I am remodeling my living room and will install my 45 year dream speaker system in the ceiling. 4 midrange and 4 tweets mounted high in the corners of the room. Centerpiece of the installation is two 12" woofers which are installed at the opening of sound muffling tubes. The tubes are about 10' long and vent to the outside air, so any back pressure from reflected waves should be infinitesimal.
What characteristics, aside from magnet weight and flat frequency response should I be considering in selecting these bass speakers. I have been told the the mechanical q in an open baffle system should be high, but would like confirmation as I am uncertain. I am tentatively looking at bass drivers with Q(qms)=5, and Q(qts)==0.33.
Any ideas/comments will be welcome.
Bill
The only dreams you will get out of that system will be nightmares.
First of all that is not an IB system at all. It will be an undamped stopped pipe, otherwise known as a Gedeckt pipe.
It will have a huge resonance at Fp which will be at 28 Hz with strong undamped harmonics at 84 Hz, 140 Hz and 196 Hz. Not good.
An IB needs a huge unrestricted space, so that the space does not influence the driver.
So the Q of the system is the Qts of the driver.
The problems with IBs are many. You need a drivers with low Fs, as this will effectively set the lower limit of the response. You need high Qts for a driver, which implies a loose suspension.
So you need drivers, with an Fs around 20 Hz or less and a Qts of around 0.45 or the sound will be too "dry".
Now the total sound in the room is produced by the movement of the driver cones, which is inefficient. So you need large excursion drivers, which is to say ones with a very high xmax. So it needs to be over 20 mm at least.
So you have large excursion drivers with loose suspensions, so they will not take a lot of power without damage.
That means for a very small room at least two 15' drivers, for medium to larger rooms four 18" drivers at least is optimal.
For reasons of rigidity and cancellation of vibration and resonance, building a very strong manifold to couple to the IB space behind the drivers is to be preferred.
Mounting multiple mid range drivers and tweeters in the ceilings in the corners, is too grotesque to contemplate. All you will get is a muffled sound from on high with massive response irregularity from comb filtering and reflections. You haven't even begun to consider how you get from the lower end of the mids, to that dreadful sub.
This is an idea in its present form that needsh burying fast without decent burial.
