Playing with the Fisher St-828's

26479 Views 29 Replies 5 Participants Last post by Yad, Oct 19, 2009

the_diyr

Discussion Starter · Oct 2, 2009

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 ft³.. 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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the_diyr

Discussion Starter · #2 · Oct 2, 2009

3

:dontknow: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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the_diyr

Discussion Starter · #3 · Oct 2, 2009

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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the_diyr

Discussion Starter · #4 · Oct 2, 2009

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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the_diyr

Discussion Starter · #5 · Oct 3, 2009

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..:yikes::clap:

I just hope I picked out the right types Went air on the Inductors and poly on the caps....

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the_diyr

Discussion Starter · #6 · Oct 3, 2009

Cost per each and speaker size

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the_diyr

Discussion Starter · #7 · Oct 4, 2009

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/sho...w=1&&vReviewPage=2&vReviewRand=473751#reviews

the_diyr

Discussion Starter · #8 · Oct 6, 2009

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

the_diyr

Discussion Starter · #9 · Oct 6, 2009

2

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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JCD

· #10 · Oct 7, 2009

the_diyr said:
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.
Posted via Mobile Device

the_diyr

Discussion Starter · #11 · Oct 14, 2009

Ok I have the crossovers on the way for the ST-828's that merely came with a junk setup for the actual crossover network.. The 15 inch woofers are in good shape even thought they are ugly as .. Now the mids and tweets are all screwy one speakear has the original tweeter and midrange and the other has a slightly smaller tweeter and a slightly larger midrange that was rigged up in the cabinet before I got them.. So I need tweets and mids both closed back design.. Just dont have the cash to get good tweets and mids now .. So I guess i should wait to put the crossovers in..

evilskillit

· #12 · Oct 14, 2009

Best of luck, let us know how it works out. I tried to restore a pair of old Galaxy TS80s that had rotted surrounds on the 12" woofers and the passive radiators on the back had completely fallen off.

Never could get them to sound good. Knowing what I know now I probably could get something going, however I pulled the new 12s back out and put them in something else. At least it wasn't a total waste

the_diyr

Discussion Starter · #13 · Oct 14, 2009

yep I thought about buying ne speakers for the front but most of the new stuff is overpriced plastic junk. I went to best buy and asked the store manager if they had any floorstanding speakers that were made out of real wood .. He laughed and said I dont think they ever made speakers out of real wood... If I cant get the Fisher speakers like I want them I will probably build my own new ones.. I did listen to a few sets of cheaper floor speakers and nothing really struck me as too the type of sound that I wanted.. I even listened to bose at a dealer in town and at very low volume they sound good but when you turn it up it sounds like my grandmothers old am transistor radio... I always knew bose was for old people who didn't know what sound quality was.. Well I think the crossovers will be here today I hope.. And I think the surround repairs for the RSVIDEO center channel will be here tommorrow

the_diyr

Discussion Starter · #14 · Oct 14, 2009

Ok I ordered some soft dome tweeters for the fisher's to match what is in the RSVIDEO center channel .. Fluid cooled soft domes... I hate waiting on stuff to show up in the snail mail..

1Michael

· #15 · Oct 14, 2009

Crossovers have to be designed and tested with the specific drivers that are going to be used in a particular box. It kind of looks like your throwing some drivers and crossover parts together in the hopes that it will work out? Or am I missing something?

the_diyr

Discussion Starter · #16 · Oct 14, 2009

Pretty close but I ordered th Cerwin Vega crossovers .. I used a crossover calculator , volume calc is right on the money .. Using CV tweets CV Mids and CV woofers.. The 15 inch woofers are CV's from an old set of speakers.. The cabinet size is perfect for the drivers.. the tweets are closed back , the mids are closed back.. the crossovers are the same specs as what is on the fron of the fisher cabinet

a modest 1.2 -6.0 khz

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the_diyr

Discussion Starter · #17 · Oct 14, 2009

I noticed on all the speakers that are mounted in the ST828's there is no seal.. They are all just mounted to the wood.. I was thinking when I put all the drivers back in i am going to use some rope caulk or something to really seal the speakers good .. I used this on my custom under the seat sub box I installed in my crewcab and it makes a good seal..

evilskillit

· #18 · Oct 15, 2009

Bleh to rope caulk. It works great but not if you ever want to get the drivers back out without destroying them or the box. I bought the Dayton BR-S1 kit, which came with rope caulk. After putting them together I wanted to double check the crossovers to make sure there were no problems, but even after shoving a broom handle through the back and pressing on the back of the driver about as hard as I dared to, I could not get it out. Fortunately I think I got everything right, after they broke in they sounded pretty good. But had I not I would probably be screwed.

On my next build I just put a small bead of silicon, smoothed it with my finger and let it dry, it made a nice rubbery seal. Weather stripping tape works well also from what I hear.

JCD

· #19 · Oct 15, 2009

This is my preference..

Creates an airtight seal and helps to isolate the driver from the box to some extent. And is MUCH cleaner and easier to install. And it's relatively cheap.

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the_diyr

Discussion Starter · #20 · Oct 15, 2009

Closed cell foam tape is a good idea .. On the silicone thing I heard that it might hurt your surround foam from the fumes .. not sure though.

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