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Old 1st June 2010, 12:29 AM   #1
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Default Building a Bass SS amp out of a old car subwoofer...need advice!

Hello All,

So this is what I have to work with:

An Infiniti Reference Series 12inch Automotive Subwoofer Model# 1230W. It has power handling of 1200W peak power, and 300W RMS.

Also, I have a Rampage by Audiovox AMP-592C 200 Watt Stereo Power Amplifier that runs off 12 volts D.C. (I don't know if I can use this at all for this project.)

I originally had it in my last car, however, it has been sitting in my garage in a custom enclosure for a LONG time because the original setup never really worked well.

Either way, I would love to make a bass amplifier out of it if possible. This would be my first custom amp project and I honestly have no idea of where to start. It is a solid state speaker so I think I will stick with a SS amp for ease of build and ease on my wallet. Also, I will build a custom enclosure for this project.

Anybody have ANY ideas?

Thanks in advance!
-John
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Old 1st June 2010, 01:44 AM   #2
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John:
Are we talking about a Bass amp as in a Bass guitar??
First off Bass guitar amps are by and large driven by tubes. There are a zillion reasons why tubes are used in this application but I won't get into that right now.
I would think your best approach would be to get that amp up & running so you can see where you might go with it...& to experiment with. Besides having a high power 12VDC supply is nice to have for any other "car" equipment.
Your choices are a "linear" PS or the 'new' generations of Switched Mode Power Supply....or SMPS. While SMPS' are quite the rage now, old-style linear supplies have their merits as well.
Check the fuse rating on your amp & start looking for a 12VDC SMPS for that rating. SMPS' are really kinda cheap & I think it would be your best bet at this stage.



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Old 1st June 2010, 02:47 AM   #3
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Quote:
Originally Posted by Richard Ellis View Post
John:
Are we talking about a Bass amp as in a Bass guitar??
First off Bass guitar amps are by and large driven by tubes. There are a zillion reasons why tubes are used in this application but I won't get into that right now.
I would think your best approach would be to get that amp up & running so you can see where you might go with it...& to experiment with. Besides having a high power 12VDC supply is nice to have for any other "car" equipment.
Your choices are a "linear" PS or the 'new' generations of Switched Mode Power Supply....or SMPS. While SMPS' are quite the rage now, old-style linear supplies have their merits as well.
Check the fuse rating on your amp & start looking for a 12VDC SMPS for that rating. SMPS' are really kinda cheap & I think it would be your best bet at this stage.



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Rick,

Thanks for the input. Yes, I am talking about building a Bass guitar amplifier. I did some more research into the parts that I have and I have determined that I would need a higher power amplifier for that Infinity speaker because I would need some additional speakers in the enclosure to have a broader frequency response. Here are the specs of the speaker:

12" 4-ohm subwoofer
polypropylene cone with rubber surround
deep-draw I-beam basket
70-ounce magnet structure
recommended power range: 50-300 watts RMS (1,200 watts peak power)
frequency response: 23-400 Hz
sensitivity: 90 dB

Also, here are the specs for the car amplifier I listed before:
Maximum Output Power: 100 watts x 2 @ 4 ohms
Output Power @ 0.1% T.H.D.: 60 watts RMS x 2
Output Impedance: 2 - 8 ohms
Frequency Response: 10 - 50,000 Hz. 1 dB
Channel Separation: 50 dB
Signal / Noise Ratio: 90 dB (A-Weighted)
Input Impedance: low-level 10K ohms, high-level 100 ohms
Input Sensitivity: low-level 200 mv. - 2 v., high-level 2 - 10 v.
Filter Type: low-pass
Filter Slope: 12 dB/octave
Filter Crossover: 50 - 250 Hz. (selectable)
Supply Voltage: 12 volts, negative ground
Fuse Rating: 10 amps.
Dimensions (W x H x D): 12-1/4" x 2" x 6-1/8"

I have looked into some amplifiers and power supplies, however, there is so much out there...I am not sure what would be good for my application. If I do go with that amplifier, it might be sufficient to run the other speakers I will need, however, it will not be sufficient to amplify the whole setup. I am going to search my garage for the rest of my car audio equipment so that I can get a wider frequency response from this project amp. I will post again with the specs of any other car audio speakers I have on hand.

