How big of a speaker can you fit in a Spike2 backbox? If there's room for 6x9's...

Not Spike2, but related:

I modified a DCS board with a filter enable switch for the backbox. Stock speakers sound much better with it disabled, expect full range speakers to perform better when provided with a full range signal.

If you are really serious about audio and using a DCS board, populate the audio-out header and run that signal to an amplifier. Turn the in-game audio up to the high 50's. These machines use digital attenuation, so the higher the volume the fewer bits getting truncated off the signal.

Depends on the amplifier's ability to scan for devices.

You need to do a line-out mod then plug that into a transmitter, and find a way to get 5V to it.

This is easier on systems that don't have digital audio control, such as System 11. On those you can pull the audio signal off the volume control.

Working on upgrading the audio on my homebrew game's WPC cab. Similar setup to what you guys are running: custom speaker panel for 6.5" speakers, 6.5" sub in the cabinet, Lepai LP-168HA amplifier.

Replaced some Pyle Blue 3-Ways with Rockford Fosgate Punch 2-ways. There was no comparison with the A/B test. The Pyles are muddy and have a completely different frequency response curve. The RF's are very clear and you can hear how much detail was being lost by the Pyles.

A couple issues I need to resolve with the RFs:
-The treble on them is razor sharp and the midrange is lacking. Thinking of adding a 7-band EQ before the amp, not sure how else to fix this.
-The foam surround on the RF's is wider than the Pyles, so I need to add 1/4" spacer ring to rear mount them. Haven't found the right size yet. Maybe use dense rubber weatherstripping?

$200 for an amp and cables to drive $20 Pyle speakers. Makes sense.

That amp looks interesting... thanks for giving the current draw.

Since it's running off a switching power supply, I wonder if adding a big capacitor on the 12V would help the amp.

It was night and day when my homebrew got capacitors on the coil power.

Spend the extra money for something like a Meanwell.

I had one of these fail due to vibration. It's your typical cheaply made PS. Don't mount it next to a subwoofer, lol.

Yes, that specific mfg & model.

The subwoofer next to it was going pretty hard at the time it failed, and you could hear something rattling around inside after it was pulled.

Added a 9-band EQ, much better. Need to scope out the signal path to make sure I'm not clipping anywhere.

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You are correct.

This might be the best sounding stereo I have.

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2" tweeter and 5.25" midrange. Haven't been able to dig up any info on the OEM of the speakers, which tells me they're generic and could benefit from an upgrade. If they were good speakers they'd be included in the advertising.

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Bench testing a Wuzhi Audio ZK-TB21 amp kit. Under $30, 5 minutes to assemble.

Initial observations:
BT works fine but no way to disable it. Don't use this model if you plan on taking your machine to shows.
Operates down to 5V.
Signal sounds clean through BT.

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Since there's a lot of acoustics knowledge in this thread...

If you were to add a subwoofer to a cabinet that doesn't have a cabinet speaker, where would you place it: behind the coinbox area or near the rear of the cab? Any benefit to porting the cab like Data East?

Bass-heads: Any trick to anti-rattle tape? Just stick it where needed?

Put a couple strips of painters tape at the top of the glass where it was rattling, there's a spot on the side that's noisy as well.

Should I be looking into replacing the glass guides under the rails?

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I ended up going with a Lepai 168HA in my System 1 build because it's the only 2.1 channel amp I've found that doesn't have bluetooth. The last thing I need is some kid pairing his phone to my game at a show and playing something inappropriate. I'm sure it could be disabled by lifting a pin or cutting a trace between the BT chip and amplifier but I haven't looked into it yet.

Anyway, this review on Parts Express is super interesting but haven't found a complete writeup elsewhere on the web. The sub output is clipping hard almost immediately... how did Spooky ever manage to use this amp in TNA? Going to try the subwoofer distortion fix and see what I can figure out.

Reasonalbe low power stereo amp. Forget the subwoofer ouput.
WARNING – The outputs are all BTL (Bridged Transformer Less). This means that no outputs of the left, right, and subwoofer channels are common and MUST NOT BE EXTERNALLY CONNECTED TO EACH OTHER. Doing so will cause excess heating and distortion and may destroy the amplifier.

My intended use of this amplifier is for my bedroom TV. The TV has no external speaker connectors but it does have volume controlled line level outputs and the ability to turn off the internal speakers. This amplifier provides me with what I need. That is: clean power (less than 0.2% up to clipping), good frequency response, and 5 or so watts to drive the speakers. The sub woofer output will not be used.

Recently I have purchased a total of four of the amplifiers. I put the them all on the bench and ran power and distortion tests before use. I found that performance for all four to be almost identical and a long way from the specs.

STEREO AMPLIFIER PERFORMANCE:
Power Output – I measured single channel power output at 1KHz just below clipping and found that power output was 5.1 watts at 8 ohms, 7 watts at 4 ohms, and 5.2watts at 2 ohms. Power stayed within a few percent over the range of 20Hz to 20KHz.

Distortion – I checked distortion at just below clipping at 8 ohms. Distortion was 0.12% at 1KHz, 0.095% at 100Hz, and 0.25% at 20Hz. I did not check higher frequency distortion. Output power and distortion did not change significantly when both channels were driven.

