# Should I add a 2nd sub?



## lexx2004 (Jun 5, 2007)

I’m thinking of adding a 2nd sub for use with both music and HT. I’d like to get some suggestions on what to go with. I currently have an HSU VTF3 MKII with Turbo. I know that there are pros and cons to having more that one sub. Pros being that you get more bass and could possibly smooth out your frequency response. Cons being cost (not really a factor for me) and complexity of integrating more than one sub. The latter point is something I’m willing to work with. I haven’t gotten a BFD yet but I will (also considering the SMS-1). I’ll likely take Sonnie’s advice (mentioned in another thread) and run the two subs using only one cable (and a y-splitter) and EQ them together rather than separately and having to combine the results. 

I should note that I’m very happy with the extension of the VTF3 MKII with turbo as I can go to approx 16 Hz. (it seems to be deep and loud enough). 
What sparked this upgrade is the fact that most people seem to be running at least 2 subs to even out the sound of the bass in their rooms. It’s not that I feel I need more bass. I just want the system to sound balanced. 

My room is 15x20 with 9 foot ceiling (approx 2700 sq. feet). My system consists of JBL S310II (floorstanding mains – rated down to 35 Hz), JBL S-Center II, and JBL S36II surrounds, Arcam AVR300 receiver, Shanling T-80 tube CD player….

Should I get?

1.) Another of the exact same sub
- I guess this will just give me more bass, in general
2.) One that goes even deeper (eg. SVS PB13 Ultra). 
- not sure if this will cause problems as one will go deeper than the other
3.) An HSU MBM-12 (mid –bass module). See link here (http://www.hsuresearch.com/products/mbm-12.html). 
- HSU recommends this option. Supposedly this option will add to my mid bass punch. I know that brucek (mentioned in a different thread) is not sold on this concept of splitting the sub frequency but I’d like his thoughts on why he feels it’s not necessary or not a good idea to go this route. 

Thanks for any advice.


----------



## Sheep (Feb 16, 2008)

Get the Exact same subwoofer again (even with the turbo). Then experiment with room placement to see where they play the flattest.

SheepStar


----------



## JCD (Apr 20, 2006)

:yeahthat:

I'll have to admit I don't remember the specifics, but I'm sure that's the right answer -- not that it's exactly the same, but you wouldn't mix your mains would you?

And I'm pretty against the mid-bass module -- just seems to me that it introduces another crossover into the equation making it even more difficult to get it right.

So, like Sheep said, get another one exactly the same and play around with placement.

JCD


----------



## Sheep (Feb 16, 2008)

JCD said:


> :yeahthat:
> 
> I'll have to admit I don't remember the specifics, but I'm sure that's the right answer -- not that it's exactly the same, but you wouldn't mix your mains would you?
> 
> ...


The MBM-12 is a gimmick. It adds to part of the sub bass spectrum that is already handled perfectly by your subwoofer, yet at the same time doesn't go nearly as low. 

Audioholics has an article on placing subwoofers and dual subwoofers. They show some setups that have a remarkably flat responses. The easiest to facilitate is opposing corners, and I think mid side wall on each side was another good one.

SheepStar


----------



## lexx2004 (Jun 5, 2007)

Thanks Sheepstar and JCD for the quick responses.


----------



## jakewash (Nov 29, 2007)

Do you know someone you could borrow a sub from to try it out? You may not really need to add one as your room is not huge. Maybe a better placement of your current sub could give you a flatter more even response.

I know of a number of people running 2 or more subs in rooms not much larger than yours and they said it made a difference but were not sure if it was the price of another sub better. I know of a few others with much larger rooms and they are running 3 subs and love the extra response, so it is up to you.

I believe it is easier to calibrate multiple subs of the same make but it is not necessary and remember when calibrating, the extra sub will add about 3db to the overall SPL so you can set both of them back a few db to even them to the mains.


----------



## Sheep (Feb 16, 2008)

jakewash said:


> Do you know someone you could borrow a sub from to try it out? You may not really need to add one as your room is not huge. Maybe a better placement of your current sub could give you a flatter more even response.
> 
> I know of a number of people running 2 or more subs in rooms not much larger than yours and they said it made a difference but were not sure if it was the price of another sub better. I know of a few others with much larger rooms and they are running 3 subs and love the extra response, so it is up to you.
> 
> I believe it is easier to calibrate multiple subs of the same make but it is not necessary and remember when calibrating, the extra sub will add about 3db to the overall SPL so you can set both of them back a few db to even them to the mains.


