SVS SB12 Plus or BK Monolith?

[Rob100]

After some advise please as I need a new sub.

Room is dedicated HC room 12' x 9'6" with sofa on back wall and screen on front wall.

Regardless of which sub I go for, it will have to sit at the front under the screen.

I could accommodate the size of the Monolith. I would probably got for the Monolith DF rather than the FF.

Currently I'm using a Denon 3805 receiver. Front speakers are AE309's and centre is an AE307. I will upgrade the fronts and centre at some point and then eventually the receiver, but have spent for too much recently so one step at a time.

Main use is movies, very rare I listed to music in this room.

I have my speakers calibrated at 75db (0db on Denon) and typically I watch movies with the volume somewhere between -15db and -5db on the Denon.

Help me decide please

Thanks,


Rob.

[Richard Torble]

I've not heard the BK, but I have heard the SVS. It was nothing short of stunning and will hopefully be getting one myself as soon as possible

I have no idea how they manage to get a sub that good in a box that size.

[chrisgeary]

I'd go for the larger sub if you have the room for it. The SB12 is amazing for its size but there is no substitute for physical volume.

[Rob100]

Thanks for the replies.

Chris - Have you heard or even owned both?

[russ.will]

Either of those subs will fill a room that size, comfortably, at the levels you're listening at. The bigger box will go deeper, no question.

My only concern would be, with the sub sitting against the front wall and you against the rear, the boundary gain experienced will be mahoosive. The first time a cannon goes off in Master & Commander, should see you clean out of the chair.

The other problem I note is that if your room is 9ft wide, I'll assume the usual 8ft(ish) ceiling height, then you'll potentially have a monster pair of combining room modes at 45-55Hz. These will dominate the sound of the sub, masking the lower frequency output.

The SB-12 has a raft of very handy room compensation controls which will help it integrate with your room and ameliorate the peaks to a certain degree, but for the money you could get a Monolith and a BFD which is a far more flexible room tuning device.

Both subs would benefit from a BFDs use, but as the rooom is dedicated, I assume you have a bit more positioning flexibility. To my mind, this plays into the hands of the Monolith, but I really would expect you to get a BFD to hear it at anything like it's potential.

The SB-12 has a more plug and play appeal, but is ultimately a smaller sub and you'd be amazed at the difference those last 5-10Hz can make with the bigger sub.

Russell

[Rob100]

Russell,

Very helpful if not confusing post

Up to now my main focus (and knowledge) has always been on PQ, so seems like I have a lot to learn on the audio side of things.

Ceiling height is approx 7' 6". Not quite sure what you mean by "you'll potentially have a monster pair of combining room modes at 45-55Hz. These will dominate the sound of the sub, masking the lower frequency output." If you could elaborate I would be very grateful.

Are you saying that a BFD will enable me to overcome the problem described above?

Despite being a dedicated room I don't have loads of flexibility in positioning. It's pretty much either on the front wall between the front speakers - to one side of the centre, unless the centre could sit on top or is this a terrible idea? Alternatively next to the sofa which you advised in the Monolith thread was a bad idea as the bass would be too localised.

Thanks,


Rob.

[Rob100]

Just thought of somewhere else the sub could sit....

Bang, smack in the middle of the room - or is that a stupid idea?

[chrisgeary]

I have owned the SB12+ amongst other subs, but not heard or owned the Monolith.

[Nimby]

Originally Posted by Rob100

Just thought of somewhere else the sub could sit....

Bang, smack in the middle of the room - or is that a stupid idea?

The middle of the room is supposed to be a null point.
The sub would be working into an acoustic back hole.
It would be an interesting experiment to see if this is true in the real world.
Unfortunately I don't have a suitable room to try it out.

[Nimby]

Originally Posted by Rob100

Russell,

Ceiling height is approx 7' 6". Not quite sure what you mean by "you'll potentially have a monster pair of combining room modes at 45-55Hz. These will dominate the sound of the sub, masking the lower frequency output." If you could elaborate I would be very grateful. Rob.

