How much sub is needed???

[Tom Adams]

We talk an awful lot about a sub's performance numbers or how well it performs with certain speakers or with music or with movies or whatever. But I don't really recall any discussion about how one determines how much sub is needed for a given room.

Ok....now before anyone says it - STOP!!!! I don't care to hear any comments like, "You can never have too much" or whatever. I'm being serious here. I know there's bass addicts like TheEar (BTW - where is that dude? Haven't heard peep, I mean, boom [] from him in a while), but what I'm trying to find out is how does one quantify the amount of bass a given room volume needs?

Maybe the question should be rephrased to: "What would constitute not enough bass for a room?" I mean, how does one know up front that a single RSW12 or Def Tech SuperCube or HSU or Sunfire or Earthquake SuperNova or whatever won't "git 'er done" in a room this-by-this-by-that?

And yes - I know a single Danley will conquer all. Leave that monster out of this. That damn thing is like taking a popsickle stick to a gunfight.

Ok....I'm all ears. Let's hear it! []

Tom

[jacksonbart]

Unfortunately its very difficult to really know unless you can demo a sub in your room, but that being said you can never have too much bass. (hey I live in Hong Kong you can't reach me)

[Colin]

Well, first, you have to know where your main spkrs roll off where is the bass missing? If you sub peaks at 40Hz and most of the modest priced ones do and your spkrs go down to 40Hz, you will have lots of boomy, muddy bass (unless you turn the sub so low you cant hear it, which is a waste of money).

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Second, how much output are the mains capable of, because your subwoofers need to be able to put out about the same amount. In other words, if your spks can hit 114dB, you need a sub that can crank that high also.

Of course that also depends on if you are seeking for musically flat frequency response or merely want lots of punch (which huge and cheap JBL bass bins can give you).

[H]

[steamer]

Tom,

My room is 14'x29'x8' narrowing to 11' at one end,the 3' missing is a closed stairway to the upstairs.I have had mostly Velodynes in the system,a couple 15's(one at a time)and a 2x12 setup.They all kept up with my Scala's to a point.I now have a BagEnd system consisting of 2x18/ELF integrator-x-over powered by a Bryston 4B proamp.The BagEnd subs probably seem like overkill but this is the best bass I have had in my system and not because there is more.They do cruise like a bigblock.The BagEnds integrate so well in the system,very musical,never standing out.This is important to me.I am not saying more is better just that quality and the ability to blend with the mains is very important.2 18's seem to breath life into the room and are effortless.1x15 Velodyne has great specs but could not keep up in my room and I never felt it blended as well as what I have now.In fact a friend familiar with my system when hearing the BagEnds for the first time said"I cant believe how balanced everthing sounds.And you can hear every note,there is impact at low volumes.You always had to turn it up with the Velodyne to get that".

I agree with what Colin said and also every room/system/listener is different.

Greg

[chops]

We talk an awful lot about a sub's performance numbers or how well it performs with certain speakers or with music or with movies or whatever. But I don't really recall any discussion about how one determines how much sub is needed for a given room.

Maybe the question should be rephrased to: "What would constitute not enough bass for a room?" I mean, how does one know up front that a single RSW12 or Def Tech SuperCube or HSU or Sunfire or Earthquake SuperNova or whatever won't "git 'er done" in a room this-by-this-by-that?

Ok....I'm all ears. Let's hear it! []

Tom

REVIEWS, REVIEWS, REVIEWS!!!

When I am interested in a certain product in my price range, I hit the Google search for "such-n-such reviews" and see what comes up. Generally, these kind of searches (depending on what it is) will bring up results from dedicated stereo websites, online stereo mags, Audiogon, Audioreview, a plethora of forums, etc, etc. You will be able to read reviews from the pros as well as novice and advanced comsumers. Unfortunately, you will also see a lot of reviews by people that don't know their "A" from a hole in the ground.

Anyway, in a lot of these reviews, the reviewers sometimes give a discription of their room and system. From here, I can usually get an idea of what might work in my situation. Also, you can usually pick up a few tips here and there about calibration and placement.

This is exactly what I did a few weeks ago before I bought my twin EQ Supernova's. I did searches on the SuperNova MkIV-10, Sunfire Super Jr and Def Tech Super Cube III. I figured these three subs might have similar performance results in the real world consiering their size, price and somewhat their specs.

Also, you have to keep in mind how you use your system, what you're looking for and how you think it might go with your existing equipment/room.

Since I play my system loud and prefer overkill, I decided to go with two subs for my system. I already have a basic understanding of acoustics and such, so I know that using twin subs reduces distorsion, doubles the overall output, can help extend the bass a little more by sheer output, and can help even out room modes if properly placed. Also, knowing that my CWs are very efficient, I felt that just one SuperNova may not cut it, at least not one MkIV-10. The 12 or 15" version probably wouldn't have any problems, but those are well out of my price range at this point.