Credible research has shown that no matter how large the room there will still be room modes. The easiest way to tame dips is to add another sub and properly place. You can't EQ a dip that much before you really stress the subwoofer. And treating the room in a way to fix bass anomalies would cost much, much more then a second subwoofer.

SheepStar


----------



## lexx2004 (Jun 5, 2007)

My room has a fair bit of acoustic treatment done to it (e.g. panels at all reflection points and bass traps in all four corners). I'll try running the 2nd sub and see how much of a difference that makes. 
Thanks so much for the responses.

One other question. I'm getting a custom sub cable designed to split the sub signal going to the two subs. I'll run it out of the BFD but one sub is approx 8 feet from the BFD and the other (when I get it) will be approx 24 feet from the BFD. For signal integrity and signal arrival times to each sub, should I keep them the same length (i.e., 24 feet to each from the BFD) or does it not matter (ie. 8 feet to one and 24 feet to the other)?


----------



## Ray3 (Feb 4, 2008)

Matching the first sub makes terrific sense, especially with that Hsu - it's a beast.

You will benefit by having smoother bass, a little more headroom and possibly a bit more extension. In fact, you might do well to get the other Hsu without the turbo and eliminate the turbo you have.

Your problem will be finding/eliminating the nulls, but once past that point, it's all pure enjoyment.


----------



## WmAx (Jan 26, 2008)

As others have stated, you should ideally use multiples of the same sub-woofer. Combining different model subwoofers can add more (unwanted) variables - such as if the subwoofers have a substantially different phase rotation point around roll-off - there by causing unexpected cancellation(s) due to mutual interaction - in addition to the complex room acoustics.

For the processor - a Behringer DCX2496 would be ideal - not only can it individually process up to six different outputs - it is also a superb crossover to run both the mains and subs through to gain ideal integration between the two.

-Chris


----------



## lexx2004 (Jun 5, 2007)

Ray3 said:


> In fact, you might do well to get the other Hsu without the turbo and eliminate the turbo you have.


Yeah, I was thinking about that because buying another Turbo for the second sub will cost another $300 approx. The turbo allows the sub to go deeper though (16 hz) and play loud so it's a tough call. The turbo allows for much more air flow (due to the two 4" ports that are open at all times). Without the turbo I might run into distortion and loss of output down below 20 Hz. The sub without the turbo has 2 3" ports (only one of them is left open when you tune the sub to 18 Hz). Do you still think that I shouldn't add the turbo?:scratchhead:


----------



## lexx2004 (Jun 5, 2007)

WmAx said:


> a Behringer DCX2496 would be ideal - not only can it individually process up to six different outputs - it is also a superb crossover to run both the mains and subs through to gain ideal integration between the two.
> 
> -Chris


Are there any advantages of the DCX2496 over the BFD 1124P. From reading online, I thought that the 1124P was preferred because it has more presets (which I'll need - 1 for music - flat, 1 for movies, house curves for both etc.). The DCX2496 only has one preset...correct?


----------



## dieselpower1966 (Nov 26, 2007)

everything that I've read on dual sub setups says "use identical subs" the reason is this. you don't want your good sub trying to compensate for the lesser sub. with both subs being equal, you don't have that problem. and yes, that means if you intend on keeping the Turbo, get a second. also check out the THX website, they show some basic sub positioning, I have my 2 subs in my front left and right corners, approximately 1 ft. from the back and side walls, I'm actually using them as stands for my front left and right channels.
good luck


----------



## WmAx (Jan 26, 2008)

lexx2004 said:


> Are there any advantages of the DCX2496 over the BFD 1124P. From reading online, I thought that the 1124P was preferred because it has more presets (which I'll need - 1 for music - flat, 1 for movies, house curves for both etc.). The DCX2496 only has one preset...correct?


The DCX can do a lot more things than the BFD. As far as presets, the DCX has 60 internal memory preset spaces that you can use. It also has a memory card slot which you can use to download or upload settings, or simply use to expand the number of settings.

-Chris


----------



## Magialisk (Jan 17, 2008)

I just added a second sub to my setup and I've been extremely happy with the results so far. I was originally running a single SVS CS-Ultra at the 16Hz tune off of one side of a Crown XLS-602 amp. Just a couple weeks ago I found a guy locally selling a used CS-Ultra and nabbed it for less than half the original MSRP.

Anyways, more to the point, I have a pretty large room at just under 7000 cu. ft. One sub is in the front right corner and the other is about 10 ft. to the left of it about midway down the long front wall shared between my living and dining rooms. The graph with REW isn't really any more or less flat than it used to be, I still have huge peaks in the 40-45 area and a huge null around 72. The null that always annoyed me at 18Hz got a little better but not much. Placement didn't seem to be much of a factor in this case. What did change was a measured increase in SPL of 5dB across the board, so I decided to plug an extra port on each and go for the 12 Hz tuning.

