DIY Super Center Channel

Early B.

ben62670 wrote: »

OK we are looking at 40hz to be able to pull off a reasonable box, and keep it tight. Some dampening will help with the drivers bump at 4k. It looks real nice nice so far.

Ben --

Is 40hz in a ported or sealed box?

I wanna go lower.

unc2701

Timbre matching aside, where do you plan to find source material that has 40hz info in the center channel?

The VAST majority of soundtracks have no material below about 80hz for the center channel and the algorithms to make a center channel out of a stereo source won't give you any sub-80hz info for most material. Hell, the Wilson Audio center only goes to 55hz for exactly this reason.

TNRabbit

I saw a pair of Klipsch KLF-30s modded into a huge@$$ center channel one time....wow.

VR3

The reason to go to 40hz is the same reason to go to 20hz...

Because you CAN!

Sick project Brad. Would love to hear it. I have always thought Centers are the most over priced pieces of poo on the market... so glad to see something real built.

ShinAce

I'm scared.

Firstly, the choice of drivers seems odd. You plan on crossing over an 8 inch woofer over 4KHz? Insane! There will be breakup modes heard. The crossover region will be harsh.

You need to find a way to drop the crossover lower, or change the woofer for something with an extended range.

Secondly, it sounds like you'll end up porting the woofers, but the goal is lots of punhcy bass to accompany a subwoofer that might be integrated to the system. Sounds strange to me.

Lastly, Zingo, 99 db!! Is that 2.83V/m but with 4 ohm drivers? Wanna share your design with me so I can nitpick. C'mon....PM plz.

Also, crossover designs from another site? Why not ask some of the builders around here for ideas. They can counsel you on which order slope to use, which formulation(L-R, butterworth, etc...), and crossover points. If you do it right the first time with good parts, you won't have to crossover upgrade your own design.

Early B.

unc2701 wrote: »

Timbre matching aside, where do you plan to find source material that has 40hz info in the center channel?

The VAST majority of soundtracks have no material below about 80hz for the center channel and the algorithms to make a center channel out of a stereo source won't give you any sub-80hz info for most material. Hell, the Wilson Audio center only goes to 55hz for exactly this reason.

That's incorrect. If you set the center channel on LARGE, it will give you a full signal. I've done it before with an AAD center channel that dipped below 30Hz and trust me, there's plenty of material in the center channel that most people don't capture due to the standard 80 Hz cut-off. It's like having an extra subwoofer. Like I said earlier, center channels are generally wimpy due to size constraints. Remove this constraint and the center channel becomes a lethal weapon of mass construction.

ShinAce

This is gonna be a 3 cases of beer job.

Early B.

ShinAce wrote: »

I'm scared.

Firstly, the choice of drivers seems odd. You plan on crossing over an 8 inch woofer over 4KHz? Insane! There will be breakup modes heard. The crossover region will be harsh.

You need to find a way to drop the crossover lower, or change the woofer for something with an extended range.

Secondly, it sounds like you'll end up porting the woofers, but the goal is lots of punhcy bass to accompany a subwoofer that might be integrated to the system. Sounds strange to me.

Lastly, Zingo, 99 db!! Is that 2.83V/m but with 4 ohm drivers? Wanna share your design with me so I can nitpick. C'mon....PM plz.

Also, crossover designs from another site? Why not ask some of the builders around here for ideas. They can counsel you on which order slope to use, which formulation(L-R, butterworth, etc...), and crossover points. If you do it right the first time with good parts, you won't have to crossover upgrade your own design.

First, the crossover will be below 4KHz. The reason to get a computer designed crossover is to mitigate the issues you raised regarding breakup modes. The service to design a 2-way crossover is only $30, so I figure it will be money well spent to do it right the first time. I have no plans to upgrade the crossover once it's designed; I only plan to use premium parts for it.

With regard to your statement about a ported box and integrating it with my existing sub being "strange," I don't understand what you mean. Can you elaborate? Thanks.

