Bridging Polk RTI 12's with a Denon 3805

[Johnny Canuck]

Hey guys....need an opinion and maybe some help. Buckeye, hopefully you can step in here as well and give me a hand as you seem to be the resident Polk expert

I found a used NAD 2200 like the one I have now. Presently i am using the NAD to run my lows of the towers and my Denon to run the highs/mids. I do notice a big difference when my speakers are on large, and a small difference when they are on small. I turn off my sub and set the fronts to large and I can really hear it, especially when i turn up the bass with the EQ.

My question is, will i have any benefit getting this other NAD amp and bridging them to my Polks? The guy at the store told me I would see no benefit at all. I usually have my speakers set to small. Towers are really a waste of money when i do this I know, but would these inefficient Polk RTI 12's benefit from another amp in my current set up? When I tried the NAD on the Polks full range, they seemed too bright so I just put the NAD on the lows. I don't really need any more volume than I have. i just hear these Polks "open up" with massive power, even at low levels. I have constantly been trying to tame the brightness with them as well. And this amp used is only $200.

I am thinking of trying to bridge one side with the NAD I have now and see how it sounds before buying the other. Is this wise?

Thanks everyone..

JC

 

[MacManNM]

Hey guys....need an opinion and maybe some help. Buckeye, hopefully you can step in here as well and give me a hand as you seem to be the resident Polk expert

I found a used NAD 2200 like the one I have now. Presently i am using the NAD to run my lows of the towers and my Denon to run the highs/mids. I do notice a big difference when my speakers are on large, and a small difference when they are on small. I turn off my sub and set the fronts to large and I can really hear it, especially when i turn up the bass with the EQ.

My question is, will i have any benefit getting this other NAD amp and bridging them to my Polks? The guy at the store told me I would see no benefit at all. I usually have my speakers set to small. Towers are really a waste of money when i do this I know, but would these inefficient Polk RTI 12's benefit from another amp in my current set up? When I tried the NAD on the Polks full range, they seemed too bright so I just put the NAD on the lows. I don't really need any more volume than I have. i just hear these Polks "open up" with massive power, even at low levels. I have constantly been trying to tame the brightness with them as well. And this amp used is only $200.

I am thinking of trying to bridge one side with the NAD I have now and see how it sounds before buying the other. Is this wise?

Thanks everyone..

JC

I'd try bridging it, why not? I would think you aren't going to hear a whole lot of improvement in the quality but, you are going to take some stress off of the Denon's PS. Have you tried dialing your crossver down to 40-50 Hz? I would think you would get the best sound letting the polks with the amp(s) play say 45 and up, with the sub playing 45 and down. You could always run the towers bi-amped, with one amp per tower. This is going to let the amps run a little cooler. Thereby extending their life.

 

[j_garcia]

Those speakers aren't inefficient, they are low impedance. That tends to cause the amp to work a bit harder. I'd have to agree with what MacManNM said, single amp per speaker, one channel for each set of posts. The NAD amps should have no problem at all with the 4 Ohm load. If you bridge, while the amps can most likely handle it, they will be working a lot harder to do basically the same thing. If you are not getting enough power to them, that would be one thing, but I doubt that is a problem with your current setup. There is a point at which you don't need any more power, and adding more power than what is needed, won't make any noticable difference because the speakers can't use it.

 

[Buckeyefan 1]

I don't think you need another amp. Your issue is brightness. Why not invest in a eq you can put between the receiver and amp? That way you can adjust the mids and highs from the receivers preouts before they enter the power amp (with your new eq). Use the amp to drive the mids and highs, and use the receiver to drive the woofers. The triple woofers are 8 ohms when unstrapped, so 120 watts each should get them moving from the receiver, and I know you've got a great sub to back them up.

 

[Johnny Canuck]

Does bridging deteriorate SQ? How does one wire it? I think i am going to buy this other NAD. I will try bridging and if it does not work, I can use it in another room. $200 is a good deal.

 

[Spiffyfast]

I don't think you need another amp. Your issue is brightness. Why not invest in a eq you can put between the receiver and amp? That way you can adjust the mids and highs from the receivers preouts before they enter the power amp (with your new eq). Use the amp to drive the mids and highs, and use the receiver to drive the woofers. The triple woofers are 8 ohms when unstrapped, so 120 watts each should get them moving from the receiver, and I know you've got a great sub to back them up.

Now thats a great idea, that way you would get what your wanting wth bi-amping and allow you to tone down the brightness.

 

[AVRat]

The Rti 12s would appear to be comprised of the Monitor 40 system with the addition of the woofer section. The Monitor 40s have a power rating of 125W, while the Rti 12s are rated at 500W. Given this, it would appear that the woofer section handles 375W. At the ratio of 1:3, and with the Denon providing 120W, it looks like you would need an amp rated at about 360W for the woofer section to provide proper balance. What is the bridged spec on the NAD? Or into 4 ohms? The price is right!

One amp bridged to each speaker should work nicely.

 

[Buckeyefan 1]

The Rti 12s would appear to be comprised of the Monitor 40 system with the addition of the woofer section. The Monitor 40s have a power rating of 125W, while the Rti 12s are rated at 500W. Given this, it would appear that the woofer section handles 375W. At the ratio of 1:3, and with the Denon providing 120W, it looks like you would need an amp rated at about 360W for the woofer section to provide proper balance. What is the bridged spec on the NAD? Or into 4 ohms? The price is right!

One amp bridged to each speaker should work nicely.

I think the RTi12 uses the CSi3 for the top end, which allows 180 watts of input, instead of the 125 watts on the monitor 40. The RTi12, in other words, requires HUGE power, so I'm in agreement with AVRat that a second amp can't hurt, but I'm still up in the air on how to tame the brightness without a separate eq (unless the 3805's internal eq does the job).
http://www.polkaudio.com/homeaudio/specs/individual/center/csi3/

 

[AVRat]

Specs from manual

NAD 2200
Bridged Mode
Continuous output power into 8Ω ... 400W (26dBW)

IHF Dynamic headroom at 8Ω +5dB
IHF dynamic power (maximum short term power per channel)
8Ω ... 1.2kW (31dBW)
4Ω ... 1.6kW (32dBW)

Currently, you are underpowering the woofer section with only 100W/channel. By bridging the amps, you will have more than enough headroom to power the speakers on their own (no bi-amping).

The manual: http://207.228.230.231/info/NAD_2200.pdf

How do I bridge an NAD power amplifier?

Always make sure, first, that the amplifier is a bridgeable model. (The instruction book for the amplifier will make clear if it is.) The switch for bridging is usually located on the rear panel of the amplifier, and there is an LED on the front panel that illuminates when the bridge mode is selected. Before making or changing any connections on your amplifier be sure to remove AC power first, by switching the POWER switch to the OFF position, and unplugging the unit from the wall socket. To bridge, move the bridging switch to the MONO position and connect the audio cable you will be using for the amplifier's mono operation to the LEFT input of the amplifier. The speaker's negative cable (- or black) is then connected to the LEFT positive (+ or red) amplifier speaker output and the speaker's positive cable is then connected to the RIGHT positive (+ or red) amplifier speaker output. Be sure the speaker(s) being used present a load to the amplifier that is a minimum of 8 Ohms. Double check your connections before switching the amplifier back on.

 

[AVRat]

Once you get the 2 NADs into the system, I would suggest some changes to the system settings since you listen more to music. Set the 12s to large, the rest to small and set the X-over to 80Hz. OR Set all to small and set the X-over to 60Hz. I know you really want to get the best quality out of your system that you can. It might just take more tweaking to get it right.