Replacing my 2 sealed 18s with 4 X dual 12s??

Hi guys.

I currently have 2 X 18" inch BMS 18n862 sealed subs in opposite corners of the room powered by a inuke 6000dsp

These are big and look like **** to be fair. But they are musical and have enough xmax for home theatre too

I'm 50 50 music movies and have access to Dirac live

Thinking of building 4 dual 12inch subs (1 in each corner) so that's technically 8 sub drivers. They will be taller but much shallower and not as wide obviously.

They will look better and also be in all 4 corners and have more cone area.


What drivers are comparable to what I have now? Good for music and movies.?

Will the output be good enough. I know more cone area but 18 inch to 12inch? Just makes me think about output under 20hz for movies.

I have kef LS50 for mains and issue is there midbass is lacking so having subs comfortable playing a bit higher up with quality is important. But I will eventually replace these.

Cheers
 

GM

Member
Joined 2003
Greets!

FWIW, ideally need (5) 12" just to get enough effective piston area (Sd), otherwise will need more Xmax, power handling to keep up with the 18s. Either way, spaced out to be at least 70+% of room height creates a ~infinite corner array. FWIW, one in each corner never worked for me unless spaced up at different heights at the room's odd harmonics and limited to 120 Hz/2nd or higher order.

Sorry, haven't kept up with drivers since the mid 90s and only used premium prosound made in the USA.
 
Sorry if I've confused it but there will be 2 drivers per box so 8 subs in total. Vs my current 2. So cone area should be alot higher than I have now.

And because one is on top of the other I should get a bit of advantage of adding a bit of height.

But 8 have no clue on quality drivers when it comes to 12 inch in a relatively small box. Or should I say 2 X 12 8nch in a small box

Also will need a 4 channel amp but will cross that bridge when I come to it
 
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GM

Member
Joined 2003
No, you wrote it right, my eyes apparently kind of glazed over (another sleepless night :sigh:) as I quickly scanned the post.

That said, did you make sure that the summed (8) 12" swept piston area (Sd*Xmax) is sufficient?

In just 'blindly'/assuming picking a BMS 12N804 as ~ in the same 'league' performance/quality wise, it has a 531*0.8 = 424.8 cm^3 x 8 = 3398.4 cm^3 while the 18N862 = 1219*1.8 = 2316.1 cm^3 x 2 = 4632.2 cm^3, so ideally need 11, which of course for a balanced system with a bit more dynamic headroom boosts it to (4)/corner. :headbash::cuss:

There's 12" with a lot more Xmax, so can probably use just (8), but no clue if the performance/quality will satisfy. For sure the few I've been exposed to aren't, but they were relatively cheap in the USA and no longer available.
 
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That's very helpful thanks.

Looks like the BMS 12 inch has less than half the xmax of 18. Which is what's causing this issue.

Obviously I've got another 2 corners filled so room response and more room gain etc could balance it out. It's not like I've ever really pushed the 18s to their limit either.

But finding a more all-round woofer which extends lower with a bit more xmax and is still good for music would be ideal.

I like the sensitivity of the pro drivers too. Not too much power required
 
The problem is in the UK there is not much choice for decent 'hi-fi' subwoofer drivers.
I'm running 4x Eminence Lab 12's in a pair of sealed enclosures which do ok for my room.
Some of the Rockford Fosgate car audio subs look ok, as do some Alpine drivers. There's the Fab12 from BKelectronics that looks like a clone of the Lab12.
Peerless xls drivers are available over here too, but I don't recall them having big xmax.
That leaves pro drivers, most of which seem to be more suited to a low freq corner of around 35-40Hz.

Rob.
 
The four ohm LAB12C has the same 13mm excursion as the six ohm LAB12.
8 LAB12C drivers would be a fair increase in displacement and a lower Fs than the pair BMS 18n862.
Each cabinet could be wired in series for a nominal 8 ohm load, two cabinets per side would load your NU6000 at four ohms, at 1500 watts (peak) each cabinet should reach around 110dB at 20 Hz with no room/corner gain.
Each 2x12" cabinet could do a clean 120dB in the 100 Hz range.
Considering the KEF LS50 max out at 106dB above 80Hz, should be more than enough.

From experience, I'd expect the 12" cones at 13mm excursion may sound better in the midbass than the 18"at 19mm.

Art
 
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My actual biggest worry was that I originally went with the BMS pro drivers due to their apparent superiority in quality Vs (proper subwoofers) like the Dayton ultimax or any other high excursion drivers.

I had in my head that they require less wattage to get a required volume, and have a lighter mass so seem faster, punchier for music etc etc.

But they won't go low. Hence 18" to counter that.

But I'm really wanting more but smaller cabinets and I didn't want to sacrifice music quality. Maybe I'm reading in to it too much but the amount of EQ I have to apply to get the BMS flat to 20hz with a house curve is LOTS.

It would be nice to have woofers that naturally go lower, but still have the quality for music

As for amplification I would want each cabinet to have its own channel. (For Dirac) so the Inuke will have to go I'm afraid
 
The smaller the box, the higher the rolloff slope begins.
There is nothing wrong with applying corrective EQ to a sealed box, the low end output is determined completely by displacement.