Again, thanks for the input!
-John
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Old 1st June 2010, 04:29 AM   #4
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John,
You do have more than enough power with that amp.quite literally to rock the house down.....Here ya go, Most "bass guitar" speakers are WAY more efficient than your car drivers...Look up Parts-Express.com - Speakers, Speaker Building, Home Audio and Video, Pro Audio, Electronic Parts & Accessories PARTS EXPRESS, Speakers, Speaker Parts, Guitar speakers, Bass speakers, Woofers, Drivers, speaker upgrades and replacement speakers. Emine & select 12" "Bass guitar speakers"
Your could run a stack of four 12" babies in a basic open back enclosure...& with that kinda power really get on the bad side of your neighbors!
Yes indeed your car drivers are not suited for musical work.
Keep lookin' for your PS module & let us know which you select...& we'll talk about it.
From there, we need some sort of pre-processor to get you the tonal qualities & effects that are needed for guitar work.

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Old 1st June 2010, 04:39 AM   #5
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Kinda like a pair of these..at eight ohms your amp will be delighted its not working hard at all.

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Old 3rd June 2010, 02:27 AM   #6
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Quote:
Originally Posted by Richard Ellis View Post
John,
You do have more than enough power with that amp.quite literally to rock the house down.....Here ya go, Most "bass guitar" speakers are WAY more efficient than your car drivers...Look up Parts-Express.com - Speakers, Speaker Building, Home Audio and Video, Pro Audio, Electronic Parts & Accessories PARTS EXPRESS, Speakers, Speaker Parts, Guitar speakers, Bass speakers, Woofers, Drivers, speaker upgrades and replacement speakers. Emine & select 12" "Bass guitar speakers"
Your could run a stack of four 12" babies in a basic open back enclosure...& with that kinda power really get on the bad side of your neighbors!
Yes indeed your car drivers are not suited for musical work.
Keep lookin' for your PS module & let us know which you select...& we'll talk about it.
From there, we need some sort of pre-processor to get you the tonal qualities & effects that are needed for guitar work.

__________________________________________________ __________Rick.......
Rick,

I took a look at that website and there is a plethora of speakers there....however, they are a bit pricey for me at the moment. I did manage to find two other car speakers in the garage. I could not find any info about them online, but this is what is listed on the magnet (word for word):

IDI
40 oz Magnet Circuit
Model No: 694
Size: 6" x 9" +3" +2" + 1"
Impedance: 8 OHM
Power: 200W (100W + 100W)
Made in Taiwan
R.O.C.

I have two of them, and the last time I knew, they were working. The 6" x 9" +3" +2" + 1" refers to a main 6x9 woofer with three tweeters sitting in front of it with respective sizes listed above.

Now, if I got a separate amplifier for either these or the woofer and ran it all with the same input, do you think it would be feasible as a bass guitar amp (with the proper inputs and equalizing and PS, etc)?

Also, I was wondering what your thoughts were on using a computer power supply as the PS for this project. I have a couple laying around and they are cheap and readily available online. They all have +12V rails that have different amperage running through them. One of the PS I have has a +12V rail with 15A running through it. If I hooked up the amp I have to an isolated +12V through a modified Molex connector (isolate the +12V rail and disconnect the +5V rail), would I blow the 10A fuse that the amp has? Would I need to get a PS that has 10A on the +12V rail?

Again, I am trying to get away as cheap as possible. I know this typically limits projects a great deal...but this is also half the fun!

And again, thanks for all the input!
-John
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Old 3rd June 2010, 05:51 AM   #7
ChrisA is offline ChrisA  United States
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Quote:
Again, I am trying to get away as cheap as possible. I know this typically limits projects a great deal...but this is also half the fun!

Even if it only cost you $20 if the amp can't do the job that is $20 wasted.

First off a bass guitar, assuming here it is a four string and you use standadrd tuning, has a rage of about 40Hz to 8KHz. There is no need to handle aything outside that range.

