DIY 2225 and 807-8a

[marcstpierre]

heres a pic of my new project, 2220a recone 2225h and 807-8a driver on 811b. custom cabinet with laminar ports.
not finish yet,work in progress.


63723

[1audiohack]

Welcome marcstpierre!

Do you like the sound or has it played yet?

Barry.

PS. To anyone thinking about it, 2220 cone kits are now NLA from JBL so lets not even get that started please.

Thank you.:)

[grumpy]

Nice work on the cabinet :) Do you have some technical info on
what appears to be a variation on an "onken" style design (such as the
partial loading on the cone front... visual, functional, or both)?

(not building one, just ever-curious)

[marcstpierre]

still in the shop,finish not done yet. i dont have a crossover design also,set for now,if you have any suggestion?the front design ie slot for the woofer, is to slightly increase spl and dynamic,by increasing pressure at the mouth of speaker, inspire by horn loaded speakers,if i dont like it, i just do the circle.
The purpose here, as with Oskar's transformer, was to have the air velocity at the output to be much faster than the velocity of the driving surface, in this case the loudspeaker cones. The motional energy imparted to the moving air is proportional to the mass of the air times the velocity squared. The "squared" part means that if you triple the velocity you impart nine times as much energy, or about 9 dB worth. This raises the efficiency of the speaker quite a bit, and it improves the transient response as the apparent mass of the air moved is higher in relation to the cone mass of the drivers. The way this is accomplished is by "squeezing" the air through an opening narrower than the surface of the moving diaphragm of the driver. In the diagram above, the air pushed by the cones has to exit out the front of the loudspeaker through a slot opening whose surface area is only about third that of the cone drivers, and so it goes out about three times faster than the velocity of the cones.
in my case the opening is two third of the opening of the driver,so it should go two times faster than the velocity of the cone.
i hope an increase of 3db. on the shop radio the result seem very interresting, also for the lower mid,but its too soon to know.thanks for your interest.

[marcstpierre]

as explain,the slot opening in my case its 2/3 of the driver surface, the velocity is suppose to be two time faster than original,i expected an increase of 3db.
time will let me know if i was right. i hope.

[marcstpierre]

Do you have some idea for a crossover?
4430 or altec? hibryd?

[marcstpierre]

do you ever try this,its like the opening of the a7,:)