Hello All. I'm new here and I'm pondering the IB sub thing. From reading the faq's, I glean that a rear wall installation is the least desirable. Thing is, that's really the only practical spot I have. My listening room is 12'w x 21.5' l x 7.5' h. The rear wall seperates the room from a crawl space, (side split design house). Just wondering if anyone has installed IB's in a rear wall and what the outcome is/was. I am a 2 channel guy so 10 hz is not necessary but 25 hz or so would be cool. Thinking of 2 Dayton IB385-8's and a 350watt plate amp. I'd hate to spend the money on the hardware for a failed experiment.
Unfortunately not. The door into the room is at the rear side wall and you would walk into the speaker when entering the room. Another possible location would be on the side wall, (the other side of the laundry/furnace room), but this would take signifigant negotiating with the wife. If I were to use the laundry room as the infinite space this would put the sub drivers on the left side of the main speaks about 5' in front of them. Basically the subs would be between the listening position and the mains on the left wall. Better?
So, after my pair of IB385-8 were doing break-in duty on the garage system for a week, I decided to do a simple test install in my listening room. There are 2- 41 1/2" x 16 1/2" doors @ the back of the room leading to the crawl space, so I just removed one and built a baffle the same size, mounted the 2 drivers, built a little frame to screw the baffle to, hooked 'em to a 350W plate amp and voila subwoofer! At first, it was terrible- had to turn the plate amp way up, it didn't blend with the mains and the bass was coming from behind me. I check the phase switch on the amp and it's @ 180*. Switched it to 0 and turn the volume WAY down and it's a thing of beauty! The volume control on the plate amp is only @ 9:30 and it blends really well. You absolutely cannot tell that the bass drivers are behind you. This is where they are staying. Oh, and the way that they integrate with the mains is amazing. Really nice punch and much lower than before. As an added bonus it does not disturb the living/dinning/kitchen area above the crawl space. These infinite baffle drivers are keepers!
Sorry to revive such an old thread, but it is pertinent to my question. How many people have been happy with IB placement to the rear of the listening position and what crossover point did you use? The only spot with access to attic space is on my right wall at the ceiling about 1' behind the listening position.
Post by moonstone2 on May 19, 2009 23:12:54 GMT -7
I made some testing about this, how low in freq you haveto go before the bass disapears. And to my surprise i couldnt locate any of the bass drivers below 100hz, now i had a friend move it while i was outside the room so it was more or less a "blind test". It was just for fun but for my ears below 100hz its impossible to say where the sub was loated at aprox 90db. Now if i was to use a 12db lowpass the situation would differ, we used signals of 20,30,40,50,60,70 and so on. when you play music and cross with 12db at 100hz you still play pretty loud at 120hz. So 80hz and below is proberbly where the highest crossover is in my case.
My first thought was that LF sinewaves (with their very long wavelengths relative to the room dimensions) would be harder to locate than musical signals. Film and music always contain more bass source location information within the sound field. Then I realised that musical signals would contain many more harmonics. So the speakers would have even less of a problem steering the apparent source of the bass wherever was desired. This is born out in practice by my IB in the side wall on the same plane as the front speakers. Unfortunately my attic room makes it impossible for me to do any experiments with rear subwoofer positions using my old SVS as a bass source.
Perhaps those who ignored the usual advice and placed their subs behind them would like to add their own experiences to this thread for future reference. It would be a great shame if we were automatically denying people the right to enjoy IB bass just because they cannot place their sub at the front. We need more real world experiences of rear IB subs so we can offer competent advice on this subject in the future. It is a question which crops up regularly on other forums concerning box subs. A number of owners with rear subs seem quite happy with the arrangement. I imagine a rear IB is even harder to locate due to the lack of heavy distortion. Most of the upper harmonics in the audio signal would be played by the speakers rather than the IB.
I would certainly appreciate people with rear IB's to comment (or even people with less than ideal setups). I gave up on the idea of doing an IB sub in my current house since the only placement option was in the rear and slightly to the left of the main listening position.
I think that, in the end, 'ideal' is a relative term. If a rear IB sub configuration is better (and much, much cheaper) than a pair of sealed subs in the front do I care if it isn't 'ideal?' Since I haven't experienced an IB sub in person would I even know if it was 'ideal' or not? If it sounds better to me then I win. This thread has certainly given me renewed vigor for the idea of an IB sub. Thanks. dave
Before I found this place, and became "enlightened", conventional wisdom from my limited sources, was that low frequency bass was not locatable
My previous sub, (not IB) was located at the rear of my lounge room, and sounded fine to my, at the time, uneducated ears.
If a rear location is all you have, it is still better than no sub, in my book As a side note, I have rearranged my room again, for about the third time now , and now have a slightly different slant on IB location I obviously cannot move my IB at this point (well not without some effort with a wrecking ball ;D), but I can move my listening position, and that is exactly what I have done to fine tune things. Good luck with your choices, and count on support from others here.
I was going to buy another DIY sealed box sub but it seems that the price has gone up dramatically. For ~$100 more I can get myself a couple of Fi 18's and an EP2500. I think I will give it a try.
