DIY Tube subwoofers.

drivinscool · 03-07-2007, 1:39 PM

Hi, I'm just about to start my second subwoofer project.
I'd like to try a tube this time.
I've found a supplier of cardboard/particle board tubes but I'm not sure what to order.

Is there a minimun wall thickness required for a tube of 450mm diametre?
Also is internal bracing needed with a tube?

My plan is to build a pair of 450mm tubes 750mm in length, each with a pair of 65mm pvc ports and a single 12" Monolith driver.

Driver specs are here http://www.bkelec.com/HiFi/drive_uni...onolith_du.htm

Rich.

asdonk · 03-07-2007, 3:28 PM

looks like a monolith in a svs cylinder

**IronGiant** · 03-07-2007, 3:54 PM

My DIY tube (built by Mat-d-Rat) is ~530mm in diameter and if memory serves the cardboard is somewhere between 10 and 15mm thick. It has no internal bracing.

Dave

Nimby · 03-07-2007, 5:53 PM

750mm counts as knee-high in SVS terms.

30", 39" & 46" tall in this diameter.

Volume counts for a lot in subwoofers.

What are the thicknesses available from your source in 450mm diameter?

The SVS tube is quite thin but claims a polyester resin adhesive, I believe.

drivinscool · 03-07-2007, 6:18 PM

Quote:

Originally Posted by Nimby

750mm counts as knee-high in SVS terms.

30", 39" & 46" tall in this diameter.

Volume counts for a lot in subwoofers.

What are the thicknesses available from your source in 450mm diameter?

The SVS tube is quite thin but claims a polyester resin adhesive, I believe.

I'm aiming for a pair of 100 litre enclosures.
The tube comes standard as only 6mm thick, they can make any thickness to order (but it costs 3x the amount).

Would 6mm with internal bracing in the form of a few full diameter MDF circles with holes cut in be sufficient? It's going to be ported anyway so internal pressure won't be that high.

I'm still in corespondance with the supplier asking questions, I've just asked about regidity and if it deforms when sat/stood on.

Nimby · 03-07-2007, 6:56 PM

A ported subwoofer is not subject to high internal air pressures so I think you can relax about 6mm. It will be far heavier than an SVS tube which uses a much more powerful driver than you intend to use.

Don't forget that the end caps of a sub add considerable radial stiffness too.

Use WinISD to find the optimum enclosure volume for a particular driver rather than fix your design on some chosen volume.

Don't be too persistent about tube specs with a manufacturer if you are only ordering small quantities. Answering questions costs money and may put them off dealing with small purchasers in future. Your questions may be completely meaningless to them anyway given the small likelihood of others building subwoofers with their tubes.

Russell.Williams · 03-07-2007, 7:32 PM

Quote:

Originally Posted by Nimby

750mm counts as knee-high in SVS terms.

30", 39" & 46" tall in this diameter.

Not wishing to seem a pedant. Bugger it! Being a pedant, 750mm is 30", give or take 11mm.

Russell

Nimby · 03-07-2007, 7:48 PM

I held up a tape measure to my adult-sized 16-46.

750mm comes about halfway up, or down. (if you want to be technical)

drivinscool · 03-07-2007, 8:42 PM

I think 75x45cm (100 L) is big enough for my room, don't forget I'm building a pair of these!
The BK Monolith is only 95L.

drivinscool · 03-07-2007, 8:50 PM

Quote:

Originally Posted by Nimby

I held up a tape measure to my adult-sized 16-46.

750mm comes about halfway up, or down. (if you want to be technical)

Your sub is 16"x46"?

Assuming thats the internal dimensions and not the overall height/width that still only equates to 137 L(without taking into account port displacment) so bigger but not that much bigger.

Nimby · 03-07-2007, 9:36 PM

Quite right.

With slightly over 40cm Dia x 110cm active I'd put it somewhere around 138 liters minus the bits and bobs inside.

It is tuned to 16Hz.

Russell.Williams · 03-07-2007, 9:52 PM

I'm sort of getting interested in tube subwoofers.

They seem to be too easy and too cheap to make to be ignored. Whilst surfing I came across this crowd.

I work in construction (I'm a materials buyer) and have come across numerous column formers. I'd ignored that company because we're using polystyrene cored materials that are even easier to use in our sphere of expertise. They'd be crap for subwoofer use however - too light. I mean, I can push my finger through it.

I'm just wondering what sort of costs drivinscool (only if you don't do 36000 a year) is talking about? I could be tempted into further investigation via numerous suppliers.

Russell

Russell.Williams · 03-07-2007, 9:55 PM

Quote:

Originally Posted by drivinscool

I think 75x45cm (100 L) is big enough for my room, don't forget I'm building a pair of these!
The BK Monolith is only 95L.

Don't underestimate that volume. Two sub tests have shown that that volume, with the right port tuning, offers near sealed sub levels of impulse response and group delay. There is a good reason why the Monolith is that big and not slightly bigger or smaller.

Russell

drivinscool · 03-07-2007, 10:25 PM

Quote:

Originally Posted by russ.will

I'm sort of getting interested in tube subwoofers.

They seem to be too easy and too cheap to make to be ignored. Whilst surfing I came across this crowd.

I work in construction (I'm a materials buyer) and have come across numerous column formers. I'd ignored that company because we're using polystyrene cored materials that are even easier to use in our sphere of expertise. They'd be crap for subwoofer use however - too light. I mean, I can push my finger through it.

I'm just wondering what sort of costs drivinscool (only if you don't do 36000 a year) is talking about? I could be tempted into further investigation via numerous suppliers.

