Help with amp selection polk LSIM speakers

[PENG]

Let's begin with the Polks Specs:

Polk specs: Nominal 8 Ohms

That is not as revealing as the SoundAndVision test reports:

Frequency response

• tower 34 Hz to 20 kHz ±4.6 dB
• center 46 Hz to 20 kHz ±3.6 dB
• surround 65 Hz to 20 kHz ±5.3 dB
• subwoofer 34 to 450 Hz ±3 dB

Sensitivity (SPL at 1 meter/1 watt)

• tower 86.5 dB
• center 87.7 dB
• surround 87.8 dB

Impedance (minimum/nominal)

• tower 2.8/5 ohms
• center 3.5/5 ohms
• surround 4.0/5 ohms

Read more at https://www.soundandvision.com/content/test-report-polk-audio-lsim-speaker-system-page-3#h23gT460K9du46iu.99

Minimum of 2.8 Ohms is quite a bit different than nominal 8 Ohms. When manufactures provide ony "Nominal Impedance", I assume this is not the impedance
Your going to need a real amp that is stable below 4 Ohms to drive these speakers.

It may also be worthwhile reading about the NCore amps by designer Bruno Putzey:



I am currently comparing the AT4002 and AT522NC at home. Driving the Revel M20 bookshelf speakers, the AT4002 makes strings sound exquisite, while the AT522NC is more forward with great detail in the high-end. I have not had a chance to audition them on the Salon2's. The difference I hear may have something to do with the M20's so it may not be universal. To put it into context, I sometimes forget which amp I am listening to when starting up the system. For heat and weight, the AT52xNC amps cannot be beat. Bass reproduction is also excellent.

- Rich

I was always suspicious of the real impedance/sensitivity characteristics of those big LSIM 707s, that's why I suggested the AT543NC. The part about the designer's comments I would politely ignore, well to a point only as I don't doubt a good part of it is valid/real (such as the different distortions profile/characteristics), but a good part of it is subjective. If the Halo amp that he is considering has enough juice for his speakers in his room at the spl (including peaks) he needs, I would still expect no audible difference in a truly level matched blind tests. That is not to say there is no subtle differences. If I am facing the decision between the two today, I would go with the AT522 or AT542NC.

 

[RichB]

I was always suspicious of the real impedance/sensitivity characteristics of those big LSIM 707s, that's why I suggested the AT543NC. The part about the designer's comments I would politely ignore, well to a point only as I don't doubt a good part of it is valid/real (such as the different distortions profile/characteristics), but a good part of it is subjective. If the Halo amp that he is considering has enough juice for his speakers in his room at the spl (including peaks) he needs, I would still expect no audible difference in a truly level matched blind tests. That is not to say there is no subtle differences. If I am facing the decision between the two today, I would go with the AT522 or AT542NC.

I think the AT52xxNC amps may surprise you. A Halo amp is a great choice as well. I suspect the Parasound and AT4002 to be very similar, with the ATI quieter at the speaker. The AT4002 and AT522NC are surprisingly distinguishable (driving the M20's directly from the UPD-205). Gains were also quite a bit different +3 for the AT522Nc, I am still investigating that. I have yet to compare them driving the Salon2's and to measure the sweeps on both speakers, so it's early yet.

When the time comes to replace my Sunfire amp (driving M20's and C20), the AT52xNC is at the top of the list. Sound quality, heat, and reliability are of major concern in this installation.

I have an Onkyo AVR driving the system and in this case, I will stay with an AVR because this is a vacation home that is also rented. Should the amp every give way, there is always the option of switching the AVR amps, while a replacement is ordered.

- Rich

 

[PENG]

I think the AT52xxNC amps may surprise you. A Halo amp is a great choice as well. I suspect the Parasound and AT4002 to be very similar, with the ATI quieter at the speaker. The AT4002 and AT522NC are surprisingly distinguishable (driving the M20's directly from the UPD-205). Gains were also quite a bit different +3 for the AT522Nc, I am still investigating that. I have yet to compare them driving the Salon2's and to measure the sweeps on both speakers, so it's early yet.

When the time comes to replace my Sunfire amp (driving M20's and C20), the AT52xNC is at the top of the list. Sound quality, heat, and reliability are of major concern in this installation.

I have an Onkyo AVR driving the system and in this case, I will stay with an AVR because this is a vacation home that is also rented. Should the amp every give way, there is always the option of switching the AVR amps, while a replacement is ordered.

- Rich

We already know that you have much more discerning hearing than me. So the fact that you like that class D amp so much, give me more confidence to try it out if I can get good enough price for either the A21 or the 4BSST. I may still have to consider the Benchmark amp, or that Lyngdorf pure digital amp that comes with RoomPerfect though.