[Big Picture]

I have the AT 450e THX speaker set with one 452 PBM sub in a 30X20X7'8" room and I'm quite pleased with the results. I'm considering adding a second 452 sub. Would this be overkill? Would it be bad in any way? Would it be a great thing to do?


All comments welcome.

 

[Rachael Bellomy]

Can you say ka-boom,that's good,I like the way you ka-boom! All I can say is why not!


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Ms. Bitchlist

 

[Buddy_Yaussy]

I'm no expert, but I'll post this anyway, because I also am considering adding a sub, and am interested in everyone's opinion.


I understand that adding a second sub can cause cancellation in certain areas of the room, even if one is wired or switched out of phase. This can be corrected for by moving them around, shifting phase, etc, but there will still always be some cancellation somewhere.


OK, a bold statement to throw out there, but here goes...


Would it not be smarter, since subs are nondirectional, to pick ONE AND ONLY ONE sub which is big enough to drive your room? That is of course not considering things such as budget and space constraints, etc, this is strictly from a performance perspective.


Buddy

 

[TV]



>>>I understand that adding a second sub can cause cancellation in certain areas of the room, even if one is wired or switched out of phase. This can be corrected for by moving them around, shifting phase, etc, but there will still always be some cancellation somewhere.<<<



That's very likely,but only if the subs are placed apart from one another. If someone wants to increase the headroom(or lower distortion for

a given volume),than adding a second identical woof, and placing it near the first will give you a 5 to 5.5dB increase in potential volume...with no additional *cancellation* issues to concern yourself with.


If you placed 4 subwoofers very near one another, they would for all intents and purposes...interact with the room boundaries as one large

subwoofer.



>>>Would it not be smarter, since subs are nondirectional, to pick ONE AND ONLY ONE sub which is big enough to drive your room? That is of course not considering things such as budget and space constraints, etc, this is strictly from a performance perspective.<<<



Ayup. Very often...a single POINT SOURCE for bass leads to the smoothest bass response over a variety of listening positions. Now--a single *point source* could be ONE enclosure,or it could be a half dozen enclosures tightly packed in a good corner.


I'm probably splitting hairs little here(if so, I apologize)...but there's really very little *downside* to adding additional bass headroom in someone's HT. In fact , I'd guess the majority of HT enthusiast are "bass-shy" if they like to listen to DVDs anywhere near reference levels.


TV

 

[Ray]

HI all

In most cases corner loading a sub will give you the loudest

responce because of the iteraction with the corner of the room

Positioning the sub or subs 1/3 in from each side wall will

give you the smoothest responce.The reason for this is because

in a rectangular room the first room mode that counts often

accurs 1/3 in from a side wall.Proper sub crossover setting

is also critical.If your front mains are full range (able to

play effectively below 50hz or so) Then set the crossover on

the subwoofer lower to "Blend" with the front mains.The gain

position on multiple subs may be at different settings

this is where a good test disk (Avia or vid essentials )

come in handy.If you are looking for the loudest responce

and dont have a corner handy here is a cheap trick.

Place the sub at the listening position and play the sub at

reference level with the test disk,now walk around the room

As you walk you will hear dips and peaks in the responce

place the sub where you hear the loudest responce

remember Patience is a virtue

Cheers RLA

 

[Big Picture]

Ray:


Are you saying my best option is to use two subs, each one being 1/3 from each of the front side walls?


Thank you.


Tom

 

[Ray]

Hi

Yes I believe you would be better off with 2 subs in that large

of a room.Another benifit of having 2 subs is that 2 subs

dont work as hard on demanding 5.1 soundtracks and are

less prone to bottom out or introduce destortion

Remember 1/3 is a good starting point for smoothest responce

not loudest.I find that 1/3 in from the side wall and an

spl level or 2-5db hotter than reference works very well

in multichannel applications. A common mistake by most

is to have the gain and crossover setting to high on the sub

IE if you front mains play down in the 40 hz region

try the crossover at 50 and work down from there

There will be less BOOM BOOM this way

Cheers RLA

 

[Ray]

Hi

I just noticed that you have the AT system.Crossover

on subs should be set at 80hz as per THX spec

Cheers RLA

 

[Big Picture]

Ray:


There is a THX switch setting past the 80HZ setting so I think I should use the THX setting, no? My pre/pro/amp is a Denon AVR 4800 (DD/THX/EX)


[This message has been edited by Tom M (edited May 16, 2000).]

 

[Rachael Bellomy]

If you were going to add a dedicated sub for the surround channels,where do you put it,a back corner? How will this affect the front sub/s? I have been considering this....Thanks for any ideas!


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Ms. Bitchlist

 

[TV]



>>>In most cases corner loading a sub will give you the loudest

responce because of the iteraction with the corner of the room

Positioning the sub or subs 1/3 in from each side wall will

give you the smoothest responce.<<<



I disagree. In general, the main problem associated with bass *smoothness* is the lack of room mode density <100hz. As the

Freqs lower, the modes become more widely spaced. Typically, to

realize the smoothest response over a variety of seats in a room, you want to excite as many room modes as possible. Placing a subwoofer in a corner excites the max number of modes, any alternate placement will not.



This isn't to say using the 1/3 method cannot lead to good results,but I'd try both the 1/3 method and the corner method and decide which one works best in your seating area.



>>>are looking for the loudest responce

and dont have a corner handy here is a cheap trick.

Place the sub at the listening position and play the sub at

reference level with the test disk,now walk around the room

As you walk you will hear dips and peaks in the responce

place the sub where you hear the loudest responce <<<




That can work...but it only works well if you are sure to use a wide variety of source material while deciding on the best location. If you use a RTA and sweeps , then I'd suspect you'd find the subwoofer works best near/in a corner anyway.


TV

 

[TV]



>>>If you were going to add a dedicated sub for the surround channels,where do you put it,a back corner? How will this affect the front sub/s<<<



I'd suggest adding more headroom to the main subwoofer, and simply rerouting the surround bass to the LFE/subwoofer signal.


1)you won't have to worry about all the headaches multiple woofs in multiple locations can cause.


2)*surround* bass is largely superfluous anyway. That is, in the rare occasions the surround channels do contain high amptitude signals <80hz, usually the front channels and/or the LFE channel will also contain nearly the same *bassy* signal.


3) in the ULTRA-rare occasions that the surrounds DO contain discrete bass signals...it happens for a few seconds of a handful of DVDs.(superspeedway,SPR,ect). So, you can either optimize your system for those few seconds, or for the rest of the time...not both.



When someone feels the need for *surround subs*, that may indicate a lack of headroom with the main woof. I'd examine that area first.


TV

 

[Rachael Bellomy]

Thanks! The Smart EX unit I installed has an output for a rear sub,I've already started wondering what if any thing to do with it...I thought maybe my present sub could move there and me'sa puta auh biggah sub on de front. I thought it might be problematic,you have convinced me that it's proably not worthwhile.....


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Ms. Bitchlist

 

[TV]



>>>Thanks! The Smart EX unit I installed has an output for a rear sub,I've already started wondering what if any thing to do with it...I thought maybe my present sub could move there and me'sa puta auh biggah sub on de front. I thought it might be problematic,you have convinced me that it's proably not worthwhile.....<<<



Well, it nevers hurts to experiement of course, just be sure to use a large variety of source material for each option. Also, I left out one of the most important reasons for not *needing* a surround woof...



While some folks feel a surround woof makes everything more realistic because of added sense of *rear bass*...actually, the cues we determine directionality with are almost always >80hz anyway.


TV