Arny Krueger a écrit :
"Lionel" wrote in message
Arny Krueger a écrit :
"Lionel" wrote in message
Arny Krueger a écrit :
"at" wrote in message
Any ideas or recommendations?
Rethink your application. There's a number of reasons why virtually
every speaker system with pretentions to quality is at least 2-way.
Don't you like the frequency response of the one I have chosen ?
http://www.madisound.com/ff225k.pdf
Two pretty serious problems:
(1) Xmax of 0.3 mm, when it should be 3-6 mm if an 8" driver would
have serious bass.
Perhaps a begining of answer to this problem :
"Just another word on xmax. It is specified by the simple relationship
of the voice coil winding length to the thickness of the top plate (or
pole disc in the enclosed neodymium designs). So, for example, if the
metal that sets the gap length is 6 mm in thickness and the voice coil
winding is 7 mm long, then X-max is .5 mm before the amount of voice
coil in the gap decreases.
That is all this specification means. Drivers can excurse farther than
X-max. The distortion just begins to rise when they do. Excursing just
slightly beyond X-max produces a very small increase in distortion.
Hitting the excursion limit of the driver produces much more
distortion.
If you eliminate a driver just on X-max alone (and you are not
planning on using it as a subwoofer), then you have made a mistake.
I didn't make that mistake, did I? I also criticized the speaker for its
lack of high frequency disperson, right?
Also, consider what sort of Xmax we are talking about. 0.3 mm is very small
Xmax for an 8" driver that we expect to reproduce 80 Hz cleanly. If Xmax
were 2 or 3 mm, I would be more likely to excuse it. Of course, I'd like to
see Xmax of 10mm or more for a subwoofer.
My problem Arnold is that I don't really like the sound of "modern"
speakers because I like quick and precise answer from the bass an not
this diffuse and not well defined loud bass that we can hear from a lot
of speakers and moreover from a lot of subwoofer.
In fact I just need to reproduce with the maximum fidelity the sound of
a double-bass.
I understand that my point of view is perhaps not really academic, but I
should also comply with the fact that there is no banker in Chapuis'
family. ;-)
Please do not over generalize. In the realm of a wide-range driver,
there are so many other things that matter so much more to the sound
of the driver than its X-max. If I was building a high SPL subwoofer,
then I would be concerned with X-max.
Frankly, you have to watch Xmax even with midrange speakers.
As I have stated in another thread, in full range or wide range
drivers, large X-max is going to limit top end.
Usually issues like cone breakup and disperson get you first.
You cannot have both.
Large X-max requires lots of voice coil out of the gap. This adds
mass and increases coil inductance. Both decrease the top end of the
driver."
In fact, drivers with Xmax in the 6 mm range can respond pretty well up to
about 4 KHz. Remember, I cricitised the proposed driver starting at 1.5 Khz
based on treble dispersion.
http://www.diyaudio.com/forums/showt...935&highlight=
Well, this guy takes a completely different tack. He claims that the Xmax is
really more like 3 mm. However, he's really talking about Xsus, not Xmax so
he's not really shedding any new light.
(2) Note that the off-axis treble response falls off above 1500 Hz.
Is it not a common behaviour ?
It's common enough that people use tweeters to deal with this problem! ;-)
Ooops !
I know that I will have to help him with a tweeter over 10 KHz but
this will be done with nearly no electronic, just *a* cap !
Often a 2 KHz crossover can be done with just a cap. This woofer is smooth
enough in the breakup region that you don't have to get agressive about
rolling off its high end. The other thing to watch out for is tweeters that
actually get a peak in their low end response when driven with a simple
capacitor.
I have learnt about this issue. I was thinking at a transition with a
simple 0.47 µF cap according to Fostex recommendations (perhaps a Jensen
one in order to give a little bit of blue blood to my speakers)
).
I will built these speakers like that because I like the horn design and
that it will put me serious problem of construction skill ;-).
Thank you anyway for these interesting technical comments. I hope that
when the the speakers will be finished I will be able to make objective
critics. I guess that at this moment your today comments will be
usefull. Now I am too much engaged, I already dreams of them. :-)