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TVOR-Ceasar
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16/08/2019 4:51 pm  

I thought it would be fun to see what others could come up with in an off-the-cuff sort of manner, as if we were all sitting around the lunch table just dreaming up stuff. Doesn't matter what it is or how much it costs as long as it is a relatively quick idea thrown together in a short time and is fairly complete. Here's mine to start off:

What's cheap and sort of decent?   

All Parts Express for ease of shopping

Main:

Dayton Audio PC68-8 2-1/2" Full-Range Poly Cone Driver in a .075 Cu.Ft box with a 1"D x 2-1/3"L port - tunes to just above 95 Hz and runs to ~17 kHz. ($8.90 /piece)

Goldwood GT-302 1/2" Mylar Dome Tweeter 4 kHz to 19 kHz, crossed over @ ~8 kHz just for top end extension ($2.95 / piece)

Single NP electrolytic 2.7 uF makes the crossover 7350 Hz ($0.53 / piece)

L-Pad resistors (3 dB) 2.4 ohm 1/2 watt (at theses frequencies, they'll be okay - there's not much power there) ($1.01 /10) and 20 ohm 1/2 watt ($0.13 / 10)

Inside box size (Acoustic ratio) 6-3/8" h, 5" w, 4" d

Sub:

WP-6020i 6-1/2" Polypropylene Cone Woofer in a 1.2 Cu.Ft. box with a 1.5"D x 1"L port tunes down to 42.5 Hz (F3 in the 30's) ($11.88)

Inside box size (Acoustic ratio) 16-7/8"h, 12-3/4"w, 10-1/8"d

Amp parts:

2.1 Hi-Fi Class D Audio Amplifier Board 2 x 15W + 30W 10-18 VDC - More than enough for desktop or nearfield. ($10.98)

15V 4A DC Power Supply AC Adapter with 2.1 x 5.5mm Center Positive (+) Plug - perfect fit ($15.95)

DPDT Mini Toggle Switch Part # 060-338 ($1.57) to switch between sources - take (1) 1/8" stereo patch cord, cut in 1/2, solder to appropriate lugs, and then you can have 2 sources.

Since I envision this as a desktop setup, more or less, the 1/8" seems appropriate. Besides, you can buy a Bluetooth audio dongle at Walmart or on-line for around $6, sometimes less.

Grand Total $66.28 without tax or shipping and NOT including wood for enclosures. And about 1/2 of that is for the amp and power supply! Seems a fair price for a self powered 2.1 system with a solid range of 42-19,000 Hz at a max power of 15 Watts.

Parts list

Full range driver

Tweeter

Woofer

NP Capacitor

Resistor

Resistor

Switch

Amp

Power Supply

-Charlie


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123Toid
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16/08/2019 5:22 pm  

Nice!  What a great write up.

 


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TVOR-Ceasar
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16/08/2019 8:48 pm  

@123toid

Thanks. It was literally just a few minutes worth of looking and a quick run through of the T/S numbers. Took a lot longer to write it up than it did to figure it out. 

This is open to anyone who wants to participate in a "What If" type of situation. Doesn't matter what you come up with or how outrageous or mundane it may be, just come on and try. It can only make you a more adept hobbyist / designer. I do look forward to what others see in the supply chain.

To all: this is NOT a contest. There are no prizes, only hopefully great conversation and praise, along with growing knowledge on everyone's part. Jump on in!

-Charlie


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TVOR-Ceasar
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17/08/2019 12:50 am  

See, here's an inexpensive Bluetooth adapter.

Walmart

-Charlie


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shrub0
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20/08/2019 5:51 pm  

I like where this is going TVOR-Ceasar but personally i'd use a woofer with more xmax.


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TVOR-Ceasar
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20/08/2019 8:07 pm  

@shrub0

Yeah, it's a little shy in that respect, but at the power level provided, it's fair enough.

That's the great thing about this thread, it's not just about what I've come up with, but what anyone can envision. 

Do you see anything out there, not necessarily just at Parts Express, that looks like it might work in something you have in mind? If so, why not throw together a quick verbal rough sketch and share it? Maybe it'll spur someone else to join in. 

