Romy the Cat wrote:

After a few hours of moving the right channel (digital crossover was not used) this is what I was able to come – right channel bass section with no filtration. This is the very best among the worse and as you can see it is very unusable. What I am thinking from here is to cut at ~50Hz with 3rd-4th order and rise gain for 5-6dB.

jessie.dazzle wrote:

Have you tried taking a measurement with the line arrays moved to the rear of the room? (ideally, he same as the current distance from the listening point, but behind you).

jessie.dazzle wrote:

If the measurements still show a strong 60Hz spike, you might as well get on with the construction of two new pairs of channels crossed as you have mentioned; mid-bass horns running down to the spike and lower-bass channels running up to the spike. Once this is done, the line arrays would be redundant, and that 60Hz spike may end up being your new best friend.

Wojtek wrote:

splitting the bass arrays on more sections(I think its possible?) trying to get rid of resonances and counter the nulls. Surely you would loose efficiency of line arrays. Maybe not such a bright idea after all but it's what Earl Geddes advocates all the time.

Paul S wrote:

Then, rent some serious self-powered "subs" and run the numbers.  With w/w carpet and band-specific "treatments", it could take kW.

Albert wrote:

If you could tune the resonence of the Helmholtz resonator, moving the middle of the resonence up or down. it looks like it is at 63hz. Moving it down to 47hz or up to 75 or even 112 would smooth things out and help to avoid high order x/o. The question is how to tune it?

msaudio wrote:

Also i would be very interested to see the lowend response in free air, in the back yard from your right channel?

Bill wrote:

1. Put a door in front of the alcove that is casusing the resdonance and line it with 6 " of sonex. May turn the space into a bass trap at 60 Hz. 2. Put an adjustable  notch filter into your crossover at 60 Hz.

jessie.dazzle wrote:

You might be able to get away with a bit less; if I remember correctly, my calculations at the time (based on the above driver) yielded a theoretical ideal volume of something like 23 cubic feet (sealed), so still not something one would casually push around.

I do not know what drivers I would go if I switch from my current arrays to two lower bass midbass but Jessie brought an interesting subject: what the size of sealed box would be “enough” if I go with 1808.

The drivers’ data is available from here:

http://www.baudline.com/erik/bass/bass_list1/Aura_1808.html

The folks, who love to do predictions, please do them. I have few 1808, a few Fane Colossus 24, a few 18” JBL (do not remember name) and many Altec 515G. Probably 1808 would be a good choose. In reality has Fs! 28Hz but the rest usually is fine and it will be able to do good job in proper enclosure. What the size of enclosure would be enough for this driver?

Or course it shall be a sealed box. Jessie went for 23 cub feet, shall I go larger? My impression was that it needs to be 35-45 cub feet. I spoke with my carpenter last night and discussed if it possible to load the boxed into the frame of the house. It is possible and my house has two very good locations …. but it will be 2.5 week of his work. So, expensive and I need to be truly sure that I would like to do it.

Romy the Cat wrote:

jessie.dazzle wrote:

I just ran the calculations again and came up with a figure of 13.8 cu ft (for a QTC favoring transient response, not lowest F3). Then I measured the boxes and they do in fact come out to just under 14 cu ft, once wall thickness, volume for driver and bracing are subtracted. Plugging in a QTC which favors lowest F3 results in a box about half the size.