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  1. #1
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    new sub sounds week...do I need an amp?

    I recently bought speakers for a home theater system. Hereís my current setup:

    Sony STR-DE835 5.1 receiver - 100W per channel
    Polk RC85I in-wall surround speakers (5) Ė 8 ohms 100W per channel
    JBL HTI88 in-wall passive subwoofer Ė 250W max

    I finally installed the in-wall sub this weekend and it sounds like itís not getting enough juice. Per the instructions I hooked it up by running the front outs of the receiver to the inputs on the sub, then ran the outputs of the sub to the front speakers. The front speakers sound great, no difference. However the sub sounds very quiet. Is there some setting I might be not doing in the receiver setup? It sounds weak whether Iím listening to the radio, TV, or DVDs. I think I have the speaker size set to small, and using the 5.1 audio output selections. Or do I need to buy an amp to power the sub? If so what are your opinions on the ONKYO M-282 2x100W amp ($200) versus the AudioSource Amp 100 2x50W amp, bridgeable to 150W RMS mono power ($95). I know these are both pretty low end, but I have a small budget to work with due to moving into a new house and the WAF.
    Last edited by seannorek; 04-10-2007 at 04:24 PM.

  2. #2
    _ Luvin Da Blues's Avatar
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    Welcome to this forum seannorek.....

    You need to set your front speaker to large with a passive sub wired they way you have it and turn off your subwoofer setting . If you set your speaker to small it assumes that you have a separate powered sub and directs the low freqs. to something that is not there. Hope this helps.

    Let us know if this works.
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  3. #3
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    Thanks for the info. I've lurched here before but I'm pretty much a noob when it comes to home theater. When I get back home on thursday night (work out of town) I'll make those changes and let you all know.

    Thanks!

  4. #4
    Forum Regular N. Abstentia's Avatar
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    That Sony receiver is definitely not enough juice for the sub, you need a dedicated subwoofer amp.

  5. #5
    _ Luvin Da Blues's Avatar
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    I agree with N.A. if you want it to really "kick" you'll need more power than what the Sony is going to give you considering that the wattage will be split at the sub to feed the front speakers. Not sure of the % split but will be less than 100 watts.

    If you can, try both amps at a dealer with a boxed passive sub approx. of the same size and quality to determine which one will "kick" more. My advice would be to buy a used amp of better quality and power to fit the budget (not sure if you are able to buy an used powered sub to steal the plate amp out of and retro fit it into another enclosure). The problem with a in-wall sub is that it may not be placed for the most or best bass.

    Having said that you may be happy with the level that the Sony can provide and you being happy with it is all that matters
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  6. #6
    _ Luvin Da Blues's Avatar
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    Good Day seannorek..

    You may want to look at these plate amps I found on ebay...of course you would have to build something to enclose them in...wooden box that you could hide behind your equipment???

    One advantage of a dedicated sub amp is that you have control over the crossover point and phase adjustments.

    http://cgi.ebay.ca/215WATT-EOSONE-PO...QQcmdZViewItem

    http://cgi.ebay.ca/EOSONE-POLK-1RF00...QQcmdZViewItem
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  7. #7
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    Quote Originally Posted by Luvin Da Blues
    Good Day seannorek..

    You may want to look at these plate amps I found on ebay...of course you would have to build something to enclose them in...wooden box that you could hide behind your equipment???

    One advantage of a dedicated sub amp is that you have control over the crossover point and phase adjustments.

    http://cgi.ebay.ca/215WATT-EOSONE-PO...QQcmdZViewItem

    http://cgi.ebay.ca/EOSONE-POLK-1RF00...QQcmdZViewItem

    Thanks so much. I really appreciate the info. So I would just need to build something to put the plate amp in and then just treat it like any other amp? I do have an old Yamaha 10” powered sub. My wife hates it because it’s big. I don’t know what the wattage is on it but I guess I could take the plate amp off it as well?

    What's the advantage of using a plate amp vs buying a regular amp?

  8. #8
    _ Luvin Da Blues's Avatar
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    "Thanks so much. I really appreciate the info. So I would just need to build something to put the plate amp in and then just treat it like any other amp? I do have an old Yamaha 10” powered sub. My wife hates it because it’s big. I don’t know what the wattage is on it but I guess I could take the plate amp off it as well?"


    may not be the prettiest thing but would be functional....just another thought........i assume that all the wiring is in the wall????....could you mount the plate amp right in the wall where the cables emerge??? again it may not be pretty but if your equipment hides it???
    Back in my day, we had nine planets.

  9. #9
    Class of the clown GMichael's Avatar
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    Quote Originally Posted by Luvin Da Blues
    "Thanks so much. I really appreciate the info. So I would just need to build something to put the plate amp in and then just treat it like any other amp? I do have an old Yamaha 10Ē powered sub. My wife hates it because itís big. I donít know what the wattage is on it but I guess I could take the plate amp off it as well?"


    may not be the prettiest thing but would be functional....just another thought........i assume that all the wiring is in the wall????....could you mount the plate amp right in the wall where the cables emerge??? again it may not be pretty but if your equipment hides it???
    It was my oppinion that plate amps saved space by being built into the sub box. In your case, it may be easier to use a standard amp.
    WARNING! - The Surgeon General has determined that, time spent listening to music is not deducted from one's lifespan.