Another thing I considered was the fact that because the CWs are fast and offer up plenty of detail, I knew I needed subs that could keep up. Naturally, going with a smaller sealed sub or one with passive radiators would need to be on my list. And since my stereo's duty is 95% 2-ch music and 5% movie, I was more concerned with a musical sub. In other words, I was not looking for a subwoofer that plays down to 10Hz at 100+ dB, but something that could at least hit 18-16Hz at -3dB or so, which these SuperNova's can do, especially with two of them running.

Anyway, that's my take on it.

[CAS]

That question is about as subjective as saying, "How much house is enough?"

In my opinion, it's this simple. Your sub should do 3 things:

1- go as low as you wish (20 hz, etc)

2- transition smoothly from your satellites (similar to number 1 but on the other side of the band)

3- do all of this undistorted at the maximum calibrated output (or a few db's hot to make sure) of your satellites

Minus lots of other characteristics like clarity, flat response, etc....Output-wise, if it can do the above 3 things then it's enough sub. Easy.

[Buckeye_Nut]

Or, how much beer is enough on movie night?

[]

[TheEAR]

TheEAR lost his password and got lazy,spending time listening to new products.Buying many new products(including subs!). []

The correct sub for your room is a subwoofer that will meet your max expected listening volume(at listening position SPL)with no audible distortion or any kind of audible mechanical noise.

This said its a very personal thing.If someone has a formula their are full of BS. User A in a small room with plenty of gain will find a large sub is just perfect while user B in a larger room will may fnd a much less capable sub perfect.

Take some subs home and try them out,as empty forum filling talk will not solve much. I have 19 subs at the moment(not counting any bass modules [] ) and I will add more. []

[sunburnwilly]

Buy the biggest one you can . And then tune it to the room .

[DrWho]

what I'm trying to find out is how does one quantify the amount of bass a given room volume needs?

Maybe the question should be rephrased to: "What would constitute not enough bass for a room?"

There are two variables to consider: bandwidth and output.

To determine the necessary bandwidth capabilities you will need to

go to your source material and run some waterfall plots to get an idea

of how low your recordings go. A sub doesn't constitute enough bass

when it cannot reproduce the low notes present on your recordings.

To determine the necessary output capabilties you need to again go

to your source material and measure the relative of peaks to the

average signal. You then need to measure the average and peak volumes

of your system at normal and loud listening levels. Once you figure

this out you can refer back to the measurements of the source material

(waterplots) to get an idea of how much headroom your system needs in

order to accurately reproduce all the peaks.

These are pretty simple tasks to complete...all you need is some

free software, a dvd-rom on your computer and an SPL meter ($30 from

the ratshack). What you will find is that peak levels of 130dB and

extension down to 15Hz really aren't insane goals to strive for.

One thing I want to mention, but not get too much into is the

nonlinear behavior of the system. It's kinda hard to quantify into a

simple variable, but in an ideal world the more overkill the system,

the more linear it will behave. Linear is a good thing []

In the practical world one needs to determine what is economically

and aesthetically feasible for one's situation as it will usually

dictate a performance level far below that of the ideal (whatever it

measures out to be). In the off chance that the aesthetic and economic

limitations allow one to exceed his needs, then consider the extra bit

of overkill a means to increase the overall linearity of the system.

[Tom Adams]

(shaking his head Tom sighs and tries to figure out how better to phrase the question)

Ok....let's try this again..........

What I'm trying to determine is partially based upon a question that Velodyne and SVS and others asks when you quiz them for a sub recommendation. And one of the questions they all ask is: "What is the size or volume of the room?" To me, that indicates that the volume of the room provides a jumping off point, if you will, as to how much ?????? one will need.

I'm not so dense or stoopid that I don't know to listen to a bunch of subs or take measurements or buy the biggest you can afford or blah, ba-blah, ba-blah........

(sorry - I'm frustrated this morning)

Anyhow.....surely the rooms' volume is enough of a factor that it allows one to predict that a single 8" sub won't do the trick, but that a good STARTING POINT would be a single 12". Or that maybe dual 12's would be a better STARTING POINT start than a single 15".

Am I making any sense now or do I just need to quit while I'm ahead and go take more medicine??

Tom

[steamer]

Ok Tom,

Lets try this again,how big is your room?What speakers will you be matching the sub or subs to?Is this a 2 channel or HT setup?What kind of music do you like?Lots of factors to consider here.

Maybe if we have more info we can give a better recommendation.

Greg

[MrMcGoo]

The big problem with subwoofers is the uneven room response. Peaks and nulls are as big a problem as not enough output and much more difficult to solve.

