# Inexpensive, easy, center channel?



## aceinc (Oct 24, 2006)

My sanity requires that I do something other than work, and my HT's weakest link is currently the center channel. My mains are currently KEF 105/4s  I picked up at a garage sale, the rear speakers are Morth Audio Echo's, my sub system is a Rythmic Audio DS15, and a pair of Titanic 10s.

My center channel is an Onkyo Fusion AV S19 that I picked up Open Box at a Circuit City 5+ years ago for $25.00. It has two 4" foam surround drivers, and what looks like a 1" dome tweeter. I was bored and opened it a few years ago, I remember it having a single cap crossover. Before I put the drivers back in I put some fiber fill in, without much affect.

My requirements are;

1) must sit nicely in front of my table top lcd tv, or perhaps underneath as a stand.

2) must do the center channel thing well. I guess this means it must do midrange extremely well and the rest of the frequency spectrum fairly well.

3) can't be too efficient/inefficient, my fronts have published specs of 86 db 1w-1m pink noise.

4) must be easy to build, with a fairly simple xover.

5) must be relatively inexpensive.

6) must wash my car on weekends... (Hey if it can do the first 5, why not go big?)

Anybody have any favorites?

Paul


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## F1 fan (Jul 6, 2006)

This kit uses a SEAS coax driver that is identical in design to the UNI-Q driver in your KEF's.It may suite your needs. http://www.madisound.com/cgi-bin/index.cgi?cart_id=8956173.16802&pid=2053


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## aceinc (Oct 24, 2006)

This looks interesting, a little too much money, and not enough work. Part of my goal is to keep myself occupied and not thinking about work. Perhaps I could buy the driver and do the rest myself.

I have an odd question, somewhat off topic. When you have a Coax driver as this is, and the tweeter is effectively horn loaded by the woofer, how does the woofer's movement affect the sound of the tweeter? I would think there would be doppler distortion to contend with, or at a minimum, the "horn's" geometry would change in relation to the tweeter, causing some form of audible artifact. Anybody know whether this is true?

Paul


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## F1 fan (Jul 6, 2006)

aceinc said:


> This looks interesting, a little too much money, and not enough work. Part of my goal is to keep myself occupied and not thinking about work. Perhaps I could buy the driver and do the rest myself.
> 
> I have an odd question, somewhat off topic. When you have a Coax driver as this is, and the tweeter is effectively horn loaded by the woofer, how does the woofer's movement affect the sound of the tweeter? I would think there would be doppler distortion to contend with, or at a minimum, the "horn's" geometry would change in relation to the tweeter, causing some form of audible artifact. Anybody know whether this is true?
> 
> Paul


you can buy just the driver and crossover as well. http://www.madisound.com/cgi-bin/index.cgi?cart_id=8956173.16802&pid=2060

Yes the tweeter being loaded by a moving horn does have some doppler issues which can give it a slight cupped hands over the mouth sound but the effect is relatively minor.Also due to reflections off of the woofers cone the tweeters on axis response gets a bit rough around 10k or so but smooths out at 10 degrees off axis.
Do you notice any of this with your KEF's?
But there are several benifits to this coincidental arrangement as well.


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## aceinc (Oct 24, 2006)

> Do you notice any of this with your KEF's?


The 105/4 has separate mid & tweeter sections. See;
http://www.kef.com/history/1980/model105_4.asp

Paul


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## kano32 (Sep 14, 2006)

Here are a couple of links to DIY center speakers:

http://www.htguide.com/forum/showthread.php4?t=15323

http://www.htguide.com/forum/showthread.php4?t=19887

http://www.htguide.com/forum/showthread.php4?t=11475

And scroll through this project showcase to find different center designs.

http://www.partsexpress.com/projectshowcase/homeaudio.cfm


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## F1 fan (Jul 6, 2006)

aceinc said:


> The 105/4 has separate mid & tweeter sections. See;
> http://www.kef.com/history/1980/model105_4.asp
> 
> Paul


Sorry for the confusion but I thought it was this model of the 105/3 that you had.It has the UNI-Q driver for mids and tweet.http://www.kef.com/history/1980/model105_3.asp


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## aceinc (Oct 24, 2006)

I was looking at the PE Cynosure, and I found the xover design interesting. Has anyone had any experience with this type of design?

