Bridging Marantz MA500's

B

breal74

Audiophyte
I purchaced 5 Marantz MA500 amps and am looking to bridge two per speaker on my Polk RTi12s, and one for my center channel. Has anybody bridged these amps before? If so, did you have any troubles with them. The RTi12's are 8 ohm speakers, so I don't see that as a problem. Thanks for any input. It is greatly apperciated!
 
TLS Guy

TLS Guy

Audioholic Jedi
I purchaced 5 Marantz MA500 amps and am looking to bridge two per speaker on my Polk RTi12s, and one for my center channel. Has anybody bridged these amps before? If so, did you have any troubles with them. The RTi12's are 8 ohm speakers, so I don't see that as a problem. Thanks for any input. It is greatly apperciated!
The MA 500s are mono blocks and you can NOT bridge mono blocks. If you try you will blow them instantly and they will be boat anchors.

Next The RTi12s are rated 8 ohm by the manufacturer but they are four ohm as you can surmise from the driver layout. In fact their impedance drops below four ohms and they are a difficult load.

Manufacturers generally are dishonest about impedance ratings and take an average of the impedance curve, which is bogus and means nothing.

A general rule of thumb is actually minimal impedance plus 10%, which put yours actually a little below four ohms.
 
H

hewhoisbill

Enthusiast
Hi Breal,

Below is a link to a diagram showing how to bridge two of the MA500s; despite the fact that they are mono blocks they were designed to be bridged.

http://www.avsforum.com/avs-vb/showthread.php?t=1121946

Before doing so I would probably dive a bit deeper into the impedance concerns TLS Guy has with the Polk's as the RTi12 and RTIa9 are both notorious for loving tons of power from a good amp. My understanding is that at some frequencies the impedance them dips quite low, but I don't know which ranges as my Google-fu appears to be weak at the moment.

One quick question though: is one MA500 not providing the volume you crave in your room? If one isn't being constantly challenged, bridging may not be worth it especially in light of the impedance concerns.

Cheers,

Kyle
 
TLS Guy

TLS Guy

Audioholic Jedi
The MA 500s are mono blocks and you can NOT bridge mono blocks. If you try you will blow them instantly and they will be boat anchors.

Next The RTi12s are rated 8 ohm by the manufacturer but they are four ohm as you can surmise from the driver layout. In fact their impedance drops below four ohms and they are a difficult load.

Manufacturers generally are dishonest about impedance ratings and take an average of the impedance curve, which is bogus and means nothing.

A general rule of thumb is actually minimal impedance plus 10%, which put yours actually a little below four ohms.
I managed to download a manual for that amp from Hi-Fi engine. There is an interconnect for bridging. However impedance is 8 to 16 ohm. That rules out using bridged amps with your speakers.

I have no phase curve with impedance for those speakers, but it has a passive crossover in the 100 Hz range, never a good idea. I would suspect the phase angles are highly adverse, that usually goes along with that approach, as well as many other ills. So I would bet that at some frequencies those speakers look close to a short circuit at some frequencies.

Bridging is something I never recommend unless you have good service gear.

Each amp is responsible for just +ve defelctions or just -ve deflections.

You really have to tweak amps with test gear and make sure their gain structure is identical. Small errors in gain result in very unpleasant crossover distortion.

So apart from the low impedance intolerance which leads to amps blowing in bridged format, there are a lot of other disadvantages, especially related to the fact that the amps are seldom exactly identical, which they have to be as a bridged pair.

There is far too much nonsense and enthusiasm around bridging.

My advice is always, if you need more power buy bigger amps. That is a much better solution.
 
j_garcia

j_garcia

Audioholic Jedi
These amps are designed to be bridged together. Having said that, and just like bridging any amps, they are no longer stable at lower impedance when bridged. Have you tried them as singles with your speakers yet? How have you come to the conclusion that you need to bridge them? I also don't think this is a good idea for these speakers, and I agree completely that if you have determined you need more power then a different amp is what you need.
 
B

breal74

Audiophyte
j garcia, I see that you have an Emotiva XPA-3 with a Marantz SR-8300. How does the sound of the Emotiva compair to the warm sound of the SR? I have been very curious about the sound of Emotiva and Outlaw amps. I have the SR 5005 and love the sound of it. That is why I picked up the MA 500's, but was thinking of dumping them and picking up some of their mono blocks. Thanks for your input!
 
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j_garcia

j_garcia

Audioholic Jedi
I used to own the MA500s as well, with the same speakers. The Emotiva is not quite as warm as the Marantz amps; it is very neutral IMO and simply doesn't get in the way of the sound. It does what it is supposed to do: amplify and it sounds just fine doing it. My speakers are 4 ohm and when I moved to this place with a larger room I needed something more powerful to fill it. I have not heard the Outlaw external amps, but the receivers had a very nice sound to them, so I wouldn't question their ability either.
 
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