My (mostly) DIY system.

[admin_exported]

Hi all. After a (shaky) start here, I figured I show show you all what I'm listening to, then I'll go on to talk about how exactly I got to where I am today WRT HiFi.

Here's my record deck:

It's a Phillips one, which was lying around in my grandfather's loft, so he offered it to me. Of course, I said yes, and got myself a turn table, with spare needles. It sounds reasonable, but I'm not convinced the pre-amp (NAD, quite old) is right for it. Still, vinyl has it's charms.

Speakers:

Subwoofer:

This uses a pair of 8" woofers, with a circuit to get it to 28Hz see below for details.

My amplifiers started with a single 50W/channel thing. I used it with 2 pairs of the old 3-way speakers (quite common in 2nd hand shops now). Naturally, the 2 ohm impedance meant it wasn't too happy.

After upgrading the power supply,

I've got something that will actually hit it's rated output, with reasonable amounts of distortion.

I got another of these amps (from a skip, apparently broken). So, I ugraded the power supply again, then bridged it to give over 100W into 8ohm, and that went on to power my subwoofer. I also added a Linkwitz circuit, which has an eq curve which matches the rolloff of the subwoofer, meaning I can get output to as low as I want. Neat, huh?

Anyway, the subwoofer itself was made after extensive modelling, and eventually, I came up with a 42L sealed enclosure, using 2 bass drivers. I'm 16, living with parents, so, noise transmitted through the floor had to be minimal. Most of you will know of the B&W PV1 subwoofer. Mine's based loosely on that - the box doesn't vibrate at all, even at full power.

The main speakers use full range drivers, augmented by woofers. Most of you will know that a full range driver means there's no crossover right in the middle of the speech band, and this can help the sound a great deal. Anyway, I took the crossover way out of the sensitive midrange area, so it's at 300Hz, where the 2 woofers (per side) come in.

Again, when deciding woofer placement, they needed to be near the other driver (to avoid cancellation at some frequencies), and they also needed to be one on opposite side to the other, so there's no vibration through the floor.

This left me (after more modelling) with a frequency response that looks like this:

The blue line is the full-range drivers, the red and green is the woofers. I don't know why the green one contributes more than the red at higher frequencies, but it doesn't affect the sound, so I'm not bothered.

The sound.

This set-up, costing a little under £200, will happily sound better than anything I've listened to, upto and including £1000 worth of NAD electronics and Dali speakers, and that's through a cheapy usb soundcard.

To finish off, a picture of my whole system.

Chris

PS - questions happily answered.

 

[El Hefe]

Brilliant work you have done there. Such an enthusiast.

 

[vinod_david]

Superb for a DIY setup.

 

[Anonymous]

Thanks for the kind words.

Are there any questions - I expect there might be some in the evening, but I've got time now, if you want to avoid the rush.

 

[idc]

When I linked to your post there were photos of the inside of the speakers. I would like to see as much as possible about their build.

Have you thought about a finish to the speakers as well?

 

[Anonymous]

his must be the best DIY job I've seen so far!!

 

[Anonymous]

Hi all.

Thanks again for the comments. I've taken some pictures of the inside of the subwoofer, if anyone's interested. I've only taken one of the construction of the main speakers, as I was far too eager to get it done. Still, I can explain what's there pretty easily...

Ohhh - blurry...

The horizontal brace is yet to be made (it's that good as it is, I don't want to have to pull it apart).

The design itself (both dirvers firing same direction, but on opposite sides of the box) reduces 2nd harmonic (mechanical) distortion significantly ie, it sorts out non-linearities between the driver moving forwards and moving backwards.

Last, but not least, the inside of the floorstander...

This is the inside of the main speaker. At the top, we have a 10:1 taper transmission line, which was then heavily stuffed. The purpose of this is to flatten the impedance of the full range driver at it's resonance, thus making the crossover act as it should. Changing impedance changes the crossover rate dramatically.

The rest of it is pretty straightforward. We've got a bass port at the bottom (gets them down to 40Hz nicely), and bracing down the middle to take out the worst of the cabinet vibration.

Thanks again

Chris

PS - here's some pictures of the design in development...

 

[Craig M.]

fair play to you! i hope you appreciate your parents, too. mine probably would have complained if i'd broken wind too loudly.

 

[idc]

So at the top left is where the speaker goes and behind that you have stuffed the cabinet and then put the top on? The the bass is obvious and at the bottom, please tell me that is a tin can you have used!

 

[Anonymous]

Sorry, but it's not a tin can... Cheap bass port of the correct dimensions.

Anyway, to answer your question..

You've got the idea - yes, you put a top on (otherwise, where would the cat sit?).

The stuffing works with the taper (heavier stuffing towards the end), to flatten the impedance. The end of the taper is open, but very little sound comes out.

Chris

 

[ear]

Any chances of putting out a video on youtube with sound?

 

[Anonymous]

Sorry, but I doubt that.

I've got a webcam, and a phone. The sound quality on each is poor.

I've split my money between my 2 main hobbies - mountain biking and HiFi. A decent camcorder just hasn't entered the equation.

 

[bballtom]

What are you studying at the moment, would imagine a-level physics?

Great system, just wish I had done something similar when I was 16 (27 now), at that time I got my first hifi but was also in mountain biking, still got my 10 year old GT Zaskar in the garage that I take out for a spin, still a much better bike than I could ever ride it.

So what made you do this and where did you get all the information from?

 

[Anonymous]

You're a year out, but that's what I plan to study (just turned 16). I'm torn between being an engineer, and going into medicine, so I've picked A-levels which suit both.

Anyway, the design was 40% help from someone on another forum, who had already tried the idea (you know when you get those ideas, buzzing around in your head, but someone else has beat you to it). I set up a thread where questions were asked about the design.

After this, is was time to choose the drivers I wanted to use (the other guy had spent £70 per driver, but only used 1 bass driver per side). So, I did some modelling of the Visaton speakers available to me, and the W130S came up trumps. I had already chosen the full range driver, as I had tried a lesser version (lower efficiency), and really liked it, so the higher efficiency version was just as good.

I did my own crossover, modelled different shapes and dimensions of boxes, and the ones I came up with (with the full range driver offset) gave the smoothest response.

There was an interesting challenge represented by the modelling program. It's brilliant, free, and all in German. After using google translate for some bits, I became fluent in German speaker designing.

The design was simply a quest to get sound significantly better than the Mission 760is they replaced. I like the cohesion of full range drivers - no crossover in the sensitive midrange area, but there's a lack of bass. Large full range speakers weren't an option. At a decent one comming in at over £100, I wasn't going to bother. So, I'd set my heart on a system that used a small full range speaker. The problem then was to overcome the lack of bass. When we need more bass, we add more woofers, which I did. My whole system now moves slightly more air than a 15" woofer, meaning it goes pretty loud.

The design itself also has a name - FAST, standing for Full-range And Subwoofer Technology.

Chris

PS - I applied the same DIY idea to my bike, spreading the parts over around 5 years. Started with a rubbish bike when I was 11, new forks when I was 12, new wheels after a 3' drop to concrete, hydraulic disks at 14, then a new frame at 15.