If you have two or more good locations, then dual subs are a major possibility. Dual subs may help smooth out room response and increase output a bit.

My recommendation is to wait for the Klipsch RT-12d and 10d subs if you have good corner(s). The room response will be automatically tuned for you and you can select the type of EQ that suits your needs. It looks like you can switch the EQ with the program material.

Movie subs are tuned differently than most music subs. Movie subs are frequently tuned to go lower at the expense of lost total output. Music subs tend to be tuned a bit higher and have more total ouput.

Movies are sooo bass intensive today that many say that there is no such thing as too much bass. Bass goes dwn to 10 Hz on some major movies such as War of the Worlds. You cannot hear it, but you can feel it. Many subs have a subsonic filter to eleminate anything below 16 Hz to avoid damage to the sub.

Bill

[Fish]

I'll take a shot at it.You need atleast two decent 10-12"subs in more

than a 400 sq ft room.This is based on nothing but my preference but

its short.

[Olorin]

It's a tough question to answer for someone else. The big guys in the trade probably have the the right questions figured out and can give you a recommendation that will most likely satisfy you. One hobbyist's opinion may or may not be helpful to another hobbyist, though. When I saw your subject on the main page, the first thought that came to mind was "All of it." []

[Tom Adams]

FWIW - this isn't for me or anyone in particular. I already know what I'm gonna do. Where I hope this would go is for someone to say, "Well, you take the total volume of the room, multiple it by the square of the hypotenuse (sp?) of your largest window, then divide it by the geometric tolerance of a typical interference fit fastener which will give you X. Then you take X, add your age and there you have Y which equals the cone size."

I quit. [] [] [] []

Tom

[formica]

There are several factors which are unknown to be able to make that kind of generalized prediction.

- subwoofer maximum output at a given THD and frequency (not the marketing numbers)

- room response / modes and where you are positioned in relation to them

- desired bass extension and volume

Same as with speakers... size, wattage, etc... don't tell us much about

the unit's performance. You can have a 10" sub which greatly

outperforms a 15" one depending on it's design. The numbers spit

out by manufactures are mostly marketing tools and don't tell the whole

story.

If you were outdoors... you can look at the subwoofer's anechoic output

and calculate a 6db loss for each doubling of the distance (ie: 110db

at 20Hz at 1m spec would give 104db at 20Hz at 2m sitting

distance). Place the subwoofer up against a wall... you have a

3db gain due to boundary effect. Place the subwoofer up in a

corner... you now have a 6db gain due to boundary effect (ie: 110db at

20Hz at 1m spec would give 110db at 20Hz at 2m sitting distance with

the subwoofer in a corner).

Ok, sounds simple... BUT now you have to look at room response...

The big problem with subwoofers is the uneven

room response. Peaks and nulls are as big a problem as not enough

output and much more difficult to solve.

Yup... it can easily vary output 15db... which is very

significant. This, we already know varies with room

geometry. Giving approximate room dimensions only give a general

idea of resonant peaks. I'm not sure what people do with the "I have a

16' x 30' x 8' room with openings to..." statements posted. If

they aren't calculating room modes, then only the distance from the

speakers can give a quick and dirty idea of volume.

Bass extension is another limiting factor; given the lower you want it

to play... the more air displacement you'll require. I enjoy it

low and loud... so I realise I'll demand more than some other

people. When people ask... music or HT, they are assuming

that music enthusiasts are willing to sacrifice both SPL and Hz, which

isn't always true.

So... as an actual answer to your question... I'd say "42" ...

ROb

[formica]

Where I hope this would go is for someone to

say, "Well, you take the total volume of the room, multiple it by the

square of the hypotenuse (sp?) of your largest window, then divide it

by the geometric tolerance of a typical interference fit fastener which

will give you X. Then you take X, add your age and there you have

Y which equals the cone size."

Like this? http://www.myhometheater.homestead.com/splcalculator.html#anchor_13193

BTW, what will you be doing in your HT or is there already a thread?

ROb

[DrWho]

FWIW - this isn't for me or anyone in

particular. I already know what I'm gonna do. Where I hope this would

go is for someone to say, "Well, you take the total volume of the room,

multiple it by the square of the hypotenuse (sp?) of your largest

window, then divide it by the geometric tolerance of a typical

interference fit fastener which will give you X. Then you take X, add

your age and there you have Y which equals the cone size."

I quit. [] [] [] []

Tom

Ok, here's the short answer...the reason these companies ask about

your room dimensions has absolutely nothing to do with the performance

of the driver. It mostly comes down to making the customer feel like

they're being taken care of. It is also so that they can suggest a model

that will be aesthetically acceptable - ie, not so big that the

customer gets pissed off (who wants a 20 cubic foot cabinet in a 10x12

room?). You aren't talking to an engineer on the other line...you are

talking to a sales rep.

