[jonwb]

OK, here is one idea...



Its sort of a further development of what I posted on the other thread.  If you want to look at it in 3D I also saved it as a VRML file.  Its located here:

http://www.geocities.com/jonwb/alpha_center_concept/center_a.wrl

If you need a VRML viewer there are many out there.  I'm using "Cosmo Viewer".  You can download it here

It is sort of a beast.  I haven't yet calculated the volume.  I figure I can adjust the volume by changing the depth.  You can see the basic outside dimensions here:

http://www.geocities.com/jonwb/alpha_center_concept/alpha_center_concept.pdf

As usual, if you want to look a my "geocities" links you need to cut & paste the URL into another Window.

[JoshK]

that looks really cool!

[mgalusha]

Very cool idea. I was at the movies this weekend and it made me think about having a center channel that was physically wider so the dialog wouldn't be tied so much to the center of my screen (I have a projector setup).  This looks like just the ticket. Now if Danny can just design a cross over for it, not that he has any extra time.

[Danny Richie]

Hey, testing, measuring, and designing the crossover is no problem and does not take a lot of time.

What I do not have time for is building the boxes.

[azryan]

"- I was at the movies this weekend and it made me think about having a center channel that was physically wider so the dialog wouldn't be tied so much to the center of my screen (I have a projector setup).-"

That's exactly what a phantom center is like.
I've got my Alphas 9' apart and it's one huge solid sheet of audio.

I've heard SO many little horizontal center chans. that collapse most of the soundstage into it's tiny, mostly vertical dispersion.

Just the nature of how a horiz. center throws sound and how much 'stuff' is typically recorded in the center channel.

I still think I don't need one at all, but this large and curved Alpha center seems much better and giving me the best of Phantom and 'actual' center chan.

I might do it for the fun of building and 'just 'cuz'.

It was REALLY funny way back when I had a 32" TV and first went from an actual center to a phantom center w/ my Newform 630's (and later 645's). The sound stage was awesome and perfect for a LARGER screen, but didn't match my small tv.

[jonwb]

Anyone tried pulling up the VRML file and spinning it?  That way you can see the bracing and stuff a little better.  Pretty cool actually.  

I'm in the midst of trying to calculate the volume.  First crack at it didn't "take" (I screwed it all up).  Now I'm setting up a spreadsheet.  I'm thinking the volume is way too big as it currently sits.  If I'm figuring correcly on weight, I think its approaching 70lbs.

I'd don't have so much a problem building the box (especially in raw MDF).  Its the cost of all those drivers and cross-over bits that'll get me in trouble.

... and when I show "her" the size the box would be...  

[mgalusha]

azryan,

I ran my system that way for a while but the issue for me is that my HT system is seperate from the stereo and I don't sit on center so the phamtom center doesn't work too well in my setup. With the chairs re-arranged it works very well and I don't feel the need for a center channel but my wife didn't much care for having her chair pushed way off to the left.

Danny,

Nice to know you can kick out a cross over. Maybe we can lobby jonwb to build a prototype box for you to play with.  Hmm... a question Danny, if this were to use the same drivers as the Alpha would the cross over be similar enough to guess-timate for those of us who could build a box and order up the goodies from you? Or would it be different enough to require a new XO design? Thanks for your time.

Mike G.

[Danny Richie]

Jonwb,

You can push the box volume out to 1.0 cubic feet or more with these and still be fine (hear that Ryan?).

It's a smaller .606 Qtc. Power handling (mechanical) shouldn't be an issue in the larger box.

The EBS type alignment of the Alpha LS has them in a ported box nearly twice the size of the optimal.

The sealed box design will be even less fussy about size using that many drivers.

Hmm... a question Danny, if this were to use the same drivers as the Alpha would the cross over be similar enough to guess-timate for those of us who could build a box and order up the goodies from you?

I'm really not to big on making about guess-timations. I am a bit of a perfectionist.

And yes it does not take me long to tweak out a network. I have all the tools and a big inventory of parts handy.

[mgalusha]

yone tried pulling up the VRML file and spinning it? That way you can see the bracing and stuff a little better. Pretty cool actually.

That is pretty cool. I had to fool Cosmo into installing as I'm using Mozilla Firefox and the plug in needed to find netscape.exe to install. I't didn't seem to care that it was zero bytes.

