Large ported subwoofer

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sploo

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I've built many loudspeakers and subs over the years, but I've never made a ported/vented sub. I had a load of old white melamine IKEA kitchen doors which seemed ideal for my desire to be cheap and stingy...

A quick mock up of the rough design in Sketchup. Dimensions were dictated by the available board sizes, but the design is approx 113 litres of internal space, using a 100mm diameter port and a 12" SB Acoustics SB34NRX75-6 sub driver:

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I knocked up a circle cutting jig:

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And cut the holes and rebates for the driver and port:

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Test fit:

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The front baffle is a double skin of the door material, and this also shows the start of the port tube:

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Then it was a job of hacking together internal bracing from what material I had to hand. All bracing deliberately off center to help reduce vibrations:

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Sound deadening and reflection absorbing sheets are expensive. Reclaimed carpet tiles are definitely just as good (honest):

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After many, many (too many) test fits, it was finally time to commit to gluing it all together:

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The port tube would need some support, so a two piece bracket was made, which will grip the inside end. The design allows removal of the port tube:

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I couldn't find suitably sized black pipe, so the inside was sprayed using plastic paint (the "dust" on the outside is just paint overspray):

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Port fitting detail:

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Wiring. As you can see, I used the purest form of stranded cable, made of £1000/m unobtainium, and sheathed in mouse p*nis leather:

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Fitting the base:

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And done:

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novocaine

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horrible and completely pointless, everyone knows you can get great sound from a 1/2" speaker in the back of every phone today.

:)

welldone, good use for kitchen doors, mine are being made in to jigs.
 

sploo

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horrible and completely pointless, everyone knows you can get great sound from a 1/2" speaker in the back of every phone today.
I tried to get my phone speaker driver to produce 105dB at 25Hz and the excursion means it's currently somewhere south of France. It's due to swing back somewhere near Iceland as it follows the sine wave 😁

PS Did you notice that the router circle jig is made from the same kitchen door material ;)
 

novocaine

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oh spotted it. I was somewhat intrigued by the bearings to keep the router facing the same way no matter it's orientation. nice idea.

wondered what the tinny trump sound was early, must have been your phone passing overhead.
 

disco_monkey79

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Very nice - how does it sound?

Interesting re the deliberately off-centre bracing - that wouldn't have occurred to me.
 

sploo

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oh spotted it. I was somewhat intrigued by the bearings to keep the router facing the same way no matter it's orientation. nice idea.

wondered what the tinny trump sound was early, must have been your phone passing overhead.
Yea, that router was used as a spindle in my CNC machine for the last ~15 years but I finally got round to getting a proper one; hence it became free. It occurred to me that the base is completely circular so it'd be possible to make a circle cutting jig that wouldn't require the router to spin round and tangle the cable. Seemed to work pretty well.

Phone's just passed over :)
 

sploo

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Very nice - how does it sound?

Interesting re the deliberately off-centre bracing - that wouldn't have occurred to me.
Sound is pretty good. It's currently paired with a couple of small monitors which perhaps isn't ideal (the 100-200Hz region isn't most suited to either speakers or sub), plus the cheap 2.1 amp I'm using has a lowpass filter for the sub channel, but no highpass for the speakers; such that it's still trying to send the low bass to the monitors (which somewhat defeats the point of reducing distortion on the small speaker midbass).

With the amp's bass control turned down though it's producing cleaner midbass + treble from the monitors, and giving me decent (and tuneful) bass with the sub.

Off-center bracing; if you brace in the center of a panel then you turn that one panel (that resonates at frequency f) into two panels that both resonate at frequency 2f; so by making the unsupported section unequal you spread the unwanted resonances across a larger range of frequencies (a bit at several frequencies being less audible than a lot at one).
 

Inspector

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You know way more about sound than I and are willing to do much more than I to get it.

Another use for those speaker ports. The 100mm and 150mm diameter ones are the best shape for dust collection hoods. They can be used "naked" like beside your bowl when sanding at the lathe or when cut to fit flush in a table saw or router cabinet improve the airflow into the duct. Better than a bare hose or a cone.

Pete
 

dannyr

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I was thinking of something similar - but connected to a stereo amp with no separate low freq channel - I know a bit about inductance, capacitance for frequency division, but does anyone have an easy wiring/electronics answer (I'm at least as stingy as sploo, so no exotics, but a ready-made would be OK) - I have the box, which would take either one low bass for both channels, or maybe easier two low bass speakers, separating the channels).
 

DBT85

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Very nice. Want to build myself something but was dreaming in the direction of a cabinet with dual 15s in it or something.

Not knowing the first thing about what to buy it's quite hard as the nerds that usually seem to build this stuff only want to spec super high end gear and would spend more on one sub than I would on a receiver.

I note that you aren't using 10000v solid core audio string. Nor are you using speaker cable stands. I mean why even bother?
 
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AFFF

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Nice work but surely chipboard is not the ideal material for this? Take a look at this YouTube link ....
 

sploo

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I was thinking of something similar - but connected to a stereo amp with no separate low freq channel - I know a bit about inductance, capacitance for frequency division, but does anyone have an easy wiring/electronics answer (I'm at least as stingy as sploo, so no exotics, but a ready-made would be OK) - I have the box, which would take either one low bass for both channels, or maybe easier two low bass speakers, separating the channels).
Do you mean making a pair of loudspeakers (treble + at least one lower frequency driver in the same cabinet) or a sub?
 

sploo

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Very nice. Want to build myself something but was dreaming in the direction of a cabinet with dual 15s in it or something.

Not knowing the first thing about what to buy it's quite hard as the nerds that usually seem to build this stuff only want to spec super high end gear and would spend more on one sub than I would on a receiver.