______________________________________________

Anyways, I know that's not the answer you wanted to hear...so allow

me to comment on what I think you're elluding to and then I will point

out why it doesn't matter.

As we all know, the room has a huge influence on the bass output of

the system. The room mode issue has been discussed and though it's a

huge factor - it doesn't really play into the design of the subwoofer.

However, there is the lowest mode frequency which is the standing wave

that occurs between the tangential corners of the room: draw a line

from the front left corner of the room on the floor to the back right

corner of the room up by the cieling. This distance will correspond to

the wavelength of the lowest mode. The formula for this distance is

just pythagorean in 3-D which is: SQRT((H^2)+(W^2)+(L^2)). This is an

important frequency because below this point the subwoofer starts to

act as a room pressurizer and not so much as a sound emitter...

Allow me to go off on a tangent and mention that the pressurizing

behavior does not mean the particular note sounds different. There is

one of those audio myths floating around that a wavelength that can't

fit in the room doesn't sound the same as the same wavelength that can.

For example, you have two rooms, A and B. A has a diagonal distance of

20 feet and B has a diagonal distance of 40 feet. The myth would state

that a 32 foot wavelength signal would be percieved differently in A

than it would in B - even if they were the same volume at the listening

position. This is however not the case...

So anyways, below the lowest mode frequency the subwoofer is

essentially pressurizing the room. The net effect of this behavior is

what we call room gain which in an ideal world is a 12dB/octave boost

in the frequency response (I hesitate to post a number like that

because it's almost never the case).

So what do we do with this room gain? A lot of people try to

implement a subwoofer that has a 12dB/octave rolloff beginning at the

point where the room gain starts to occur. And I guess in a way it

makes sense because you will measure a flat frequency response when you

pink noise the system. This is however a totally wrong approach...an

approach I was corrected on after talking to a few professional

subwoofer engineers in the field. So here's why:

The ultimate goal of the sound system is to be a perfect

reproduction of the recording...essentially an attempt to put the band

in your room. Keeping this in mind, every room has its own "transport

function" which is just a fancy term to refer to the sum total of all

the room gain, reverb, etc etc...With no music playing and your eyes

closed you will notice that you can almost hear the spatial attributes

of the room...basically you are hearing yourself with the transport

function of the room. All that to say, because the recording itself

does not have the transport function of your room built in, you will

need the transport function of the room to be applied to the sounding

coming out of the speakers so that it is percieved as being in the same

room as yourself. In other words, a kick drum playing in the corner of

your room is going to have the transport function applied to it...why

then wouldn't you want the kick drum on the recording to have the same

effect? I know I'm not explaining it well, but it's the best I can do

right now...it is definetly a topic in the realm of psychoacoustics.

The issue gets a bit more confused when you start talking about the

effects of boundary gain...which are in no way related to the effects

of room gain. Boundary gain is what occurs when you reduce the amount

of directions in space the driver is pushing sound into. Free space would be like a

speaker floating in the middle of the air - sound radiates into all

directions. Half space would be like a speaker sitting on the ground -

sound radiates into half of the possible directions (ie up and not

down). Quarter space would be a speaker sitting on the ground pushed up

against a really wide wall. Eighth space would be a speaker sitting in

the the corner of a room. Room gain is a function of how the sound

"bounces" around the room which will be a function of the dimensions of

the room - so boundary and room gain are two totally different things. Anyways, the point here is

that you want to compensate for the effects of boundary gain because

you do not experience those effects when sitting at the listening

position (you are sitting in the middle of the room, not the corner).

Getting back to the practicality of all the theory (which I totally

just botched up), you do not want to compensate for room gain. And all

commercially available subs are measured in the corner, which means the

effects of boundary gain have already been compensated for. But if you

position the subwoofer out of the corner (say along the middle of the

front wall), then you no longer have all of the boundary gain from the

original design and therefore the sub will be a bit lacking, requiring

some EQ to bring it back to the "ideal."

So what happens if you build a sub to be awesome outside and then

bring it into your HT and put it in the corner? Well, you will have way

too much fricken bass...but really this isn't a big deal because you

can just implement some EQ to tame it back down to normal....which will

in turn reduce the cone excursion and ultimately reduce the distortion

of the system. And this is why you can never have too much (because you

can always turn it down). And this is why subwoofer companies have no

problem letting sales-reps answer these questions for their customers

[]

So ya, I know it turned out to be a long post, but hopefully the question got answered somewhere in there...

[johnyholiday]

more overkill the system, the more linear it will behave. Linear is a good thing Wink [][Y]