Unfortunately I have another big null at 12 Hz which is frustrating, but overall the subs in tandem play both louder and lower than the single sub used to, and listening closely during loud passages I haven't heard any signs of bottoming. I may do some further experimentation with placement in the future but my options are very limited due to aesthetics. In the end, I think a second sub can be a great addition as long as you're using something like a BFD to keep things under control.


----------



## imbeaujp (Oct 20, 2007)

dieselpower1966 said:


> everything that I've read on dual sub setups says "use identical subs" the reason is this. you don't want your good sub trying to compensate for the lesser sub. with both subs being equal, you don't have that problem. and yes, that means if you intend on keeping the Turbo, get a second. also check out the THX website, they show some basic sub positioning, I have my 2 subs in my front left and right corners, approximately 1 ft. from the back and side walls, I'm actually using them as stands for my front left and right channels.
> good luck



I have the same configuration: 2 subs under L and R speaker. I plan to add 2 more subs for LS and RS.

I love the sound with 2 subs, you can extend the good bass to more listening positions.

JP


----------



## conchyjoe7 (Aug 28, 2007)

I have no idea of your age, but let me give you an analogy. Getting and having 2 subs is kinda like the first time you got a TV with a remote control (I unfortunately am old enough to remember when this was extremely uncommon)...once you had it there was no going back. Same result with 2 MATCHING subs. The difference is far more than subtle and you'll never look back. :T
Cheers,
Konky.


----------



## lexx2004 (Jun 5, 2007)

Thanks everyone for your advice. I was able to purchase a 2nd of the same sub used. Can't wait to get it all set-up.


----------



## Bigdaddy999 (Nov 12, 2006)

SO? how is the dual sub setup??


----------



## bsoko2 (May 9, 2007)

Don't listen to those who say that the MBM-12 doesn't do any good. The MBM is proven addition to any main sub and can help with room anomilies. I'm running two MBM-12's, one with each main and two 3.3's, one Turbo & one without.
Get a MBM-12 to go with your 3.3 Turbo and you will enjoy the best in bass!

Bill


----------



## mdrake (Jan 31, 2008)

ThomasW from HTguide posted this link http://www.harman.com/wp/pdf/multsubs.pdf
The conclusion was that two subs placed in front and in back showed very good results.

Matt


----------



## lexx2004 (Jun 5, 2007)

I haven't had a chance to try the dual configuration as yet since I'm in the process of moving. Probably won't be able to for about another month. I'll report back when I do. Thanks again everyone for your input and suggestions.


----------



## Blaser (Aug 28, 2006)

lexx2004 said:


> Should I get?
> 
> 1.) Another of the exact same sub
> - I guess this will just give me more bass, in general
> ...


I have dual subs... and I think your very best option is no 1, then no 2. I give you a third recommendation maybe: sell the HSU and get the Pb13 Ultra and add a second in the future if you feel you need more (most expensive but most effective upgrade).


> - HSU recommends this option. Supposedly this option will add to my mid bass punch. I know that brucek (mentioned in a different thread) is not sold on this concept of splitting the sub frequency but I’d like his thoughts on why he feels it’s not necessary or not a good idea to go this route.


I do not recommend an MBM unless you are already satisfied with bass and just adding it for extra punch and fun, but this is not true subwoofing.


----------



## Blaser (Aug 28, 2006)

bsoko2 said:


> Don't listen to those who say that the MBM-12 doesn't do any good. The MBM is proven addition to any main sub and can help with room anomilies. I'm running two MBM-12's, one with each main and two 3.3's, one Turbo & one without.
> Get a MBM-12 to go with your 3.3 Turbo and you will enjoy the best in bass!
> 
> Bill


Can you post a FR at LP with all subs firing?


----------



## bsoko2 (May 9, 2007)

blaser said:


> I have dual subs... and I think your very best option is no 1, then no 2. I give you a third recommendation maybe: sell the HSU and get the Pb13 Ultra and add a second in the future if you feel you need more (most expensive but most effective upgrade).
> 
> I do not recommend an MBM unless you are already satisfied with bass and just adding it for extra punch and fun, but this is not true subwoofing.


And just what is "tru subwoofing"????? Do you know what you are talking about?????