Bung your room measurements in here for an idea of likely room modes.

http://www.mcsquared.com/modecalc.htm

[russ.will]

Originally Posted by Rob100

Ceiling height is approx 7' 6". Not quite sure what you mean by "you'll potentially have a monster pair of combining room modes at 45-55Hz. These will dominate the sound of the sub, masking the lower frequency output." If you could elaborate I would be very grateful.

Are you saying that a BFD will enable me to overcome the problem described above?

Subwoofers are cable of exciting the rooms natural resonances. These are directly related to the room dimensions as the standing waves (room booms) are only present at the frequencies with wavelengths related to the rooms dimensions.

Measure your room and plug the measurements into this. This will indicate the frequencies most likely to 'boom' in your room.

When I saw that you had a 9ft room width, I realised that it was close to the probable floor to ceiling dimension, circa 8ft. This will likely result in two booms (more correctly, modes) that will cause peaks in your subs response. That they are so close together means that they will combine, to a certain degree and cause a massive boost at across those frequencies.

Even with your current setup, if you wander around the room, you'll note that bass is massively louder the closer you get to a wall. Try it. If you get a quality sub, position it against the front wall and then sit against the rear, believe me you'll suffer some astonishing bass, especially at the frequencies the rooms dimensions favour. The gain in the subs frequencies affected by the rooms dimensions are at their most extreme at the room's boundaries and that's wher you're going to sit AND position the sub.

The fact is, your hearing reduces in sensitivity with reducing frequency. Therefore, if you have a really dominant frequency in the room(which you will with the current arrangement), it will tend to overpower lower frequencies. In other words, you'll reduce the volume of the sub so it doesn't sound overblown, but in so doing, you'll be turning down the frequencies you bought the big sub for in the first place.

Buying a BFD/SMS-1 allows you to tune out the dominant peaks in the subs in room response. In your case, this is even more critical because of the sub/seating positions. Once these peaks are gone, you'll find that you turn the sub up to actually hear all of the subs output on an even footing, et voila! Your deep response becomes noticable.

Along the way, you'll note that the sub sounds tighter, cleaner and faster. It involves some effort, but unlike the main speakers, it's easily measurable with any number of freely available on-line resources, which simplifies the process. Doesn't make it any less adictive though.

Russell

[Rob100]

Russell,

Thanks for the info.

I d/l'ed Room EQ Wizard and after some initial problems with crappy sound cards I settled on using my old (and trusty) Turtle Beach Santa Cruz.

Oooh... Took a little while getting my head round the software, but using my RS SPL meter I measured my current sub and I cannot believe how pathetic it is compared with the graph for the SB12 on SVS's website. Have you post a graph of your Monolith anywhere?

I've also been looking at FBD's and am starting to get the idea

Thanks again,

Rob.

[russ.will]

Having searched my Imageshack images, I realised that any recent plots I had were lost when I migarated my Mac G4 over to my MacBook Pro dual core. I'll blame my ham fistedness rather than the Macs for that one.

However, this gives me a reason to get the E-300 out and record some more recent ones. It should be noted that as I use an SMS-1 they're not REW style graphs and therefore the general shape of them is more important than the absolute levels.

The last one I could find, which is hanging out in some ancient thread, is this one:

IIRC, this is a sub only plot, but more recent positioning experimentation has resulted in far less savage filters (with no boosts) and a more even in room response for the immediately adjacent listening positions, especially once I employ Audyssey.

FWIW, this is what it looks like with no EQ:

Note how the 27 & 35Hz peaks combine to give a large, apparently single peak. Without EQ, they mask the 20Hz odd effects that make a big sub sound special. I'll post a much more recent graph (these are nearly a year old) as soon as I can, which show the main speakers included.

Russell

[Rob100]

Thanks Russell. All very interesting.

The one thing I am confident about now is that which ever sub I get I now know how to measure it's response and understand what I'm seeing.

It certainly will be very interesting to see what difference positioning makes.

Another question.... I have my RS SPL meter on a tripod to it's at ear height of my listening/viewing position. Should I point the mic towards the front (so meter is on the top) or point the mic to the ceiling?

Thanks again,

Rob.

[russ.will]

Ceiling.

Russell