FAST or STAFT (WAW or STAW) Which is Better?

Jump to Latest
#122
Just saw a pair of these old school things on ebay. Interesting FAST type design with stepped baffle for time alignment and separate enclosure for the 'fullrange'.
Admittedly the XO is 2500hz so a bit more '2 way' area than a true fullrange assisted jobbie.
1st order on the woofer and 2nd on the HF. Probably sound 'average' as is but would be a good project to stick some modern drivers in there!
 

Attachments

  • sb-4000-service-manual.jpg
    sb-4000-service-manual.jpg
    503.1 KB · Views: 368
  • sb-4000-crossover-circuit-diagram.jpg
    sb-4000-crossover-circuit-diagram.jpg
    388.5 KB · Views: 381
#123
It's just a cone tweeter. Quite common for many years, sadly only a handful made today.

Don't kid yourself about the 'modern' drivers part -some of those old Technics linear phase models were actually quite good. Crossover caps may be shot now if they aren't film types, but that's a straightforward fix so if otherwise in good shape, they'll still make decent music for somebody.
 
Last edited:
#124
I bought some of those super cheap Monacor dome tweets but haven't played with them yet.
No I realise my comment about the drivers isn't quite correct. I have some old 8" wharfedale and leak units i have tried and they are pretty decent if you don't need too much power handling.
 
#132
I see a 6 and a 12 (out of phase), and I"ve no idea what natural driver roll offs are.

I'd like to see a driver 6db down at crossover point and 12db down an octave away.

Am i wrong ?

I've got to do some digging on my understanding of crossovers........
 
Last edited:
#133
Look at my 10F/RS225 FAST thread. I have an 8in and 3.5in 1st order XO. The driver choice for woofer is critical - must be smooth and flat with breakups at least >2 octaves above the XO. RS225-8 in unique, very few other 8in woofers are as flat and have breakup at 7kHz (nearly 3 octaves above XO point).

656204d1515700364-10f-8424-rs225-8-fast-ref-monitor-xrk971-10f-rs225-fast-freq-jpg
 
#136
oon_the_kid said:
After all, real musical instruments are omnidirectional.
Click to expand...

Not at all.

Comparison of different microphone positions for orchestra instruments


norman bates said:
Is it ?

Much of intelligibility is helped from the letters s and t.

The uppermost harmonics of these letters is around 8khz.
Click to expand...

Having RTA'd this stuff, go up another octave, easily, unless you're using something like an SM58. Blowing air through a narrow aperture (like teeth) will result in a whistle, which in theory would have a large series of harmonics well into the HF.

xrk971 said:
AllenB,
From a physics standpoint, Newton’s 2nd law would seem to indicate that a lighter cone would be able to respond to dynamics faster. Lighter mass, faster acceleration. One reason why ribbon tweeters seem to be able to effortlessly go to higher frequencies.
Click to expand...

... Or it implies a larger amount of force must be applied. ie, heavier cone = lower efficiency.
+1 on Scott's mention of acceleration correlating (loosely) with HF extension.

Using Hornresp, it can be found that acceleration is low at low frequencies, even though excursions can be large.

Chris
 
#137
Right. Assuming oscillatory (pistonic) conditions, transient response in a drive unit is proportional to how quickly you can slew current through the coil, as Dan Wiggins & others have shown. The mass of the moving components relative to the available motor power simply determines how efficiently the electrical energy is converted into mechanical movement / acoustical energy.

An even simpler way of looking at it is this: ask 'can this drive unit produce xyz frequency under pistonic conditions, with no HF drop-off through VC inductance'? If the answer is 'yes' then by definition it can move fast enough to handle all lower frequencies down to its mass-corner.
 
You must log in or register to reply here.
Top Bottom