  10. #10
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    The sub is mounted flush in the wall so there are no wires coming out of the wall. I have my DVD player, receiver, and cable box on a tv stand. The wires coming out of the receiver go into a wall plate and then are run behind the wall (using a crawl space) and then are run to all the in-wall speakers. It’s possible I could mount the plate amp right into the wall, but I doubt the wife will go for that.

    I think my options are either use a plate amp and build something to make it look presentable on the tv stand or possibly tuck it right behind the tv stand, or buy a regular amp. If I were to bridge the AudioSource Amp to get 150W RMS, do you think that would supply enough power, or should I just spend the extra $100 and get the Onkyo M-282 which is 100W x2, but I don’t know if it’s bridgeable. If not then I would only be able to get 100W to the sub correct? Mind you I love good sound, but I obviously do not have high end equipment and I really want to get the bass booming again like my old Yamaha powered sub.


    One thing is that I am going to wire other zones throughout the house so we have music in every room. I suspect I will need an amp to power that later on when I get around to doing all the wiring.

    Onkyo amp http://tinyurl.com/2rdaxw
    Audiosource amp http://tinyurl.com/38per7

  11. #11
    _ Luvin Da Blues's Avatar
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    First I would try the receiver adjustments and see how that goes...if that doesn't cut the mustard then you should, if you can, audition each choice to really know (I'm not familiar with either amp but you will want the amp with the highest output current).

    Have you considered a single mono block amp?
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  12. #12
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    Is a single mono block amp just a single channel amp? I've never heard the term before. So it's just a single channel amp to drive the sub only?

  13. #13
    Class of the clown GMichael's Avatar
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    Quote Originally Posted by seannorek
    Is a single mono block amp just a single channel amp? I've never heard the term before. So it's just a single channel amp to drive the sub only?
    Yeah, but in most cases they are a little pricey. Great if you are putting together a "money is no object" system.
    WARNING! - The Surgeon General has determined that, time spent listening to music is not deducted from one's lifespan.

  14. #14
    _ Luvin Da Blues's Avatar
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    the operative words are "most cases"

    Check this out

    http://cgi.ebay.ca/L-K-Marantz-MA500...QQcmdZViewItem
    Back in my day, we had nine planets.

  15. #15
    Class of the clown GMichael's Avatar
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    Quote Originally Posted by Luvin Da Blues
    the operative words are "most cases"

    Check this out

    http://cgi.ebay.ca/L-K-Marantz-MA500...QQcmdZViewItem
    That would be great if it goes for the $75 that it's at now. But with 6+ days left?
    Worth looking into though.
    WARNING! - The Surgeon General has determined that, time spent listening to music is not deducted from one's lifespan.

  16. #16
    _ Luvin Da Blues's Avatar
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    Agreed GM but was thinking that there is only one and most people buy them in pairs so......


    If one was inclined to have patience a deal or two should pop up.
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  17. #17
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    Hi Seannorek; I was thinking about your post and realized I had done an experiment for about a year along these lines.

    First, like some of the members of the forum suggested, set your main speakers to LARGE on the bass mangement menu and see how that works.

    I cannot comment below on a bridged stereo power amplifier and as to how you would hook up the speaker output of that amp into the speaker input(s) of that passive sub.

    As for a mono block amp, you might only hook up the speaker output of the mono black amp to one of those passive sub speaker inputs. You might want to run a jumper wire into the second speaker input of the passive sub. However, you need to keep in mind of the impedance of that sub. It is most likely a dual voice coil sub. As such, each voice coil has its own impedance. If a jumper is added, the impedance becomes that of two speakers in parallel. That impedance could be lower than what the mono block is capable of handling.

    As for a stereo power amplifer, yes, you can use that. You would hook up the speaker outputs of each channel to the speaker inputs of your passive sub, the same way as you are now doing it with the sony. However, your main left and right satellite speakers are now hooked directly to the sony's main left and right speaker outputs.

    You would have to hook up a subwoofer cable from the sub out of the sony to the inputs of your power amplifier. That will require your use of a Y adapter.

    You would set the bass management of your sony receiver to small. I do not know what kind of bass mangement crossover your receiver has, whether it is fixed or variable, however, what ever that output is will feed into the power amp. If you have a variable crossover in the receiver and small satellites, start with the lower figure.

    Set your sub output on the receiver to the lowest point. Some receivers are 0, others could be -10 or -15. Put some music on like an FM station and slowly increase the sub output until the bass blends with your satellites. Tweaking will follow as needed.

    I ran the power amp section of a NAD int. amp into two separate 10 inch passive subs from a fixed bass crossover of a receiver into that power amp with a Y adapter and it did work rather will.

  18. #18
    Crackhead Extraordinaire Dusty Chalk's Avatar
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    Quote Originally Posted by seannorek
    Or do I need to buy an amp to power the sub?
    I really think a separate amp for the sub would be my advice.
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  19. #19
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    Thanks everyone. First thing I did when I got home was try switching the speaker setting to LARGE. That did increase the bass output some, but it's still nowehere near what I had with my powered Yamaha. So I'm gonna buy an amp to power the baby up. I'm gonna watch those mono block amps and either get one of them or the Onkyo amp. Hopefully one of those will fix my issue.

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