building my home sub ala Vikash ;)

ok heres some pics; we all love pics

passive radiator



the drive unit to go in (see earlier thread)

the 80w amp

 

box building

Here you can see the front, side and bottom pieces. The Bottom measures 380x356 as I am using 12mm MDF and 18mm MDF front and rear baffles- bit easier than grinding a bit of 18mm away to make the driver and amp sit flush



close up of one of the side panels. Note the bits of 18mm mounted ontop of the panel. This should make the box much stronger and provide more support.


and using some bathroom sealant from a bathroom (surprisingly) project 12months ago we stuck the pieces on.


another mockup showing the pieces in position.


starting on the top and bottom pieces, we need to only put extra mdf strengthening pieces on the top and bottom to strengthen the baffle and amp mount panel


a finished side panel

note the MDF split- we cut against the grain so that when the screws are finally in the finished article they are going in the grain ergo stronger
This is B&Q £10 a big **** off sheet as my dad works there and gets discount. Probably best to use better MDF
And a finished top panel


some of todays finished work


to come- mounting drivers, fitting the bracing panels, fitting the 12mm and 18mm MDF pieces together at either end etc etc. If you click on my home audio pic you will see my Vaessen speakers are painted grey with nicely rounded off edges. I'm hoping to get the sub to look like that or just nicely veneer it.

 

I can't see the split in the photo,
...but if you're screwing into the edge of mdf you always have to drill a pilot hole or the mdf will split, whatever its thickness/strength. There isn.t really a 'grain' in mdf (it's papier mache really), but there are effectively a series of layers running through the thickness of the material.

 

if you look at the 3rd photo from bottom, top right screw, there is a split.
Its going to be quite a cute little box i think. I did mean to ask Vikash how his sounded before building mine incidentally. I'm assuming he's happy with it

 

Rory, I wouldnt put those drivers face down. The roll surround is about 1cm high and you could bugger them. I made standoffs for the grills on mine and used 12" grills for a 10" driver, just so they wouldn't make contact with the 13mm forward excursion

 

I just use huge feet which screw into the bottom which I have made provision for (threaded inserts). You need more than just enough clearance for driver excursion - enough to let it breathe too. Otherwise I wouldn't attempt to put a driver or PR at the bottom.

And it sounds briliant with the XLS10. Bracing is paramount as this puppy shifts some serious air. Ideally it needs a better amp than what I used.

You must always pilot drill holes for screws in MDF. I no longer use screws in cabinet construction. There's no need. Now that's an even better way

Also, I highly recommend using threaded inserts to mount the drivers and plate amp instead of t-nuts, and defintely don't use scews:
http://www.madaboutsound.com/prod_det.asp?product_id=16

 

Graham- the surround was unbelievably stiff for that passive radiator and the things so light anyway it hasn't done any damage or marked anything
Vikash- there were pilot holes drilled, believe it or not! its just poor MDF quality

 

use bigger pilot holes !!

 

some updated pics

 

right well i've sort of finished the sub. Have yet to seal the enclosure. On testing it there doesn't appear to be any bass below 30hz. What results did you get Vikash?

 

The sub goes quite low, but remember it's a 10" driver so high SPL at low frequencies is never going to be massive.

As for your implementation, you've literally dumped a driver in a box without tuning the PR accordingly or selecting enclosure volume based on the driver as you should. NOI. But if you're not happy with its output, then I would look toward slotting the xls10 driver in there as design intended.

IIRC at ~30Hz the PR should be in its element. A relatively small input signal should see that PR shift some serious air. I did some tests and the driver hardly moves, while the PR is making the whole box skate around. You should definely have output

 

Here's modelled response and excursions graphs (anaechonic) in 28l with xls10 and PR combo.

There's a lot of data to take in, but you can see that extension is quite good for a 10" in a small enclosure. Factor in room gain and this puppy kicks. Also notice that at around 25Hz when driver excursion is at minimum (resonance) the PR is at max. PR excursion goes past its rated limits at ~28Hz with >120w input so you're looking at 100db SPL at 25Hz within excursion, and 106+db higher up the range if you ignore the PR excursion.

So you can see some of the data to consider when selecting a driver and enclosure. No idea what your driver will result in. But that's not to say it can't be good.

 

how much weight did you settle on for the passive radiator by the way? I haven't added anything yet. I must say, its articulate, clean bass, just not deep. The original Paradigm cabinet was ported and slightly longer so this is obviously a totally different enclosure for it, which is why its not possibly performing at its best.

 

I used the 265g passive with no additional weight added.

Remember that a PR, for all intents and purposes, is the same as a port. It has a few advantages over a conventional port such as no port chuffing, alternative where long port tunings won't fit, and easier to adjust tuning; and one big disadvantage - cost. But in essence is does exactly what a port does.

edit: and congrats on your 1000th post