Wanting to build 2 small subwoofers to go on either side of my fireplace - advice appreciated

[Pygmy]

I have a big drop down projector screen that drops in front of the fireplace.
Next to the fireplace - left and right - are two bookcases, BUT there's a 21cm space between the fireplace and those.
So - I have on both sides a spot of 21cm wide, 48cm high, 30cm deep that's not actively being used / could be used by a nice project..

I'd like to fill these 2 spaces with small subwoofers.
The width limitation means 8" drivers...

So - what's the best I can do within these limits - 21x48x30cm, with the driver on the 21cm side..?
What are the best 8" subwoofer driver options, and what can I do with them?

 

[Wolf]

Unfortunately, most 8" woofers are 21cm+ in diameter, so getting an 8" to fit gets rather difficult. A good 7" would likely work, like the new Dayton Epique E180HE44 woofers or the Dayton DCS165. The Tang Band 1139 also has street cred in this area.

 

[DVDdoug]

You can use software such as WinISD to predict & optimize performance. You can enter the Thiele-Small parameters before choosing & buying a driver and you can model sealed & ported designs.

Of course with limited width you can get more piston area with multiple drivers.

 

[Midnight Audiophile]

A design with four 4” drivers similar to the Dayton Audio MKSX4 may work. It’s close to fitting your space as it is at 15 x 35.5 x 40.6 cm.

Home

Dayton Audio MKSX4 Four 4" Driver Low Profile Passive SubwooferDayton Audio MKSX4 Low Profile SubwooferThe MK Series of home speakers from Dayton Audio are the best way to add rich sound with elegance and sophistication. Built to last, the MK series makes it easy to listen to for hours and hours...

www.parts-express.com

 

[Wolf]

How silly of me, there are more...
Anarchy6
Peerless SLS 830946

More?

 

[AwesomeSauce2015]

Side firing is the answer.
You can get a shallow-mount 10 or 12" sub like these: https://www.parts-express.com/Dayton-Audio-LS12-44-12-Low-Profile-Subwoofer-Dual-4-Ohm-295-253
(Other options exist, but the Daytons are pretty good value.)
Mount them so that they're side firing and build a tall & narrow ported enclosure for them. IDK if 2 opposed drivers/side would work, but you may want to consider it for the piston surface area.
Add a DSP amp and you'll hopefully be set.

 

[Holmz]

Do you use that fireplace @Pygmy ?

They are not known to be great for sonics, but could be a goose to stuff in some absorber.
(Maybe removing it on MXAS eve.)
However that stack of wood suggests that it is used.

A speaker right in front it is not likely ideal and if it is rear ported then maybe try and move it?


What is behind the door under the TV and under the books on the right side?
If you could use some of that volume it looks like it could be an optional place??

 

[alex-z]

Work backwards from your displacement limit.

21x48x30cm results in 19.89 litres of internal air volume, if using 19mm aka 3/4" MDF. Assume you will lose about 1 litre to driver displacement + internal bracing.

The Dayton E180HE-44 works pretty well in that displacement, using a 30Hz port tune. If you use a 20Hz high-pass filter, you can give each driver about 70 watts, have -3dB at 32Hz, and -10dB at 24Hz.

Although something like a side firing 10" offers a lot more value per dollar.

A Dayton Ultimax 10" could be used with a Linkwitz Transform filter to place -3dB at 30Hz, and -10dB at 20Hz. More importantly, using a 20Hz high-pass, each driver can handle 300 watts, allowing for a 11.5dB more SPL at 20Hz than the E180HE-44, and roughly 5dB more at 30Hz.

UM10 has a surround to motor depth of 178mm, so it should just barely fit in your 21cm width requirement, including the surround height and cabinet walls.

 

[fineMen]

SB Acoustics has a race track shaped driver that might fit. It is powerful, people say, and not that expensive. In the possible enclosure given, that "chuffing" from a realizable port may become a primary concern.

 

[FrantzM]

Hi

Rather than going for a really suboptimal , subwoofer with smallish drivers.. why not find a good carpenter or try to modify the boocases and drop a subwoofer in each. You could cut the bottom so that the subwoofers are on the floor and minimizing the vibrations of the bookcases themselves, reducing buzzes and creeks and other nastiness, and use louvered doors or something acoustically transparent for doors on the bookcases...
A picture to make more sense:

To illustrate the kind of door you would need... Cut the bottom of the bookcase to the dimensions of the (much better subs) drop them and enclose them.. Serious bass and invisibility... Of course after DSP, EQ and the other stuffs

Peace

 

[Maciek]

Side firing Peerless XLS 10" with passive radiator tuned to mid 20s. With room gain it will work like a charm down to as low as You like. Mine works in a cab 22,5 cm wide, around 18-19l. I think it would still work trimmed to 21 cm.

 

[Pygmy]

Thank you all for your ideas!