Bill


----------



## Blaser (Aug 28, 2006)

bsoko2 said:


> And just what is "tru subwoofing"????? Do you know what you are talking about?????
> 
> Bill


Bill,

I know what I am talking about, but it seems you just don't know who you are talking to... Let's have a nice talk and respect forum rules. You are willing to help and I am sure you are a nice guy :T. We may have different point of view but we should be nice to each other.

What I mean by "true subwoofing" is equal output at all frequencies starting from at least 20 Hz for a "balanced" experience.
Pls let us see your FR if possible, I would like to see the effect of your MBMs on FR.

Thank you!


----------



## bsoko2 (May 9, 2007)

blaser said:


> Bill,
> 
> I know what I am talking about, but it seems you just don't know who you are talking to... Let's have a nice talk and respect forum rules. You are willing to help and I am sure you are a nice guy :T. We may have different point of view but we should be nice to each other.
> 
> ...


Check out the HSU sub charts and you will see the benefit of using a main sub and MBM-12: http://www.hometheatershack.com/for...index-subwoofer-tests-manufacturer-model.html. Large rooms like mine (6000 cu ft.) benefit greatly by mutiple subs and also with the addition of mid bass subs. This concept is not new and is just now getting some popularity. It solves alot of room anomiles. Here is how I have the subs set up: Both my 3.3 (MO) and 3.3 Turbo set at 50hz (co-located near field, behind the couch). Both MBM-12's (one with each main) are naturally set for 50hz to infinity (dial all the way up) and the cross over on the receiver LFE set at 150hz. Reason for high LFE cross over is that the MBM's take the strain off the mains mid bass so the tweeters can get the full benefit of the 200 watts from the amps. It works and sounds detailed.

Enjoy the sand, Bill


----------



## jakewash (Nov 29, 2007)

That sounds to me like you really only need bookshelf speakers and even at that small ones, as the mains don't get much of anything below 130hz.


----------



## bsoko2 (May 9, 2007)

jakewash said:


> That sounds to me like you really only need bookshelf speakers and even at that small ones, as the mains don't get much of anything below 130hz.


The mains will always get bass no matter what the LFE setting is. LFE takes some of the bass from the mains, not all. Amember of the HSU forum did the same thing that I did and this post and links in the post will further explain the reasoning for my setup: http://forum.hsuresearch.com/showthread.php?t=3855&highlight=crossover).

Thank you, Bill


----------



## jakewash (Nov 29, 2007)

But isn't the spec for LFE 80hz and lower for the audio tracks when mixed? If so that would mean your receiver is taking the extra frequenies away from the mains. I am surprised you can adjust your LFE XO that high. Otherwise you would be getting some dialogue out of the MBM's. Do you use an MBM with your center channel too, as it would seem to need that boost as well to equalize across the front and take that load off you amp.

I always thought the MBM was made to help with Hsu's bookshelf system have better upper bass/midrange capability.


----------



## bsoko2 (May 9, 2007)

jakewash said:


> But isn't the spec for LFE 80hz and lower for the audio tracks when mixed? If so that would mean your receiver is taking the extra frequenies away from the mains. I am surprised you can adjust your LFE XO that high. Otherwise you would be getting some dialogue out of the MBM's. Do you use an MBM with your center channel too, as it would seem to need that boost as well to equalize across the front and take that load off you amp.
> 
> I always thought the MBM was made to help with Hsu's bookshelf system have better upper bass/midrange capability.


You can set your LFE xover to whatever you are comfortable with. 80hz is simply a THX spec. Anything above aprox. 120hz will localize your sub but in my case it there is no localization as my true sub is xover at 50hz. There is no dialogue from the MBM's. Others have done what I have done and they report no issues.

Bill


----------



## jakewash (Nov 29, 2007)

I see, you were not talking about the specific LFE channel as set in movie soundtracks but the usual subwoofer crossover.


----------



## Blaser (Aug 28, 2006)

bsoko2 said:


> Check out the HSU sub charts and you will see the benefit of using a main sub and MBM-12: http://www.hometheatershack.com/for...index-subwoofer-tests-manufacturer-model.html. Large rooms like mine (6000 cu ft.) benefit greatly by mutiple subs and also with the addition of mid bass subs. This concept is not new and is just now getting some popularity. It solves alot of room anomiles. Here is how I have the subs set up: Both my 3.3 (MO) and 3.3 Turbo set at 50hz (co-located near field, behind the couch). Both MBM-12's (one with each main) are naturally set for 50hz to infinity (dial all the way up) and the cross over on the receiver LFE set at 150hz. Reason for high LFE cross over is that the MBM's take the strain off the mains mid bass so the tweeters can get the full benefit of the 200 watts from the amps. It works and sounds detailed.
> 
> Enjoy the sand, Bill


