I.B. Subwoofer

[crytklmass]

im currently building a HT in my basement. Dimensions will be 16 ft wide, 22 feet deep, 10 feet high (unfinished ceiling). I'll be using a 130" Seymour AT curved screen 2:37. I already have 4 15" Ultimax sealed subs which I was planning on placing in the front and rear corners. Will adding I.B. subs help produce more lifelike bass for HT. I prefer loud action movies and like to feel the boom. I don't really want to use up more floor space with box subs. I thought about adding 4 15" IB Ie. http://www.parts-express.com/dayton-...oofer--295-455 or similar behind my AT screen around 4 feet off the ground. I was wondering if that would help bring bass notes higher off the ground. I already have 4 at ground level. I am hoping to get full dispersion of bass from floor to ceiling. I could also place IB at the sides or rear of my theater and in the ceiling (since it is unfinished). But, I would only add a few at a time due to cost. I would prefer to find the best location now and add more if I feel its necessary. The cost being an issue ie. 2 Dayton IB are $99 each + an Inuke 1000dsp to power both = $400. 2 Ultimax W/ box and 2 inukes = over $900.
Will the IB be worth the addition to assist with my HT
p.s. I am not opposed to using 2 18's for IB or even larger if the return is worth it. If 2 18's are better than 4 15's then of course the 18's are the better choice and cost less.

[BobEllis]

I am a relatively new to the cult of the infinitely baffled, but I absolutely love my year old IB sub setup. I replaced box subs to reclaim the space, hoping I liked it. If you can configure your IB with a system Q of .5 (usually with EQ), it's great. I'm able to go a bit lower than my ported/EQed system did and everything down low is cleaner. It seems more benefit to music than movies, as a wannabe bass player I love the clarity of various bass sources.

If your Ultimax subs don't reach as low as your favorite source discs, IB may help if EQ'd properly. If you are looking for chest thumping bass, that's more in the 60-120Hz range, and mains with bigger woofers may be they way that you want to go. To find movies with deep bass content check out http://data-bass.ipbhost.com/index.p...mes-music-etc/

For low frequencies there is no replacement for displacement, given comparably low distortion. This is particularly an issue without the assistance of a port (sealed, IB). Multiply Sd by Xmax and compare swept volume per dollar. I have a couple of DIY Cable 15" drivers in an IB with significantly more displacement capability than the boxed JBL 2245Hs they replaced. An 18" isn't always better than a 15".

If raising your subs creates a sense that the bass is coming from higher that's a sign of distortion or a crossover that is too high/shallow. At subwoofer frequencies we have a hard time localizing the source. If you have an adjustable crossover in your processor, set it as low as your mains can handle to prevent sub localization.

In your room, I'd think that 4 x 15" IB subs would be adequate, especially augmented with your existing subs. Of course, more drivers makes for more headroom and you can go louder without distortion. Bass Head Bob says you can never have too many subwoofers. A benefit of your proposed side wall subs is minimizing the nulls in response. See http://www.harman.com/EN-US/OurCompa...s/multsubs.pdf You may want to consider placing 2 of the first four subs on the side walls and adding more up front if needed.

Enjoy your build.

[JonMarsh]

As long as your sealed subs are on a boundary, preferably two (floor + rear wall junction) they should be able to work fairly optimally. You haven't mentioned what size your sealed subs are and what the box Fb is- did you model them before building? If on the smaller side, it's not unlikely that they will need some EQ to perform flat in room. Best way to know is to do some basic measurements, of course.

An IB and sealed sub work basically the same, BUT, an IB allows the free air resonance and T/S parameters to set the LF roll off characteristic, whereas for a box sub, the driver and box design due this in combination. BOTH may require some equalization for optimum flatness, it all depends on the driver characteristic as to what is needed and how the bass-ic system will work... (pun intended). In general, IF you have the room set setup an IB with manifold, that's a good way to go because you wind up with even better damped transient response, and you don't have the power loss associated with the EQ from a Linkwitz transform or similar EQ to drive a sub in a smallish box.

Suggest you run the numbers in Unibox (free program for Excel) or similar to see what the theoretical anechoic response of your sealed subs look like now, then evaluate what you might need to do EQ wise if you want to target flat to 20 in room. Getting an inexpensive measurement setup might be very helpful for sorting things out, too.