What did you create the drawing with? Just curious.

Jonwb,
I'm really not to big on making about guess-timations. I am a bit of a perfectionist.

That's always good to hear. I rather suspected that after hearing your speakers (a friend has the Diluceo's).  

Thanks for the info.

Mike G.

[scooter]

Jonwb,

You can push the box volume out to 1.0 cubic feet or more with these and still be fine (hear that Ryan?).

It's a smaller .606 Qtc. Power handling (mechanical) shouldn't be an issue in the larger box.

The EBS type alignment of the Alpha LS has them in a ported box nearly twice the size of the optimal.

The sealed box design will be even less fussy about size using that many drivers.

I'm really not to big on making about guess-timations. I am a bit of a perfectionist.

And yes it does  ...

Danny,

Would it make a better overall center if the driver complement was doubled i.e. 10 Woofers and 10 Neos.

I also love the design and am considering building it.

[azryan]

Holy CRAP! 10 neos and 10 woofers???

You serious 'scooter'?

That's larger than the actual Alphas!

The curved design seems better to me personally.

The best would probably be a third Alpha tipped vertical behind a acousticaly trans. screen, but w/ the spread of a 6 woofers and neos (if I do it I'm not going to put the 6th woofer and neo at the rear like jon looks like he's going to do) it should do what it's supose to do and I don't see any advantage to 'more' drivers.

Danny,

Where's that email? Do you have my earthlink address? Thanks man.

[Danny Richie]

Would it make a better overall center if the driver complement was doubled i.e. 10 Woofers and 10 Neos.

A curved array of 6 and 6 is as large as I would make it with all 6 being in the front of the curved array.

That is actually plenty big, and gives a 100 degree coverage area if each is turned 20 degrees.

Where's that email? Do you have my earthlink address? Thanks man.

It went to your ignmail address.

What is your other one?

[scooter]

Holy CRAP! 10 neos and 10 woofers???

You serious 'scooter'?

I am nearly at the point where we will be moving house and I am trying to see how big a room I am going to build. I am aiming for 20 x 30 ft room hopefyully. With that size room I would look for a 12 ft width screen so a large long chorizontal enter would not really be out of place. The options I have are to use a verical Alpha or build the center channel version. I have never heard a very long center channel so I am not sure which will provide the best performance around the room, maybe Danny would like to comment as I can do it vertically as I will be using a sound transparent screen.

This will probably be like my last theater, in total it took me over 186 months to build, it is my only hobby and only passion (aside from my family)

[scooter]

Before you say it, it was 18 months not 186 months.

[azryan]

OK...

Spent some time working on plans for an Alpha center.

I don't have a fancy CG modeling program but I have a pencil, a ruler, my wife's protractor from grade school, AND a sheet of lined paper. hehe

After I thought I knew what I wanted, I drew the top view on my kitchen countertop to get an idea of it 'life sized' too!
My wife wasn't too thrilled with that. hehe
It's pencil on formica I told her... It'll wash off. hehe

Here's a link to my notes. Yes.. they're totally messy as if written by a small demented child.

http://home.earthlink.net/~azstrehlow/alphacenter.html

So Danny.... does this seem ok?

I think six 10 degree sections will work perfectly. That's a 60 degree spread -right? 10 degrees times 6?

From ~13' away from the center face it looks like it'll cover a 17.5' width (which happens to be my room's width).
Even from a much closer distance of ~8' it looks like it'll cover a 13' width.

If I didn't screw that calculation up (tell me if I did) I see no need to make it 15 or 20 degrees per section. I'm figuring the closer to flat I can keep it the better too.

scooter, do you think this would hit where you intend to have seats? I see your room size posted, but not seating.

I'm not 100% sure about the cabinet depth but it looks like .635 cu. ft. is REALLY small so my only concern of depth seems to be having enough space behind the two end woofers.

I'm looking at 2.5" deep on the inside side walls. The depth from the inside center to inside back looks like it'll then be about 10".

Double thick side and back walls. Probably stick with single .75" MDF top and bottom w/ vertical bracing probably a few wood dowels since they're rounded and easy to cut and stick in.

It looks like if I put a .75" solid sheet to sepp. woofers and neos then I'll have a sealed woofer volume of about 1 cu. ft. minus woofer magnets, x-over parts, damping stuff.

