I NEED infrasound... (seeking advice for sub20hz bass on a budget!) - Page 8 - diyAudio
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Old 9th April 2013, 06:50 PM   #71
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Join Date: Sep 2011
Location: Germany, South, near Stuttgart
I also want a streetlegal PaganiZonda R, but no way. Not possible on public streets here in Germany and the bigger Problem, the 1.500.000Million Euro and the limited edition of 25 is already sold out!
What I suggested is able to play below 20 Hz with a significant Level and its inside the 5 K limitation!
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Old 4th May 2013, 05:00 AM   #72
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Join Date: Jun 2010
Hello again, I said i'd be back and I am! : D Sorry off so long, RL got busier than I thought. : P Following back up now though I still may have somewhat intermittent access. (if the thread goes cold a few weeks i'll post once back, RL work taking me out of town unexpectedly).

FYI I'm rereading the thread from the very beginning and taking notes along the way just to be sure I didn't miss anything offered so far.

To bring anyone else up to speed whose only reading the latest messages - I was originally seeking a 3-20hz capable at 115db room for special audio mastering (which i've now revised to 4-20hz at 120db ideal currently) not only LFE for cinema, but possibly for location based entertainment design (which is one reason for the "beyond THX" requirements - they have the money to spend to play louder and deeper for a crowd) but furthermore "on a budget" both financial and wattage. (no using 22x Bag End 18's and 40kw here) About half the time was spent so far saying no it's not a joke, no i'm not seeking injury, and yes i'm serious, and no the goal is not 160db at 30hz either like in a car. I just need to be able to author and demo true infrasound capability.

A few offers and suggestions have been made of different ways to accomplish that (which I was seeking, and thank you for all contributions so far, they are appreciated very much even those angles I may not end up using), and although I knew zero about Infinite Baffle designs at the beginning i've since learned more in the last month but still don't understand it fully in particular low frequency efficiency. So i'm still not 100% sold (i'm 75% there so far)/wanting to compare against a specially constructed horn subwoofer from concrete at least being possible, something like this: IL PIU' GRANDE SUBWOOFER DEL MONDO - by Roberto Delle Curti - Italy if anyone has suggestions. But i'm simultaneously sketching out an IB-centric plan.

--- (first responding to what a guy on a post I missed actually first time around!)

Going to respond a bit out of order, as i'm taking notes as I go and want to comment on the most important things first rather than the first information.

To "just a guy" WOW and thanks, for your modeling of the room - after seeing that, consider it guaranteed that i'll figure out a way to make an airtight room if that kind of room gain is possible. Since were talking a difference of so many kilowatts and extra woofers to get back the db otherwise - but that's why I asked in my original post that room design comes first. Questions I have are do BOTH sides have to be that airtight (both the 'home theater'/large room and the 'mastering'/small room) or just one side?

Note i'm seeking nowhere near the low end extension in the home theater room, just the mastering room - i'm pretty sure 4 to 8 18's will be ample bass for any home theater soundtrack. I don't know what the leakage is/might be i'm just curious if both have to be utterly airtight or just the mastering room/"speaker enclosure/IB backside" side. (shutting off the air vents to the mastering room during mastering periods of infrasound which in all likelihood cannot be listened to for more than a few minutes anyways isn't really a lack of oxygen risk or anything : P) I'd rather leave HVAC working for the home theater's multi hour movies or have an option to close it off for shorter periods for 'demo time' (plus more air in a large construction) for if I need the HT side to play the loudest and deepest.

The next thing i'm wondering is how much does sound absorbant material affect the efficiency? I'm hoping for fidelity over absolute ultimate db and efficiency at higher bass frequencies (others suggesting concrete walls by the sound of it) without too massively compromising 4-8hz response. I can have ultra-solid walls filled with steel and concrete but i'd like to have strawbales inside those walls to make it as quiet as an anechoic chamber in there so direct sources are almost exclusively the source of sound. (this is not a 100% plan to use strawbales/just something i'm still exploring) My understanding is such material primarily attenuates things half the wavelength or less, but the deep soft squishiness of it could also absorb lower frequency energy, i'm just not sure how much. (I don't 100% have to use strawbales either it's just an excellent value for whats an STC of 55-60. I could also use like 5 layers of sheetrock with green glue keeping the outer wall hard as long as 130db doesn't shred it. It will cost way more though i'd guess.)

Another question is how would having unequal room dimensions affect things? I've seen some designs that for instance the front of the room is 10ft wide the rear is 13ft wide, the front is 7ft tall the rear is 9ft tall, so that there is no "resonance" even essentially possible. Sound absorption is needed because acoustics are ruined all to hell otherwise with the odd reflections at higher frequencies, but the lower frequencies are tamed. If not possible I can go with a 'golden ratio' to try and even up the room modes and spread them around as much as feasible.

For room size (from "what a guy") that under 20hz room size doesn't matter so much anymore if it's airtight, i'm not sure I understand the physics of how this is possible... people wall off boom vans to pressurize a smaller place to hit a higher db afterall unless that's only the case at certain frequencies. If this is the case then the home theater might almost be the mastering room too. (a 2nd room is not essential, just seemed the best way to get the infrasound efficiently) Airtight and rigid is doable - i'd still like to have that ultra sound absorbing material (strawbales or whatever) if possible.

---- CAUGHT UP NOW - new things since my last fully read post.

Originally Posted by weltersys View Post
I question the use of the small room, as there are no large rooms or open air facilities that your LF mixes made in a small room will relate well to.
In an acoustically large room (most theaters) the level from the sub will drop off with distance.

A small room allows even pressure throughout at an SPL that would only be achievable for the front row in a theater, or at "ground zero" in a ride.

If you want to make "award winning" mixes, I'd suggest a mix facility that approximates the intended listening environment.
The small room was mostly a way to increase frequency response/db/efficiency - if what a guy is right and room size doesn't matter, given a very tight listening environment, the small room option may be abandoned entirely as nothing is 100% fixed yet. A home theater room is still not the size of a pro theater but whether tiny or medium i'm hoping by having something almost anechoic chamber quiet I can simply simulate with DSP a "large movie theater" hall mode, and then try the mix later in a real theater to see if it correlates well.

