[Schwingding]

I have seen it mentioned that subs co-located or put right on top of each other do not suffer phasing issues between each other.


Is this correct? If so, what is the effective distance before this benefit is no longer applicable?


BTW, dual SVS PB 12 + /2s


Thanks.

 

[Richard Mayer]

It depends of the crossover frequency used. With 80 Hz they should be closer than ~2 meters or 7 feet.

 

[Ed Mullen]

Recent experimentation has convinced me to place duals even closer......I've seen some cancellation (in certain applications) occuring at 1/2 wavelength separation distances that cleared up as the subs were moved closer.


I'm currently most comfortable getting within a 1/4 wavelength at the selected XO frequency (about 3-4 feet with an 80 Hz XO). As usual, YMMV and experiment to see what works best in your room - these guidelines are not absolutes and good results can still be had in many applications with the subs placed farther apart than 1/4 wavelength.

 

[Darin]

I can't say how accurate this is, but I've read that you'll get co-located benefits as long as the drivers are within 1/4 wavelength. Between 1/4 to 1/2 wavelenth is iffy, and above 1/2 wavelength they definitely behave as two separate sources. That being said, just because your subs are greater than that, doesn't mean you can't realize any benefit from them. You won't get the extra gain from the added driver area at the higher frequencies (only the extra gain from the extra displacement), and you will run the risk of some cancellation at some frequencies at some listening points, but you GAIN the possibility of filling some nulls. So, within 1/4 wavelength, they act as one sub, no cancellations, and you should get 6db gain. Greater than 1/2 wavelength, they act as two subs, so you should get 3db gain, but possibly[/b] smoother response in more listening positions in the room (though experimentation may be needed to find the right two spots to make this happen). Between 1/4 and 1/2 wavelength... maybe something in between.

 

[HT Nut]

SD,


My LF subs are almost 14 feet apart, front and back of room. lovely wifes ears are about 5 feet from front sub, my ears are about 3 feet from rear sub.


But then I cross over to higher frequency subs at 40 hz to avoid doppler distortions from the long excursions. so I am at longer wavelengths.


Hence my five subs.

 

[Schwingding]

Thanks for the great responses everyone. I had been running my XO at 60Hz until recently when I moved it to 80 becuse I had an almost 15db spike in the 60Hz region of my frequency response curve and the only way I could tame it (tried everything!) was to move the XO to 80Hz. It worked well, in fact.


I will move the subs within a couple of feet and experiment. Hard to believe it can be even better! Ron S. suggested to me in an email a while back that I put one on top of the other. I'll give that a go as well. (with some help as literally, each one of these weighs more than me)

 

[Denon2807]



Quote:
Originally Posted by Schwingding /forum/post/0


I will move the subs within a couple of feet and experiment. Hard to believe it can be even better! Ron S. suggested to me in an email a while back that I put one on top of the other. I'll give that a go as well. (with some help as literally, each one of these weighs more than me)

You must be a short and skinny man at less than 140 pounds.

I'm going to have my own challanges with phasing and whatnot as I'm in a similar position as you. I've got one SVS PB12-Plus/2, with the second one arriving today, and they will be about 12 feet from each other with the second one being just 3 to 4 feet from the listening position and the first one being about 14 feet from the listening position. To make the challenge even more difficult I've got a HSU MBM-12 that I'm placing directly (as in touching against) behind the main seating position (couch).


I'm looking to bring in a pro, perferably from these boards so if any of you guys know anyone in the central Florida area who is good with configuring multiple subs, please let me know.

 

[Schwingding]



Quote:
Originally Posted by Denon2807 /forum/post/0


You must be a short and skinny man at less than 140 pounds.

I'm going to have my own challanges with phasing and whatnot as I'm in a similar position as you. I've got one SVS PB12-Plus/2, with the second one arriving today, and they will be about 12 feet from each other with the second one being just 3 to 4 feet from the listening position and the first one being about 14 feet from the listening position. To make the challenge even more difficult I've got a HSU MBM-12 that I'm placing directly (as in touching against) behind the main seating position (couch)..

5'5", ironman triathlete - I'd better be skinny!


Your setup is almost identical to mine, even position wise, with the exception of the HSU. I'll keep you posted on my experiments over the weekend.

 

[JimP]

Just to open this up to more thinking.


I was playing around with the distance setting for my sub and other front speakers while observing their behavior on the on screen display of the SMS-1. What I find is that two listening positions 5 feet apart will have different signal combining/smearing(difference in phasing). You calibrate the distance setting for your speakers for one spot and everwhere else it'll be different. (JimP slaps head and says out loud "of course it is, stupid") As much effort we go through to get things just perfect, at some point you realize that there is no way its going to be that perfect.

 

[Denon2807]



Quote:
Originally Posted by Schwingding /forum/post/0


5'5", ironman triathlete - I'd better be skinny!


Your setup is almost identical to mine, even position wise, with the exception of the HSU. I'll keep you posted on my experiments over the weekend.

Thanks, Schwingding! I'm looking forward to your results.


IRONMAN triathalete, huh? Were you here in Clearwater for last years' World Championship --- a couple months ago I believe it was? I was pretty shocked the event was taking place in the small town that I live which is Clearwater. It was pretty neat to see the event going on, and wow, all those Clearwater Police stationed at every corner. Because the police had every U-turn median spot blocked I had to drive for 4 miles in order to turn around. It was frustrating but I understood since it was only one day. If I recall I think they said they had over 2,000 Clearwater Police out there that day. That's like half the city!

Haha.

 

[Schwingding]

I was not a Clearwater - that race was not an ironman distance race, by the way, but a big show, nonetheless. They had a lot of trouble with the bike course which led to a lot of illegal drafting - too many people on a course that didn't allow them to spread out, cyclists aren't allowed within 3 lengths of each other in triathlon unless passing.

 

[HT Nut]

"As much effort we go through to get things just perfect, at some point you realize that there is no way its going to be that perfect."


The new home theater seating will have a vice to keep your ears aligned just so with the speakers to prevent any phase shifting.


This thread was about subs which some seem to have set to reproduce two octaves of sound. There is no way on this earth that you will negate all the nulls and peaks in a room of any reasonable proportions. The higher the frequency the less room there is to move yor head.


A good buddy of mine used Altec Lansing Voice of the Theaters like earphones. Each speaker set up so the horns were about a foot from his ears. That was even more volume than I care to use for rock music. And he was driving them with 200 wpc MacIntosh amps.


Yeah Yeah I am old. But I am not yet too dumb. I get a real belly laugh sometimes when people get all serious about vibrating diaphragms.


I think the biggest hoot ever was during the transition to digital music when the analogophiles were convinced that digitally recorded and manipulated music when transferred to vinyl would damage the bearings in your tonearm.


And that Schwingding is a mighty small man. Take that any way you like.

 

[Schwingding]

I may be little, but I go long and fast.

 

[HT Nut]

Until you hit a tripwire SD