MAME Arcade Game cabinet audio upgrade

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Orcish75

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Hi Everyone,

This is a bit different from the usual audio DIY stuff, I don?t think many people have done this before. I bought a couple of arcade machines a few years ago from someone who had closed their gaming business. This was before the current ?Retro? craze hit the scene, where vintage computers, consoles and arcade machines are selling for stupid prices. I?ve been working on the arcade machines on and off, setting up old Core 2 Duo PCs with MAME and replacing the image burnt CRTs with CRTs scavenged from old TVs. Replacing the joysticks and buttons with new ones that haven?t been smashed into oblivion.

The other area that was in desperate need of an upgrade was the audio. Most arcade machines had a TDA1517 or equally pathetic amp chip driving a mono 2W speaker. To say they sounded like a budgie trying to sing Nessun Dorma would be kind. They really sucked! The nice thing with arcade cabinets is that there?s lots of space in them to add a reasonable sound system. I picked up a couple of 10? woofers and two sets of Pioneer 4? two-way speakers from a cash and carry shop for the bargain price of R240 for the woofers and R300 for the Pioneers. Sure, they?re not gonna give Sonus Faber a run for their money, but for this application, they?re perfect.

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Of course I had to do the obligatory speaker run-in, (well, not really necessary in this case, but did it anyway) ran a 35Hz sine wave through the woofers for about 150 hours to loosen up the surrounds and spiders.

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Bought a couple of 4 channel car amps from Cash Converters, made sure they were bridgeable and had adjustable low pass and high pass filters.

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One thing I really didn?t think about when I bought the speakers was that the arcade machines had CRTs. When I started to do the measurements to fit the Pioneers, I realised how close they would be to the CRT and they weren?t magnetically shielded. I really didn?t want the screen image to look like something out of My Little Pony so I had to make a plan. Enter the baked bean can!

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Couldn?t believe my luck how perfect the size was! I cut both sides of the can about 25mm from the edge and then applied 5mm thick double sided tape to the back of the magnet on each speaker. I then made four 6mm thick cardboard shims to get the speaker in the middle of the can. It was quite a challenge as the magnets are stronger than you think. Eventually I got it right on both speakers and then pushed down on the speaker so that the double sided tape bonded nicely to the tin.

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Looks really ghetto, doesn?t it!  :giggle:

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The tin cans worked really well, I?d say subjectively, it about halved the magnetic attraction if I brought the magnets of the two speakers together.
Next, I drilled out the holes for the Pioneers with a hole-saw and mounted them.

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Now it was the woofer?s turn to be mounted. I marked out where the hole was to be cut. For the OCD types, don?t worry, my measurement was dead centre, all those small holes were drilled off centre by the previous owner.

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Cut out the hole with a jigsaw and mounted the woofer.

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Slapped on a protective grill to prevent speaker damage.

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Built a box for the woofer to improve the sound.

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Then finally, mounted and wired up the speakers to the amp. I bridged the two rear channels of the amp and activated the low-pass filter to drive the woofer. I set the cross-over to around 150Hz as that?s about where the Pioneers start becoming audible. I connected the Pioneers to the two front channels and activated the high-pass filter and set the crossover to about 150Hz. Anything below that is barely audible on the Pioneers as they?re such small speakers.

I connected the power terminals of the amp to the PCs power supply. I used the 6-pin 12V connector on the PC power supply that?s normally used for graphics cards to power the amp. The power supply can push out about 20 amps on that connector so it?s more than enough current to power the amp. I?m not going to be listening to arcade game music and SFX at ear splitting levels anyway!

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All I can say is what a massive improvement in sound quality! Granted, most arcade game jingles are tinny and crappy to begin with, but this still made a huge improvement. It?s certainly not audiophile level by any means, I didn?t bother with damping material for the woofer or add a reflex port, (I may still do this at a later stage) and used the mediocre on-board soundcard of the PC. The main thing is that there was a huge improvement and that made the effort worthwhile.

Even my 4 year old son was commenting on how cool the explosions were when he was playing Metal Slug!

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There?s still a ton of other work to do on this cabinet, but I just wanted to show the audio upgrade on something a bit different from most of the builds on AVForums.



 
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