Number and size of subwoofers in a larger space?

[nicoleise]

Hello,

I'm building a living room home cinema that is currently in the construction stage and will be a lenghty project. It will be 9.X.4, and I will be attempting to hide most of the speakers. The subwoofers I would build custom backboxes into the side walls for to end up with something similar to a baffle wall.

I have little experience with listening spaces this large, nor with what many subwoofers do in a space, apart from a more even response. My main speakers (JBL Ti10k's) have very accurate/tight/fast bass, and even at high levels, the woofers hardly move/excurse, yet the output in the room is definitely both felt and heard.

So an obvious concern of mine is the subwoofer(s) "mudding out" this perception. My "pocket logic" tells me, that this would especially be the case for higher excursion woofers that need to travel a lot when pushed, and thus the same logic tells me that likely I should be looking for larger woofers, that don't need significant excursion to create the same output.

JBL did make matching subs for these (TiK Master Sub and TiK Sub), but they are rarer than gold and diamonds. They are 15" powered units, with some built-in DSP system where the master sub will control up to 3 slave subwoofers. I believe it never really worked as intended. But apparently, JBL felt 15" were a suitable "partner size" for these main speakers, but there could be many commercial or aestetic factors involved in this decision also.

My priority isn't so much low-end extension. The first priority is precision and the second priority is volume/output enough to fill the space without throwing precision completely under the bus when at near-reference levels.


The reason I'm asking this so early in the project is that a fair priced listing showed up yesterday for 3x JBL ES250P/230, which are 12" powered units. I already own a very similar JBL E250P/230, so this would be a quick and fairly cheap path to a 4x12" system. But while I can gather that one of these units would be hard-pressed to remain accurate and convincing while serving a space of this size, I have no idea if using 3-4 of these actually adds so much that it's easily enough for the space.

If they are enough, it would be a cheap and easy path to a lot of performance. But if they end up coming short, then it's just pointless time spend and storage of these units.

So - can anyone suggest what it is I should be looking for in terms of subwoofers? I get that drivers are built different, so it's impossible to just say 18", but still I'm guessing there's a "suitable range" or so.

• Room dimensions are difficult, because it's in open connection to most of the space. The listening space itself, I would define as 6m/19' wide by 11m/36' deep. It's under a pitched roof, so the ceiling is 46°C and symmetrical to the room. The tip height is something like 3,7 m/12' and at the side walls about 0,9m/3'.
• The distance from subwoofers to MLP will be something like 5m/16½' on average
• The sidewall cavities can be made roughly 0,9m/3' tall and deep, and would make a triangle if viewed in profile, since the roof pitch is 46°. The width can be as desired, but max 1 m/3' would be ideal. I could extend the box inside the construction or even build two boxes next to each other and connect them if needed.
• I'll be using some form of DSP (time alignment and bass management).
• I usually listen at something like reference -20 dB, but occasionally, I listen at reference, and I'd like stuff to still be cohesive at that point.
• I don't have a preference for a certain number of subs; I'd like at least 2 (even response) and no more than four (construction constraints).
• Surround speakers are JBL Ti2k (6½" woofer), center speaker unknown. Will either be a "butchered" Ti10k, a Ti2K or perhaps 2x Ti-C center (dual 5 1/4" woofers) in an above/below configuration, but the centers sound pretty astmatic compared to the rest of the range, so most likely either another Ti2k or if I can find a used Ti10k or two that I can bring myself to cut into pieces, then a DIY cabinet based on those components to try and match the L/R within the design constraints of the room.
• As per above, probably looking for "coverage" in mainly the 20...60 Hz range, with some overlap to the bed layer speakers according to what in-room measurements end up showing.

If more information is needed, please don't hesitate to ask.

Thank you,
Nicolai

 

[shadyJ]

The JBL E250P/230 are probably OK but just don't expect them to dig super deep. I would be surprised if you got deeper than 30Hz bass with those. Calibration will be everything for what you want, as well as a multi-sub setup. Optimal placement will be critical, so I hope you have flexibility in terms of where the subs can go. I would just make it easy and use some variant of Dirac, especially with Dirac Bass Control, but you can calibrate manually too, although it does take some time to learn. I wouldn't worry so much about what subs to get (above a certain level of performance - don't use supercheap budget subs) as how and where to set them up.

 

[nicoleise]

Thanks, Shady.