Frequency Response and Sensitivity – With the tone controls adjusted for maximum flatness the outputs were 3dB down at 20Hz and 55KHz. With the volume control set to max (CW), 226mV was required at 1KHz to produce levels just below clipping.

SUBWOOFER AMPLIFIER PERFORMANCE:
Power Output – I measured the subwoofer power output at just below clipping at 20Hz, 50Hz and 200Hz. I measured 5.12 watts at 8 ohms, 6.76 watts at 4 ohms. At 2 ohms I measured 8.82 watts at 50 and 200Hz and 5.6 watts at 20Hz.

Distortion – I measured distortion at just below clipping from 20Hz to 200Hz. At 8 ohms, distortion was between 5.2% and 5.8%. At 4 ohms, distortion was between 10% and 11% over that frequency range. At 2 ohms, distortion was 21% at 50 and 200Hz and at 20Hz, output level was lower and distortion was 17%. I reduced the level to 1 watt into 8 ohms at 50Hz and still measured 5% distortion.

Input Sensitivity – With the SUB VOLUME set to max (CW), 15.6mV is required to produce levels just below clipping. This means that the subwoofer channel has 14.5X (23dB) more gain than the stereo channels. Sub-volume is not adjusted by the main volume control. Matching the two levels requires that the sub volume need only be turned a few degrees clockwise.

Frequency response – Maximum output was at 24Hz and relative to this frequency was 3dB down at 9Hz and 61Hz and down 17dB at 200Hz. Independent of the X-OVER control’s setting, the relative frequency response of the subwoofer channel did not change. Changing the X-OVER control from 40Hz to 200Hz instead resulted in an overall subwoofer output drop of 3dB.

Other – The subwoofer output is almost 180° out of phase with the stereo outputs. This is easily fixed by reversing the subwoofer leads.

OTHER ISSUES:
The LEDS are too bright.
The speaker connectors are poor. One broke and others are about to.
The Audio Input RCA jacks and AUX mini jack are directly paralleled.

CONCLUSIONS:
The power output specs for this amplifier are misleading. A total of 148 watts output are specified (40+40+68) while the power supply is rated at 12 volts at 3amps (36 watts).

HOW TO VOID THE WARRANTY – I searched for a schematic for this device and could not find one. I therefore captured it manually. The schematic allowed me to come up with mods to the circuitry to make it perform to spec.

1. Subwoofer distortion was mainly caused by inadequate power ground to the subwoofer output IC. After beefing this up, distortion is below 0.1% in the subwoofer channel.

2. Correcting the subwoofer frequency response required removing some capacitors and changing the values of others.

3. Tying the subwoofer level to the main volume level required changing resistor values and connection points at the volume control. This also made the subwoofer level control more friendly with levels matched at about mid-range.

4. I changed the series resistor for the blue LED to From 220 ohm to 10K.

5. I changed the series resistor for the red LED from 2.2K to 47K.

6. On one amplifier, I replaced the speaker connectors with 5-way binding posts.

FINALLY:
I hope others find this informative. Ignore the manufacturer’s specifications. If you need a low power, low distortion stereo amplifier, this is a reasonable choice. It has a nice look to it, but forget about the subwoofer output. Unless you have the knowledge to overhaul it, the subwoofer is useless. Also be aware that the speaker connectors are somewhat fragile.

That's interesting how you're using a 4 channel amp in 2 channel mode, correct? Does that put the subwoofer on only 1 channel or does it mix L+R?

Did the LP-168HA ground mod... sub amp is a TDA7297. Didn't do an A/B test but it seems better?

"Upgraded" a System 11 game with speakers I had on hand.
Backbox: 2 x 6.5" full range speakers, 4 ohm. Wired in series. Didn't enlarge the tweeter speaker hole, just centered the new speaker over it.
Cabinet: 6.5" midbass woofer, 4ohm. Added a speaker crossover, as System 11 sends full range audio to the cabinet.

Yes.

Replaced the Lepai LP-168HA amps I've been running in my homebrew cabs with ZK-TB21 amps. Based on TPA3116D2 chips, sold under a few brands such as Fosi and Wuzhi. The difference is night and day, it's able to actually drive the subwoofer at a decent volume without clipping. Did not upgrade the power supply. Only complaint is no way to disable the bluetooth. There are other amps based on this chip but I couldn't find one with tone controls that did not have BT.

Found a WillisonAudioLabs video where the amp dyno'd at 7 watts on the sub channel before clipping.

These things have been around for years and the design flaws were never corrected. I don't know why Parts Express sells this garbage. I don't know why Spooky uses these amps in their games, especially TNA where the soundtrack got a lot of attention. They could do so much better with any of the pcb-only options.

If you are building a homebrew pinball game do not use a Lepai LP-168HA, you are wasting your time.

Hopefully that's enough keywords to show up in google search results, lol.

I tried one of the non-bluetooth TPA3116D2 amps, but it did not meet my needs. This one only has a treble adjustment for the L/R channels. The amp is driving a pair of Sony SSCS5 bookshelf speakers and they need some bass boost to sound good. If the audio has an EQ upstream it might be OK but I did not try to find the EQ in Windows.

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Off the volume control.

You are correct it's a variable resistor. It takes the output of the sound generation section and attenuates it before feeding the power amplifier section, which is fixed gain.

The signal there is a little hot but it's still around 1V pk-pk. You could hook up a 2nd volume control in parallel and use that to feed your amplifier.