scratch built shop stereo

[Jon Jacobs]

Hi Guys, I decided to re-purpose my car stereo after my vehicle met an untimely demise last new years when a lady pulled in front of me and totalled my car.

The insurance company agreed to let me keep the stereo which consisted of the deck, 2 amps, surius receiver, 4 speakers and a sub-woofer. ( it came with the car, im too old for that bs ).

I have a shop which I put 6 speakers in the ceiling, the large amp will run the ceiling speakers and the smaller amp will run the two speakers in the unit I built.

Just putting the finishing touches on the frame before it goes for powder coat.

I used an old computer power supply to convert from 110 ac to 12v dc.

The entire project was built from leftover materials I had around the shop.

Once I get it painted I will post a few more pics.

It weighs a ton. I call it my heavy metal stereo. Pun intended.

 

[exmaxima1]

As a professional speaker engineer, my first impressions are that there appears to be alot of potential air leakage in that design. If the rear waves of the speakers meet the front waves, you get cancellation---loss of sound. In your case it will be total loss of bass, but you should still get plenty of highs and upper mid frequencies.

Sure looks purdy. Very nice work!

 

[simpler=better]

It looks great!

but you are going to need to put some kind of baffle around the rear of each speaker if you want it to sound right.

 

[txvwnut]

Really cool, great idea and execution. But like the others have you should, if you haven't or have planned to, baffle the back of the speakers.

 

[csp]

Is the computer power supply going to be on all the time so that you don't lose any presets or the time on the clock?

 

[930dreamer]

Nice fab work for the shop stereo.

 

[HOTFR8]

I did something similar years ago with an old AM radio single speaker in a wooden box. You have put a lot of time and work into that.

 

[neonnblack]

That looks sweet. Nice job.

 

[brianh]

Thats really nice, you could fab some nice aluminum speaker boxes damped with foam rubber.

Love the industrial look

 

[Jon Jacobs]

Thats really nice, you could fab some nice aluminum speaker boxes damped with foam rubber.

Love the industrial look

Thanks ! Good idea.

 

[Jon Jacobs]

That looks sweet. Nice job.

Thank you. : )

 

[Jon Jacobs]

I did something similar years ago with an old AM radio single speaker in a wooden box. You have put a lot of time and work into that.

Thank you, I have about 20 hrs in it I would estimate.

 

[Jon Jacobs]

Nice fab work for the shop stereo.

Thank you. I built the box 1st then started to mock up where the pieces would fit.

 

[Jon Jacobs]

As a professional speaker engineer, my first impressions are that there appears to be alot of potential air leakage in that design. If the rear waves of the speakers meet the front waves, you get cancellation---loss of sound. In your case it will be total loss of bass, but you should still get plenty of highs and upper mid frequencies.

Sure looks purdy. Very nice work!

Hi thanks. This is what happens when you do electrical in a machine shop. My degree is in mechanical, but you make a good point. It sounds good but I think I will make some lexan dividers for the speakers.

 

[Jon Jacobs]

Really cool, great idea and execution. But like the others have you should, if you haven't or have planned to, baffle the back of the speakers.

Thank you. Theres a surplus store here that sells stereo odds and ends. I may take a look see what they have.

 

[Jon Jacobs]

Is the computer power supply going to be on all the time so that you don't lose any presets or the time on the clock?

Good point, I am looking into a battery back up. Not sure yet.

 

[longlivepunk]

Hey Jon, glad to see a new post from you! How's the shop doing? That stereo looks awesome (at least to a guy with only AM/FM in his truck [emoji14] )

Sent from my B15 using Tapatalk

 

[Jon Jacobs]

Hey Jon, glad to see a new post from you! How's the shop doing? That stereo looks awesome (at least to a guy with only AM/FM in his truck [emoji14] )

Sent from my B15 using Tapatalk

Hi, thanks. The shop is coming along slowly as time permits. The property also has a duplex on it that ended up needing a total reno.

My dad got sick too which slowed down the progress of the shop.

I have almost finished the insulation and new lighting, I will start a new thread of some before and after pics son, Best Jon.

 

[kbs2244]

Leveling screws on the feet?
There does look to be room for a turntable.

 

[DHCrocks]

how many watts is the power supply can it handle the two amps?

for the ceiling speakers assuming they are 8 ohms and you run in parallel to a 2ch amp that will put 3 speakers on each channel for a total load of 2.67 ohms. check to be sure the amp can drive a 2 ohm load.

