Where can I find some info about choosing the right home theatre sub? (1 Viewer)

[VanillaRice]

Ok I just read connecting subwoofers 101 and now know how to connect my subwoofer properly. I was just confused about the left and right inputs on a sub as they are obviously mono devices. This propmted me to run 2 RCA's off one of my audio out channels and not off my Subwoffer pre-out
Why do these subs have left and right channels ? Is it for older amps that dont have sub pre outs?

 

[Robert_J]

Correct. They give you options for many different systems. The only proper way to connect a sub to an A/V receiver is the LFE/sub out to either one of the inputs. It doesn't matter which one as they are summed inside the amp. Your speakers connect directly to the receiver. You should set your speakers to small or whatever setting forces the receiver to send all bass to the sub.
You have found the room placement makes a huge difference. If you don't have any test equipment then you need to perform the "crawl method". It sounds stupid but works. You put the sub in your listening position. Then you crawl around on the floor until you find the location that sounds best. That's where the sub goes.

 

[Robert_J]

The number one cause of distortion is having too little power, or lack of quality wattage......

I'm not debating you in this thread. In fact, it's not proper forum etiquette to hijack a thread like this. If you want to discuss theory, I'll be happy to debate you in your own thread.

 

[aerialacoustics]

I am a returning Iraq Vet, I do not hijack anything. I am just explaining facts; the net is saturated with misinformation and you saying that large subs need less power shows you need more experience in the industry. It is a matter of science, not debate.

 

[Robert_J]

I am a returning Iraq Vet, I do not hijack anything. I am just explaining facts; the net is saturated with misinformation and you saying that large subs need less power shows you need more experience in the industry. It is a matter of science, not debate.

Thank you for your service. I don't see where that gives you an advantage in discussing electromagnetic transducers. The only one that I know of with military experience related to this is Dan Wiggins of ADI. His background was in SONAR.
Yes, the net is saturated in "facts" about audio. I backed up my statement by referencing Hoffman's Iron Law. All things being equal, larger enclosures are more efficient and therefore require less power to reach the same SPL. If you want to take that up, it's J. Anton Hoffman's law.

 

[Robert_J]

Since I bent my rule, I might as well break it.

The number one cause of distortion is having too little power, or lack of quality wattage.
If a sub says, (which is typical), 500W-1000W RMS, 3000W peak the sub will sound best with a 1000W amp. (Although, you can and we on here often recommend you push 1100-1200W to it, it will likely take it and you can keep the gain down and know you can send it 1000W with no problems or clipping). Aerial Acoustics recommends getting an amp that is at least 70% of RMS - so a 700W amp would work for it (and not be too much quieter than the 1000W amp), some but not much). I have seen some setups on Aerials, or (less expensive ones) with as little as 41-56% of RMS, so you could use a 400W-500W amp with the sub, but that is about the limit for it to play decently.
The specs say AT LEAST 500W b/c they need that to sound good. But they sound best with 800-1200W.
They include the lower number b/c if that is all you have; a company they still want you to buy their sub. It is very similar to Microsoft newer OS’s claiming it work with a certain level of RAM, but I think it likes ten times the recommended RAM, although more than that is not much benefit.
Bottom Line - if you can only get a 500W amp, it will still play that sub, but it would do better with a 500W RMS sub, and that sub would do better with a 1000W amp.Bass requires lots of power. More power means cleaner bass, less power is muddier, regardless of cone size, magnet size, excursion, and enclosure design. Just power match your driver with your amp.

There are two ways to look a determine the power handling of a low frequency driver. The most common is thermal power handling which is how 99% of all raw drivers are rated. The other is mechanical power handling. With low frequency driver, that power rating is totally dependent on the enclosure they are installed in. There are times when 500w of power will drive a sub to it's xmax in it's enclosure.
Since you bring up distortion, as a driver's coil moves to the limits distortion increases. One of Mr. Wiggins' inventions is a sub motor structure that flattens the BL curve so that magnetic strength is constant throughout the stroke and distortion is kept to a minimum. I've used his XBL^2 sub drivers and like he stated here at HTF years ago, they sound great right up until failure. It is true in that they don't show any signs of stress until you hear the failure. I destroyed a sub rated at 250w of thermal power handling by sending it 250w of clean power. It sounded great right up until it seized.
Therefore, it isn't always the amp causing distortion.

 

[aerialacoustics]

Thanks Robert for your gratitude on my service. Many people take it for granted.
Have you seen Danley Labs Matterhorn? I was working with Rockford when someone told me of Toms latest design. This is the Army’s version of the making of the world's largest subwoofer. 40,000 watts of pure power! Built out of a 20' x 8' x 8' shipping container for a military requirement. It will do 105 dB @ 250 meters. See details at www.danleysoundlabs.com.
Here it is on You Tube:

 

[Robert_J]

The Matterhorn is legendary in the DIY forums. It was probably the first introduction of most to tapped horns.
If you worked in the industry then you know the big names. A lot of them hung out here when there was an active DIY section. It was like going to school every day when I logged in.
I'm not in the industry, I'm just a subwoofer enthusiast who likes to experiment when time permits.

