What is best size woofer/subwoofer for optimal bass response?

My friend and I recently got into a good discussion about woofer and subwoofer sizes and how they react in free air environments vs ported and sealed type speaker cabinets. So here is where the fun started. He said that 10" woofers and subwoofers are the best size for any low frequency application and can not suffer from major cone excursion. My argument was that the surround material and spider is usually made to be more stiff for different applications on most woofers. He insisted that larger woofers can never have a better bass response due to cone size as well. I can understand his views for possibly 15" or ever 18" woofers but I have never had any issues with any of the speakers I have that use 12" woofers. I don't see how adding 2" to the cone of a woofer could make that much of a difference?

 

OK, there is a lot to consider.

What is the best size for a sub-woofer is entirely dependent on a number of factors.

Just to start off, this is the best size for a sub-woofer for me (the cabinet on the left).



This is a horn load 15" passive commercial sub.

Now let's go on from there.

The first three considerations that I would first consider are; HT or for Stereo, what is the size of the room, what kind of material is being played through it?

There are many other considerations to consider, but I would start out with these three.

For HT the sub is the SFX of the movie, it exists primarily to make big BOOM sounds. In stereo, it is there to "augment" an existing primary speaker system, to achieve a deeper bass. With "normal" music, you should not even need to realize that there is a sub in the system, just that everything that you expect to be present in the music is there.

If you are a bass-head, then the sub would play an entirely different roll, obviously!

The, we need to consider the size of the room and the amount of LF information, that is needed to properly pressurize the air that room.

These are thy primary factors that I would consider when deciding the size of the sub and the power of the sub.

Going back to driver size and what would an extra 2" make a difference?

Since speaker surfaces can be anything from flat surfaces to cone shape. Let's just assume, for the purpose of this discussion, that we are talking about a circle of so many inches in diameter.

To move air, as specially at low frequencies, you have to couple the speaker driver to the air, in order to excite the molecules in the air. The more surface area, a LF driver has, all other things being equal, the more effectively you can pressurize the air in a give volume of space.

So let's look at speaker's sizes of different diameter's.

10" diameter = 100 square inches of surface area.

12" diameter = 144 square inches of surface area.

15" diameter = 225 square inches of surface area.

Consider a 15" sub as compared to a 10" diameter sub. Since the surface area is much smaller, the the sub would have to move further farther and backward to move the same volume of air. The move a speaker has to move, the more distortion it will produce.

It is a myth that large speakers, like a 15" size speaker are big and flabby. The opposite is true. A larger diameter driver will have to move less to move the same volume of air of smaller driver.

You don't have to be a Physics major to figure out that larger cabinets will produce more bass, it is a matter of physics. In the old days, speaker cabinets in theaters were very large. The original Altec Lansing A2, had huge dual cabinets which has dual 15" drivers in each cabinet and the bass cabinets themselves were 7' tall. Cabinets had to be large, because amplifier's were samll and movie "palaces" were also very large spaces, volume wise, to fill with sound. A single A2 cabinet weighed around 2,300-lbs.

Here are some Altec Lansing heritage speaker's.



The A2's were typical of what would be behind theater screens back in the 40's. Smaller movie theater's of the 50' and 60's would typically have the A2 cabinet's behind the screen. The A5, was produced in the early 60's and is the forerunner of the A7 design, like mine, that were designed with smaller venue's of up to about 800-patron's in mind. The A8 were designed for even smaller theaters, of the 80's and beyond which had little room behind the screen.

None of these cabinets were designed for sub bass in mind, the have just regular bass "woofer's".

The A7 cabinet next to my sub, will only play down to around 47-Hz. at its -3 dB point, but it will easily play lower than that to produce the notes of a stand up bass or a bass guitar (the open low "E" string of a standard 4-string electric bass is just over 41-cycles at its fundamental frequency).

Now on to home subs...

The smaller the sub and the smaller of the cabinet, the more power and speaker excursion is required. Compared to to a large cabinet with a horn loaded (coupled) cabinet.

Remember to differentiate the term "woofer" which is a bass speaker, from the term sub-woofer, which is intended for sub bass.

Simply put, there is no magical perfect size for a woofer or sub-woofer to be.

How deep the driver plays is dependent on the design characteristics of the driver. Is it intended to be used as a bass driver or as a sub-woofer, that makes a difference?

Secondly, the lower frequency of the bass and the amount of bass produces is largely a product of the size of the cabinet, not the driver, which does play an important roll, and the power of the amplifier driving it.

