[Rclark]

http://news.cnet.com/8301-13645_3-20118768-47/monoprice-subwoofers-how-low-can-they-go/?tag=mncol;txt

 $57 8" sub
 $84 12" sub

 I think I have to try 4 of the 12" subs as a "swarm" for my small room application before I go ahead and build the OB servo subs. They're cheap enough to be a fun little experiment before my speaker mods are completed and before I need more serious subs to go with them.

 When I'm done with them in the stereo, I can just put them in the living room with my monitors for HT bass.

 I might instead do 4 of the 8's, or heck, even 6 of the 8's.

 Undecided. I just discovered these things ten minutes ago, but they look like a hoot. I'm sure the cabinets can be improved some. but 4 of them in my small space could be some very nice low end and I've never heard more than 1 sub in my room so that could be neat.

[decal]

Okay, I'll bite. is a "swarm" system? 

[jtwrace]

Okay, I'll bite. is a "swarm" system? 

mulitple subs spread around the room

[decal]

mulitple subs spread around the room

To imitate a "swarm" of bees I dare to guess !!!!! 

[Rclark]

Hey, I put in quotes, I didn't coin the term or the idea  . Come on, 4 8's for just under $250. All the benefits of multiple subs.

[Noseyears]

Hey, I put in quotes, I didn't coin the term or the idea  . Come on, 4 8's for just under $250. All the benefits of multiple subs.

This monoprice company products are being mentioned in most forums, it looks like they are building some reputation with their products. Definitely having 4 subs on a room its a basshead dream. 
All for a reasonable price.

[cujobob]

You have four subs around the room for better response, not for output. That comes as a part of it

[roscoeiii]

The CNET review suggested that the 8" was the more musical sub, and swarming would seem to increase the impact of the 8" to give a greater quantity of bass than that single 8" can put out. Or so it would seem. I am not a swarm expert at all (dual subs here, NHT SW2s FWIW).

[Rclark]

 So consensus is good idea? They can be turned down low where the sweetest possible, lowest distortion output would be. Is it true that each sub adds 3dB so four subs would be 16 times louder than the one alone? That would make 4 of them extremely efficient in my room and I could turn the gain down very low on each.

 I would add some extra bracing if possible and also no-rez or some alternative.

 The only thing that concerns me is he says the 8 only goes to 50hz but that must be a misprint, because the crossover control stops at 50 hz. Even the lousiest multimedia sub is going to go to 30hz so I have to believe that 30hz will happen with this sub.

 Did you see the pics with the grill off? It's kinda neat looking, it's got a fat port on it.

 Unless someone can convince me this is a horrible idea I think I might get around to ordering a pack of 4 8"s. I think for about $250 it should be pretty painless fun, and then, hey, I've got four little backup subs. Then again, they might be great and I just keep them a while.

 If I do this, should I keep my ported 10" in the mix? Five subs, one larger than the four?

  Edit: I just contacted tech support, they say it's a brand new unit and they don't have data on output, but he's going to get back to me in a few days to a week.

[Rclark]

... I also wonder if having 4 (or the 5) subs will lessen the amount of basstraps I need due to already smoothed response.

[BrassEar]

Earl Geddes invented the concept but I don't believe that he likes ported subs as much as sealed. He also advocates using different subs and not matched sets. 10-inch minimum.

This is an excellent guide to correctly using multiple subs.
http://mehlau.net/audio/multisub_geddes/

quotes from Earl:

"First my approach is not about what design of sub to use, I pretty much don;t care. I have not seen a big difference from the design or the maker, its all about the room and the setup. So I will de-emphasize the type and focus on the "how".

In my setup the room is special, its designed to be a listening room and it has extensive LF damping. This is always going to be an advantage. But the approach is the same no mater what kind of room you have. The idea is to use multple subs located around the room to smooth the spatial and spectral response at the seating location. The fact that multiple subs does this has been proven time and time again and really isn't an arguable point. IF you want the smoothest bass, then you must use multiple sources, no single source can compete. The room dominates the LF situation in any audio system and its the sources that must be accomodated to the room.

Sure its not great to have subs all over the place, but you have to get your priorities in order. Do you want the "best" bass or not, because if you do, you better get used to multiple subs. But rememebr that because there are lots of them, they don't have to be extremely large. Mine are about 18 x 16 x 14 for what I call the broad band subs which cover about 50 Hz - 150 Hz. These then overlap the mains, which are simple closed box. I use one Ultra Low Frequency sub that covers 25 Hz - 50 Hz for that lowest octave. At these frequencies only one sub is needed and it matters not at all where it is placed as long as its NOT in the middle of the room (given its size that would never happen.)

The most complicated part of using multiple subs is setup. To get it right you need some measurements to set the parameters on the sub amps correctly. This is done top get as smooth a response as possible. A detailed explaination of this technique can be found at DIY by Markus Mehkau and on his web site.

I am thinking about doing the setup calculations for multiple subs as a service to my customers, but this has to be worked out.

