Polk Speakers Hard to Drive ??

THIS IS A QUESTION THAT I POSTED ON ANOTHER FORUM...AND DOWN BELOW IS THE RESPONSE I GOT BACK ABOUT MY POLK SPEAKERS:

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Last night I added 2 RT35i as my rear surrounds and changed over from 5.1 to 7.1 --- When I was finished I put in my Gladiator DVD to enjoy the new set-up and it sounded great. Then during a loud battle scene when a catapult shoots a fire-ball, my Sony 4ES completely shut off the sound and gave me the following warning in the display:

"Protecting...Turn Off Power"

I turned off the receiver power, waited 30 seconds, and turned it on again and it played fine...although I didn't go as loud this time.

Does the fact that I added 2 more speakers spread my available power even thinner so that I overloaded the receiver?? I never had this problem before using the 5.1 set-up and it has been played very loud. (Also never had this happen with my older Sony STR-DE945)

I have heard the term "Clipping"....is this what happened and how can I prevent it??

Recv: Sony 4ES
Fronts: Polk RT800i
Center: Polk CS400i
Sides: Polk F/X 500i
Rears: Polk RT35i
Sub: SVS 25-31PCi

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AND HERE IS THE RESPONSE:

Polk speakers are infamous for impedance drops. Although they are specified as "8 Ohms nominal" or sometimes even "Compatible with 8 Ohm outputs", they often are not so compatible, with impedance that can drop to below 4 ohms at some frequencies.

I would suspect that the problem is with driving your very difficult polk speakers. Seven may be just too many.

Try flipping the impedance switch on the back panel of the receiver to 4 Ohm instead of 8 Ohm. This will enable the 4ES to drive your array of Polks more easily. You will (theoretically) get a very slight drop in peak power output (less than 1 dB), but the amp will heat up a lot less, and you will probably never get the protection message again.

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Does any fellow "Polk Owners" have any input ??

Thanks in advance,
Beski

I'm no expert, but I do know that many Polk speakers and other high-quality speakers can drop into a pretty low impredence when they are really pushed to do so. Adding 2 more speakers to your reciever on material that is very dynamic across all your channels will indeed make for a harder load to handle.

If you have any speakers set to "large" that cannot really handle bass below 80hz, or whatever your crossover is set, you should try setting those speakers to "small" and letting your sub/larger speakers handle the lower frequencies. This can reduce some of the strain on your reciever.

I'm pretty sure all the above information is right. Any Polk xperts that want to clarify or add to my suggestions go right ahead. I hope this helps ya.

All Speakers are Set to "SMALL"

What should my Crossover be set at??

BESKI - I have a STR-DA2ES and my default filters(crossovers) are 120hz when set to "Small", I will presume that yours are also. The default should be fine, I don't see why you would have to raise your filter(crossover) level.

As far as why this happened, I am unsure, Dr. Spec/ Mantis/ F1 Nut or someone will I'm sure notice this thread and provide some information for you. Good luck and I also would be interested in the cause or answer, keep us posted. Good luck.

Few thoughts and tests that I have for you Beski.....

None of the speakers that you have listed would cause a receiver to go into protection(even by adding speakers to going 7.1), provided that they're connected correctly (unless there's some internal wiring to be blamed). Out of curiousity, where did you get your 35i's and how long have you had them?

What I would do if I were you is check to make sure that you don't have any of the wires crossed. When you were hearing the sounds out of the rear surrounds(at the Protection point), did the sound come across as clear and crisp or was it a little muffled? If you have a cross-connected wire, either your receiver or your speaker will go belly up, possibly both.

Try reverting back to your 5.1 setup and watch your movie at the same volume that you were listening to when your receiver went into Protect Mode. If it works fine, then what you might want to do is to move some speakers around to test if you have a problem with the individual speakers (internal wiring being the culprit). Take your F/X500i's and replace them with your RT35i's and run your 5.1 system with the 35's. With your 35's in place of the 500's, then listen to the movie at the volume level your receiver shut down again. If the problem is with the speakers alone, then you should see that the receiver shuts down in this scenario. If after putting the 35's where the 500's were and your system runs without any problem, then connect your 500's (which you know to function normally at your louder listening volumes) as your rear surrounds and see what happens.

One of those scenarios should clarify what the problem could be. Let us know what you find out after tryin these couple of steps..........

I agree with that method approach. Perhaps try this to keep from moving a bunch of stuff around.....just unhook a set and play at same volume. For example, disco your rear center, play it loud, watch it and see what happens. If it does happen again, keep disco'd and disco the rear surrounds....etc. Play with it.

Like Brett said, none of your speakers should be causing it. But you never know. Either scenario should at least rule out your speakers.

If anyone else has some additional information, please pipe in.

