The dual Ikea Kallax subwoofer

[Tell]

Now that the kid is finally starting daycare, which means dad is finally getting a bit more free time, and now with some decent finances and a with a new living situation that allows it; it's time to build some bass! But being a bit of a minimalist and with WAF to consider the plan is to squeeze them (yep, I want two) into a Ikea Kallax.

The internal dimensions of a Kallax according to my ruler are 34x34x34 cm (with a few mm of variation, probably due to imprecise assembly), which gives 39 liters. But since I want a bit of margin on the sides (where I'm also considering adding some kind of wedge) I lose about 0.5 cm on each side, and with 16 mm thick panels that leaves me with a remaining volume of 25 liters.

I've set my sights on the Dayton Audio DSC255-4, a 10” driver with a Vas of 32.1 liters and an Xmax of 8.3 mm, which costs around 170 EUR from Soundimports.eu. I’m planning to tune the box to 35 Hz using a 3D-printed flared port, based on this guys work. 25 cm long, with an internal diameter of 6.1 cm and an exit flare of 9.2 cm. According to the designer’s excel sheet this gives a max port SPL of 99 dB which I assume means that above that there's a risk of port noise? I’d obviously like something larger, but with a 9.2 cm port on the front, space gets very tight since the driver also needs to fit. A regular straight port of similar size in WinISD shows a velocity around 50 m/s at 200W, which is quite extreme! Though maybe the flared port can handle it better? I have considered placing the port on the back, but I’d prefer (look wise) to keep the Kallax as close to the wall as possible.
The driver, port, and bracing will take up a few extra liters, so the total volume looks like it’ll end up around 23 liters, not a lot but still a fun challenge for a minimalist like me

WinISD gives me this curve, which I think will perform quite nicely with a bit of EQ, at least compared to what I’ve had since moving to Norway seven years ago.

What do you think? Should the port go on the back after all? Or use two of them? Are there maybe even better drivers for a Kallax (preferably in the same price range)? Or should I drop down to 8” to better accommodate the port?


And this might be something for later on though, but I'm also thinking how to integrate them with my current Ino Audio piP? Those actually play quite well down to 30 Hz despite their small 4" woofer, but of course I want more SPL! And just as important; a smoother bass response in the living room. So I’m thinking of letting the piPs still run full range but at a lower level, and then supplementing them with these Daytons placed between them under the TV to help even out the bass.
Or is it better to just cut the piPs at around 80 Hz and let the subs handle everything below that?

 

[digitalfrost]

I tried that once. The problem is the whole thing will rattle with the subwoofer. If you don't play loud it might be fine, but going for it the vibrations will extend to the whole rack and everything in it / on it.

 

[Tell]

I tried that once. The problem is the whole thing will rattle with the subwoofer. If you don't play loud it might be fine, but going for it the vibrations will extend to the whole rack and everything in it / on it.

Don't really have anything on top of it, and the other drawers will be filled with fabric so I don't think vibrations will be that big of a problem

 

[Elgrosso]

Cool idea! I love messing with ikea stuff too, can’t even remember everything I tried.

I agree with digitalfrost it will rattle, but it might not be an issue as it will depend of spl, isolation, placement etc
The kallax panels being hollow with honey comb, they will also resonate.
I built one in the same 4x1 once with a 15’’ and 18mm mdf all around inside and plywood front and back, but I had to brace the hell of it and still had to cross it low.
kallax using very thick panels, with the added internal mdf, braces, driver, port etc you lose volume very quick compared to the external volume.
Maybe you can find some more in hidden areas, a bit in the back, below with a fake support, or even in the middle using the baskets as fakes.
Sealed could be easier to manage.

To mitigate resonances and vibrations I also tried different solutions, but with ekets (higher WAF, radmanso too).
Adding sand in between panels after removing the honeycomb, worked very well.
Or concrete, but not as easy, and too heavy at the end.

 

[digitalfrost]

And this might be something for later on though, but I'm also thinking how to integrate them with my current Ino Audio piP? Those actually play quite well down to 30 Hz despite their small 4" woofer, but of course I want more SPL! And just as important; a smoother bass response in the living room. So I’m thinking of letting the piPs still run full range but at a lower level, and then supplementing them with these Daytons placed between them under the TV to help even out the bass.
Or is it better to just cut the piPs at around 80 Hz and let the subs handle everything below that?

So, seeing that you need to integrate them with existing speakers, the woofers will be placed close to the wall, this kinda calls for a DSP enabled setup.

At first I thought to recommend a closed box setup since they're so close to the wall, but then I thought, eh the less membrane movement the better, so why not go for bass-reflex. I'd put the ports on the front there's really no space for them somewhere else.

