Hide my babies?!?

[ajpoe]

So, it has been a while since I've posted on here although I like to check in and read up on new projects, etc. This was my project from what I can't believe was 8 years ago!

http://www.htguide.com/forum/showthread.php4?t=14644

Not much has changed with my system since building these subs. I'm yet to hear anything that sounds better and have a list of friends who want to purchase them if I ever decided to give them up. Anyway, life changes and I'm looking for some feedback. I thought this would be the best place to come since it would be a DIY undertaking. We recently listed our house and in the process the wifey had me take one of my subs to the basement. So what did I do... well, I ran one sub off my Crown K1 in mono bridged mode and was still blown away by the sound I was getting from just one of these subs. Here is the challenge! We are building a new house and as tolerant as my wife has been with having my Studio 60s, center channel and two subs across the room, she doesn't seem as willing to allow this in the 'dream house' that will be breaking ground soon. We are trying to compromise here and I have come up with the attached idea. Sorry for the rough sketch but it gets the general idea across. We have been distressing/refinishing a lot of furniture for our house so I have more wood working experience since I built these subs. I even built our distressed dining room table. So, I was thinking that I could find a piece of furniture that fit our style and I could basically just use the front and top and rebuild the back to house my subs/components. The thinking is that I could hide a sub at one end or subs on each end. I would probably just finish the sides with grill cloth to hide the speaker. She would prefer that I do something similar in the front to hide the center channel. So, if I were to do something like this, would I be creating any major issues with sound quality from the subs? I fear that having subs facing sideways in opposite directions may have not be so great but maybe I'm wrong? Also, after hearing one sub bridged off the K1, maybe I could get away with only one sub and just put it within one end? This is going to be a substantially larger room though so that does scare me a bit. My wife has agreed that I could continue to use the subs if I were able to hide them in some manner like I drew up. Any help to actually accomplish this would be much appreciated. We have just moved to a temporary living spot while we start the build process so this is the first I'm really getting the chance to breathe and think about how to do this in the new house.

For those of you who want to suggest the simple idea of just having a dedicated room, I've already thought of that. It would have to be in a basement. In the previous house, I temporarily moved my system to our basement as to have a normal 'living room' and we found ourselves never going downstairs to use the equipment. My wife and I agree that we want the best sound in our main living space so we can utilize it daily easily as well as for entertaining. We just need to agree on how it will look.

Thanks in advance for any input!

[BobEllis]

Is there and adjacent basement or attic in the new room? How about about a large closet that could house an infinite baffle sub?

Sub frequencies are so low that which direction they face is immaterial. Sideways firing is fine and might help hide any higher order distortion products. Your sketch indicates there is some vibration isolation between the subs and the rest of the table. That's a good idea. The usual caveats about enough airflow to keep your amps cool apply. Depending on how much space is available you may need to consider adding fans in the space to encourage airflow. Do whatever it takes to get your subs in the room.

[ajpoe]

There is an unfinished basement below the living room. I never really thought of that option... If I were to do a piece of furniture then yes, the sub box would not touch it. I would build it to leave a bit of space around the box.

[ajpoe]

I do not know anything about an IB except for looking at pictures and trying to read through some of this: http://home.comcast.net/~infinitelybaffled/index.html

If I were to do something like this, would I still be able to use my two Avalanche subs? If so, would two 15"s be enough for a large two story living room? Taking my subs out of the existing boxes to build a new IB enclosure would be OK... assuming I could convince my wife to let me put a hole in the floor. But, if I had to buy all new drivers or more of them (which would require another amp too), I would probably rather pursue the original furniture idea.

Also, I understand that using one sub facing sideways is not a big deal for bass frequencies. But, if I were to use both at opposite ends of the furniture facing opposite directions, would I run into problems with cancellation or anything else? I guess I didn't have that issue when I was running them both together on opposite sides of each of my fronts... they were probably about 8' apart facing forward.

[BobEllis]

You've found the IB bible. You'd probably want to make a manifold/"enclosure" to hold your drivers below the floor and put a nice wrought iron grate over the opening. With the inside of the opening painted flat black, the opening shouldn't draw much attention to itself. There's not much to designing an IB sub beyond the electrical EQ required. The site you found shows a number of examples and ways to hide the sub. I like the no visible sub that kicks butt aspect. Place the manifold under the equipment table - leave the false drawer fronts and a grill on the sides, back open. Woo hoo!

