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How to set up 4 subs?


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19 replies to this topic

#1 of 20 OFFLINE   Mark_J_H_Jr

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Posted January 28 2005 - 12:51 AM

I saw a thread a while back about a fellow named Todd Welti, that did a study on optimum number and locations for subs. http://www.harman.co...df/multsubs.pdf . The results were that two were good and 4 were better.

With that in mind, how do you send the LFE from your receiver/pre-pro to 2 or 4 subs at a time? I am picturing a medusa looking cable that splits from one to 4 and going to the 4 subs. Is that how you would do it if you only have one LFE output on your receiver? Or do you daisy chain around the room?

What if you had separate amps?

That would get to be lots of cables.

Like the article says, you would get lots of output, and pretty smooth response.

Anyone tried spacing 4 subs around their room? If so, what are the results?
mjh

#2 of 20 OFFLINE   ThomasW

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Posted January 28 2005 - 03:06 AM

IMO the Harman article over simplifies the use of multiple subs and the issues involved with them.

How many people have a 20' X24" room with 9' ceilings, setup to seat 2 dozen people?

The reality is that the only way to know for certain if this is going to work in a room is to build 4 test boxes. Then see if you can duplicate the results of the Harman study.

The logistics of using splitters for the LFE singal and multiple amps doesn't really seem all that problematic.

#3 of 20 OFFLINE   Wayne A. Pflughaupt

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Posted January 28 2005 - 05:26 AM

I’m with Thomas, I wish they’d take that thing down. It’s been a while since I waded through it, and someone please correct me if I’m wrong, but if I recall there was no “real” test at all, it was all computer generated. It didn’t take into account important things like the phase issues you always get with multiple subs, which result in ragged response.

Even best-case, with any test like this the results are only relevant if you have an identical room. If your room has drastically different dimensions, the test doesn’t do you much good at all.

As far as feeding multiple subs or amps, that’s no big deal. You can simply daisy chain the signal from one to the next. You can use “y” splitters, or since most subs have L/R inputs that are internally summed, you can probably just use one jack for the signal input, and the other to feed the next sub. Either way you do it, yes it’s a lot of cable, there will be a certain amount of signal (read voltage) loss, but that’s why subs have gain controls.

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#4 of 20 OFFLINE   ThomasW

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Posted January 28 2005 - 05:49 AM

Quote:
but if I recall there was no “real” test at all, it was all computer generated.
Correct.....

#5 of 20 OFFLINE   Mark_J_H_Jr

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Posted January 28 2005 - 06:18 AM

Thanks Wayne for straightening me out about how to wire. I was considering building a sub/subs and am doing some homework on what might work best for my room. If multiple subs, then I would need to make sure I could daisy chain them together and have an amp that can adjust for gain.

Quote:
it was all computer generated

Actually, in the write up they do measure the response using 4 “AKG-C98 microphones suspended at ear height”. I have no idea what an AKG-C98 microphone is, BTW.

My room is 20 x 22.5 with 8 ft ceilings. So this analysis and demonstration got my attention since it does apply rather well with my situation. My room is nearly square, it is not the most musical of rooms.

When I went through the set up of my BFD, I noticed that moving the SPL meter away from the sweet spot made a big difference. The testing that was done by Harman sure makes sense to me. If you reduce the number of nulls in a room, you get a smoother response. No? Maybe I want to believe this is the panacea for my room. Posted Image

Is there anything I can check out to learn about the phase issue you mention?
mjh

#6 of 20 OFFLINE   Richard_M

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Posted January 28 2005 - 08:18 AM

Mark

As Thomas & Wayne have pointed out adding more subs also adds more issues.

Good on you for wanting to find out and experiment, just realise that you will need to add additional equipment to be able to set up each sub properly.

As an example I run 5x subs in my room, 4x at the front and 1x at the rear. I use a Behringer DCX2496 in circuit this allows me to split the LFE channel 6ways, I can set delays and phase controls for each sub independent of the others. The DCX also allows me to set parametric and High/Low/Band pass filters for each sub so I can customise each sub to roughly match up with each others in room freq response. Okay now ahead of the DCX I also run a DEQ2496 which I use to customize the overall in room response with all subs working.