The nest thing to know is that a guitar amp is ANYTHING BUT a HiFi. You design them intentionally to distort just a little. Bass amps are cleaner than guitar amps. But still they "color" the sound.

Much of that color comes from your choise of speaker. A lot of them are mid scooped to kill the mids (kind of anti-hifi)

That sub woofer that goes from 20Hz to 400 would be a disaster because you have to crossit over right at about middle C or just below. NEVER d a speaker crossover right in the middle of an instrument's range. You have a pretty noticable change in tinbre right thee at the first note above the bass cleff.

Get a speaker that can do the job.

OK go one? now you can figure out how big the amp needs to be. Contrary to what was said today many bas players use SS amps simply because a 500W tube amp is a monster. You can use any very clean and powerfull SS amp you have. Look at the RMS watts and go for about 250W.

Now we get to the part you have to build - the preamp. This is what you plug the guiter ito and what drives the line level signal into the SS power amp. Build this with TUBES. It's cheap because a preamp does not need an output transformer and you can run 12AX7 tubes on 250V and you can get that from a $25 Edcor power transfoormer. YOu only need a few milliamps of curent at 250 volts. Maye a 12ax7 and 12au7 and a tone stack. Do two
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Old 3rd June 2010, 07:23 AM   #8
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Here's a thought for you.

You could buy a faulty bass amp off ebay. If you fix it, you've got a power amp, a pre-amp, and a speaker. You could make your own cab. If you can't fix it, you'll get a power transformer, and a pre-amp (pretty much guaranteed - if a transistor blows, it can take the speaker with it).

faulty Marshall 5506 Bass 60 guitar amplifier amp on eBay (end time 04-Jun-10 22:42:41 BST)
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Old 5th June 2010, 06:46 PM   #9
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Hello all,

I just wanted to give an update on this project. After reading all of your comments and taking into consideration all that would be involved with making a bass guitar amp, I decided to re-think the project. I have decided to create what the subwoofer was designed to do...be a subwoofer.

This is what I have accomplished thus far:
I "hot-wired" a 300W computer power supply by wiring the green "power on" line to a black ground on the 20-Pin motherboard connector. This PS supplies +12VDC with 300W maximum power with a 15A rating on the +12VDC rail.

Next, I modified two Molex 4-pin connectors so that one only outputs the +12V rail and the ground and the other only outputs the +12V rail. The first one supplies the power and the ground for the amp and are connected to the "Batt" and "Gnd" terminals respectively. The second molex supplies 12V to the remote terminal essentially telling the unit to turn on. I had issues with the unit turning on before I supplied 12V to this terminal.

After that, I bridged the two output terminals of the amp and connected them to the sub. I plugged in the PC power supply and on came the whole setup. I used a headphone to RCA adapter to plug in the amplifier to my laptop and ran some tunes through it and boy did it thump!

So, at this point, I have abandoned the idea of creating a bass guitar amp and I am going to move forward to make a subwoofer for my home stereo system (something I have always wanted).

There are two questions that I still have: The amplifier only has a Right & Left RCA input and my home theater receiver (an Onkyo TX DS474) has a single RCA output for the subwoofer connection. Can I simply use a 2-to-1 RCA connector to connect these two components? Do I need to build some type of adapter for this project?

Secondly, what is the best material to use for the sub enclosure? I was planning on using some 1/2" or possibly 3/4" sanded BC plywood for this project. Is there something that would be better for this application? The enclosure will be about 16" square for the actual sub box and then have a 16"W x 16"D x 3.5"H for the amp and PS enclosure that will be on top of the sub box.

I want to thank all of you for your input on this matter. This is turning out to be quite the successful project. I will post pictures of the enclosure and the project so that you guys can see the completed project!

Thanks again for all the help!
-John
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Old 5th June 2010, 08:00 PM   #10
AndrewT is offline AndrewT  Scotland
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Hi,
before you start designing the speaker box, you need more information about your driver.
Do you have the T/S parameters?
or can you measure the T/S parameters?
or do you have a friend who could measure the T/S parameters for you?

Without them you are guessing.
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