My questions... Obviously the box I build has to be big enough for the subs . How big does the opening to the room need to be to get maximum effect? In other words can the opening to the room be 6"x20" or 8"x20" (assuming the subs need 20"x20" to mount properly)? This is for WAF.
Right now I wouldn't be able to get any EQ but my preamp is equipped with Audyssey. Is there a chance it is good enough to detect phase differences and set them properly since the IB will be behind me? dave
How big does the opening to the room need to be to get maximum effect?
Check #15 on the main FAQ page
Right now I wouldn't be able to get any EQ but my preamp is equipped with Audyssey. Is there a chance it is good enough to detect phase differences and set them properly since the IB will be behind me?
I don't know much about the Audyssey but I don't think it does much with regard to phase.
Ok, why not comment on this old thread, since input was requested much earlier on!
I did my first IB, using stuff from the closet (an 18 and a couple of 10's), in a door to a storage space in a rear corner of the room.
Then I turned off my three expensive boxes, EQed the makeship IB with Velodyne, and fiddled some with phase, AND got the best sound from my front end ever (so long 'smearing', hello clearly defined imaging and soundstage), and with never before achieved extension in the bass.
Most 'experts' (including those at THX) state that bass is not localizable, and that if you have two subwoofers, put one in front and one in back. This site has a theoretical argument against a single rear subwoofer (WHAT ABOUT ONE FRONT, AND ONE REAR IB?), but has anyone actually reported hearing the predicted smearing of imaging when they tried the rear only position?
I haven't seen this confirmation posted, but have seen, like this one, contrary views.
I feel that what mattered for me was getting the boxes out of the room. When I turned my front location subwoofer (the site recommended acoustic suspension) on, to accompany the rear IB, I got the same old 'smear' from the front end (left, right and two centers).
6/14 EDIT: I stood in front of my IB last night so that it was 1ft behind me and I think I felt what ThomasW was talking about. Crossed over at 60hz, and its not that I could hear it behind me but felt like I could perceive it behind me. Maybe whats distracting about a single rear sub is that tactile sensations feel backwards.
Last Edit: Jun 14, 2012 8:03:12 GMT -7 by scorp133
Do you mean instead of straight back from one's head, the IB is at a angle much closer to perhaps 70 degrees up? Good question, and again, as has been stated, not enough good information.
Theoretically, localization is a function of frequency, distortion products, etc.
I've performed my own small box experiments with subs behind me, near-field, on each side of me, etc. I found I can enjoy the effect only if there's some measure of symmetry , with subs equidistant of my position, and back of me a few feet. Otherwise I could detect they were behind me and either side of me. I utilized an 80hz cross, and Velodyne subs.
This is a good question, and the answer is that it's not advisable, and for good reason. But still more evidence is needed. Now in a case of multiple sub scenarios, with the proper tools for time/signal alignment, sources behind the LP in concert with sources in front of the LP can offer world class playback.
OK, I have 2 IB set ups in my house. In the HT system I have a pair of 18's, one at each side wall about halfway between the seating position and the screen. these drivers are mounted horizontally and vent into that room through some modified floor air vents I got at Home depot on clseout. The system works great, lots of extension, lots of output, about the only problem is having to secure and mass load items in the room to keep them from rattling.
My second set up is more relevant to this thread. This is a dedicated 2 channel setup. Most of my listening room is over a finished basement and I'm not willing to cut holes in the ceiling of the basement to have my subs vent into the listening room at the front wall, plus there would be a more direct acoustic path for the back wave, up the stairs, down the hall, back to the listening room. So for that system, the setup ended being a pair of v-shaped manifolds (1 had to be V shaped to miss the air handler, so of course, both had to be) in the crawl space venting into the listening room through large cold air return grates at the back corners of the room. The main speakers are a pair of Martin Logan CLS II Z electrostats located about 7 feet out from the front wall.
The listening position is a couple feet out from the back wall with much room treatment lining the back wall. The sub drivers are 4 of the Fi car IB 18's, 2 per manifold. The main speakers are run from 95 HZ up, sub's from 95 HZ down, both crossed over at 60 db/octave. It works pretty well, with program material, there is almost never a sense of bass directivity, it just sounds like the bass is coming from the front since that's where most of the sound is coming from. If I turn off the mains amplifier, there is a sense of the LF sound coming from the sides and a bit behind, but its a room filling sound and with the fast slopes of the crossovers, the music cannot be identified.
when I originally posted some information about wanting to do this one moderator said why not just move your listening position. There are three glass panels on the front wall that give a beautiful view of the wooded back acreage, and even though I'm into audio pretty heavily, being able to look outside while listening to music is more important to me than having my sub vents at the front of the room.
I don't feel it was much of a compromise, I've enjoyed it for a number of years and it can be relatively easily undone if I was ever wanting to sell the house to a non audiophile. I think the most important thing to do is use very fast crossover slopes for the subs which eliminates most of the overtones and with it, the ability to identify where the sound is coming from.
Hope this helps anyone thinking of a similar setup.