[kevinm]

But Jon, why measure to 20hz flat when you can measure to 7hz flat? :W

Nothing of real value to add that these fine gentlemen haven't already said other than some less-than-subtle sarcasm, BUT just wanted to throw this out there.

I doubt you'll be timid considering the 4 ultimax subs already in your possession, but IB works best in large configurations (4+). As already been said, this works best because you provide ample headroom, increase overall sensitivity and reduce distortion. Additionally, if your system can play 130db, but you only want 125db, you have 5db worth of flattening to work with when you EQ. As you know, it's best to EQ down and not up. So if you go IB (adding more subs to an already over-kill system is a no-brainer!), I highly recommend using 4 or more of them.

[5th element]

The maximum SPL capability of a sealed or IB based system is determined by the raw displacement available and raw displacement only. A sealed or IB system will have exactly the same max SPL capability, if using the same drivers, providing the sealed system is placed, as Jon says, in corners.

In fact I don't know how boundary reinforcement works with an IB. Does it just give you the flat out maximum all the time, or is it actually less than a sealed box when it's next to three surfaces?

Either way, if the drivers are the same the theoretical SPL max is the same. What actually determines the real world max SPL is what EQ is required to get both flat, whether you have the amplifier power to do this and then whether or not the drivers can cope with it.

[crytklmass]

I forgot to mention the 15" ultimax came with the flatpack. http://www.parts-express.com/dayton-...kage--300-7097
I didn't want to take the time to build 4 boxes on top of building 2 more QSC 2150's and my theater. I was considering placing 2 subs to the sides just a bit forward of my searing area and 2 behind. Could I then use 4 I.B. in front (behind my screen) or is it better to build 2 more box subs behind my screen? I figured the I.B. would cost less since there is no box required and I could run all 4 with a single Inuke 1000dsp. If the I.B. is the better choice could I run them in a line array? (2 on each side of my center speaker. Located about 4 feet apart with 2 about 2 feet of the ground and 2 4ft off the ground) The dimensions can change. Or is it best to run dual opposed with 2 facing each other on either side of my center or 4 opposed in a single box? Sorry for so many ? but I have seen different build with different configurations. Can you build I.B. however you want as long as they are facing forward? A box speaker is straight forward.

[kevinm]

As far as I understand it, orientiation of the drivers in IB has less effect on output and more effect on vibration/resonances. Arrays have pretty rough vibration problems since all the drivers are moving in the same direction. I think this type of orientation is your best bet in IB design from what I have read - admittedly limited still - because all the drivers cancel each other's movement out.



Edit - How much space do you have to work with for the IB drives to use? They each need roughly the driver's vas x 10. If Acquiring that much space is troublesome, more sealed boxes might be a better option. As you move away from x10 vas you move more towards a conventional sealed setup. Dual opposed sealed subs might be a better option if you have issues with space.

[5th element]

An IB speaker is a sealed box, it's just a very large sealed box. All you're gaining by plopping the speakers into the volume of an unused adjacent room is efficiency vs a normal sized sealed enclosure. Even if the size of the adjacent room is pretty small, it's still going to be cavernous compared to an in room box, so you're still going to be gaining efficiency.

How do IBs work vs room modes? I'd imagine that they work just like a standard box loudspeaker does. So from that point of view, the efficiency gains aside, you're still going to get better bass with multiple subs placed about the room.

[crytklmass]

I can be build column type speaker stands for my side speakers. Would it help if I used 10" or 12" I.B. subs in a dual opposed configuration leaving the front open of course and covering with AT material? (the open baffle would have to face the seats) I could build 2 or 4 per side (4 or 8 total) to help with bass in the middle for the theater. I could stack my box 15's on top of each other too. I just built a sub floor to help transfer more bass, the concrete was killing me. I can still make adjustments as I build. As far as behind the seats it doesn't really matter. I have about 4 feet between the seat and wall for subs.

[5th element]

It depends what you mean by dual opposed. That by definition means placing one driver on the front of a cabinet and one on the back, so that the drivers are firing in opposition to one another. The benefit is that it cancels out the motion, caused by the drivers, that would otherwise shake the cabinet. This isn't really applicable to an IB installation if the drivers are mounted on a wall. If however they are mounted in a vent or duct, like kevinm posted then yes, putting one driver on one side of the vent and one on the other would stop the drivers from shaking the vent about.