The reason for switching the speakers around is to determine if the problem lies with the speakers, or the rear surround channel on the receiver itself. The only way to eliminate one or the other is to (unfortunately) move things around a bit.

Brett - No I agree with your approach. I was just expressing an option. :)

What is the Sony receiver's power ratings for 5.1 vs. 7.1? It seems like you reached the point where the receiver just ran out of juice. How high was it turned up, 10 o'clock, halfway, more??? I checked specs on all your speakers, they are all rated at 8 ohms "nominal", but I'm sure they drop lower than that, so if you can switch the receiver to 4 ohms as was stated, try that. You also need to consider that you are running much longer speaker wires to those rears and that can be a problem with impedance drop, putting more stress on a already stressed receiver. It could also be a sign that there is a problem with the receiver going south, it happens.

Can you say bigger amp? Polks have nice efficient speakers usually in the low 90's.

First, Thanks for all of the replies and suggestions !!

Here is more information that my help:

1) I bought the RT35i brand new about a year ago....I had used them "Stacked" on top of my RT800i using the A+B switch since my old Sony receiver let me play the 800's on "A" and the 35's on "B" at the same time and STILL have all HT Surround modes. The new Sony will only play in 2 Channel using this method so I moved them to the back. (But all speakers have played fine over the past year at high volumes with both music and HT so I know it's not the speakers).

2) I have a 50 foot run of Monster cable to reach from my Receiver, down through the floor, across the basement and back up through the floor to the 35i rear speakers. That is the same 2 pieces of wire that I used for the F/X500's when they were in the rear before I moved them to the sides. Now I also have 2 more new 50 foot runs to get to my side surrounds.

QUESTION: (Should this length of wire be reason to switch over to 4ohms on the Receiver??)

3) Just before I added the two speakers, I forgot that I was playing around with my crossover and I had everything set to 80 which may have been too much for the receiver at that part of the movie with that big impact of bass. I have since swithched back to the receiver's default setting of 120 and will do more testing tonight and over the weekend with the same Demo materials.

4) I just bought the Sony 4es Receiver brand new and it is only about 1 month old. I am still learning the settings and continue to experiment and test it's features and capabilities.

5) Last night I re-checked all speaker wire and connections, and then re-calibrated the system with AVIA set at 85db and also did the phase test. (Not sure if the 7.1 system was calibrated when I had my problem)

6) Played the Eagles-Hell Freezes Over last night very loud after calibration and it sounded great.

QUESTION: What are the Pro's and Con's if I switch the Receiver setting over to 4Ohms ??

Thanks again....Can't wait for more replies !!!
Tom

I'd wait for one of the forum's "ol' timers" to give their opinion on switching from 8ohms to 4ohms before you did it. Not saying that you will damage anything, but better safe than sorry.

If your recevier is clipping at 8 ohms, switching to 4 ohms will only exacerbate the problem. Dropping ohms increases the load on the amplifier.

Quote:

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Originally posted by BESKI64

3) Just before I added the two speakers, I forgot that I was playing around with my crossover and I had everything set to 80 which may have been too much for the receiver at that part of the movie with that big impact of bass. I have since swithched back to the receiver's default setting of 120 and will do more testing tonight and over the weekend with the same Demo materials.

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There's your answer.

I don't find that polk speakers are that hard to drive.. it just seems that they are not the most efficient speakers out there. most of them are around 89db to 91db. another well known brand (not Bose) makes speakers efficent to around 99db to 102db. those seem to be easier to drive louder.

does anyone know what the difference would be between a speaker that is rated at 89db as compared to a similar one at 101db ?

thanks, Al

Quote:

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Originally posted by danger boy
does anyone know what the difference would be between a speaker that is rated at 89db as compared to a similar one at 101db ?

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There is no difference in the speaker per say, there's a difference in the amount of power you need to provide it to play a certain sound level though.

For a 3dB gain you need to double the wattage (@ 1 meter). So to play something at say 105 dB, (which is extremely loud BTW), a speaker with an efficency of 89dB would need 40.3W (105-89=16; 16/3db=5.33; 2^5.33=40.3W) where as a speaker with a rating of 102 db would only need 2W (105-102=3; 3/3db=1; 2^1=2W).

Tony

Edit....

Quote:

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Originally posted by brettw22

What I would do if I were you is check to make sure that you don't have any of the wires crossed. When you were hearing the sounds out of the rear surrounds(at the Protection point), did the sound come across as clear and crisp or was it a little muffled? If you have a cross-connected wire, either your receiver or your speaker will go belly up, possibly both.

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Just out of curiousity.. what wires are you talking about? Are you talking about speaker wire?? Are you saying that having a speaker connected out of phase will cause that speaker and/or the receiver to fail???


As for the 89dB vs. 101.. it takes a doubling of amplifier power to increase volume by 3dB.

