Impulse response

[aqman]

There is an interesting article here:

http://www.soundoctor.com/whitepapers/subs.htm

by Soundoctor that states that modern sealed and active subs like the JL audio subs, have about a 10 ms group delay. That means to get the impulse response of the mains and sub to match, you need to move the sub about 9 feet closer the listening position than the mains. For many of us, that would literally mean sitting on the sub.

The alternative is to delay the mains somehow. Most HT receivers/processors have the ability to do this, but I'm not aware of any "audiophile" preamps with this ability. I owned the Classe CP-800 and I know that although it had some bass management and room correction features, it could not delay mains wrt sub.

Active crossovers like the Bryston and JL's own CR-1 also don't have this capability. Are all audiophiles with subs doing it wrong- or at least sub-optimally?

I found that it can be done in JRiver as described by benchmark:
http://benchmarkmedia.com/blogs/news...1-music-server

but additional dacs and sound cards and using JRiver for volume is clunky to say the least.

This made me seriously reconsider trying to integrate a sub.

Thoughts?

[chessman]

My subs seem integrated (both in front, one each next to each main). I cannot move the mains back or the subs forward. I assume the subs are one full cycle behind, i.e. in phase but with the front of the impulse wave of the subs lagging the mains. I have them crossed at 50 H, the lowest the Bryston 10B-SUB would go, to minimize the effect of the lag. For me, gaining 1.5 octaves, widening the sound stage, and sweetening the mid-range by lightening the load on the amp were benefits that out-weighed the burden of poor bass timbre or other bass smearing. HOWEVER, I did not feel that way until I got the Bryston dialed in. Until then, the subs always sounded somehow "wrong."

[djwhog]

I recall several of Ivan's rooms the mains were in front and the subs were closer to the listener and behind you.

I have both my subs about 10' closer to me and they seem to be very seamless, I would note I think it is easy to add to much bass. My concern is to make sure that the crossovers are low enough as to still blend with the mains and leave no gaps in lower crossover points.

I guess I can see this would be a bigger issue with mains that have a hard time getting down to save at least 60hz, that said I cross over one sub at 40hz and the other at 35hz to compensate for the room placement etc.

When you can crossover lover and with a steeper slope the bass is not very directional and that to seems to dismiss delays blending issues etc.

Good points, nice article and post... Thanks

Sent from my iPad using A.Aficionado

[chessman]

UPDATE:

Upon rereading the article mentioned by the OP, I realized that while my two channel sub integration was set in stone, I did have the option to use Barry Ober's tip for the third sub that I use for redirected bass/LFE in the home theater application. Since the mains are 9 feet away from the listening position, I simply set that sub for 21 feet. Presto! The impulse waves match and now movies, television and video games are breathtaking.

[jdandy]

aqman.......The JL Audio Fathom and Gotham subwoofers have a phase control that allows the user to adjust timing of the subwoofer output relative to the mains speakers. The phase angle is adjustable from 0° to 280°. This allows a user to synchronize the subwoofer cone's launch time with the mains speakers.

One of the easiest ways I have found to make this adjustment relatively accurate is to reverse the polarity of the main speakers, usually by swapping the positive and negative speaker wires at the back of the speakers. Set the subwoofer crossover to 80Hz for testing purposes and adjust the subwoofer output to equal the main speakers as close as possible. Using music with solid low and mid-bass content or as an alternative use low frequency bass test tones while making minor adjustment to the Fathom's phase control. When you reach the point where the least low frequencies are audible you will have the woofers in the mains speakers and the subwoofer launching at the same time. In other words, with the mains out of phase with the subwoofer both speakers will cancel the low frequency outputs when the phase control reaches the right spot. This may take some time to dial in accurately. It is advisable to have someone help you to make the adjustment on the phase control while you sit in the sweet spot listening. Once the bass output is the least it can be stop there, then reverse your mains speaker's polarity back to the proper positive and negative connections from the amplifier and you are done. After that it is a matter of selecting the specific crossover point you want to use and adjusting the output level to your satisfaction.

