Axiom Home Page Forums General Discussion Home Theater Working with two different brand subwoofers

I am sure this is a topic that has been covered to some extent but it probably bear5s repeating. I presently have an old velodyne subwoofer. I plan on getting either the new 350 or HSU VTF 2 v 3. If I use both subs in my system how do I go about setting them up. For instance: Do I use the same crossover point. How do I adjust the loudness and figure out the phase settings? Also, how do I place them? Also, I know the HSu and Axiom are superior. Am I better off just using the one. I am in a fairly large basement with ceramic floors. However, my listening area is fairly small maybe 10 x 12, with my couch set against a back wall. The m60's are angled and about 8 feet from the listening position and about 6.5 feet apart. Thanks in advance for your suggestions.

I would use both on opposite walls and then calibrate them at the same time. Both should have the same crossover, as it is usually done through your receiver and the subs' filter is on bypass. This should be a good starting point, this is what I plan to do when I get my next sub.

I am sure others with more dual + sub experience will be along shortly and have more to say.

When I was running dual Hsu Vtf 2s I calibrated each separately @ -3 db from reference. Running both subs at once you gain the 3 db back.

What about phase?

I think phase has alot to do with the room dynamics and the exact spots of the subs.

I left the phase @ 0, this seemed to give the best output for my room.

Sure, Eddie, the same crossover that you set in your receiver would have to apply to both subs since they're both receiving the same signal from the sub out(bypass the sub's internal crossover if it has that option; if not, turn it to the highest setting to get it as far away from interfering with the receiver's crossover as possible). The crossover frequency is of far more significance to the speakers than the sub anyway.

Although the subs receive the same signals, different efficiency and room placement might lead to different sound levels. The subs should be calibrated separately and the levels balanced by using the level adjustment on the back of the subs.

The best placement to help minimize the effect of room modes would be at the midway point of the opposite side walls(or the front and back wall).

Different subs aren't the ideal arrangement, but you should certainly use both if they're available and see how you like the effect.

yes.



This is a generic suggestion because your room acoustics will be unique. But in a typical room I would first start with making sure once again that all your speakers are level balanced at 75db. Lower the subwoofer level at the receiver to -5 to minimize distortion and give you room to raise it. Next set up one sub A on the mid sidewall and adjust level so it is 70db on the rs metre and 0 deg phase. Turn off sub A Then set up the other sub B right beside it so it is colocated follow the same steps above. Now turn oon both subs. Measure combined output. It should be very close to 76db and the subs are working properly. Turn off both subs again.

Then put the other sub B on the opposite sidewall but just off perpendicular, so its not exactly across (the idea being to make it slightly asymetric since I've found its just a bit smoother off that perpendicular axis). Adjust level to 70db again at the new placement. Next set the phase in that sub to 180 deg so the woofers facing each other are moving out of phase. The idea is not to maximize output from reinforcing peaks but to smooth response so there is less volatility on your RS metre. Depending on your room 0 degrees may be smoother (not louder from reinforced peaks). Now turn on both subs and measure output. Depending on how far they are from each other the coupling effect will give you a combined output between 70bd to 76db. At 72.5db the subs output will be level with the speakers. Now adjust the subwoofer level on the receiver to taste, remembering that anything above 72.5 will be running the subs hot. Chill drinks and get the popcorn ready.

How about 3 or 4 subs, same idea?

I like the way you think, Randy. I can't wait to have 4 EP600s in my huge dedicated basement home theater.

Pretty much Randy except when testing the subs to make sure they are working properly, additional output will increase by 6db with 2 subs, 9db with 3 subs and 12db with 4 subs.

For setting phase on sub C you will need to experiment with both settings. With 4 subs set up the subs across from each other like I suggested above.

I don't think I'll every be able to get 3 more 600's.$$$$$$ However, I've tossed the idea around about 3 more new350's or 400's possibly.

How big is that HT space again? I remember it was huge. In which case you may be better off adding a 500/600 to get the output.

Here is an old drawing back in the days of my 500, but should give you an idea. The 600 is now placed on the left wall right below the first wall treatment panel close to the front left speaker. I was thinking about putting the 600 back up front under the center channel since it looked cool. Then, get 2 or maybe 3 more subs.