I use a small 8" 75-Watt Martin Logan sub in a bedroom, with bookshelf speakers that play down to 50-Hz. at their -3 dB point. This helps fill in the sound below 50-Hz. and you are not really aware that thee is a small sub present in the room.

For most listening rooms, a subs with a 10" or 12" driver is sufficient. It still falls back on the driver design, cabinet design and the power of the amplifier.

Larger driver's would be naturally require a larger cabinet. Which together would help to develop a deeper base than a slightly smaller 10" driver.

Still the larger the room and the more SPL is required to pressurize that room will require more or larger driver's, together with more amplifier power.

I'm not sure that the "spider" and speaker "surround's" have that much influence on the overall performance of a driver.

Your friend's statement "He insisted that larger woofers can never have a better bass response due to cone size as well", make no sense at all.

All things being equal, the larger something is, the deeper base that it could naturally produce. Compare a 1" gong to a 12" gong to a 6' gong, What is going to produce more and lower bass frequencies?

If this were to be the case, then speaker manufacturer's would not be producing large 15" and 18" speakers and large speaker cabinets.

Here are a couple of compact pro-sound Yorkville commercial bass cabinets of the same basic design.

Here is their smaller 16" cabinet, which weighs 110-lbs.



Here is their larger 18" cabinet, which weighs about 182-lbs.



My Yorkville UCS-1 is a 15" cabinet which weighs 155-lbs, which is kind of in the middle between both of these designs.

The UCS-1 is rated at 1,500-Watts and the 18" cabinet (above) is rated at 2,000-Watts.

Size wise, for comparison's. The UCS-1 is 41" tall, the 15" ES15P is 32" tall and the 18" LS1208 is 43.5" tall.

Do you have any specific questions in mind?

 

The Pros and Cons of Big Subwoofer Drivers

What Size Subwoofer Do I Need? | Driven Sound and Security | Michigan

 

15" Powered Subbie - This big boy weighs in at 85kgs...
For ROCK I use it at its lowest settings (or a bit higher with the 'main spkrs' LOW turned down) .. It gives 'ambience' and
'presence' to 'weaker sounding' Classical music recordings. Having it facing across the room gives it a bit more subtlety as it
isn't 'in my face'.

 

I like it!

 

I like 15" subs. Like stated pushes a lot of air at low distortion due to minimal cone movement vs 10" sub or 2.25 times as much air.

 

I had a REL sub that would reproduce 16Hz. The very lowest organ notes! And with a 10" speaker. Achieved with cabinet and amplifier design.

 

I'm not into car audio. Home audio is what I'm into currently. I do own a couple pairs of smaller studio monitor speakers. I use those for my Computer/media room. What really drove my posting was the fact that none of what he said sounded very right to me. I've set up numerous systems in three homes so far with great success. The bass always sounded great. I once had to deal with a small room 8'x8'x8'. The subwoofer I used there was overkill as I didnt have much choice or money at the time. I believe it was either a 12" or 15" JBL or Yamaha. I have since sold most of my speakers. I am really happy with the bass response of my old Realistic Optimus 400s.
@SandAndGlass I sent my buddy a mms of what you posted here. I also sent him the link to the page. Thanks for all of the information. It definitely clears things up for me.

 

This one........

 

Just my opinion, but in most homes, smaller Subs are preferred, if the intention is just to augment the mains and help them get a little bit lower and firm up the lower bass. Most people don't even need 12" subs. A couple of 10" subs are better, as they even out the bass in the room.

I have processor based system so that I can use my normal stereo amplification for HT and stereo. So the large sub can make the earth slitting open on the screen and make it seem like the floor is spitting open along with it.

Now since I run my commercial sub, for both HT and stereo (which I can turn and off). I run a full range signal from the preamp to an unused channel of the processor that I select on the remote, when playing music. I am using the processor's bass management feature to separate out the sub-bass signal from 40-Hz. and below and send out the processor's LFE channel. That way I can use the commercial sub the same way for either HT or stereo.

I have two pair of front mains, and can use either pair or both. The inside pair are the Polk flagship LSiM707's. They weigh 99-lbs. each and play down to 38-Hz. at their -3 dB point, their lower limit is 20-Hz. For practical reasons, these are about as large an most anyone is going to have in their living rooms.



These can produce some deep base. The large A7's, one is sitting next to the UCS-1 sub, only play down to about 47-Hz. as their -3 dB point, but they will play much lower.

