project open baffle and vented mixed

[jafp23]

i plan to build the following 4 way box:

one focal 15WX as (open baffle) up to 50 hz [then falling 6db]

one focal 13WX as vented system up to 250 hz [then falling 12 db]

one or two seas excel M15CH001 as (open baffle)
from 250 up to 2500 hz [both sides falling 12 db]

one morel supreme from 2500 hz [12db]


what do you thing about this speaker

[Roscoe Primrose]

I think you're going to have real problems getting the vented midbass driver to integrate well with the open baffle bass & midrange drivers...

Peace

[slowmotion]

Hi jafp23

Why don't you want to use an open baffle midbass?
The subwoofer could be vented if desired.

cheers

[RR]

Is this what you want to build?

[Rudolf]

My experience says:
50-250 Hz is the range where you want the dipole effects for the most. And you will have a hard time doing an efficient dipole subwoofer much lower than 40 Hz.
So I would do it exactly the opposite way you are planning

[jafp23]

so it is better to make both woofers vented and the rest open ??

[Rudolf]

IMHO the dipole effect will help you most in the frequency range where distinctive room modes are excited. In normal listening rooms this will be up to 200-300 Hz, when room modes follow one another so close, that a reverberant field emerges.

So ideally you want dipoles at least up to 200 Hz.
Building a dipole reaching much lower than 50 Hz will need some HIGH excursion woofers with electronic equalisation. So a vented design might be a good compromise here.

You may use a dipole design up from 200-300 Hz, but (again IMHO) the dipole virtues will become less pronounced with rising frequency.

[Timn8ter]

Just an FYI:

The speaker in the foreground has the upper four FF85K drivers in open baffle and the two FW127 woofers below in a vented cab. The FF85K has an fs of 122Hz and in open baffle I'm sure they're not being pushed down to that level. This is a very nice sounding arrangement, the vocal reproduction is outstanding.

[Rudolf]

The FF85K is one of my favorites too. I have tried it in much larger OBs than yours with a subwoofer. It felt happiest when I crossed over at >200 Hz. But I used only one driver for each OB.

Could you give some detail about your x-over to the woofers? And what about combing effects between the four units? Do you need to exactly align the speakers with your listening position?

Curious
Rudolf

[Timn8ter]

That's not my design, just one I enjoyed listening to tremendously and hope to build someday. This was on display in the Fostex room at T.H.E. Show in Las Vegas back in January. I've been told that it's not a published design, rather one of the Fostex guys personal design. I would love to know the XO design too! With OB I didn't experience the usual line effects you get with a box.