I don't think Polk tends to be on the low side of sensitivity.. or efficiency.. or whatever you want to call it. There are a wealth of loudspeakers on the market that are rated well below the 89-91dB range.

Quote:

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Originally posted by burdette
Just out of curiousity.. what wires are you talking about? Are you talking about speaker wire?? Are you saying that having a speaker connected out of phase will cause that speaker and/or the receiver to fail???

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Yes, the speaker wire. My understanding is that if you cross the polarities of the wire between the speaker and the receiver, you're creating a vicious loop that can and will cause either the speaker or the receiver to croak.......or both.

Quote:

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Originally posted by brettw22
My understanding is that if you cross the polarities of the wire between the speaker and the receiver, you're creating a vicious loop that can and will cause either the speaker or the receiver to croak.......or both.

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Huh.. I don't think that is true. I know I had my mains wired out of phase to each other last year for I don't know HOW long, and didn't discover it until I bought the S&V test DVD. I'd even wondered during that time why my stereo image seemed to have collapsed, but never considered checking the phase because I've always been such a stickler for phase - but, I'd done it. In a 2-channel setup, you can wire both speakers out of phase and get yourself right back in phase.

Many crossovers, especially 2nd-order, call for wiring the tweeter out of phase with the input, while the woofer is wired in-phase.

i accidently wired my fronts out of phase one time and the only thing I noticed was that the one out of phase lacked bass extension.

UPDATE:

O.K.......After taking everybody's suggestions, I re-adjusted my crossovers back to the standard default of "120".

I then played a few Demos including Gladiator, U-571, Titan AE, Toy Story 2, and JPIII...I also used my SPL during the Demo and had an average reading of 95db during playback with peaks reaching between 105-110db during the large impact scenes and explosions !! (Walls were Quaking and Windows were Shaking !!)

This was at an even higher volume then when my Receiver went into "Protect Mode" during the Gladiator scene and louder then my average HT listening level, so I can only think that having the crossovers at 80 must have contributed to the problem.

I was more then happy with the results....but I may still try the crossover at 110 and 100 to experiment with the sound quality. I did not notice any localization of bass at the 120, but I though the center channel sounded a little thin.

Would anybody suggest setting differet crossovers for different speakers (Example: Center at 90, Fronts at 100, Surrounds at 120 etc...or should they all be the same ???)

Thanks again,
Tom

BESKIE - Glad to hear that all is well. I run my filters at lower than default because it sounds better to me. I run them at 100 across the front stage. I also use the EQ feature on the ES receiver to adjust the base on the front and front mid about +5db. See if that helps and stays consistent with your sound levels.

Congrats on getting ur system back on track. Glad we could help.

all i have to say is i hate SONY!!!

except the Sony Playstation 2 of course. :lol:

I agree with ya on that one danger boy.

Quote:

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Originally posted by NINjesse
all i have to say is i hate SONY!!!

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For a new guy, you certainly have made your mark quickly. Could you be more specific on what you don't like about their products? While you're dwelling on that, let me point out that they make everything from low-end audio to high-end audio and video. Would you like me to list the audiophile grade models? Have you listened to/owned any high-end Sony? I didn't think so. If you purchased one of their $200.00 recievers, well what did you expect?!?

Tone it down and don't talk out of your http://www.clicksmilie.de/sammlung/g...smiley-036.gif

If you like SACD, Sony makes some of the best CD only SACD players. Their ES line of CD palyers are excellent. While their speaker lines leave much to be desired they make a good, inexpensive "Bang for Buck" subwoofer (SA-WM40) that for less than $200 (and a little tweaking) will give you a decent sub. I have owned Sony recievers and other gear over the years and while it isn't the best..for what I paid, it has served me well with few problems.

Also, while I think they can be pricey...the have made some of the best TVs for years going back to their Trinitron models. I have a 10 year old 32" model that just keeps going..and going...and going with many hours of use every day with ablsolutely no problems.

F1NUT - I hold the other side of the banner for SONY, :) I like Sony also, I can say it, Ive come out of the closet! Sony has given me great stuff, and I am a fan....much like Polk Audio.

Ever since I joined this fine forum, which I enjoy greatly, every 20 posts or more, there is the atypical hateful comment on a product or comment on a user trying to help another forum poster. And along with the atypical post is the no supporting data or even just a simple comment of their honest experience with said product. Hey, if you owned a STR-DA blah blah, and it was in the shop for 3/4 of its life, then hey, you have a gripe. But please enlighten us with what you didnt like about it..... think, I know its hard......but the forums help to educate also, relate your information. If BOSE sucks or is great, tell us why!(Note: This has been addressed and talked about)...If Radio Shack makes the flat out best high grade, audiophile ready, Class A, MOSFET amplifiers and speakers and you think that Carver Tube Amps are just pretty dildos....well hell brother let us know why!!!! :D