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post #1 of 12 Old 09-17-2018, 11:26 AM - Thread Starter
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Question Sub Help - Dual Subs, Small room? SVS Upgrade!

First, thank you for taking the time to read the below and please see attachments for a visual. I have a fairly small room 14Lx11Wx10H which ends up being a mixed use of my office and a personal theater. Only one seating so just the MLP - there can only be one! My problem is that I've done the sub crawl, test tones from 20-80hz, and moved the sub all over the room. The place it sounds the best is near field on the left side of my seating position. In general I don't have a problem with this, but it can feel localized. Sometimes I'm not sure if it is actually localized or if it is just my mind knowing the sub is just to the left of me.

So based on that I went down the road of should I get dual subs to maybe help the FR (I don't always get that hit me in the chest feel that I have had with this same sub in a different room) and eliminate the localization. I have a UMIK-1 on order and it should be here Wed to get an idea of what my current environment is. But for now I started playing with the Room Sim - and this is where things went down hill. What it shows in the room sim does not at all line up with what I am hearing/feeling in my room. The room sim (see attachments) says the best place should be in the front corners. But in reality if I do that I barely feel anything at all. I think this may have something to do with all of the "stuff" in my room as opposed to room sim thinking it is an empty room/blank walls. The other issue is room sim doesn't seem to show dual subs near field at the MLP will help, the SPL for the 15-30hz range actually slopes down as compared to a single sub in my current position.

My main questions are:

Will I truly benefit from dual subs or is room sim right? I am coming up on my 1 year SVS upgrade time (currently have a single PB13-Ultra and looking to get dual PC-4000s) and I need to make a decision soon to upgrade or not. I don't want to buy something and then end up in the same place I am today.

Does the stuff in my room affect room sim this much?

Any recommendations?


Current equipment:
A/V:
LG 65 OLED B7A
Onkyo RZ920 (running in 7.1.4)
2 Channel amp (for rear surr)
Nvidia Shield
Sony X700 4K BR Player

Speakers:
SVS Ultra bookshelf L/R
SVS Ultra Center
SVS Ultra Surrounds in duet mode
SVS PB-13 Ultra (looking to upgrade to dual PC-4000s)
Klipsch RP-140SA (4 height mounted on the wall near the ceiling)
Attached Thumbnails
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Name:	Current Layout.JPG
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Name:	Current Layout Dual Subs.JPG
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ID:	2456426   Click image for larger version

Name:	Room Sim Ideal layout.JPG
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ID:	2456428  

Last edited by dgrizzard; 09-18-2018 at 03:55 AM.
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post #2 of 12 Old 09-17-2018, 02:00 PM
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Since you have a small space to fill and seating is only for one I would put the sub directly behind you for nearfield placement. You will get the best bass response/ tactile sensation. Try that and see how you like that compared to how you have the sub placement now.
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post #3 of 12 Old 09-17-2018, 02:26 PM
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Quote:
Originally Posted by dgrizzard View Post
First, thank you for taking the time to read the below and please see attachments for a visual. I have a fairly small room 14Lx11Wx10H which ends up being a mixed use of my office and a personal theater. Only one seating so just the MLP - there can only be one! My problem is that I've done the sub crawl, test tones from 20-80hz, and moved the sub all over the room. The place it sounds the best is near field on the left side of my seating position. In general I don't have a problem with this, but it can feel localized. Sometimes I'm not sure if it is actually localized or if it is just my mind knowing the sub is just to the left of me.

So based on that I went down the road of should I get dual subs to maybe help the FR (I don't always get that hit me in the chest feel that I have had with this same sub in a different room) and eliminate the localization. I have a UMIK-1 on order and it should be here Wed to get an idea of what my current environment is. But for now I started playing with the Room Sim - and this is where things went down hill. What it shows in the room sim does not at all line up with what I am hearing/feeling in my room. The room sim (see attachments) says the best place should be in the front corners. But in reality if I do that I barely feel anything at all. I think this may have something to do with all of the "stuff" in my room as opposed to room sim thinking it is an empty room/blank walls. The other issue is room sim doesn't seem to show dual subs near field at the MLP will help, the SPL for the 15-30hz range actually slopes down as compared to a single sub in my current position.

My main questions are:

Will I truly benefit from dual subs or is room sim right? I am coming up on my 1 year SVS upgrade time (currently have a single PC13-Ultra and looking to get dual PC-4000s) and I need to make a decision soon to upgrade or not. I don't want to buy something and then end up in the same place I am today.

Does the stuff in my room affect room sim this much?

Any recommendations?

Hi,

I have several observations. First, the room sim may or may not be a reliable predictor of the best subwoofer location. I have seen results all over the map on that. Second, the stuff in your room should not affect the overall frequency response that much. I like the suggestion to try putting your existing subwoofer directly behind your seating position. That would be even more in the nearfield, where room modes would have less effect, and it might help with localization.

We can sometimes get localization cues from bass sounds and sensations, so I wouldn't assume that your occasional ability to localize or "notice" bass coming from the left is entirely psychological. If you aren't getting the chest punch you used to get, it may be that you have some cancellation occurring in about the 60Hz to 80Hz range, or from the position of the MLP. (More later on that.)