Even with big speakers like these, if you listen to music like Trance or Dubstep there is going to be a lot of big deep bass. People think they are hearing this bass. I have people over and play music like this for people, and then I turn the commercial sub, which is powered by a Crown class "D" amplifer. It runs in bridged mono mode and can produce 1,600 watts. The sub is very efficient, about 100-dB's due to its horn load design and large cabinet.

It can play at a SPL of 133 dB, continuous program material. So even with very large speakers, if you listen to certain type of music, you need a lot of power and a large sub to really hit that deep base. Check some of the JL subs, they have some of the most serious home subs going!

The biggest mistakes that people make with home subs, are buying to large of a sub, for the size of their room and turning the volume on it up too loud and the crossovers set too high and what you end up with is a mess!

You used the resources that you had available to you at the time, you could see first hand what happens with a large sub in a really small room. But, you did the bet that you could, no shame in that.

But consider that most average rooms are really not that big, are square or rectangular and are easily overpowered by even most 12" subs. The most important thing at home it the proper integration of a sub into the mains.

It's all good...

 

I think your friend is mis informed. Any driver can exceed it's xmax , no matter the diameter.

Smaller the sub driver the further the cone has to move for a given output. 10" sub that goes low is inefficient by law and is limited in output considerably compared to a similarly designed 15.

Lots of factors involved in sub design including size of driver and while nothing wrong with 10 inch I wouldn't choose that size for most applications.

 

I have one sub that has 3- 8" woofers, Martin Logan Depth, and another that has 1 - 10" woofer, Martin Logan Grotto. Acting together and set up as they are they go low or lower than 95% of most records and CDs and my room is fairly large and extends into the kitchen/great room area. Plenty o' bass throughout the house.

 

See Green Mountain's explanation under the Ask The Right Questions section. Much of the problem comes from the speed of sound being faster than the speed of the cone. The more the cone moves the more it will be distorted because the cone is moving slower than the speed of sound. Therefore, bigger can be better because it requires less movement of the cone.

I didn't feel like digging through his website anymore this morning but I remember reading one of his discussions where he calculated that on smaller high excursion cones trying to make bass at volume the initial wave release often hits the listener while the cone is still trying to produce the note, smearing the wave. This is the calculation of the differences between the speed of sound and the speed of the cone and that speed over the distance to the listener's position.

That said, I went with a 15" sealed running at an idle, and with an electric feedback sytem to control boom. As a bonus, it doesn't require a ton of power.

 

I use Sunfire EQ 10 that is wonderful but when I think of the next upgrade in the bass dept. I think of the Swarm system which I see made the Absolute Sounds recommendations again this year even though they are rarely mentioned in forums and mags. Check out the reviews. 3 grand with amp I think.

 

I don't think the swarm system is mentioned for two main reasons.
A lot of audiophiles don't know how to properly integrate a sub. As a result, the sub doesn't sounds right to many so they write it off as something for HT.
Secondly, cost. A swarm of subs is expensive just to eek out the bottom harmonics. Opportunity costs usually allocate money to be spent elsewhere, main speakers, amps/pre, music, a vacation......

I get a similarly claimed flat response at the listener position from 20hz to 80hz using one large sub and a similarly large home made bass trap to control the ringing of the room, at a third of the price. I don't really care if the sound isn't equally flat in a different position in the room where no one will be while music or movies are playing. If you do care about the sound all over the room, a swarm might be the answer.

 

Does the shape matter? I have a SVS cone shaped and Carver true signature square one which is box shaped..

 

My bookshelf speakers have 6.5" woofers which will deliver down to about 78Hz. I augment those with a 100 watt 8" low profile sub, crossed over at about 80Hz. No problems with that setup so far.

 

12" drivers are fine.

 

Much depends on the size of the cabinet.

 

People get mislead by the widespread notion that 10¨ subs produce the ¨punchiest¨ bass and more is overkill, unless you have a very large room. In a way, they are right, because they excel at the higher bass frequencies (around 100 hz), hence the ¨punch¨. But 12¨ will provide just as much punch AND a WAY more extension (lower frequencies), esp. when paired with capable floorstanders.

8¨ subs are a joke and 15-18 and 21¨ tend to be sloppier and have a lot of associated issues; WAY better, tighter results with dual 12¨.

 

Had a chance to hear that Infinity system. Maybe I was amazed.