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Old 27th September 2012, 12:49 PM   #1
Vix is offline Vix  Yugoslavia
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Default Quick 'n fast- F.A.S.T

Hi,

As I am using open baffle as a main system (see last pic), some of the past projects, some still working, some scrapped, ended half way between the living room and the trash bin..they reside in the "man cave", i.e., basement. While I was doing some tidying of the basement, it occurred to me that I have just enough parts , that, put together, can make a nice test rig, without disturbing others...
One of the things that always intrigued me was a FAST loudspeaker system, but I wasn't quite prepared to spend cash, partly because I am still happy with the Open baffle and associated electronics while it is still allowed in the living room .

So, the basement components gave a good ground to try some things out, just for fun of it...

The amp that you see on top is a S.E.W.A amp, with halogen sticks as a current source.
SEWA - Seven Watt Amplifier

Below is the preamp, Pass labs Bride of Zen preamp, and the old CD player...

Bass speakers enclosure is a "leftover" from my previous speakers M.J. King ML-TL with Fostex 206.... (see pic) .
Fostex is no longer there, but the enclosure was still in the basement, so I bought some cheap 8" drivers. No parameters available, neither I was ready to spend time measuring. Just quick'n dirty pop em' there. Crossover is comprised of a single air coil, must have somewhere around 2.5 mH....
For the top, I used some 4" Sony car speakers mounted in a cardboard tube (being an omni in the sort of ML-TL's -worked quite nice by themselves in the office until my boss ordered their removal). Now I relieved them from the bottom end, by a series cap. Tried values from 68-100 uF (this is a 4 ohm speaker).

I was truly surprised at how good such a (s)crap system can sound...
These days I am planning to do some more experimenting with various FR's on top, in various boxes (or no boxes)....
Attached Images
File Type: jpg ML_TL.jpg (137.8 KB, 742 views)
File Type: jpg 2012-09-26 19.30.17.jpg (92.0 KB, 729 views)
File Type: jpg 2012-09-26 19.29.53.jpg (99.1 KB, 714 views)
File Type: jpg 2012-09-26 19.29.32.jpg (87.2 KB, 709 views)
File Type: jpg 2012-09-26 19.32.46.jpg (77.3 KB, 707 views)
File Type: jpg 2012-09-25 22.05.40.jpg (91.8 KB, 247 views)
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Old 27th September 2012, 12:53 PM   #2
Vix is offline Vix  Yugoslavia
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One more pic (sorry for a poor quality...)
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Old 2nd October 2012, 11:22 AM   #3
philipc is offline philipc  South Africa
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Good to see all the 'recycling' going on
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Old 2nd October 2012, 01:44 PM   #4
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I'm continually surprised that the FAST system gets so little attention - there is such an ease to get really good results this way, particularly with the availability of reasonably priced good quality amplifiers to use as high pass and low pass amps with passive or the active electronic Xovers.
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Old 2nd October 2012, 06:24 PM   #5
Vix is offline Vix  Yugoslavia
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Moreover, tuens out that a decent 8" midwoofer in an ML-TL can go low enough. On the other hand, it has enough span to be crossed at around 400-500 hz first order. At such xo frequency, one can mount a fullrange of choice, without the need to do bass frequencies. When even such crappy speakers can manage to sound good, I can only imagine how would some nice 8" Peerles driver in an properly designed ML-TL do, with an Alpair 7.3 on top...
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Old 2nd October 2012, 07:59 PM   #6
GM is offline GM  United States
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Quote:
Originally Posted by jameshillj View Post
I'm continually surprised that the FAST system gets so little attention - there is such an ease to get really good results this way, particularly with the availability of reasonably priced good quality amplifiers to use as high pass and low pass amps with passive or the active electronic Xovers.
Yeah, this is what the pioneers of audio deemed a good use of wide BW drivers once the source material had enough BW to justify more than one driver, or speaker, if the original was a large horn.

I've been touting them as long as I've been on line, but as you noted, it's only been recently with the advent of low noise DSP, chip amps that folks have begun to embrace them.

GM
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Old 2nd October 2012, 08:19 PM   #7
GM is offline GM  United States
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Quote:
Originally Posted by Vix View Post
Moreover, tuens out that a decent 8" midwoofer in an ML-TL can go low enough. On the other hand, it has enough span to be crossed at around 400-500 hz first order. At such xo frequency, one can mount a fullrange of choice, without the need to do bass frequencies. When even such crappy speakers can manage to sound good, I can only imagine how would some nice 8" Peerles driver in an properly designed ML-TL do, with an Alpair 7.3 on top...
Correct, all my early TL, tower [MLTL] speakers for others were 8"-12" wide BW drivers mated to 2"-4" paper [mid]tweeters 'rescued' from old radios, consoles, TVs with them hooked the same as originally, i.e. the woofer run full range and just a cap on the HF, with 2.2 uF being the most common. Even did a few 15" variants for party apps.

I seriously doubt such simple designs would pass muster with today's much more discerning DIYer, but to the '60s-'70s youngsters they did AM/FM, vinyl, eight track tape and even Quadraphonic just fine, thank you very much .

GM
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Old 9th October 2012, 11:38 AM   #8
Vix is offline Vix  Yugoslavia
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I did some more testing and playing with cheap drivers..definitely a concept worth pursuing and doing properly, with "real" drivers...

Here's a link with some photos (along with some other DIY projects)...

https://www.dropbox.com/sh/zuqip6428gh1m6s/Sgs_77A7l0#/
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Old 9th October 2012, 01:42 PM   #9
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The FAST system is all about using a really good driver/amp combination specifically for bass and the FR driver/amp selected for the tonal balance to suit your own personal taste & music.

The Xover point for the Fast is about 120 - 150Hz so it isn't just another 2way speaker system - by it's designation, it simple removes the difficult job for the FR driver to try to reproduce the bass freqs.

There have been quite a few very successful matched Fast systems over the years and a search will show the benefits & difficulties of most of the selections - unfortunately, there is a certain ignorance about the combination of amplifier/driver benefits but the best results seem to be when the bass driver efficiency matches that of the FR driver so this usually precludes the use of the smaller dia bass drivers even with DSP freq assistance - it's hard enough to get the Linkwitz Transform/B2 alignment working "properly"

There are quite a few High efficiency FR drivers now on the retail market at quite resonable prices - I suggest you purchase good quality drivers, even when just trying the idea out as you can always onsell good drivers if not suitable.
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Old 9th October 2012, 02:11 PM   #10
zman01 is offline zman01  Bangladesh
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JH,

You're right about FAST - if properly set up can punch way above its weight class in terms of money spent and effort put in. I think what puts lof of people off is:

1. 2nd amp - what to buy? If you are driving subs definitely something with watts. I've found cheap Class D very handy

2. XO - how and with what - this is a major one IMHO.I've done with Foobar ASIO plug-in, but then that setting does not work for other Windows programs, right...? Maybe MiniDSP can be a quick and easy solution here? Then comes XO frequency....

3. Driver matching, building a sub - there are many drivers/designs available - but again, more research and building. Another apprehension - will the sub be able to pla high enough for XO to be workable at desired SPL? Will the FR unit be able to play loud enough w/o distortion down to that XO level?

Well helper "woofers" can be used too and should not have problems reaching higher XO frequencies vs subs.

Last edited by zman01; 9th October 2012 at 02:14 PM.
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