2716 or 28c16. May need to adjust the jumpers too

The sound boards can be configured to use two different rom types, the 2716/2816 or the 9316. Both fit the same socket but have different pinouts. Games could have come with either type, but 9316s aren't reprogrammable so you need to use 2716s. If yours is jumpered for 9316s then it needs to be changed

The rectangular shaped sound board has jumpers for 2716 but a 2732 can also be used if you double up the image file.

The square shaped sound board that can have speech uses a 2716 sound rom for most game, again a doubled up 2732 can be used to replace the 2716. A few games require a 2532 ROM. I am not sure if factory jumpers exists to use a 2732 sound rom instead of 2532.

The speech ROMs are 2532. Once system 9 rolled around they added 2732 jumpers to the same compatible speech card, but that isnt normally found in a system 6/7 game. You can reverse engineer the system 9 schematic and apply it to the system 6/7 speech card. Pinwiki has info about this.

NMC27C32, M2732A.... etc are examples are 2732 eprom part numbers.

Here is a tip for ROM burning. Most the EPROMs follow a pin out standard. There are some oddballs like 2532 and 27C301 but forget those for the example... Since the pinout is standard you can generally sub larger EPROMs for smaller ones. Knowing that you can stock the largest size eprom in the pin count package... For example 2764, 27128, 27256, and 27512 are all 28pin EPROMs. A 27512 can be used to replace (95% of the time) all the way back to 2764 assuming you fill the ROM up with repeated copies of the binary file. Same goes for 24 and 32pin eproms.

Is there any way to clean up or clear up the speech in a Williams System 6 game? I have a Blackout and the early speech is hard to understand. Is there a way to reprogram a speech chip to sound better phonetically? Can a new speech ROM be modified somehow to improve speech? Thanks!

Try replacing the IC3 opamp (and maybe IC2 too) on speech board. They sometimes cause bad distortion in speech.

There is no verification of the speech ROMs so if they go corrupt some of the words get garbled. You may want to compare to a youtube video or something to see if what you hear is normal

Sure, Blackout is not the most clearly speaking System 6 game. I remember while working for an operator when Blackout was released, he was very amazed how its speech sounded so bad compared to previous Gorgar. But I still remember hearing "Launch Mission", "Condition Red/Green/Yellow", "Orbit Completed", "Blackout" and whatever random phrase at game over, and even though my English is not very good, I definitely could understand those. So I still recommend replacing the opamp and/or capacitors on speech board.

Bad speech ROM's very likely result in completely random noise instead of speech.