Face

Early B. wrote: »

That's incorrect. If you set the center channel on LARGE, it will give you a full signal. I've done it before with an AAD center channel that dipped below 30Hz and trust me, there's plenty of material in the center channel that most people don't capture due to the standard 80 Hz cut-off. It's like having an extra subwoofer. Like I said earlier, center channels are generally wimpy due to size constraints. Remove this constraint and the center channel becomes a lethal weapon of mass construction.

If that's the case, you should just junk the rest of your speakers and listen in mono.

Early B.

ShinAce wrote: »

This is gonna be a 3 cases of beer job.

I'm gonna keep Ben alcohol free for this job. We all know what happens when...;)

Anyway, he's into Arizona Ice Tea.

unc2701

Early B. wrote: »

That's incorrect. If you set the center channel on LARGE, it will give you a full signal. I've done it before with an AAD center channel that dipped below 30Hz and trust me, there's plenty of material in the center channel that most people don't capture due to the standard 80 Hz cut-off. It's like having an extra subwoofer. Like I said earlier, center channels are generally wimpy due to size constraints. Remove this constraint and the center channel becomes a lethal weapon of mass construction.

I'm familiar with the crossover controls in AVR's- that's not the issue. The standard 80hz cut off has lead many of the studios mastering DVD's to not put sub-80hz info on the center channel track. DVD-A seems to be an exception to this... I can't speak to multichannel SACD.

Likewise, many of the stereo to 5.1 algorithms take Left minus right for the center channel. Since bass tends to be recorded in Mono, it gets eliminated.

If you weren't going full steam ahead on this, I'd tell you to hook a sub to your center channel and see what you got, but since you're already committed, might as well see this through. It'll be an interesting project regardless of where your Fs winds up.

Systems

Placing a ribbon tweet that far below the listening axis might not be ideal.Ribbons have excellent horizontal dispersion but their vertical dispersion is usually very poor above and below,the longer the ribbon the worse the vertical response will be.They work best at ear level.Just some food for thought.

A nice center could be assembled using a SEAS 1333 coax for the mid tweet section.http://www.seas.no/images/stories/prestige/pdfdatasheet/h1333_t18re_xfctv2_datasheet.pdf .Madisound has a crossover designed for it.It is an ideal driver for center channel use.

Get a decent 2 channel amp and active crossover like the Marchand XM1 kit then actively crossover at 200- 300hz to a pair of 8"' or 10"s.
example, http://www.parts-express.com/pe/showdetl.cfm?Partnumber=295-456 these 8"s have long excursion capabilty and low Fs so a pair will have serious output capability and they will dig into the low 30's in a reasonable size box.

Then you will have a passive/active center with excellent dialog reproduction from any seating position due to the coax's excellent dispersion and lack of lobing issues,and lots of spl potental below 300hz with the dual woofers.

Early B.

GV#27 wrote: »

Placing a ribbon tweet that far below the listening axis might not be ideal.Ribbons have excellent horizontal dispersion but their vertical dispersion is usually very poor above and below,the longer the ribbon the worse the vertical response will be.They work best at ear level.Just some food for thought.

A nice center could be assembled using a SEAS 1333 coax for the mid tweet section.http://www.seas.no/images/stories/prestige/pdfdatasheet/h1333_t18re_xfctv2_datasheet.pdf .Madisound has a crossover designed for it.It is an ideal driver for center channel use.

Get a decent 2 channel amp and active crossover like the Marchand XM1 kit then actively crossover at 200- 300hz to a pair of 8"' or 10"s.
example, http://www.parts-express.com/pe/showdetl.cfm?Partnumber=295-456 these 8"s have long excursion capabilty and low Fs so a pair will have serious output capability and they will dig into the low 30's in a reasonable size box.

Then you will have a passive/active center with excellent dialog reproduction from any seating position due to the coax's excellent dispersion and lack of lobing issues,and lots of spl potental below 300hz with the dual woofers.

Thanks. I'll look into all of your suggestions when I get home.

Certainly not stuck on the ribbon tweet. The other option we're exploring is the ring radiator tweeter.

ben62670

Early B. wrote: »

I'm gonna keep Ben alcohol free for this job. We all know what happens when...;)

Anyway, he's into Arizona Ice Tea.