If however you are talking about push-pull mounting, where one driver is mounted with the magnet facing outwards, with the other facing inwards, then yes, it is always worth doing this for subs. It's worth doing both for subs, but you can't exactly go dual opposed if the drivers are mounted on a wall.

[crytklmass]

Not a push/pull for the wall. I could use all 4 I.B. speakers like the picture above and mount them on the side of my theater wall correct? I have 22 feet of wall to work with. The other end would vent into my basement on the other side of my wall. Would it matter if I used 2 ib's at one end and the other 2 ib's at the other or is it mute with I.B. subwoofers. I would have to cut 2 separate holes but in the end I assume the displacement would be the same.

[5th element]

If you have two at one end and two at the other this will give you two low frequency sources, which is always better than one (Multiple subs). If you can go push/pull in the wall it will improve low end distortion, but may not be visually acceptable.

Although low bass isn't supposed to be directional, do be wary of the fact that with all the subs on one side of the room you might notice the bass is kinda balanced to one side, especially if you are positioned close to any of the drivers.

[crytklmass]

If I use I.B. subs in the side walls I may place 2 subs up front, not sure about the other 2 in the rear. Maybe its better if I place one sub on top of another and place all 4 up front. If Im going to do that, Ill have to decide before I put my screen in place. I don't want to be messing around moving things in/out. When placing the I.B. subs in the walls will it matter how far off the ground they are. Should I mount them toward the floor, middle, or ceiling. Will it even matter? I have 2 choices, either mount them inside my columns ill build for my side speakers (just for aesthetics) or I can hang my side speakers from the wall and cut an opening in the wall for the I.B. subwoofers. Does the hole size matter? would a 20x20 square work for a pair of 15"?

[kevinm]

5th is definitely sending you down the right path. Here is an excerpt from a great IB resource on placement.

[URL]https://web.archive.org/web/20130602192111/http://ibsubwoofers.com//URL]

5) Where should I put my IB?

Due to the design most people don't have the luxury of choosing between multiple placement options. If possible, placement should be on the front wall, floor, or ceiling, centered between the main speakers. This allows the greatest flexibility of crossover points, and that guarantees the sub won't smear the stereo image. Frontal side locations work well too. Locations behind or beside the listener are not recommended (see Administrative for more info about IBs behind the listening position). The more off axis compared to the main speaker, the lower the crossover point should be.

Those with the flexibility to do mount multiple drivers on the front/rear walls might consider doing a the IB version of a Single or Double Bass Array

So I'm thinking 2 sets of IB subs up front and then use the sealed Ultimax's wherever sounds best after some toying around?

For sets of 2, this is an easy design to work with if you want the boxes in another room.

Image not available

[crytklmass]

That's what I was picturing. So it doesn't matter how "wide" I make the hole? Wouldn't it be beneficial to at least reach the studs or would that cause resonance through the studs and into the wall? So by placing a few inches narrower you avoid that problem.

[kevinm]

#15 on the link I provided goes deeper into this, but it looks like the bigger the better. I would just use the stud width.

[JonMarsh]

5th is definitely sending you down the right path. Here is an excerpt from a great IB resource on placement.

https://web.archive.org/web/20130602192111/http://ibsubwoofers.com/

5) Where should I put my IB?

Due to the design most people don't have the luxury of choosing between multiple placement options. If possible, placement should be on the front wall, floor, or ceiling, centered between the main speakers. This allows the greatest flexibility of crossover points, and that guarantees the sub won't smear the stereo image. Frontal side locations work well too. Locations behind or beside the listener are not recommended (see Administrative for more info about IBs behind the listening position). The more off axis compared to the main speaker, the lower the crossover point should be.

Those with the flexibility to do mount multiple drivers on the front/rear walls might consider doing a the IB version of a Single or Double Bass Array

So I'm thinking 2 sets of IB subs up front and then use the sealed Ultimax's wherever sounds best after some toying around?

For sets of 2, this is an easy design to work with if you want the boxes in another room.

Image not available

Something to remember about a manifold configuration like this that is a bit narrower- it tends to put a peak into the upper bass, which may disturb the functioning of the crossover behavior and phase depending on the frequency setting.

Also, though longer manifolds with multiple drivers along the length are cool to build, there are also time delay effects which create some ripple in the response at some higher frequencies- we've measured both of these phenomena in Thomas's two manifold IB's.