Be aware that 25l for this chassis tuned to 35hz is already plenty of bass, with as you can see a rise in frequency response. A chassis with lower Qts would be suited better, but it's always a problem to get BR ports to fit into tiny enclosures.

Chassis wise.

SB Acoustics SB23MFCL45-4
Dayton Audio RSS210HO-4
Dayton Audio RSS265HO-4

These all would fit better into the volume you're having, requiring around 20l to work well. If I simulate your chassis it's more like 60l.

How you arrive at 35hz tuning with such a short port I don't know. My simulations arrive at ports length between 114-140cm. Maybe sealed and DSP would be the better solution.

 

[audio_tony]

Isn't the Kallax hollow wood with cardboard inner? I'm sure it's not solid wood, so you'd need to line it with something substantial like 18mm MDF, which would lose even more volume.

 

[Keith_W]

Isn't the Kallax hollow wood with cardboard inner? I'm sure it's not solid wood, so you'd need to line it with something substantial like 18mm MDF, which would lose even more volume.

Ikea stuff is made with particle board with a melamine veneer.

Particle board is essentially sawdust / woodchips held together with glue.

Most people use MDF, which is sawdust held together with glue, but compressed so that it is stronger.

 

[Talisman]

I assure you, the Kallax is internally made of a cardboard honeycomb structure; I had to drill holes in it for a job. This also explains its remarkable lightness despite its thickness.
I don't think it's possible to use its walls for subwoofers; the results would be terrible.

 

[Keith_W]

You are probably right. I don't own a Kallax. The only IKEA stuff left in my house are my Billy bookcases - those are particle board.

 

[LTig]

I assure you, the Kallax is internally made of a cardboard honeycomb structure; I had to drill holes in it for a job. This also explains its remarkable lightness despite its thickness.
I don't think it's possible to use its walls for subwoofers; the results would be terrible.
View attachment 463158

Yep. Just knock it with your finger and it sounds really loud.

 

[voodooless]

Having built a sub into an Ikea cabinet before, some tips:

since I want a bit of margin on the sides (where I'm also considering adding some kind of wedge) I lose about 0.5 cm on each side

This is probably a good idea to do, but still, I had the enclosures vibrate against each other, and at certain frequencies, this gives highly audible resonances. So either make the margins big enough, or make sure to stuff the room with something like felt.

If you hang your cabinet on the wall, make sure to brace the underside; otherwise, it will sag. This can be achieved with an aluminum L-profile screwed along the back side, for instance.

As @digitalfrost mentioned, there is no way that short port is for 35Hz. I used a slot port that is actually already way too small, and it was really long (about the same tuning).

Maybe just go for two 12" woofers in a closed box? Or 4 on opposing sides to remove the vibrations. One of these will probably do well:

Loudspeaker Database

Not surprisingly, most of these are car-audio subs.

You could also fake the middle compartments: only make the facades look like they are usable. That would open up some more room

And for your health: use plywood, not MDF!

 

[antcollinet]

Just to add my voice to those above.

It's going to resonate like hell.

 

[Tell]

Thank you all for your replies! Firstly yes I'm fully aware that my project is a bit a compromise and not 100% perfectly hifi And secondly no I haven't really thought about the thin shell of the whole Kallax resonating, the only thing I really thought about was that I could maybe wedge the box with some tall 3D-printed wedges making that 16mm (or whatever I might pick in the end), getting +5mm from the wedge and then +3mm for the thickness of the inner part of the Kallax so I'd get around 24mm walls and less risk of the Kallax closest to the box to not resonate. But then of course the rest might do so instead so using some stuffing instead might be the better way?
I did do a quick test with my small Ino Audio piP lying on top of the Kallax playing some sines as louds as they could handle and I didn't hear any resonances at all from that, but then it's a bit of a air capacity differences between a 4" and a 10"..
But if I do build this and I do get serious resonance problems from the Kallax despite the wedging or stuffing I guess I could let go a bit of the WAF (she'll accept it) and place them next to the Kallax instead. Not maybe the optimal way of doing it all, but it might still be worth the experiment

About the port, I forgot to add a screenshot of that excel-document. You're saying this is completely wrong?

And thanks for the suggestions for other drivers. There are some that might be interesting, but most are either not easy to get here in Norway or they are just to expensive. But the SB Acoustics SB23MFCL45-4 and maaybe Dayton Audio RSS210HO-4 looks interesting even though I'd prefer not to go down to 8", but then again I might just have to considering the size of the box.

Was also considering going with a 12" sealed box, but haven't really looked in to that too much since I like doing stuff as efficiently as possible with what I got, and not sure how much amplifier I would need for that (got around 300 dirty wattage to play with atm). But maybe that would be the best way anyways?
And yes, will probably use plywood!

