Active subwoofer out to passive subwoofer voice bleedthrough - help please

[yoda313]

Ok I bought a Kenwood passive subwoofer (sw15ht) at a garage sale for just 5.00. It looks to be in good shape. It only has one input - speaker cable input not an rca input and it is not a powered amp.

I have a 5.1 amp from about 10 years ago. I have the active subwoofer output but not a dedicated speaker level output that I could connect to the passive subwoofer directly.

After googling/yahooing for a bit I found out that you can connect the rca out from the subwoofer out on the main digital amp to any stereo and hook that up to the passive sub. So I did that and it seemed to work after fiddling with it for a little while. It had pretty good rumbling during action scenes - tested with a couple of blurays on my ps3 - note I only have a sd digital amp not an hdmi amp so its hooked up via fiber optic.

However there is vocal bleedthrough on the subwoofer. I can hear the voice track on the subwoofer. Its muffled to be sure but definitely there. At first I thought it might have just been a part of a movie that I hadn't realized had piped the vocal track through the sub to give it resonance but that was not the case. I tried another movie and the same thing happened multiple times and throughout my testing phase.

Is there a way to get a passive subwoofer to act just like a powered subwoofer from a 5.1 amp? I can dig up my sony amps model number if that would be useful. I have uploaded pics to clearly show what my setup currently is.

By the way - are there some kind of adapters to make this work smoothly? I have bumped into the term "crossovers" but I'm not sure what they are and if they are relevant to this issue.

Here are the pics and layout:

Back of my digital amp - the active subwoofer out rca jack:



Here is the input I used on my plain vanilla old stereo I brought out of storage - I have it currently connected to the right input of the tape input jack - any other slot and I couldn't get any signal to the subwoofer at all - I have to do it through the tape input to get it to work:




The plain vanilla stereo is connected to my new subwoofer via a single speaker cable connected to the right speaker out - just chose it could have been left:



The plain vanilla stereo is set to tape monitor so it will actually play the sound from the subwoofer cable:



This is the back of the subwoofer itself. It only has one input jack - for speaker cables - one set. That is from the right output from the plain vanilla stereo:



Here is what the sub looks like - it is a front firing 100 watt sub. My current powered sony sub - bought the same time as my sony amp - is a 50 watt down firing sub.



Your suggestions are welcome for this configuration. I really like the rumble I get out of the new sub but the vocal bleedthrough is not acceptable. It is like watching a dolby pro logic track and having the vocals rumble through the sub all the time - note I don't have a pro logic 2 amp so I don't have a fake discrete 5.1 mode.

Also if there is a "crossover" device that is designed for this procedure please let me know. However since this isn't really necessary as my existing subwoofer is satisfactory I don't want to pay a lot for one if I can get my current setup working.

Thanks again.

[aedipuss]

you may need to build a low pass filter. it only requires a resistor and a capacitor. or buy one.

[yoda313]

you may need to build a low pass filter. it only requires a resistor and a capacitor. or buy one.

Thank you for the suggestion. I'll have to look it up to read up on it.

Will that reduce or eliminate the vocals I'm getting in the sub? Even if I can't get 0 vocals I would be happy with a significant reduction.

Thanks again.

Edit - oh I forgot I have an old teac equalizer that I have kept. Would that be useful? Is there someway to fiddle with the settings to tweak it just right? It would kind of suck to have to have an old amp AND an equalizer just to run the new sub but If its simple enough I might go with it.

[yoda313]

Hello,

I was wondering if anyone had a recommendation for a low pass filter. I am not experienced in this and I don't know what I'm looking at with my internet searches. I would like to keep the cost at or under 20.00 if possible. Assuming this would do the trick and get rid of the voice bleedthrough.

Also I'm wondering if I should use a y splitter on the subwoofer out to my old stereo amp that I'm using to drive the subwoofer. I saw that mentioned at least once on a forum somewhere online.

I looked up stuff and saw a plate amp mentioned. However those started to look relatively expensive for a little project here that I'm not interested in investing a lot of money into.

Also I'm not sure what a speaker selector might do if anything. Again that was a single mention on one website.