[nicoff]

Originally Posted by jdandy

aqman.......The JL Audio Fathom and Gotham subwoofers have a phase control that allows the user to adjust timing of the subwoofer output relative to the mains speakers. The phase angle is adjustable from 0° to 280°. This allows a user to synchronize the subwoofer cone's launch time with the mains speakers. One of the easiest ways I have found to make this adjustment relatively accurate is to reverse the polarity of the main speakers, usually by swapping the positive and negative speaker wires at the back of the speakers. Set the subwoofer crossover to 80Hz for testing purposes and adjust the subwoofer output to equal the main speakers as close as possible. Using music with solid low and mid-bass content or as an alternative use low frequency bass test tones while making minor adjustment to the Fathom's phase control. When you reach the point where the least low frequencies are audible you will have the woofers in the mains speakers and the subwoofer launching at the same time. In other words, with the mains out of phase with the subwoofer both speakers will cancel the low frequency outputs when the phase control reaches the right spot. This may take some time to dial in accurately. It is advisable to have someone help you to make the adjustment on the phase control while you sit in the sweet spot listening. Once the bass output is the least it can be stop there, then reverse your mains speaker's polarity back to the proper positive and negative connections from the amplifier and you are done. After that it is a matter of selecting the specific crossover point you want to use and adjusting the output level to your satisfaction.

That procedure that you listed is similar to the one described by Barry Ober in the white paper that the OP linked to/referenced above. I just went through this procedure with my system. It works very well.

[jdandy]

Originally Posted by nicoff

That procedure that you listed is similar to the one described by Barry Ober in the white paper that the OP linked to/referenced above. I just went through this procedure with my system. It works very well.

nicoff.......I am glad to hear you were successful with this subwoofer setup procedure. It has worked for me for years to set up several subwoofers. I hope others will take the time to try this routine. It produces good results.

[crwilli]

Originally Posted by jdandy

aqman.......The JL Audio Fathom and Gotham subwoofers have a phase control that allows the user to adjust timing of the subwoofer output relative to the mains speakers. The phase angle is adjustable from 0° to 280°. This allows a user to synchronize the subwoofer cone's launch time with the mains speakers. One of the easiest ways I have found to make this adjustment relatively accurate is to reverse the polarity of the main speakers, usually by swapping the positive and negative speaker wires at the back of the speakers. Set the subwoofer crossover to 80Hz for testing purposes and adjust the subwoofer output to equal the main speakers as close as possible. Using music with solid low and mid-bass content or as an alternative use low frequency bass test tones while making minor adjustment to the Fathom's phase control. When you reach the point where the least low frequencies are audible you will have the woofers in the mains speakers and the subwoofer launching at the same time. In other words, with the mains out of phase with the subwoofer both speakers will cancel the low frequency outputs when the phase control reaches the right spot. This may take some time to dial in accurately. It is advisable to have someone help you to make the adjustment on the phase control while you sit in the sweet spot listening. Once the bass output is the least it can be stop there, then reverse your mains speaker's polarity back to the proper positive and negative connections from the amplifier and you are done. After that it is a matter of selecting the specific crossover point you want to use and adjusting the output level to your satisfaction.

Going to try this tomorrow.

[chessman]

Originally Posted by jdandy

aqman.......The JL Audio Fathom and Gotham subwoofers have a phase control that allows the user to adjust timing of the subwoofer output relative to the mains speakers. The phase angle is adjustable from 0° to 280°. This allows a user to synchronize the subwoofer cone's launch time with the mains speakers. One of the easiest ways I have found to make this adjustment relatively accurate is to reverse the polarity of the main speakers, usually by swapping the positive and negative speaker wires at the back of the speakers. Set the subwoofer crossover to 80Hz for testing purposes and adjust the subwoofer output to equal the main speakers as close as possible. Using music with solid low and mid-bass content or as an alternative use low frequency bass test tones while making minor adjustment to the Fathom's phase control. When you reach the point where the least low frequencies are audible you will have the woofers in the mains speakers and the subwoofer launching at the same time. In other words, with the mains out of phase with the subwoofer both speakers will cancel the low frequency outputs when the phase control reaches the right spot. This may take some time to dial in accurately. It is advisable to have someone help you to make the adjustment on the phase control while you sit in the sweet spot listening. Once the bass output is the least it can be stop there, then reverse your mains speaker's polarity back to the proper positive and negative connections from the amplifier and you are done. After that it is a matter of selecting the specific crossover point you want to use and adjusting the output level to your satisfaction.

This method will align the phase angle, but it cannot prevent the front of the impulse wave from lagging can it? In other words the wave pattern matches, but is a cycle behind in time?