small subwoofers

[dodgerblue]

Hi Eddie: I also have a vaulted ceiling in my listening room and it is open-ended, so it connects to the den and eventually into the kitchen. The listening space (LR) is 15' x 15' and the walls are probably 8', then the vaulted ceiling; I wouldn't know how to calculate cubic feet with this configuration. As far as having adequate power, for my room with a 9:00 dial setting, I'm satisfied. If I try to crank it up to reference level (which is probably front fow center), I'll be having my neighbors on me, since I live in a townhome complex. I wish I could give you some advice on room size and sub selection. The UFW-10, which you refer to, has a ~500 watt (?) amp. The ULF-10 that I have has a 375 watt amp. I read somewhere that it is only a 2-3 db increase in SPL. I don't know what that means since I don't use a SPL meter. All my calibrations are done by ear. Good luck with your search. AV123 has a 30-day trial period and their customer service is A1 like Ascend.

[Mag_Neato]

I recently added a UFW-10 to go with my 170's. My room is 13'x 18' with 8' ceiling with two non-closable doorways. I put the sub in the system without any calibration, meaning I set the gain to 12 o'clock, phase knob at "0", and the PEQ zeroed out(no EQ). It sounds very good just like it is, even a step better than the BFD'd PSB 12" ported sub it replaced! There may be some low end rumble missing, but I can't tell for sure.

For 6000 cubic feet, I'd go with either dual UFW's or a big Hsu or SVS.

[dodgerblue]

Fellow audio purists: I have another elementary question. What is Phase and how does changing the value from 0 - 180 change the sound. It seems like it has something to do with angles and making the sub and speakers a cohesive unit. But I've never received a layman's definition of what is actually going on. Is the difference something that can be detected by ear or do you need a SPL meter to smooth things out. Thanks.

Oh, Eddie. What knid of speakers are you using. Seems like if you have Ascend 170s and are satisfied in that large room, my logic says that the UFW-10 may also satisfy your needs. This is merely based on the fact that the the sub and 170s are designed for small-medium sized rooms.

[BradJudy]

Fellow audio purists: I have another elementary question. What is Phase and how does changing the value from 0 - 180 change the sound. It seems like it has something to do with angles and making the sub and speakers a cohesive unit. But I've never received a layman's definition of what is actually going on. Is the difference something that can be detected by ear or do you need a SPL meter to smooth things out. Thanks.

Phase adjustment on a subwoofer is used to make sure the sub and speakers are 'in sync' with each other and not fighting each other. On a more mathematical level, it has to do with the superposition of the sound waves and whether this creates constructive or destructive interference. You want the sub and speakers to be working together (constructive interference) to create an even frequency response (difference frequencies are the same loudness). If they are not working together, there will be a big dip in the loudness at the frequencies they overlap. It is possible to make this adjustment by ear (listen to test tone in the crossover/overlap range while someone else adjusts the phase until it sounds loudest). It also is very clear in measurements when the phase is wrong.

Here's a measurement with the phase set wrong - http://www.bradjudy.com/AV123/sub_an...oom_0phase.JPG

Here's one with the phase set correctly -
http://www.bradjudy.com/AV123/sub_and_mains_inroom.JPG

[dodgerblue]

Thanks BradJudy for trying to explain the technical to someone who is not technical. I'm guessing now, so, if a sub and speakers are in sync, does that mean that the sound waves are reaching the listeners ears at the same time? If so, is there a delay working here? Excuse me, if I sound lame. I'm still unclear about the mechanics of what is actually happening when the sound waves are in-/out of sync. But I will try the test you suggest, when I get a CD of bass test tones. Thanks.

[BradJudy]

Yes, the phase adjustment can also be thought of as a delay adjustment to get the sound waves reaching the listener at the same time. This is why a 'distance' setting for a subwoofer in your receiver can also be used to adjust phase - it is also a delay adjustment.

[Eddie]

dodgerblue,

actually I have 340s across the front, and am very happy with them given my room's size. Just hate my crappy JBL e150 sub, though its positioning (in center of room with only about 2 feet of a wall anchoring behind it, and no other placement is possible at this time for WAF reasons so don't even ask).

I'm interested in the UFW/ULW subs because I keep hearing that sealed subs are better for music, but I want to make sure that such a small sub won't get swallowed up by all that space.

[dodgerblue]

BradJudy: Ah ha! Now it makes sense. Thanks for hanging in there. Also, thanks for the initial suggestion of the ULW-10.

Eddie: I understand your concern and hope you find the right match. If you're not concerned about size perhaps the HSU and SVS makes may meet your needs. If you haven't already, the Goodsound review of the UFW-10 does make a comparison with the HSU. Good luck!

[dodgerblue]

Epilogue. It's been a couple of months now since I received my Rocket ULW-10. And I discovered something significant that may affect other owners of two-channel receivers connecting to subs with only a single low level line input. My advice: don't connect a y-adapter cable at the L/R outputs on the receiver, as recommended in the owner's manual, but just use a single subwoofer cable and attach it either to the L or R channel then to the sub input. I'm embarassed to admit this, but I didn't initially hear the degradation in the sound associated with using the Y-adapter. By using the Y-adapter at my pre-outs on the receiver, the soundstage depth and width and the imaging was compromised. I discovered this by accident while listening to a CD with recordings designed to test your system. On tracks that were supposed to play music from only the L or R channels, both channels were active! And on a track that was supposed to simulate instruments moving L to R and back again, there was no movement detected! Then I tried to use my balance controls and found out that they were not working properly, that is, even by turing the the balance knob to either extreme, sound was coming from both channels! So, I experimented with the cables to see what was up and was able to correct the audio by using only the single subwoofer cable and eliminating the y-adapter. I called NAD and asked about this, and the technician told me that I was correct in connecting the sub the way that I did. He indicated that some subs with summed LFE inputs are not truly summed and this affects the amplifier and in some cases could cause permanent damage. I also read a thread on Audioholics about using or not using y-adapters which confirmed what my ears were hearing. I thought my system sounded more complete with the sub, but now, I'm even more pleased because the change was obvious. I thought I'd just throw this out there for owners of a two-channel receiver that are thnking about adding a sub. FYI my int amp is a NAD 370. Maybe with other two-channel systems, this may not be a problem.

[bikeman]

Have you posted this over at the AV123 Forum?

David