18 inch subwoofer vs multiple 12 inch subwoofers with bookshelf speakers

Unless you can’t afford it, multiple subs are always better than one, especially when dealing with bookshelf speakers. This is a no brainer. Also, you might get away with it for movies, but two F18 might be overwhelming for your bookshelf if musicality is your criteria. 

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Two subs is better than one, and four are better than two as long as the subs are somewhat comparable as are the F12 and F18.  Of your options and if it’s viable I’d put a swarm of 4 F12s at the top of the list.  Best of luck.

4 X f12.  I have two Rythmik F30 (2 X 15") and two SVS SB13 Ultra subs (13.5") in my system.  It's complete overkill.  The volume setting on the Rythmiks is about 9 o'clock and something like -27 on the SVS subs.  In other words, they are barely even on for proper integration.  The F18s would be overkill unless you have a really large room, or would rather hear bass than the rest of the frequency range.

I am a sub system user for 20 years now and have tried a number of things. One subs is very poor sounding. It “can” work for one seat but two subs is so much easier to integrate.

if you want infrasonics (bass below 20hz) the 18s will be much better than 12s. But almost all music is filter at 20hz. For movie and music 12s are 100% fine.

as for integrating with small 5.5” drivers… it will sound fine with either size until your speakers run out of steam at which point the subs will take over the sound signature. Just come down to how loud you listen. I would guess at 95db your speakers are starting to compress a bit. There is a reason theaters use compression drivers and or line arrays. 
 

another way to look at it is which sub plays at a higher crossover. Low inductance light drivers can play very high and a crossover higher than standard might actually help you out. Sadly I fine anything over 80hz is pretty locatable though so sub placement would need to by right by your mains for higher crossovers. 

Based on the linked measurements the LS50 takes a big dive by 96db in the bass. If you want to play above 90db-ish you probably need a crossover of 100hz and a safer bet would be 120hz if you really wanted to rock out a movie. So maybe the question is what sub plays the best in the 100hz range. Food for thought. 
 

https://www.erinsaudiocorner.com/loudspeakers/kef_ls50_meta/

In your case, if you can place each in an ideal location then do two.

I don’t believe that smaller = faster, at all. That’s a misunderstanding of what really happens, however if you are flexible in the sub placement so you can smooth out the room response, two will give you the better option.

Also, consider bass traps in the corners and a miniDSP to equalize each sub separately, and plug the ports. Set the subwoofer as high as your measurements say you can.

The miniDSP site had application notes for EQ'ing multiple subs in a room.

Check out the AM Acoustics Room Mode Simulator, it will help you place your speakers and subs outside of the worst and lowest room modes.

Of course, another problem often faces is that a reflective room with all parallel surfaces will be bright. Treat it as needed first, that will help the bass bloom. Then you can set your subwoofer level correctly. Don’t forget the ceiling between listener and speaker.

Bass becomes directional due to it’s overtones, thus bass imaging is possible

A stereo pair of subs, adjacent to the fronts, no port, if so, front port only.

One thing I forgot to mention, specs and measurements like the one's shown above don't mean crap when you get a speaker in a room.  This speaker seems to have plenty of output to 40 Hz, which is great for the size, but in the room this could go either direction.

I would proceed in this order:

• Place your main speakers
• Treat the walls and ceiling
• Evaluate

Treating the walls and ceiling will often bring out the bass to the point you don't want more.  THEN if you still want more, the dual subs, placed in ideal situations with EQ and bass traps may be your next steps.

Here is the articles from miniDSP

After thorough research, I have narrowed down my options to two configurations: 1x Rythmik F18 18-inch subwoofer or 2x Rythmik F12 12-inch subwoofers, with the possibility of expanding to two F18 or four F12s in the future.

My primary criteria for the subwoofer system are musicality, speed, transient response and depth of bass response, particularly in the low-frequency extension below 18Hz

For your criteria, you won’t do any better than Rythmik subs (there is no competition). Get two F18s now. Later on, add two F12s as funds permit. I would also recommend the F12G w/ the GR research driver over the F12.

Depending on the processor you have and room layout, you can load up different combinations of subs for the content you are listening to. You could also go all out with 4 of them. The F18 can be mind blowing (!!), f you take the time to integrate it correctly. I was raving about it relatively recently in some other thread. Dr. Brian Ding at Rythmik is very helpful and should be able to answer any questions for ya,

I would also recommend the F12G w/ the GR research driver over the F12.

+1 since music is your priority.