The JBL E250P/230 are probably OK but just don't expect them to dig super deep. I would be surprised if you got deeper than 30Hz bass with those.

Datasheet says 25 Hz, but doesn't mention the dB value. I assume @-3dB since it's JBL after all, and based on my experience with the E250P, it seems valid though, it does go deep for the size. I don't need infrasonic performance, so something like 25 Hz would be absolutely fine for me.

I'm just not sure if they have to "work too hard" to fill the space and thus not have the "reserve" to be able to actually deliver a convincing, accurate and tight result in the much larger space, even if there's 3-4 of them. It's simply two "major components of the equation" that I have too little experience with the impact of (large room, many subwoofers).

I guess my notion that fx an 18" driver at X output is better (quicker/more accurate) than a 12" driver at the same output (providing the output is within reach for both drivers) is incorrect? I imagined that a larger driver that has to travel much less to apply the same amount of energy into the room would be faster due to the minimal excursion (and thus; providing the mass isn't excessively larger, less inertia), resulting in a tighter sound?

These JBL subs are fairly high excursion. If I recall somewhat correctly, it would appear to be (it's difficult to actually see) something like maybe 3/4" in each direction when it was really going.

Calibration will be everything for what you want, as well as a multi-sub setup.

I agree, and haven't decided on DSP yet. I'll pull conduits and setup an in-wall rack, so I can decide later. But generally, I would prefer something I'm in direct control over rather than a "push-to-run" solution.

I guess maybe discrete power amps and a miniDSP between those and the processor/receiver, but it's a pretty cumbersome solution.

Optimal placement will be critical, so I hope you have flexibility in terms of where the subs can go.

Once build, no real flexibility. Until then, some. I did model the placement in REW and played around with it, and it seems to calculate good results with these locations, definitely something that would be useable as-is, so with DSP it should be fine. I realize it's essentially a crude calculation, but better than nothing.

I would just make it easy and use some variant of Dirac, especially with Dirac Bass Control, but you can calibrate manually too, although it does take some time to learn. I wouldn't worry so much about what subs to get (above a certain level of performance - don't use supercheap budget subs) as how and where to set them up.

Thanks.

 

[William Lemmerhirt]

That’s a lot of airspace, and if it’s on concrete those JBL subs will be just about worthless imo. As shady said, they won’t do much below about 30hz, and a high quality sub should at least go down to 20hz, and even if you had 50 jbls’s, they won’t dig any deeper than a single one. Also there’s no way that you’ll be able to hide subwoofers in the room that are able to offer much impact. They will need to be large.
If this were my space starting from scratch. I would call Tom from PSA m(founding member of svs), and tell him what you’re doing. He will have a good idea, and not try to upsell you. My other choice would be a pair of 15-18” subs from Rythmik. You could possibly build a TH(tapped horn)into a wall, similar to what @TLSguy did in his living room. He’s also designed some nice diy subs using affordable Dayton drivers.
Or a custom sized Marty, or devastator. Short version, if you want a quality bass system, it will be an investment in time and money. Buy once, cry once.
Edit: your assumption about driver size is basically correct. However the overall design of the subwoofer as a whole is what matters.

 

[nicoleise]

That’s a lot of airspace, and if it’s on concrete those JBL subs will be just about worthless imo.

Thanks William,

It's a wooden construction 1st floor (first floor above ground floor, so I guess 2nd floor in the US?), so no concrete. But yes, it's a large space and it's connected to even more space. In fact, one of my simple challenges is to define the space that is the home cinema (in terms of sound). It's a simple, yet confusing space.

I'll try and add this snip from the 3D model at an early stage of drawing it, maybe that helps:

The white areas top/bottom are the "crawl spaces" (I don't know what they're called in a ceiling/loft type situation) outside of the side walls. This is where I'll place the surround speakers and subwoofers. The height speakers will go in the ceiling and are DIY builds.

L/R are visible on the floor, C can also just be seen. "A1" is "front subs" and not shown (added based on REW modeling) is rear subs at the South corner by the roof terrace (2) and either directly opposite in the North space or pushed back to where the kitchen starts (3).

So the subs will be roughly 11-12 m between front and right and roughly 6 m between left and right. And roughly 7 m to the MLP from each sub.

