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Small DIY Subwoofer

A

AdamJP

Guest
To protect myself from any newbie bashing posts i'm gonna start by saying I have very little experience with sound systems.

I have a set of Creative P580 surround sound speakers which I picked up cheap and I'm looking at using a few of the parts for a DIY speaker setup for my GCSE DT project.

What I want to do is transfer the speakers, sub and panel amp into new boxes, which I will make. The speakers will be relatively straight forward but the sub could be tricky. I was thinking of upgrading the sub from the 5?" one already there to a 6" - 8" one, would there be any necessary upgrades to the amp or will the one in there cope?

What size box and port would I need for this sub?

Please go easy on me!

EDIT: Oh and cost is an issue!

Adam
 

Mylo

Distinguished Member
Unfortunately I don't think that driver would not be much use mate. The frequency response is probably that of a mid range speaker rather than a woofer.
 

HiFiRuss71

Distinguished Member
My expertise is limited, but go for a box about 30x30x30cm and tune the port to about 40-50Hz. The driver is a mid/bass unit so there is no point trying to drag low frequencies out of it that it was never designed to handle. With a peak power handling of 75w there is a choice of volume or depth and 75w won't give you any sort of audible depth, so don't try for it. It's also 6 ohm and I'm guessing the light weight paper unit in the creative sub is lighter and easier to drive than the unit you're looking at.

The creative sub is probably designed for maximum boom at the port frequency to sound big and impressive with games, so try to tighten the sound rather than increase or extend it.

I doubt the amp from the creative sub gives anything like 75w but it may be adequate for your purposes. Better would be to try and blag almost any cheap hi-fi amp. Ebay may help you here.

You may have to do more web research to find out what size (diameter and length) of port will give you the frequency extension required. If you start with the sort of cardboard tube that you get in a kitchen roll, you could adapt your project to investigate the different frequency responses, port length and diameter can effect.

Most schools have sine wave generators (raid the physics labs), so test tones and precise frequency generation should be easy. You're the bright young thing, so as to how you measure the output, I'll leave to you.

But if anybody on here gets sniffy, remember this. I haven't met many people on here who have tried building a speaker of any sort, much less somone of 16 years or less. So best of luck and bear in mind, all speakers, regardless of cost, are designed by a person. Those people all started somewhere and I think that was somewhere about where you are.

Russell
 

Mylo

Distinguished Member
If you check out the DIY forum on this site you will find some previous homemade sub threads.

Building DIY speakers is great fun and should be actively encouraged:thumbsup:
 

banners

Established Member
russ.will said:
But if anybody on here gets sniffy, remember this. I haven't met many people on here who have tried building a speaker of any sort, much less somone of 16 years or less. So best of luck and bear in mind, all speakers, regardless of cost, are designed by a person. Those people all started somewhere and I think that was somewhere about where you are.

Russell

LOL - I remember the first DIY speaker system I built. I was 15, and came up with the idea one night with a mate. The next day we built a plywood box about half the size of a wardrobe and made cut outs for 6 speakers - 3 a side, fastened them in ( with no regard to impedance:eek: ) and hooked the beast up to the cheap n nasty all in one unit. !WOW! sound came out:devil:
This really livened up my SNES playing at the time. Tv sat on top!
I'm still playing with DIY speakers, I just wish I had more time....

On to the original post, will what you're proposing to do satisfy the D&T Syllabus? After all it sounds like you just want to re house the units? Or are you wishing to modify the plate amp in some way to introduce an element of electronics??
Also Adam the driver at Maplin wouldn't be (high) on my list for bass duties. The resonant frequency is too high (Fs or Fo in listings of data). For subwoofers the Fs should be as low as possible (~35Hz or below generally).
I recommend you start a new thread in the DIY section, no doubt people around here will assist you with ideas.

Good Luck

Steve
 
S

skinnyfat

Guest
Adam

Hi and welcome.
To determine what size box and port to use you need to have the T&S parameters of the driver at hand. IMO an Fs of 85Hz is way too high for a sub. What is your limit when it comes to budget? Let me know and maybe I can help find you a more suitable driver. Once you've found that then we can sim up a few boxes and see which size suits you the best
 

Lewis123

Established Member
You could use a car subwoofer like this. Dont know what to do about an amp though.
 

IronGiant

Moderator
What is your budget? And perhaps more importantly, what is the brief for your project? Clearly you will get more kudos for designing a sub from scratch then reboxing the units you already have. There was a student from the States on here wanting to build a sub and his tutor told him he hadn't put enough effort into the design (not necessarily relevant in your case, but I would check your plan with your school if you haven't already).

Dave
 
A

AdamJP

Guest
Thanks for all the advice.

I'm talking to my teacher about different methods etc. and he recons it could be a good project if I research well enough. Most of whats above answers my questions.

Budget is about £30 or so.

Adam
 
S

skinnyfat

Guest
Adam

Here's a plot of that Tang driver.

Box : Vented 30.5 Lt
Vent :1 X 4.9cm diameter, 23 cm Length
Tuned to 25 Hz
Dimensions : 35 cm (w) X 35 cm (h) X 38 cm (d)

Max SPL wont be great due to low sensitivity but should max out at around 95 dB depending on your room response.
Remember that this plot is plotted at 1W at 1 Metre
 

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