Any proven UM8 builds (Ultimax 8")?

[lamski]

Are there any good proven UM8 builds for home theater (movie) use? Trying to get the strongest bass (impact/output) from a thin cabinet due to space constraints. I will plan to build 2 of them to run as stereo subs in the front of the room. If an 8" just won't cut it, are there any other options like maybe a larger driver mounted on the side while keeping the cabinet thin? I'd like to try and keep the cabinet to 10" wide or less if possible.

[Chris Roemer]

You can get into the lower half of the 20s in about 1.7cf (net) w/a 3" Precision Port that's anywhere from 12" to 18" long.
A 200 or 250w amp should be good.

[lamski]

After some additional research it looks like the 10" UM would be a considerable upgrade without a huge step up in size.

Now to decide if I should go with a slot port like in your tower stand version or a Passive Radiator. Any PR designs with the UM10 out there?

[billfitzmaurice]

I will plan to build 2 of them to run as stereo subs in the front of the room.

That's a very popular placement, but far more often than not it's poor placement. There's no such thing as stereo below 80Hz, as recordings have been summed to mono in the lows since the late 1970s. Where room response is concerned the best placement for subs and for mains is almost never within the same footprint, nor the same distance from the wall, nor even necessarily on the same end of the room. My mains are 14 feet in front of me, my sub is 1 foot behind me, integration is perfect. Before deciding on placement, and in so doing restricting the sub options, research speaker placement.

[jim85iroc]

how do you prevent localization in cases where the sub isn't up front? I briefly had my sub in the corner behind me in one of my listening rooms, and it was awful. Even with the low pass set somewhere around 50hz, I always heard the bass behind me instead of up front. In car audio situations this was typically an issue because of resonances coming from other panels, so sound deadening and other mitigations to prevent resonances would help bring the bass sound up front, but in my room, I don't have items there that could be resonating except for the structure itself, yet the localization was extremely audible and very distracting.

[wogg]

I you were able to localize your sub, you were probably doing so based on harmonics, vibrations, or other distortions and not the low frequencies themselves. The wavelength involved is just too long for your brain to be able to localize, starting around 200Hz but definitely below 100Hz. As long as the crossover and time alignment are good and you eliminate as much distortion (from driver and rattling bits elsewhere) you will not be able to tell where that woofer is at all.

[Wolf]

UM10 with RSS315PR, called Overdrive10:

http://techtalk.parts-express.com/fo...d-overdrive-10

Wolf

[billfitzmaurice]

If you can localize a sub that's crossed over at 80Hz it's because it has high THD and you're localizing harmonics.

[jim85iroc]

perhaps that's the case. The sub is an older Dayton SD-215 DVC sub. I always thought those were pretty decent subs, and aside from the localization issue, I have no complaints with it. I moved it to the front of the room and have continued to be as happy as a clam with it.