First DIY Project Subwoofer

[ozynigma]

Hi All,

Found this site by accident and am very impressed with the level of knowledge and enthusiasm shown.

I am about to start my first DIY project. I am looking to replace a JBL Digital 10 Subwoofer in my HT system. The JBL only goes down to about 34Hz which is only 8Hz below my main speakers.

Before I start designing the enclosure (which I will also need some help with) I would like some advice on placement.

Currently I have the forward firing ported subwoofer IN the cabinet. It fits neatly and I cannot detect any significant change in performance from having it in the corner of the room.

The attached image shows where the current subwoofer is located and you can see that the main speakers fit nicely into the corners of the room.

1) So should I make my new enclosure to also fit into the cabinet or should I make it freestanding and rearrange the living room? (Note room is 4.8m W x 6m D x 3m H.)

2) High sound levels are not very important to me as the neighbours (and wife) are already complaining. Can a single 12 inch 100 W sub in a sealed enclosure get down to 20Hz and improve my HT setup?

I am currently sourcing a driver and amp and will advise specs when I have them.

Thanks
Ozynigma

[busterno1]

The answers to your question will depend on which driver you get .

It will tell what sort & size of box you need to use .

Yes some 12 "sub drivers will go down to 20hz .

Some of It will depend on your choice of driver

do you have a budget in mind . I am sure there a aussies here which gladly offer advice on what drivers are available

[ozynigma]

Hmmm budget....

Well initially I am treating this first project as a bit of an experiment so keeping the costs down. Looks like I can get the amp for under $200AU. I might be able to get a slightly used Peerless driver under $100AU. However I would probably be prepared to pay $150-300AU for a new driver if necessary.

I noticed that SkinnyBoy had two 8" Peerless drivers for sale on the trading post of this site........

Ozynigma

[moving_electron]

Given the moderate SPL and small cabinet size benefit, Linkwitz transformed sealed sub might make a lot of sense. Could make a nice low Q sub crossing in at 60 or so.

It would be interesting to calculate what could be done utilizing your existing sub by sealing the port and utilizing a LT. A new 12 inch would give you more SPL, but you may be able to take the existing JBL very low and give you very tight base for music.

[ozynigma]

I have been looking at the Linkwitz site and conceptually I think his Thor design of a 12" driver in a 50 litre sealed enclosure could be the way to go for this beginner with only moderate expectations for SPL.

Yeah I could try modding the JBL but I am thinking of using it as is with my PC and some self powered satellites (my next project???). I think I would need to learn a lot more and probably need some test equipment to go down the route of modifying the JBL.

Also it seems strange that JBL would not have optimised the subwoofer to deliver deep bass. Perhaps they ported it to maximise SPL at the expense of frequency range?

Ozynigma

[michael]

A ported enclosure will always go lower than a sealed one and it will with the same driver be a larger optimum enclosure.
I suggest you look at the Adire DPL and the Shiva, both of which at 12"ers with rave reviews and high SPL capabilities. Both will cost you about 300.
A driver between these two would be the Eminence Lab12 at the same price it is better built than the shiva and has higher efficiency than the DPL.

what size is that other sub that you have and how deep can we put it in the rack. That way we can see how much space there is to work with. And i think that you want a ported as sealed would not go as low as the JBL there.

[BAM]

It's my understanding that the DPL12 likes smaller sealed boxes.

[michael]

It's my understanding that the DPL12 likes smaller sealed boxes.

To a degree, it performs better than most in sealed boxes, though those sealed boxes are around the 60L mark.
Its F3 will be about 10hz lower than the shiva in the same box.
But i would turn him away from the DPL due to its low efficiency of 84db, this with his desired 100w would make a rather low spl subwoofer.

[ozynigma]

The rack is 400mm deep.

So I can go a box size 400mm D x 450mm W x 345mm H.

With 20mm thick material that would give internal volume of 47 litres, less the internals.

If necessary I can go taller on the H dimension up to say 450mm.

I am currently attempting to source a cheap Peerless 12" Bass Driver 831857, specs are here ;
http://www.d-s-t.com/peerless/dataover/wo_class.htm

This and a 110W amp are my starting point.

Any advice on box size and porting alternatives and their effectiveness would be appreciated.

Ozynigma

[michael]

The peerless 831857 requires at least 140L to work, i recomend that with that 47L to play with that you push your budget up and go for the adire DPL12, put it in the 47L box, heavily stuff it with polyfil and throw about 200w at it, wes components sell a 200w plate amp for 300 that is very good (have it myself).
This will give you 103db of output at 30hz with an f3 at the same point. you will also have the headroom of the large excurtion.
All in all would cost about $600 for the parts then more for the box.