As to whether the 2 drivers would be enough, as usual it depends on how low you are trying to go and how loud. If the subs are sealed now and are enough for the room, I think you'd be OK. If ported you'll lose the port output, but the driver won't roll off as quickly as it does in a box. Since there is no enclosure adding to the suspension stiffness, you would likely find that the subs are excursion limited. That would mean you don't need an extra amp. Just wire the drivers in series/parallel to keep the net impedance tolerable for the amp.

Since most good drivers have a Qtc too low for unequalized operation, you will likely want a bit of LF boost. One way to do that is to add a second order high pass filter with Fc= driver's Fs and Q so that filter Q x driver Q = .707 (Butterworth, flat deep response before rolloff) or .5 ("critically damped") If the driver Q is .4 and you want a Butterworth response, your filter Q should be 1.77. The benefit of the filter besides increasing low end response is it limits extreme LF excursion. You could make your manifold to hold 4 or more drivers, and put blanking plates over the unused spots unless you need to add more drivers. The filter is easy to design build, I can help you off line if you'd like. You can also use a Behringer FBQ2496 or similar.

Good luck convincing the wife. That's the hardest part of this hobby. My girlfriend says my .75 cubic foot mains are "huge" h:

[cjd]

fwiw The Khancenter was made for just about that kind of placement...

[ajpoe]

I have no idea what the Qtc measurement is on my drivers. They are Ascendant Audio Avalanches from mid 2005. I know they were quite popular back then so someone else may have the specs. I really appreciate the feedback. I had never even considered an IB option and I'm thinking that would be awesome if my wife would allow it. I'm also getting a strong suggestion to replace my Paradigm Studio lineup with an on wall alternative like the Monitor Audio Apex a40s for L R C and a10s for the surrounds. If I did go this route, the IB setup would make the room very clean! I have concerns of how much I'd be losing with the a40s compared to my Studio 60s but that is a whole different conversation. The two huge sub boxes are her main distaste!

[Steve Manning]

Of course you could offer up an alternative to your wife, just to make things smaller and neater just for "her". You could go with a pair of these, http://www.ultraaudio.com/twbas/twbas_20100301.htm good review on these ....... then you can finish things off with a pair of these http://www.jlaudio.com/iws-sys-2-hom...woofer-systems .... to replace those big old ones you have. Once she see's the price of the new toys all of a sudden the old stuff looks like a nice option after all!!!!

[ajpoe]

Steve, I must say I love you how think and will follow that up with the comment "great minds think alike!" Just this morning over breakfast I read my wife a review of the Paradigm Sub 2, showed a picture and asked her if she would prefer that I have that with the Signature S2 bookshelf speakers that took up a lot less room than the 60s. LOL!

She was not impressed with the price of the Sub 2 and didn't know why anyone would "need" that. I said "need" is an interesting word as we build a new house and discuss any high end HT setup. :-) I got the look and went on with my bacon and eggs! If only money was no issue I could probably get away with it!

[PMazz]

didn't know why anyone would "need" that.

I always invoke a reference to jewelry when my wife says that.

[Steve Manning]

I always invoke a reference to jewelry when my wife says that.

This is so true ....... you have to factor in the additional "appeasial" gift for the wife when purchasing one's toys.

[cjd]

I always invoke a reference to jewelry when my wife says that.

Fortunately for me (?) my wife knits...

And has more yarn than she could use in a few years, I suspect. None of it cheap. Last year she focused on "de-stashing" through knitting or selling, and ended up with only a little bit more yarn in the stash than the year started out with.

Whee.

She hasn't really ever complained about large speakers either, however.

