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post #1 of 17 Old 05-06-2014, 11:51 AM - Thread Starter
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hi guys i was needed some help and wondering what you would do in my situation. i currently have two svs pb13 ultras located in each of my front corners. my main listening position seems to be the "dead spot" it sounds amazing in the rear row and just ok in the front row. what i have decided is to buy 2 more subwoofers for the rear corners to hopefully get rid of the dead spots. my my dilemma is do i get 2 pc13 which will fit in each corner right now or do i get rid of one seat ( leaves me with four) and get 2 pb13 to match the 2 front subs? thought? thanks
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post #2 of 17 Old 05-06-2014, 11:57 AM
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Try moving one sub to the opposite back corner. It may resolve your null and is cheaper/easier/quicker.
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post #3 of 17 Old 05-06-2014, 12:14 PM
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Quote:
Originally Posted by paulfromtulsa View Post

hi guys i was needed some help and wondering what you would do in my situation. i currently have two svs pb13 ultras located in each of my front corners. my main listening position seems to be the "dead spot" it sounds amazing in the rear row and just ok in the front row. what i have decided is to buy 2 more subwoofers for the rear corners to hopefully get rid of the dead spots. my my dilemma is do i get 2 pc13 which will fit in each corner right now or do i get rid of one seat ( leaves me with four) and get 2 pb13 to match the 2 front subs? thought? thanks
Have you done the crawl? another option is to play around with REW room simulator (I found it fairly accurate with my very nearly rectangular room).

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post #4 of 17 Old 05-06-2014, 01:02 PM - Thread Starter
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Originally Posted by Ozzie Isaac View Post

Try moving one sub to the opposite back corner. It may resolve your null and is cheaper/easier/quicker.
ok i forgot to mention that in each of the the back corner i have a sunfire true subwoofer eq 10". and the dead spot or where the weaker bass is, is still the front row. im wondering if i just got rid of the sunfires and just used the pb13 in the opposite corners if that would sound better in the main listening position? thought?
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post #5 of 17 Old 05-06-2014, 01:04 PM - Thread Starter
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Have you done the crawl? another option is to play around with REW room simulator (I found it fairly accurate with my very nearly rectangular room).
what is the crawl? thanks
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post #6 of 17 Old 05-06-2014, 01:17 PM
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Quote:
Originally Posted by paulfromtulsa View Post

what is the crawl?

http://www.avsforum.com/t/1390040/subwoofer-crawl-question


Did you really need to quote that entire post in your reply?
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post #7 of 17 Old 05-06-2014, 01:20 PM
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what is the crawl? thanks
google 'sub crawl'… basically placing the sub at the main listening position, playing some familiar, bass-heavy content and crawling around the room listening for good sounding bass. Spots with good sounding bass are your best options for placement. Better than nothing, but there are other tools available now as well (including measurement and modeling).

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post #8 of 17 Old 05-06-2014, 02:10 PM
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Experimentation with multiple subs is the real answer. When using three or four subs, the sub crawl is not that useful. It works great with one sub.
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post #9 of 17 Old 05-06-2014, 02:40 PM - Thread Starter
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Quote:
Originally Posted by dougri View Post

google 'sub crawl'… basically placing the sub at the main listening position, playing some familiar, bass-heavy content and crawling around the room listening for good sounding bass. Spots with good sounding bass are your best options for placement. Better than nothing, but there are other tools available now as well (including measurement and modeling).

ok i know what this is but the reason i cant really do that is the only position i can put subs in the rear is the 2 corners and for the front along the front wall so when running 4 subs i figure the optimal position is all four corners. so back to my first question run 4pb13 with only 4 listening positions in the rear or run 2 pb13 in the front and 2 pc13 in the rear with 4 listening positions. thanks
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post #10 of 17 Old 05-06-2014, 02:47 PM
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Someone else had a similar issue and they said they changed the timings on the amp. By testing out different delays on one of the subs they fixed their dead spot. It was a recent post at least that was my understanding of what fixed it.
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post #11 of 17 Old 05-06-2014, 02:50 PM
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Quote:
Originally Posted by paulfromtulsa View Post


ok i know what this is but the reason i cant really do that is the only position i can put subs in the rear is the 2 corners and for the front along the front wall so when running 4 subs i figure the optimal position is all four corners. so back to my first question run 4pb13 with only 4 listening positions in the rear or run 2 pb13 in the front and 2 pc13 in the rear with 4 listening positions. thanks

Any possibility of placing each of the 4 subs in the middle of each wall?  I've read elsewhere that this placement option is the best.