Not everything professionally is mixed in home theater sized rooms, not for music and not for cinema. One way or another infrasound is needed for location based entertainment system projects - I either do it on a budget or I don't do it at all. Telling me to get 22x Bag End subs and a 40x90ft mastering room wont help. Even if I can't do 100% of the mix, but can only do 90% of it, I can still make the mix, and demo it at home to someone flying in, and if funding support comes in fine tuning the mix can be done elsewhere/further tests done. I seriously doubt there would be fundamental or huge differences that would completely break the mix unless you have reasonable anecdotal evidence that small mastering rooms cant and dont work? :- /

Originally Posted by weltersys View Post
You can't "scale down" a 113 foot long 10Hz wave, and how it sounds in a theater will be far different than the experience in a small concrete bunker, both in terms of achievable SPL and acoustical response.
The biggest difference is that a normal theater will have less low end response and less db by what I can tell. Since I hope to have a very quiet room and DSP simulate the room modes of a large theater i'm not even sure there will be huge differences in damped but still there front/ceiling reflections or room reverb. (which may mean some extra room simulating DSP speakers like yamaha's Presence, who has been modeling rooms since the 1980's to try the mix through to see if any problems become apparent with a less damped real world theater room) The only reason I don't necessarily want commercial theater acoustics at home is that I don't ONLY want to master for that environment. If there's a vital flaw in this strategy though i'm all ears to hear from people who know better than me - just preferably from people who tell me a better way to do it instead of just telling me don't bother to do it at all.

Originally Posted by just a guy View Post
The wavelength of 5 hz is 226 feet, the half wave would be 113 feet. How many straw bales do you have? Do you have room for a 113 foot thick wall all the way around the perimeter of your room?
I'm not wanting to attenuate the lowest bass actually, just control room modes above the frequency where room gain kicks in. But I was worried that having thick strawbales might quiet the infrasound too much - some people were implying that might happen but I wasn't sure who said what or knows what. : P

Originally Posted by just a guy View Post
There is absolutely no need to cater to the 4 hz crowd
I'm not "catering to a crowd", Location Based Entertainment systems is cost no object IF what you come up with blows somebody away. At such low frequencies I probably wouldn't even ever use speaker cones, i'd probably use some kind of one note tuned resonator (like organ pipes). I don't want to use that indoors though regardless of efficiency because I don't for a fact know exactly what I WILL use... i'd plan to play around with samples of "credibly efficient infrasound generation methods" with the idea I could use any of them at no cost in the virtual mix, even if scaling it up to a crowd would require something that's... not a speaker anymore.

I might abandon 4hz or 5hz plans - they arent firm, i'm just exploring them. If a very tight solid room can allow me to master and explore that without radically increased cost beyond an 8hz suitable room i'd like to see what it's like. If it required 16 subwoofers of 18" size - I may do exactly that, designing capable to expand to that in the manifolds even if I start with just 4. If things just get entirely too radical I might tone back plans but with an original bass budget of $10k i'm still not sure where that is. If even 24 subs IB could never reach 120db at 4hz regardless of room construction/size, or electronics that work at that frequency become impossibly expensive to find that's about the point I start scaling back. (Yet I still bump it only as much as needed, ie designing for 5hz instead to see if that's possible on the budget)

Originally Posted by just a guy View Post
I don't really understand this. It would cost 10's of thousands of dollars to construct a large concrete under floor horn but your budget for the IB setup is for only four cheap 18's and a bit of wood to make a baffle (or manifold) - well under $1000. ???
Well using earthbag construction i'm pretty sure I can replicate the shape of IL PIU' GRANDE SUBWOOFER DEL MONDO - by Roberto Delle Curti - Italy just fine and then concrete over the front of it using pouring forms. But i'm thinking such a horn will still roll off rapidly below the 10hz it's designed for, it just starts to become an alternative if I start looking at dozens and dozens of subs as the alternative. My "budget" wasn't $1000, it was up to $10k, but I was exploring how to phase up to that budget over time since it wasn't all at once. I think my original post was about how close I could get to the ideal with $5k, and then with $2k. In favor of Infinite Baffle is how nicely expandable it is - I could make holes in the wall for manifolds expected to eventually be 32 subs and fill just 4 to start. The horn is kind of an all or nothing commitment, but the persons reported 120db at 1 watt efficiency made me --> @_@

Originally Posted by just a guy View Post
No, the airtight construction is far from unsolvable IF you are aware of the issue and plan ahead. But from your previous posts I had no indication that were aware of the issue OR that you wanted the type of construction that would afford these benefits.
I'm sorry if i'm frustrating you with some questions and hope I haven't driven you off the thread, when your suggestions have been the best of all so far/primarily the room gain modeling. I had no idea it was that important and now I do. But that's why i'm trying to solve these problems at the design stage. I'm realizing the biggest problem is still explaining both why i'm serious and why I don't think that i'm crazy to seek this. Not even an LBE rig would be producing 4hz with speaker cones. But it lets me both master up and demo simulations that I think will be close enough to justify larger mockups and experiments. I have to do 4hz with speaker cones because I don't want to build up every kind of infrasound generator possible when it's not only about sine waves.

I'm going to go ahead and post this, even if I double post to additional responses. It's getting large enough I don't want to lose the in progress writeup or anything.

As a quick PS - to those suggesting excel spreadsheets, WinISD, AkAbak and similar, I can't at this time use any software I don't yet have due a computer problem. (crashing on install) No that doesn't mean i'm asking you to do my work for me! : P If you volunteer to noodle around and model something up in addition i'm happy, but no i'm not expecting or demanding anything whatsoever when you've all been so helpful so far already. This is just a phase 1 pre-alpha stage of exploring different ways to solve these problems. When I actually hit phase 2 i'll have the computer working and start hammering out specifics - room size, room shape, using the software, deciding on appropriate speaker cone displacement, amp wattage, everything. I'm not asking anyone to do all that unpaid fine tuning work for me. This is still just the picking brains stage to see what kind of possibilities are worth designing around at all.
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Old 4th May 2013, 05:11 AM   #73
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22x Bag End 18's seem to fit for the duty
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Old 4th May 2013, 08:58 AM   #74
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Responses part 2.