Russell

That's where I'm getting my tube from, £50 delivered for 6mm x 1500mm x 450mm.

drivinscool · 03-07-2007, 10:27 PM

Quote:

Originally Posted by russ.will

Don't underestimate that volume. Two sub tests have shown that that volume, with the right port tuning, offers near sealed sub levels of impulse response and group delay. There is a good reason why the Monolith is that big and not slightly bigger or smaller.

Russell

Thanks Russ, i'll keep that in mind

Russell.Williams · 03-07-2007, 10:56 PM

Quote:

Originally Posted by drivinscool

That's where I'm getting my tube from, £50 delivered for 6mm x 1500mm x 450mm.

It's that cheap!

What are you going to power it with? The Behringer Europower 1500 would seem a cost effective unit for these drivers.

Russell

bilba · 04-07-2007, 12:49 AM

To make your design job a bit easier, grab yourself a copy of sonosub.exe

It's something I whipped up for the boys in the US, where sonotube based subs are quite popular.

And yes, you can work in inches, cm or mm

drivinscool · 04-07-2007, 7:01 AM

Thanks for the replies,

Russ, I'll be stripping my existing DIY sub of its BK components. MF300 amp module and ASBF bass controler. The 300w (4ohms)module is rated at 220w at 8ohms so each of my 4ohm subs will get 110 each until I can afford another unit or get a 1000w plate amp.

Bilba, thanks I'll give it a go. I use winISD pro at the moment which is good but it's worth a play.

Nimby · 04-07-2007, 9:50 AM

An excellent resource, bilba! Thanks.

drivinscool · 04-07-2007, 5:11 PM

Quote:

Originally Posted by russ.will

It's that cheap!

What are you going to power it with? The Behringer Europower 1500 would seem a cost effective unit for these drivers.

Russell

£50 + vat.
£58.75, still very good value. MDF would cost maybe £35-40 for boxes of similer size but a lot less work is needed with the tube.

Nimby · 04-07-2007, 5:38 PM

Downside with Behringer EP1500 & EP2500 amps is the cooling fan noise.
A simple swap for a quieter fan but you need to find a 24Volt fan.
Same size as a computer case fan at 80mm x 25mm but very few computer shops stock 24Volt fans.
I ended up going to the Papst importer after an exhaustive search of all the computer shops.

drivinscool · 04-07-2007, 5:52 PM

Quote:

Originally Posted by Nimby

Downside with Behringer EP1500 & EP2500 amps is the cooling fan noise.
A simple swap for a quieter fan but you need to find a 24Volt fan.
Same size as a computer case fan at 80mm x 25mm but very few computer shops stock 24Volt fans.
I ended up going to the Papst importer after an exhaustive search of all the computer shops.

I looked at that but noticed the Dimension 3 Numark Dimension3 Power Amp looked quite nice and has the crossovers i need.
Any reports on this product?

Nimby · 04-07-2007, 6:28 PM

I'm afraid I know nothing of Numark.

Behringer may not be the finest quality on earth but they have a good reputation for reliability with AV fans (worldwide). They easily match the requirements for subwoofer duties in an HT.

Judging from experienced posters on other forums it is pointless to save a few pounds if the product is of unknown quality. Behringer is well known.

eviljohn2 · 04-07-2007, 6:41 PM

Out of interest Nimby, did you consider 2 12V fans in series or a 12V fan with a suitable loading resistor?

Nimby · 04-07-2007, 7:14 PM

Quote:

Originally Posted by eviljohn2

Out of interest Nimby, did you consider 2 12V fans in series or a 12V fan with a suitable loading resistor?

I've seen twin fans suggested online but nobody has posted about actually trying it to my knowledge. It may have the same weakness as the series resistor:

A series resistor doesn't work reliably.- It tends to stall the motor or cause it not to start on switch on. Which must obviously be avoided at all costs!

A low noise fan is by far the best option in HT subwoofer use.

For the demands of band and PA use the original fan should not be changed.

If the amp can be housed in a cupboard or another room then the rushing noise is no longer a problem.

drivinscool · 10-07-2007, 8:43 PM

OK so my tube arrived today and i've started routing out the circular MDF pieces for internal bracing and end caps.

Should I go the SVS route and mount the port on the opposing baffle or next to the driver on the main baffle, will this have any effect on the sound?

I'm just a little concerned that my 3 year old will fill the sub with power rangers figures if he can get to the opening

Also on SVS sube there is what looks like a separate circle of MDF a few inches away from the driver, is this essential as I haven't seen such a thing on normal DF subs, is the clearance critical?

Rich.

**IronGiant** · 11-07-2007, 12:39 AM

This may help:

http://matthew.augier.info/index.php...e=PICT3266.jpg

Keep clicking on the next picture, bottom left of the screen.

All down firing subs hit against the floor, I don't think it matters how far within an inch or so

drivinscool · 14-07-2007, 11:05 AM

Quote:

Originally Posted by IronGiant

This may help:

http://matthew.augier.info/index.php...e=PICT3266.jpg

Keep clicking on the next picture, bottom left of the screen.

All down firing subs hit against the floor, I don't think it matters how far within an inch or so

Thanks,

I'll add the extra MDF base, it must reflect the sound better than the carpet and some extra weight can't do any harm as these tubes are pretty light compared to my last MDF box.

goatywoaty · 19-07-2007, 3:33 PM

Hiya Drivinscool,

How you getting along with your sub? Very interested as if I can get some money together for it, I might be interested in doing something simmilar, two tube type subwoofers attatched together that use 2 x monolith drivers and a 500watt BK amp...