LSiM 707s impedence
myhikingboots
Posts: 8
This post with a different title was first posted in the audio section of AVS Forums:
Refurb Marantz MM-7055 from Accessories4Less
A couple of months ago I purchased a pair of Polk LSiM 707's and a 706 center channel that were being clearance from Adorama. I quickly found out that my avr was woefully lacking. I then purchased a new Marantz SR 6014 for processing and powering the back and height channels. I also picked up the 5-channel Marantz MM-7055 to power the front stage from accessorie4less via Amazon. I used four channels to power the 707s in Bi-amp and the other channel was for the center. Before even hooking up the 707s in that configuration I had the center playing at very low volume for a few minutes when the refurbed MM-7055 went into protect mode. My only thoughts were that I had gotten a dud or possibly not getting enough ventilation. Before using it again I purchased an AC Infinity air cooler that sits on top of the amp and vents air out the back. I guess this helped some because I could sometimes watch TV/Blu-ray without a problem, but other times it would go into protect mode after it being on for less than an hour.
I went through some troubleshooting over the course of a couple of days through email with the tech at Accessories4less but the problem kept reoccurring. The final straw was one night I turned on the amp and it started with the internal fan blowing and after 5 minutes of watching tv at low volume it went into protect. I emailed the tech and he starting asking about the speakers and then he said that the Polks were too power hungry. I told him they ran fine on the SR 6014 and never had a problem. It was then I told him I was sending the MM-7055 back. He said ok. I sent the item back and ordered a NEW MM-7055 from Amazon and placed it in the exact same configuration and have not had a problem as of yet, even when playing at very high levels.
Two days later I get a refund but they charged a 20% restock fee and did not refund the full purchase price. I immediately responded to the seller asking why? And this was there response:
"We ran the amp on diff speakers on our test bench and it played for over 6 hours and never shut down. The impdeance of the Polks goes too low below 4 ohms https://www.soundandvision.com/conte...-labs-measures
Impedance reaches a minimum of 3.75 ohms at 66 Hz and a phase angle of –47.96 degrees at 83 Hz.
The Marantz amp can only handle a min of 6 ohms. This is why it kept going into protect mode. The speakers are low impedance and clipped the amp. Follow the review link I provided for the test bench results."
The article references these test results:
The LSiM707’s listening-window response (a five-point average of axial and +/–15-degree horizontal and vertical responses) measures +1.05/–1.73 decibels from 200 hertz to 10 kilohertz. The –3dB point is at 34 Hz, and the –6dB point is at 30 Hz. Impedance reaches a minimum of 3.75 ohms at 66 Hz and a phase angle of –47.96 degrees at 83 Hz.
But the same article lists in the specs that the speakers are 8ohm. Do they really have a point or is this just horse****?
Gear Front Stage: Polk LSiM 707s Ctr: LSiM 706c
Srd: LSiM 703s Ht: 700-LS Rears: Cheap Infinity book shelves
Amps: Marantz SR6014 and MM7055
Sony Ubp-X800M2, Xbox, 65" Samsung
Refurb Marantz MM-7055 from Accessories4Less
A couple of months ago I purchased a pair of Polk LSiM 707's and a 706 center channel that were being clearance from Adorama. I quickly found out that my avr was woefully lacking. I then purchased a new Marantz SR 6014 for processing and powering the back and height channels. I also picked up the 5-channel Marantz MM-7055 to power the front stage from accessorie4less via Amazon. I used four channels to power the 707s in Bi-amp and the other channel was for the center. Before even hooking up the 707s in that configuration I had the center playing at very low volume for a few minutes when the refurbed MM-7055 went into protect mode. My only thoughts were that I had gotten a dud or possibly not getting enough ventilation. Before using it again I purchased an AC Infinity air cooler that sits on top of the amp and vents air out the back. I guess this helped some because I could sometimes watch TV/Blu-ray without a problem, but other times it would go into protect mode after it being on for less than an hour.
I went through some troubleshooting over the course of a couple of days through email with the tech at Accessories4less but the problem kept reoccurring. The final straw was one night I turned on the amp and it started with the internal fan blowing and after 5 minutes of watching tv at low volume it went into protect. I emailed the tech and he starting asking about the speakers and then he said that the Polks were too power hungry. I told him they ran fine on the SR 6014 and never had a problem. It was then I told him I was sending the MM-7055 back. He said ok. I sent the item back and ordered a NEW MM-7055 from Amazon and placed it in the exact same configuration and have not had a problem as of yet, even when playing at very high levels.
Two days later I get a refund but they charged a 20% restock fee and did not refund the full purchase price. I immediately responded to the seller asking why? And this was there response:
"We ran the amp on diff speakers on our test bench and it played for over 6 hours and never shut down. The impdeance of the Polks goes too low below 4 ohms https://www.soundandvision.com/conte...-labs-measures
Impedance reaches a minimum of 3.75 ohms at 66 Hz and a phase angle of –47.96 degrees at 83 Hz.
The Marantz amp can only handle a min of 6 ohms. This is why it kept going into protect mode. The speakers are low impedance and clipped the amp. Follow the review link I provided for the test bench results."
The article references these test results:
The LSiM707’s listening-window response (a five-point average of axial and +/–15-degree horizontal and vertical responses) measures +1.05/–1.73 decibels from 200 hertz to 10 kilohertz. The –3dB point is at 34 Hz, and the –6dB point is at 30 Hz. Impedance reaches a minimum of 3.75 ohms at 66 Hz and a phase angle of –47.96 degrees at 83 Hz.
But the same article lists in the specs that the speakers are 8ohm. Do they really have a point or is this just horse****?
Gear Front Stage: Polk LSiM 707s Ctr: LSiM 706c
Srd: LSiM 703s Ht: 700-LS Rears: Cheap Infinity book shelves
Amps: Marantz SR6014 and MM7055
Sony Ubp-X800M2, Xbox, 65" Samsung
Comments
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A given speaker is rated for its nominal impedance, which basically means an average. A given speaker's impedance will rise above and fall below that nominal rating depending on the frequency. The fact that your speakers drop to 3.75 ohms at one frequency has no bearing on the fact the amp in question was defective further evidenced by the fact the replacement amp is working perfectly. In short, the seller's excuse is BS.Political Correctness'.........defined
"A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."
President of Club Polk -
Wow, shame on you Acessories4Less.