I'll go over some of them:

- a side firing woofer might indeed be better than using 6.5" or 8" woofers in the 21cm front - but it'll be side-firing directly into either the bookcase or the fireplace, that doesn't seem right..?
- yes, we use the fireplace
- I've built the bookcases myself and no, my beter half will not allow me to install subs in the lower cabinets

That said I've forgotten to mention some things that might or might not be relevant:
- yes I'm fiddling about with WinISD and different drivers to see what I can come up with
- I have a Umik1 and experience measuring rooms with REW
- I'm using a NAD receiver with Dirac Live (and again, measurements)

Random thought:
- has anybody ever built a subwoofer in the bottom of a fireplace? Heat shielding the sub might be difficult but sending sub-waves through the flames might be awesome

 

[sarumbear]

I have a big drop down projector screen that drops in front of the fireplace.
Next to the fireplace - left and right - are two bookcases, BUT there's a 21cm space between the fireplace and those.
So - I have on both sides a spot of 21cm wide, 48cm high, 30cm deep that's not actively being used / could be used by a nice project..

I'd like to fill these 2 spaces with small subwoofers.
The width limitation means 8" drivers...

So - what's the best I can do within these limits - 21x48x30cm, with the driver on the 21cm side..?
What are the best 8" subwoofer driver options, and what can I do with them?
View attachment 239067

You can mount the driver(s) on the side of the enclosure and use larger drivers. Like KEF does with the Blades.

 

[Pygmy]

You can mount the driver(s) on the side of the enclosure and use larger drivers. Like KEF does with the Blades.

Yes other people mentioned that as well, my only problem with that is that the woofer will then be firing straight into either my bookcase or the wall of the fireplace :-/

 

[sarumbear]

Yes other people mentioned that as well, my only problem with that is that the woofer will then be firing straight into either my bookcase or the wall of the fireplace :-/

If you use a shallow subwoofer driver you don’t need an enclosure as wide as the entire width of the slot. If you place the ports on the front, the pressure in front of the driver will be small.

Your other option is to use multiple (4 or more) 8” drivers along the narrow front facing side but finding drivers in that diameter with large Xmax is difficult. I think a single shallow 12” or two 10” drivers should be better suited to the job.

 

[Pygmy]

Just thinking out loud here - an SB Acoustics 10" shallow driver has a depth of about 9cm so that would fit - when using 18mm mdf or plywood there's 17.4mm of inside space available so a driver like that would only take half space... meaning I could make the cabinet less than 21cm wide, and add those centimeters to the free air between the cabinet and the bookcase/fireplace..

 

[jomo]

Thank you all for your ideas!

I'll go over some of them:

- a side firing woofer might indeed be better than using 6.5" or 8" woofers in the 21cm front - but it'll be side-firing directly into either the bookcase or the fireplace, that doesn't seem right..?
- yes, we use the fireplace
- I've built the bookcases myself and no, my beter half will not allow me to install subs in the lower cabinets

That said I've forgotten to mention some things that might or might not be relevant:
- yes I'm fiddling about with WinISD and different drivers to see what I can come up with
- I have a Umik1 and experience measuring rooms with REW
- I'm using a NAD receiver with Dirac Live (and again, measurements)

Random thought:
- has anybody ever built a subwoofer in the bottom of a fireplace? Heat shielding the sub might be difficult but sending sub-waves through the flames might be awesome

I would talk to Rythmik. They used to sell their 8" servo woofer in a kit for custom installs. They no longer selll the kit, but I think you can piece it together with separate drivers and associated plate amp. They would be a good source for what's possible. BTW, their 8" servo woofers in a sealed enclosure go down to 20 Hz (-3 dB) when used with their complimentary amps

Rythmik Audio servo subwoofer 8" FM8

 

[Duke]

my only problem with that is that the woofer will then be firing straight into either my bookcase or the wall of the fireplace :-/

As long as there is adequate clearance so that the surround doesn't tap the bookcase, you should be fine. I'd face the woofer away from the fireplace to keep if far from the heat.

Air in that tight space between woofer and bookcase would slightly increase the effective moving mass by more closely coupling to the woofer cone. The effect would be a slight increase in the effective moving mass and therefore a slight reduction in the in-box resonant frequency of the woofer. Assuming the woofer has a fairly heavy cone, the audible effect may fall somewhere between very small and negligible. Anyway whatever effect there is will be in a beneficial direction, as far as bottom-end extension goes.

 

[Keith Conroy]

I have a big drop down projector screen that drops in front of the fireplace.
Next to the fireplace - left and right - are two bookcases, BUT there's a 21cm space between the fireplace and those.
So - I have on both sides a spot of 21cm wide, 48cm high, 30cm deep that's not actively being used / could be used by a nice project..

I'd like to fill these 2 spaces with small subwoofers.
The width limitation means 8" drivers...

So - what's the best I can do within these limits - 21x48x30cm, with the driver on the 21cm side..?
What are the best 8" subwoofer driver options, and what can I do with them?
View attachment 239067

Maybe I missed it? Its important to know what your using for main speakers?

 

[sarumbear]

Maybe I missed it? Its important to know what your using for main speakers?

Why?