But, if you have a UMIK coming Wednesday, then I would put all of the speculation on hold until you have had a chance to measure the room and see what you actually have now in the way of a frequency response. If you do have some cancellation occurring near the crossover to the speakers, you may be able to address that with a sub distance tweak, or by adjusting the phase on your PC13.

I would measure with your sub where it is now, and both listen and measure with a rear nearfield placement, making whatever tweaks are required. But, I also wouldn't totally rule-out upgrading to dual subs yet either. Matching the left-wall sub, with a right-wall sub, would give you a potentially workable location for dual subs. Opposing mid-walls can often work well. And, there are other placement combinations you could try. I just think it's a little too early to tell whether you need a second sub yet, until you have had a chance to work with REW a little.

One thing that I see in your drawing that concerns me a little, if it's rendered accurately, is the location of your MLP. It appears to be awfully close to the center of the room's long dimension. If so, you could be getting some cancellation just due to your MLP location. If you could move the MLP back a foot or two, to get a little further off that center line, it might help, irrespective of other factors. There are also some things that you can do to enhance your mid-bass chest punch, but I would start with better MLP positioning, and REW, first.

Regards,
Mike
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post #4 of 12 Old 09-17-2018, 02:55 PM
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I most likely will not be able to help you but I had the same problem. I have a small room (13x15.5x10feet) too. I had one 15" servo sub in the room and for the life of me I was not able to get the sub in the right position and at times localization was problem. Even in some positions the sub would sound like it was coming from the left even though it was on the right side.

I talked to a lot of "experts" and did some tests with Bass traps but the end conclusion was that the combination of my small room and soundproofing made my room no ideal for my sub.

I sold my sub and was going to move to dual 12" subs until the kids took over the room.
It may sound strange but the only time Bass was perfect in the room was when I ran my towers full range and used two large speakers as "subs". I did not have deep bass but the bass was smooth.

Your solution just might be multi-subs. I would not get bigger subs as you do not need much with that room.
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post #5 of 12 Old 09-17-2018, 03:51 PM - Thread Starter
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Quote:
Originally Posted by mthomas47 View Post
Hi,

I have several observations. First, the room sim may or may not be a reliable predictor of the best subwoofer location. I have seen results all over the map on that. Second, the stuff in your room should not affect the overall frequency response that much. I like the suggestion to try putting your existing subwoofer directly behind your seating position. That would be even more in the nearfield, where room modes would have less effect, and it might help with localization.

We can sometimes get localization cues from bass sounds and sensations, so I wouldn't assume that your occasional ability to localize or "notice" bass coming from the left is entirely psychological. If you aren't getting the chest punch you used to get, it may be that you have some cancellation occurring in about the 60Hz to 80Hz range, or from the position of the MLP. (More later on that.)

But, if you have a UMIK coming Wednesday, then I would put all of the speculation on hold until you have had a chance to measure the room and see what you actually have now in the way of a frequency response. If you do have some cancellation occurring near the crossover to the speakers, you may be able to address that with a sub distance tweak, or by adjusting the phase on your PC13.

I would measure with your sub where it is now, and both listen and measure with a rear nearfield placement, making whatever tweaks are required. But, I also wouldn't totally rule-out upgrading to dual subs yet either. Matching the left-wall sub, with a right-wall sub, would give you a potentially workable location for dual subs. Opposing mid-walls can often work well. And, there are other placement combinations you could try. I just think it's a little too early to tell whether you need a second sub yet, until you have had a chance to work with REW a little.

One thing that I see in your drawing that concerns me a little, if it's rendered accurately, is the location of your MLP. It appears to be awfully close to the center of the room's long dimension. If so, you could be getting some cancellation just due to your MLP location. If you could move the MLP back a foot or two, to get a little further off that center line, it might help, irrespective of other factors. There are also some things that you can do to enhance your mid-bass chest punch, but I would start with better MLP positioning, and REW, first.

Regards,
Mike
Thanks to all three of you for the replies so far. While I wait for the UMIK-1 I will try what you've suggested and move my MLP back a few feet, leaving the sub where it is and test that. Then try it at my current MLP with the sub rear near field. I am close to the 50% mark - around 6 feet from the back wall of the closet of the 14' length, so that is a possible issue. Thanks again and I will report back with my findings.
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post #6 of 12 Old 09-17-2018, 04:51 PM - Thread Starter
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Just to follow up, moving back the MLP was an improvement, but it does mess with my surr/rear surr. Moving to the rear placement was a vast improvement. Once I get the UMIK I will run REW to see where I am now with the rear MLP and side MLP I had before. Thanks again and I will update back when I have the REW results.
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post #7 of 12 Old 09-17-2018, 06:50 PM
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Are you able to try opposite diagonal corners, or does the closet in the back of the room preclude that?

