Help with SW alignment

[mga2009]

Hi,

I've got 6 SBacoustics SW26DBAC76-3-DV 10" subwoofers.

These are shallow subwoofers and do work in small boxes, however, that is kind of inconvenient when tuning the boxes too low as the port is quite large...

These will be used in a (very) small room for home theater/movies, with solid walls and ceiling, so probably have good room gain.

SBacoustics recommends a Sealed box between 9 and 21 liters. What alignment would you recommend? Would you mount them single, in pairs or in trios?

Looking forward to your help

 

[digitalfrost]

If you got 6 and they don't need a lot of volume, why not build them dual opposed. So 3 subs with 2 chassis each on opposite sides of the enclosure. This will ensure the enclosure is inert and the subs won't be wandering about the floor even if they are not heavy.

These seem to have dual voicecoils? The TSP seem to be for parallel connection. If you were to put 2 chassis in 1 enclosure, it could make sense to wire the voice coils in series and have the chassis in parallel.

Closed boxes are easy to tune, since you have so many chassis and membrane area if they don't go deep enough you can easily add a boost via DSP.

According to my calculations, 10l per chassis are enough for Qtc of 0.707, so you could build very compact subwoofers indeed.

 

[alex-z]

Personally I would build 3 subs, each with 40L of volume and 2 drivers so you get an early but gradual bass slope suited to small rooms. Spread them throughout the room for good seat to seat consistency, then apply global EQ as needed.

If you only have a single listening position you should also time align the subs for that single position.

 

[mga2009]

If you got 6 and they don't need a lot of volume, why not build them dual opposed. So 3 subs with 2 chassis each on opposite sides of the enclosure. This will ensure the enclosure is inert and the subs won't be wandering about the floor even if they are not heavy.

These seem to have dual voicecoils? The TSP seem to be for parallel connection. If you were to put 2 chassis in 1 enclosure, it could make sense to wire the voice coils in series and have the chassis in parallel.

Closed boxes are easy to tune, since you have so many chassis and membrane area if they don't go deep enough you can easily add a boost via DSP.

According to my calculations, 10l per chassis are enough for Qtc of 0.707, so you could build very compact subwoofers indeed.

They have dual 3ohm VC, so the best alternative is probably a total 6ohm load on each box (dual SW in a single box). The "problem" I have with dual opposed is that at least 2 of these SW boxes will me bellow and between the TV rack; should I aim one driver firing to the front and the other to the back wall? Or both aiming to the TV rack walls? I attached a picture showing them with the drivers mounted aiming both to the front. In any case, if getting the woofers to close to the wall or the furniture is NOT a problem sound wise; I recon it will save me a good chunk of real estate space.

Personally I would build 3 subs, each with 40L of volume and 2 drivers so you get an early but gradual bass slope suited to small rooms. Spread them throughout the room for good seat to seat consistency, then apply global EQ as needed.

If you only have a single listening position you should also time align the subs for that single position.

Sealed right? Also... does it make any difference If I have 40L for both drivers, or 20L for each driver in separated chambers?

I do have only one listening position, so I will take the TA recommendation.

 

[digitalfrost]

If you really want to put them right in front of the wall, maybe dual opposed is not a solution. You could put the chassis top and bottom and attach some feet so raise the enclosure off the floor, but I'm not sure if thats the most sensible way to go about it.

Generally because these chassis need so little volume you have a lot of freedom in how you design the case, but I can see you're probably trying to match the other furniture height. The sub next to the couch could be built different to the ones on the front wall. Maybe think of downfiring woofers, just to protect them from people who might accidentically hit the chassis with their feet.

You could make a nice sidetable for the couch. Built this dual-opposed to prevent it from rattling, raise it however much you need to be able to put stuff there and have it reachable from the couch.

Are we even volume constrained here? My general impression is you have a lot more volume than is actually needed. Not that it's a bad thing.

 

[mga2009]

I am not volume constrained, but I want to match the furniture heigh, so that I can use the top surface of the rack.

Good idea about the SW near the couch, I will definitely consider it.

Regarding the dual opposed... what about both drivers opposed, cone to cone, each with individual 20 lt. internal sealed volume, both separated by a central manifold 10cm wide... is there any advantage? drivers should work on or off phase? Something like the picture attached (credits to Sebr023) or like this:

DIY - Dual 12" Sub · Jul 23, 2016âââApr 23, 2020 ð¸

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photos.google.com

I think this design will give me the benefits of a dual opposed SW, cancelling forces and also allow me to make a shorter -alas wider- box.

​

 

[digitalfrost]

"drivers should work on or off phase?" they need to be in-phase for the force cancellation to work.

The DIY sub you linked reminds me of ripoles https://www.audiosciencereview.com/forum/index.php?threads/diy-ripole-subs.7575/ but ripoles would have the rear chamber open to the other sides. These seems to be closed box. The thing is, this cavity between the drivers will have a resonance that you need to take into account. Here is another member simulating a similar design:

Slot Loaded, Dual Opposed 8" Subwoofer (suitable for on wall/high shelf mounting)

I have started designing a subwoofer suitable for wall mounting. Like most, my room is not ideally shaped but I would like to locate a sub in each of the four quadrants of the room. This means locating at least one sub high up on a wall above a window. To minimize cabinet vibrations the...

www.audiosciencereview.com

If you crossover low with 24db/oct filters it might be okay, but shallow filters and higher crossover frequency could make the resonance audible. As for the chamber size, I would try to make it at least 2 * Sd * Xmax from the volume and have the opening at least 2 * Sd in size if possible. If you go lower the air mass in the chamber can increase the membrane weight and it will lower Fs. Ripole subs utilize this.