Distances from the front wall (with the three "funny" windows on the left/West):

• MLP: 5,2 m/17'
• (1) 8 m/26 1/4' to the rear most speakers (so the end of the listening area, if you will)
• (2) 11,3 m/37' to a built-in roof terrace that protrudes about 1,5 m into the room.
• (3) 13,6 m/44½' to kitchen cabinets+terrace reduces width at floor level to 1 m
• (4) 18,2 m/60' to the nearest "back wall", but it doesn't actually enclose the space
• (5) 26 m/85' to the final "back wall" that also doesn't enclose the space

The wall at (5) doesn't enclose the space, since the corridor continues North another 82' m, before being fully enclosed, but since the room between points 4-5 will be cladded with acoustic panels on both W, S and E sides, I don't think whatever sound remains at point 5 can actually traverse the corner and continue, and especially not return all the way back to the MLP. We might at some point figure out some place where a pocket door can be added, but it's difficult with the sloping ceiling.

The width of the room is 5,5 m/18' at floor level when the acoustic cladding on the side walls is taken into account.

The opening to the North "above" the sofa is 2,8 m/9' wide and 1,1 m/3½' deep.

I hope this sorta clarifies, I personally really struggle to explain it it writing.

As shady said, they won’t do much below about 30hz, and a high quality sub should at least go down to 20hz, and even if you had 50 jbls’s, they won’t dig any deeper than a single one.

That I get (that more subs do not reach deeper).

Also there’s no way that you’ll be able to hide subwoofers in the room that are able to offer much impact. They will need to be large.
If this were my space starting from scratch. I would call Tom from PSA m(founding member of svs), and tell him what you’re doing. He will have a good idea, and not try to upsell you. My other choice would be a pair of 15-18” subs from Rythmik. You could possibly build a TH(tapped horn)into a wall, similar to what @TLSguy did in his living room. He’s also designed some nice diy subs using affordable Dayton drivers.
Or a custom sized Marty, or devastator. Short version, if you want a quality bass system, it will be an investment in time and money. Buy once, cry once.
Edit: your assumption about driver size is basically correct. However the overall design of the subwoofer as a whole is what matters.

They have to be hidden. It's not the usual (WAF), my wife likes speakers, prefer them to not have grills on, etc. I just personally find a pair of nice (tower) stereo speakers to be "pretty" but speakers everywhere to be visually way too overwhelming. Especially with sloping walls and such.

The "crawl spaces" (that I still don't know what to call) offer something like 40 l/1,4 cf per meter wall space, and I could combine more than one "cell" and connect them internally (behind the studs). But I see your point, my DIY 12" sub was 74 liters/2,6 cf (ported cabinet).

My plan (before seeing the mentioned listing) was similar, and I'm aware of TLS Guys setup, and was hoping for his advice when time comes for the build. I figured DIY would be the only way to get the performance maximized in the space on offer. I could obviously do more insane things, like build a mega sub over the kitchen cabinets at (4) on the plan, but I'd also like to sorta "constrain" the noise from the home cinema to the listening area as much as possible.

I wont call Tom, since I'm in Europe, and thus there's not likely any sale in it for him. But thanks.

I don't so much mind having to pay something for drivers, amps, materials and spending time on the build, if the result is great. The reason the listing appealed to me was simply that if the JBL subs are essentially already adequate-to-overkill when using four of them, then my efforts wouldn't really increase the end result. It's that evaulation I struggle to make at the moment, with my limited knowledge with both many subwoofers and larger spaces.

And since the price was also attractive, no reason not to snatch them up if they'd do a good job. If they wont though, it's just a pointless expense.

 

[shadyJ]

I guess my notion that fx an 18" driver at X output is better (quicker/more accurate) than a 12" driver at the same output (providing the output is within reach for both drivers) is incorrect? I imagined that a larger driver that has to travel much less to apply the same amount of energy into the room would be faster due to the minimal excursion (and thus; providing the mass isn't excessively larger, less inertia), resulting in a tighter sound?

All other things being equal, yes, an 18" has an easier time moving air than a 12", but all other things are rarely equal. Definitely do not judge subwoofers by their cone diameters.

These JBL subs are fairly high excursion. If I recall somewhat correctly, it would appear to be (it's difficult to actually see) something like maybe 3/4" in each direction when it was really going.

They may have a 3/4" Xmech, but what matters is linear excursion, and they will not have near 18mm of linear one-way excursion. I would guess 10mm or 11mm or something in that ballpark.