I'm using a Velodyne CT150 and was thinking about adding a 2nd sub. So is it important to stay with another Velodyne sub. Also does it have to be the same size as my Velodyne CT150.
Quote:
Originally Posted by jsil /forum/post/20935044
I'm using a Velodyne CT150 and was thinking about adding a 2nd sub. So is it important to stay with another Velodyne sub. Also does it have to be the same size as my Velodyne CT150.
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Originally Posted by craig john /forum/post/0
I would not suggest:
*mixing 2 subs with significantly different output capabilities;
Quote:
Originally Posted by craig john /forum/post/0
*mixing subs with significantly different low frequency extensions;
Quote:
Originally Posted by craig john /forum/post/0
*mixing a ported sub with a sealed sub.
Craig
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Originally Posted by jaddie /forum/post/20936215
unless they are active, have level adjustments, and the lower output one is closer to the listening position...
careful positioning would minimize any adverse effects, if any, and maximize the benefits of multiple subs
Can't see where it matters how it works in this case. More subs always evens out sub coverage, even if dissimilar.
Ideally they should match. We don't live in an ideal world though. I'd always take multiple subs over a single, regardless of match.
Originally Posted by g_bartman I have four different subs in my theater and it's not an issue. |
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Originally Posted by craig john /forum/post/0
I stick by my recommendations.
I would NOT suggest mixing 2 subs with dissimilar outputs. The lesser output sub will limit the higher output sub. The lesser output sub will go into compression, distortion and possibly bottoming well before the higher output sub. The only alternative is to limit the higher output sub to the level of the loweroutput sub. Of course, one can mitigate this somewhat with nearfield placement of the leser sub and level reduction of the lesser sub. Still, if one is buying a new sub to mate with an existing sub, then it is ALWAYS better to choose a sub with similar output capabilities.
I would NOT suggest mixing sub with different low frequency extensions. The sub with lesser extension will add to the levels at all frequencies above the -3 dB point, but it will add little to nothing below that. When the combined levels of the subs are calibrated to the speakers, the level will be set on the combined levels. This will lower the levels of both subs, but the sub with lower extension will have it's deeper extension reduced in level, thus crippling the deeper extension. Using 2 similar subs won't increase the extension of either sub, but it will increase the useful levels of the deepest extesnion of the combined output.
I would NOT mix a sealed sub with a ported sub. A ported sub has a "tune point" of the port. At that frequency, the output of the port is predominant and it is driven by the backwave of the driver. Hence, the output of the ports is, by definition, out of phase with the rest of the output, which is driven by the frontwave of the driver. Sealed subs don't exhibit this phenomenon. If you mix a ported sub with a sealed sub, they can be in phase with each other at all frequencies except at the frequencies around the tune point of the ported sub, where they will be out of phase.
I completely agree with you about multiple subs being better than a single sub. However, system design is very important, as is system optimization. If one wants to integrate dissimilar subs, it is critical that one has the ability to measure the system and the know how to optimize it.
If I am advising someone considering a second sub about what sub to get, my best advise would be to get a 2nd of whatever they currently have, assuming they are content with the performance of whatever they currently have. A 2nd will net them 3 to 6 dB more output with similar LF extension, but more headroom at the -3 dB point. If they are not content with their current sub and they want more extension, then my advice would be to get a better subwoofer, and then save up for a 2nd of that better subwoofer.
Craig
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Originally Posted by jsil /forum/post/20935377
g_bartman,
The four subwoofers you have are they the same size.
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Originally Posted by jaddie /forum/post/20939126
You make some valid technical points in your post. They are correct, technically, but you miss some aspects of practical application.
First, the point about ported subs and phase response. This would create a huge issue if a ported and sealed sub both shared the same exact location. Their dissimilar frequency and phase responses could indeed be very detrimental. BTW, a sealed sub doesn't have flat phase response below cutoff either, but also won't have the same rolloff either, so serious phase cancellation would be highly unlikely anyway. But co-location is not what you do with multiple subs. They are placed deliberately at distances from each other so they can excite different room mode.
The big issue we address with multi subs is room modes. These result in huge response variations, location and frequency specific, and fairly unpredictable in location and magnitude. Multi subs is one of several ways to partially deal with this, but you can never eliminate a mode, and in fact, you don't want to. Having two subs that stimulate different modes lessens the effect of any one mode. Three or four subs does an even better job. Even if you have identical subs, placing them in different locations results in radically different modal equations for each location. They aren't there to add to each other in phase, or subtract out of phase, they are there to stimulate different modes filling in response nulls.