Originally Posted by just a guy View Post
I know that, Don. The original mention of straw bales had to do with sound isolation outside the room.

Regardless, if used as bass traps the straw bales would need to be INSIDE the room and I'm pretty sure that's not what he's planning.
Actually they were planned to be inside the room all along because I thought it was necessary. I thought I was clearer on that point but if not we'll just call it my bad and move on. I said it would be possible to have 'hard' walls inside if it were required for infrasound performance however as an alternative.

I hoped the straw bales would kill reflections from at least 150hz up (at about 40 inch wavelengths, 10 inches wide of straw should be a quarter wave) or 75hz up if I doubled them, or even more of using the thicker/wider 3 string bales which are 24" wide laid normally. Below whatever frequency that blocked I was hoping to use unequal room dimensions, again if I can, to kill room modes. I was hoping that strawbales and unequal room dimensions (no parallel walls or ceiling/roof anywhere) would be irrelevant to infrabass efficiency! Ideally the strawbales wouldn't touch the wall/they'd make a rectangular room within the misshapen outer room of solid earthbags and possibly concrete. Whether any kind of plaster on the inside is even possible that wont be destroyed by infrasound I don't know but it isn't built for aesthetics and this isn't a construction form, i'm just trying to give more detail since my giving less detail in the past led to other misunderstandings.

It's possible (am I wrong?) that having the "bass trap" floor to ceiling strawbale walls inside of the nromal walls might even damp frequencies more than normal, since instead of a quarterwave hitting the straw and bouncing back it would actually travel through to the outer wall then back through at a different part of the wave form... to say nothing of bouncing off the nonparallel wall at a different angle before going back through straw, though I could be totally wrong on understanding the physics of that too.

The roof i'm still playing around with but probably on the inside suspended strawbales tied into metal trusses, and the trusses mounted in some way where they wont vibrate. (no metal touching metal) On the outside 'roof' (the outer nonparallel ceiling, still separately constructed inside the barn, which has to be solid to create a solid enclosure and not vibrate or move much) probably metal trusses supporting some extremely metal-braced plywood roof at least an inch thick - not sure if I want solid concrete overhead due to weight. Metal 2x6's like from office framing I think are far stiffer than even 2x12's from wood and if that's bracing it i'm guessing the plywood wont move much. Another possibility is a "double layer outside roof" with metal 2x4's (again still inside the outer barn) similar to how they use double walls in recording studios for extreme sound insulation on the order of 80-90db since at that level there's extra isolation needed between the two stud walls because otherwise the sound is moving through the physical structure. (but i'm just applying it to the ceiling instead) Double doors would be used to enter either part of it, something solid like commercial building fire door with sound absorbant material stuck to the inside to keep it solid and tight. (lighter than strawbale)

HVAC is obviously a special case. Haven't fully investigated it yet. But the barn would be climate controlled to heat/air conditioning isn't needed, just reasonable airflow in when needed. Expected some kind of sound insulated opening/closing doors being an option so they could be closed to seal the room for better bass response for shorter periods. Hell I could even program a timecode to unseal the ventilation when the bass isn't hitting.

I'm hoping this shows I have at least some understanding of what's involved, I was just trying to avoid unnecessary spam until certain "possibility studies" of even reproducing the bass were answered, so tried to say "assume the room will be solid and stiff" to make it easier.

--- next users

Djim -

If filling the entire inside area with strawbale isn't necessary that's another plus, basically though space is cheaper in the design phase, it's not a problem to have 2ft thick of solid straw if I need to. But if stacks in the corners everywhere do it or something that's fine too. It's mostly a solution for a low cost bass trap.

As an off the cuff insertion I tried to join AVSforum but keep having a problem with the "captcha" nonsense no matter what I do, is there any way to get an account registered without all that garbage like if someone already there asks a moderator or something? : P

Don Hills suggestions:

Thanks for your suggestions and yes that's sort of what i'm trying to do. The only downside to an extremely hard cement walled room is that although it would have infrasound I assume the sound reflections from even nearfield monitors would ruin things.

Being "inside the box" still isn't out of the question if you think it's achievable - though the arguments in favor of infinite baffle are still impressing me since it sounds like the huge enclosure volume is more efficient at the extremely low frequencies like 4hz i'd like to reach. If I can hit the db level with 800w instead of 4kw i'd be happier obviously. I'd rather do more drivers and enclosure size than wattage. I'm also wondering whether 21" subs have any advantage - in general I assume it's about pure volume displacement, but the larger cone should interface with the air at low frequencies better since I assume 12's for instance even with the same displacement wouldn't be as efficient. Pyle had some monster 21" subs for cheap Pyle PDW21250 21" High Power Subwoofer 292-2526 - notably less xmax at 9mm than the suggested 'value' drivers Stereo Integrity | HT Subwoofers but even if I used more 21's i'm wondering if the actual sensitivity _at 4hz_ would be substantially better. I'm not sure how suitable they are for infinite baffle though offhand.

What do you mean by aircon ducts tuned to 1hz, is there a way to still get air into/out of the room without ruining the pressurization? Even if it's the equivalent of an "air diode", some kind of anti reversion air ducts like I think mufflers on cars use on the exhaust. Heck maybe even the bass level just triggers a very fast baffle to close off the room to depressurization. (probably not fast enough or too much AV delay for convenience though so something prescripted is still fine - again the mastering room has to hit the level for mastering, the separate home theater room is not quite as demanding and is more of a nice afterthought.)

just a guy -

What about my idea to have ventilation ducts which open during softer bass passages and close during louder ones, controlled by something like DMX512 operation and synched to the movie time? I was going to use DMX512 for "special effects" in room (anything from strobes to fog for a beamshow to wind generators - again for LBE systems it's like "4D" film so anything goes, even smellovision : P ), it's just that particular channel is only for the convenience of the mastering room and abandoned once the mix is finalized and exported for the client.

And yes safety exits would be a given. Even if not required by code. I just assumed those are all questions more suited to construction, i'm here to mostly focus on the bass physics. (and AVSforum if I can ever get onto there :- / )

Inductor -

Thanks for nothing and I never said 1k. I said up to 10k for bass speakers, enclosures and amps alone not including room construction. Stop reading and go somewhere else if you are just posting to be rude and nonhelpful.

