[rupnok]

Hi all,

Looking for sanity check/advice on how to proceed with a potential custom build of Danny's 12" sandbox sub. I have a large open floorplan living room (not my main HT, but an area I spend a lot of time with my spouse and children). My spouse has agreed that I can have dual 12" subwoofers... as long as they are integrated in a custom wooden console we're building that is going to span the length of the wall (image attached).

My plan is to build two of Danny's 12" sandbox subwoofers, and essentially have my cabinet builder build the console of drawers around the subwoofers. The subwoofers will not have room to breath – they'll be right up against the wall (and the amps will be a few feet away in a closet).

Am I insane? Should I look at other solutions, or – given the constraints mentioned above – is this a decent plan?

 

[Tyson]

I think it'll be just fine.  Nice win

[Early B.]

Make sure everything on the cabinet and inside the drawers is locked down. If not, it's gonna vibrate like crazy.

[rupnok]

Even with the "sandbox" design that Danny suggested? Any other recommendations for decoupling the subwoofer structure from the rest of the console? Should I line the outside box with foam/MLV or create space internally?

[Early B.]

Even with the "sandbox" design that Danny suggested?

Cabinet stiffness isn't the issue -- the purpose is to improve the sound by tightening up the bass. Low sound waves can cause vibrations in any room with any subwoofer, but more likely if the subs are integrated into cabinets. Not a big deal and easy to fix, but it's a consideration as you plan everything out. For instance, anything hanging on the front wall will vibrate a lot. Also, if your audio components will be on or in the cabinet, you'll want to consider investing in isolation devices. 
 

[EdwardT]

You could work with your builder to isolate those sections from the rest of the built ins and the wall then disguise the separation to maintain a seamless appearance. Add in some of Herbie's or Isoacoustics isolation solutions and you'll be good to go. Since you’re in the design stage and not working to modify existing structure you've got the advantage.

[rupnok]

@EdwardT – mind sharing a bit more detail / giving me more direction on what I should be telling my cabinet builder?

Should I thread IsoAcoustic GAIA's all around (top, bottom, back, sides) or wrap the entire sandbox with viscoeslatic foam or do a mix of both? I'm most concerned with ensuring the TV and my wallmounted speakers don't vibrate (the rest of my AV equipment is in rack ~10 feet off the side).

 

[EdwardT]

I had two thoughts: decouple the console sections and let a continuous top disguise the cubby holes for the subs, then line the back, sides and tops of the cubbies with NoRez. But then I looked at the mechanical drawing and realized it was only 15” to the top and an inch (without footers) shorter than the sub so that leaves me with no solution…

[rupnok]

@EdwardT – I am able to change the heigh of the console within reason (~probably could go up to 18").

My biggest issue right now is how to accomodate a flush toe-kick. I've asked Danny if I can adjust the measurements of the front baffle to "shorten" the height and "widen" the width without negatively impacting performance.

[EdwardT]

I think the flush toe kick might not be problematic if you use something like a cork filled rubber mat like a compressor isolator under the sub, adds 3/4” to the height placing the cone edge about 2 1/2” above the floor. So, the baseboard trim height comes into play, too. Still, that puts the cab top at 16 1/2”.

The top of the bottom drawer in my no-toe kick kitchen cabinet is 16” above the floor so I think maybe 18” to the bottom of the counter top is realistic. Make the topper at least 18” deep and there’s room for norez on the back wall, tight but workable. You'd probably have to connect via a side but since the amps are remote that part is easy enough.

[WGH]

You could work with your builder to isolate those sections from the rest of the built ins..

Edward is on the right track. Think of the subs and console as two separate units, they are not physically connected to each other.

After the console is installed the sub units are slid/rolled into their cubbyholes, a removable grill with toe kick is attached to the console with magnets for a seamless look.

Why separate units? In my experience speakers like to be fiddled with: crossovers adjusted, cables changed out, etc. Being able to pull out the subs makes all this easier, think about locking casters.

The plate amp will need ventilation. There is a limit to how long the speaker wire from the plate amp to the driver can be so the servo works properly, the amp may have to be installed somewhere on the sub cabinet. Since the sub will be hidden the plate amp could be installed on the top or side of the sub sandbox instead of the rear, or even make the sandbox extra wide and mount the plate amp on the front (cooling problem solved).

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You will need access holes in the console rear to reach the back casters.

As with all custom work, you need ALL the hardware in hand to physically measure it - THEN design the cabinet.

[rupnok]

@WGH – gosh, I hadn't even thought about whether I could install the plate amps ~10 ft away or not! Who do you think would be the right party to talk to about total length of speaker cable - Danny or Brian at Rythmik? Ideally I'd have the plate amps be remotely situated, so that I'm not having to consider extra cabinet ventilation or take away from drawer storage for my spouse's throw pillows, throws, and kid's toys...

That said, I think I'm conceptually understanding your feedback. In practice, I think this means having the cabinet manufacturer make the console in five parts: (1) the left and (2) right drawers under the windows, (3) the middle drawers, (4) a continuous top, and (5) removable grill/toekicks for the subwoofer sections. I'd have them leave two subwoofer sized :voids: that I can slide the subwoofers into – and have them make a removable grill piece that matches the drawers (including toekick).