To enable me to set these up properly I measured each sub using RTA software, then I started with 1x sub and got that right, then add the next and adjust this to match the first, and so on down the line.

I believe my system sounds fantastic (but then don’t we all), and others have been impressed with the response, but believe me there is no such thing as a free lunch, I say go ahead and experiment if you have the room and money to invest, just be prepared to invest some time as well.
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#7 of 20 OFFLINE   MichaelAngelo

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Posted January 28 2005 - 08:20 AM

FWIW when I clicked that link it goes to optimumonlinedotcom,
not harmon dot com.
HTH

#8 of 20 OFFLINE   Mark_J_H_Jr

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Posted January 28 2005 - 12:07 PM

Sorry about the link. I will get if fixed next time as soon as I get back to work.

Richard_M,

As far as subs go,I have a Beringer 1124P that I am using now. It only has two channels though. But it seemed to make a difference after I got it dailed in. So I think I understand where you are going with equalization. Perhaps the next level will require RTA software and working on adjusting the system. I certainly do not have a problem doing the work. Getting the time for me is the biggest problem these days.

One of the reasons, other than than usual "upgraditis", for looking at improving the low end is that I was listening to my son practicing drums. The base drum in his kit was so dynamic, it put my sub and speakers to shame. I am trying to find out how to get that same sort of slam from my system. Multiple subs seemed a likely option. (I have a SVS 20-39PCi) Multiple subs would move much more air that a single "super-sub" (lets leave a Genelc out of the equation for now).

So, in your system, with 4 subs across the front what sort of limitations are there without equalization and filters?
mjh

#9 of 20 OFFLINE   Bryan Michael

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Posted January 28 2005 - 02:29 PM

i would recomend just putting 1 large box with 4 large subs in the middle of the rear wall or in the middle of the front wall. i have 2 av15 in a large box and it is just awsome 120 db @10 feet @18 hz aka lotr ring drop sene
there are olny 2 types of people in the world the irish and thoes who want to be irish

#10 of 20 OFFLINE   Richard_M

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Posted January 28 2005 - 05:33 PM

Mark,

Quote:
So, in your system, with 4 subs across the front what sort of limitations are there without equalization and filters?


If the subs are stacked or placed next to each other then this shouldn't be too much of a problem, however once you start to separate them you then run into phase/delay problems as well as cancellation/modes, this causes the "Ragged Response" as Wayne so rightly puts it.

Quote:
One of the reasons, other than than usual "upgraditis", for looking at improving the low end is that I was listening to my son practicing drums. The base drum in his kit was so dynamic, it put my sub and speakers to shame. I am trying to find out how to get that same sort of slam from my system. Multiple subs seemed a likely option. (I have a SVS 20-39PCi) Multiple subs would move much more air that a single "super-sub" (lets leave a Genelc out of the equation for now).


Ahhh now I see the problem, you know for years I have been reading posts from audio gurus about how good some subs are at reproducing the "Thwack" of the kick drum, and yet I have never experienced this phenomena.

A friend of mine plays bass in a band. A couple of weeks ago he was filling in for another band, so I went along for a listen, especially since they were playing 5mins down the road from home.

To get to the point when I walked into the room, the sound was good and the Bass and kick drum were about normal to what I hear with other bands etc. Now here is the twist I got to sit along side the band on stage which was also behind the kick drum.

Well what can I say, the “Thwack” of that kick drum was nothing short of fantastic, I went out in front and the “Thwack” was no longer audible, during one of the breaks I was talking to some of the band members talking about “things”, and I mentioned what I had heard with regards to the kick drum, the sound guy told me he EQ’s it out for better sound in the hall, and this is standard practice, mind you the drummer was on my side and said it should be left in…

Now thinking about the EQ’d sound of the kick drum, and this is probably the norm of what I hear at most places, also the sound I get from my DVD’s and Cd’s is also very similar i.e. minimal to no “Thwack” based on the recording, and yet a lot reviewers of Subs talk about this “Thwack” from the kick drums when they do their testing, and until that night I had never REALLY heard it.

