One or Two Subs

[Tommy]

pierrebnh wrote:

How many sub outs do you have? Many AVRs have 2. Otherwise a Y-splitter with each sub having their own EQ I would think gives the best results.

01
I dont see anything on the back of this receiver marked exactly as sub-out, is it named or initialed somthing different?

02
Also, I know your not supposed to mix speakers does the same go for the subwoofers, I sent the in-wall MTX sub back but when I buy a floor standing sub now does it still need to be from MTX?

03
Ok I know the subs get different type of wire then the speakers but exactly what of wire?

04
I saw something about having it precut to lengths with the connectors already added. Can I order it like the speaker wire on a spool and cut it where I need it? Or do I need the fixed lengths?

05
If I am cutting it what type of connectors & tools do I need?

06
Going thru the sheet rock, what type of boxes/plate covers do I need to either run the wire out of it or which would even look nicer is there someway to terminate it at the box and then on the outside screw it to a connection piece on the box plate?

[rcarlton]

Sonnie wrote:

I still question too how much stereo sub information is present in the LFE channel... I've always thought it was mono... Maybe I'm confused... which wouldn't be a surprise.

Turns out the LFE channel is mono!

[kingkip]

Tommy wrote:

02
Also, I know your not supposed to mix speakers does the same go for the subwoofers, I sent the in-wall MTX sub back but when I buy a floor standing sub now does it still need to be from MTX?

No, that isn't necessary. The timbre matching usually has to do with the tweeter. Get a sub that can fill your room and sound good to you. Or whatever other qualities you need for it.

Tommy wrote:

03
Ok I know the subs get different type of wire then the speakers but exactly what of wire?

Decent shielded rca

Tommy wrote:

04
I saw something about having it precut to lengths with the connectors already added. Can I order it like the speaker wire on a spool and cut it where I need it? Or do I need the fixed lengths?

You can but then you have to terminate the cables yourself. Soldering skill, an iron and wire strippers, though not terribly difficult. You can get decent factory cables starting at around $20 or so.

Tommy wrote:

05
If I am cutting it what type of connectors & tools do I need?

See above

Tommy wrote:

06
Going thru the sheet rock, what type of boxes/plate covers do I need to either run the wire out of it or which would even look nicer is there someway to terminate it at the box and then on the outside screw it to a connection piece on the box plate?

Home Depot, Lowes etc sell RCA wall plates or speaker terminal wall plates and the like.

[kingkip]

Sonnie wrote:

Hey Ron.... he seems to recommend stereo subs... but this would be hard for most wouldn't it? Most sub pre-outs are mono I think aren't they?

I still question too how much stereo sub information is present in the LFE channel... I've always thought it was mono... Maybe I'm confused... which wouldn't be a surprise.

Really only financially hard. All you have to do is use a y-cable to split the signal and then run it to both subs. With big enough subs I suppose it would be physically hard to position them though.


It absolutely is mono. However when you use the LFE out it sends all the signals (from all of the channels you are using ie 2, 5, 6, 7 whatever) below what you have the xover set at in the receiver to the sub. Since sound at those freqs are omnidirectional it doesn't matter that it only comes from one place.

Where two subs usually help is with displacement and with good positioning can help cancel out some nulls.

[kingkip]

Josuah wrote:

An infinite baffle supposedly requires double the drivers because you are throwing away the reverse excursion? This is what I've heard at least. It's supposed to sound cleaner also as a result, because you never deal with the reverse excursion, which is not going to be identical to the forward excursion.

You aren't thowing away the back wave. If that were true a sealed subwoofer (which is what an IB is on a grand scale) would require double the drivers as well, as the back wave can't escape the box. Why you typically need more drivers in an IB is because you lose the accoustic suspension provided by having that sealed box. In a typical sealed box the air trapped in the box compresses as the driver move in and resists the driver, making it harder for the driver to bottom out. In an IB since the "box" is so large there is no air "shock absorber" and therefore it is easier to bottom out the spooks. More drivers mean more displacement which means more SPL for less movement from each driver and there is your protection.