 

[VanillaRice]

Ok that's enough time to review my m6as mission sub.
Please remember I've never had a worthy home sub before so I don't have a benchmark to go off. But all things considered overall I am happy with this sub.
Things to note are:
This sub (and I'm sure with all home theatre subs) is very critical on placement. I'm positive after much testing I have found its sweet spot. I'm very surprised at how loud it can be at my couch but if I go 2 steps around a corner into my kitchen, the sound of the sub almost dissapears although my plates are still rattling. This is quite annoying if I want to listen to music in the kitchen as all the bass seems to go to the couch.
It goes deep and thumpy for those impact scenes in movies (this is essentially what I wanted out of it)
As you know I bought this sub second hand for a good price (remember price is relative as New Zealand is stupidly expensive for home theaters compared to the states)
Would I have bought this sub brand new for $835nz which is the cheapest I can find it? Probably not. But then again, except for a DIY job I wouldn't have been able to afford a sub with these kind of specs, especially with a 350rms amplifier.
Another problem that I've picked up on is a humming/buzzing noise from the sub when it's not playing. It only happens when my AVR is turned on. It doesn't do it when the AVR is off. You can hear it regardless of whether the sub is on or in standby mode. It seems to only do it when I'm watching TV through my SKY TV satellite decoder. It might be a problem with my rca cable. I bought a cheap length of 15meters for testing around my lounge room. I may just buy some good quality stuff of maybe 2meters but there is a lot of miss information out there about the benefits of this expensive composite cable. I have a feeling something more complicated is going on. The buzzing kind of pulses and stays on for about 10 seconds off for 5seconds and then comes back again.
But in a nutshell I'm happy. Next on my list is some decent floor standing speakers. I listened to some Wharfdale CR30.4's today and they didn't sound all that great. The only demo music the guy had was Brooke Fraser and my musical taste is the polar opposite. They look cheap to me as-well. I've found a pair of Polk TS 1400's for about $100NZ more and reviews seem good. But after buying a new AVR and this sub I think I've blown my budget for the month.

 

[Al.Anderson]

Another problem that I've picked up on is a humming/buzzing noise from the sub when it's not playing.

That could be a ground loop. If both the sub and the receiver are plugged into the same circuit (even if they're on different sockets), move one of them to a different circuit.

 

[Robert_J]

It seems to only do it when I'm watching TV through my SKY TV satellite decoder

How is the satellite receiver connected to the AVR? If you have the ability to connect it via an optical cable, that will eliminate any ground loops. Also, is your satellite dish grounded? Depending on your house ground, that could cause issues.

 

[VanillaRice]

How is the satellite receiver connected to the AVR? If you have the ability to connect it via an optical cable, that will eliminate any ground loops. Also, is your satellite dish grounded? Depending on your house ground, that could cause issues.

HDMI from the satellite receiver to the AVR. I have the option to use optical though. I've never been on the roof but I will try and get up there and see how / if the dish is grounded

 

[Robert_J]

I've never been on the roof but I will try and get up there and see how / if the dish is grounded

There will be a visible wire running from the dish or a nearby coaxial coupler to a ground spike in the dirt or to a water pipe in the ground.

 

[VanillaRice]

There will be a visible wire running from the dish or a nearby coaxial coupler to a ground spike in the dirt or to a water pipe in the ground.

Ok thanks,
Now back to the optical connections, I'm a bit confused as to how I link my satellite tv video picture (HDMI Cable) with my optical audio through my AVR. Because if my satellite tv is coming through video1 on my AVR via HDMI cable, surely it will opt to just play the audio that came on the same cable. Unless there is a feature to select an alternative audio source through my AVR? Its a Sony STRDN1020 which should be new enough to handle that sort of thing.

 

[gene c]

You should be able to assign (select) the optical audio and hdmi video to Video 1 in the Sony's Input Setup menu.

 

[VanillaRice]

Ok, I will get a new optical cable and see it if fixes the problem.

 

[Robert_J]

With Gene's description, it will allow you to test to see if there is really a ground loop between your AVR and your sat receiver.

 

[Dave Moritz]

Polk Audio makes some nice subs for a reasonable amount of money. You can also check out Velodyne, Klipsch, SVS and Tannoy!
http://www.newegg.com/Product/Product.aspx?Item=N82E16882290130
Here is some of what I am using:

Pioneer Elite SC05 7.1 channel surround sound receiver (130w X 7 @ 8 Ohms)

Polk Audio PSW Series PSW505 12" Powered Subwoofer

Vintage Altec Lancing A-7 Voice Of The Theater

 

[VanillaRice]

I've finally found time to mess with my gear and try to get rid of my subwoofer hum.
It turns out that the hum is there with no input lead even connected. So I suppose the hum is coming from the mains, the AVR or the Sub Amp. I don't believe its a problem with my new sub because I just tried my old active sub and it's got the same hum only it's even more noticeable with that one.
To the person who recommended I try the amp on a different circuit, that's going to hard to do because everything on this level of the house is on the same circuit breaker. I think I will run a temporary extension chord from my garage to power my sub and see if that makes a difference.

 

[VanillaRice]

Polk Audio makes some nice subs for a reasonable amount of money. You can also check out Velodyne, Klipsch, SVS and Tannoy!

That's a nice setup Dave. I already settled on a mission M6AS sub. I've also added my old 30W active sub to make 380RMS of bass which seems plenty for my lounge room. Until I get used to it at least.
I'm really annoyed, I just lost my chance to score some Polk Tsi 400's for half price. Now the shop has doubled their price arghh!
It's a co-incidence you mention Tannoy as I've been watching two auctions for a pair of "Tannoy Sensys 2's" both auctions are due to close tomorrow morning so I have a price in mind and won't go over it.
http://www.trademe.co.nz/Browse/Listing.aspx?id=489606193
and the other one
http://www.trademe.co.nz/Browse/Listing.aspx?id=489638881