I use no EQ in my setup - although it could use some to improve it. The ideal setup would use something like a Behringer DCX9624, but I haven't bit the bullet and got one yet, because I'm not sure how much benefit it would be in my setup. As Randy has stated its pretty good the way it stands.

Finally all of my subs are very inexpensive, the plate amps about $100 and the B&C woofer about $150 makes up the bulk of the cost if you DIY, but the enclosures are pretty easy to build."

[srb]

A phase control can come in handy when trying to tune the swarm.  Although it seems the majority of subwoofers have one (either continuously variable or switched settings) the Monoprice subs do not have phase controls.
 
I would personally try and find some alternative subs with 10" drivers and phase controls.
 
Steve

[Duke]

I use the distributed multi-sub approach with Earl Geddes' permission, and call my system the "Swarm".   

My guess is that that little 8" sub is tuned fairly high, judging by the diameter of the port and the 50 Hz spec that was mentioned.   So you might want to try lowering the tuning frequency by decreasing the port's cross-sectional area.  I have a few ideas on how to do so if you'd like to hear them. 

In the modal region, the output from the four scattered subs will add in semi-random phase.  Below the modal region, in the pressure zone, their outputs will add in-phase.  This translates to +3 dB in the lower bass as compared to the upper bass regions.  So there is an argument for subs destined for a swarm to have a gentle built-in rolloff compared to a single bigger sub. 

[Rclark]

I use the distributed multi-sub approach with Earl Geddes' permission, and call my system the "Swarm".   

My guess is that that little 8" sub is tuned fairly high, judging by the diameter of the port and the 50 Hz spec that was mentioned.   So you might want to try lowering the tuning frequency by decreasing the port's
cross-sectional area.  I have a few ideas on how to do so if you'd like to hear them.

 Yes please!

In the modal region, the output from the four scattered subs will add in semi-random phase.  Below the modal region, in the pressure zone, their outputs will add in-phase.  This translates to +3 dB in the lower bass as compared to the upper bass regions.  So there is an argument for subs destined for a swarm to have a gentle built-in rolloff compared to a single bigger sub.

 So you are saying that by virtue of having four of these, low bass output will increase quite a bit versus using a single unit, and that upper bass output with the four will not increase as much with the four versus a single? In other words, I think you are saying that as you add subs, low bass output becomes more prominent.

 .... Do you agree that this sub is probably capable of going lower than 50hz? I ran a 6" multimedia sub for many years before starting this system of mine, and it played at 30hz no problem, and it probably had about 20-40 poor quality watts at best. If abused, it would actually rattle the walls a bit but it didn't quite fill the room like a real sub.

 Actually I had two of these once, and I had them both placed under a large solid steel desk (ran left satellite off the left amp and right under the right), and that was actually a pretty fun setup for that time.In that config they could be pretty loud. Very punchy and the reason I prefer a lot of punchy midbass for drums. Hopefully I can get that punch back into my system eventually with some servo subs.

[jtwrace]

Having a full Geddes system and setting one up I might know something about this.   

There is a fantastic paper on the Dr. Geddes forum.  If you can't get it just let me know and I'll send it to you. 

It's about the multiple sub approach not GedLee.

[Duke]

 Yes please!

 So you are saying that by virtue of having four of these, low bass output will increase quite a bit versus using a single unit, and that upper bass output with the four will not increase as much with the four versus a single? In other words, I think you are saying that as you add subs, low bass output becomes more prominent.

 .... Do you agree that this sub is probably capable of going lower than 50hz? I ran a 6" multimedia sub for many years before starting this system of mine, and it played at 30hz no problem, and it probably had about 20-40 poor quality watts at best. If abused, it would actually rattle the walls a bit but it didn't quite fill the room like a real sub.

 Actually I had two of these once, and I had them both placed under a large solid steel desk (ran left satellite off the left amp and right under the right), and that was actually a pretty fun setup for that time.In that config they could be pretty loud. Very punchy and the reason I prefer a lot of punchy midbass for drums. Hopefully I can get that punch back into my system eventually with some servo subs.

Without knowing the specifications of the woofer and enclosure I couldn't reliably predict how low that sub will go, but if you can give me an estimate of the internal volume and port dimensions (both diameter and length) I might be able to make a ballpark guess.

To lower the tuning frequency, get one tube for each sub, plastic or cardboard, slightly smaller in outer diameter than the inner diameter of the existing port.   Cut them maybe a bit longer than the exisiting port, and wrap the ends with just enough electrical tape to get a good friction fit.  Stuff them into the existing ports, and that will lower the tuning frequency. 

If you don't mind the new port sticking out a bit, cut it somewhat longer than the existing port, and adjust the location of the friction-fit tape accordingly. 

I've never actually tried this, but believe it would work.

[Rclark]

This is the only useful information you get:

13.75" x 11.75" x 11.75" for the 8".

Hopfully that tech support guy can hook us up with something useful. I like the idea of using a different port length and stuffing it with material. Hopefully we can soon know more about the sub. If it's feasable to get 30hz output, then I'll try a batch. Even if he doesn't get back with anything usable, I might just try one. Even if I don't like it, I can gift it out.

