Playing with the Fisher St-828's - Home Theater Forum and Systems - HomeTheaterShack.com

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post #1 of 30 Old 10-02-09, 10:54 AM Thread Starter
John
 
Join Date: Sep 2009
Location: mississippi
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Playing with the Fisher St-828's

Ok the drivers and crossovers are all messed up in these ..The 15 inch woofers appear to be in good shape as does everything else they just sound awful.. So I did som enclosure calculations on this three way box , it has enclosed mids and tweets that take up hardly no space in the enclosure .. The enclosure in cubic feet is 2.648 ft≥.. So the port in these is 5 inches long by 2 inches round.. So I did some calc's and came up with a low freq somewhere in the neighborhood of 23-24hz.. Wow..My only problem is the crossovers that were in these do not work .. .. So I am lookin at replacing the tweets , the mids and I guess the woofers.. Biggest thing that gets me about the 15 inch fisher woofers is with a real bassy song they produce great bass but they barely move.. I guess if i replace the woofers I will get better sound because these speakers are at least 25 years old.. I got them at a garge sale years ago for 12.00 for the pair.. They are 27 inches tall , 17 inches wide , and 13 inches deep.. 8Ω
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post #2 of 30 Old 10-02-09, 12:14 PM Thread Starter
John
 
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Re: Playing with the Fisher St-828's

Here are some crossover ideas if i build my own.. What was normal for the speakers that were in the cabinet was 1.5 - 6 khz... So I used the calc for first order , and fourth order .. Not to sure but 1st order has no gain and 4th order has a 2.99db gain but it will be a monstor to build
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post #3 of 30 Old 10-02-09, 12:16 PM Thread Starter
John
 
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Re: Playing with the Fisher St-828's

http://www.diyaudioandvideo.com/Calculator/APCXOver/

This is the calculator I used

Capacitors
C1 = 3.31 uF
C2 = 29.88 uF
Inductors
L1 = 0.19 mH
L2 = 1.7 mH


750 to 6000 here
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post #4 of 30 Old 10-02-09, 12:29 PM Thread Starter
John
 
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Re: Playing with the Fisher St-828's

Here is a humdinger 4th order 2.99db gain

Parts List

--------------------------------------------------------------------------------
Capacitors
C1 = 1.77 uF
C2 = 3.51 uF
C3 = 22.24 uF
C4 = 31.42 uF
C5 = 4.71 uF
C6 = 1.05 uF
C7 = 41.92 uF
C8 = 9.48 uF
Inductors
L1 = 0.13 mH
L2 = 0.59 mH
L3 = 0.84 mH
L4 = 4.8 mH
L5 = 0.39 mH
L6 = 0.18 mH
L7 = 3.18 mH
L8 = 1.6 mH

4th Order Normal Polarity

6000 Hertz / 750 Hertz

8 Ohm Tweeter / 8 Ohm Mid / 8 Ohm Woofer
2.84 db Bandpass Gain, Spread = 8 : 3 octaves
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post #5 of 30 Old 10-02-09, 10:28 PM Thread Starter
John
 
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Re: Playing with the Fisher St-828's

Ok this looks like the verdict .. I am going to build my crossovers.. Getting the goods from madisound.. I figured it out on a sheet of paper but the photo shows the idea .. Total cost for mid line caps and inductors is about 23.20 per ( Speaker ) Crossover so 46.40 for the pair..

I just hope I picked out the right types Went air on the Inductors and poly on the caps....
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post #6 of 30 Old 10-02-09, 10:34 PM Thread Starter
John
 
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Re: Playing with the Fisher St-828's

Cost per each and speaker size
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post #7 of 30 Old 10-03-09, 09:40 PM Thread Starter
John
 
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Re: Playing with the Fisher St-828's

Is it just me are did Caps and Inductors really jump in price .. Just doing some figuring for a 3 way crossover .. ( 1ST ORDER ) I am looking at 18.00 a 3rd order Normal somewhere in the neighborhood of 40.00 per each ... I am seriously considering these

http://www.parts-express.com/pe/show...473751#reviews
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post #8 of 30 Old 10-05-09, 09:54 PM Thread Starter
John
 
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Re: Playing with the Fisher St-828's

Found some crossovers 800/5000 I ordered them .. 3 way...

Found some nice 3 inch tweeters polycell , just like my center channel has

and polk audio 5 inch closed back midrange.. Will finish these next week
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post #9 of 30 Old 10-06-09, 07:00 AM Thread Starter
John
 
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Re: Playing with the Fisher St-828's

I am debating as to what to do with the front setup...First I thought about building a shelf system around the big screen tv.. But that was sort of shot down by the wife.. I think she sai we dont need anymore clutter in the den..So then I thought maybe build some tall and less wide front speakers .. My biggest problem is the width of the room . My right channel front is just fine but my left channel front is almost behind the couch..and the sub is right on the floor too.. bothe behind the side of the couch..
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post #10 of 30 Old 10-07-09, 03:50 AM
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Quote:
the_diyr wrote: View Post
I am debating as to what to do with the front setup...First I thought about building a shelf system around the big screen tv.. But that was sort of shot down by the wife.. I think she sai we dont need anymore clutter in the den..So then I thought maybe build some tall and less wide front speakers .. My biggest problem is the width of the room . My right channel front is just fine but my left channel front is almost behind the couch..and the sub is right on the floor too.. bothe behind the side of the couch..
I haven't had time to look in much around here lately, so I just saw this thread. I'm confused at what you're trying to accomplish at this point.
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