I'll skip the long backstory. Is it possible/feasible to build a subwoofer into this corner fireplace/TV area? The rough volume is about 60 cu ft. (equilateral triangle with two 56" sides yielding an 80" face, about 75" tall after a divider is accounted for). Yes I know it's not an ideal sub box, but we're trying to maximize space and avoid building an entirely separate box just to sit on top of, what is effectively, a giant box. Also, the sides are about as rigid as you get (framed house exterior on two sides, thick tile on the face) so that's a big plus!
We're not looking for crazy high SPL, more concerned with extremely low bass and overall SQ vs an off-the-shelf solution. I'd love to get flat to 35hz if possible. Since it's lower SPL, we're hoping the fireplace wont' rattle, but it's a risk we're willing to take.
1. Is this at all feasible or just completely ridiculous?
2. If feasible, what driver would you recommend?
3. Ports? Batting? Any other suggestions to maximize results (given obvious constraints).
4. Even after all that, are we likely to get better results from a MUCH smaller, but properly designed and/or built 15" or maybe even 18" sub? I'd like to go passive, so something like a JBL MRX or EV (I come from the pro audio world, so not too familiar with equivalent home stereo boxes)
Thanks fellas!
We're not looking for crazy high SPL, more concerned with extremely low bass and overall SQ vs an off-the-shelf solution. I'd love to get flat to 35hz if possible. Since it's lower SPL, we're hoping the fireplace wont' rattle, but it's a risk we're willing to take.
1. Is this at all feasible or just completely ridiculous?
2. If feasible, what driver would you recommend?
3. Ports? Batting? Any other suggestions to maximize results (given obvious constraints).
4. Even after all that, are we likely to get better results from a MUCH smaller, but properly designed and/or built 15" or maybe even 18" sub? I'd like to go passive, so something like a JBL MRX or EV (I come from the pro audio world, so not too familiar with equivalent home stereo boxes)
Thanks fellas!
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35Hz is a good compromise for size vs low for PA, but not considered "extremely low bass" in home stereo/theater usage.
With that amount of real estate available, flat response down into the low teens is possible.
That said "flat" does not exist in most rooms, DSP (digital signal processing) should be considered in the design from the start.
The fireplace won't be the only thing that rattles ;^).
Mounting pairs of drivers facing each other ("slot loaded") can reduce mechanical vibrations considerably.
Very feasible, though "crazy" high SPL does not require near that much enclosed volume.
Your choices regarding infinite baffle, horn load, bass reflex, the upper crossover point and cabinets, low frequency extension and sound quality all may lead to different recommendations.
All depend on decisions for #2.
The JBL MRX518S rolls off below 60Hz, -10 dB at 40Hz, -20dB at 30Hz.
With the volume you have available, you can get a response that looks similar, but moved down two octaves.
That said, often multiple small subs placed (hidden) around the room can give more even results than a single corner location.
Art
Yes…..it’s better than an ideal box…..being so large, it’s closer to an infinite baffle in practical operation.
Once you remove the firebox, you’ll have access to the interior portion to add bracing and damping material. You should also be able to seal it up with expanding foam pretty easily. Lightly stuffed, acoustically the volume will increase significantly.
Two 18” drivers would likely give you in room performance to 20hz and below with rational SPL.
Once you remove the firebox, you’ll have access to the interior portion to add bracing and damping material. You should also be able to seal it up with expanding foam pretty easily. Lightly stuffed, acoustically the volume will increase significantly.
Two 18” drivers would likely give you in room performance to 20hz and below with rational SPL.
Why?
You are in the range where the room totally dominates, so active with EQ is almost always a better solution.
You have a huge enclosure to use. Go sealed with EQ and enough power IMO.
60 cu.ft lets you get close to IB loading with some drivers, especially modern 'pro subs'.
Common universally loved sub drivers with measured excellent performance.
The BMS 18N862 is hard to overlook.
If you want something flat into the teens that can deliver serious SPLs.
Stereo integrity's HST 18 and 24 are absolute monsters, with excellent Klippel measurements.
The downside is the price, weight, and lower efficiency.
If you want to go passive, ported is likely the better option for the efficiency gain down low, and a 'sub' with a lighter cone and higher efficiency.
Like JBL 2245H,TAD 1801, Faital 18FH500 etc.
