Norpus' first IB

[norpus]

Here is my first diy speaker project blog

IB Sub

My objective
was to do a double leap of technology by listening to other DTV forum members dreams last year and doing it first as an early adopter here in Australia. I had a lot of faith in these guys and their sub knowledge and enthusiasm btw (credits to Spearmint and Nobby)
Wanted never to worry about lack of quality bass - this seemed the ultimate bang for buck
Wanted to meet/exceed the THX spec for subwoofer of 121dB available output

Method
IB Infinite Baffle Sub manifold with 2 x 18" Avalanche drivers, mounted in floor to minimise number of big black boxes in the room (WAF is positive).
Purchased imported drivers ex another forum member delivered on Saturday Feb 25, box constructed during the following week and installed Sat/Sun 5/3/06

Room location, in between mains. Hole is 650 x 610mm

Made manifold box from 2 sheets 18mm construction boxing ply (waterproof as under floor). Routered the manifold to allow flush fitting of drivers - in hindsight wouldn't bother with the hassle next time

The drivers weigh 20kg each - the magnets shagged my crt picture from over 1mtr away - total rainbow of colour needed degaussing after they passed by the screen hehe

The manifold went under floor - bottom half painted with bituminous paint as it is partly below ground level. and yes the box became bigger than I'd thought. Internally, it added 230 extra litres to my room

We needed to dig 7 wheelbarrow loads of dirt out from underneath to allow us to fit from top (not easy btw) rather than fitting drivers from under house crawling on belly (< 600mm clearance under floor).

We then lowered box in to hole and fitted the drivers leaning in from top (2 man op, not easy took 2 hours to get it right). Then used a strop over back to lift the box (now 80kg with drivers) into position whilst Mac drilled with coach bolts into floor joists on 4 sides. (The wires were left there untidied for Foxtail )

Roughly finished product ready for first test using 2ch of the Elektra theatre 7 until the behringers arrive. Needs paint touchup and tuning. Also a grate to fit over the hole so pieces of furniture don't fall in and damage the drivers (and yes I have tried that already by mistake with one of my mains ). Luckily I didn't get the 'oversized' 600x600mm return air grate I'd found on the web, as after building the box with 40mm walls, I found it was somewhat undersized and would have fallen in

Behringer A500 amp and FBQ2496 feedback destroyer to power it
http://www.musicianswarehouse.com.au...ctCode=FBQ2496
http://www.musicianswarehouse.com.au...oductCode=A500

Cost Summary (I knew you would ask)
Cost materials and labour - around $2.5K AUD (including 2-3 man-days over the week)
Cheap considering the quality of these drivers is superior than your average box woofer and it has been designed to outperform most box woofers for HT above the $5K mark (conservatively)


Thoughts
Yes they are overkill for my room, but hey I happen to like that concept

[Exocer]

Exciting project you have there! I remember reading up on the close-out Avalanche deals...but didnt understand at the time how a single driver could be worth $300... I wish I could go back

That behringer seems like a great amp for this application indeed. Hope you enjoy the end result.

[norpus]

Exocer wrote:

Exciting project you have there! I remember reading up on the close-out Avalanche deals...but didnt understand at the time how a single driver could be worth $300... I wish I could go back

That behringer seems like a great amp for this application indeed. Hope you enjoy the end result.

Thanks, yes it was a bit of a pioneering exercise for me as I'd never seen or heard an IB before. Just talk on the net and a couple of mates who'd seen one

I also was not prepared to pay lots for drivers - they are twice the price here and more due to transport/import costs. I ended up paying well over $1000USD for the 2 Avalanches from a guy who imported 6 into Australia. So $300 is nothing - in fact thats what the lowly Tempest 15D8 cost me.

The behringer A500 is a great little amp for bang/buck ratio. However I have found it doesn't really have the grunt to run 2x18 fully. I suspect it is really only 150w rms or so. Hence it will be retired for something better soon - maybe something with phase control built in