@voodooless Care to share any more about your Ikea-sub?

 

[voodooless]

About the port, I forgot to add a screenshot of that excel-document. You're saying this is completely wrong?

Maybe.. WinISD gives 25cm for a 6cm diameter port, and 9 cm gives 61 cm. So it seems here, it uses the lowest diameter for its calculation, which is probably wrong? If I (and I usually don't fully) trust ChatGPT, then the effective port diameter would be around 7.8 cm, making the needed port length around 45 cm.

As for my sub, it was built for a Besta TV enclosure, nicely hidden behind a door, downfiring. I used a 10" Wavecor woofer that I had lying around. I used a flared slot port to get the tuning done, also around 30 to 35 Hz. All in all, it worked pretty well. It goes really loud, obviously not super clean, given the enclosure it is in. I had to battle some resonances, and the box was so heavy that the Besta enclosure started to sag, mostly due to the hole I made in the underside . But it served me well for about one and a half years. Now, the enclosure is retired, so I'll need to find some other way to hide a sub

 

[digitalfrost]

Hmm it seems you are right if it's only 6cm the length should be okay.

If we compare the chassis, I think the RS210 is a good candidate, or the RSS265. Your solution lacks depth, and since the BR tuning is at 35hz you cannot boost below/at 35hz. -3dB is 42hz for RS255 in 25l.

All chassis lowpassed at 80hz with LR4.

 

[bmc0]

So it seems here, it uses the lowest diameter for its calculation, which is probably wrong?

It does not. See section 5 "Modeling flared ports and prediction of tuning" (page 9-12 of the PDF, numbered as page 30-33) of this paper.
I'd expect the actual tuning to be slightly lower than predicted due to the proximity to the side and bottom panels, but the effect should be small.

 

[Tell]

Maybe.. WinISD gives 25cm for a 6cm diameter port, and 9 cm gives 61 cm. So it seems here, it uses the lowest diameter for its calculation, which is probably wrong? If I (and I usually don't fully) trust ChatGPT, then the effective port diameter would be around 7.8 cm, making the needed port length around 45 cm.

As for my sub, it was built for a Besta TV enclosure, nicely hidden behind a door, downfiring. I used a 10" Wavecor woofer that I had lying around. I used a flared slot port to get the tuning done, also around 30 to 35 Hz. All in all, it worked pretty well. It goes really loud, obviously not super clean, given the enclosure it is in. I had to battle some resonances, and the box was so heavy that the Besta enclosure started to sag, mostly due to the hole I made in the underside . But it served me well for about one and a half years. Now, the enclosure is retired, so I'll need to find some other way to hide a sub

I think I trust it, both because of the paper and because of that 50 pages on diyaudio. What I don't fully trust is the small size that I'm aiming for, but I guess it's only at very high volumes that I might get problems, and combine that with the possible resonances in the Kallax I might not even be able to blast it as loud as I want to. But I guess that will be a lesson learned How id you battle those resonances btw?

Hmm it seems you are right if it's only 6cm the length should be okay.

View attachment 463175


If we compare the chassis, I think the RS210 is a good candidate, or the RSS265. Your solution lacks depth, and since the BR tuning is at 35hz you cannot boost below/at 35hz. -3dB is 42hz for RS255 in 25l.

All chassis lowpassed at 80hz with LR4.

Comparing it like that the DSC255 seems to be lacking quite a bit yes, but on paper it's quite a bit more efficient so feeding the 300w that my current amplifier can push it instead comes out ahead except at around 30Hz where it looses by a decibel. It's only if I'd get a much more powerful amplifier that I might be able to get a bit more of the smaller RSS210, or if I ported the RSS265 that would win by quite a margin, but I probably won't upgrade my amp in quite a while.
Or am I missing something?

 

[kemmler3D]

Given the possible rattling issue and concern over port noise, have you considered doing a dual opposed, sealed build instead?

 

[digitalfrost]

Eh it's still plenty deep and it's close to a wall anyway. You will probably have more problems with too much bass than to little

 

[Tell]

Given the possible rattling issue and concern over port noise, have you considered doing a dual opposed, sealed build instead?

No I haven't, but it feels like it's going to be a bit cramped with two of them in such a small box loosing lots of efficiency. You think the rattle will be so substantial that I would still benefit from it?
But also I prefer not to have to place the Kallax too far from the wall, I already have around 5cm because of a floorboard and some cables, but I could maybe maybe pull it another 5cm if needed, but then I could also place the port in the back which could help me accommodate a bigger one with less potential turbulence noise problems.

Eh it's still plenty deep and it's close to a wall anyway. You will probably have more problems with too much bass than to little

That's what I'm hoping for! ^^