The BMS18N62 increases about 13dB between 20 and 100Hz in a 180liter box, 15dB in a 115liter box, and 19dB in a 180liter box.
180Liter.png

115L: 57L.png


A higher Bl, lighter cone is more sensitive/efficient in the upper end, but in a sealed cabinet the low end efficiency of the woofer is proportional to the cabinet volume and the cube of its cutoff frequency.
Smaller boxes, regardless of how the Sd is made up (single large driver, multiple small drivers) require more power to produce the same displacement/SPL.

Four LAB12C require double the cabinet volume for the nearly the same slope as the BMS18N62, you would be better off getting another pair of them and putting all of them in smaller cabinets.
Cut the size in half, they will use about double the power in the low end for the same output, but you can drop the cabinet volume to 57L and still be around 2000 watts per driver at 19mm at 10 Hz.

Since you plan on corner placement, you could make triangular cabinets and really cut the footprint down.

Have fun!

Art
 
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That's very helpful thanks.

Looks like the BMS 12 inch has less than half the xmax of 18. Which is what's causing this issue.

Obviously I've got another 2 corners filled so room response and more room gain etc could balance it out. It's not like I've ever really pushed the 18s to their limit either.

But finding a more all-round woofer which extends lower with a bit more xmax and is still good for music would be ideal.

I like the sensitivity of the pro drivers too. Not too much power required
You're welcome!

Indeed!

True, but don't know just how life-like you want your T-Rex foot stomps or WWII TNT bomb blasts (infrasonic horns are super large, so imagine how many woofers/Xmax it would take to replicate them).

Also, assuming a 120 Hz HT max XO, then only need a Qts' for this upper mass corner (Fhm = 2x Fs/120), which in turn removes some of the need for a high SQ (sub) woofer and especially if only using the cinema standard 80 Hz, though with lower efficiency as the trade-off, which brings it back to my preferred corner line arrays which allows cheaper drivers. ;)

(Qts'): (Qts) + any added series resistance (Rs): http://www.mh-audio.nl/Calculators/newqts.html
 
The smaller the box, the higher the rolloff slope begins.
There is nothing wrong with applying corrective EQ to a sealed box, the low end output is determined completely by displacement.

The BMS18N62 increases about 13dB between 20 and 100Hz in a 180liter box, 15dB in a 115liter box, and 19dB in a 180liter box.
View attachment 1215439
View attachment 1215440

A higher Bl, lighter cone is more sensitive/efficient in the upper end, but in a sealed cabinet the low end efficiency of the woofer is proportional to the cabinet volume and the cube of its cutoff frequency.
Smaller boxes, regardless of how the Sd is made up (single large driver, multiple small drivers) require more power to produce the same displacement/SPL.

Four LAB12C require double the cabinet volume for the nearly the same slope as the BMS18N62, you would be better off getting another pair of them and putting all of them in smaller cabinets.
Cut the size in half, they will use about double the power in the low end for the same output, but you can drop the cabinet volume to 57L and still be around 2000 watts per driver at 19mm at 10 Hz.

Since you plan on corner placement, you could make triangular cabinets and really cut the footprint down.

Have fun!

Art
Really funny as I've been modeling too and it seems that getting another 2 BMS is probably the way to go. And build them in to the corners.

Make them a bit smaller cabs and stuff them with fibre glass to replicate a bit larger box.

Also. Won't need as much bracing if they are built in to a corner as the structure of the box is more rigid I believe but could be wrong.

I assume the box would also be kind of coupled to the wall so won't stick out in to room as much? Never done this kind of design before
 
Yeah, don't need much bracing if using a high MOE stiffness such as 18/19 mm BB, apple or marine ply. Biggest problem is getting them heavy enough, yet manageable, so might need something removable perched on top, such as my preferred heavy plants that did double duty diffusing the corner's higher frequencies.

Right, my long gone corner horn system was 56" wide, but only 28" deep and if I'd used a higher ratio it would of course been less.
 
If you want high efficiency live sound drivers.
Then no 12" speakers not even considered a sub.

Far as using more speakers for efficiency.
There is plenty of subs in 12" range that will
do it.

Far as sealed, again with drawback of efficiency
there is numerous well known HiFi subs
that can go deep sealed.

2x 12" are fine for some 8x would do it.
Be curious what the actual listening SPL is
and actual real power level is. Not theoretical
overkill

If performance issue is not the issue.
" Ugly boxes" are fixed with a rebuild
and finish techniques. Or hidden behind screen.
Or wall mounted, or basically a second wall added
in the room. enclosure integrated within
 
Sorry for the long post. Well just for context I'm currently getting all new for my HT which is the living room which is 5.1mL x 4mW x 2.4mH.

So it's not massive. The LS50s are going to be replaced with something a bit better like R3 meta or maybe ever reference 1 or maybe different brand who knows.. I'm getting a monoprice HTP1 with Dirac bass control. And then hopefully the new Dirac ART in the future.

