Midrange: sealed dipole vs OB mounting?

[OllBoll]

Hello to you all!

I'm considering doing dipole and am concidering how to design the best midrange ( ~ 400 to 2200 in my case ) possible without breaking the bank too much

My first possible choice is to simply do a standard open baffle with M15CH002, nothing fancy here.

The second is to use the 6nd430 which according to distortion measures by zaph should run circles around the M15CH when used as midrange. The 6nd430 however doesn't have that nice open magnet structure and I want as close to identical front and rear dispersion so I've thought about two possible configurations:

The rightmost is the standard open baffle, the leftmost however is what I wish your opinion on: would there be any sound quality compromises in doing this closed box set up compared to the open baffled version?

I will use EQ so I don't care about exact response unless it can't be EQed away, but about what will get me the best sound quality.

And if anyone wonders why, to hide the magnet and unify dispersion is only half of the truth... the other half is that the box would be half as tall

[picowallspeaker]

Have you considered also an 'only frame' speaker suspension ?
So you don't have to deal with a baffle at all .
But..only in case you fear of vibrational effects from/to other parts of the system.
I would surely build the boxed dipole ... for my taste it's a little too expensive !
At least , you know what you get when passing from to monopole to bi-pole the dipole listening . I do prefer classic monopole , as no extra EQ is involved thus playing with passive EQ requires less circuitry .
But...I remember my experiment with boxed dipole like the sketch on the left ( way cheaper than m15 ....) produced a nice attack from the drums !

[AllenB]

With the left option, the dipole effect will stop earlier due to the greater front to back distance, however with the driver baskets exposed, you'll have to cross lower as diffraction will cause problems.

[OllBoll]

exactly, shouldn't the left option be approximable as a single driver but with a larger baffle?

What I wondered mostly is if the actual internal box will add distortion or coloration or if it would sound at least as clean as the open baffle.

[pieter t]

The left option will have lower efficiency as it is functionally one driver.
I tried a bit with MTM on open baffle; the diffraction at the back side when mounting the drivers both "front firing" is nothing to worry about. At least I could not hear something "wrong". Sound from the back of a dipole is reflected anyway. You could easily try the right version both ways and check with your ears.

[sreten]

Hi,

I think a single driver open baffle is your best option, exactly matching
the front and rear response seems too expensive (needs two drivers)
and will introduce more lobes at the c/o point to the tweeter.

The left is a bipole, the right is a dipole, they are very different.

rgds, sreten.

[picowallspeaker]

Left is ....right !

[picowallspeaker]

Originally Posted by sreten

The left is a bipole, the right is a dipole, they are very different.

No , if the drivers are wired appropiately

well ,maybe some offset between the centers might be taken into account ...

[AllenB]

Sreten, the first option has the drivers out of phase (as well as physically reversed).

Peter, good point about the efficiency but they are connected isobarically. What would you think about using some pvc between them but retaining the box as a baffle?

OllBoll, there are numerous reasons I might be reluctant to cross too high. Anyway, your box is interesting because you could round the sides to reduce diffraction, eg: cut some pvc pipe in half which will fit front to back corners of each side of the box.

[sreten]

Hi,

Sorry I missed the box wiring, still seems a too expensive solution, and
wont the box version introduce a dip related to the driver spacing ?

rgds, sreten.