 

[dogdog]

Curious why would the insurance company have to give you permission to have any sort of radio in your shop?

 

[Model A Fan]

Curious why would the insurance company have to give you permission to have any sort of radio in your shop?

"Canada".

 

[csp]

Curious why would the insurance company have to give you permission to have any sort of radio in your shop?

The insurance company let the OP pull the stereo out of a vehicle that they deemed to be totaled.

It had nothing to do with permission for a radio in the shop.

 

[Dick in Wisconsin]

You have lots of room to add more things like a scanner, weather radio receiver, maybe a CB, WiFi repeater, a bunch of different color LEDs, digital voltage and amp meters, outside air temp indicator, etc.

A truly Mil Spec shop radio.

Great job!

 

[Jon Jacobs]

how many watts is the power supply can it handle the two amps?

for the ceiling speakers assuming they are 8 ohms and you run in parallel to a 2ch amp that will put 3 speakers on each channel for a total load of 2.67 ohms. check to be sure the amp can drive a 2 ohm load.

Let me get back to you on that. Good point. The power supply says 240 watts. I will check the boxes the roof speakers came in. They're 5" marine speakers. I wired up he amps today but the light became dim under load. The schematics call for a capacitor for the amps which I don't have.

 

[Jon Jacobs]

You have lots of room to add more things like a scanner, weather radio receiver, maybe a CB, WiFi repeater, a bunch of different color LEDs, digital voltage and amp meters, outside air temp indicator, etc.

A truly Mil Spec shop radio.

Great job!

Thanks, Im thinking phone charger at least....

 

[gahrajmahal]

Back in my groovy van customizing phase all the shops I worked in had a similar setup. An old car takeout radio mounted in a panel and speakers in wood boxes balanced in the ceiling. Rock on!

 

[Jon Jacobs]

Back in my groovy van customizing phase all the shops I worked in had a similar setup. An old car takeout radio mounted in a panel and speakers in wood boxes balanced in the ceiling. Rock on!

I had a young co-op student working with me for the summer, it was a great exercise.

 

[DHCrocks]

Let me get back to you on that. Good point. The power supply says 240 watts. I will check the boxes the roof speakers came in. They're 5" marine speakers. I wired up he amps today but the light became dim under load. The schematics call for a capacitor for the amps which I don't have.

on the power supply there should be a sticker showing the different voltage rails and the maximum current for each. if the total power is only 240 watts the 12 volt rails will be less maybe around 16A or so. it would be too small. you can easily drive the head unit which alone but pushing two additional amplifiers will be a stretch, on very low volume it should work ok but at higher volumes you will be drawing too much current and the voltage will dip and likely burnout your power supply.

assuming 16A that is 192watts at 12volts. Since you have old school gear (class AB) the efficiency of the amplifiers is probably around 50% so that means the total output would be about 96watts (50% of 192w) given the supply you have. if your amplifiers are rated more then this then you don't have enough juice for them.

A simple way to estimate your power requirements would be to add up all the fuses for the total maximum current draw. say you need 100A total, at 12 volts that would be 1200 watts (P=VI, 12v x 100A = 1200W).


on the speakers, I think marine speakers are similar to car audio in that they use 4 ohm speakers. if this is the case your looking at 1.33 ohms in parallel which is pretty low and a lot of lower end amplifiers can't drive that low a load. if you run them in series you will have 12 ohms which is no problem for the amplifier but you will sacrifice quite a bit of volume, but it would be the safer way to go.


list the specs of what you got and we can go from there to determine the best setup.

 

[Jon Jacobs]

on the power supply there should be a sticker showing the different voltage rails and the maximum current for each. if the total power is only 240 watts the 12 volt rails will be less maybe around 16A or so. it would be too small. you can easily drive the head unit which alone but pushing two additional amplifiers will be a stretch, on very low volume it should work ok but at higher volumes you will be drawing too much current and the voltage will dip and likely burnout your power supply.

assuming 16A that is 192watts at 12volts. Since you have old school gear (class AB) the efficiency of the amplifiers is probably around 50% so that means the total output would be about 96watts (50% of 192w) given the supply you have. if your amplifiers are rated more then this then you don't have enough juice for them.