PS - to those who have actually suggested truly helpful and new to me information so far, when I finally get things built if your ever in the area drop by for demos and bring beer, your bass CD's and favorite Blurays. : P As long as you don't mind the smell of straw. It's 1.5-2 years off absolute minimum still though.

just a guy -

Though you and Don Hills are developing a cool repoire without me : D, yes you still have me by and large convinced by the Stereo Integrity drivers because of value for volume. Even longer xmax drivers always sound worse anyways - if there were a shorter one in a much cheaper sub to move as much air for the same cost i'd go with that.

My only alternative was the Pyle 21 I linked above, only if it possibly might couple to 4hz room waves better.

Originally Posted by just a guy View Post
I'm not too interested in this type of super high excursion driver since I have no personal need for them so I don't keep up to date with them. [snip] (In case you haven't guessed I have no experience at all with ANY of these, and depending on the alignment, some of the car audio drivers might require some eq, but they all have plenty of listed excursion.)
As someone else noted, I have more of a car audio background - trust me, you aren't missing anything not being up on all those brands. Car audio wants ultimate xmax within a single woofer because they never have enough room for more speakers at the top end of competition. I have plenty of room so i'm looking for value and your suggested value definately seems to be it. There are drivers with up to 52mm Xmax I believe - the Resonant Engineering XXX stuff/newest ones only. But longer excursion is always a loss of fidelity. Plus that's only a little over a doubling for about 5x the price and I don't know if it's any more suited for infinite baffle.

Originally Posted by just a guy View Post
I could get my hands on plenty of straw but I can't imagine it would be anywhere near as effective as rigid fibreglass. If space is an issue, I'd be looking for maximum effect and I don't think straw is the answer.
What kind of rigid fibreglass are you referring to btw? My reason for wanting to use straw is it will be cheap, as i'll already be rural, and i'll be using it as an insulation method on the farm already so i'll already have a heap of bales handy. I should have plenty of space nearly everywhere, easier to make the room a few feet larger to get the best value for maximum STC sound reduction. However the door will still need something lighter and thinner on it.

Originally Posted by just a guy View Post
Can't argue with any of this, but it seems a waste to go to so much trouble to make the room airtight and then have a big vent hole. But if there's no way around it I guess there's no choice... I'm not sure how the serious HT guys deal with this and I'm not quite interested enough to research.
Maybe you've caught up by now and seen my other postings on the topic but just for convenience i'll double post the info. I'm hoping to use some kind of a electric shutter mechanism to close off the air inlet (or at least the outlet/it's possible the air inlet could have anti reversion baffles to limit bass traveling back up the duct) along with things like a low oxygen warning as a backup. I'd have the ducts closed for a few minutes at a time normally with a minimum time between when it can be closed to insure enough air gets back in.

If some other home theater builder has a solution I hope to investigate it maybe at AVSforum if I can ever get on there. Hell I could go with a pair Roots blowers if nothing else - that's a positive displacement air pump, the bass wouldn't be going anywhere and i'd still get air in. I'd just have to investigate how to do it without adding too much noise, long muffled ducts and such. Indoor air quality requirements suggest 15-60cfm per person Minimum Outdoor Makeup Air and a Detroit Diesel 6-71 blower from a junkyard at about 411cid per revolution, so to get 60cfm (upper suggestion for a single person, in reality suitable for 2-3 people) it's only 252rpm or 4 rotations a minute. They can spin ten times that without problem but get noisy. Larger ones move more and would do it more quietly. The point is that with an electric motor would leave a totally sealed room while still providing airflow requirements.

And that's only if the air valves prove to not work well which i'd try first, and if Don's tuned air ports cause too much leakage. (I could readily design a plan that could go any of three ways and try it in the real world to see which works best, measuring things like leakage)

Don Hills

Slamming the door hurting woofers would be protected from with one of those soft-close pneumatic rods like on your storm door. Seems like the easiest solution. : P Plus any larger setup is seeming like it's going to be larger than a door's worth of radiating area anyways. <_< >_>

Though thank you for mentioning that - to be honest that was one thing I hadn't thought of yet.

Originally Posted by Don Hills View Post
Adding another $1K of drivers would certainly help protect the drivers from damage, but would cause significant damage to the OP's wallet. Remember, this is being done on a restricted budget.
Actually it's more a progressive budget. : ) I have no desire to spend more than I have to. But I fully expected to have to possibly spend as much as 10k to get infrasound mastering ability already because I honestly had no understanding of Infinite Baffles and such before. Mostly I was hoping to just space it out over a longer period of time upgrading as needs present themself. So mostly so far it's happy news. But i think a soft closing door, or even something like an additional outdoor air vent which remains open until after the door shut is an even simpler way to solve the problem.

Originally Posted by Don Hills View Post
Anyway, hopefully by now the OP has enough info to decide if he wants to take this path.
Hopefully the blocks of text and I hope signs of research i've done in the past should suggest that i'm still taking it just as seriously. Even if there's still some open possibility between a sealed box I sit inside, an infinite baffle, and an ultra deeply tuned horn sub. My biggest deciding factor between is which will require the LEAST watts at 4hz/best sensitivity. At least it's starting to seem possible now.

Oh and as to building codes i'd expect to have "normal vents" into the room in addition to the Roots blower vents - it's just i'd jam a physical blockage into them when mastering bass. That would qualify for building codes even if my usage of blocking is something you aren't supposed to leave it permanently as, but it wouldn't be permanently that way.

NOTE - as of this point i'm caught up to my last posting (which was unread up to that point) about being stuck with RL distractions. Just for anyone following the thread. Now onto anything posted after that.

