Solution to my Protect Mode Problem

Cpyder Posts: 514
edited February 2010 in 2 Channel Audio
I know I've started a lot of threads trying to diagnose my problem. Sorry about that. This forum has been very helpful so far. Thank you to everyone for your help!

In case you haven't experienced my needy nature yet, here's my problem:

My receiver (Marantz SR5003 [6 ohm]) is not properly rated for my speakers' (Polk LSi9s [4 ohm]) impedance. It works perfect for music but when I watch movies, the very low bass tracks cause my receiver to go into protect mode (or even blow) because in the low bass region is where the impedance for the speakers drops especially low which causes the receiver to draw too much current to handle. Originally, I wanted to buy a separate external amp. Then I thought about selling my receiver and buying an external amp to replace it. My source is my desktop computer.

However, I've decided against these two solutions since the first one is too expensive for me right now, and the second option forces me to use my computer's DAC which is severely lacking. I've even tried using an M-Audio Transit as my DAC, but nothing so far compares to the receiver's sound using optical from my computer. Using the 3.5mm jack on my computer or the Transit simply makes the bass way too wimpy and the highs overly bright. Bright enough to cause listener fatigue.

So, in the effort of preserving the sound quality the Marantz puts out using optical and finding a low cost solution I've come up with these ideas. Let me know if you think they are valid:

1.) Since it's low extended bass that causes the receiver to go into protect mode - buying a stand-alone crossover with a step high pass filter that cuts off around ~40 Hz.

2.) Is it overheating that is causing the receiver to go into protect? If so, could I come up with a cooling solution using fans or even possibly water cooling?

3.) Somehow increasing the resistance of the speakers? High resistance wires? Installing a resistor in-line with the speaker cables?

4.) Somehow installing a current meter so I can watch the amperage and adjust the volume accordingly so I don't push my receiver too hard. I feel like I'm totally blind figuring out how loud is too loud. I can easily watch movies at moderate levels, but as soon as I turn it up too much, (and depending on the bass track of the movie) it's a toss-up of whether the receiver goes into protect or not. It's happened at +4dB, -5dB, even -15dB once.

5.) Installing some sort of current limiter? Do these exist?

6.) Any other suggestions?

I know what you're thinking: Wow, what a cheap ****! Just buy a cheap, used, external amp! But I'm a poor college student who simply wants to enjoy the loud, stunningly realistic sound from my LSi9s and my Marantz.

Sorry for the long post, but please help me out! Thank you so very much!
Post edited by Cpyder on


  • hearingimpared
    hearingimpared Banned Posts: 21,137
    edited February 2010
    I think any of those option would degrade the SQ and just cause you more problems. Sorry to say this pal, but I think you should save up your pennies and get a good used amp.

    BTW deep bass lines cause a major current draw and that is most likely what is causing your receiver to go into protect mode not the heat.
  • Cpyder
    Cpyder Posts: 514
    edited February 2010
    I think any of those option would degrade the SQ and just cause you more problems. Sorry to say this pal, but I think you should save up your pennies and get a good used amp.

    BTW deep bass lines cause a major current draw and that is most likely what is causing your receiver to go into protect mode not the heat.

    That's what I was thinking. The deep bass lines are the culprit. Because I can turn up my music as loud as I want, yet movies cause the problem. Music usually only has short snappy bass and the long notes usually aren't as deep as in movies.

    And damn, I was kinda thinking the same thing, but I just wanted to hear someone else say it. If I put anything in between the receiver and speakers, I'll end up with poorer SQ. But what about a very steep crossover below what my speakers can play? Would that still hurt SQ?
    BlueFox wrote: »
    Get a powered sub and turn it up, and lower the volume on the AVR.

    This isn't what I wanted to hear, even though it's more than likely the right answer.
  • danger boy
    danger boy Posts: 15,722
    edited February 2010
    get an amp. sorry it's not a inexpensive solution. but it is the best one.
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  • heiney9
    heiney9 Posts: 24,341
    edited February 2010
    There really isn't a solution to your problem beyond listening at a lower level or getting better gear. I know, not what you wanted to hear. LSi's present a difficult load across the board and just adding a "cutoff" crossover isn't going to work and I doubt the LSi's go much below 40Hz anyways, so I would think you'd need to cut it at about 60-80Hz which will sound like crap, plus there will still be impedance issues

    You could get a powered sub and set the front speakers to "small" and cross the sub over at 80Hz.

    Heat or current limiting is causing it to go into protect.

    "Appreciation of audio is a completely subjective human experience. Measurements can provide a measure of insight, but are no substitute for human judgment. Why are we looking to reduce a subjective experience to objective criteria anyway? The subtleties of music and audio reproduction are for those who appreciate it. Differentiation by numbers is for those who do not".--Nelson Pass

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  • esowden
    esowden Registered User Posts: 55
    edited February 2010
    I don't know that I'd consider any of your ideas solutions. None of them address the real issue which is your speakers are drawing more current than the receiver can supply. The only real solution is replacing the receiver (or the speakers). Until you can do so - you'll have to live with listening at a lower volume.
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  • tonyb
    tonyb Posts: 32,683
    edited February 2010
    Sell the LSI 9's, pick up a pair of monitor 7b's, your receiver will be happy,you'll be happy, and save the coin for future upgrades when you can afford to do it right.
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  • jimmydep
    jimmydep Posts: 1,305
    edited February 2010
    You've gotten some good temporary solutions, but I think they're just band-aids. To solve you're problem you need to either replace the speakers with an easier to drive 8ohm load or get a power amp for the Lsi's.
  • Knucklehead
    Knucklehead Posts: 3,606
    edited February 2010
    Looks like everyone has pretty much hit the nail on the head. My system for Ht is about as basic as you can get, I had the same problem with it going into protect mode before I added a separate amp to run my problems now.
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