A simple way to estimate your power requirements would be to add up all the fuses for the total maximum current draw. say you need 100A total, at 12 volts that would be 1200 watts (P=VI, 12v x 100A = 1200W).


on the speakers, I think marine speakers are similar to car audio in that they use 4 ohm speakers. if this is the case your looking at 1.33 ohms in parallel which is pretty low and a lot of lower end amplifiers can't drive that low a load. if you run them in series you will have 12 ohms which is no problem for the amplifier but you will sacrifice quite a bit of volume, but it would be the safer way to go.


list the specs of what you got and we can go from there to determine the best setup.

Awesome, thanks so much, I am no audio file. I will collect the data and hopefully you can help me out here, I already sent the frame for paint. Talk soon.

 

[Jon Jacobs]

on the power supply there should be a sticker showing the different voltage rails and the maximum current for each. if the total power is only 240 watts the 12 volt rails will be less maybe around 16A or so. it would be too small. you can easily drive the head unit which alone but pushing two additional amplifiers will be a stretch, on very low volume it should work ok but at higher volumes you will be drawing too much current and the voltage will dip and likely burnout your power supply.

assuming 16A that is 192watts at 12volts. Since you have old school gear (class AB) the efficiency of the amplifiers is probably around 50% so that means the total output would be about 96watts (50% of 192w) given the supply you have. if your amplifiers are rated more then this then you don't have enough juice for them.

A simple way to estimate your power requirements would be to add up all the fuses for the total maximum current draw. say you need 100A total, at 12 volts that would be 1200 watts (P=VI, 12v x 100A = 1200W).


on the speakers, I think marine speakers are similar to car audio in that they use 4 ohm speakers. if this is the case your looking at 1.33 ohms in parallel which is pretty low and a lot of lower end amplifiers can't drive that low a load. if you run them in series you will have 12 ohms which is no problem for the amplifier but you will sacrifice quite a bit of volume, but it would be the safer way to go.


list the specs of what you got and we can go from there to determine the best setup.

Hi, I have the information you requested, Please review data and give me your thoughts.

The 2 amps have a 25 amp and 20 amp fuse , but no data on the unit. The larger takes the 25 amp.

I have attached a photo of the power supply to discern if it will do the job.

Originally the smaller amp ran the sub woofer which I am not using but rather the 2 grill speakers in the unit.

I copied the ceiling speaker data directly from the vendors website:

• 5.25-inch dual cone full-range speakers
• 50 Watts peak per speaker
• Completely waterproof
• For marine or car use
• Polypropylene cone with cloth surround
• Built-in molded grill
• Molded ABS plastic basket
• 20 Ounce circuit magnet
• Frequency response: 100Hz - 18k Hz
• 4 Ohms impedance

Also I have a wiring diagram of the original install.

Any information you could offer would be greatly appreciated,

 

[DHCrocks]

first off you're screwed, that power supply only outputs 9.5A @ 12v. much to little, it is enough to drive your head unit only. need to find a bigger power supply. You can temporarily hook up the 4 speakers to the head unit until you can get a bigger one. if your head unit has speaker level outputs you can temporarily hook up 4 speakers (left/right+front/rear) and not use an amp.



once you get the power supply sorted out heres how I would hook up the speakers.
MRP-F240 is 40wx4ch (4ohm) / 50wx4ch (2 ohm)
MRP-T220 is 50wx2ch (4ohm) / 70wx2ch (2 ohm)

hook up your pair of speakers on the rack to two channels on the MRP-F240 (40w each speaker)

hook up one pair of ceiling speakers to the other two channels on the MRP-F240 (40w each speaker)

hook up two pairs of ceiling speakers in parallel to the MRP-T220 (35w each speaker - since 70w per channel and they are in parallel.)

this should give you the best balance.

 

[Dick in Wisconsin]

Thanks, Im thinking phone charger at least....

Multiple powered USB ports should be easy. I'd put toggle switches on each one with a LED to show when the respective port is powered up or powered down.

 

[Jon Jacobs]

first off you're screwed, that power supply only outputs 9.5A @ 12v. much to little, it is enough to drive your head unit only. need to find a bigger power supply. You can temporarily hook up the 4 speakers to the head unit until you can get a bigger one. if your head unit has speaker level outputs you can temporarily hook up 4 speakers (left/right+front/rear) and not use an amp.



once you get the power supply sorted out heres how I would hook up the speakers.
MRP-F240 is 40wx4ch (4ohm) / 50wx4ch (2 ohm)
MRP-T220 is 50wx2ch (4ohm) / 70wx2ch (2 ohm)

hook up your pair of speakers on the rack to two channels on the MRP-F240 (40w each speaker)

hook up one pair of ceiling speakers to the other two channels on the MRP-F240 (40w each speaker)

hook up two pairs of ceiling speakers in parallel to the MRP-T220 (35w each speaker - since 70w per channel and they are in parallel.)

this should give you the best balance.