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post #8 of 12 Old 09-18-2018, 03:51 AM - Thread Starter
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One corner I cannot use (upper right) due to the desk. I have tried placement in the other 3 corners, including placing the sub inside the closet (as much as it would fit anyway) with the driver/port facing out through the door. But the sound from the corners was pretty muted. So far the best two I have done were the near field on the side and then what I have right now (better than side) which is near field in the rear.
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post #9 of 12 Old 09-18-2018, 04:14 AM
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Quote:
Originally Posted by dgrizzard View Post
One corner I cannot use (upper right) due to the desk. I have tried placement in the other 3 corners, including placing the sub inside the closet (as much as it would fit anyway) with the driver/port facing out through the door. But the sound from the corners was pretty muted. So far the best two I have done were the near field on the side and then what I have right now (better than side) which is near field in the rear.
I suspect you have a standing wave cancellation/null in the middle of the room. With that said, duals in opposite diagonal corners, when properly phased, will very often fill-in that null. I think it's worth a try once you get REW and start experimenting/measuring.
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post #10 of 12 Old 09-18-2018, 05:33 AM
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Quote:
Originally Posted by dgrizzard View Post
One corner I cannot use (upper right) due to the desk. I have tried placement in the other 3 corners, including placing the sub inside the closet (as much as it would fit anyway) with the driver/port facing out through the door. But the sound from the corners was pretty muted. So far the best two I have done were the near field on the side and then what I have right now (better than side) which is near field in the rear.

I suspect that Ed and I are right about some cancellation occurring near the middle of the room, due to the position of the MLP. That would be pretty typical with a listening position located near the center point of a rectangle or a square. It is something that you will be able to test once you are measuring. You also mentioned that moving the MLP threw-off your surrounds and rear surrounds.

I don't know whether you recalibrated, with some sort of auto-calibration system when you tried moving your MLP, but that re-calibration would normally compensate for distance/volume changes of all of the surround channels. It's also possible that moving backward less aggressively will help you to hit a sweet spot, where you are getting less cancellation, without messing with your other channels as much.

I think it may be helpful to put the discussion in context, too. Your original question was whether or not you should upgrade? I would love to see you upgrade to dual PC4000's. First, the 4000 series subs are a little better than the 13 Ultra's they replaced, and they offer some cool features. Second, there are advantages to having dual subs, including increased undistorted headroom, better FR, and better bass envelopment (the sense that bass sounds and sensations are coming from everywhere). And, the PC4000's would give you more placement flexibility in tight spaces than the PB13 does.

But, if you can achieve the results you are looking for by moving the MLP slightly, and/or by positioning the PB13 rear nearfield, then you may not "need" to upgrade. I have used a rear nearfield sub in a large room for several years, and I really like that location. But, I use it in conjunction with other subwoofers. I am afraid that I would be able to localize a rear nearfield sub operating by itself. That is something that you will have to determine through experimentation. If you can't localize it, then you may have found a solution without upgrading. If you can still localize a single subwoofer, then I am pretty sure that some combination of MLP and dual PC4000's will be a successful solution.

One of the nice things about SVS is the free-trial period. You could always order one PC4000 to try in conjunction with your PB13--they would be compatible. If they work well together in diagonal corners, or on opposing side-walls (perhaps with some distance or phase tweaking), then you could exchange your PB13 for a second PC4000. You have lots of options, and one of them is almost certain to work well for you.

Regards,
Mike
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post #11 of 12 Old 09-18-2018, 10:05 AM - Thread Starter
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Ah, let me clarify the surr/rear surr - I just meant I will need to re-position them if I do move the MLP. Yeah, my main concern right now is to upgrade or not. When I get my UMIK tomorrow I can run REW and get some concrete numbers on what my single sub options are and what they look like. I definitely don't have a problem with the upgrade and the finance committee is good as well. I just don't want to go through all of the hassle (shipping, moving, packing, returning, etc) if it isn't going to make a difference. Probably more so I would feel a little down about 2 subs not working, just not sure what my other options would be in this room to make it better. Don't get me wrong though I am pretty happy with the rear placement now, but I always have that nagging in the back of my head of can it be better? I think that's what I'm chasing right now.
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post #12 of 12 Old 09-19-2018, 03:36 PM - Thread Starter
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Ok so UMIK arrived and REW has been run. Just based on my little knowledge I *think* the two best candidates are opposite corners or two at the room mid point side walls. Both options with my MLP moved to 2 feet off the back wall. I have it all in the attached REW file, but the original MLP looked pretty bad no matter where I had the sub.

If I do go dual subs, it looks like the side wall/midpoint option at least looks the best to me. Where one measurement was down on a certain frequency range the other side of the room measured high/higher in that same range. So it should even the FR and get rid of a lot of my dips. At least that is my theory anyways. It would be great if some of you could take a look, let me know what you think, and if dual subs would help my situation or not.

Thanks!

I've attached three files, two are screenshots of the overlay, 1 for the two midpoint measurements (green/pink) and 1 for the opposite corners measurement (red/brown). The other file is the REW file.
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Name:	Opposite-corner-placement-new-mlp.png
Views:	21
Size:	150.2 KB
ID:	2457228  
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File Type: zip PB13Ultra-Single.mdat.zip (698.9 KB, 5 views)

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