I do like the Arizona Tea:) I'll take that any day over booze;)

Early B.

Ben & GV --

What do you think about this driver --

http://www.madisound.com/catalog/product_info.php?products_id=834

ben62670

Only 88db

zingo

You should mount one of these along the entire top of the speaker for your tweeter!

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=264-700

Early B.

ben62670 wrote: »

Only 88db

Is that a bad thing?

I'd love to get a higher sensitvity, 4-ohm driver, but on the other hand, I want the best quality drivers in my price range, so that's why I posted this one.

ben62670

What are your main speakers?

ShinAce

I say take GV's advice.

ben62670

ShinAce wrote: »

I say take GV's advice.

I looked at that driver, and yuck! What a bumpy road:eek: I do agree with the vertical issues with a ribbon, but his seating is far enough back, and the speaker will not be on the floor.

Early B.

ben62670 wrote: »

What are your main speakers?

I dunno. Probably around 90. Nevertheless, with dual 12" woofers in each cabinet, they have a prefer lots of power.

BTW -- the center channel will be powered by a 125 wpc (into 8 ohms) multi-channel amp.

ben62670

I am thinking it is higher than 90 with 2 light 12's.

megasat16

I think GV recommended Dayton should be crossed between 200Hz to 2KHz for use as mid-woofer and get something bigger and badder for the lows. The Fs is showing bumpy graphs below 100Hz and above 2KHz. But for mid-woofer use, they could be awesome.

Early B.

megasat16 wrote: »

I think GV recommended Dayton should be crossed between 200Hz to 2KHz for use as mid-woofer and get something bigger and badder for the lows. The Fs is showing bumpy graphs below 100Hz and above 2KHz. But for mid-woofer use, they could be awesome.

I orginally thought about subs, separate boxes, active crossover, bookshelf speakers, etc., but now I'm thinking -- keep it simple. I just want more authority in the center channel without spending a ton of money and making this project too complicated. Remember -- the budget is $400. If a 2-way single (big!) box design will achieve these objectives, then that's what I want to do.

megasat16

If you want to add the cost of the MDF / woods, glue and the finishing, your actual budget seems less than $250 or less for the actual drivers + crossover + ports. That may be a real low end for getting good drivers.

If you want to make it right in the 1st time and spend it right, I wouldn't choke the budget too much. It's better to spend right amount for one time than doing it multiple times or redoing it to make the center sounds right.

Early B.

megasat16 wrote: »

If you want to add the cost of the MDF / woods, glue and the finishing, your actual budget seems less than $250 or less for the actual drivers + crossover + ports. That may be a real low end for getting good drivers.

You're right. That's why I want to keep it simple. If I can keep the drivers around $250, I'll be OK. That's 4 woofers and 1 tweeter with an average cost of $50 ea. Not too bad.

unc2701

Hell, screw the box. Why not build an Emerald Physics knock off- Got a spare channel on your amp?

Selenium D220Ti :$43
Eminence Alpha x2: $110 (12's or 15's)
DCX2496: $200 off ebay
Waveguide: $10

That's right around $400, you'll have another two channels on the DCX to play with, 99db efficiency and it'll hit to 20hz.

megasat16

I think going active is quite out of the picture at this price point.

And also high efficiency driver with good sound (Fs) is very hard to achieve at this price point. It's like you gotta make a trade off between efficiency and sounds quality and decides what favors you. You can hardly get the best of both world under strict budget.

However, take a look at some of the GR Research drivers in your budget. They may sound good but they are not highly efficient drivers (being 88db). I think 4 of these M165X woofer and Neo3PDR is not a bad pairing for center but you need to raise the ribbon tweeter to your ear level when sitting in front of the TV + center.

http://www.gr-research.com/index.asp?PageAction=VIEWCATS&Category=11

Ben, if you have already got drivers in mind, do share with us.

ShinAce

You can get high efficiency and low Fs if you can afford a very big box. However, other than Pioneer, I haven't seen many companies that build this type of woofer.

Keep looking. I usually spend at least 2-3 weeks mulling over different designs and parts before I settle on the actual build.