Hey, I have a really stupid question here. Not really a tool guy, Wish I had more hands on with them, it would make diy'ing things a lot easier, but I was thinking about what I might do to improve bracing, and I was imagining a set of of threaded rods threaded together at the center that you could stick into the box and then thread out until they are pressing against or into the parallel walls inside the box, or up against some kind of plates set against the same inside walls. Does something like that exist that I can get at the hardware store?

 ... I might also do something that I learned by doing the GR Insignia speaker mod, and that was to fill in any cracks and crevices inside with a hardening water putty. That was the first thing I did to those speakers and it surely did improve the boxes.

[doug s.]

So consensus is good idea? They can be turned down low where the sweetest possible, lowest distortion output would be. Is it true that each sub adds 3dB so four subs would be 16 times louder than the one alone? That would make 4 of them extremely efficient in my room and I could turn the gain down very low on each.

 I would add some extra bracing if possible and also no-rez or some alternative.

 The only thing that concerns me is he says the 8 only goes to 50hz but that must be a misprint, because the crossover control stops at 50 hz. Even the lousiest multimedia sub is going to go to 30hz so I have to believe that 30hz will happen with this sub.

 Did you see the pics with the grill off? It's kinda neat looking, it's got a fat port on it.

 Unless someone can convince me this is a horrible idea I think I might get around to ordering a pack of 4 8"s. I think for about $250 it should be pretty painless fun, and then, hey, I've got four little backup subs. Then again, they might be great and I just keep them a while.

 If I do this, should I keep my ported 10" in the mix? Five subs, one larger than the four?

  Edit: I just contacted tech support, they say it's a brand new unit and they don't have data on output, but he's going to get back to me in a few days to a week.

a few comments:
 - normally, doubling the drivers will equate to 3db additional spl.  so having 4 drivers instead of one should equate to 6db gain.  even if you sum the gain, you are looking at a 9db increase max.
- the 50hz spec for the 8" "sub" (really a woofer imo, not a sub), is cited not only in the article, but in two separate locations on the monopole site - in the description, and in the specs.  if it's not accurate, i would suspect it's because it's not even that low, not cuz it's lower - we are talking about an 8" driver, that, coupled w/an amp and a cabinet, is retailing for $57! 
- regarding "musicality", well, for a small cheap stereo system, a single 8" driver may be more "musical".  but, if you wanted real bass, you wuold still need a subwoofer!     for me, if i were really wanting anything approximating true low end, i would opt for the 12" model.  especially considering that using 4 of them will mean that you will be needing only about 1/4 the power to generate the same spl's as opposed to using a single sub.  this should increase the musicality of the larger unit sufficiently, imo.  plus, you are getting a 150wrms amp instead of a 60wrms amp...

if i were gonna be trying this, i would definitely be considering only 4 of the larger units.

ymmv,

doug s.

[Rclark]

 Well I simply can't believe the output is only to 50hz, that's just silly. And regardless, if 30 or close to it can be achieved with some adjustments, longer, stuffed port as Duke suggests, then I think I may still attempt it.

 The Klipsch Promedia sub was doing 30hz 8 or 9 years ago. Not loudly like a more legitimate subwoofer, but definitely there... and you could daisy chain several of them. Matter of fact, for a while, Klipsch had an add-on single 8" sub for the promedia system and you could daisy chain 16 of them together and make a wall of bass.

 The 12" wasn't as well receieved by the reviewer, but you're probably right, having 4 of them, less effort, better quality.

 The problem is the ship date for the 12 is some time in Jan and I think I'll probably be finishing up first go round on my room treatments, my speakers will be modded, and I'll be interested in checking out some OB bass at that time.

 If I do this at all, it will be in the coming weeks, to a month, and it will have to be the 8's or nothing.

 If it works out, the 8's can drop sufficiently low, and I can maximize them with any sort of simple mods, and they sound good in that swarm configuration, heck I might just run them for a while.

 Who knows, running a bunch of them like that might end up being more than decent, sort of a bare-minimum for ultra smooth bass for music in a small room like mine. My MMG's will take an apparently huge upswing in quality in about two months and needs will change.

[Duke]

Thanks for the dimensions, Rclark.

Okay the port diameter looks like about 3" to me, and the effective port length might possibly be 9.5", which would tune that box to about 50 Hz.  So I think their claim of 50 Hz is reasonable.

We don't know the shape of the curve because we don't know the woofer's parameters, but in general lowering the tuning frequency causes the rolloff to start higher up and become more gradual.

If we were able to reduce the effective port diameter to 2", and use a port length of 9" (which would leave about 2" clearance for the inner opening of the port inside the box), we'd drop the tuning frequency to about 35 Hz.   That is NOT the same thing as bass extension to 35 Hz, but we would have a gentler rolloff which in my opinion is more likely to be conducive to good bass quality than with the higher tuning. 

The smaller diameter inner port will begin to "chuff" at a lower SPL than the original port, but I would guess that the woofer in a $57 sub will go non-linear by exceeding x-max ("fartout") before port chuffing sets in.