[ajpoe]

So the best thing happened today! I preface this story with the fact that my wife and my wife's family are all extremely talented musicians. This fact with my wife has helped me get away with the system thus far because she really does enjoy the high end sound and we use it quite a bit for 2 channel listening. Anyway, we went to my in-laws house today for Easter. My father-in-law is the band director/music teacher at a prestigious school in the area. He has two masters in music. I told me wife to not say a word as I explained my side of the argument and I went on to explain the dilemma we are having with the compromise on the HT system to the family. I went on to show my father-in-law some IB setups with several pictures. He thought that was pure genius and said I should absolutely do that. He agreed that it would get the huge sub boxes out of the room and a little hole in the floor was nothing to hide with a nice grill or furniture over the top. My mother-in-law and grandma-in-law both chimed in with agreement and thought that was such a wonderful idea. So... I just looked at my wife and said last time i checked my math, 80% of the room feels like this is a great idea and these people agreeing with me are your elders that you should deeply respect! LOL, it was perfect.

Anyway, my father-in-law loved the idea so much he is considering doing the same thing in a rec room they are finishing upstairs. Although, he would have the ability to do it on the other side of a wall instead of through the floor boards. I just thought I would share because I got a huge kick out of it. I think this has pushed me significantly toward wanting to pursue the IB setup vs. building a piece of furniture around the existing subs. I think the elimination of the subs would also allow the Studio 60s to stay. I got them in the Rosewood finish so they are quite nice to look at anyway. Now, to continue researching IB setups!

[ajpoe]

More questions... after reading the IB bible in more detail, I'm concerned that the two 15"s won't be enough. It says that the output is typically less in an IB configuration than a sealed sub. I really do not want to reduce my bass output. I'm also concerned with the size of the hole I'd have to put in the floor. I have a buddy that is really hoping that I go the IB route. I think he is thinking he could snag my two sealed boxes off me and convince me to use four new drivers in an IB setup. But, the problem with that is that four drivers will require an even bigger hole than two. But, if I could make this work, I would be open to selling my subs to him and an IB setup seems like it would be quite a bit less expensive to do since I'd be building my own enclosure that doesn't have to look nice. I'm not sure what the latest and greatest drivers are these days but I'd like to look at pricing so any suggestions that I should look into, please let me know.

Also, to anyone who has read the reviews of the Paradigm Sub 2. Every review indicates that this is about the best sub they have ever heard for both music and HT. They tend to atribute that to the fact they are smaller drivers but more of them in the force cancelling arrangement. This gets the faster performance of the smaller driver but can move a lot of air because of the number of drivers. Would there be any benefit to trying to recreate this type of set up with an IB configuration. Maybe six 10" drivers like the Sub 2 instead of two or four 15" drivers? Thoughts? Would it be possible to get that same kind of low end reach?

[BobEllis]

I'm not a believer in "fast" bass. With a typical 4th order low pass filter at 80 Hz, how much "fast" signal can there be to hit the driver? I think the term is synonymous with "tight" bass, either referring to a close to critically damped system, Q=0.5. As long as the driver behaves linearly with a system Q approximately =.5 your will probably come close to nirvana. This means roll off will start higher but be more gradual than a higher Q system. The other advantage, is that less EQ is required than a higher Q system, so the system power requirement is less.

Empirically it doesn't make sense to me that output would be lower than a sealed enclosure. You still have the same surface area being displaced the same amount. Maximum output will still be the same. It's been a while since I have read the IB site, but I think you may be misreading the requirement for EQ at the bottom end and a potential requirement for more power as meaning lower output. A sealed box will have a higher cutoff frequency and tend to be self limiting for excursion. You are more likely to drive an IB sub to its excursion limits than a sealed sub if you aren't careful, so a high pass filter is a good idea, even if you determine that you don't need EQ.

Just in case, you can size your manifold to accommodate extra drivers if you need them. You can mix drivers as long as each type gets its own EQ/filter.

Is there a thick wall you could use to house the manifold rather than come through the floor? The opening(s) could be covered with a grille meant for AC returns. A fairly simple drywall patch if you sell or decide to go back to conventional subs (unlikely).

[ajpoe]

I am concerned about just two avalanches for the ib because of this from section seven of the link I posted:

" In a small room 2-15"s should be adequate. For larger spaces or for high output, multiple 12"s, 15"s or even 18"s* are desirable. People should understand the IB bass is much different than the bass from a standard 'box/tube' sub. Because of that, we recommend use of more drivers than one would normally associate with a 'normal' box sub. Please note, the primary function of using significantly more drivers is to maintain extremely low distortion and protect the drivers, not to create insanely high SPLs."

