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Author Topic: Campsite Subwoofer (hobby project)  (Read 975 times)

Frank Koenig

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Campsite Subwoofer (hobby project)
« on: April 08, 2021, 05:06:05 pm »

Loud, low, or small. In this instance I chose low and small. Over the years I've amused myself (and worried my fellow campers) with small, portable playback systems that run off tiny amounts of 12 VDC. This keeps me busy and supplies Parts Express with a steady income. The current addition to the kit might actually be of some use in very small-scale live sound or installations, so I post here.

The driver is a B&C 12BG76 12 in. woofer with fs = 44 Hz, Vas = 1.13 ft^3 and Qts = .41. B&C recommends a 1.4 ft^3 enclosure with fb = 42 Hz. After some fiddle-farting with the model I arrived at 1.5 ft^3 and 40 Hz, which, usurpingly, is pretty close. I wanted to use 4 in. ABS DWV pipe for the vent to keep the velocity reasonable and for ease of tuning. This results in a vent length of about 11 in. Making room for it on the front of the box results in the box being too shallow to accommodate the length of the vent (without bends) so I moved it to one side. As the box will be used solo with nothing beside it this should be OK.

For amplification it became a dance between peak voltage (good) and idle current (bad). I settled on a "Sure Electronics" "200 W"  single-channel amp board from, where else, Parts Express. It allows a maximum supply voltage of 36 V at which it can put an honest 50 W into 8 Ohms. Distortion measures at under .2% under normal conditions and I suspect is actually a bit better as the HF hash on the output may throw-off my antique HP distortion analyzer. The clipping behavior on this amp is a bit weird. It doesn't clip cleanly as one would like but rather grows a beard of switching hash on the part of the waveform that exceeds the amp's voltage capability. To keep an eye on clipping I added a small home-brew clip detector that lights an LED when either output gets within ~3.5 volts of ground. (The amp is single-supply in a bridge configuration and quiescent output voltage is 1/2 the supply.)

To get 36 Volts I ordered from DigiKey a 24 V, 4A output DC-DC converter made by CUI. Since its output floats it can be wired in series with the 12 V supply to achieve 36 V. (I actually trimmed-down the convertor to 22 V so as not to bust 36 V by too much when the battery is charging.) Idle current for the whole shebang at the 12 V input is ~475 mA.

I added a switch-selectable direct connection to the driver so that the speaker can be used with an external amp in louder, shore-powered situations.

The frequency response plot was taken with both speaker and mic on the ground 20 ft apart with no other boundaries within the 200 ms window. (The dB scale is relative, not SPL.) I'm very pleased with this result. An ~4 dB shelf makes it flat to < 40 Hz and so far I think it sounds fantastic, which is entirely due to the excellent, modern driver design from B&C. I would definitely use this driver again.




--Frank
« Last Edit: April 08, 2021, 05:25:08 pm by Frank Koenig »
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Steve-White

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Re: Campsite Subwoofer (hobby project)
« Reply #1 on: April 08, 2021, 06:55:49 pm »

^^^ Looks really good Frank.  I keep myself occupied in the shop as well.  Installed an new HT preamp in the entertainment system rack today.

Pictured are a couple of Rube Goldberg's of mine.

The other one pictured is a fueling station for the generators, ZTR mower etc.  Mounted everything on an aluminum hand truck, 14 gallon tank and hand crank pump.  Fueling up the larger generators is not easy with a 6 gallon fuel can.  The put the fill port right in the center of the fuel tank and it takes 3 hands to do it safely.  Not anymore.

« Last Edit: April 08, 2021, 07:09:55 pm by Steve-White »
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Dave Garoutte

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Re: Campsite Subwoofer (hobby project)
« Reply #2 on: April 08, 2021, 07:09:19 pm »

Do I see a rat guard on the vent?
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Steve-White

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Re: Campsite Subwoofer (hobby project)
« Reply #3 on: April 08, 2021, 07:10:42 pm »

Heater was a problem out on the patio at night for cigar in the winter.  Pulling it close enough to feel the heat was too hot, move it back and heat went straight up.  Solution was to mount a fan on top to blow the warm air across the patio.  Works great.
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Frank Koenig

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Re: Campsite Subwoofer (hobby project)
« Reply #4 on: April 08, 2021, 07:34:05 pm »

Do I see a rat guard on the vent?

Exactly right! A piece of 1/2 in. hardware cloth held on with a hose clamp. It will keep out rats but maybe not mice. I should make the experiment to see if 1/4 in. has any effect on box Q or makes bad noises at high power near fb. 1/4 in. will keep out mice, so far as I know.

Speaking of rodent problems, is there an uptick in wire insulation eating on vehicles? Two of my friends here in town have recently had major damage. Anecdotal, I know. But there could be more rats/mice, or people are driving less due to Covid, or maybe car manufacturers are using tastier insulation?

--Frank
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Frank Koenig

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Re: Campsite Subwoofer (hobby project)
« Reply #5 on: April 08, 2021, 07:53:53 pm »

The other one pictured is a fueling station for the generators, ZTR mower etc.