I know the brand Rythmik but have never used them in my system. In general, smaller drivers, 12 inch in your case vs. 18 inch, will deliver faster bass which can keep up with your song.  Larger drivers, in general tend to be slow and likely suitable for movies in home theater set up.  Dual subwoofers are also better than one subwoofer.

Fast bass, slow bass - myth vs. Fact see here! I agree with @james633 😎

Mike

@thxbest. 3x KEF LS50 Metas with 5.25-inch midrange drivers, 2x KEF Q150

Correct me if I’m wrong, your Musuc/HT system isn’t design for more than 4-6 people in a medium size room. These speakers will have a hard time with anything larger anyway.

Here in Las Vegas, I see how they setup 2k+ seat show rooms. They use horn loaded speakers above 60-70Hz hidden above the stage and place a 12”-15” subs hidden behind/below every 2 to 4 seats. The sound tech will go into sections across the show room and EQ/balance each zone against main speakers. One more device they use is multiple delay lines to sync the whole room. Yes this is an oversimplification but you get the idea.

I’m a humble advocate of placing subs behind your listening seats. Using digital delays to retire bass signal to sync arrival times gives me perfect base every time.

Best Regards 

Mosler666

PS: I choke every time when I see someone say bass overtone with subwoofers. Proper sub at proper xover feq will not produce any such nonsense.

I too generally have preferred multiple subs, especially when crossing to small (bookshelf type) mains.

Driver Xmax and surface area will not be the same. Depending on how you plan to integrate the subs, that may not be a negligible difference. An 18” driver will offer ~10-12% greater surface area than 2x 12” drivers.

In your case, without knowing the specs for either model, I’d still be inclined to use two smaller subs vs. one bigger sub (again, especially with small mains and with music being a strong use case).

I have been using two B&W AWS600 Series 8” subs paired with Harbeth SHL5+ Bookshelf monitors and found them more than adequate. 200W x2 offers more than enough power without overfilling the room with a super boom boom bass punch that can move your furniture. In short, too much can be way worse than not enough. The size of the area you need to support coupled with the crossover frequency and how hard you can drive the monitors is what drives the formula, not just the bottom end.

Not to 'X' foils with Erik, but...imho 'smaller' is faster, but I've played about with trying to pace with the large Heil AMTs'...but I goof about with various combinations to fill the hours.

Currently, the low-mids X out from a pair of 6.5s' into a pair of 10s' for most of their range.  The 'bottom' Xs' down to an 8" self powered sub...

An odd coupling, perhaps...but my space 'x v. y' is similar to our OPs'....except for ceiling 'z', which is 13~14 ft.  And there's other issues that drive me to 'ignore the room' per Linkwitz...

(...still trying to convince our cats to act as bass traps, but they ain't buying it...messes with their sleep patterns....🤷‍♂️🤦‍♂️...)

I've got 2 - 18s', a 12 that's better suited to a 'street boomer', a pair of JBL 10s' that could be pressing into service.... But, have 4 - 8" that I'm considering for a 'swarm' arrangement for my walsh drivers....*s*

Got the means and the methodology    just have to give up that annoyance called 'sleep'....😏👍

Another vote for multiple 12 inch subs. We have 4 REL S510s in our home theatre and it is fantastic 

@thxbest 

There is a video on Youtube that is titled: "Dual Rythmik FM-8 Subwoofers as Speaker Stands?" that is probably worth a look.

There are definitely times when smaller is less likely to wake the dragons, so I'm not saying smaller isn't often just right, but sometimes excess really is excess.

A pair of REL subs will provide the upgrade sound that you are hoping to achieve.

Depending on the nature and and musical venue you prefer to listen to, I would not think it would be necessary to go beyond the "T9/x" sub. A pair should yield improvements to you overall system that other brands can only aspire to. Of

course REL has several other sub lines that have won virtually every audio award the industry has to offer. If you have the funds, you might explore that course.

I can assure you that a pair of "T9/x subs will rock your world, and at the same time, provide the finesse that classical and jazz music require.

AXPERT

I used to have 1 REL sub, tried 2 Rythmiks F12 and preferred the latter, then added 2 additional F12 for a nice improvement, then added a miniDSP 4x10HD and Multi Sub Optimizer (MSO) for an even better result. Very much in line with above posts.

Multiple subs.allow for smoother frequency response across morecseats in the room. MSO enables a flat response across several seats. It does require a measuring mic, though.