Wanting a 4 channel amp that can run the 4 X subs. No matter what they end up. Though probably sticking with the BMS in new boxes.
Actual power used is probably very little especially for music. Where they don't seem to break a sweat. But 4k lossless movies when buildings start falling down and things like interstellar are a lot bigger ask.again wattage wise I bet they aren't pulling anywhere near what the Inuke can actually put out.

The 2 subs I have can get to beyond 20hz quite easily with a bit of EQ when placed at the front corners. However I need at least 1 sub at the back corner to tackle some bad dips at around 40hz.

Problem is. Anywhere I put the sub along the back wall the FR drops off like a stone at 30hz at the listening position. But evens the response out nicely above that

So I need at least one at the back but then that's doing nothing to help the one at the front below 30hz

I'm basically wanting it punchy and good for music and very low for movies too. So I thought the BMS18 driver was ideal seen as it's sensitive and high xmax for a pro driver.

Don't think I was wrong there but due to the room I need another up front to help it down low with proper authority. And also having 2 would reduce distortion and how much they had to work.

Hope this makes a bit of sense
 
Have a look here - SB34NRXL75-8:
https://www.diyaudio.com/community/...rxl75-8-vs-sb29nrx75-6-vs-sb29nrx75-8.402671/

LAB12 is ok too but the SB Acoustics goes way higher and has a lighter membrane. LS50 could need low frequency help up to 200-250Hz - this could be a 3-way setup to get the full potential.

You need some EQ for the lowest frequencies when useing closed volumes! If you have enough membrane area and Xmax (and you have) just dial in the frequency response you would like to have.
 
And has a very well cooled and vented 3" coil. PA Manufacturers would power rate it at least double.
ScanSpeak also has such a 12" but is more expensive and as you need a few ...

Their 15" is also interesting in closed volumes but also more expensive and for subwoofer only ... I personal would stick with 2 12". Esp with LS50 on top.

The 10" is also interesting. Same 3" coil, HUGE venting hole in the back. Mechanical very robust and still no noises at Xmax and not to heavy membrane. Cheap for what it brings to the table, but for low frequencies only (I use the 12" up to 4-500Hz, 10" only to 100-150Hz).

Better than these is only Purify ... but we don't even know the price of the 10" and the 8" already costs an arm and leg.
 
Currently cross my ls50s at 90hz. I could experiment with higher but localising the subs could become an issue. With 4 subs maybe not an issue anymore.

The 15 would obviously be better for the movies. I'm thinking if I go the 15 then I wouldn't need to have 2 per corner. Just 1 may do for movies and to be fair. They would never be pushed with music to anywhere near distortion levels. Maybe the quality would be good when playing up around 150hz

Don't forget. I'm gonna be replacing the LS50 with something bigger anyway down the line. At which point ide probably be pissed I didn't get the 15s low more low end.

Decisions are always hard. Also. Wondering on the overall quality of the SB acoustics Vs the BMS. Sure it would be comparable?
 
The 15 would obviously be better for the movies.
Sorry but that's "old" thinking!
The GREAT thing from these closed subwoofers is that you can EQ them and adapt to the room as you like! You can boost 10-15dB if they can take the power! (I normally do around 6-8dB for cinema use but sometimes more is needed) Frequency response can be modified a lot - and that is often needed in a normal room cause the ROOM adds a lot of sh...marrn.
You can't EQ a reflex speaker under it's resonance frequency but for a closed box that's no issue. So - 2x 12" is very likely to give more output alt low frequencies as 1x 15" (but need to do the simulation).

I didn't measure the BMS but these HiFi Spekaers often have less THD and losses at low levels. But the BMS can take way more power.
You need to simulate if it reaches Xmax before the power maximum (which is often) then this benefit is not as important.
SPL in low frequencies is membrane area x travel, regardless of PA or HiFi chassis.
 
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Wanting a 4 channel amp that can run the 4 X subs. No matter what they end up. Though probably sticking with the BMS in new boxes.
Actual power used is probably very little especially for music. Where they don't seem to break a sweat. But 4k lossless movies when buildings start falling down and things like interstellar are a lot bigger ask.again wattage wise I bet they aren't pulling anywhere near what the Inuke can actually put out.
You could get a pretty good idea of what peak power your NU-6000 is putting out from the LED display:

NU 6000 meter.png

Your subs are probably a bit lower than 4 ohms <16 Hz, so the 0dB light should be near 3000 watts/109volts peak.
There is no headroom after the 0dB light illuminates- any more input level just current limits the output.

The -6dB light is around 750 watts/55volts at the impedance minima.
When buildings start falling down, if you see a peak to peak excursion of 19mm or less when that illuminates, the speaker won't reach Xmax at full tilt boogie. There is a possibility the SPL at those levels if sustained will actually flap or loosen drywall- a Mackie HRS120 with a 12" and passive radiator with far less displacement than one of your subs could do that.

Looking sideways at a little white dot on the cone and a ruler makes it easy to see what it's excursion is.
With that information you can estimate what you want and the minimum size cabinets that won't choke the excursion at the power they use.

Art
 
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