Originally Posted by just a guy View Post
It's seriously going to cost at least $10000 and probably a lot more (possibly several times that much unless you are a bricklayer or work in concrete) just to do the floor. Do you still want to talk seriously?
I've done both - helped build forms, work pours, and lay brick before. If the specs for the bass work out i'm hoping to make an above-ground version out of earthbags as a first experiment and if it worked well i'd make an under floor one. (or the horn can be in place of the 2nd room that the infinite baffle since efficiency should be high enough now to make "enough bass" almost moot) The earthbags can provide as much mass as you want, they just don't have a perfectly flat surface - i'm not sure if that even matters at infrasonic frequencies, but if it does it's possible I could lay thick particleboard against the inside over most of the horn mouth if not all of it. Or lay up (mine would be reclaimed) brick or even stone masonry inside like the construction linked a few times. The mounting for the subs would either be poured concrete or something like 2 inch thick particleboard backed with metal reinforcement rods.

I think building a horn for not too expensive is feasible, i'm just wondering what kind of drivers, amps, and frequency response I could expect to get. Since the earthbags (just like the straw) are slated for another project ANYWAY i'd expect the total cost to mostly be the mounting plate for the woofers of steel backed wood or concrete, and the woofers themself. If they were woofers I could also use in an infinite baffle setup so much the better, but i've been told that horn loading 18's breaks them due to excessive pressure and that 15's is as big as you should ever go due to it altering the physics. (according to Bill Fitzmaurice)

That said for the size of the 10hz horn I might want to try and make a tapped horn version of it if the precision needed didn't make that impossible. Since I don't know what response their horn has at 4hz. (which again, may not even be the goal in the end if the electronics make it not work, but still is the preferred goal for now since it seems possible with IB)

The main thing I dont like about the horn or tapped horn is that if I don't match the precision of construction required (i'm hoping it's much easier scaled up to these sizes than precision woodwork, i've just been told how bitchy they are about exact angles and lengths and such esp tapped horns) then it's alot of work (even if I can reuse most materials) for a bust project, and I also don't like the all or nothing commitment - IB's scale up much more nicely. I might even build the IB manifolds for my current house (the basement theater room borders on an empty room that I can readily add them) and later move them out to the new property/house/barn when I move in the future, though anything I do here won't be hitting plaster-busting db or frequency levels because I want to sell this house again. : P

Originally Posted by Don Hills View Post
Thanks for the link. I agree, it is well constructed and worthy of mention and publication, but it does illustrate how hard it is to generate significant amounts of SPL below 20 Hz. They may have indeed measured 140 dB at some points in the room, but I very much doubt that it was at 7 Hz. Simple calculations using fundamental laws of physics
This is why I wasn't sure of just a guy's post about the size of the HT room doesn't matter, unless he just meant that within the range of sizes from a small mastering room to a medium home theater it's irrelevant. My assumption is smaller will give louder deeper bass by allowing pressurizing that smaller cubic volume more easily. Yet the need for 10x Vas sets an absolute lower limit since any time I double the subs I double the minimum room size as well. Since I still don't perfectly understand IB physics, can someone help me understand the difference in efficiency at the proposed 4hz with a room designed for say 4x Vas, 10x Vas, and 20x Vas? I'm thinking that this is going to put a fairly hard upper limit on the db and lowest frequencies available, simply because I won't have the power budget (endless KW) to the barn to do this inefficiently. I'm mostly trying to stretch as far down as I deem is reasonable, using every hack in the book (like a perfectly sealed room for max gain) to begin with, and still keeping the money use as a figure. A flexible figure mind you, but one which was originally planned to be pretty stretchy anyways since I was honestly eyeing 10k not including the majority of construction since that had to be done anyways. The whole home theater setup itself is probably going to have another 10-15k in it not including construction even if the bass doesn't, but that again won't happen overnight and will be built piece by piece at great research for ultimate value probably outdoing theaters costing much more. If you think what I have planned for bass is nuts, wait til you see the rest. : P I expect much more ridicule before i'm done. But this I have to literally design entire rooms around.

Originally Posted by Don Hills View Post
Sorry about that. :-)
Even if you don't take this path, you've prompted some useful discussion of things which aren't often thought about and will hopefully be a resource for others in the future.
I'm hoping to give back too - i'm including some experimentation options if the discussion above makes it apparent, things like the Roots ventilation system to keep the room completely closed and pressurized and efficient. I hope when I actually do construction that i'll set up a blog with photos for everyone. I may very well try to finish the bass project entirely first before even admitting how crazy the rest of the system is going to be. It will be a jaw dropper, and I guarantee people will think that I spent something six figures instead of low fives for everything except... well, the smell of straw everywhere. : P Yet until or unless the budget lets me change all the bass traps for unscented foam it's not a priority to get rid of...

I'm not going to have the money for a 4k cinema projector like the Kipnis Studio Standard but some of the plans are as crazy-nuts in terms of the lengths i'm expecting to go. I'm just focusing my demand for fidelity on things other than the absolute newest of content demanding such setups. And hopefully i'll be able to beat his 4hz, 8hz and maybe 16hz bass figure. (i've no clue what it is, but 132db is claimed total speaker output in his room - his system of at last count 12x 18" vented Snell THX Reference with claimed 8hz response and tens of kilowatts)

Originally Posted by just a guy View Post
These things are thought about constantly and discussed ad nauseum in home theater based forums. This particular forum is geared more towards theory than practice (compared to the HT forums) and here (IMO) loud is valued over low for the most part.
Well in part I was hoping for theoretical discussion unless you mean that's of a higher caliber over there too... this is at this point a theoretical exercise. A serious one, but one i'm still designing up on paper. When I get to actually building I expect I will be more active in other forums more suited to that.

Originally Posted by SpeakerFrank View Post
Maybe as a small advice to Doggyboy! !
Now that others have shown me that what I want is actually within reach I think i'm going to go with my original plan. : )

Originally Posted by just a guy View Post
Doggyboy wants 3 hz. A couple of prosound drivers are not going to do it.
I've compromised 1hz all the way up to 4hz, that's like a 33% improvement, isn't that enough? ; )

The only reason I even said 3hz was because of the Thigpen, which doesn't really audibly provide that in the real world/that's the claimed point where it turns inaudible despite 112db or so in room.