Yup, as I was collecting information for you it became obvious the power supply was insufficient.

I visited a local computer supply store and purchase a 500W gaming power supply with 25 and 20 amp rails.

I am still trying to figure out which rails produce the highest amperage.

I was hoping I could use the smaller amp to run the 2 grill speakers and the larger one to run the 6 in the ceiling.

Is this a bad idea based on your calcs ?

I have the speakers daisy chained together ( left and right sides ), I could pull out the wiring but it would be a pain.

I was also going to put an on / off switch for the smaller amp as I wouldn't use it often, but I get your logic on splitting up the speakers.

Let me know your thoughts, Cheers

 

[Jon Jacobs]

Multiple powered USB ports should be easy. I'd put toggle switches on each one with a LED to show when the respective port is powered up or powered down.

Agreed, I stopped at my local car parts supplier and picked up a toggle for the smaller amp, still a novice at this point.

Wisconsin rocks btw, all my relatives are in Cudahy and Madison.

 

[DHCrocks]

the setup i gave would give the most even power distribution to all speakers.

you could hook up the 2ch amp to the grill speakers and they would get 50w each.

by daisy chaining, do you mean in series? (+)speaker1(-) to (+)speaker2(-) to (+)speaker3(-) if this is the case you will have a 12ohm load. you can bridge the 4ch amp to 2 channels and run it like that.

if you did parallel, positive of all speakers together and negative of all speakers together you will have a 1.3ohm load which your amp can not drive. you would need to rewire this.

probable the best solution to use the overhead speakers on just the 4ch amp would be to hook up a single speaker to channels 1&2 and a pair parallel to channels 3&4. channels 1&2 would get 40w to each speaker. Channels 3&4 would get 50w each. but each speaker would only see 25w, so it will be a bit softer. you can adjust the gain on the amp to compensate to balance out the sound levels.


using an on/off switch is a great idea, just be sure you do it on the remote turn on wire and not the power wire.

 

[hotdogstand]

You *should* be able to run a small 12v battery (think UPS or ATV) and maybe a larger car-audio capacitor to smooth out the demands on the power supply. I have an anchor audio PA that I converted into a "boom box" by swapping out the receiver with a Bluetooth head unit. It has two power supply batteries I salvaged from a server UPS to run it when it's not plugged in, but is still deafeningly loud. The bass is decent, but it isn't really equipped for a low frequency kick being that it was originally a PA.

 

[Jon Jacobs]

You *should* be able to run a small 12v battery (think UPS or ATV) and maybe a larger car-audio capacitor to smooth out the demands on the power supply. I have an anchor audio PA that I converted into a "boom box" by swapping out the receiver with a Bluetooth head unit. It has two power supply batteries I salvaged from a server UPS to run it when it's not plugged in, but is still deafeningly loud. The bass is decent, but it isn't really equipped for a low frequency kick being that it was originally a PA.

What would you recommend for a battery to maintain presets ?

 

[Jon Jacobs]

the setup i gave would give the most even power distribution to all speakers.

you could hook up the 2ch amp to the grill speakers and they would get 50w each.

by daisy chaining, do you mean in series? (+)speaker1(-) to (+)speaker2(-) to (+)speaker3(-) if this is the case you will have a 12ohm load. you can bridge the 4ch amp to 2 channels and run it like that.

if you did parallel, positive of all speakers together and negative of all speakers together you will have a 1.3ohm load which your amp can not drive. you would need to rewire this.

probable the best solution to use the overhead speakers on just the 4ch amp would be to hook up a single speaker to channels 1&2 and a pair parallel to channels 3&4. channels 1&2 would get 40w to each speaker. Channels 3&4 would get 50w each. but each speaker would only see 25w, so it will be a bit softer. you can adjust the gain on the amp to compensate to balance out the sound levels.


using an on/off switch is a great idea, just be sure you do it on the remote turn on wire and not the power wire.

Ok, sounds excellent, I just picked up the frame from powder coaters and I am going to tackle the wiring as per your instructions.

I am planning on checking the amperage under load once I get it wired up.

If its ok with you I may message you directly, Thanks for all your help on this. It proved to be a bigger endeavour than I had anticipated.

 

[Jon Jacobs]

Frame back from painters. I am pleased.