Net recommendation, if you use a manifold, keep the mouth area reasonably large, and use fewer larger drivers. More ideal is not to use a manifold at all, flush mounting the driver to the wall, but for some that may not be practical.

[5th element]

If you are using a manifold you can still go push-pull, you simply mount one driver the other way around so that its magnet sticks inwards. Of course the manifold needs to be large enough to accommodate this, but from what's been said here that's going to give you bonuses in other areas too.

I guess the peak you're talking about Jon is similar to the peak you get in a standard H baffle, dictated by the depth of the H.

In a multiple sub set up one of the accepted ways to do this is by having one main large sub and then a couple of fillers. In a sense, having the main sub as an IB installation and then augmented with a couple of in room subs sounds pretty much perfect.

[crytklmass]

I was reading the spec's between the Daytons and AE. Of course there is the price difference but I wonder how much of a difference I would really notice between the 2. Even the Dayton Ulitmax is a cheaper 15" driver than other manufacturers but it still gets the job done. But $99.00 per 15" driver is really cheap. Maybe I can find a build thread and review from someone that has actually used this driver. I am not overly impressed with the Ultimax subs. Even with an Inuke 1000 dsp I cannot get the woofer to move, I can hear bass but no visible excursion. *sigh*

[ThomasW]

Although we try to use products from PE there are times when they simply don't offer what's needed. One example of this is situation their lack of drivers suitable for high output for IB subs.

Normal recommendation for a high output IB install is to start with a 4 Fi IB3 18"s. After testing the room for appropriate locations, build 2 manifolds large enough to accommodate 4 drivers but only mount 2 drivers in each. (obviously closing off the extra holes).

Fire up the system, do some measurements and give it a listen. If it's what you want fine, if more output is desired buy more drivers and fill the manifolds.

Without measurements it's impossible to know what's up with your existing subs. I suspect it's a combination of location, smallish box, and a lack of power.

[PMazz]

Hi Tom!! Good to see you posting. :-y

[kgveteran]

.......i want 32 of these http://www.parts-express.com/dayton-...oofer--295-455....... in a troth ib cutting across the front stage area of my HT...... Just say'n

[JonMarsh]

.......i want 32 of these http://www.parts-express.com/dayton-...oofer--295-455....... in a troth ib cutting across the front stage area of my HT...... Just say'n

well, I can't argue with the on paper value proposition of price versus specs; Fs and Qts are in the right ball park, and Xmax looks OK on paper,





but looking at the suspension of that driver, I'd say it would have a lot of trouble supporting 14mm Xmax with any decent suspension linearity- I'd go out on a limb a bit and bet a nice dinner anywhere in the SF Bay area that the Kippel report on this driver would be something of a mess, because of that.

the UMC 15 might not be as much of a "bargain", but I think it will come close to delivering as promised- I'm building a test case sealed for GF's HT to evaluate. If it works out well, will probably build another matching one.




And if you build a Troth IB with 32 (or even 16!) of these, I'd love to fly out and hear it! :W

[5th element]

The ultimax sure are pretty looking, we cannot get them this side of the pond that easily though I don't think.

I understand the suspicions about the suspensions limitation in those other drivers, but surely, if you had 32 of them you'd probably never exceed 1mm before the roof fell down. I mean I'm running just 4 10" XLS drivers in what amounts to around 15 litres of volume each and that rattles the room. Sure it's a small room, but 32! 15" drivers. Whaddya actually need all that for?

I mean I see this quite often though, people who do IB installations use far more driver than you'd actually ever put into the room in cabinets. Is this because you can? ie you don't need a box, so you're free to pick the biggest drivers you can afford and screw how big the cabinet might otherwise be?

Thomas' recommendation towards 4 18" drivers with 30mm of xmax seems a tad over kill for most people too. Or is this coming from the point of view of IBs aren't for 'most people' if you get what I mean. :W

[kevinm]

The more drivers you have the lower frequencies you can play with. I mean, don't we all really want to feel the 3hz LFE on War of the Worlds?

No one needs it, but when has that ever stopped us in this hobby?! :P

[kgveteran]

(16) Fi ib318's is my goal. Removable floor pods, 4 drivers in each of the four pods. Four Ep4000's would power them and my trusty Marchand BASSIS would do the L/T work....

