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Old 7th December 2009, 08:21 PM   #1
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Default 2 stereo lm1875 amps, 4 speakers, and a bunch-o-other stuff

Warning this is a NEWBIE thread turn back now if you become frustrated easily.

About 6 months ago my cheap sherwood amp died when the power at my old apartment went haywire and took my dads old fisher speakers with it. Since then I've made do with $20 radio shack 2.1 computer speakers running off the on board audio of my computer. Now work doesn't start up for me again until april and I have a bit of extra cash that I was going to put towards a 100% perfectly legal closet grow room experiment but as I moved to a new place that has a land lord that actually cares what happens to the house this isn't going to happen. I've always wanted to dabble in DIY audio stuff and this seems like the perfect time since I have a ton of time until april.
Let me start off with what I currently have:
2x 8" Fostex fullrange drivers (no enclosures yet) http://www.madisound.com/catalog/PDF...ers/FE206E.pdf
1x Tymphany LAT250 (sealed enclosure, wired 4ohm/4ohm, from an abandoned project but it sounds really nice) http://www.madisound.com/catalog/PDF/LAT250-004.pdf
1x DAC for my computer (so I can hook it to an amp and never have to use these computer speakers again)
1x CD player
What I want:
2x lm1875 stereo amps (1 for the left and right fostex drivers and 1 for each of the LATs channels). I'm looking at the pcb kits from chipamp.com for these unless anyone has better suggestions
1x turntable (gonna find an old one on ebay, any suggestions on what to look for?)
1x phono preamp (need affordable kit suggestions)
An now for the complicated part I want to do an active cross over after the volume control but know nothing about them. I've see some kits but really don't know what I'm looking at. I also want to know if I'll have any problems with the "subs" (I wouldn't call the LAT250 a true sub but...) being 4ohms and the fostex being 8ohm (I already know that I'll need an L-pad on the fostexs to bring them in line SPL wise with the LAT). I also want to know if there is a way to incorperate a bass and treble control into this (I don't always have the best sources in the world but don't want the complexity of a full equalizer). I'd like to do this with kits and opamps if its even possible.
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Old 7th December 2009, 08:54 PM   #2
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Last question 1st... you will need a level control on each amplifier (or at least on the amplifier that needs turning down more (likely the Fostex one).

The 1875 amplifier is likely best for the Fostex, something beefier for the LAT (3875, 3886) for the LAT.

Hagermann makes a decent semi-kit for phono, a number of phono section projects have hit diyAudio just recently.

For TT i'd suggest a blet-drive. What kind of budget do you have (note that TTs need to be packed extra carefully and if off eBay you need to worry about this,

To my mind the 2 best enclosures for FE206 are likely Sachiko or Dallas II (with either of these you may find the LAT extraneous)

dave
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Old 8th December 2009, 02:48 AM   #3
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Chipamp 1875 is very good and simple. Low parts count. If you need bigger power, the 3886 is also very good. Recommended.
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Old 8th December 2009, 04:21 AM   #4
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Quote:
Last question 1st... you will need a level control on each amplifier (or at least on the amplifier that needs turning down more (likely the Fostex one).
Would that be something like an attenuator for each amp to get the SPL out put on each speaker the same along with a master volume control once everything is the same?

Quote:
The 1875 amplifier is likely best for the Fostex, something beefier for the LAT (3875, 3886) for the LAT.
So getting a stereo lm1875 kit and a stereo lm3866 kit would be a good idea? Would the stereo lm3866 be fine or should I do the dual mono (the way I built the speaker each voice coil is seperate and the way the binding posts are done connecting it so they are parallel or in series would be difficult. Its a very artsy enclosure)?

Quote:
For TT i'd suggest a blet-drive. What kind of budget do you have (note that TTs need to be packed extra carefully and if off eBay you need to worry about this,
I'm not gonna lie I'm a cheapo and don't listen to records too much. Really my record collection consists of jethro tull and mastodon (odd combo I know) along with a few other ones. Really the last TT I owned was a fisher direct drive with linear tracking. Works but needs a new stylus and its ugly as sin. Considering I pop about a few rounds off a day with my mosin I doubt my ears are good enough to tell the difference between a cheap TT and a $$$$$ TT. I'm open to a new one if theres a good one under $150. If I go used then >$50.

Quote:
To my mind the 2 best enclosures for FE206 are likely Sachiko or Dallas II (with either of these you may find the LAT extraneous)
Should have mention I'm building the enclosures myself. Actually since I like my sound tight (you know you just chuckled) and I was going to have the LAT handle the low freq. I figured I would build them sealed enclosures. I honestly don't like fullranges all on their own cept on open baffles which I don't have enough room for.
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Old 8th December 2009, 06:37 AM   #5
Atilla is offline Atilla  Norway
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Originally Posted by churchwarden View Post
Would that be something like an attenuator for each amp to get the SPL out put on each speaker the same along with a master volume control once everything is the same?.
Yes. It's like a balance control for your intended usage. You might want to have that.

