Added a second sub to my home theater setup

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kevm14
Posts: 15200
Joined: Wed Oct 23, 2013 10:28 pm

Added a second sub to my home theater setup

Post by kevm14 »

My Dad got this Polk Audio 100W subwoofer 10 years ago and somewhere along the way decided he didn't want to use it with the TV. He has an old ~2008 era MItsubishi 46" LCD with a built-in sound bar and I guess it has a sub output. I don't really know why he stopped using it. I know there was a really big dead spot below where the TV speakers could respond but above the 200Hz of the sub, but I am sure acoustics had nothing to do with it...

After moving it to the living room for some number of years, he finally asked if I wanted it. Of course I do. So I brought it home.

It is either this, or almost identical:
https://www.bestbuy.com/site/polk-audio ... Id=9154073

It's nothing crazy high end but is a decent unit.

About 9 or 10 years ago I bought an old Sony CRT (36" HD 4:3) as well as a Sony 5.1 system of the same era as the TV. Even 2 TVs later I am still using the Sony system. It does an acceptable job with movies and other surround sources so I have had no reason to replace it even as the receiver display has been completely blank for probably 4+ years now. Anyway, it has a 100W sub that does alright but the acoustics in my large great room really did not allow the bass to reach the listener in many of the seating positions that we have. If we were against the back wall, that would help a LOT but that would be too far from the TV. In the middle of the room, there is a dead spot. This has bothered me for years. Enter the second sub.

I have read on home theater forums that adding a second sub can make a huge difference as it tends to help cut down on the dead zones significantly and overall enhance the sound. So I decided to hook it up.

The sub signal comes from my receiver (obviously) and is just a single RCA cable. The Polk sub takes a L and R input and did not appear to have an auto mono mode so I would need to split the signal into both the L and R inputs. Side note, it also has speaker level inputs if you are really limited.

So I bought 2 Y cables and an RCA gender changer. One Y cable hooks up to the original signal wire. One of the outputs goes to the Sony sub, done. The second output goes to a 12' cable (that I already had) via the gender changer and at the other end, another Y cable to split the mono signal to feed both the L and R inputs. The result is both subwoofers work.

I tried one spot to the right of the TV and ended up moving it to the left area, where it is almost invisible. The sound is still nowhere near as good in the seating positions as it is in the back of the room (where there is some really impressive bottom end) but it is significantly improved, and that's the point. Success. I had to turn the volume down from the middle setting a bit on the Polk. Left the Sony basically in the middle (maybe a touch lower).

I don't know what would make good bass for middle of room viewers. One sub in each front corner of the room perhaps? I have no idea. Or maybe the Polk could go in the rear with the phase switch set to 180 degrees out. Thumbs up for 2 subs.
kevm14
Posts: 15200
Joined: Wed Oct 23, 2013 10:28 pm

Re: Added a second sub to my home theater setup

Post by kevm14 »

I am reading the reviews on Best Buy. I am sure my room needs like dual 12s at several hundred watts each (get down to a real 20Hz, shake the walls, etc.), but then my Sony 5.1 system will be overpowered so this will do until I am forced to replace the entire system. I don't know when that will be. I wish the display on the receiver worked but it doesn't seem to matter. The only thing I really can't do is configure the speaker distances. They are still set to my old house (which means they are completely wrong for my great room). Good audio is expensive though so I bet one look at pricing for a system that I'd want to upgrade to and that would be the end of that. Maybe used stuff is a thing here. Probably is. People upgrade stuff and spend crazy money on home theater.
kevm14
Posts: 15200
Joined: Wed Oct 23, 2013 10:28 pm

Re: Added a second sub to my home theater setup

Post by kevm14 »

My system consists of a Denon X4000 avr, B&W 683 S2 mains, B&W HTM61 S2 center channel, and 6.5" in ceiling rear speakers. I originally bought the matching $650 B&W ASW610 10" sealed subwoofer to fill in the low end, but was unsatisfied. The B&W subwoofer was very tight and clean for music, but lacked in overall output for movies. I didn't want to spend any more money on an additional matching B&W subwoofer, so I figured I'd now try 2 less expensive 10" ported subwoofers instead for increased output. After reading many great reviews for this $200 Polk Audio PSW108, I exchanged the B&W for 2 of them. They are not quite as tight and detailed as the B&W for music, however they make up for it with much more power and impact for movies. With 2 subs vs 1 I also get much more uniform bass response throughout my listening area. I am more than satisfied!
Yup, I think I had the right idea. Two is in fact better than one for subs in a room. They need to be placed apart from each other.
kevm14
Posts: 15200
Joined: Wed Oct 23, 2013 10:28 pm

Re: Added a second sub to my home theater setup

Post by kevm14 »

I just put on some of my old bass test stuff. In the back right corner of the room (when facing the TV), the bass is QUITE strong, and plays down to the lowest frequencies in this particular song. Damn. Too bad it doesn't sound like that in my normal viewing position. Acoustics matter, big time.

To my ear it may have played down below its rated 35Hz. I'd say 25. You could feel how low it was by the frequency the wall I was leaning on was shaking.
kevm14
Posts: 15200
Joined: Wed Oct 23, 2013 10:28 pm

Re: Added a second sub to my home theater setup

Post by kevm14 »

Music is not as good. In the listening position it is muddy and not well defined, and does not extend down low enough. In the corner (and some other areas) it is better. Acoustics, again. I could go buy another one of these Polk subs and put it in the right corner. That may be excessive though having multiple subs, even turned down, will probably yield better results than one powerful sub, based on my experience.

The performance in the corner does remind me of car audio. It had significant "cabin gain" or I guess room gain. But not in a distortive way.

In fact, it was hitting hard enough that it would shake my vision just a little bit, making the TV appear to vibrate (it wasn't). I just cranked up Money for Nothing and it even did it on some 80s rock, in the corner. I guess I could just listen to music in the corner...

All that said, I think my floor standing 3-way Cerwin Vegas with 12" woofers are still better for music. You put a couple hundred watts into those (per channel) and you have a light duty PA solution. A sub/sat arrangement is not ideally suited to music because the satellites tend to be small, and not have separate tweeters and midrange drivers so you end up with a pretty significant missing chunk of high bass or low midrange and maybe even some missing high end. They just can't handle the power, nor does this Sony receiver have any kind of significant per channel power output. I'd guess 50W, at the most.
kevm14
Posts: 15200
Joined: Wed Oct 23, 2013 10:28 pm

Re: Added a second sub to my home theater setup

Post by kevm14 »

Pretty good short video on placement of dual subs.

https://youtu.be/OXVpy5jaNsk

They say opposite diagonal corner placement measures the best. Interesting. I will need to figure out wires for the rear one...
kevm14
Posts: 15200
Joined: Wed Oct 23, 2013 10:28 pm

Re: Added a second sub to my home theater setup

Post by kevm14 »

Smart ass comment:
I run 1.5 1 speaker and 5 subs.
kevm14
Posts: 15200
Joined: Wed Oct 23, 2013 10:28 pm

Re: Added a second sub to my home theater setup

Post by kevm14 »

Forgot to mention something funny. As I was testing and messing around with sub positioning, I heard some rattling in the Sony sub. I tipped it and out of the port came tumbling some plastic toy balls. I shook it more and more came out. Later on, I realized there were STILL more. I shook it and finally got another one out. There were still like two more. It took some serious tumbling and jostling around but I was finally able to get everything to come out of the port. Good god. Kids with little arms and hands....sheesh.
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