Would this be something I might be able to get at a place like a car stereo store? Or what about the car section at BestBuy? Would stuff for car amps work for a home theater passive sub? Or are they different animals that don't work similarly enough?

Thanks for any advice. Thanks aedipuss for pointing me into a direction I should go into.

Edit - oh and I did try that old equalizer I had. I switched and slid every control on that thing and I couldn't get it to do anything. It did light up and everything so I assume it works. Just not sure if it would be anything to work with this setup.

[Hoser Rob]

This is probably about as cheap as you're going to get, and you'll need a case for it as well and the ability to solder the connectors you'll also need:

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=266-444

The reason you're getting vocals is that a 12" or 15" speaker will reproduce midrange frequencies quite well. Lots of electric guitar amps use 10" or 12" or even 15". That's why you need low pass filtering.

I don't see what you'd need a y splitter for to drive a single subwoofer if the signal is coming from the sub out on your 5.1 amp. It's already downmixed to audio at that point, which is what people use those y adapters for.

[yoda313]

This is probably about as cheap as you're going to get, and you'll need a case for it as well and the ability to solder the connectors you'll also need:

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=266-444

Designed to be wired in-line between amp and speaker by using .205" disconnect terminals or soldering.

So does that mean I'd solder the speaker wires coming from the plain stereo out to this device and then likewise to the subwoofer itself? Its only one set of wires as shown in the picture above.

The reason you're getting vocals is that a 12" or 15" speaker will reproduce midrange frequencies quite well. Lots of electric guitar amps use 10" or 12" or even 15". That's why you need low pass filtering.

Ok.

Oh and about the y splitter I was just repeating what I read on one website. I tried it for the heck of it and it didn't do anything.

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So All I would do is solder the outgoing speaker wire from the plain stereo amp that I am using to drive the subwoofer and solder the outgoing wire from the filter?

Thanks for all the suggestions.

[Hoser Rob]

You'll want to put it in a case ... those boards and wires are not meant to be used in the open ... with 2 sets of speaker connectors put into the case as well. Actually if they sell them as a stereo pair you'd just need 1 set.

[yoda313]

You'll want to put it in a case ... those boards and wires are not meant to be used in the open ... with 2 sets of speaker connectors put into the case as well. Actually if they sell them as a stereo pair you'd just need 1 set.

Ok. I think I follow you. I'm going to think about it. I'll let you know if I do it.

[Hoser Rob]

Try searching "diy audio". I should have thought to mention that first.

[yoda313]

Thanks Hoser Rob - and aedipuss as well

[yoda313]

Ok I decided to go ahead and do it. I just bought the 100hz low pass filter that Hoser Rob linked to. However I bought it through amazon with parts express as the store supplier. I was just being lazy and didn't want to set up a new account at another store. Amazon already has my information so why not do it that way.

I used standard shipping and the estimated delivery date is between the 10th and the 15th. I'll let you know when I get it.

I'll have to think about what to use for a case. I've seen some crazy electronic mods out there that often use a full size altoids mint container as a case. I don't know if this is the right size for it but I might try that myself

[yoda313]

Well my filter came Thursday night. I did a dry fit without soldering and it worked. I liked it. It definitely did the trick. No more voices through the sub.

This morning I went to radioshack and bought a case for it. I put it together and soldered the wires on. It kind of looked like what a pipe bomb must look like

I am not too proud to admit I did get help soldering. I got my dad to help out there. I never did any soldering before so you got start somewhere. But now it is done and I am happy.

The only thing is it seems to cut out occasionally. I think it only does it on extremely heavy bass passages. I am going to have monitor it and check out levels I do get. Seeing as this quite a bit improvised I am not too surprised. I'll keep an eye on it and look for a happy medium of heavy power but without cutting out.

I'll post the pics below. I had the mouse in one of the pictures to show a relative size of the whole thing. In the picture on the company website it looked like it wasn't any bigger than a paper clip. It sure surprised me when it came in.

Thanks everyone for your help. The 5.00 sub now comes in at about 30.00 but for a 100 watt kenwood that I can use with my system and I am more than happy with it.

FYI the last pic shows the zip ties that I used to secure the filter into the case so it wouldn't slide around a lot.

I'm going to post them in the before and after order.