Polk Audio LSiC on Yamaha HTR-5750?

[David248]

I just purchased a Yamaha HTR-5750 receiver and I plan to purchase the following Polk Audio speakers to connect to this receiver:
Fronts: LSi7 (4 ohm)
Center: LSiC (4 ohms)
Rears: FXi3 (8 ohms)

My concern here is that the impedance select switch on the back of the HTR-5750 indicates the receiver can drive 4 ohm speakers on the front channels, but only 6 ohm speakers on the center and rear channels. This seems to be the true for all of the HTR series as well as the comparable RX-V series Yamaha receivers. I do not plan on playing the system extremely loud, so I don't think this configuration will be a problem, but I'd like to make sure. Any input is is appreciated.

[20to20K]

I just purchased a Yamaha HTR-5750 receiver and I plan to purchase the following Polk Audio speakers to connect to this receiver:
Fronts: LSi7 (4 ohm)
Center: LSiC (4 ohms)
Rears: FXi3 (8 ohms)

My concern here is that the impedance select switch on the back of the HTR-5750 indicates the receiver can drive 4 ohm speakers on the front channels, but only 6 ohm speakers on the center and rear channels. This seems to be the true for all of the HTR series as well as the comparable RX-V series Yamaha receivers. I do not plan on playing the system extremely loud, so I don't think this configuration will be a problem, but I'd like to make sure. Any input is is appreciated.

My systems plays fine in 2 channel mode for very long periods at high volume.Hope this helps!

Larry

[20to20K]

Something got hosed with my last reply...I'll try again.

I just had a similiar problem today...I tried to connect my Denon 3803 to the following:

Polk LSi 15 - front (4 ohm)
Polk LSi C - center (4 ohm)
Polk Fxi 30 - rears (8 ohm)

After about 20 minutes playing in 5 channel mode the reciever cuts off. I'm not playing it
loud. I call Tweeter. They claim AVRs tend to have a problem playing speakers with mixed
impedences and may shutdown in this configuration. The Denon has no impedence selector. This sounds fishy to me and if it's true sounds lame on Denon's part.

If it is true (I will continue to research) it appears I may need to buy a seperate amp to
drive the 8 ohm rears. This is still cheaper than upgrading the rears to the $900 LSi FX's.

Hope this helps.

Larry

[David248]

Thats a bit concerning. Has anybody had any experience with mixed impediance on a Yamaha receiver? If this also applies to Yamaha I'll have to rethink my speaker choice. I submitted a question on Yamaha's website, so I'll have to see what they say.

Something got hosed with my last reply...I'll try again.

I just had a similiar problem today...I tried to connect my Denon 3803 to the following:

Polk LSi 15 - front (4 ohm)
Polk LSi C - center (4 ohm)
Polk Fxi 30 - rears (8 ohm)

After about 20 minutes playing in 5 channel mode the reciever cuts off. I'm not playing it
loud. I call Tweeter. They claim AVRs tend to have a problem playing speakers with mixed
impedences and may shutdown in this configuration. The Denon has no impedence selector. This sounds fishy to me and if it's true sounds lame on Denon's part.

If it is true (I will continue to research) it appears I may need to buy a seperate amp to
drive the 8 ohm rears. This is still cheaper than upgrading the rears to the $900 LSi FX's.

Hope this helps.

Larry

[anamorphic96]

It sounds like your in the same boat as the other guy. You guys really need to look at exteranl amps to drive those Polks. The impedance selector swich will actually degrade the sound in that it restricts the amout of current to the speakers so the amp will not overload. Try and find a used amp to drive those Polks. Check Rotel, Parasound, or Adcom. Most receivers have a hard time driving 4ohm loads. They just cant deliver enough current to do the job properly. As I stated to 20to20k the receiver will drive them but not with any type of real punch or authority. Try listening to the Polks at your dealer with a dedicated amp designed for 4ohm loads. Your speakers will sound far better.

P.S. The Polk LSi series kicks ass. They just need alot of current to sound right.

Cheers,
Glenn

[spacedeckman]

Mixed impedances aren't going to create any specific problem, the real problem will be either with the power supply not having enough "oomph", or the output devices/heat sink not keeping up.

As long as you are expecting reasonable volumes, start with the switch in 8 ohm mode. If you have problems, switch to the 4 ohm mode. Please turn it off before making the switch over. All the switch does is limit the voltage to the output devices to keep them within their Safe Operating Area (SOA), the lower impedances will increase current draw, offsetting most of what would be "lost".