Seas G17REX/P (H648)

[rho]

I'm looking for some nice drivers for a small 2-way speaker. I was thinking about the Seas G17REX/P together with the NoFerro550.(H1149)
Datasheet H1149 Datasheet H648

Has anyone used these drivers? In what kind of enclosure did you use the low-mids? How low could I cross the tweeters?

Any advice is appreciated.

[p_ete2003]

Hi Rho,

I haven't used G17Rex/p, P17Rex is a good driver thou. If you like to check the bass area try the winisdpro, you can get it from http://www.linearteam.dk/

I wouldn't use any tweeter under 2000Hz preferably not under 3000Hz. With G17Rex I think you'll have to use the tweeter on it's limits.

I would think some else midbass driver with H648


regards,
Pete

[rho]

I'm Sorry: The H648 is called REX171EX-GF
But the REX171EX-P looks nice too.


I use WinISD but don't trust the results that much. It models the enclosures for most drivers very small compared to recommended enclosures. I don't know why, but it just does in most cases.

Why wouldn't you go any lower then 2-3kHz? Distortion or powerhandling?


Those tweeters are build to be crossed at rather low frequencies.
The last edition of the German magazine tested the NoFerro800 and it seems to work fine down to 1.5kHz, so 2kHz would be fine I think. The NoFerro550 has even lower Fs so I think the 2kHz would turn out nice. Higher cross-over points would bring the low-mid in trouble I think.
But all of the all of the above is "guessing", so real experiances with these drivers would be nice.

[rho]

There is somthing strange about the names that are given to the drivers around the world.
Seas says it's the G17REX/P but in Germany it's called different. But I'm sure it's the H648 and that is the G17REX/P according to the datasheet. So thats' the driver I'm asking about.
....confusing stuff....

[p_ete2003]

In generally I wouldn't use any tweeter under 3KHz because the powerhandling and also prefer 1st order xos.

[rho]

OK, with a 1st order x-over it is a good idea not to x-over too low.

The recommende freq range of the 17cm drivers goes up to 3000Hz.
At 2000Hz the distortion-levels from the NoFerro are rather low. Even at an output of 107dB. Even K2 will not go over 1% at that volume-level.
With a 12dB/oct it wouldn't be a problem to cross it between 2000hz and 2500hz, would it?

[p_ete2003]

If you use 2nd order, you'll get 12dB / octave drop and 180 deg phase shift. If you have a mic and foe SpectraRTA you can check the bass/mid and tweeter xo freqs separately.

I would try 2KHz for the bass/mid and 4KHz for the tweeter (2nd order) at first. I think you should first make the speaker and then listen to it and after that adjust the xo.

Which kind of cabinet will u use? How many litres and tuning freq for the port?

[rho]

I'm not sure yet about the drivers but if it will be these Seas then they will be in a 14 liter box ported to ±48Hz.

Uhm, why the tweeter at 4kHz and the low-mid at 2kHz?

[p_ete2003]

If you use 2nd order xo you'll have 12db drop/octave. Mid from 2KHz to 4Khz is one octave. If you mix the mid and tweeter between this you'll have straight line, right?

[rho]

Isn't the cross-over freq specified by the -3dB point?
If it is not it would be like this. (IMHO)
low-pass: -12dB at 4kHz
High pass: -12dB at 2kHz
That would make the coss-over-point 3kHz (your favorite? )
So, about 6dB down at that point.........add them up and........you are right.

Did I get that right?