Quote:
Originally Posted by churchwarden View Post
So getting a stereo lm1875 kit and a stereo lm3866 kit would be a good idea? Would the stereo lm3866 be fine or should I do the dual mono (the way I built the speaker each voice coil is seperate and the way the binding posts are done connecting it so they are parallel or in series would be difficult. Its a very artsy enclosure)?
If you want 1 sub output and 2 lower power speaker outputs, you could use one LM3886 for the sub and 2x LM1875 for the speakers. Good efficiency speakers won't require that much power to get to the levels that make your ears scream. Especially if the lower frequencies are handled by a separate amp/woofer combo. The active crossover before the chips will be important and you should read more about how to make them. The ESP Sound Projects and Linkwitz Labs pages should help you a fair bit, along with some reading on active filters. Just google them and look through those forums as well.

Quote:
Originally Posted by churchwarden View Post
Should have mention I'm building the enclosures myself. Actually since I like my sound tight (you know you just chuckled) and I was going to have the LAT handle the low freq. I figured I would build them sealed enclosures. I honestly don't like fullranges all on their own cept on open baffles which I don't have enough room for
Fair is fair, not everyone has the room acoustics for that ultimate "pure sound". If you get your power ratings and active crossover right, you should be able to have a very good output that will make you proud with your work.

Oh and if you're having a separate subwoofer enclosure, you might want to make it ported to reduce the size of the casing. It is more complicated, definitely, but tweaking your setup is part of the DIY spirit

Last edited by Atilla; 8th December 2009 at 06:41 AM.
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Old 8th December 2009, 08:05 AM   #6
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Quote:
Originally Posted by churchwarden View Post
Should have mention I'm building the enclosures myself. Actually since I like my sound tight (you know you just chuckled) and I was going to have the LAT handle the low freq. I figured I would build them sealed enclosures. I honestly don't like fullranges all on their own cept on open baffles which I don't have enough room for.
Most people here are building the enclosures themselves

How high do the LATs go? I just don't have a good feeling about how well they will integrate. Sealed you'd be crossing at 150 Hz and a really tiny enclosure.

dave
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Old 8th December 2009, 04:55 PM   #7
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The LAT is in a really tiny sealed enclosure. The entire point was having a small sub for a tiny *** room (large farm house, would be the babies room if not rented to 5 college age guys and their girl friends) and I chose the LAT250 since it was specifically designed for a ridiculously small enclosure. Can't remember the program I used to calculate the dimensions but even I was surprised by how small it had to be. I had to change the dimensions (kept the volume the same) a lot to have a surface big enough to mount it on. Last time I used it I think it was crossed over at 175hz and sounded fine (not the best sub in the world but I have heard FAR worse. The 18" woofers on my dads fishers come to mind, VERY BOOMY). I was think of crossing it at 150-200hz this time obviously experimenting a little to find what I liked best.
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Old 8th December 2009, 07:11 PM   #8
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Sorry for the double post but I couldn't figure out how to edit my previous one.

Firstly sorry for using MSpaint its what I have. This is what I'm thinking for the active crossover set up. Almost all of the kits I've seen are 4th order LR. I honestly don't really know what that means but it appears to be popular. I'm currently reading and trying to the best of my ability to understand ESP's Bi-Amp article and I'm leaning towards using the ESP P09 board for the active crossovers.

Basically this pic is what setup is going though my mind right now. Mainly I want to know whats right/wrong whats needed/unneeded. Note that when I say L + R in it I don't mean mixing the two signals. Its just that I got lazy and didn't want to draw two lines.
basicsetup.JPG
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Old 10th December 2009, 01:58 AM   #9
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LOL church what kind of mosin-nagant do you have? I have a Finish M39 1941 issue, all original equipment. Thing is a shoulder slammer. Not nearly as bad as the carbine models though.
Back on topic. I have always wanted to try one of those USB sound cards that do 5.1 and hide it in a receiver case. As small as computers are getting I could probably build something with an Nvidia ION chipset into it. Think about it. BR-drive, 5.1 sound, decent amps.. all in one box. Puts a smile on my face!
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Old 10th December 2009, 03:54 AM   #10
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A russian M91. REALLY OLD one according to 7.62x54r.net. No hand guards, no finger rest, no sling holes in the stock (sling goes on differently), no cross bolt, French made. The barrel has seen better days but its still good enough to hunt dear with (and shoot cans with). Unfortunatlly I don't have a matching bolt. Found it in my old aprt. bassement and the landlord sold it to me for $50 (Had no bolt, ejector/interuptor or trigger and was completely packed in grease so he though it was useless). Spent another $50 on parts and tada (whoever stored it didn't know what they were doing...stock is still ******* greasy...oozzes out on hot days). I bet this gun has a hell of a story to tell.

I wish I had waited for the ION. I have an Intel Atom 330 Mini-ITX and the onboard sound is HORRIBLE (k I bet most of it is the speakers but I digress). Still using various parts I've a accumulated over the years I got a desktop for $80.
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