Originally Posted by subbuilds
I could add up to 6 UM-18's but am not sure if there is enough available power to drive them.
This project is a bit of a one-off... what works best for a HT and what works best for this project are two entirely different things.
Normally I would recommend a single 24 and a SpeakerPower amp for HT, or a nu1kdsp and PA-460 for chest-kick.
But even that won't be near-enough
for this project...
Haven't box-modeled it BUT if you can afford 6 UM-18's, then you MIGHT actually be better off with 18 of these 18's instead
(with bulk discount and sales codes): https://www.parts-express.com/dayton...4-ohm--295-475
They are 96db/w/m and have more excursion than PA-460's have, for not much more money.
The UM is only 88db/w/m and 3x the price, it does have more excursion and power handling though.
Trust the box modeling software, they usually aren't far off. Whatever it says is best, buy that...
Cone area vs excursion ratio is very important for ULF on the cheap. Likely more FAR important than available-watts or power-handling in this case... as I mentioned earlier.
You may actually want to rent
a few Powersoft K20's for a day, those have PFC which is super important when limited by the breaker. PFC makes the amplifier draw a smooth waveform rather than drawing spikes of amperes when the 120V drops to 0V 120 times a second, and by renting you aren't committing to it for later personal ownership. You can usually rent pro amps at your local pro-sound shops (if you have any good shops that have the good amplifiers. i.e. Powersoft).
Otherwise just get the SpeakerPower amps, those are known-good for single digit Hz into 1-ohm loads. Especially their rack mountable amps.
What works well for this project vs personal ownership in HT is two entirely different things...
This is one of the freak cases
where 18 of the Dayton Classic 18's might just outperform both the UM and PA Dayton's for the same $.
Make the box as big as you can lift or transport, and as many of those big boxes as you can afford to transport, and put as many 18's as will fit in a 14hz tuning in each one.
Rent the largest
moving truck for a day and a pallet jack (or fork lift if available).
Bigger boxes are more efficient vs smaller boxes,
but really it is ALSO the ratio of cones per cuft... and your ability to lift/transport/place the things.
You don't want the port velocity to be too high or you will get nothing but port chuffing. That is the one downside of ported boxes vs sealed.
Ported is the goldilocks zone of box types, more efficient than sealed nearing the tuning frequency, and easier to make than horned...
Ported is about 8-12db louder than sealed, near say 14hz...
Horned is about 6db louder than ported. Which WOULD come in handy in this case.
Horned boxes tend to be about 25-50% bigger than ported boxes.
No free lunch.
No matter how many cones you end up buying or which ones, I'd still have computer fans blowing directly on the coils to cool them in this project. They are cheap and they work.
Sinewaves put a LOT of stress on both the coils and the amplifier.
Maximum stress, in fact...
The only thing worse is clipped-sinewaves or squarewaves