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Old 6th April 2004, 09:39 PM   #131
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Default Re: Re. 2.5-way?

Quote:
Originally posted by DeonC
Furthermore, how about changing the tweeter for the Vifa XT19TD00-04 ¾" Dual Concentric Tweeter? Or any of the Dual Concentric Tweeters for that matter? Should be a killer speaker.


AFAIK this tweeter needs a fairly complex crossover and thus not suitable for newbies.
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Old 6th April 2004, 09:40 PM   #132
DeonC is offline DeonC  South Africa
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Quote:
AFAIK this tweeter needs a fairly complex crossover and thus not suitable for newbies.
Such a pity. It looks to be a good one

Deon
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Old 6th April 2004, 09:49 PM   #133
DeonC is offline DeonC  South Africa
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Default Re. Tweeters

Hi guys

I just thought about something- has anyone considered the Fostex FT28D tweeter? It looks good, albeit a bit expensive. The specs in brief are as follows:
Impedance 8 ohm
Resonant frequency 850 Hz
Bandwidht 1kHz÷50kHz
Sensitivity 90 dB
Music power 40 W

Any one have any ideas\experience?

Deon

PS. Go here to download the complete spec sheet. It is in PDF format:
Fostex FT28D Further Specifications
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Old 6th April 2004, 10:33 PM   #134
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Default Re: Re. 2.5-way?

Quote:
Originally posted by DeonC
What about a 2.5-way? With the proposed baffle width (170mm), the baffle-step frequency will be circa 2kHz. So the upper P13 can have a 1st order XO at 2kHz, the lower P13 run full-range, and the proposed 5uF cap on the D27TG.
17 cm is approx a 680 Hz baffle-step (or less)... in a 2.5 way i always like to put the 0.5 way on the back so that the phase-roll of the 0.5 woofer doesn't mess up the midrange... you can also load push-push for better micro-dynamics. As well getting the electrical roll-off perfect isn't as critical because the box will guarantee perfect fill-in.

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Old 6th April 2004, 10:34 PM   #135
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The D27 is an ideal tweeter because it's sensitivity is a very good match...

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Old 6th April 2004, 10:39 PM   #136
DeonC is offline DeonC  South Africa
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Hi Dave

Quote:
17 cm is approx a 680 Hz baffle-step (or less)...
????? How do you get to that figure? 17cm = 6.7", and I still get between 1950Hz and 2kHz. For 680Hz I get a baffle width of between 48.5cm (19.1") & 50.5cm (19.85"). How do you calculate baffle-step?

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Old 6th April 2004, 11:09 PM   #137
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Quote:
Originally posted by DeonC
????? How do you get to that figure? 17cm = 6.7", and I still get between 1950Hz and 2kHz. For 680Hz I get a baffle width of between 48.5cm (19.1") & 50.5cm (19.85"). How do you calculate baffle-step?
If the baffle is measured in inches (W=17 cm = 6.7") then the formula for BS F3 is 4560/W = 680.6 Hz.

This is the accepted formula derived empirically from Olsen's graphs. Newer software BS smulators that take into account non-square baffles tend to predict a lower F3 yet.

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Old 7th April 2004, 12:05 AM   #138
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Hi Dave

Quote:
If the baffle is measured in inches (W=17 cm = 6.7") then the formula for BS F3 is 4560/W = 680.6 Hz.
I think we were talking about the same thing, just different points. I read the article again, and the calculation you're doing is for the f3 point, which I guess is more usable if you are calculating the XO points. Take the following fomula:
Click the image to open in full size.
That is the equation I was using. The f3 formula is:
Click the image to open in full size.
That is the equation you were using. My bad. Sorry.

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Old 7th April 2004, 12:41 AM   #139
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Quote:
Originally posted by DeonC

Click the image to open in full size.

Click the image to open in full size.
I recoginize those graphics :^)

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Old 7th April 2004, 04:48 AM   #140
Jay is offline Jay  Indonesia
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Rabbitz,

Is the xo you sent to x. onasis copyrighted? Do the drivers "lock in" beautifully?

x. onasis,

I hope you'll come up with a good speaker so I will be motivated to buy the drivers.
Currently I need a good looking small speaker to be used at office. I have a 6"
local driver (called Tango) as a candidate. Not as detail and sweet as P13 but
better dynamic and very low bass. I need one that work good in low SPL.

The P13 is really sweet in midrange, and I feel that the midrange quality is very
important for music enjoyment (when listening to vocals). But 5uF D27 could be
a problem, especially when we expose the midrange quality as in small speakers.
In floorstanders, we expose other qualities (transient, bass) that will make the
problem with D27 become less important. The problem is not only the harsh
sounding (like what coolkhoa is anticipating), which is true, but also the phase
problem. For the harsh sounding problem, may be you can damp the chamber
with wool.

As I can remember, the D25 has qualities that better the D27 (to be match with
P13, P17 or even several other drivers I have tried). But that is just my opinion.

I really don't think that P17 is a better option than P13. If you insist a P17 project,
it should be a high power teenager system with a lot of (not so low) bass, a
floorstander. I think EROS is the best implementation available on the net. And
there are also many other implementations (John K's for example) so building a
completely new design is not supposed to be done by newbies.

If you want another project using P17 and D27 (called the Pilotis), I think I can
send you the xo information (this one is not on the net). This speaker is popular
here, and seems many here can live long with it.

Coolkhoa,

It is sure that the D27 will be harsh sounding with only one cap (even with second
order accoustically). The problem is to find out how important or critical it is.

With P13, no matter where you cross it, it will still be sweet. But I usually search
a point where the driver produce the most natural sound (sweet doesn't mean
natural), and it is usually lower than what creates "sweet" sound. IMO, the natural
sound will be produced if the driver mechanics (cone etc) doesn't introduce their
own sound, and so the sound must not be heard coming from the driver.

Dual P13 in MTM? That's the Ariel. I usually against double woofer, but P13 is
very good at mid with the compensation of weak bass. IMO, the best choiche to
expose a bass is by means of a good enclosure. But I think I have never seen a
small MTM like Froy/Odin/Gemini. That will be an interesting project.

Jay.
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