If the OP has two subs, any two subs, and places the lesser sub closer to the listening position, or in near field, compensates for inverse square law spl gain, and then calibrates, he will have a low cost option to compare to the single sub solution.
No, I wouldn't recommend dissimilar subs if you have to buy them, but if you have them, or the second sub is highly affordable, I believe the chances of improvement are excellent. I base this on my own hands on experience.
Single subs with room mode response issues always results in spacially uneven bass coverage. Multiple subs, properly located, does mitigate modal issues, even if they don't match.
I don't recommend it, but I've done it, it works, and there was no fracture in the space-time continuum.
Quote:
I'm using a Velodyne CT150 and was thinking about adding a 2nd sub. So is it important to stay with another Velodyne sub. Also does it have to be the same size as my Velodyne CT150.
Quote:
Originally Posted by craig john /forum/post/20935793
I would not suggest:
*mixing 2 subs with significantly different output capabilities;
*mixing subs with significantly different low frequency extensions;
*mixing a ported sub with a sealed sub.
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Originally Posted by Tom Vodhanel /forum/post/20936300
One important question is *why* you are adding the second unit?
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Originally Posted by craig john /forum/post/20941467
Although it seems you want to find ways to disagree with me, I think we both agree that the best answer to the original question is to get another similar sub. It will be much easier to integrate than a dissimilar sub.
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Originally Posted by craig john /forum/post/20941467
I still maintain that it takes much more work, and much more knowledge and measurement capability to get right.
Quote:
Originally Posted by craig john /forum/post/20941467
For myself, I'll take multiple *identical* subs all day, every day. Please see the link to my system in my signature to see how I've integrated multiple identical subs.
Craig
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Originally Posted by jaddie /forum/post/20942062
Ok, that's fine, and I'd prefer that too, so long as we realize that identical subs will not perform at all identically when placed in different locations. In fact, they will be radically different. It's never just about the sub, it's the sub AND the room, rather, the room and the sub (room comes first, sorry). And, in fact, that's the whole point. You need it "radically different" for the multi-sub idea to work!
Quote:
Originally Posted by jaddie /forum/post/20942062
So, stay with me a sec.... if you end up with radically different sub performance with identical subs in different positions, then what's the problem with subs of different design in differing positions? So long as you realize their performance limitations, and place them to their best advantage. Not to back away from that, but identical subs does make it a bit easier, particularly in the extreme LF, high SPL area. I just don't think I'd ever pick one sub in favor of two dissimilar subs, that just doesn't make sense, at least to me. I've never been able to place a single sub in a spot where it works evenly, smoothly, without response nulls, and the same for every seat. It's just not physically possible, room modes bite you in the kazoo every time.
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Originally Posted by jaddie /forum/post/20942062
Yes, precision measurement is important for any multi-sub setup, dissimilar or identical. Not sure what the reference to gain matching was in another post directed your way, but there's no reason to try to match gains only, it's the composite response in-room, and by the way, never in only one listening position! Complex, yes, but worth the effort, IMHO.
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Originally Posted by jaddie /forum/post/20942062
Not looking for ways to disagree, sorry if I come off that way. Opinions sometimes seem inflammatory when they aren't, it's a side effect of typing and not speaking. And I'm not rolling my eyes, just winking.
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Originally Posted by sivadselim /forum/post/20954203
nice thread
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Originally Posted by craig john /forum/post/20936383
I stick by my recommendations.
A ported sub has a "tune point" of the port. At that frequency, the output of the port is predominant and it is driven by the backwave of the driver. Hence, the output of the ports is, by definition, out of phase with the rest of the output, which is driven by the frontwave of the driver. Sealed subs don't exhibit this phenomenon. If you mix a ported sub with a sealed sub, they can be in phase with each other at all frequencies except at the frequencies around the tune point of the ported sub, where they will be out of phase.
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Originally Posted by stepyourgameup /forum/post/20956844
I have a question for you. When I place my SPL meter at the primary LP and I play the test tone from my Denon, I get higher SPL if the subs are set to different phases, ie one is set to 0 and the other is set to 180. Both ported subs are basically identical and they are both placed up front on either side of the center channel. Can you explain why this is the case? would having them set to different phases be detrimental in any way?
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Originally Posted by craig john /forum/post/20943982
To your comment about measuring in only one position, I will say that I run Audyssey using the full 8 positions, but when I measure the response afterwards, I generally only measure in the position I listen from. I really don't much care what the response is in other positions, but I can state that it's not terribly different than the response where I listen.
Quote:
Originally Posted by jsil /forum/post/20935044
I'm using a Velodyne CT150 and was thinking about adding a 2nd sub. So is it important to stay with another Velodyne sub. Also does it have to be the same size as my Velodyne CT150.