I am wondering if this is indeed standard practice to EQ this sound out, does anyone know of any cd’s or Hi-res discs that may have a good playback of this “Thwack”

I guess what I am saying you may not get the sound you are after from prerecorded DVD's/CD's.
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#11 of 20 OFFLINE   Wayne A. Pflughaupt

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Posted January 29 2005 - 10:47 AM

Quote:
The base drum in his kit was so dynamic, it put my sub and speakers to shame. I am trying to find out how to get that same sort of slam from my system.
You probably won’t be able to. The problem is the recordings we listen to. They all utilize considerable compression that “squashes” the dynamics of highly percussive instruments like drums. Probably not a bad thing, since most home systems simply wouldn’t be able to handle the equivalent of a directly mic’d drum kit, or many other live instruments for that matter

Quote:
I am wondering if this is indeed standard practice to EQ this sound out, does anyone know of any cd’s or Hi-res discs that may have a good playback of this “Thwack”
IMO kick drums are probably the most abused instrument in the recording process. If you’ve ever heard them live, you know that they are virtually never accurately reproduced. Not only is the “thwack” often EQ’d out (by that I assume you mean higher-frequency sound of the mallet striking the head), but abnormally low frequency energy is often dialed in for an artificial thump in the chest.

Regards,
Wayne A. Pflughaupt

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#12 of 20 OFFLINE   Mark_J_H_Jr

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Posted January 30 2005 - 06:06 AM

Let me recap what I think I have gotten so far:

1.Multiple subs either cause a ragged response or help optimize the modal response of the room.
2.Success is attainable using multiple subs if one is willing to EQ and phase align regardless of 1 above.
3.Recommendation of one large enclosure with 4 drivers versus 4 spaced around the room.
4.One through three don’t really matter because what I am trying to accomplish with recorded music is EQed out during the recording process.

Let me interject one of the systems I was attempting to target.

The best reproduction of percussion, or for music, I had the opportunity to hear was a system that had a pair of Maggie 20s. They were accompanied by 4 Tempest based subs spaced across the front of a room about 14 ft wide by 20 ft long.

I cannot say for sure if it was the Maggies or the 4 subs or room interaction, but the sound was great. The short amount of time I was able to listen to this set up was limited. And like many things, I may be remembering it better than it was. But I think I remember hearing the attack of the bass drum.

So if Wayne et al are correct, the target I am shooting for does not exist. And what I recall from the Maggie audition was incorrect. Now, that IS frustrating. So, should I aim for a different target? Posted Image

Another thought, although I fear I hear the cash register ringing. If I were to build 4 enclosures, what should be the top three drivers I should be comparing, Acendant, Adire etc? And what alignment? Could I keep the driver costs below $1,000?

Link to Harman article;

Welti
mjh

#13 of 20 OFFLINE   Wayne A. Pflughaupt

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Posted January 30 2005 - 12:54 PM

Quote:
So if Wayne et al are correct, the target I am shooting for does not exist. And what I recall from the Maggie audition was incorrect. Now, that IS frustrating. So, should I aim for a different target?
Sorry to rain on your parade, Mark – I sure didn’t mean to imply that pursuing accurate sound reproduction is a lost cause. Posted Image

Certainly, with a first-class system you can get very satisfying results. It’s just that no matter how good it is, there’s no mistaking it for live instruments. There is just too much conversion and processing between that and the reproduced product to expect that there won’t be some loss.

Not that that’s necessarily a bad thing. When you’re talking about a work with multiple instruments and/or singers, it takes equalizing, mixing etc. to ensure a viable, coherent product. If not, you just have an unlistenable mess.

Regards,
Wayne A. Pflughaupt

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#14 of 20 OFFLINE   Mark_J_H_Jr

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Posted January 31 2005 - 04:20 AM

Wayne,

My parade has been wet for years. Posted Image

For your edification, your posts on setting up a BFD were helpful when I went through the process. Posted Image

I likely will continue with room treatments and looking into improving the bass in the room.

The recommendations of trail and error may be the best path forward. MDF is cheap, and I may investigate building boxes to mount drivers. Find out if it is better to have subs spaced around the room versus having them grouped together.