BTW if you don't believe me about throwing away the back side, sit in the room on the back side of the IB during U-571

[Fincave]

Tommy wrote:

01
I dont see anything on the back of this receiver marked exactly as sub-out, is it named or initialed somthing different?

Page 13 of the manual reads something like "CONNECTING A SUBWOOFER. Use the PRE OUT SUBWOOFER jack to connect a powered subwoofer (powered amplifier built in)" On the rear panel of the SR 7500 it is marked as SW PRE OUT, am not meaning to be sarcastic but it really is worth taking the time to read the manual carefully. Receivers can be a bit complicated as they have a wide range of features and options.

[Sonnie]

I can see Tommy now...

[Steve Williamson]

You know I understand sub inputs

This a pic of the back of mine, left and right line in, left and right line out, left and right speaker in and left and right speaker out.

Now I'm confused, and I've buried my manual somewhere whilst we pack for moving.

My receiver only has one "subwoofer pre out" labelled on the back next to the pre out for the rear surrounds.

[JimP]

Steve,

This can be confusing.

What you are seeing with all these ins and outs is where you are using the sub's crossover to seperate the frequencies that the sub is responsible for from the ones that go on to the speakers.

You basically have 3 different options.

1st. Use the receiver's crossover and send the sub out signal from the receiver to the line in input (either left or right will do). When you do this, you do want to turn the crossover on the sub to the highest setting to avoid the effects of a double crossover. This is probably the best setup for home theater.

2nd Use a preamp's stereo left right line level output to the sub's line level input and then route the sub's line level output to an amplifier. In this example, you'd want to disable the crossover in the preamp and use the crossover on the sub. This would work best when you're using the the sub for stereo as the low frequencies for the other channels in a home theater setup would not be routed to the sub.

3rd Last but not least, route the left right speaker output from the receiver or amplifier to the sub's left right speaker input and then route the left right speaker output to the speakers. This primarily works for stereo.

Thinking outside of the box here, I have a variation that you guys might be interested in. I have a 7.1 system where my front mains, center channel and side surrounds are set to small and the low frequency information is routed to a sub located at the front of the room between the TV and the right front channel through an equalizer (velodyne SMS-1). Now here is things get interesting. My back surrounds are set as "large" in the preamp and the speaker level out from the amplifier first goes to the "speaker in" on a subwoofer located at the back of the room then on to speakers. The sub in the back of the room crossover is set at 80 hz, the same as the preamp setting for the other speakers. What I gain with this is a more 3 D effect of the sub frequencies. Imagine a battle cruser fly by with the lower bass located at the front of the room and the rest of the sound going from the back of the room to the front of the room. Now imagine the same fly by when all the sound originates from the back of the room then all moves forward to the front of the room. Since I'm using fairly significant speakers all the way around (flat to around 50hz) and that I'm using them at roughly a 80 hz crossover, that many other options exist as to setup. Although I like what I'm hearing (after much experimentation) when the mad scientist gene kicks in again, who know what I'll try next.

Edit: One thing that I tried and did not like is where I ran both the front sub and the rear sub off of the sub output of the preamp. I also used the Velodyne SMS-1 equalizer for the front sub. I spent days getting everything calibrated and what I wound up with was having the sub frequencies always coming from the middle of my head. Cute at first, extremely annoying soon thereafter. In retrospect, this might have been better with a 50 hz crossover where there is less information going to the subs between 80 and 50, but with a 80 hz crossover, you constantly have this pounding going on that is overkill.

[Tommy]

Sonnie wrote:

I can see Tommy now...

hahaha sonnie, I'll get ya back for that one...

Fincave wrote:

Page 13 of the manual reads something like "CONNECTING A SUBWOOFER. Use the PRE OUT SUBWOOFER jack to connect a powered subwoofer (powered amplifier built in)" On the rear panel of the SR 7500 it is marked as SW PRE OUT, am not meaning to be sarcastic but it really is worth taking the time to read the manual carefully. Receivers can be a bit complicated as they have a wide range of features and options.

Ok I'm not that bad and will always fully read the manual before actually touching anything unlike most people. But for the quick reference of answering how many output jacks I have, I did not bother to open the manual as of yet.

BTW Fincave, thank you mentioning the Pre Out was what I was getting at as far as asking if it was named something else.