Sorry to derail.....

[5th element]

It just surprises me that for a recommendation people talk about things that will bring the roof down. Surely if one only wants to experiment it'd be a far better idea to use a decent quad of 10 or 12" drivers. Or, if you already use subs, to use the same number of the same sized drivers so you can get a fair comparison as to what IB can do.

If you suddenly go from dual 10" subs to four 18" in an IB it's obvious which you're going to prefer

[kgveteran]

It just surprises me that for a recommendation people talk about things that will bring the roof down. Surely if one only wants to experiment it'd be a far better idea to use a decent quad of 10 or 12" drivers. Or, if you already use subs, to use the same number of the same sized drivers so you can get a fair comparison as to what IB can do.

If you suddenly go from dual 10" subs to four 18" in an IB it's obvious which you're going to prefer

I remember the first time i fired up my quad 15" Tumults sealed with about 6kwatts...... I never knew what undistorted sound, sounded like. Then i heard a buddies ib..... It sounded like a cleaner sealed system....

[JonMarsh]

T

Thomas' recommendation towards 4 18" drivers with 30mm of xmax seems a tad over kill for most people too. Or is this coming from the point of view of IBs aren't for 'most people' if you get what I mean. :W

I think that pretty much nails it. I bet I could walk down the block on the street GF lives in Danville, and not find a single home with an IB sub... :B

Of course, you never know, they could be thinking the same thing...

This neighborhood is what you might call a high end blue collar neighborhood- guys who run contracting outfits or other small companies, driving expensive pickup trucks (no, that's not an oxymoron, you know...) and living in $800K to 1KK homes. This is the slums of Danville. The nicer parts of town are filled with BMW's, Mercedes, Jaguars, Land Rovers, and for the more technologically liberal, Tesla's. It's rare I can drive the short distance from GF's home to free way entry and not see one or two Tesla's. But, IB subs are not likely on their mind, or even their radar!

[kevinm]

Ahh come on 5th, no one is telling him put 16-32 drivers in. Hehe

Just because you buy/build them, doesn't mean you are going to destroy the house. You know more than anyone that more drivers just improve response with cleaner, deeper response. That's half the benefit of IB manifolds (other half is utilizing the space for the driver's 10x vas). I think Thomas' recommendation is really solid. Buy 4 to get started and see how you like it.

[ThomasW]

Thomas' recommendation towards 4 18" drivers with 30mm of xmax seems a tad over kill for most people too. Or is this coming from the point of view of IBs aren't for 'most people' if you get what I mean. :W

I recommended 4-18"s to the OP because his primary speakers are QSC 2150


Unless he has the 4-18" there will be a huge mismatch in output between his mains and the sub.

For more normal HT's the standard recommendation is a pair of 18"s. With IB subs we have drivers that are excursion limited as opposed to thermal limited in a 'box' sub.

FWIW in the UK Fi drivers are available from Blade Ice.

[5th element]

Crikey that's a pretty serious main loudspeaker :E

I see what you mean about the need for more output. With the 4 15" Ultimax they've got that should be a good starting place, but indeed, if they wanted more, 4 18s would be the way to go.

4 18s in a well placed manifold or two + 4 15" filler subs about the room, to smooth out room modes. Should be a good test to see if your house has any subsidence throughout its foundations. Either that or it'll cause it :roll:

[cjd]

Pondering the potential loss of a room I can use an IB in has me thinking once again. I lucked out on our current house in this regard, but it's certainly harder to find a room where this is easily done - AND have everything else you want.

I'm surprised to see the recommendation to flush-mount when possible (vs manifold) - the mechanical cancellation seems like it's more beneficial than any time alignment or cavity resonance issues (assuming you're in a fairly open manifold - mine is 15x30 or so opening with 4 15's - I can sit in the 'box' reasonably comfortably) - I still cause the walls to wobble - I have no idea what I'd have to do to keep 4 15's from shaking that wall to pieces (and my screen, which is mounted on the same wall...) if it weren't manifold mounted.

You can never have too much excursion IMO. You may never use it all, but that first bit is the best. Kind-of like the 1kW (at 4ohm) monoblocks I use that rarely even see 1W output.

I talked with Rory a bit about the Ultimax - pretty sure it is likely to live up to expectations.

C