I need a fueling rig like that for the little rubber-track front-end loader I keep up in the Sierra Foothills. I've been struggling with 5 gal. plastic jugs for years now and just about everything with that arrangement is wrong. The jugs don't vent properly due to some misguided attempt by the manufacturer to comply with newer safety rules. The spout is too short and too weak to rest the weight of the jug on. And the fuel inlet is too high up on the machine. So I huff and puff and curse and dribble diesel all over while milking (alternately squeezing and releasing) the plastic jug to get the fuel out. The last 10% never comes out. Thanks for the inspiration.

--Frank
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Bob Faulkner

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Re: Campsite Subwoofer (hobby project)
« Reply #6 on: April 08, 2021, 09:12:39 pm »

Speaking of rodent problems, is there an uptick in wire insulation eating on vehicles? Two of my friends here in town have recently had major damage. Anecdotal, I know. But there could be more rats/mice, or people are driving less due to Covid, or maybe car manufacturers are using tastier insulation?

--Frank
Yes.  Some auto manufactures are putting "green" components into vehicles.  About 2 years ago, my neighbor had some squirrels chew through his Diesel fuel tank on an F350.  The fuel spill from it (all over his driveway) prompted a slight haz-mat situation, which the fire department came out to asses.  Root-cause-analysis:  the gas tank was soy based.

http://www.synlube.com/IncredibleEdibleCar1.htm


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Riley Casey

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Re: Campsite Subwoofer (hobby project)
« Reply #7 on: April 08, 2021, 09:52:48 pm »

Trying to make an F350 marginally more environmentally friendly, now that's thats some high comedy.


Yes.  Some auto manufactures are putting "green" components into vehicles.  About 2 years ago, my neighbor had some squirrels chew through his Diesel fuel tank on an F350.  The fuel spill from it (all over his driveway) prompted a slight haz-mat situation, which the fire department came out to asses.  Root-cause-analysis:  the gas tank was soy based.

http://www.synlube.com/IncredibleEdibleCar1.htm

Steve-White

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Re: Campsite Subwoofer (hobby project)
« Reply #8 on: April 09, 2021, 01:41:55 am »

I need a fueling rig like that for the little rubber-track front-end loader I keep up in the Sierra Foothills. I've been struggling with 5 gal. plastic jugs for years now and just about everything with that arrangement is wrong. The jugs don't vent properly due to some misguided attempt by the manufacturer to comply with newer safety rules. The spout is too short and too weak to rest the weight of the jug on. And the fuel inlet is too high up on the machine. So I huff and puff and curse and dribble diesel all over while milking (alternately squeezing and releasing) the plastic jug to get the fuel out. The last 10% never comes out. Thanks for the inspiration.

--Frank

I got so pissed off at consumer grade gas cans I put them all in the recycle bin.  Switched to VP racing fuel jugs that I saw the guys using on Street Outlaws.  They work great, hold 6 gallons and come in lots of colors.  The spouts are long and can be easily lengthened to fit need.  I use standard length.  There is a folding handle on the pump that's off of a handwheel on a milling machine, so the hand truck lays on it's back for easy filling.

https://zzdiesel.com/vp-racing-fuels-motorsport-container-round/?pid=12908&utm_source=bing&utm_medium=cpc&utm_campaign=*PDS%20All%20Products%207%2F29%2F2019&utm_term=4576717161145835&utm_content=All%20But%20GM%20and%20Cummins

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Steve-White

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Re: Campsite Subwoofer (hobby project)
« Reply #9 on: April 09, 2021, 01:44:02 am »

I got so pissed off at consumer grade gas cans I put them all in the recycle bin.  Switched to VP racing fuel jugs that I saw the guys using on Street Outlaws.  They work great, hold 6 gallons and come in lots of colors.  The spouts are long and can be easily lengthened to fit need.  I use standard length.  There is a folding handle on the pump that's off of a handwheel on a milling machine, so the hand truck lays on it's back for easy filling.

https://zzdiesel.com/vp-racing-fuels-motorsport-container-round/?pid=12908&utm_source=bing&utm_medium=cpc&utm_campaign=*PDS%20All%20Products%207%2F29%2F2019&utm_term=4576717161145835&utm_content=All%20But%20GM%20and%20Cummins

You did a real slick job on the back plate and amp board mounting and details such as the remote power speakon are great.  It's always worth it building custom to get exactly what ya want.

Again, nice work.
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Scott Holtzman

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Re: Campsite Subwoofer (hobby project)
« Reply #10 on: April 09, 2021, 01:53:47 am »

You did a real slick job on the back plate and amp board mounting and details such as the remote power speakon are great.  It's always worth it building custom to get exactly what ya want.

Again, nice work.


I had a chance to meet Frank and see a few of his projects, not only does he possess mad technical chops but his construction skills and ability to execute on his ideas are inspiring to say the least!