As to specific interests in 4hz - that actually is (just) audible on the Thigpen. That seemed maybe more attainable - it was stated early the Thigpen designers had problems finding electronics to even work at 3hz, yet i've seen Crown amps pull 5hz with no problems in the real world (demo on a friends quad 18 vented monster of a system in a small room) so 4hz made me wonder can I stretch it just a bit. It's also a 128ft pipe organ stop (which has never existed for real on a real organ though a few were designed I believe) and I have a thing for the pipe organ. The one electronic demo of a virtual 128ft stop had me go "oh... my.... god....", yes it really does add that much more than just the 8hz 64' stop, used ultra-sparingly.

(Heard a demo of a 256ft electronic stop at 2hz too, but that seems beyond attainable on my budget without going to something as crazy as 64-128 woofers - yes, that IS beyond my budget anytime soon, and my interest level at this point. Even though i'm sure I was more hearing warbling overtones and i'd still reproduce those instead of the fundamental, so the effect would still be cool, i'm not seeking a true 2hz response.) I also browsed AVSforums and their lists of mega low bass DVD's and was seeing 4hz legitimately listed (no clue how it was mastered in - probably without ever hearing the result, will I be the first?? or did someone else hit 4hz in their IB system?) on waterfall graphs. So hey, why not, it IS out there.

If I can't get 4hz, i'll compromise to 5hz. If I fail at that, it jumps "all the way" up to 8hz, the next organ stop of high interest. For which no, 9-10hz is not enough, I don't want it dropping like a rock at 8hz. : P

Originally Posted by SpeakerFrank View Post
I also want a streetlegal PaganiZonda R, but no way. Not possible on public streets here in Germany and the bigger Problem, the 1.500.000Million Euro and the limited edition of 25 is already sold out!
What I suggested is able to play below 20 Hz with a significant Level and its inside the 5 K limitation!
Well i'm the kind of guy that would build an Ultima GT-R for the upper five figures and probably run with the Zonda on any track in the world I can think of at a twentieth the cost. I find ways. Just for the fun comparison (yes i'm passionate about many things, and many types of fun - home theater is one area, cars are another):

The Zonda R has alot more downforce at speed (Ultima is variable, settable up to 935lbs at 200mph but usually put less for say high speed runs... however the R means race only, the Ultima is still street legal) so without the downforce so on anything but the fastest of tracks i'd probably put my money on the Ultima still. Both are sub 7 minute capable on the Nurburgring. For track-only the Radical SR8 LM got within a half second of the race only Zonda R.

My point of the diversion? If you just want the "name" you can spend 10-20x as much. If all you care about is the performance or the fun, or say getting the job done (my infrasound mastering rig is at least 60% intended professional use, 40% personal use) there are often out of the box ways to accomplish the same goals. If I just wanted to blow money i'd get an array of Thigpen rotary woofers and call it done expecting to spend $40,000-50,000 by the sound of it. People here have already specced out systems using Infinite Baffles for $1000-5000 that will break my house and will require me to build the eventual barn construction very strong to even use properly. This performance level is not unobtainable. Asking to do it on $100 is unattainable, but for multi thousands not really. I just have to have equally reduced cost listening room construction methods (which I do, as being discussed, in depth in the most recent posts) to even make use of 120db bass levels.

If I weren't seeking 120db at 16hz and down response, i'd stick a pair of BFM Tuba Home Theaters in the corner and be done with it - most people describe 120db at 20hz being a reasonable in room expectation. And to be honest that is probably actually the first step - if I don't build an infinite baffle here, i'll be building one or two THT's for enjoying home theater, without infrabass, until I can get the barn built. Then they'll be sold. (or something dumb like sticking both of them into my Caravan : P ) This is just the research project for when i'm able to more seriously pursue my passions of film and experimental music along with other media projects (like the LBE pitches to chinese investors... to the guy b*tching about you wont compete with six flags and disney and etc, think whatever you want, money is falling from the trees for entertainment projects over there in a nation of over a billion people, they already tried to build a freaking pirate Disneyland for chrissakes The Chinese Pirated DisneyLand | Amrit Williams Blog so even if there aren't interested US parties I don't consider it a closed attempt to author stuff for a location based entertainment setup. Even if that doesn't work there's still the use for really good film tracks and music mastering plus that 40% for personal enjoyment.

None of this is expecting to "steal other peoples businesses" - I doubt anyone is going to hire The Fellatio Barn over Todd-AO (okay, that only makes sense if your familiar with Spacemoose : P ) to do their audio - I need a competitive system for MY projects that i'm involved in - what i'm expecting to do is to work with other indie producers to try and do something like a Blair Witch or Clerks or whatever project which gets big, hopefully helped by having an audio mix beyond the norm of what you'd expect for an indie production.

That's almost too much text but misunderstandings have abounded so far so i'm being more verbose now. That's a response to everyone up to present. The next response might take at least a week (or several) due to ongoing RL work, just showing that i'm still keeping track, and hoping clarifying things helps people understand why i'm still aiming at 4hz if possible, considering horns and similar.
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Old 4th May 2013, 09:53 AM   #75
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Dear Doggyboy, what I suggested to you is something that will maybe get close to that what you require in your first Post. A subwoofer that is capeble to work down into the infra range for 5 Grand: Thats what you asked for! It is surely only a compromise, not more but also not less!
And now a word to that Ultimate KitCar on steroids. It is what it is, a Kitcar and so it will perform. A Zonda R is surely not the fastest Car on the planet when its about Topspeed, but be sure its a wonderfull peace of drivable Art and craftmanship, far above and away from that UltimaThinggy! And when you mention the Northloop of the Ring, then I am very sure that these Ultima will not even make it one Lap around the Loop under full throttle! The Northloop is much more then the Simulations in NFS or GT5 or other Computer Games!
The momentary Record with streetlegal Cars and that mens legal here in Germany, fullfilling the German Law and Rules set be the German Tüv is stil 7.11.57!
Why I do tell you that, simple and easy. In the beginning you asked about a payable solution. But what you really want is the the overall Recordholder and that is even a bit faster then the 6.40 Times of Zonda and Radical!
And allow me a last question and thought on that. For what in the world you want a Soundreproductionsystem that is capeble to produce 4, 5 or 6 Hz???
But if this is your own and personal holy grail and then its okay, but be sure about one thing! For 5 Grand, impossible, even when you add another 0! IMPOSSIBLE!!!
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Old 4th May 2013, 01:18 PM   #76
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Originally Posted by SpeakerFrank View Post
Dear Doggyboy, what I suggested to you is something that will maybe get close to that what you require in your first Post.
Thanks for your suggestion but... I will pass. If you haven't read the whole thread i'm already well on my way to designing exactly what i've been talking about based off others results. 7hz is already being done by others for cheaper and at least two people seem real intrigued and wanting to continue to help out.

