# help using receiver to power passive sub



## kwalikum (Oct 31, 2011)

Hi, my powered sub is busted and while I look for a replacement (reading up on building a tapped horn) I thought I would use a spare integrated amp and tower speakers. Yes, I realise this is not ideal and is not a permanent solution, but it should be better than nothing, right? In any case, I want to figure out what is going wrong because now I'm frustrated.

The problem is the input level appears to be far too low so I have to crank the integrated amp volume and end up with a ton of constant hiss/static.

I'm using a Kenwood KRF-V6070D listening to a 5.1 source. The subwoofer output from the Kenwood is running to the left CD input on a Sony STR-DE475, and then I run the left speaker output to a tower speaker. The tower is poor quality but has a 12" woofer but it works as expected when used as a tower speaker. When I use the test tone function on the Kenwood I get the usual (pink?) noise from each of the speakers including the tower I'm using as a passive subwoofer. However, in order to match the volume on each speaker I have to crank the volume on the Sony up to almost maximum, and this comes with a constant hiss of what I assume is over-amplification.

It would seem to me the source signal is far too low - am I doing something wrong here? Any ideas? :dontknow:


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## tonyvdb (Sep 5, 2007)

Im a bit confused by your post, you say you want to power a passive sub in your heading but you talk about using a "tower speaker" that has a 12" driver in it. Are you trying to use the tower speaker as a Sub?


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## kwalikum (Oct 31, 2011)

tonyvdb said:


> Are you trying to use the tower speaker as a Sub?


That is correct. I realise it is far from ideal, and if I had a spare wad of cash to buy a real active sub then I wouldn't have bothered posting. I'm sure some will say no sub at all is better than a cobbled together integrated amp plus cheap tower speaker, but I'd like to at least know why the level is so far off...


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## Wayne A. Pflughaupt (Apr 13, 2006)

It might be that you have the Sony set for a surround-sound mode, and all the “energy” is being directed to the center channel speaker connection. So, make sure you have the Sony set for “direct” or “byass.”

If that doesn’t help, go into the Kenwood’s menu and increase the subwoofer output level.

Regards,
Wayne


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## kwalikum (Oct 31, 2011)

Wayne A. Pflughaupt said:


> It might be that you have the Sony set for a surround-sound mode, and all the “energy” is being directed to the center channel speaker connection. So, make sure you have the Sony set for “direct” or “byass.”
> 
> If that doesn’t help, go into the Kenwood’s menu and increase the subwoofer output level.
> 
> ...


Thanks Wayne. I have the Sony set for 2 channel audio and in the speaker setup I have front L/R set as "Large", centre as "No", surround L/R as "No", and subwoofer as "No". I have also made that change to the Kenwood output with front on -10dB and subwoofer on +10dB. This helps, but not nearly enough.


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## tonyvdb (Sep 5, 2007)

Have you unhooked the other speakers in the tower? the reason your hearing alot of hiss is because the highs are still being sent to the tweeter and thats going to give you hiss.


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## kwalikum (Oct 31, 2011)

tonyvdb said:


> Have you unhooked the other speakers in the tower? the reason your hearing alot of hiss is because the highs are still being sent to the tweeter and thats going to give you hiss.


No, I thought about doing that but didn't actually do it. I'll give that a try also. Am I still treating symptoms rather than the problem tho? My understanding is the LFE channel should be fairly clean in those higher frequencies, and that still leaves me with the sub amplifier on almost max.

Thanks for your suggestion - I'll give disconnecting a go.


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## tonyvdb (Sep 5, 2007)

Also remember that the receivers amps are not very powerful and the lows will need a fair bit of juice to make it worth while. I suspect that you wont get more then 80 watts to that speaker and thats why your finding you need the volume knob at max. I can garentee thats going to introduce noise and distortion.


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## Misfit (Dec 27, 2013)

The "Subwoofer Out" from your Kenwood receiver is filtered, corrrect? It's only bass, no highs or mids? Is it crossed-over at 80 Hz or something? 

It may be that the Sony receiver you're using is filtering out the lower frequencies to the "Front" designated speakers. Not likely, since you said they were set to, "Large Front", but if the Sony had a High-Pass Filter or something, that would be a problem. 

Could also be a polarity issue, with woofers out-of-phase with each other. I don't know how many of what you have going, but placement can also disrupt and cancel low frequencies out.


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## TheHammer (Dec 16, 2012)

kwalikum said:


> The problem is the input level appears to be far too low so I have to crank the integrated amp volume and end up with a ton of constant hiss/static.
> 
> I'm using a Kenwood KRF-V6070D listening to a 5.1 source. The subwoofer output from the Kenwood is running to the left CD input on a Sony STR-DE475, and then I run the left speaker output to a tower speaker. The tower is poor quality but has a 12" woofer but it works as expected when used as a tower speaker. When I use the test tone function on the Kenwood I get the usual (pink?) noise from each of the speakers including the tower I'm using as a passive subwoofer. However, in order to match the volume on each speaker I have to crank the volume on the Sony up to almost maximum, and this comes with a constant hiss of what I assume is over-amplification.
> 
> ...


I would suggest a systematic approach here. 

1) It appears that your Sony is set up correctly, but lets check this. It might have a setting wrong. Please try hooking up another source to the left CD input (like the audio output of a DVD player) and see if you get full volume to that speaker. Be certain to turn the volume way back down because, if the Sony is set up properly, you will get full power to that left speaker. Please use the same connector that you use to connect the Sony to the Kenwood. If that works properly, then the problem is the sub output on the Kenwood. 

2) If step #1 works, then try hooking that left CD on the Sony back to the sub out of the Kenwood like you had it before. Try running a pink noise test and see if you get sound to the sub (assuming your pink noise test drives the sub). If not, we need to look at the setup in your Kenwood. Setting that sub output to +10 and the front to -10 should be way overkill. I would suggest going in and setting your Kenwood to 5.1 and make certain your speakers are set to small. I am not familiar with this Kenwood, but is there a crossover frequency setting for the sub? If so, set it to 120 Hz or as high as you can set it for the purposes of this test. Also, restore all balance settings to 0 db.

Please let us know how this works out. Thanks.


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## RTS100x5 (Sep 12, 2009)

The easy answer is just buy an inexpensive plate amp from Parts Express :heehee:

http://www.parts-express.com/yung-sd200-200w-class-d-subwoofer-plate-amplifier-module-no-boost--301-504


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## TheHammer (Dec 16, 2012)

RTS100x5 said:


> The easy answer is just buy an inexpensive plate amp from Parts Express :heehee:
> 
> http://www.parts-express.com/yung-sd200-200w-class-d-subwoofer-plate-amplifier-module-no-boost--301-504


That is a sweet plate amp. If my B&W sub ever gives up the ghost, I may try that as a replacement.:clap:


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