First project. Need advice and help!

[elnewb]

Hi guys,

I want to make a smallish speaker system for me and my fellow dormies (No one has any decent speakers). And preferably on the cheap. I have experience soldering simple kits and today built the "champ" amplifier kit and regulated power supply quite quickly and without any hassle.

The aims for the system is to be loud, as cheap as possible and durable.

I've looked at suitable parts online for the system mostly at jaycar as other places cannot do not seem to be able to come close to their prices (perhaps this is an indication of quality?).

Anyway here's what I've decided I want to build:

2x Studio Monitor type enclosures
1x Subwoofer

So a 2.1 system. A diagram of the setup is below:


Click for full size - Uploaded with plasq's Skitch


Monitor contents (One monitor):

1x 8" Paper Cone Woofer @ $39.95 Each
CW2196 http://www.jaycar.com.au/productView.asp?ID=CW2196
Impedance: 8 ohms
Nominal Power: 90 WRMS

1x Piezo Horn Tweeter @ $29.95 Each
CT1934 http://www.jaycar.com.au/productView.asp?ID=CT1934
Impedance: 8 ohms
Nominal Power: ?
Max Power: 400 WRMS

1x 2 Way Speaker Crossover 3.5Khz @ $12.50 Each
CX2614 http://www.jaycar.com.au/productView.asp?ID=CX2614
Impedance: 8 ohms
Nominal Power: 50 WRMS

Cost per box: $82.40
Cost for two: $164.80

Potential Issues?:
- Crossover not being able to handle the power from the amplifier. Is this fixable?
- Building an enclosure? I'm not sure how to go about this. Are there pre-fabbed enclosures around?

Subwoofer contents:

1x 12" Response Paper Cone Woofer @ $74.95 Each
CW2199 http://jaycar.com.au/productView.asp?ID=CW2199
Impedance: 8 ohms
Nominal Power: 225 WRMS

Cost per sub box: $74.95

Speakers and Sub total: $239.75 + Enclosure + Wiring/Plugs

Potential issues?:
- Again the enclosure. I know sub woofer enclosures are available but they can be expensive.
- Also, is it necessary to use a crossover so that the woofer is only sent a signal with frequencies within it's responsive range or is this not necessary?

Next is the problem of amplification. The best solution seems to be a dual-mono (to achieve stereo) amplifier for the pair of monitors and then a separate amp for the sub.

Contents of the Monitor Amp:

2x Ultra-Low Distortion 135WRMS Amplifier Module @ $94.95 Each
KC5470 http://www.jaycar.com.au/productView.asp?ID=KC5470
135WRMS into 8 ohms (Using this as the speakers have an impedance of 8 ohms)
200WRMS into 4 ohms

2x Power Supply Kit for Ultra-LD Mk2 200W Amplifier @ $55.95 Each
KC5471 http://www.jaycar.com.au/productView.asp?ID=KC5471

2x 40V-0-40V 300VA Toroidal Transformer @ $84.95 Each

1x 2 Unit ABS Black Rack Case @ $59.95 Each
HB5150 http://jaycar.com.au/productView.asp?ID=HB5150

2x Diecast Heatsink @ $25 Each

Cost of Amplifier: $581.65 + Connectors and Wiring

Contents of the Sub Amp:

1x Studio 350 - High Power Amplifier @ $175.00 Each
KC5372 http://www.jaycar.com.au/productView.asp?ID=KC5372
200WRMS into 8 ohms (Using this as the speakers have an impedance of 8 ohms)
135WRMS into 4 ohms

1x Power Supply

1x 70V-0-70V Toroidal Transformer

1x Diecast Heatsink @ $25.95 Each

Cost of Amplifier: $200.95 + Toroidal Transformer + Power Supply + Connectors and Wiring

Potential issues?:
- I can't find an appropriate power supply or toroidal transformer for the Studio 350 Amp.
- Cost. This is starting to add up. The speakers are affordable enough but the amps are jacking up the cost.

Any input on this would be greatly appreciated. I'd like ways to cut the costs down and still stick to the original aims of being loud and durable. As this is my first project I am unsure as to if this is under or over kill. As I said before any and all feedback is welcome.

[Beftus]

Hmm, decent and cheap only seldom go together. You could start with just two monitor style speakers and add a sub later if you need more "ooomph".

As a side note: I think there's a bit more to loudspeaker building than just making an enclosure and mount two drivers and a crossover into it... Have you been here? http://www.theloudspeakerkit.com

For the novice diy-er a kit a great way to start.

[pacificblue]

You could certainly get away with much less amplifier power, even if you want it loud.

Have you considered to use a 2.0 setup? That would save the active subwoofer crossover and amplifier. A second of those 12" woofers plus crossover could be cheaper than that.

Build the speakers and test them with your Champ. Then decide, if you need more SPL = power. If you do, look for Alesis or Behringer PA amplifiers. You should get them for less than 581 AU$ with all protection circuits on-board and waranty.

[JSW]

Did you ever atttempt to build this amp?

[AndrewT]

it will be cheaper to select higher sensitivity speakers/drivers and set your power targets appropriately lower.
eg.
86dB speakers and 300W
or
90dB speakers and 120W
or
94dB speakers and 48W
all give about the same maximum SPL (about 105dB to 107dB at 2.5m listening distance).

Don't bother with the separate woofer initially.
Just build a pair of 94dB/W/m 8ohm two ways using 7inch to 9inch bass/mids with matching tweeters.
Try using a 50W or 60W amplifier to drive these.

If you do decide to add a separate bass speaker, then be prepared to be evicted from your dorm.