One would go along the left wall, one would go on the shorter right wall below that panel, and the third could be daisy chained off the left one and maybe be placed along the back wall. My drawing is a little off as the back window and walkout door should be moved a bit to the right, so I have some wall back there for a 4th sub. The bad part is I would have a long coax going along the entire length of the side wall to the back wall.

There's nothing wrong in general(unless you mean aesthetics if it isn't concealed) with runs of coax that long, Randy. The losses are very small(especially at sub frequencies) until the run gets into hundreds of feet and can be disregarded.

Randy that space is in the order of 7000cf. You need output with that sized room if you want to feel the LFE bass. I would stick with the 500s or 600s. You don't need the benefits of a small sub in that huge space since even a 500 would look inconspicuous. For the $$s I would keep adding 500s or if you want them matched a 600 and then 500s. For the same price I would add 2 500s instead of 3 350v3s. A sub beside the seats and possible one behind the seats on the backwall would be worthwhile placement options depending how well you can dial them in.

Yes, before I bumped out the AV closet it was over 8,000.

thanks for the help. Now I just need to come up with how to fund this idea. Lets see, what can I sell.

You can always buy the drivers, the amps, power cables and the folded horns from Axiom and build the boxes yourself.

In my set up I really don't have a right side wall. That is, I have a left sidewall that runs about 12 feet, a front wall that runs about 20 feet, a back wall that runs about 10 feet. Obviously the right wall is about 20 feet away. My listening area is pretty much confined to the 10 by 12 area. Would you still recommend putting the sub on the right side wall even though it is so far from my listening area. There is also additonal basement area extending out from that front wall. Or am I better off confining my subs to the listening area.
Thanks

I'm running a SVS PB13 and HSU VTF-2 in my living room. Both are calibrated flat to 85 DB with the mains and running them together they run 3 db hot. I have phase at 0, as they are on the same wall and both up front with my mains. Run a splitter off the back of the receiver, turn one off calibrate, do the same with the other. Actually the amp on my old VTF-2 just went kaput so I'm trying to get it repaired now.

Bill3508

Eddie, it isn't entirely clear from your description how your listening area is laid-out, especially the 20' front wall compared to the 10' back wall. Nevertheless, the idea of placing two subs at the opposite midpoints of either the side walls or the front and back wall(to minimize the effect of room modes, as researched in the Harmon paper and also summarized by Alan in this month's Axiom newsletter)requires that they be placed at the side(or front and back)walls, even if that isn't considered part of your regular "listening area".

Here's the best I can do without drawing tools:


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This is the shape of my room with location of speakers. How would you suggest I place the subs.

Ummm....I don't think that worked.

No it certainly didn't. But if you can picture the middle line as the back wall of my listening area and draw an imaginary line from the right edge of the middle line you have my listening area, Left and right speakers are about 6 inches from each side and about 12" from the front wall. I have a couch butted up against the mid wall and my surrounds pretty are pretty much line up with the fron speakers over the couch against the mid wall. In my picture I was trying to give the impress of the inverted C nature of my basement. The front wall extends another 8 feet right of the imaginary marker and then extends about 20 feet down. My question is do I keep one sub along the imaginary axis or extend it all the way right against the sliding door closets on the right that aren't really in the confines of my listening area. I hope this explains things better.

Eddie, I think that I've got the rough idea of the layout. These positioning concepts we keep referring to are designed for a more symmetrical arrangement, but my thought would be to try a front/back wall(yes, right behind the couch)combination, with the axis being the middle of the 10' back wall.

I have no room behind the couch. The couch butts up agains that mid wall. Any other suggestions?

Move the couch.

can't do?

Here's another attempt at describing my room

LFS___________________TV_______________RFS_______________________
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l Right Wall------------------------------------------------------>

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Midwall_____________________________________(End of back wall)***

StairCase___________________________________(end of Stair Case)**








Backroom Area
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Where should the subs go? Can I put one sub i the open area on the right side or must it butt up against a wall?

Deleted my post.

I was making fun of his ASCII drawing by inferring that it meant he must secretly be this person in real life, followed by an ASCII picture of Dilbert. The picture turned out crappy though and I have no time to fix it.