Quick Amplifier Clarification

[cynicmonster]

Hi All ,

I am in the process of planning/building a dedicated jukebox for my shed. I want to have external speakers.

My aim is to run a pair of 15" 120W Party Speakers (refer www.jaycar.com.au) in parallel off a 180W Mosfet amp.

I am not interested in hi-fi or stereo, just volume.

Will this work?

Regards,

Monster

[MaximRecoil]

Are you talking about these? -- Link

If you are looking for volume without regard to sound quality, on the cheap, those should be just the thing. Four piezo drivers in those things, lol. Those things scream; especially eight (!) of them in a pair. And those 15" drivers, even though they are not actual subwoofers (just big woofers doing bass/midbass/midrange duties up the line until the parade of piezos kick in), and even though they can't handle much power; simply by virtue of being large and in a ported enclosure, and the fact that you'll have two of them; they should move a good deal of air.

Now you say you plan to run them "in parallel off a 180W Mosfet amp". Do you have a link to this amp you are talking about? Keep in mind that if you run them in parallel, you'll have mono sound. If you don't mind spending more money, pick up four of those speaker boxes, get yourself a 250W x 2 @ 4 ohms amplifier, and run 2 of the boxes in parallel off each channel. That would be stereo, and should be plenty loud enough for your shed, and get the neighborhood cats howling to boot.

If you are into DIY audio, I think you could build those speaker units for cheaper than $170 each, and probably get higher quality 15" woofers in the process.

You could start with this 15" woofer from Dayton (a reputable speaker company) for $47.65 USD -- Link

Get your 3 piezo tweeters here for $1.44 USD each -- Link

And your wide dispersion piezo horn here for $1.78 USD -- Link

So that's a total of roughly $50 USD for the speakers. You'd want some 3/4" MDF to build the boxes from. You would use less than a 4' x 8' sheet per box -- you might even get two boxes out of a sheet. Figure about $30 USD per sheet.

I've seen the inside of those prefab piezo/woofer boxes, and there are no crossovers or anything, so no added expense there. They are just wired in parallel. It doesn't drop the impedance because the speakers in there that are wired in parallel cover different frequency ranges, and the natural roll-off frequencies of the speakers become the crossover points.

[cynicmonster]

Hi MaximRecoil,

Thanks for your response.

The amp link is here: http://sound.westhost.com/project101.htm

I am not particularly interested in stereo at the moment, but I hope to construct in a way that would make further improvements possible (gotta think about the $$$ factor  ).

I am tossing up whether to go with this amp (I really like the specs of it) or look at the option of a car amp. Any suggestions would be welcome.

Regards,

Monster 

[MaximRecoil]

Interesting amplifier. Have you built it yet? A pair of those "party speaker" units wired in parallel would present the amp a 4 ohm load, and that amp does 250 watts RMS @ 4 ohms. Not bad. It appears to be a mono amp, so the only way you'd get stereo is to use two of them anyway.

I am tossing up whether to go with this amp (I really like the specs of it) or look at the option of a car amp. Any suggestions would be welcome.

You'd need a substantial 12 VDC power supply to run a car amplifier big enough to power a pair of those "party speakers". A run-of-the-mill 100 watts x 2 @ 8 ohms home stereo receiver would be the easiest way to power them, plus you'd get stereo by default.

[cynicmonster]

No, I haven't built this amp, but have had my eye on it for a while. One of my biggest factors is still cost and, as much as it looks good, I might have to shelve it for another time.

I have been tossing up the idea of your amp suggestion and am starting to lean this way.

Thanks for the feedback. 

[shardian]

Apparently you are not on a budget.

To tell the truth, for a diy jukebox that puts out volume, your best bet is your local Goodwills and second hand stores. you can get old-school speakers with 15"woofers and amps for next to nothing.

[rovingmind]

check your local auction listings for storage unit auctions.

I just picked up a nice pair of vintage speakers for $20.  I could have gotten them for $5 if i had taken the time to remove them from the storage unit.  Instead i purchased them from the guy who bought the rest of the stuff in the storage unit.