I note that you aren't using 10000v solid core audio string. Nor are you using speaker cable stands. I mean why even bother?
Have a search around for DIY designs; though subs are "easier" in that the front baffle dimensions aren't critical (unlike a loudspeaker) and it's generally a case of just making sure the internal volume is suitable for the driver being used (it's acting as an air spring). If you port/vent or use a passive radiator then the design does get a bit more complicated, but a cabinet with two 15" drivers would likely produce enough low frequency energy to rattle your fillings; even without a port.

By the time you get to 15" you're more in the realm of PA audio than home audio drivers; though often they can be cheaper - but I don't know much about the PA market. SB Acoustics do the 15" SB42FHCL75-6 (seems to retail around £400). I couldn't immediately spot anything that large from Scan Speak, and their 13" 32W/4878T00 is over £500.
 

sploo

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Nice work but surely chipboard is not the ideal material for this? Take a look at this YouTube link ....

It's ideal when you have a lot of it ;)

Like anything in home audio there's tons of beard stroking and argument about the "best" cabinet material, but (sensible) consensus is generally something dense and homogeneous - i.e. MDF. Chipboard products can have voids or loose particles that can rattle (so obviously not ideal). Solid timber moves with moisture changes so is generally not a good idea (though I have built speakers that way too).
 

DBT85

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Have a search around for DIY designs; though subs are "easier" in that the front baffle dimensions aren't critical (unlike a loudspeaker) and it's generally a case of just making sure the internal volume is suitable for the driver being used (it's acting as an air spring). If you port/vent or use a passive radiator then the design does get a bit more complicated, but a cabinet with two 15" drivers would likely produce enough low frequency energy to rattle your fillings; even without a port.

By the time you get to 15" you're more in the realm of PA audio than home audio drivers; though often they can be cheaper - but I don't know much about the PA market. SB Acoustics do the 15" SB42FHCL75-6 (seems to retail around £400). I couldn't immediately spot anything that large from Scan Speak, and their 13" 32W/4878T00 is over £500.
Bowel loosening when the trex in jurassic Park stomps around sounds perfect 😂.

But yeah. I'm not dropping that kind of money to build a sub. My pitiful 20 year old Sony 5.1 in a box sub (I think the case says 30w?!) is working for now.

I agree with the beard stroking. So many seem to worry more about ha ING the perfect unit rather than just having A unit that in their environment and setting and with their ears isn't going to be "perfect" anyway. If you'd built that from mdf do you think you'd have noticed any actual difference?

Maybe I'll revise by ideas down a bit. Though I think my plan was to go sealed rather than ported. My TV is on the wall with the nice Kef flat speakers around it, I had hoped to essentially make what would look to anyone like a TV unit with downward facing drivers. Naturally it would be useless to actually stand anything on as it would all rattle off!
 

dannyr

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Do you mean making a pair of loudspeakers (treble + at least one lower frequency driver in the same cabinet) or a sub?

I have the mid/high range taken care of by "sold as full range but pretty small" speakers I gave a cosmetic boost to and put on mahogany stands and I have a very stylish old hollow mahogany fluted column I'd turn (sideways) into a bass channel speaker or two as a tweak. Back in my hi-fi days I made full range speakers reasonably successfully with a off the shelf 3 way crossovers and am reasonably happy with options for porting or not, so any suggestions -- simple and cheap.
 

sploo

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Bowel loosening when the trex in jurassic Park stomps around sounds perfect 😂.

But yeah. I'm not dropping that kind of money to build a sub. My pitiful 20 year old Sony 5.1 in a box sub (I think the case says 30w?!) is working for now.

I agree with the beard stroking. So many seem to worry more about ha ING the perfect unit rather than just having A unit that in their environment and setting and with their ears isn't going to be "perfect" anyway. If you'd built that from mdf do you think you'd have noticed any actual difference?

Maybe I'll revise by ideas down a bit. Though I think my plan was to go sealed rather than ported. My TV is on the wall with the nice Kef flat speakers around it, I had hoped to essentially make what would look to anyone like a TV unit with downward facing drivers. Naturally it would be useless to actually stand anything on as it would all rattle off!
If you have two drivers and can put them on opposing sides then the movement of the drivers will cancel one another out. I've got a pair of sub cabinets, each with two 10" Peerless XLS drivers (front and rear face) and you can put a glass of water on top with no risk.

Sealed is definitely easier than ported - plus you generally only require a smaller cabinet.

Larger drivers tend to be more efficient, and the little 2.1 amp that's powering the 12" ported sub is only capable of around 30W (given the PSU I'm using and the impedance of the driver). It'll play louder than I'd want for comfortable listening.
 

sploo

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I have the mid/high range taken care of by "sold as full range but pretty small" speakers I gave a cosmetic boost to and put on mahogany stands and I have a very stylish old hollow mahogany fluted column I'd turn (sideways) into a bass channel speaker or two as a tweak. Back in my hi-fi days I made full range speakers reasonably successfully with a off the shelf 3 way crossovers and am reasonably happy with options for porting or not, so any suggestions -- simple and cheap.
What are the dimensions of the column? Obviously there's no point in recommending a 12" driver if the diameter is only 10" ;)

If the internal volume is small then a car audio sub might work, as they seem to be designed for tight enclosures (at the expense of being fairly inefficient).
 

dannyr

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What are the dimensions of the column? Obviously there's no point in recommending a 12" driver if the diameter is only 10" ;)

If the internal volume is small then a car audio sub might work, as they seem to be designed for tight enclosures (at the expense of being fairly inefficient).

Thanks for quick response ------ About 8ins - I have some poss longish throw drivers already, my Q was rather about the frequency splitting options given a standard 2 channel stereo output.
 
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