Multiple Subs

[ACV92]

8 minutes ago, CECAA850 said:

You're not going to boost a null with eq.  The best you can do is drop the peaks or move your listening position

 

Agreed.  That's what I've seen so far.  With my initial results I had the low pass set at 60, BW 12 db.  I ended up with the low pass at 75, with a 3.5, 4, db boost at 67.5, in the middle of the void, with a relatively high Q to try and narrow the boost to that particular bandwidth.  Funny thing is, with my worn out SW-10 I had a void in the 50 hz range.  With the UMAX it's in the 60's.  Question though, my old AVR has a low pass set at 200 hz.  No large, small, crossover setpoint, etc.  So, my KG 5.5's run at full range.  I measured with sub, mains active.  Could there be a cancellation with delay that is creating the 60 void?  Would positioning of the sub possibly change it?  Just curious.  Thanks!

[ACV92]

12 minutes ago, jason str said:

The null could just be the microphone position as well.

This is a Radio Shack SPL meter.  I mounted it on my camera tripod, with mic top at my ear level, centered in my listening position.  I need to get a Umik with REW software to really see what my little setup is doing.  I tested multiple times within that range to see what affects my PEQ, crossover settings had.  So, yeah, you could be totally right that with my SPL meter I'm 'seeing' something that may not be there.  I have to say though, I do love the DSP function of the 3000 DSP.

[derrickdj1]

Multiple subwoofer integration with the mains.  This is a complicated process to cover in one or two post.  Also, is there any advantage of using all the same type and size subs.  The issue of phase cancellation has to also be considered.

 

First, you can't perfectly time align multiple subwoofers.  It does not matter if they are identical subs or mixed.

 

Second, you can only  align the direct reflection of one subwoofer to a single spot.  There will be secondary reflections that will interfere with perfect alignment.

 

Third, take two, three or four subs and multiply that by every boundary in the room.  This multiplied number is the number of spots one would have to time align.  This is impossible because you can set a delay for a reflection or change the phase.

 

Fourth, there is light at the end of the tunnel. For the same reasons that subs are omnidirectional and a group delay lag up to 25-30 ms are not audible in the small HT.  This is what allows for good results with sealed and mixed subwoofers in the same system, and also the use of non-identical subwoofers.  No problem if they are all the same either.

 

There is a need for a permanent sticky in the subwoofer section for subwoofer setup and integration on multiple subwoofer.  With skillful EQ, this is not as difficult has it appears.  For my 8 subs all asymmetrically placed, I use no more than 2-3 EQ filters and the first one is a boost down low.  So, the EQ process does not have to be a nightmare.

[derrickdj1]

The issue of 2 lesser subs vs one really good sub is a frequent topic.  There is no right or wrong answer.

If you have the ability to get a second subs down the road, get a really good sub.  If size problem, then two smaller subwoofer will offer more benefit.  This will give better bass coverage that can't be achieved with one sub.  My preference is to add subs in pairs.

 

[wvu80]

There are several extensive threads on AVSforums.com on setting up multiple subs.  Mtg90 is well respected on the subject.

http://www.avsforum.com/forum/155-diy-speakers-subs/1713458-mtg90a-s-multiple-subwoofers-mains-integration-how-thread.html

 

+++

This thread drift to multiple subs has been good for me.  It challenged my assumptions that multiple subs should all match.  I matched a 12" ported sub with a 15" sealed because that is what I had and I assumed this was a bad idea which I made worse with poor implantation, even though it generally sounds pretty good to my ears.

 

[wvu80]

Duplicate post.

[Paducah Home Theater]

 

6 hours ago, jason str said:

 

 

I'm not going to provide any graphs, take my word or don't as its no worry of mine.

 

Did you finally buy a microphone?  I honestly didn't realize that you owned one.  Last I checked you didn't.  

[derrickdj1]

Matt is one of our Chicago area guys.  This topic has been covered in part at some of our local GTG and the GTG I had back in Oct. of 2016.  My approach is different than Matt's but, will get the same results for the most part.  Matt's post is great for those using REW.  My approach is with Omnimic but, most of the basic concepts are very similar.

[ClaudeJ1]

5 hours ago, jason str said:

The THT i sold you had a budget driver installed as mentioned before sale, the frequency response may have differed from published graphs, i never had a chance to measure it. The driver was approved by Bill so i went with it.

 

My current THTLP is near flat from 18 - 85 Hz where it falls off quickly on both ends but works perfect with the La Scala's. A bit of EQ on the sub and some on the La Scala bass bin made a world of difference.

 

I'm not going to provide any graphs, take my word or don't as its no worry of mine.

I think you missed my point. First I was very happy with that sub, the driver, and it's performance. Primarily, it's  shape just didn't fit the living room, blocking a through way unacceptably. In the basement, the room dimensions changed curves drastically, which was discovered by listening and measurement from my listening position. In the horn mouth it was reasonably flat, but that's not where we listen, right?