What is the current cost effective driver of choice? One of the new Ascendant drivers? I had looked into the Adires a while back. I would prefer to build small sealed enclosures.
mjh

#15 of 20 OFFLINE   JohnI

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Posted February 11 2005 - 08:29 PM

Arent you suppposed to use a sub for each of the 4 main channels? Not just 1 channel split everywhere? That way your front right/left, and rear right/left each have a little sub. Playing what they play. The subs in surround...not mono.

Of course just splitting it would work but its just a mono channel of bass split around the room.
-johnybass

#16 of 20 OFFLINE   Brian Bunge

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Posted February 12 2005 - 12:42 AM

Mark,

Long time no see!Posted Image How've you been? From what I remember in the past, you were sort of toying with an IB sub. I think that's probably going to be your best bet if you can do it. Your front wall where your screen is mounted is also adjacent to your garage where that '65 Mustang sits, correct? I would think that if you can do an IB with 2/4 of the Ascendant Atlas 15's that you'd get the sound you are looking for. They allow for adjustable Q and you could still use your BFD to dial in some added EQ down low if you wanted.

BTW, what ever happened to the Atlanta HT forum? I've looked for it several times and it seems the old URL isn't active anymore.
Brian Bunge
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#17 of 20 OFFLINE   Wayne A. Pflughaupt

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Posted February 12 2005 - 09:48 AM

Quote:
Arent you suppposed to use a sub for each of the 4 main channels? The subs in surround...not mono.
Great in theory, not so great in practice. If you check the earlier posts in this thread, you see that multiple subs can be very problematic.

There are other issues as well. The only way to get true surround sound for four subs would be to feed them from the main channel pre-outputs. However, most people want to set their main speakers for “small.” Doing this would engage a high pass filter on the pre-outs, which means there would be virtually no signal going to the subs.

Regards,
Wayne A. Pflughaupt

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#18 of 20 OFFLINE   Dennis XYZ

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Posted February 12 2005 - 01:07 PM

Quote:
if I recall there was no “real” test at all, it was all computer generated.


Actually, they double-checked the results in a real room.

Quote:
Agreement between measured and calculated metrics is
good, providing justification for using modeled results.


#19 of 20 OFFLINE   Tom Rosback

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Posted February 18 2005 - 09:49 PM

I think what gets lost with the concept of multiple subs is that you resort to the pain of doing it to solve a specific problem you may be having. For instance, in my room, the seating is at the room midpoint, and I have a null there no matter where I place my Tumult. Its sad to see 3" of linear excursion on a 15" driver and hear no bass at some frequencies. So I'm experimenting with adding eq-ing, and phasing another sub in the rear. PITA.

I also like the effect of two subs or full range mains for stereo. But that creates so many problems in the theater, I'm back to a single sub in the front.

I'm loaded for bear with MLSSA and a calibrated mic, but getting this right is a painstaking process.
Tom Rosback

#20 of 20 OFFLINE   Mark_J_H_Jr

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Posted February 22 2005 - 11:32 AM

Hey Mr. Bunge,

Quote:
Long time no see! How've you been? From what I remember in the past, you were sort of toying with an IB sub. I think that's probably going to be your best bet if you can do it. Your front wall where your screen is mounted is also adjacent to your garage where that '65 Mustang sits, correct? I would think that if you can do an IB with 2/4 of the Ascendant Atlas 15's that you'd get the sound you are looking for. They allow for adjustable Q and you could still use your BFD to dial in some added EQ down low if you wanted.


Great memory!

Unfortunately, I have been working for a living. Or perhaps I should say I am thankful I have a steady paycheck. The 60 hour weeks and traveling have taken a toll on my time. Family takes up the rest of the few valuable hours. Perhaps I am having a "mid-life" crisis and am anxious to upgrade again. Or maybe just looking for a woodworking project. (I have way too many hobbies. Posted Image )

Yes I do have quite a volume where "Nellie Belle" sits all jacked up with no place to go waiting on me to put the master cylinder back.

Guess my problem is that I have yet to hear an IB sub.

Could I have the IB opening behind the thick black curtain I have across the front of the room? Or is there lots of attenuation and would need to cut the curtian back?

The more that I listen to son #2 playing on the drums do I realize how anemic the drum kits sound on CDs. Posted Image

(Brian - link to the mAHTG Atlanta Home Theater Group)
mjh


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