[Tommy]

Thank you Kingkip this also answers some of my questions.

I guess what I'll plan for then is behind the wall I will run pre-cut terminated wires, one wire to the far corner on the back wall and one wire to the front of the room (same side) and have both connected to there own wall plate.

Then I'll get a seperate wires that run from the wall plate to the subs after I figure where exactly they'll sit.

Does this sound right?

kingkip wrote:

No, that isn't necessary. The timbre matching usually has to do with the tweeter. Get a sub that can fill your room and sound good to you. Or whatever other qualities you need for it.

Decent shielded rca


You can but then you have to terminate the cables yourself. Soldering skill, an iron and wire strippers, though not terribly difficult. You can get decent factory cables starting at around $20 or so.


See above


Home Depot, Lowes etc sell RCA wall plates or speaker terminal wall plates and the like.

[kingkip]

Tommy wrote:

Thank you Kingkip this also answers some of my questions.

I guess what I'll plan for then is behind the wall I will run pre-cut terminated wires, one wire to the far corner on the back wall and one wire to the front of the room (same side) and have both connected to there own wall plate.

Then I'll get a seperate wires that run from the wall plate to the subs after I figure where exactly they'll sit.

Does this sound right?

That should do it.

[Tommy]

Sonnie wrote:

Remember your room is almost the size of mine and I have two SVS PB12-Plus/2's. I had just one hooked up for a night and then hooked the other up the next night... NO lookin' back! I can't figure out how I ever lived without two... and for those two subs you actually get 4 x 12" subs with about 1800 watts total power.

Two of them, aint they like 1,200 each? [Filtered word here], I want the room to shake but not sure if I want to spend that much extra.

I thought I was doing well bumping it up from one $500 speaker to maybe two or just getting one speaker that is better.

[Tommy]

Sonnie wrote:

Remember your room is almost the size of mine and I have two SVS PB12-Plus/2's. I had just one hooked up for a night and then hooked the other up the next night... NO lookin' back! I can't figure out how I ever lived without two... and for those two subs you actually get 4 x 12" subs with about 1800 watts total power.

Sonnie I ordered one SVS PB12-Plus/2's.

Those things are expensive at $1,200 each. I'll see how I like the one and how the whole room is before deciding if I should get another one.

I've heard different things saying whether or not Im gonna need a seperate amplifier. Is there a test I can run to show whether or not one will be needed?

[Josuah]

Separate amp? The PB12+/2 has an amp built-in.

[Sonnie]

Yeah... lol... where ever you heard you need a separate amp for that sub... you should stay far far away from... cause they stupid or ignorant or both.

What? ... you paid how much? You didn't get the 25% discount... did you not give them the coupon code? What were you thinking? You could have saved 300 bucks man! Now it's too late. It was only good through 12 midnight 5/31/06. Oh well... live and learn I suppose.


Well congrats on the sub... you will be excited... and one might be enough. Two would look prettier.

Hey no fair... you got the new drivers in yours...

Spoiler

Noooooo.... there is really no coupon code and there is really no 25% discount... you could not have saved 300 bucks. I'm just yankin' ya chain...

[Tommy]

Sonnie wrote:

Yeah... lol... where ever you heard you need a separate amp for that sub... you should stay far far away from... cause they stupid or ignorant or both.

What? ... you paid how much? You didn't get the 25% discount... did you not give them the coupon code? What were you thinking? You could have saved 300 bucks man! Now it's too late. It was only good through 12 midnight 5/31/06. Oh well... live and learn I suppose.


Well congrats on the sub... you will be excited... and one might be enough. Two would look prettier.

Hey no fair... you got the new drivers in yours...

Spoiler

Noooooo.... there is really no coupon code and there is really no 25% discount... you could not have saved 300 bucks. I'm just yankin' ya chain...

Hey sorry there was some miscommunication on my part. When suggested I get a seperate amp that was when I was trying to find a sub but didnt actually select or get this specific one yet.

But I did want to know if there was some specific gauge/test or stat that shows if your running it on enough?

Oh and ya did have me cursing here about the 25% discount, I'll get ya back for that one...

Let the prank wars begin...