 

I'm sure you THTLP is very good also, but you are still talking a single sub, and not TWO, which is what the OP was trying to solve. My response was about that.

 

No worries here either, but in order to disagree with you, I had to show that I had done it successfully. Although, admittedly, my success might have had a little luck thrown in along with good practice and measurement. After all, it's always a SYSTEMS approach, but the ROOM always dominates, no matter how we use to  "shake the air."

[ClaudeJ1]

2 hours ago, ACV92 said:

My point being, I don't see the negative in using different subs, as long as they're tuned right.

I agree with this notion for sure.

[ClaudeJ1]

57 minutes ago, jason str said:

The null could just be the microphone position as well.

YEP, more than likely.

[ClaudeJ1]

41 minutes ago, ACV92 said:

This is a Radio Shack SPL meter.

The RS SPL meter is NOT very good in the subwoofer range. UMIK and REW is the way to go and works with any windows computer with a USB port..

[ClaudeJ1]

27 minutes ago, derrickdj1 said:

Multiple subwoofer integration with the mains.  This is a complicated process to cover in one or two post.  Also, is there any advantage of using all the same type and size subs.  The issue of phase cancellation has to also be considered.

 

First, you can't perfectly time align multiple subwoofers.  It does not matter if they are identical subs or mixed.

 

Second, you can only  align the direct reflection of one subwoofer to a single spot.  There will be secondary reflections that will interfere with perfect alignment.

 

Third, take two, three or four subs and multiply that by every boundary in the room.  This multiplied number is the number of spots one would have to time align.  This is impossible because you can set a delay for a reflection or change the phase.

 

Fourth, there is light at the end of the tunnel. For the same reasons that subs are omnidirectional and a group delay lag up to 25-30 ms are not audible in the small HT.  This is what allows for good results with sealed and mixed subwoofers in the same system, and also the use of non-identical subwoofers.  No problem if they are all the same either.

 

There is a need for a permanent sticky in the subwoofer section for subwoofer setup and integration on multiple subwoofer.  With skillful EQ, this is not as difficult has it appears.  For my 8 subs all asymmetrically placed, I use no more than 2-3 EQ filters and the first one is a boost down low.  So, the EQ process does not have to be a nightmare.

I agree with this. According to Geddes, we must excite as many room modes as possible in order to smooth out the bass, especially for more than 1 seat.

[jason str]

2 minutes ago, ClaudeJ1 said:

The RS SPL meter is NOT very good in the subwoofer range. UMIK and REW is the way to go and works with any windows computer with a USB port..

 

 

The Dayton UMM-6 is another good option.

[ACV92]

So, I guess my question to everyone is this.  If you could have a choice of 2 scenarios, which would you choose?  Scenario one, two 15's ported/sealed, with two 8's ported/sealed, or scenario two, only two 15's ported/sealed.  To my layman brain, I would choose scenario one.  Why, I could tune the 8's to the upper low end, tune the 15's to pick up where I'm cutting the 8's.  Why, to me, certain size drivers are better suited to perform given tasks.  Hence, why we don't use 4" diameter dome tweets for our highs.  

[ACV92]

3 minutes ago, ClaudeJ1 said:

The RS SPL meter is NOT very good in the subwoofer range. UMIK and REW is the way to go and works with any windows computer with a USB port..

Noted.  Next on my birthday wish list.

[jason str]

11 minutes ago, MetropolisLakeOutfitters said:

 

 

Did you finally buy a microphone?  I honestly didn't realize that you owned one.  Last I checked you didn't.  

 

No more borrowing, finally picked one up when i purchased the Mini DSP.

[derrickdj1]

Omnimic is a great tool and easy to learn as another option for taking measurements.  It is more expensive but, one can be up and running in 20 min.  It will take several days for the new user to learn the in's and out's of REW.  The manual is around 90 pages.

[ACV92]

1 minute ago, jason str said:

 

No more borrowing, finally picked one up when i purchased the Mini DSP.

Let us know how you like the mini-DSP.  I've been considering getting one for my baby HT setup in the basement.

[Paducah Home Theater]

3 minutes ago, ACV92 said:

So, I guess my question to everyone is this.  If you could have a choice of 2 scenarios, which would you choose?  Scenario one, two 15's ported/sealed, with two 8's ported/sealed, or scenario two, only two 15's ported/sealed.  To my layman brain, I would choose scenario one.  Why, I could tune the 8's to the upper low end, tune the 15's to pick up where I'm cutting the 8's.  Why, to me, certain size drivers are better suited to perform given tasks.  Hence, why we don't use 4" diameter dome tweets for our highs.  

 

Just doesn't matter with subs nowadays.  Some of the best and highest extending and most accurate midbass drivers are 18's.  Better to match than to try to partake in such things.  It's a solution to a problem that doesn't exist.