesn't do squat when the amp can put out the full power handling either way.

 

Swapping to drivers with half impedance only means it takes half the voltage to move them but the current gets doubled at the same time. Do the sums and it's the same power before they go bang.

 

Fish hook though. The half impedance ones are usually built a bit tougher to cope and that makes them less loud per volt applied.

 

The only reason to be concerned about getting max watts out of your amp is when it's under powered in the first place. Not 800w Mesa's.

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There should be no difference between connecting from amp to cab to cab versus amp to cab x 2. If there is a difference, either the cable is absurdly undersized or there is a defective termination.

 

One problem with driving any 4 ohm 210 with a Subway amp is that the amp is capable of overdriving (and likely damaging long term) every cabinet that I have ever tested. The woolly sound from the 210 might be due to this.
 

Another possible and even likely cause is if the cabinet is really 12 ohms with the drivers switched into series mode, it will be ~3 ohms when the drivers are switched into “4 ohm mode”. If the amp is set to 8/4 ohm mode, it will try to deliver over 1000 watts the the cabinet and internal protection circuitry will limit this power which will not be a good sounding result. The amp should be set to the 2 ohm position, which will limit the power to ~600 watts into a real 4 ohm load, and ~800 into a 3 ohm load. 
 

Running all cabinets in parallel from the amp will result in a load of ~1.5 ohms which is NOT an appropriate or safe load.

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For flexibility I've always used a small mixing desk, currently an old Mackie with 4 high impedance inputs. I plug my basses into the channels, my pedal board is connected to the send and return, and I've got enough outputs from the desk to run to several rigs if necessary plus a DI for the main PA if needed. That also means my signals are buffered, impedances are sorted and whichever bass I use, the pedal board and the outputs get a consistent level. 

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  • 2 weeks later...

Hi Guys. After much testing, gigs, and playing in three different bands I have a happy result.

On the advice of Kirby, our guitarist, I bought a Tonebone ABY unit. I have this connected to the amps. The Mesa going to the bottom cab and the LMIII going to the top cab. The LMIII needed polarity change on the pedal. Both cabs set to 4ohm.

The result is an incredibly versatile rig that gives me exactly the tone and power that I'm after regardless of the venue. I could not be more pleased. I don't have the rig playing that loud but the versatility of tone and the fact that if any amp or cab craps out at a gig I can keep on playing is priceless. 

I have now ordered a single 1x10 cab from Barefaced to use as the top cab at smaller gigs.

I am seriously pleased with the set-up.

Thanks again for all your kind advice.

Cheers, Bob

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On 20/09/2021 at 10:30, bob_atherton said:

Hi Guys. After much testing, gigs, and playing in three different bands I have a happy result.

On the advice of Kirby, our guitarist, I bought a Tonebone ABY unit. I have this connected to the amps. The Mesa going to the bottom cab and the LMIII going to the top cab. The LMIII needed polarity change on the pedal. Both cabs set to 4ohm.

The result is an incredibly versatile rig that gives me exactly the tone and power that I'm after regardless of the venue. I could not be more pleased. I don't have the rig playing that loud but the versatility of tone and the fact that if any amp or cab craps out at a gig I can keep on playing is priceless. 

I have now ordered a single 1x10 cab from Barefaced to use as the top cab at smaller gigs.

I am seriously pleased with the set-up.

Thanks again for all your kind advice.

Cheers, Bob

 

That isn't Kirby of Stretch fame is it?

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