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post #12 of 17 Old 05-06-2014, 02:52 PM
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post #13 of 17 Old 05-06-2014, 03:10 PM - Thread Starter
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Any possibility of placing each of the 4 subs in the middle of each wall?  I've read elsewhere that this placement option is the best.
no. the only place i can put the rear subs is in each corner but on the front i can put it anywhere along the front wall
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post #14 of 17 Old 05-06-2014, 03:34 PM
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Quote:
Originally Posted by paulfromtulsa View Post

ok i know what this is but the reason i cant really do that is the only position i can put subs in the rear is the 2 corners and for the front along the front wall so when running 4 subs i figure the optimal position is all four corners. so back to my first question run 4pb13 with only 4 listening positions in the rear or run 2 pb13 in the front and 2 pc13 in the rear with 4 listening positions. thanks

Multiple subs usually help with a more even response, with the exception of when limited placement options exist such that they only reinforce peaks and do nothing to fill nulls. This is the exception rather than the rule, but can happen. Before buying new subs, I'd try moving one of the two you have to the opposing rear corner (from the one remaining in the front) and see if that solves things (especially if you are only desiring a more even response rather than more headroom or deeper extension). Have you asked SVS about mixing the models? they are usually very helpful in cases like this. Also, as I previously suggested, if your room is rectangular (or nearly so), play around with REW room simulator and see what it thinks will work with two or four subs… try what it thinks is the best 2-sub placement (even if it is not a workable placement for you) to see if it models your room fairly closely (where your peaks and nulls are at the listening positions)… if so, its a pretty good bet that its 4-sub sim is fairly close as well… can't hurt, it is free after all.

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post #15 of 17 Old 05-06-2014, 03:52 PM
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Try moving the sub in the left corner closer to the TV, about 1/4 of the way from the left corn to the right corner. Do the same 1/4 from the right wall with the other sub. A few months ago I got my 2nd sub. A slightly similar placement to this helped me out. When I was pretty frustrated with the 2 sub combo for the first month or so. Now I see why everyone likes multiple. Good luck.

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post #16 of 17 Old 05-06-2014, 04:00 PM - Thread Starter
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Originally Posted by dougri View Post

Multiple subs usually help with a more even response, with the exception of when limited placement options exist such that they only reinforce peaks and do nothing to fill nulls. This is the exception rather than the rule, but can happen. Before buying new subs, I'd try moving one of the two you have to the opposing rear corner (from the one remaining in the front) and see if that solves things (especially if you are only desiring a more even response rather than more headroom or deeper extension). Have you asked SVS about mixing the models? they are usually very helpful in cases like this. Also, as I previously suggested, if your room is rectangular (or nearly so), play around with REW room simulator and see what it thinks will work with two or four subs… try what it thinks is the best 2-sub placement (even if it is not a workable placement for you) to see if it models your room fairly closely (where your peaks and nulls are at the listening positions)… if so, its a pretty good bet that its 4-sub sim is fairly close as well… can't hurt, it is free after all.
i have talked to svs and they say that either the pc or pb would be fine. the pb does out perform the pc but not by much i think they said 2 db. the reason i think it will sound better is that right now i am mismatching subs. i am running the sunfires and svs's. also the pbs are ported and the sunfires are sealed but have that passive radiator so i dont know how well the 2 different type of subs mix. but when i just run the svs's and turn off the sunfires it doesnt sound as good even in the best listening position. i am pretty dead set on getting 4 svs subs. i would love for all of them to be pb13 but dont want to give up the extra seat in the rear. so thats why i considered the pc13 but then now i am running 2 different subs even though both are ported with the same driver and amp.
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post #17 of 17 Old 05-06-2014, 04:05 PM
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You discussed a dead spot but did not mention if you have checked to see what frequencies are not showing up in the dead spot. It would be beneficial if you could do a check with some test tones to know which frequencies are a problem. As mentioned above changing the timing through either sub phase adjustments or distance settings may fix the problem frequencies by minimizing the wave cancellations.

Once you know which frequencies are a problem you can make a phase change on a single sub and see if it improves the response.

You mentioned that you have placed two sun fire subs in the back. Replacing those subs with more powerful/capable subs will not fix your problem if the cancellations are happening above 40hz.

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