The building your own portable soundsystem thread

[beesonthewhatnow]

I'm thinking more the random bits of homebrew electronics/batteries knocking around inside it

I think you'd be fine tbh, the worst they'd do is make you open it up in front of them to check it.

 

[stuff_it]

What about this idea then?

One of these
An amp like fractionMan

Two of these:
Speakers

Then make a box to put it in, and power it with a battery like fractionMans; The idea being to run my bass though it as a busking amp sort of thing for bbq singalongs and the like. Any advice welcomed.

You should use a proper bass amp, really

Innit, Fraction Man tends to short out if you let him overheat

 

[junglevip]

These are about the same price and much, much better (although they're bigger too - 8 inch) http://www.bluearan.co.uk/index.php?id=CELSUP8&browsemode=category

Thanks man! The bottom end frequency is only 100hz whereas the cheaper ones were 35hz (I am led to believe that low E is 40hz) will this matter? Also; would a 25w per channel amp blow a 15w speaker up?

 

[fractionMan]

Thanks man! The bottom end frequency is only 100hz whereas the cheaper ones were 35hz (I am led to believe that low E is 40hz) will this matter? Also; would a 25w per channel amp blow a 15w speaker up?

The amp is 25w into 4 ohms. it only delivers 13w into 8 ohms and it'll be fine.

You're right about the speaker though, I think it's a normal guitar speaker rather than a bass speaker.

What's your budget? Ideally you need to look at the response graph. Many cheap speakers say 35 or something, but really only start pushing out the noise higher up. Also, from what I've read, getting low E from a small speaker outdoors, is pretty much impossible. It requires a lot of power and large drivers. Indoors it's easier cos it bounces off the walls.

Anyway, take a look at this celestion product sheet for one of their 10" bass guitar speakers listed as 45-3500: http://professional.celestion.com/bass/pdf/BL10-100X8.pdf

Then compare it with the graph for the 8" I linked to here:
http://www.bluearan.co.uk/index.php?id=CELSUP8&browsemode=category

The difference is that the 8" has a higher resonant frequency (105hz vs the 10" 76hz), which put simply means the peak of the bottom end. unfortunately this isn't shown on the bottom graph.


You also need something like this (10x AA battery holder) http://cgi.ebay.co.uk/10-x-AA-Short...f63297012c0a0e2023771b7ff874e55#ht_1117wt_870 You can get them with the 2.5 power jack on the end suitable for pluggin straight into the amp somewhere.

 

[junglevip]

Thank man! My budget for amp and speakers is about £50, but I like the project side of things (I am banned from making grow rooms....) I have an acoustic bass with a built in pre-amp and i'd just like to keep up with a 5-10w guitar amp. If getting the low E is is a problem that can only be solved by money, then it can wait until I have some.

If you do get a chance to plug a bass into your system, then it would be nice to know how you got on. Thanks again.... . . . . .

 

[fractionMan]

Well, I've acquired a 6.5 inch stageline mid+bass speaker that looks promising for its size. I'm gonna see how that does at the low end.

If you want to piss about, just have the odd search for speaker on ebay. If you sort the list by things closest to you (auctions only), you'll be able to cut out the postage costs and land yourself a bargain driver or two. Just get yourself anything for under a fiver and experiment!

The thing I've found about ordering speakers is that the postage is huge. So a couple of six quid drivers ends up being £19

 

[skyscraper101]

Can't wait to see pics of this in the pram

 

[junglevip]

Well, I have bought the Tripath now. When it comes I can crack on with testing; looks like I will be learning how to use an oscilloscope

 

[ddraig]

still in the diff?
would like to see it in operation when done if ok
good luck

 

[junglevip]

Not in the big C at the mo...
I am sure we can sort a demo or something out though. Will probably be able to suggest design improvements by then aswell.
Cheers

 

[Crispy]

Bank Holiday Weekends?
I am ready for you.

 

[fractionMan]

crispy is confirmed awesome

 

[Crispy]

Cheers

I inherited some TDL floor standers some years ago, but dropped one in a move and utterly broke the drivers (2 in each cab). So I took one from the other cabinet and filled the holes with hardboard. Never really sounded right. So I thought fuck it, this is a much better use for them. On the side (not visible in this pic) I've mounted the original speaker terminals, so I can take the T-amp out and plug it into a proper amplifier, should I need to.

Wheelie suitcase was £25 from a local sells-everything shop. I already had a T-amp (and I'm not going to permanently mount it in this case, so it's still useful for other things). Might take it to hackspace for some finessing. The front panel could do with reinforcing and having the screws protected. Needs protective grilles and the wires/crossovers need tidying and it would be nice to make a 'slot' for the amp so that the volume knob on it lines up with a circular hole on the outside. Oh and an external input socket too.