Bill,

I am afraid you are not addressing my request. The link you gave is Ilkka's tests on differents subwoofers (that I already know by heart). What I need is your systems FR (at home) just to see how things look like. By the way, even HSU differenciate between an MBM and what they call a true subwoofer and therefore I can't understand why you were surprised by "true subwoofing".
MBM is unfortunately not the best way to correct room anomalies for 2 simple reasons:
- it is limited to 50 Hz
- it does not have a continuously adjustable phase setting (only 0 - 180), and while you might be lucky it works well in your setup, it might not work in another...
It also looks to me like you do not have very capable mains and therefore MBMs may be a good addition to your fronts, but again OP did not mention anything about the fronts if I am not mistaken.


----------



## bsoko2 (May 9, 2007)

blaser said:


> Bill,
> 
> I am afraid you are not addressing my request. The link you gave is Ilkka's tests on differents subwoofers (that I already know by heart). What I need is your systems FR (at home) just to see how things look like. By the way, even HSU differenciate between an MBM and what they call a true subwoofer and therefore I can't understand why you were surprised by "true subwoofing".
> MBM is unfortunately not the best way to correct room anomalies for 2 simple reasons:
> ...


Main sub xover is set at 50hz to down, the MBM is naturally set at 50hz to up - what is the problem with that? All you are doing is splitting the sub bass between two subs. This is not new! I have never ran any tests to track the room freqs. No need to, the ear is always the best and not all rooms or subs are the same.

Bill


----------



## Blaser (Aug 28, 2006)

So you're definitely not addressing eventual room anomalies with MBM...By the way, if you're happy with your setup, that's fine...enjoy!


----------



## jagman (Jul 8, 2006)

lexx24:

How's the move coming along? Have you had the chance to experiment with sub location? I'm really curious about having equal subs centered in the front and rear (the Harman alignment). If you've tried it, how does it sound?

I exchanged e-mails with the author of that paper and he said the front sub should be in phase with the mains, and that the rear sub's phase should be set so it fires at exactly the same time as the front suib (no delay). To me, what that means is the only way the front and rear subs would be "in phase" is if the seated position was exactly half way between the two subs. It seems kind of weird, but he wrote the paper. He also said the out of phase nature of not sitting in the middle is what allows the rear sub to fill in the valleys and drop down the peak in the in room frequency plot. Lastly, he said the central location (right to left) should minimize any localisation that occurs. But, a lot of that is theory... I've been told by someone else who's tried the two sub Harman alignment that localisation of the rear sub occurs above 50 Hz (probably due to proximity). Please comment! Thanks .


----------



## lexx2004 (Jun 5, 2007)

jagman said:


> lexx24:
> 
> How's the move coming along? Have you had the chance to experiment with sub location? I'm really curious about having equal subs centered in the front and rear (the Harman alignment). If you've tried it, how does it sound?
> 
> I exchanged e-mails with the author of that paper and he said the front sub should be in phase with the mains, and that the rear sub's phase should be set so it fires at exactly the same time as the front suib (no delay). To me, what that means is the only way the front and rear subs would be "in phase" is if the seated position was exactly half way between the two subs. It seems kind of weird, but he wrote the paper. He also said the out of phase nature of not sitting in the middle is what allows the rear sub to fill in the valleys and drop down the peak in the in room frequency plot. Lastly, he said the central location (right to left) should minimize any localisation that occurs. But, a lot of that is theory... I've been told by someone else who's tried the two sub Harman alignment that localisation of the rear sub occurs above 50 Hz (probably due to proximity). Please comment! Thanks .


I just completed the move but I'm still a ways away from the set-up. I need to do some acoustic treatment first. I've read a few articles on dual sub placement and I'll likely go with the left and right locations (mid way in the room against the side walls). I'm not sure how phasing would work for that positioning though. Let me know if you have any thoughts on the phasing.

Thanks,


----------



## Blaser (Aug 28, 2006)

lexx2004 said:


> I've read a few articles on dual sub placement and I'll likely go with the left and right locations (mid way in the room against the side walls). I'm not sure how phasing would work for that positioning though. Let me know if you have any thoughts on the phasing.


If you use the same subs and amps, a spacing of 3-4 feet shouldn't generate any phase issues 80Hz and below. So, that's generally 1/3 and 2/3 rd front wall to accomplish that assuming a moderately sized room. That eliminates the lateral mode but not the axial. I wouldn't space subs too much otherwise you may need phase treatment, which many times won't produce good coupling at all frequencies...That's my 2 cent.


----------

