Wanted: Comments & Suggestions on this My First Speaker Project

bluesarebest

bluesarebest

Audiophyte
Wanted: Comments & Suggestions on this My First Speaker Project

My objective here is to build a pair of home theater speakers to flank my 36” flat screen. To drive my new speakers, I currently have a JVC Audio/Video Receiver RX-8030VBK (6 X 130W per channel) The amp has several digital optical inputs that can be
hooked up to the soundcard of my home computer which manages a very large collection of MP3 files.

My box size calculations came from quick study of some web sites and forums. Since math is not a strong point with me, please
take a look at my “guess work” and holler, NO YOU IDIOT! If you care to take the time to give advice to me, please keep in mind that unlike most of you, I have limited knowledge when it comes to Thiele-Small data and it’s affect on drivers and their output performance. Some of you are sure to say I’m building the boxes a bit large, but I did this for future upgrades to 10” woofers (don’t want to build new cabinets). You also need to know some info about room size and listening preferences.

Folks at my house never listen to REALLY LOUD music. We enjoy 4 to 5 DVD movies each week, and music plays during times the TV is not being watched. Our “Theater” room measures 26 X 12 with the TV screen backed up to the middle of one of the long walls, the floor is finished wood on a pier & beam foundation.

I’ve listed the products I’ve picked out to suite my meager budget and these are all I can afford at this time. I know there is better quality stuff out there, but I still have to put two more brats through college soon. I’m always asking my wife, “who wanted all these d$#n kids anyway”?

Budget $300 each speaker.

2 - GOLDWOOD GW-8PC-30-8 8" HEAVY DUTY WOOFER 8 OHM $40 ea.
SPECS: 120 watts RMS/230 watts max, Voice coil diameter: 1-1/2", Le: .99 mH, Freq. response: 45-7,000 Hz, Re: 7.24 ohms,
Magnet weight: 30 oz, Fs: 55 Hz, SPL: 88 dB 2.83W/1m, Vas: .51 cu. Ft, Qms: 4.2, Qes: .62, Qts: .56, Xmax: 3.21mm

2 - EMINENCE LA6-CBMR 6-1/2" SEALED BACK MID RANGE $75 ea.
SPECS: 150 watts RMS, VCdia: 1.5", Le: 0.33 mH, Impedance: 8 ohms, Re: 6.3 ohms, Freq. range: 500-5,000 Hz, Magnet weight: 38 oz, Fs: 460 Hz, SPL: 98 dB, Vas: 0.013 cu. Ft, Qms: 3.13, Qes: 1.24, Qts: .89, Xmax: 0.2 m

2 - VIFA XT25SC30-04 SHIELDED DUAL CONCENTRIC DOME TWEETER $80 ea.
SPECS: 100 watts RMS/140 watts max, Znom: 4 ohms, Re: 3.0 ohms, Freq. range: 1,500-40,000 Hz, Magnet weight: 8.5 oz,
Fs: 500 Hz, SPL: 91.5 dB 2.83V/1m

2 – CROSSOVERS (Parts Express #260-231) $40 ea.
SPECS: The woofer section rolls off 6 dB at 800 Hz while the tweeter section uses a 12 dB per octave roll off at 4,500 Hz. The midrange section uses a true band pass filter with a response of 750-5,000 Hz. 12 dB per octave roll off. All crossover frequencies are rated into an 8 ohm load

2 - DAYTON AUDIO GOLD BINDING POST PAIR (Parts Express #091-1245) $15
SPECS: The binding posts can be used with banana plugs or will accept wire up to 8 gauge. Extra long rear bolt (1-1/2”) for mounting in speaker cabinets with walls up to 1” thick. Overall length is 2-1/4”. Sold in color coded pairs with solder tabs.

2 – ACOUSTA-STUF POLYFILL 1 LB. BAG $20


1 - 4’ X 8’ X ¾” Medium Density Fiberboard $38


Box inside dimensions of 25”H X 15”W X 12”D gives a volume of 2.6 cubic feet leaving a bit over 500 cubic inches
to be taken up by wood bracing and the speakers. Port 3” X 6.25

This is my first post, Thanks for your time. BluesAreBest
 
JoeE SP9

JoeE SP9

Senior Audioholic
Have you considered buying a pair of used speakers. For $300 per speaker you can get some mighty impressive stuff. My audio bud Mr.T just bought a pair of Magneplaner MG2's for $300 the pair. We rode from Phila. to Queens Long Island in his truck to pick them up. We did see a Lamborghini Diablo on the Jersey pike so the trip was not totally unpleasant. The Maggies are near mint and sound absolutly wonderful.
 
Rip Van Woofer

Rip Van Woofer

Audioholic General
You might get more responses in the DIY Corner. Hey, I'm a moderator, I'm s'posed to point that stuff out! Anyway...

Since this is your first DIY speaker project and math is not your strong suit, and if you haven't already bought the drivers, do what I did (since that sounds exactly like me!): find some good speaker plans where someone has already done the heavy thinking for you and you just have to follow directions. I think you might be in for considerable frustration if you try to bite off the challenge of designing your own speakers right off the bat. There's a lot more to it than you can learn with a "quick study of Web sites and forums". With a bit more searching and maybe buying a book or two you can find plans for a system that will fit your needs. You can learn a lot that way and greatly improve the odds of ending up with an excellent system. I did!

Or try one of the Parts Express kits.