 

[girasol]

Beauty, Crispy! I'd say the only thing missing, from a health&safety point, are some metal grilles to protect the speakers, i.e.

Something like:

 

[fractionMan]

I like the idea of using existing speaker drivers.

These for example are available to collect in bath: http://cgi.ebay.co.uk/Celestion-DL4...iFiSpeakers&hash=item33670e9cad#ht_500wt_1066

That's 2x quality tweeters, 2xquality 6.5" woofers, crossover and speaker terminals for £25

 

[electroplated]

What's the best technique for cutting the holes in suitcase like things, assuming you only have basic tools to hand?

Also, I was just wondering if I got a pair of old speakers and found a suitcase of (roughly) matching internal volume, would that make for potentially better sound, or would thta be a massive oversimplification on speaker theory?

 

[Crispy]

I just stabbed at mine with a kitchen knife
Fractionman used a jigsaw, which should be fine.

No idea on the theory. My wheelie case is roughly the same volume as the speaker cabinet that used to house those 2 drivers, but high fidelity is not really the aim here!

 

[ViolentPanda]

What's the best technique for cutting the holes in suitcase like things, assuming you only have basic tools to hand?

Also, I was just wondering if I got a pair of old speakers and found a suitcase of (roughly) matching internal volume, would that make for potentially better sound, or would thta be a massive oversimplification on speaker theory?

From my limited experience of building cabs (a couple of 2x12" cabs for guitar, and a set of 4 speaker cabs (mid-range and tweeter plus r/f bass port), the closer you can get the volume to the volume specced for the speakers, the better.

There used to be a cheap book available from Maplins that did a good basic explanation of why sticking to the specs was best. I'll have a think about the title and post it if I recall it. Twas only £5-6 quid.

 

[ViolentPanda]

I just stabbed at mine with a kitchen knife
Fractionman used a jigsaw, which should be fine.

No idea on the theory. My wheelie case is roughly the same volume as the speaker cabinet that used to house those 2 drivers, but high fidelity is not really the aim here!

You should get decent repro though, as long as the case isn't too much less rigid than the speaker cab was.

 

[Mation]

I just stabbed at mine with a kitchen knife
Fractionman used a jigsaw, which should be fine.

No idea on the theory. My wheelie case is roughly the same volume as the speaker cabinet that used to house those 2 drivers, but high fidelity is not really the aim here!

Sounds good though!

 

[Crispy]

Also, the original cabs were ported. Should I port my suitcase too? I could reuse the tubes.

 

[fractionMan]

Ideally you'd somehow separate out the two channels and give them a compartment each, but hey, it's not the end of the world if you don't.

 

[fractionMan]

Also, the original cabs were ported. Should I port my suitcase too? I could reuse the tubes.

Tuning ports is something to do with drivers+cab size+port length+port diameter. Not sure what though. You can tune them to specific frequencies. There's a prog called winSID or something that works it out for you.

I considered it for a couple of my boxes but figured I didn't know enough to do it properly.

 

[ViolentPanda]

Tuning ports is something to do with drivers+cab size+port length+port diameter. Not sure what though. You can tune them to specific frequencies. There's a prog called winSID or something that works it out for you.

I considered it for a couple of my boxes but figured I didn't know enough to do it properly.

WinISD.

Fine for Hi-Fi, not really necessary for something used in mobile and changeable conditions, though, IMO.

 

[Crispy]

Ideally you'd somehow separate out the two channels and give them a compartment each, but hey, it's not the end of the world if you don't.

Most of what I'll be playing on it doesn't have a great deal of stereo separation, tbf

 

[fractionMan]

Yeah, that was my conclusion

 

[fractionMan]

Simple crossovers explained

Great guide to simple one component high/low filters

 

[fractionMan]

I just ordered a hole cutter!

http://www.amazon.co.uk/exec/obidos/ASIN/B000LFU94G/ref=pe_thx_sims_1

Ok, it's a bit crap but I think it'll still be better than doing it by hand with a jigsaw.

 

[Crispy]

very handy

 

[fractionMan]

Great thread about speaker parameters, calculating box size and why car speakers are shit

(accompanying sealed box calculator - ignore some of the notes about resonant freq as they're about subwoofers)

Also, this later in the thread:

But you can see how it works by downloading WinISD and then putting in the parameters for any speaker. It will then suggest an optimal cabinet volume based on a optimal Q of 0.707 (which is optimal for indoors use in a midsized room, 0.5 is optimal in a small room, 1 in a large room and 1.214 in free field).

Not sure how this works with two speakers in one box