I thought damping mat. makes the cabinet 'look' bigger to the woofers though so I might have to fill up the cabinet further??

I'm thinking I can just fill up the whole neo cavity w/ damping?

Will that work fine or do I have to actually put the neos in a much shallower volume like in the Alphas?

If the solid woofer/neo sep. sheet will work I'm thinking 3 dowels behind the 1st and 2nd, 3rd and 4th, and 5th and 6th face segments and 2 dowels in the rear corners will hold up that sheet, plus glueing the sheet in good too (liquid nails to make sure it's totally sealed).

I'll also put some dowels between near the center to brace things or maybe a rounded corner MDF sheet w/ some holes in it, but not the whole width of the speaker fearing it'll be too close to the end woofers.

Looks like overall it'll be 12.25" tall (same as the Alpha's width), ~44.5" wide, and 12.25" deep (at the center of the face to the back).

I already cut the double thick back sheets to the right height but to have to wait till I actually
cut the face segments to be sure of the exact back width.

I've got the double thick face sheet glued up and drying. Later I'll cut the segments to a width of ~7 15/16" and then angle all the sides back 10 degrees -'cept the left edge of the 1st segment and the right edge of the 6th segment (if that makes sense?).

'IF' this all works out right I'll be able to post a good cut sheet drawing and exact measurments for everything but the numbers on the my messy drawing I think are at least pretty close to 'right'.

This should only take one full sheet of 4' x 8' MDF, so about $20.

To hide it below my RPTV screen (center sound better IMO under a screen rather than above even when both are aimed directly at the listener), I'm not going to veneer it like I did my Alpha mains.

I'll do it in a matte black to match the drivers. Should be pretty danm invisible for such a HUGE center chan.

Questions?

Comments?

Wild laughing?

[wshuff]

I'm going to go with wild laughing until you start cutting MDF, then I'll ask questions and offer comments.  So...get to work!  And post pictures.  

[azryan]

I have already started cutting MDF (it says that in my previous post).

On Sun. I cut the 2 layers for the back section to the right height, but have to wait to get the exact length.

I also cut the two sheets for the face sections and glued them together.

Just a few hours work in the afternoon.

On Mon. I cut the inset for the neo line, rounded the top and bottom edge, then cut apart the face sections.

Then I cut neo holes out for each section (you just cut one long slot for the Alpha mains but for the center I think I need to have sep. holes so I can glue full solid edges together).

Then I cut the 10 degree angles on all the sections 'cept the left edge of the 1st section and the right edge of the 6th section.

Those angle cuts sucked to do. I really needed someone to hold the MDF while I was cutting. A table saw would have been a lot nicer but oh well my circular saw worked ok I think.

I already stood them up and looked at the curve and it looks really slick. You can already see what it'll pretty much look like when it's done.

Should be plenty wide coverage from 10 degree cuts IMO.

Just hope to have Danny confirm that my volume looks ok and the space behind the end woofers will be enough and space for the damping.

I can then finish the whole thing in another day or two tops (plus glue drying time).

It won't be any trouble to adjust how deep it'll be. The face and back'll stay the same.

Not bad for $20 of MDF. I mostly used scrap I had too.

Send me a digital cam and I'll take pics for you. hehe

[azryan]

Oh,

And wshuff,

it looks like your center speaker is upsidedown.

I'm guessing your x-over is glued to the top of your speaker as you've got it in your pic.
probably won't cause any prob. but just thought I'd warn you.

[wshuff]

I'd send you the camera but since it was actually the wife's Christmas present, she may not like it.  Of course, we have our meeting with the Bureau of Citizenship and Immigration Services tomorrow, so if they don't like her, I'm keeping the camera and I'll send it to you.  Hell, I might even hand deliver it since I'll be single and alone again.

As for the center channel, I'd never paid attention, but I think you are right.  That's probably why all the dialogue seems backwards.  It's upside down!

I'll have to crawl up there and flip it over.  Thanks!

[azryan]

I only point out the 'upside-down' center 'cuz it means your x-over parts are hanging upside-down inside the cabinet which probably doesn't matter, but thought 'just in case' you might want to flip it over.

You can put the neo panel in either way so it might not be upside-down, but unless you looked inside I'd bet it is.