And IMO, 6db/oct. "first order" crossovers are very problematic. I think that 12db/octave to 24db/oct. Linkwitz-Riley crossovers are the best. But this is a contentious area! (ok, first-order fanatics...fire away! :D )

If you don't know what "Linkwitz-Riley" or "first order" mean, that's another sign that you should think twice about doing your own design. ;)

See my DIY speakers here . :)
 
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bluesarebest

bluesarebest

Audiophyte
Thanks JoeE & Rip!
Please fell free to move this post to wherever you see fit, I am after all a beginner, so I was not sure where to post :)

Both of you make very fine suggestions, but I've given this a lot of consideration. I want to do this DIY. Y'all started somewhere right? I've never in my life put together anything I wasn't happy with, I work too hard for my money to waste it. If I wanted to make mistakes, I never would have asked for your opinions. I just would have ordered the stuff and built them.

Rip your absolutly right I have much to learn. But guide me, teach me, tell
me what is wrong with my drivers, suggest better ones. Give me little tips like the one about those paticular design of crossovers. My ignorance will only be temporary. My intent is to pick brains and get real comfortable with all of this long before anything gets purchased. My MP3 collection & CDs will wait for better speakers, many months if needed :rolleyes:

I have already ordered a copy of V. Dickason's Loudspeaker Design Cookbook form Barnes & Noble. Rest easy folks, bluesarebest is a grey haired old hippie who is still very laid back, and always, always, looks before leaping :)
 
Rip Van Woofer

Rip Van Woofer

Audioholic General
bluesarebest said:
Rip your absolutly right I have much to learn. But guide me, teach me, tell
me what is wrong with my drivers, suggest better ones.
I don't know. That's why I let better minds than mine do the designing! I'm not really into DIY speaker building and being an amateur speaker designer for it's own sake. And I'm not a techie - I was a music and theater major! For me DIY is just a means to an end: getting better sound than I could otherwise afford. For my speakers I went with a somewhat unconventional design by one of the best minds in audio who has seen fit to publish much of his wisdom gratis for the greater good. Even if open-baffle dipole speakers aren't for you, his site has a lot of good info (albeit very techy and math-intense at times). Link below.

Getting the book was a good step.

Siegfried Linkwitz's site

[EDIT] aaahh...now that I've had some breakfast and coffee here's a few other places to look if you haven't found them already:

Parts Express DIY Center

Elliot Sound DIY site

Speakerbuilder.net

Steve's Speaker Stuff site A good site by a keen amateur builder.

No doubt links on these sites will lead you to other good ones.

And a good basic electronics book is The TAB Electronics Guide to Understanding Electricity and Electronics, Second Edition by *. Randy Slone, McGraw Hill, publisher. (the first initial is "gee". I don't know why it gets replaced by an asterisk. Must be an obscure obscenity that has somehow escaped my notice)

That oughta keep you busy, you old hippie! :)
 
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jeffsg4mac

jeffsg4mac

Republican Poster Boy
Rip Van Woofer said:
And IMO, 6db/oct. "first order" crossovers are very problematic. I think that 12db/octave to 24db/oct. Linkwitz-Riley crossovers are the best. But this is a contentious area! (ok, first-order fanatics...fire away! :D )
Rip, you are correct, because I prefer 18db per ooctave slopes in a DiAppilito configuration. But hey thats just me :D
 
bluesarebest

bluesarebest

Audiophyte
Thanks Rip

I think I'm a little smarter today :) Thanks for the links. I've bookmarked
the sites and will visit them in-depth over time.
Have a small problem this morning if anyone can help. I'm going to post it in the HT section. Enjoy whats left of the weekend!
 
bluesarebest

bluesarebest

Audiophyte
Taking your advice

Rip, I've come to see your wisdom about designing my own speakers.
I've looked around and have decided to try to build a pair if the infamous Dayton III MTM's. they should fit my room very well.

I've already taken my measurements to my local cabinet maker.
I have a little furniture making experience, but never worked with MDF.
I went over to the local DIY warehouse to discover a sheet of 3/4" MDF is very heavy! Since my old worn out spine is not up to wrestling with a 4X8 sheet of MDF, my cabinet guy is going to make all the cuts for two boxes.

I checked Parts Express and they have all the items needed. There is however some kind of difference in the crossover design based on a change to the tweeter. If you, or anyone else knows which of these two crossovers work best with the "new" tweeter, please let me know. BTW, I was born and raised in Roseville ;)
 
Rip Van Woofer

Rip Van Woofer

Audioholic General
bluesarebest said:
BTW, I was born and raised in Roseville ;)
No way! I grew up there, too. RHS class of '71.

Don't have an answer to your crossover question. There's a forum on the Parts Express site in the DIY center where you could ask. Someone probably already has.
 
bluesarebest

bluesarebest

Audiophyte
Go Wildcats!

Yes way! :eek: I grew up in a subdivision just northwest of I-94 & 10 Mile Rd.
If that rings a bell with you, lets find out if we ever hung out as kids.

Thanks for the tip about the forum. I'll post there and see if I can get my question answered.
 
Rip Van Woofer

Rip Van Woofer

Audioholic General
I was just a couple of blocks north of Martin Rd. close to Groesbeck near the high school so we probably didn't. I was in the band in HS, played percussion. Drums were my life then!

Old RHS is now a junior high. Brablec is now Roseville-Brablec high school and the only high school. I seldom have reason to go thru Roseville any more except when I ride thru sometimes with the bicycle club I belong to. And haven't touched a drumstick in years...
 

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