Anyone want to help design a new 3-way?

[*B*]

Just about done collecting the drivers I want to use. They are:
Vifa XT25
Seas M15-CH001
CSS SDX7

I dont have the SDX7 yet as I want to only use one per channel for financial reasons, but think two might be better. What are your thoughts?

And I chose these drivers mainly based on me liking the sound of the Seas M15, and found the other drivers to match aesthetics (the XT25 have a copper phase plug as well). So I dont know how these will sound together, but would like some help on crossover design and maybe a few ideas for an enclosure. This is gonna be a slow project as I am quite busy right now. But would like to get it started.

Thanks

[b_force]

I should use a 10 of 8 inch instead of some SDX7.

The SDX does perform very well, but can just not take very low frequencies at high volumes.
But it all depends what your goals are, if you want to make just a really small 3-way system, this could be a solution.

In this thread there are some measurements of the SDX7

http://htguide.com/forum/showthread.php4?t=31673&page=2&pp=35&highlight=sdx7

I added another test from a magazine where the SDX7 was tested at 90dB.

[*B*]

Awesome thanks.
Any particular 8 inchers you would recommend? I am trying to keep this somewhat smaller, but open to exporing other possibilities.

[b_force]

If you want to keep it small, use a Peerless HDS or so.

[Dave Bullet]

What are the voltage sensitivities of the various drivers? Are you going active or passive?

[*B*]

The sensitivities are:
XT25 - 91.1db (2.83v/1m)
M15 - 90.0db (1w/1m)
SDX7 - 85.0db (1w/1m)

And I'd like to go passive

[ThomasW]

Mount the drivers in the baffle where they will be used.

Take measurements of the frequency response and impedance with the drivers in the baffles.

Import that data into a crossover design program and go from there...

[Dave Bullet]

The sensitivities are:
XT25 - 91.1db (2.83v/1m)
M15 - 90.0db (1w/1m)
SDX7 - 85.0db (1w/1m)

And I'd like to go passive

Assuming a monopole design, you're not going to get a very sensitive speaker. Is the nominal sensitivity of the SDX7 85dB? If so - after you apply typical baffle step compensation, you'll lose 3-4dB, therefore you'll end up with an 82dB system and need to pad down the mid / tweeter by 8 - 10dB.

You might be better off investing in another SDX7 per side (= 2) to increase sensitivity back up to the high eighties. Of course, I don't know the minimum impedance of the SDX7 and problems that might present when paralleled. As Thomas said, some initial modeling would benefit.

If you can't measure yourself, look at www.rjbaudio.com for a description of how you can use existing measurements to approximate a crossover. I would also focus on the impedance when modeling, since midbass impedance dips down to of 2 - 3 ohms are not uncommon in a 3 way (depending on your crossover between bass and midrange drivers).

Dave.

[*B*]

Thanks for the link. I'll read into it

[b_force]

It's how you define sensitive

With two driver parallel it will cost more current, otherwise more voltage.
So do you look at the current, voltage or just in Watts?

You can better say that the max SPL with just one SDX7 will not be that high.
Max spl depends on xmax en SD.

On the other hand you must also look at the THD for the lower frequencies and I think a SDX7 just can not run that loud at low frequencies.
In other words, do you define maxspl at the xmax, or do you define the maxspl at a specific THD?

(I'm glad that the word sensitive is used and not efficiency. In the Netherlands people use both words, but the definitions are totally different)