# Active center channel



## F1 fan (Jul 6, 2006)

The center channel is currently the weakest link in my HT so I am planning to upgrade it so that it more closely matches the performance of my main left and right speakers.I am very pleased with the results after having recently completed the conversion of my main speakers to fully active so I thought that I would achieve similar improvements if I did a completely active center as well.

I had originally planned on using a old SEAS H489 coax I still had laying around from project (written up in Speaker Builder magazine 1993)but decided against this because it would be harder to get it to sonically match the timber of the mains.Timber matching across the front stage is very important and the best way to achieve it is by using the same drivers and crossover in all three speakers.

My mains are a 4way which consist of an SEAS aluminum dome tweeter a 6.5" VIFA used as a mid and an 8" SEAS woofer and 10"sub woofers.I dont have the room on top of my TV for a duplicate of this large system so for the CC I settled on an MTM using a SEAS Aluminum dome tweet and two of the same VIFA 6.5" midrange/woofers.The active crossover will be the same LR4 at 2k that is used in the mains.

The MTM seemed like a good choice because you have two woofers sharing the load thus they will be less stressed on demanding sound tracks.The center channel is not just for dialog their can be some very loud effects happening in the CC as well.MTM's can exhibit off axis problems when oriented horizontally but I'am going to do a couple of things to help lessen the severity of them. I got these Ideas from Vance Dickasons DIY Audax CC kit .First I will position the frames of the woofers within an inch of each other to reduce off axis cancellations.Second use tweeter with a small flange that can be positioned between and above the woofers.The tweeter has the same dome and surround as the one used in the mains but the motor and flange are different .Therefore it should still be a reasonably close match.I still use a CRT TV so shielding was also neccessary.

Tweeter http://www.madisound.com/cgi-bin/index.cgi?cart_id=6076084.21227&pid=2138

Woofer http://www.madisound.com/cgi-bin/index.cgi?cart_id=6076084.21227&pid=1345


----------



## Exocer (Apr 19, 2006)

Well, this sounds like a cool project. Good job locating similar matching drivers too. Have you ordered any parts yet? :devil:


----------



## F1 fan (Jul 6, 2006)

Exocer said:


> Well, this sounds like a cool project. Good job locating similar matching drivers too. Have you ordered any parts yet? :devil:


Thanks ,I'm hoping it will meet expectations.

I already have the two Vifa midwoofers and they are the same model driver I use as a midrange in my mains to cover the range 300-2000hz.In the center channel they will handle the 100hz -2000hz.
(a separate 10" woofer in its own enclosure will handle the below 100hz making it a 3way.)

I have not yet ordered the tweeter but the one I intend to get has the same aluminum diaphram as the one in my mains but it has a different magnet and and a smaller flange.


----------



## F1 fan (Jul 6, 2006)

Its taken awhile but Im ready to add venneer and paint the front baffle black.


----------



## drf (Oct 22, 2006)

Nice work. I am interested in what the veneer is you use and how you apply it, some of the veneers availiable here in Oz are very expensive and look rather cheap once applied (even if excessive care is taken). Also what amp are you going to use and are they going to have active or passive crossovers?

cheers,
Dr F


----------



## F1 fan (Jul 6, 2006)

drf said:


> Nice work. I am interested in what the veneer is you use and how you apply it, some of the veneers availiable here in Oz are very expensive and look rather cheap once applied (even if excessive care is taken). Also what amp are you going to use and are they going to have active or passive crossovers?
> 
> cheers,
> Dr F


Hi Dr F,I will be using cherry veneer and I apply it with the wood glue iron on method because I find it much easier and forgiving than using contact cement.Ive veneered several enclosures with this way and had no problems and I only use veneers that have a paper backing.

The amp is a Bryston 2B LP http://www.bryston.ca/2blppro_m.html one channel for the tweeter the other driving the woofers.

The crossover will be an active 4th order linkwitz riley at 2k.


----------



## drf (Oct 22, 2006)

Nice, that should sound fairly awesome.
hope you post plenty of photo's showing the veneering process, I wouldn't mind learning to do it properly. :R


----------



## F1 fan (Jul 6, 2006)

Sure I will post some pics when I do the veneering.


----------



## eddthompson (Aug 19, 2006)

Do you have any more info on your mains? 

Id love to know the details, what crossover, did you wire the tweeter straight to the amplifier etc.

Im realy tempted by a project like this.

edd


----------



## F1 fan (Jul 6, 2006)

Hi edd,I use a 4way setup for my mains using these drivers.

tweeter http://www.madisound.com/cgi-bin/index.cgi?cart_id=8956173.16802&pid=1005

I was using a Vifa M17 for the midrange but recently changed to this one from SEAS 
http://www.madisound.com/cgi-bin/index.cgi?cart_id=8956173.16802&pid=1063

woofer http://www.madisound.com/cgi-bin/index.cgi?cart_id=8956173.16802&pid=1046

and a pair of AC10 10" sealed woofers cover the 50hz and below range.

The crossover points and slopes are 2k 4th order linkwitz riley mid/tweet using a DIY active crossover.

300hz 4th order LR woofer/mid using a Bryston 10BLR active crossover.And a 4th order at 50hz between woofer /sub using a DIY active unit..

To protect the tweeter from possible DC I placed a 47uf poly cap between it and the amp.


----------



## eddthompson (Aug 19, 2006)

I bet they sound great, did you make your crossover, or is it a commerial one, i was probably going to start with the cheapo behringer :bigsmile: 

Of course this is all in theory at the moment due to the possible move :daydream: 

edd


----------



## eddthompson (Aug 19, 2006)

Just found your equipment list to see your using a bryston crossover, im now insanely jealous.

edd


----------



## F1 fan (Jul 6, 2006)

The Bryston is a commercial unit but I built the others.
The Behringers are a good place to get started with active systems.


----------



## F1 fan (Jul 6, 2006)

eddthompson said:


> Just found your equipment list to see your using a bryston crossover,
> 
> edd


Yes it is as good as it gets for a pure analog crossover.


----------



## F1 fan (Jul 6, 2006)

Ive finished the veneering and thought I would post some pics of how I did it.This is a simple method that I have used on several projects and have never had any problems with veneer peeling or air bubbles etc.
First I precut each piece of veneer allowing for about an 1 /8th of an inch overhang that will be trimmed later.

The pieces should be cut in proper sequence so that the grain will match up after it is applied.

I used yellow carpenters glue and applied it to the back side of the veneer and the enclosure with a small foam paint roller as demonstrated by model Shalena.(I didn't really let her use the router):no: 

I let the glue dry to the point of tackiness then carefully lined up the edges and applied mild pressure with the iron.The irons heat control was set 3/4.

Keep working the surface with the iron until the veneer is completely glued down and their are no air bubbles.Be sure that the iron does not sit stationary in one place or it will leave an impression that may or may not be able to be sanded out.
After each piece is in place I used a veneer trimming bit in my router to trim it flush.
A small file was then used to further trim and dress the edges.
Then its time to sand and finish.


----------



## kano32 (Sep 14, 2006)

Looks good. Can't wait to see the finished speaker.


----------



## drf (Oct 22, 2006)

Looks very good, what does using the iron do to the wood workers glue?


----------



## F1 fan (Jul 6, 2006)

drf said:


> Looks very good, what does using the iron do to the wood workers glue?


Thanks.

The idea is to let the glue dry to the point of tackiness or even a bit drier ,then when the heat from the iron is applied it reactivates the dry glue.I prefer this method over contact cement because you can presicely position the veneer before glueing.Whereas with contact cement you only get one shot at it so if a piece is out of alignment you can't fix it.


----------