They end up selling off TV's stereos, I saw an entire storage unit sell for $150 that had a pair of home speakers, and a projection TV plus alot of other crap.  You pull out something your willing to pay $5 to start and bid accordingly.  Most of the people who go to them are resellers around here.  They buy entire units of leftovers.

I picked up a vintage marantz hi-fi amp for $5.00 from my local goodwill.  that combination would make an excellent jukebox.  You might not WANT Hi-fi initially but it can be cheaper to go hi-fi than to do some custom build applications.

[cynicmonster]

Shardian, I am on a budget, but I'm in the planning stages. Leave me alone....lol 

OK, my aim is to build a 'low'-cost music machine that can be hired out around my local area for a price that will undercut commercially made machines (no time limit on this, mind you, but aiming for 2 yrs). Have looked into registration/licensing (Chris...will speak to you re: Wincab).

I live in a rural area and something I hear a bit about is the fact that as much as a commercial jukebox is available for hire, who wants to hear 2,500 songs about something they can't relate to (farmers, 50+...). Give them something they can specify as to what music will play. Give the Hirer a chance to specify what music is played at their party.

I assume that 'Goodwill Stores' are the same as our 'Op-Shops' (Oppurtunity Shops - charity-run) and to that extent, I have managed to pick up 2 units @ 50 W RMS/channel systems for a total of $20 AUD...just gotta get them working...   (Got my eye on a pair of speakers for $10 that needs minimal work).

I'm thinking that I should build a prototype for my shed...more to get the cabinet dimensions right. I want it easy to transport. My current design has a floorspace of 50cm x 50cm (inches: divide by 2.54) using a 14" monitor at a height of 100cm (front) - 115cm (back). Keep the button selection simple (alcohol factor... ).

So... I build a prototype for my shed (big shed, 11m x 10m, refer to conversion factor above...), throw in one of the 50W amps with the Op-shop speakers and see how it works.  Develop it from there.

Sounds fair enough to me...

BTW...happy to post photo's, details, etc. for the keyboard hack for this project. Let me know.



 

[rovingmind]

wouldn't a keyboard hack get a bit too bulky?

 My ponderings involve a trackball and 3 buttons for a potential user interaction on a DJ rig.

trackball for screen navigation, page forward, page backward and select  Less to go wrong on site.

[cynicmonster]

Ultimately I would like to see joystick interface with buttons, but it won't happen with the clientele in my area.

It's the KISS principle - Keep It Simple Stupid.

Give the customers the buttons to push. Swap the keyboard over when it matters...

[cynicmonster]

Further to buttons being pushed....

Should I look at a keypad (0-9, & page left/right) , or go for individual buttons (numbered 1 - 0, & page left/right), per Chris' numeric skin on Wincab (again, KISS)?

Input welcome.

[rovingmind]

that would depend on how much space you want the keypad to take up.  Maybe you could get an 80's jukebox keypad to use?

I wouldn't use a joystick just for hauling purposes.  The trackball and buttons won't stick up as high and a simple latch cover can protect them.

[cynicmonster]

Thanks rovingmind,

Same thoughts I had.

Looking at something like a 3U front panel as the mounting plate - 10 buttons (+page left/right), screen-printed labelling.

Hirer has access to main controls (master vol.,. etc.) accessed through the back/side.

I think that a trackball is too far ahead of the audience I am trying to reach.

[rovingmind]

maybe not if the cursor is a gigantic cartoon glove?   

which now makes me wonder how hard it will be to make a giant cartoon glove animated cursor.  The animation wouldn't be that hard but i've never looked at the format for cursors.

I've thought about converting one of those oldish console stereos.  take off the bottom legs and make a matching pedestal base to raise it up higher to almost bar height, add the trackball and buttons and install a monitor in the old record player hole.  I'm waiting to hear about one now.  If the electronics are dead its going to be my home jukebox.

[rovingmind]

flickr link to a nifty shot of a converted radio jukebox.