Originally Posted by SpeakerFrank View Post
And now a word to that Ultimate KitCar on steroids.
If you honestly think that's a "kit car" then that tells me all I need to know. : P [deleted wall of followup text I already wrote before an argument starts since this isnt a car board anyways but i've seen both vs each other in action, at least the normal road legal Zonda anyways, and I suspect you haven't in person.]

I'm not trying to pick an argument here i'm just pointing out we aren't even on the same page of what we consider both priorities and what's not only scientifically possible but tested, done, and verified by multiple others yet just not common knowledge. Your answer was frustrating. I care about finding that uncommon knowledge because I work hard for my money, I want to get a good value for it, to get the maximum out of it possible, and i'm willing to spend exactly what i'm willing to spend to get the performance i've decided is worth having to me whether it's for personal or professional reasons. I see how far I can push the boundary without going into totally uncharted territory and no more. If you don't like the thread then just ignore it completely and you'll be happier, complaining about my post wont make either of us any happier because I dont see where you are going with any of it. :- /


Now back to the REAL reason I came back on already to post a 3rd time/I couldn't view the Wall of Bass article at first but now this time I could so I wanted to comment on it actually.

I'd actually considered something similar myself for years, although I didn't understand the math of the 'lambda' speaker positioning necessarily (wondering whether greater density might be even better) i'd considered a "planar wave of bass" instead of bothering with corner and wall loading at all, and i'd seen some Infinite Baffle pictures not far off from that actually assuming thats what part of the reason was about. If you looked at my initial plan to consider the backside of an IB cabinet with four almost edge to edge woofers I was wondering whether I might achieve a similar effect inside the box actually.

Building a scaled down version of that is not out of the question, i'd probably return to sitting height and a minivan sized enclosure though if possible even if it's long and deep. Yet 7hz is what the other IB guys seem to be hitting so I don't see how it's a huge improvement. (unless that's just flat and 4hz is attainable) I don't know how deep their enclosures are or how efficient either, i'd still trade upper frequency for that 4hz extension.

Just on the subject i'm not sure the 140db at 7hz is completely off either - at 25,600 watts RMS that's about 80db on 1 watt at 7hz or if the 16,000 figure (500rms each for rated volume) is closer then it's 83db on 1 watt at 7hz, this both at 1 meter but it's possible plane-array physics would mean the drop off... possibly even doesn't happen at all. It's not dispersing into a room. The same reason you get corner gain is because the speaker radiates into a smaller cone of area, this is literally like radiating down a long square shaft - whatever you pressurize on one area is going to be the same pressure coming out the other side.

Which brings be back to Infinite Baffles... what kind of 1 watt sensitivity can be expected with any of these monster drivers, pushing and pulling on a pair of 10 Vas or so rooms when we start dropping to frequencies in the 4-20hz range? One page I read claimed it's almost flat (somewhere on IB subwoofer FAQ page by my notes) but I can't see how, unless they aren't meaning as low as i'm interested in.

How does it change for our proposed totally 100% sealed room, with the graph absolutely climbing towards the sky before it ever hit 10hz? Is that possibly a math/computer error or honestly what I could expect in the real world? (i'm so unsure of those results I may very well build up at some point a single 18" 10x Vas enclosure, front and rear, with no air out just a db microphone to test and measure - too small to crawl in but will give me an idea before I plop down money for the rest)

The next thought on mind i'm aware of the incredible solidity of the Wall of Bass construction - although I like the look of it i'm probably going to go with a manifold design instead because i'm not sure if I want to have to make it THAT solid, I read about problems on the IB pages with line arrays. I mean I could it just seems like more expense and trouble than... what is the performance difference vs a line or plane array? I dont mind 1-2 inch thick wood on the manifolds and slightly thinner maybe 3/4" room walls backed by the earthbags for sheer mass (remember i'm not really seeking above 120db so far, there's some movement but not extreme, it's more avoiding long planes of unbacked unreinforced wood and resonant frequencies - for a rule of thumb the absolute minimum weight/density of say an 8ft tall 10ft wide wall/on the small side for the theater room would be 9000lbs and that can be increased if need be, expect a similar solidity everywhere, if I made a similar density wall to compare to the 'Wall of Bass' room it would be in excess of 40 tons vs their 13 tons and for them it's only being used for the driver wall and not the whole structure I think) and I would assume that would be adequate having seen 160db bass boxes being built of wood alone (pressures way in excess of the Wall of Bass, but then they fill the car with concrete to stiffen it instead of the box) because i'm guessing the additional db gained with half ton monolithic blocks of concrete speaker housings is not large enough to be worth it for me personally to eliminate the last few millimeters of cabinet flex. Would it even be over 1db you think?

It's possible some of my previously suggested engineering is overkill even at 'just' 120db, i'm honestly not sure. I like to have a range of possible responses, or the option to upgrade everything later if the 100% sealed room gain and low frequency efficiency enables even higher db levels within my 2kw preferred power bass limit due to sensitivity. But anyone responding to this message 3 - please also read messages 1 and 2 as I put an absolutely HUGE amount of personal information, expansion, explanation, and answers to everyone who had posted or commented so far!

Last edited by Doggyboy; 4th May 2013 at 01:37 PM. Reason: clarifications
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Old 4th May 2013, 01:48 PM   #77
zobsky is offline zobsky  India
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Use a tactile transducer, instead.
"Not everything that can be counted counts, and not everything that counts can be counted." - Albert Einstein
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Old 4th May 2013, 02:10 PM   #78
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Location: New Zealand
Hard walls:
Rigid walls are required for infrabass efficiency. If you're familiar with car SPL then you will be aware that panel flex is an SPL killer. You don't have to leave them bare, you can have sound damping (straw bales etc) to control higher frequencies without significantly affecting the infrabass. You appear to have a reasonable grasp of the mechanics of this.