I am feeling what you're saying about casters... but I think my preference is probably to slide into place on an isolation pad vs. casters...

[Early B.]

Allow me to throw a monkey in the wrench --

Why integrate the subs into the cabinets? You're complicating two things that may not go together -- the beauty of custom cabinets coupled with DIY subwoofers? 

My point is that your sound system components (especially speakers & subs) constantly change, but those custom cabinets won't change.

Here's another option -- do the custom cabinets need to extend from wall to wall? If not, place the subs in the corners and the top panel of the subs can be designed to fit with the cabinets. That way, if or when you decide to remove the subs, it won't affect the cabinets. And your wife can put some decorative lamps where the subs used to be.

[WGH]

Who do you think would be the right party to talk to about total length of speaker cable -

"We recommend only using the length of wire that is on each amp. That gives you about an 18" umbilical that will allow you to move the amp around behind the woofers quite a bit."
https://www.audiocircle.com/index.php?topic=164028.msg1744272#msg1744272


Feeling strong are you? The isolation pad will effectively lock the sub in place, if it's able to move or slide then it's not doing it's job.
"As I recall, I pegged the first ones [sandbox sub] at about 160 lbs. with amp and driver"
https://www.audiocircle.com/index.php?topic=84765.msg1440895#msg1440895

[rupnok]

Allow me to throw a monkey in the wrench --

Why integrate the subs into the cabinets? You're complicating two things that may not go together -- the beauty of custom cabinets coupled with DIY subwoofers? 

My point is that your sound system components (especially speakers & subs) constantly change, but those custom cabinets won't change.

Here's another option -- do the custom cabinets need to extend from wall to wall? If not, place the subs in the corners and the top panel of the subs can be designed to fit with the cabinets. That way, if or when you decide to remove the subs, it won't affect the cabinets. And your wife can put some decorative lamps where the subs used to be.

Honestly – I'd thought about this as well, but was worried about corner loading both subwoofers. Though we are using ~capable on-wall speakers (~rated to 60Hz +/-3db), I was planning on running the subwoofers at either 90Hz or 100Hz crossover, and was a bit worried about localization (hence the placement of them at 1/4 and 3/4 of the wall length).

Corner placing them in ~24" x 18" voids solves almost all my problems – I can decouple them completely from the cabinetry, and also attach the amps directly to the subwoofer.

[Early B.]

Honestly – I'd thought about this as well, but was worried about corner loading both subwoofers. Though we are using ~capable on-wall speakers (~rated to 60Hz +/-3db), I was planning on running the subwoofers at either 90Hz or 100Hz crossover, and was a bit worried about localization (hence the placement of them at 1/4 and 3/4 of the wall length).

Whether placing the subs in corners or cubbies, neither one is ideal. Localization will likely occur either way, but it's a minor consideration, IMO.

[WGH]

A lower crossover point would be preferable, less localization if you will be using the setup to play music. My sub is crossed over at 30 Hz (stereo) and I have no idea where it is. Crossovers are not brick walls but slopes. A 100 Hz crossover point will allow the sub to play up to 200 Hz with music or video without a LFE track.

My Anthem AVM60 is only used for movies and video, the 200 Hz High Frequency Extension doesn't produce any localization because of the digital filter built into the LFE track.


"Dolby Digital’s LFE channel carries additional bass information from 120 Hz on down. This is not a roll-off but a digital brick wall (i.e., no 121 Hz info), so the content is usually rolled off by the sound engineer starting around 80 Hz for a smoother blend."
https://hometheaterhifi.com/editorial/the-misunderstood-01-lfe-channel-in-51-digital-surround-sound/

REL, the company that only makes subwoofers, likes a corner placement for their subs:

"When possible, the REL should be placed in one of the corners behind the speakers. Remember, we are
dealing with true LOW bass pressurization with RELs. Low bass pressurization below 40Hz is best derived
from corner placement, where the most linear and efficient low bass can be produced."

"The optimal position for a REL is in one of the corners behind the main speakers. This position
provides 9 dB of mechanical amplification and allows for the most linear true low bass wave launch,
owing to the ability to tune the REL to the longest distance in the room in order to produce the longest,
therefore lowest, bass waves."

[rupnok]

Many thanks to everyone for their help. Have decided to abandon the idea of fully integrating the subwoofer into the console, and instead will build in two areas in the corner of the console to slide in subwoofers with attached amplifiers. Have changed my electrical and low voltage plans to ensure there's one outlet per each cubby and one RCA out (which will feed independent LFE signals from my Denon receiver).

I will look at using those heavy duty casters and may also look to MLV line the cubby to add some mass to reduce risk of resonance. 

[Digi-G]

For what it's worth I've got a single SVS sub that I've tried in 2 different corners of 2 different houses.  Each time it excited the room mode and gave me a big hump around 40-45Hz.  My previous sub was a Velodyne and both manufacturers recommended corner placement.  But it's never worked for me and I've gotten smoother response moving the sub down the side wall, about 8-10 feet from the corner. 

YMMV,

[JWCoffman]

I've got two of the sealed servo subs that are working well with corner placement behind the L&R speakers and crossed over with my MTM's at 70hz.  This helped reduce my room mode at 45-50hz which was really bad when I only had one flabby sub with the MTM's.  Obviously, every room and setup is different, but my experience has been good with this arrangement.