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Hi All

 

Have already received some feedback suggesting the setup I'm considering wont be entirely crap, but in summary....

 

  • I'm wanting to add an additional sub into my theatre room however am stretch for suitable locations
  • I'm considering replacing one of the boxy arm rests on our modular couch with a custom box for a sub
  • The driver will however end up facing a wall with around 4 inch of clearance.

 

Open to any further comments on that...

 

 

My new question though....

 

I'm likely to go with a ported option, is there any issue with having the port to the front of the box whilst the driver is on the side? What would be the optimal location of the driver? Above the port or further away?

Untitled_jpg_3685de0e8cfd843510c2972dff5a0c9e.jpg

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The good thing about low bass is that there isn't much directivity. Port and driver direction shouldn't be important. Driver or port close to floor tends to add additional bass level.

Some subs are on short legs and fire downwards, I'd imagine that might work with some sofa designs.

I suspect the port shouldn't be as close to the driver as is shown in your drawing.

Two smaller drivers may help you keep to the armrest dimensions and proportions more easily (2 x 8" or 10"). You could have the driver/s on the rear panel and port at the front as you've shown.

Have a look at some online sub box designs for the driver you want to use, then squeeze the proportions to suit your armrest shape while keeping the internal volume and port volume the same.

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2 hours ago, Craggs2341 said:

Open to any further comments on that...

The gap will do this.

 

Change the air "loading" on the driver....  If you are designing the subwoofer in place.... ie. filtering it so it has a "flat" frequency reponse .... then you have accounted for this in your design.

 

Affect frequencies (make peaks and dips) where the dimensions of the gap become significant in relation to the wavelength of sound.    Becuase your gap is small then the affect is further outside the subwoofers pass band.    You might think a smaller gap wil be more of  a probem..... but it doesn't work like that.     Keep the subwoofer filtered to subwoofer frequencies (ie. <80Hz) and it will be fine.

 

Make the wall (and the couch) liable to vibration.   Make it sturdy, and be ready to appologise to people on the otherside of the wall.

2 hours ago, Craggs2341 said:

I'm likely to go with a ported option, is there any issue with having the port to the front of the box whilst the driver is on the side?

None.  In fact that's likely your only/best option.   You don't want the port facing into the wall or the couch, as it will affect the tuning of the port (Which you would need to account for in the design of the port/box tuning).

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1 hour ago, pwstereo said:

Driver or port close to floor tends to add additional bass level.

At true SW frequncies (<80Hz) touching the floor, or being 1m off the floor.... is the same, with respect to how many wavelengths they are away from the floor  (ie. close to zero).

 

1 hour ago, pwstereo said:

I suspect the port shouldn't be as close to the driver as is shown in your drawing.

The port will need to be quite large.... a lot larger than the picture indicates.... so it won't be able to be that tight with the driver.

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I'm pretty sure some of Australian manufacturers can build subwoofer whatever shape you need. 

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5 hours ago, Craggs2341 said:

I'm likely to go with a ported option, is there any issue with having the port to the front of the box whilst the driver is on the side? What would be the optimal location of the driver? Above the port or further away?

There are plenty of subbies on the market out there with down firing ports and the driver on the 'front' - which is the same as you're looking at. The only issue you will have is how to organise the port on the inside of the box. Have you thought of having the port be down firing and have 3-inch 'legs' on the new armrest for your couch?

 

Now, if you're going to be replacing the arm with a box the same size, you're going to be designing the subwoofer backwards. So you'll be attempting to locate a woofer that can be used in a specific box volume (and port volume is included in this). But, if you're going to allow your new 'arm' to be a little wider, then you will probably have no major issues and would be able to purchase based on the approximate sizing given by the manufacturer.

 

And as you will have a fair amount of area on the side of the armrest, you could probably go with a pair of woofers rather than just one. And where are you going to locate the amp? On the 'back' of the armrest would probably be most suitable...

 

Also, you said 'additional sub', what is/are your current sub arrangements? would you want this one to beef up the bottom octave (15-30Hz) or more of the range (up to 80Hz)? This could offor some other options in designing.

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Dayton Audio RSS315HFA-8 12" Reference HF Subwoofer 8 Ohm might be the puppy you're looking for. It says (on the Loudspeakerkit website) that it can produce f3 of 20Hz in a 50 litre ported box. I'm assuming that's 50 litres PLUS the port. And the driver is less than 8 inches (or 20cm) deep.

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If you havnt got a subwoofer design building site here is one https://www.subwoofer-builder.com/WinISD.htm which has a data base of hundreds of woofer makes and models to simulate and build a cabinet to suit your space.

 

The cabinet shape you have could also be made into a transmission line subwoofer with great affect, woofer face out, slot port forward or upwards. Try for example, a suitable 8-10 inch woofer, create a multi folded tube behind it equal to the surface area of the woofer come or tapering towards the slot port outlet. Experiment with a test box or don’t glue it until sounds right.

 

http://www.mh-audio.nl/Calculators/TML.html

 

https://www.diysubwoofers.org/tls/

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Thanks for the input all

 

FYI my existing sub is a 12 inch Dayton Ultimax with a 1000D amp, I was looking at getting the same driver and a new amp, likely the 3000D. 

 

I'll do some more reading regarding two smaller units

 

Also see below arm rest I was looking to replace

 

Ignore the mess :)

20200705_191931.jpg

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8 hours ago, Craggs2341 said:

Also see below arm rest I was looking to replace

With that armrest position I would suggest a front facing port. Front or down firing driver.

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