One suggestion is to consider two Rythmik F8 under/very close to your LS50. F8 can be crossed much higher (up to 250Hz but you don't need that much). You could run F8 say 20 to 150Hz and two F12 from 20 to 60Hz.

I had my Rythmiks for about 12 years without issues. And the same folks keep replying my questions at Rythmik, which is nice.

ditusa,

The article by Doug Blackburn is absolutely correct. The "speed" heard is not from the bass. It is from the accurate reproduction of midrange and HF overtones of the bass fundamental. Smaller bass drivers extend up to the mid bass and significantly into the midrange. Most critical is the integration of the midrange and bass drivers. Larger bass drivers are good for only one thing--deep bass extension.

viber6,

So let's say a 12 inch sub for instance Rythmik F12 does perform and blend better with KEF LS 50 Metas than an Rythmik F18 sub because of the better mid bass, no matter if servo controlled or not?  

I would buy two puppies instead of one

thx best,

I don't know the Rythmik products.  Servo controlled is another factor.  Theoretically, according to Doug Blackburn, I would predict a servo 12" would still integrate better than a servo 18".  But it would be an apple/orange comparison when comparing a non servo 12 with a servo 18.  

As an aside, in 1980 I heard the HQD system--double Quad 57's, Decca ribbon tweeter, 24" Hartley woofer built into the floor whose cabinet was the room below.  The Hartley was probably not servo.  Those Quad electrostatic are still unmatched for midrange accuracy, and probably for upper bass accuracy.  I don't listen to music with much deep bass, so I couldn't comment on the quality of the bass from the Hartley.  Mark Levinson, who put together the HQD, drove it with triamped Levinson ML2 power amps and used crossovers to keep the midrange overtones from the H out of the Quad midrange.  

18” subs are a bad idea. Their motion can frequently leave pistonic and begin to wobble. The largest I recommend is 15”, but then you are dealing with large enclosures. 12” is a great compromise. If you want more than two 12” subs can give you, get another two. I use 8 12” drivers.

18” subs are a bad idea.

@mijostyn Yes, except when it is sealed and has the servo controlled drivers deployed by Rythmik (it becomes doable). Yes, it is a tad bit of a compromise compared to their 12 inch offerings, etc, but, it could put you into the infrasonic miracle territory. OP’s use case is both movies and music.

@thxbest , You could also go with Model G22, which is a force balanced, dual opposed 12 inch configuration.

While this is not answering the posed question, I find it interesting that so many are using crossover points above 100Hz, even up to 120Hz. Ive found that 80-85Hz keeps the vocals out of the subs, and it becomes less "directional". I've always used a single.

@thxbest , I would ask Brian at Rythmik.  He was very helpful to me not just with his product line, but also other principles and how to meet my integration and sound quality goals.  He is very straightforward and not trying to just sell you something.   Certain theories may hold true across various designs and manufacturers,  but why not go right to the source when they are so knowledgeable and available!   As much as I love my KEFs, this is what is so great about dealing with a company like Rythmik getting to interact with the designer and owner. 

 I bought dual F12s through Salk.  They seemed like the best combination of depth,  musicality, and authority for my tastes.  A single F12 is pretty loud by the way.  I haven't heard RELs, but these integrate better than any other subs I've had including with my very fast very musical Daedalus speakers.  I'm not sure about your conclusion on " better" mid-bass on the F12.  Seems like your priority is fast musical response where others may prefer the slam the 18 can provide.   The sheer physical size and weight of the 18 drove me away.  I would have went with the compact 15 if I had more priority on slam than speed.  Don't know what frequency you're considering midbass, but I would be surprised if you received a suggestion to use them (12 or 18) to solve many problems above 80-100 Hz.

Below from Brian:

"FM8 will sound more fluid than 12”, but that means its tactile response is also worse. There are customers who prefer FM8 over F12G. It all depends on the priority. FM8 bass quality is closer to electrostatic panel speakers. Another thing to consider when you crossover too high is the location of sub relative to the main speakers. When crossover higher you have to place sub next to main speakers to get proper dispersion lobes and phase alignment.

Our F12 is our reference frequency response for all of our design. F18 may extend a bit lower, but it will be 2hz or3hz at most. If you like fluidity type of bass, F12 is best and E15/F15 is next and F18 is last. Large diameter drivers do sound more authority in bass, but some may interpret that as boomy."

@deep_333 , Multiple 12 and a little DSp will do exactly the same thing with less distortion.

18" sub. That when I go out to the club.  I'm a little too old for that.