Try for a concrete roof. It will be stronger and more rigid than most other systems. Most multistory building floors are prestressed concrete slabs or beams, proving the strength and safety of the system. The usual method is to use a layer of prestressed concrete beams, then a layer of concrete is laid on top.

If you choose to incorporate it, you don't need valves etc. Just use long ducts. The length of the duct will attenuate sound, and the right length/diameter will not leak sub-bass. I suggested a duct length that would resonate with the room at below 1 Hz. At higher frequencies the duct acts as though it is sealed. It's just like a vented speaker, there is no significant output from the port at frequencies 4x above the enclosure resonance.

21 inch drivers:
At 4 Hz in a small space, all that matters is volume displacement. This is the amount of air the driver can pump - diaphragm area in square cm, times xmax in cm, equals displacement in cubic cm. Do the sums - some 15" or 18" drivers will displace more than the 21" you mentioned.

Enclosure size:
"True" IB assumes that the enclosure is at least 10x the Vas of the combined drivers. If it's smaller, it's not a problem - it can be equalised out. You may need more power, but not a lot more. Remember, we're not doing a standard SPL calculation. We're looking for a more or less constant xmax from 4 Hz up to 40 Hz or so. This is like the situation in car audio, where a drooping free-air response results in a flat response in-car. If you plot the excursion curve of such a system, you will see a more or less constant excursion below the frequency at which "cabin gain" becomes significant.
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Old 4th May 2013, 02:53 PM   #79
Zero D is offline Zero D  United Kingdom
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location based entertainment design
Unless the site & the people are enclosed in a similar room as you're proposing, they won't experience what you're hoping for. Even if the eventual system is capable of reproducing the VLF !

how much does sound absorbant material affect the efficiency
Inside the room or out ? The more you have in the walls etc, & of the right type, will "help" prevent sound out & in, but mostly @ non VLF f's. SAM in the room won't make much difference @ VLF, unless the room is Massive & almost stuffed with it. Even then it won't make much, if any difference.

no "resonance" even essentially possible.
Impossible, ALL rooms have @ least a fundamental resonance, dictated by the dimensions.

Sound absorption is needed because acoustics are ruined all to hell otherwise with the odd reflections at higher frequencies,
Reflections are how life is, & how we percieve sound. Nobody wants to listen to audio in an anechoic room. Sure too much is bad, think of places like churches etc etc, where "some" people say, ( Ooh hasn't it good acoustics ) Actually meaning it echoes a LOT

but the lower frequencies are tamed.
How ?

If not possible I can go with a 'golden ratio' to try and even up the room modes and spread them around as much as feasible.
Yeah GR makes sense to "help" lesson RM's, but you Won't eliminate them.
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Old 4th May 2013, 03:46 PM   #80
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I'm going to respond to some of this but I don't have time to get to most of it.

First, read post 78 by Don. Then read it again. Now read it 5 or 13 more times. Everything in there is gold, this is the info you need to get started. I know you don't want concrete walls and ceilings but you need them. Do you know what a paper bag looks like when you put it up to your mouth and breathe into it? That's what your walls and ceiling are going to be doing if they are not thick concrete. Do you know how much energy it takes to accomplish that? That is all energy that your system is losing, in other words, it's using a huge amount of energy to move your structure instead of making clean bass sounds. You can make a room within a room if you want but the outside shell absolutely needs to be as solid as possible if you have any hope at all of being able to even perceive 4 hz.

The rigid fibreglass I am referring to is Owens Corning 700 series. Here's an example. Owens Corning 703 1 inch acoustical panels - 12 Panels at best prices - www.TMsoundproofing.com
It's very expensive and very effective. I have no idea how straw stacks up in terms of sound absorbtion and I don't care to research it, so that's up to you.

You only need to absorb through the modal region to take care of the room modes. The lowest modal frequency of the room is determined by the room's longest dimension. It's probably not cost effective or size effective to try to damp the lowest mode, for a large room it could be at 30 hz or lower. No matter what you do, you won't be able to fit enough straw in the room to affect 4 hz (unless you pack it so full you can't enter the room), so don't worry about that.

I've seen some designs that for instance the front of the room is 10ft wide the rear is 13ft wide, the front is 7ft tall the rear is 9ft tall, so that there is no "resonance" even essentially possible.
This is simply not true. There are always resonances. Making irregular shapes will break the resonances up so they don't all occur at the same frequencies. A circular shape is worst, it will have all equal dimensions and the resonance will be a narrow spike at only 1 frequency. Using irregular shapes will break that one strong resonance into many weaker resonances.

For room size (from "what a guy") that under 20hz room size doesn't matter so much anymore if it's airtight...
Click the image to open in full size.

That's the pic I posted earlier. The frequency range of interest is 4 to 20 hz, so as you can see, it doesn't matter how large the room is, in the range of 4 to 20 hz the room needs to be huge to make any difference at all.

(Graph 1 and 3 are rooms with a longest dimension of 6 feet, the second graph is a room with longest dimension of 20 feet.)

The room dimensions affect the room gain, and since the most important frequency is the lowest frequency, and since the room gain at 4 hz is the same whether the room is 6 feet long or 20 feet long, the dimensions don't really matter all that much.

By 20 hz you can see we've already lost 6 db in the larger room (comparing graphs 1 and 2), so it's not like the dimensions make no difference at all, but at single digit frequencies the dimensions don't make much difference (1 db at 10 hz).

I hope that is more clear now.

On a final note, it is absolutely essential that you get a working computer up and running. We can answer questions about IB response, sealed box response, horn response, room gain, pressure gain, etc, all day long and you aren't going to understand anything until you see and experience it yourself. Simulators are the best education you are ever going to get, it will bypass a lot of reading and conversational misunderstandings. You need to see for yourself how excursion is affected by tuning, how spl is affected by having an airtight room, how a 21 inch low excursion driver compares to an 18 inch high excursion driver. We can answer those questions with 100 percent accuracy but you won't really get it until you see it on a graph. The alternative is to learn the equations and do the math but the simulators make it so much easier.
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