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Scott AKA "Skyking" Holtzman

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Steve-White

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Re: Campsite Subwoofer (hobby project)
« Reply #11 on: April 09, 2021, 03:03:42 am »

^^^ Absolutely Scott - workmanship is top notch without a doubt.  Always nice to see someone with that skill level showing their work.
« Last Edit: April 09, 2021, 03:08:17 am by Steve-White »
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Steve-White

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Re: Campsite Subwoofer (hobby project)
« Reply #12 on: April 09, 2021, 03:08:44 am »

^^^ Absolutely Scott - Frank's workmanship is top notch without a doubt.  Always nice to see someone with that skill level showing their work.
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Craig Hauber

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Re: Campsite Subwoofer (hobby project)
« Reply #13 on: April 09, 2021, 04:01:47 pm »

Exactly right! A piece of 1/2 in. hardware cloth held on with a hose clamp. It will keep out rats but maybe not mice. I should make the experiment to see if 1/4 in. has any effect on box Q or makes bad noises at high power near fb. 1/4 in. will keep out mice, so far as I know.

Speaking of rodent problems, is there an uptick in wire insulation eating on vehicles? Two of my friends here in town have recently had major damage. Anecdotal, I know. But there could be more rats/mice, or people are driving less due to Covid, or maybe car manufacturers are using tastier insulation?

--Frank
Definitely an uptick here, but not because the insulation is any tastier in modern vehicles, my '62 f100 and my 41 international got chewed up really bad this last season and they've been parked in the same quonset-barn for years.  Time to invest in some cats I guess.
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Dave Garoutte

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Re: Campsite Subwoofer (hobby project)
« Reply #14 on: April 09, 2021, 06:21:02 pm »

Definitely an uptick here, but not because the insulation is any tastier in modern vehicles, my '62 f100 and my 41 international got chewed up really bad this last season and they've been parked in the same quonset-barn for years.  Time to invest in some cats I guess.
I saw a video of a guy with a mink and a dog that worked together to clear out rat's nests.  The mink would go inside and chase the rats out and the dog would kill them.
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Scott Holtzman

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Re: Campsite Subwoofer (hobby project)
« Reply #15 on: April 09, 2021, 09:22:09 pm »

^^^ Looks really good Frank.  I keep myself occupied in the shop as well.  Installed an new HT preamp in the entertainment system rack today.

Pictured are a couple of Rube Goldberg's of mine.

The other one pictured is a fueling station for the generators, ZTR mower etc.  Mounted everything on an aluminum hand truck, 14 gallon tank and hand crank pump.  Fueling up the larger generators is not easy with a 6 gallon fuel can.  The put the fill port right in the center of the fuel tank and it takes 3 hands to do it safely.  Not anymore.


That is much nicer than the portable fuel station I have seen on Amazon.  The gas stations is almost a mile from the house so that's a little far to ride the ZTR without attracting a bit of attention.  IIRC it holds over 20 gallons.  I have thought of getting a trailer for it just to fuel it.  That doesn't address the myriad of other gasoline powered devices.  I like it.



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Scott AKA "Skyking" Holtzman

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Steven Cohen

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Re: Campsite Subwoofer (hobby project)
« Reply #16 on: April 10, 2021, 03:23:13 pm »

I got so pissed off at consumer grade gas cans I put them all in the recycle bin.  Switched to VP racing fuel jugs that I saw the guys using on Street Outlaws.  They work great, hold 6 gallons and come in lots of colors.  The spouts are long and can be easily lengthened to fit need.  I use standard length.  There is a folding handle on the pump that's off of a handwheel on a milling machine, so the hand truck lays on it's back for easy filling.

https://zzdiesel.com/vp-racing-fuels-motorsport-container-round/?pid=12908&utm_source=bing&utm_medium=cpc&utm_campaign=*PDS%20All%20Products%207%2F29%2F2019&utm_term=4576717161145835&utm_content=All%20But%20GM%20and%20Cummins

I switched to metal Eagle safety cans. They are air tight so fuel last longer (E0 with Stabil). They also come with a built in flame arrester.
https://www.eagle-mfg.com/safety-cans
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Jeff Bankston

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Re: Campsite Subwoofer (hobby project)
« Reply #17 on: April 10, 2021, 03:27:19 pm »

♫ oooohhhh , dee campsite woofer make dee song woof woof , woof woof , dee campsite woof boom all night long and I dont get no sleep ♫

note > believe me , I did get plenty of rest list night !


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Helge A Bentsen

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Re: Campsite Subwoofer (hobby project)
« Reply #18 on: April 10, 2021, 05:14:17 pm »

IMHO Ze Germans invented the perfect gas can back in the 30's.
https://en.wikipedia.org/wiki/Jerrycan

I use these when needed.
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Dave Garoutte

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Re: Campsite Subwoofer (hobby project)
« Reply #19 on: April 10, 2021, 06:01:45 pm »

IMHO Ze Germans invented the perfect gas can back in the 30's.
https://en.wikipedia.org/wiki/Jerrycan

I use these when needed.
The only can I had back in my racing days.
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Nothing can be made idiot-proof; only idiot resistant.

Events.  Stage, PA, Lighting and Backline rentals.
Chauvet dealer.  Home of the Angler.
Inventor.  And now, Streaming Video!

ProSoundWeb Community

Re: Campsite Subwoofer (hobby project)
« Reply #19 on: April 10, 2021, 06:01:45 pm »


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