-Charlie


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TVOR-Ceasar
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29/08/2019 8:57 am  

So, I thought about this a little more and figured that if something like this were completely passive, that'd give me about $30 or so to play around with. And if they sounded good enough, they could go to MWAF for competition. 🙂

I would get another woofer and some "iron core" coils to keep the highs out of them.  Price would still be about the same. Parts #'s later.

Time to head to the lake.

-Charlie


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TVOR-Ceasar
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01/09/2019 12:01 am  

Just a quick update on my "What If".

Looking at the graphs available, it looks as if I should change the crossovers cap for the tweeter to a 5.6 uF value and eliminate the L-Pad resistors. That puts the crossover at 3550 Hz. The tweeter is almost perfectly matched to the full range driver at that point and is past the point of max SPL. That'll pull $1.14 out of the price (resistors), but since the caps increase to 59¢, that adds 12¢ back in. So a reduction of $1.01.

New capcacitor

At this point, I have the option to lowpass the full range and pull out the high end where the tweeter would be working so well.

If I did, I'd probably go with a 0.25 mH coil to start cut off at 5kHz. That's $3.10 each, $6.20 total.

Small coil

So far that would it the original total up to $71.38 sans tax and shipping.

Now, to go back to the previous post, if I drop the amplification, that'll put me at $44.45 baseline. Making this into 2 full range speakers would entail another woofer@ $11.98 and 2 coils to lowpass them at 255 Hz (5 mH) for $6.99 each. That would bring my grand total up to $70.41.

Woofer coil

That's less than $1 difference between a 15/30 watt 2.1 system suitable for desktop / dorm room and a larger passive "bookshelf" quasi-3-way system that, using conventional manufacturer's methods, is rated at 110 watts.

I'm torn between the two. Hmmmm...  

-Charlie


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TVOR-Ceasar
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01/09/2019 12:33 am  

When all you have is pencil and paper to combine graphs.

P 20190901 002955 1

 

 

-Charlie


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TVOR-Ceasar
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02/09/2019 1:45 am  

Since I don't have access to my design software this holiday weekend (as you've seen above) other than finally getting QBasic to run on my tablet, I get to commit rough ideas to the sketch pad. Keep in mind, all I have is a pencil and sketch pad,  no drawing tools, and no real good surface with decent lighting I can use .

Take #1,  Powered 2.1 system

P 20190902 011204~2

Take #2, Passive 3-way

P 20190902 011300~2

 

Two very different designs using the same drivers.

 

**Addendum: did I mention doing this late at night, rather hastily? If not, there you go. 🙂

-Charlie


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Justin D
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02/09/2019 7:02 am  

Looks very different from what I'm doing on a 2.1. I'm using a set of 6.5" component car speakers with 1" tweeters and putting them in proper cabinets I'm  6.5" suputting matching  in a separate matching vented cabinet with 70w plate amps. I'll post pictures when it's done.


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Justin D
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02/09/2019 7:04 am  

Looks very different from what I'm doing on a 2.1. I'm using a set of 6.5" component car speakers with 1" tweeters and putting them in proper cabinets I'm  6.5" suputting matching  in a separate matching vented cabinet with 70w plate amps. I'll post pictures when it's done.


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TVOR-Ceasar
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02/09/2019 2:21 pm  

Would like to see them and am looking forward to their fruition.

I've done a few with automotive speakers before with decent results. Usually, they require a good size box for any real bottom end. I still have a set of Kraco 6x9 3 ways that I need to pull out of storage to do something with. These were in my first car and were killer back then.

-Charlie


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TVOR-Ceasar
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02/09/2019 2:23 pm  

Like I said way above, anyone else is welcome to come into this thread. Take a look at your favorite supply house or houses, pick something that looks promising and throw it out here with your first impressions / thoughts on what to do with it. Doesn't matter how inexpensive or exotic, it only matters that you exercise those brain cells. I want to see the creativity you have floating around in your cranium(s). Let those dreams out. You never know when that thought might come to fruition or spark someone else's imagination.

-Charlie


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