You probably dont want to hear this...but the tool I use is my ears. Most of the time in my experiences, there is no difference. Acoustically speaking. Technically, there are measured differences in reinforment of lower response vs cancellation. Ears...you dont need anything else for this exersize. |
Start with a test tone that is below your crossover point of your mains. Set the volume to a comfortable level. Using a SPL meter at the seating position, adjust the phase of your sub that produces the highest output...you're done. Now comes the fun part of sub positioning, crossover points and volume. Good luck, and have some fun. |
BRF's approach is a good one. Sometimes, though, it is easier to do that but find the setting that produces the lowest output as the null can be sharper/more defined than the peak. Then, subtract/add 180deg to that.
You might try both.
Kal
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A product that I use and frequently recommend is the Velodyne SMS-1 sub controller. Attach a monitor and you will see the effect of any change to any parameter (including phase) on the frequency response at your listening position. I find it tremendously helpful in setting up/integrating subs. It also allows PEq to smooth the subs response - which may well provide dramatic improvement in your system's bottom end. That has been my experience, anyway.
Cost is $450 from Audioadvisor.com.
Good Luck
Marty |
If you are interested in the Velodyne SMS-1, you might want to take a look at this link.
http://www.hometheatershack.com/forums/bfd-electronic-equalization-devices/6346-behringer-fbq2496-velodyne-sms-1-distortion.html
It is a couple of years old and maybe that problem has been fixed in the recent versions; but if you are looking to buy used, you might want to double check. |
Thank you BRF and Kal, your answers make sense to me. And best of all I won't need to buy any additional testing equipment :) |
Sidssp,
Am I reading these right?
The SMS-1 input can be overloaded into distortion. To prevent this, adjust the output level of the source appropriately. Done. No issue (at the preferred -6db input level, distortion for both the Behringer and the SMS is inaudibly low - per those graphs). Granted, the Behringer measures a bit better, but - given these very low THD levels at these very low frequencies - I really believe that you're looking at hairs on the arms of the angels on the head of the pin.
The LF roll off shown for the SMS-1 is down app 2db @20hz. I filter at 25hz anyway for my music only system. This might be an issue for HT use, but not IMO for music.
Unless those results are viewed in light of HT use, they will be awfully misleading. Unless I'm missing something -and it wouldn't be the first time for that!
Marty |
A bit off-topic and this may not contribute to the thread.
I find that most musical material differ in bass frequency output. Some albums will have more bass and sound boomy even without the subwoofer integrated into the system(room acoustics affect this to a certain extent) while some albums will need the volume/crossover on the sub to be turned up considerably high above the half-way point on the volume knob of the sub in order to feel the bass. As such, I am unsure whether setting-up the sub accurately using test tones as suggested by most folks(which is supposed to be the correct method anyway) will apply to all conditions and all albums, both CD and LP format.
I don't know about others but the settings on my subwoofer are always changed periodically dictated by the particular CD or record that is played. Any insight on the proper method to professionally set up the subwoofer would be appreciated. For those who have professionally set up the sub using test tones, do the settings stay put for all listening material?
p/s: I have a Radio Shack meter and test tone CD. |
Ryder, using a standardized sub set up, you are attempting to equalize the output amongst the various frequencies, thus attempting to eliminate any frequency nulls and peaks. With a neutral setting i.e. flat response, you now can hear what the recording engineer wanted you to hear.
Adjusting the sub by ear and further adjusting the output based on specific CDs is basically over riding the recording engineers efforts and tailoring the sound to your particular taste. Nothing wrong with this approach, but it is a colored approach. Even at fine restaurants I sometimes find the need for more salt. |
I have used a little different method than described above to adjust subwoofer phase. If you have a sub where the phase is adjustable by remote you can do it with one person, if not you will need a friend to help. First place the sub in the best position possible given room arrangement and spousal compatability. There are other threads that give good advice on how to find this location. Second, run the speakers full range and adjust the subwoofer crossover above the cutoff of your mains. Subwoofer volume should be set fairly low for this. Play music that you are familiar with while listening from the main listening position. Have the friend or use the remote to adjust the subwoofer phase thru its range while listening. When you get the mains and sub in phase with each other, the leading edge to the bass notes will be heard at the same time. When they are not, it will sound like 2 separate bass notes at slightly different times. It is very similar to wiring a mid range or tweeter out of phase. It will be obvious to your ears when you get it right. Now, adjust the crossover to the setting that you want and finally adjust level.
I don't know if this method is what would normally be done, but it worked for me. I have a Velodyne DD-12 which has the SMS-1 mentioned above integral to the sub. I tried going thru the set up that the manual described, which is similar to what others have suggested above, and just couldn't get it to sound right. It now blends beautifully with my mains. The fact that it also has a digital parametric eq to help smooth out the bass due to less than optimal positioning is icing on the cake. |
