Tech challenge: neighbour-friendly high eff. designs?

[Karanael]

Lo all

I'm due to move into dorms at Glasgow University in september, and I'm worried. very worried, as I'm currently used to some Tuba 24's and DR250's for PC/HT/music use. Being complete overkill for the most part (gotta love bass extention to the low 20's!), I think I need a different solution, especially as this kind of bass extention is not tolerable under any stretch of the imagination in university accommodation.

Anyway, my technical challenge is this:

Is it possible, through reasonable use of technology, to provide the sort of sound quality (especially bass, which is the issue here) I'm used to with my DR's and Tubas, in a single room, without affecting my neighbours?

I experimented with an Autotuba design and a few other folded horns with some quite positive results, especially in sealed rooms. Can any of you audiophiles think of an acoustic means of controlling where the sound ends up?

What I was thinking was that if I can control the movement of the actual subwoofer (assuming that's what I use - all kinds of jazz like line arrays, horns, TL's etc are feasible) and its cabinet isolated from the room itself, then the only energy emitted would be through the air.. Is this technically possible? Sorry to sound like a noob, but I'm working on this very problem myself and I thought it'd be best to give you lot something productive to set your minds on so I'm not working in a vacuum

How about...

a folded horn built with a padded bottom/sides/top, designed to prevent transfer of physical movement or vibrations to the surrounding room, pointing towards the front of the listener in a nearfield arrangement (maximum audibility for minimum actual energy = more efficcent = less power 'wasted' in shaking the room)...

With a pair of midranges, again acousically isolated from the surroundings, in a nearfield line array? If they're all 'pointing inwards' to the listener, then I'd probably end up with a selective comb filter... if I make it so there's a wide horisontal sweet spot, and very high vertical dropoff, I could get more sound in the correct places through virtue of increasing 'efficcency'..... and some tweeters on top for good measure


Again, this is all speculation... but having discovered high-efficency cabinet designs (Tuba! DR! *Dance*) I don't think I could ever go back... they're so so selective, but so powerful at the same time. If I could do a similar thing, but instead of focusing on maximising output from a certain input power, I minimise sound pressure outside of the desired listening area... that would be another use of said high-efficency designs.

I hope I'm not rambling too much here, and that I inspire people to scratch their heads and think, "hmm... how could we do this?"..

I'm going to have a play with my Autotuba tomorrow, try and find a way of reducing the amount of floor-shaking it produces. it's so much better than a pair of 15's for that lol, now I know where all that energy was going...

Thanks all,

Karanael

[Cordraconis]

Open baffle would be best for directive bass.
However, if you are used to horns ...

Tip: Good headphones! I have Sennheiser HD25-1, and I payed 219€ for them. They go from 30Hz-18000Hz at -3dB, and 16Hz-22000Hz at -10dB.
Plenty of loudness and most important: they stay cristal clear! i run them directly off the onboard soundcard, and if you disable all unused line-ins, mic's, etc ... noise is actually a LOT better than if I run my fathers Onkyo amp between them.
Their isolating capabilities are an extra bonus if your neighbours make the noise for a change.

Most important: make sure you have good neigbours! If you have to spend your years like the ***** I had my final year, getting yelled at, and then getting yelled at more if SHE woke you up slamming her windows for the guy's under her room that you didn't even hear ...

I should have put my foot down the first time and turned the volume UP instead of giving her a finger so she could take an arm ... grrrrr ....

Woops, let myself go again.

[johninCR]

Dorm choice is important. My first year my dorm room had 1ft thick concrete walls floor and ceiling, so only the door and windows where a problem.

Also, Cordraconis hit the nail on head with the dipole suggestion without really explaining. You can have tremendous bass in your listening position and not much outside it. The nulls in the radiation pattern are vertical and to the sides of your speakers, so the energy going to the floor, ceiling and side walls is nothing compared to typical boxed speakers, so the sound stays confined your room much better.

[AJinFLA]

Horns like yours + dorms/neighbors not hating you = oil + water. My suggestion would be an OB coaxial (high efficiency - if you must) single driver, capable of bass down to say 100hz or so. Coaxials integrate well even in the nearfield. Heavily treat the walls behind the drivers with some sort of sound absorbent material to absorb some of the rear output. Treating the whole room will help with the neighbors some, but (possibly) at the cost of too dead a room. Use a tactile transducer at you seating position/chair/sofa (or several ). I don't know what would be available where you are, but here are some examples :
http://www.partsexpress.com/pe/showd...number=299-028
http://www.partsexpress.com/pe/pshow...=290-500&DID=7
http://www.partsexpress.com/pe/pshow...number=294-718
The acoustic treatments can be found rather cheaply here at any hardware store, usually in building materials.
Otherwise, there is always headphones + bass shaker.
I'm actually building a dipole based on a KEF ceiling speaker this weekend. I'll post it as soon as it's done.
Good luck. Study hard off course (hopefully EE)

Cheers,

AJ

[Magnetar]

If you have significant output below 100 cycles (say 120 db) try moving to a place that has a basement. Otherwise forget about trying to 'trap' the bass from bleeding into adjacent rooms/homes.

I've seen measurments from these 'tubas' and have to say they really aren't subwoofers - The horns are WAY undersized to produce low bass - not much response at all down low. What spurred you to build them?

[thylantyr]

.. or move away to isolation, an audio system in a cave .........................

Hire Alfred to keep an eye on things .

[AJinFLA]

Well, its not "done", but I promised pics ASAP in my earlier post. OB point source driver. KEF Ci200QR. Audax bass drivers. I just got them home tonight, so no details yet.

I really must get to sleep

Cheers,

AJ