This will be a large room and two stories high. Unfortunately I do not have a room I could use except the unfinished basement...

[BobEllis]

I was thinking of having the wall built like it would be carrying a large HVAC duct riser, which is actually your manifold. That way you wouldn't have a hole in the floor if you ever want to sell.

To me that quoted paragraph would apply to all subs. The old no replacement for displacement argument. Most people cannot live with multiple boxed subwoofers competing for space in room, but more drivers would reduce excursion and therefore distortion. With an IB arrangement you can get away with more drivers.

IB subs are prone to infrasonic excursions as there isn't the box air spring to help limit it. One of the reasons for IB is the extra extension it offers compared to a box type with the same driver. Excursion rises with decreasing frequency, so trying to get to 15 Hz will push the driver to 4 times the 30 Hz excursion for the same SPL. If you limit the bottom end with high pass filter you will limit LF excursion below filter cutoff. I think you'll be OK if the sealed box version would work in the room and you limit the IB sub to the same cutoff. Of course, if you want to reproduce those 5 Hz helicopter rotor sounds in Blackhawk Down at the same SPL as your mains, you'll need more drivers. Lots more.

[Martyn]

With the help of Thomas and "The Cult", I built an IB arrangement much as you describe. I used a pair of Q18 drivers from Fi Car Audio mounted facing each other in a plywood manifold that I mounted beneath the floor of my living room adjacent to an outside wall. I used a 16" x 18" return air register to disguise the hole I cut in the floor. My wife remained remarkably calm during the whole exercise.

The Q18 drivers have a 27mm Xmax which I don't come close to using. I drive them with a Behringer EP1500 amp which I leave set at two o'clock (26 on a scale of 32). This is sufficient to scare my wife when we are playing a movie at typical cinema levels. This is in a room 19' x 23' with a nine foot ceiling. If your room is much bigger or you like effects that are a little more extreme, then I'd pay a little more and get the EP2500.

I love the overall effect. It's all crunch and no boom, often with little audible sound at all.

[cjd]

Of course, if you want to reproduce those 5 Hz helicopter rotor sounds in Blackhawk Down at the same SPL as your mains, you'll need more drivers. Lots more.

Once you discover what this is like, it's tough to go back. It needs EQ and gobs of excursion.

The flip side is that it is startlingly clean - it's just there, and gone. Which is the whole strength of IB subs in the first place.

I went from a pair of Dayton 15" IB subs to a quad of Tempest-X leaving me with over 4x the displacement. I used to bottom the IB subs, I have to try with these. My room is ~1600cu/ft and my usual movie volume is <80dB at the listening spot, though when it's just me it creeps up over 85dB. Sometimes more.

My main problem with the infrasonics is that it bothers the projector and the HDMI connection - I've had the projector lose sync due to sub-bass (confirmed it wasn't a disc problem by muting...) This has me wanting a LED based projector next.

If you limit to 18Hz ("traditional" sub-amp rumble filter) it is unlikely you'll have less capacity to fill the room with the same drivers, but the quality will (almost always- assuming good placement of the IB) be significantly better. It's only when you discover you can go lower without much effort that the need for more displacement starts to creep into your plans.

C

[ajpoe]

I think a 16"x18" grate in the floor would get SIGNIFICANT push back. I was trying to make an argument for a standard register size and I know that isn't large enough after doing more research. I'm not completely going away from the IB just yet but I'm wanting to talk more about the possibility of masking the subs in a piece of furniture. I have been throwing out ideas to the wifey of pieces of furniture that would work to hide the subs. One of these is a trunk... maybe something old school with cool hardware or whatever on it. I don't really care as long as she likes the looks of it. I could even build one from scratch and distress and have her finish it in her style if I had to. I'm thinking a force cancelling design. I found some info on in wall subs with small drivers. That is where I stole the attached image. If that were an top view of the innards of the trunk (or any other piece of furniture), would that work with my two 15" avalanches? I could maybe put the slot on the backside of the trunk or lift it with feet and have the slot on the bottom. I don't know the science of how big the slot would have to be and how close the drivers should be to avoid phase issues. But, I guess those are things that would be addressed if the general idea would work.