DIY Movie Sub

[Macca]

I have a professionally built Acousta cabinet (about the size of a fridge) that has been cut out to take a 12'' Bass driver.

I was thinking of installing an an appropriate bass driver with a simple crossover of one hard wired inductor to restrict upper out put to about 50hz after which rolling off steeply. I'd use a Behringer A500 bridged to power the sub as it has adjustable gain.

Is this any way realistic and if so what would be a suitable driver? I'd want useful bass down to 20hz

[Techno Commander]

Volt RV3143 (http://www.wilmslow-audio.co.uk/rv3143-radial-488-p.asp)

[Macca]

Volt RV3143 (http://www.wilmslow-audio.co.uk/rv3143-radial-488-p.asp)

Thanks Andy - if I was building hi-fi speakers that would be my first choice but £300 with VAT is a bit much - this is for movie bass only. I just need to move a bit of air at VFL:)

[Ali Tait]

Can you cut it out for a 15 incher? Eminence Alpha can be had for about 50 squids.

[Ali Tait]

Or this would slot straight in-

http://cgi.ebay.co.uk/Eminence-Alpha-12-150W-12-Bass-Mid-Range-Speaker-/130471907820?pt=UK_ConElec_SpeakersPASystems_RL&hash=item1e60bb51ec

[Techno Commander]

I would choose this as a cheaper alternative. (http://cgi.ebay.co.uk/Eminence-LAB-12-400W-800W-12-6-Ohm-Subwoofer-Driver-/120667472627?pt=UK_AudioVideoElectronics_HomeAudio HiFi_HiFiSpeakers&hash=item1c185782f3)

[Reid Malenfant]

The Lab 12 would be ideal imo. Low resonance & a decently low total Q long stroke voicecoil, stuff it in a 4 or 5 cubic foot enclosure tuned to 20Hz & you'll know all about bass. It'd actually make a very decent hifi sub with it's characteristics :)

[Reid Malenfant]

The Lab 12 would be ideal imo. Low resonance & a decently low total Q long stroke voicecoil, stuff it in a 4 or 5 cubic foot enclosure tuned to 20Hz & you'll know all about bass. It'd actually make a very decent hifi sub with it's characteristics :)
I just modelled it & i was pretty damn close tbh :eyebrows:

A 140L enclosure tuned to 21.5Hz will give you -3Db @ 20Hz @ 110Db :eek: You'd need a 400W amp to get that though. Maximum output would be 113Db..

You'd need 2 x 4" diameter ports & each would need to be 68CM long, the reason you need two is to reduce air velocity in the ports to keep turbulence to a minimum. Obviously you'd need to add extra volume to the enclosure to account for the volume taken up by the ports themselves.

If you decide to do it go to your nearest carpet warehouse & grab one of the cardboard carpet rolls once it's been disposed of ;)

It'd make a hell of a sub :eyebrows:

[Techno Commander]

You'd need 2 x 4" diameter ports & each would need to be 68CM long

You could mount them coming out the top like chimneys?:lol:

[Reid Malenfant]

You could mount them coming out the top like chimneys?:lol:
True, i have thought about this in the past when extremely long ports are needed.. At the end of the day though even i couldn't live with that & i'm single ffs :D

[Macca]

Thanks for the suggestions - I'll review the bass drivers tomorrow in the sober light of day and see what I will go for.

Mark I think enthusiasm has got the better of you - you forgot I am using an existing cab so the chimney ports are not going to happen -this time...:eyebrows:

[Reid Malenfant]

Hey i didn't suggest it :lol:

What you really need to do is find out the internal enclosure volume. Once you know that then look for a driver that'll give you the best performance with what you have.

Never buy a driver & then work out what enclosure it needs as it often ends in tears :eyebrows:

[Macca]

Mark

It's been a long time since I last designed and built speakers...what I did back then was to buy the bass-mid drivers and use the Thiel-Small parameters to work out the optimum cabinet volume for the bass response I wanted, then I built (with some asisstance as I am pretty cack-handed) the cabs to suit. I figured this was the optimum way of doing things.

With this sub I am already starting with the cab so I need a driver to suit. I would estimate the cab is about 100 litres. As this is not a music sub - it just need sto reproduce deep bas effects for movie soundtrack replay, my thinking is that I can be a little more cavalier in terms of parameters.

What say you?

[Reid Malenfant]

Well yes, but wouldn't it be better to get some synergy between the driver & cab?

If you can find out the exact volume then we can predict what any driver will do in the enclosure, tuning can be tweaked etc. At about 100L the Lab 12 is still looking like a prime contender right now though :)

[Macca]

Well yes, but wouldn't it be better to get some synergy between the driver & cab?

If you can find out the exact volume then we can predict what any driver will do in the enclosure, tuning can be tweaked etc. At about 100L the Lab 12 is still looking like a prime contender right now though :)

Okay that makes sense. Later I will get the cab down and measure it, maybe take a piccy and post it up to give more of an idea.