The amps I'll be using utilize Ashly Protea DSP, which I've used before and am familiar with. They also connect to the network via ethernet, which is a big plus for controlling remotely.
That's really interesting. I only have about 800W worth of power to play with, so maybe two 15" drivers, slot-loaded in a "drop in box"? Someone else recommended building a drop-in unit....this might be a good version of that idea? Generally speaking, "better" than a single 18 (for SQ, LF extension, sensitivity).
Yeah, I don't need crazy high SPL....just good loud listening volume, but it doesn't need to **** off the neighbors.
Okay, this is much of why I'm here for help. I know enough about audio to know that each of those things will have its own set of benefits and trade-offs and may or may not be more or less ideal for the weird cabinet I'll be using to achieve the stated goals of moderate SPL with good LF extension and SQ....and preferably a driver with good sensitivity to get the most out of limited wattage. It could take years (decades) of immersion in speaker building to make a truly informed decision. I'm just not there.
I realize it's a big ask, but off the top of your head, what type of design would you choose for this purpose if it were your home?
That would be awesome, even one octave lower would be fine with me. In my pro audio work, I use subs that are flat down to about 35hz (Meyer LFC 1200 and soon 2100....look em up, they're fun). I have not once pined for more LF extension. Then again, I've never experienced a proper home theater with legit LFE....so maybe I'll defer to you guys on that as well. Whatever you think is best for this purpose.
We tried to figure out ways to do that....with the limited space in this build, it just wouldn't be feasible. We would've had to remove considerable cabinet space in the kitchen.....try explaining that to your wife.....good luck lol
Thanks Art, I very much appreciate the help!
I'll have EQ/DSP for sure (graphic, parametric, limiter, subharmonic synthesizer, etc.) and I'll be tweaking the system with SMART or REW. The reason I want to go passive it because all the amps driving the house speakers (14 in total) are Ashly Protea network enabled. They not only provide DSP, but allow us to control levels remotely via computer, tablet, or wall panel, or even port into from afar via the interwebs. I'd really like to get the sub amp on the same network so everything can be controlled in this way. Also, if you blow the amp on a powered box, you've gotta repair the damn amp module, which can be expensive and a big PITA, sometimes not even possible if schematics are proprietary and/or parts are unobtanium. If you blow an amp in a passive system, just replace the amp and you're good.
When you write passive, most of us will think a simple amplifier, with inductors and caps as the only way to cross and no EQ at least that's where my head goes. So a bit of a misunderstanding maybe 🙂
An Infinite baffle sub utilizing the entire fireplace enclosure volume will produce the least amount of vibration related noise, play the cleanest and extend lower than any other option mentioned above other than the multi sub/swarm approach. I would not hesitate to do an IB and for the ultimate, make 4 small sealed 8" or so midbass modules placed around the room...that would be epic for both music and theater.
Looks like a modern "fireplace"-screen. from the pictures. If not that construction would be a serious fire hazard as pictured.
Also if a real fireplace that is used, well thermal issues.
Larger cones are more sensitive, 2x18" roughly +3dB (half the power required) over 2x15".
800 watts is ambiguous, how many volts can your amp(s) produce into what impedance? I used 4 ohm nominal drivers in the simulation below.
Something that goes an octave lower than what we might use for PA
Push-push to reduce mechanical vibrations. I did not include the plenum (slot) in this simulation, it would add some upper "punch", but the low end wouldn't change much at all. I chose the BMSN862-4 for you because of it's low Fs, low distortion, and relatively lightweight cone is more sensitive than other "PA" subs designed for small enclosures.
With a HP around 14 Hz the pair won't run out of excursion to below 16Hz, super clean.
124dB at 16Hz is pant leg flapping territory, though you probably won't go that loud (unless you want to).
You don't miss it until you have heard it, but the size needed for LF extension prohibits it's use in PA cabinets- I compromised at 36Hz Fb (box tunings) when I was doing PA. My 8" studio subs have an Fb od 24Hz, over 1/3 octave lower than the
Couldn't find a LFC 1200, but the above cabinet would go about an octave lower than the LFC 1100 or 2100, and not require 8000 watts (peak) to get there.
With high excursion high power drivers, cabinets as small as 1 cubic foot can get loud and low, but would rattle the pots and pans