13th May 2012
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#1 | | Gear interested
Joined: May 2012
Posts: 4
Thread Starter | Bridged Mode Amp + Nearfield Monitors Help
Hey guys, i have an issue.
I own a set of old Alesis Monitor One's (mkI) passive, they can handle 120watts RMS each @4ohms. ATM im using Goodmans Delta 800A, and it's an old and noisy. I've decided that an Alesis RA300 would be ideal amp (150watts per side)that's in my price range. Only problem is, they're discontinued, and i wanted something brandnew. However, the RA150 is still available, it only gives 75watts rms @ 4ohms or 45@8ohms though, unless it's bridged, in which case it gives 150watts @ 8ohms, can i just buy two of these and use my 4ohm speakers? Iv'e already googled this, and generally, you shouldn't power a 4ohm speaker with an amp thats designed for an 8ohm circuit, but the fact that its in bridged mode my change that somehow, this amp has the ability to provide 150watts rms at 4 ohm's does it not?
Thankyou for reading
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14th May 2012
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#2 | | Moderator
Joined: Jan 2004 Location: New Zealand/Switzerland/guitar case
Posts: 8,944
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No you can't use speakers lower than the stated minimum, you will fry the amp.
Assuming 8 is the minimum in bridged mode, because you didn't actually say that.
matt
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14th May 2012
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#3 | | Gear interested
Joined: May 2012
Posts: 4
Thread Starter |
Hello, thanks for the reply, as you can see, the link i provided does show that the minimum in bridged mode is 8ohm. Anyhow, i have decided to get the amps and use them with the monitors, il just make sure i keep the gain down on the amp.
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14th May 2012
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#4 | | Lives for gear
Joined: Dec 2007
Posts: 1,651
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If 8 ohms bridged is the spec, then going below that will damage the amp by running a 4 ohm speaker. Your amps life will be short.
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15th May 2012
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#5 | | Moderator
Joined: Jan 2004 Location: New Zealand/Switzerland/guitar case
Posts: 8,944
| Quote:
Originally Posted by shnabz  Hello, thanks for the reply, as you can see, the link i provided does show that the minimum in bridged mode is 8ohm. Anyhow, i have decided to get the amps and use them with the monitors, il just make sure i keep the gain down on the amp. | The problem is kind of like blowing through a straw.
If you blow through a normal drinking straw, you get a bit of resistance, which makes it easy to blow through.
But if you blow through a 4 inch diameter pipe, there won't be as much resistance and you will wear yourself out in no time.
I would advise seeing if you can return the amps, and look for something else. They will work, but it will lead (possibly quickly) to trouble. It will also not be loaded correctly, so it will not be producing the quality sound that it should. Either that or just use one amp, you may find that is enough.
matt
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15th May 2012
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#6 | | Gear interested
Joined: May 2012
Posts: 4
Thread Starter | Quote:
Originally Posted by matt thomas The problem is kind of like blowing through a straw.
If you blow through a normal drinking straw, you get a bit of resistance, which makes it easy to blow through.
But if you blow through a 4 inch diameter pipe, there won't be as much resistance and you will wear yourself out in no time.
I would advise seeing if you can return the amps, and look for something else. They will work, but it will lead (possibly quickly) to trouble. It will also not be loaded correctly, so it will not be producing the quality sound that it should. Either that or just use one amp, you may find that is enough.
matt | I have not actually purchased them yet so no need to return, i will probably buy just one and load it correctly and see if its loud enough. I like the analogy of blowing through a straw, however, would turning the input gain down not help? Because the amp will not be drawing more power than it can handle?
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15th May 2012
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#7 | | Moderator
Joined: Jan 2004 Location: New Zealand/Switzerland/guitar case
Posts: 8,944
| Quote:
Originally Posted by shnabz I have not actually purchased them yet so no need to return, i will probably buy just one and load it correctly and see if its loud enough. I like the analogy of blowing through a straw, however, would turning the input gain down not help? Because the amp will not be drawing more power than it can handle? | If you do that it won't be so prone to over heating, but it still won't be controlling the speakers correctly
matt
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17th May 2012
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#8 | | Lives for gear
Joined: Nov 2011 Location: Vienna
Posts: 1,337
| Quote:
Originally Posted by shnabz I have not actually purchased them yet so no need to return, i will probably buy just one and load it correctly and see if its loud enough. I like the analogy of blowing through a straw, however, would turning the input gain down not help? Because the amp will not be drawing more power than it can handle? | its still possible that the amp can burn-out!!
the impedance is not directly connected to the gain on the amp....
if you dont give too much gain, it wont burn soo quick, but after a while it will..
btw i doubt it will give you a more or less correct signal through the speakers!
cheers
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