I would like some opinions from folks who have heard this type of xover network, preferably.

I was thinking about using eight of the HiVi B3s, and a tweeter crossed over at 4khz, and if I get a wild hair, I might add a pair of Tang Band W5-1138SM crossed over at 300 hz. Since all of the drivers would be well within their working ranges, I thought 6 db slopes would be simple, inexpensive, and adequate for my needs.

One question that crops up, is do I need to do the varying low pass filters on the Hi Vi B3s array? What are the pros & cons?

Paul


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## Guest (Apr 16, 2007)

I just finished a CSSWR125/Seas center channel that I am happy with. Total cost was under $200. I plan to post the details of the speaker in a separate post.


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## aceinc (Oct 24, 2006)

I have an idea for an inexpensive, (less than $50 in drivers) though not necessarily easy center channel.

Below is a Google sketchup rendition, I just started using sketchup this evening, so don't pick on the quality. I intend to use series/parallel for all drivers. It is about 36" wide & 8-3/4" high by about 15" deep, and will be a stand for my 46" LCD TV.

Even though they will be built as separate cabinets, they will have a single back panel, and will be glued together, sanded and finished as a single cabinet. All baffle edges will be rounded, the mids, and tweeters will be sunk below the level of the woofers. The woofers are 5", mids are 3" and the tweets are 5/8".

WinISD says I can get less than 50hz f3 using the drivers, ported in the cabinets shown.

My first stab at a xover will be a 1st order at 600 & 4000 hz with an L-Pad on the tweets and mids. Part of my KISS approach.


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## aceinc (Oct 24, 2006)

If anyone is following this thread, I have built the box, but I am waiting for the drivers to hole the baffle. I went with a single large box separated into three main chambers, 1 for the mids & tweeters, and 2 for the woofers. I also created a small area behind the mid/tweet section to mount the xover, as I believe that this will be the crux of the biscuit, and I want easy access to modify it.

I chose not to go with a "time aligned" arrangement for three main reasons;

1) I will be trying a 1st order xover first, which throws the drivers out of phase by 90 degrees at the xover.

2) I felt that I may have a problem with dispersion if the tweeters were buried, and surrounded by wood.

3) I picked up some scrap 3/4" sand-ply for free, and building the individual cabinets and gluing them together would look like ****, and my cabinet building skills left cutting the top & bottom to match the time aligned array design, an impossibility.

So the cabinet is 3/4" Sand-Ply top, bottom and sides. the baffle is 1-1/4" MDF, the back and internal pieces are 3/4" MDF. It ended up being 32"w x 8-1/2"h x 15-3/4"d. 

My wife likes the idea of a base for the TV.

Paul


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## kano32 (Sep 14, 2006)

It looks pretty complicated. I hope it works out well.


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## Guest (Apr 27, 2007)

there are a couple of designs for different center channels on this page that should be fairly inexpensive

users.d-web.com/dbrown/speakers/speakers.htm


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## aceinc (Oct 24, 2006)

> there are a couple of designs for different center channels on this page that should be fairly inexpensive


The speakers on the page you included look great, but I have already started the project. There is a good possibility that what I cooked up may not sound optimal,:hissyfit: in which case, I will try again.

Paul


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## aceinc (Oct 24, 2006)

Well If anyone is still paying attention I have finished the cabinet, installed the speakers and after a few false starts have a working speaker. I will be doing some testing over the weekend and post my results.

I have accomplished the inexpensive part of this project, easy part is questionable. I spent about $54 on drivers, $5 on the xover, and about $30 on other electronics, including L-pads that I may not have needed.

The speaker blends into my system fairly seamlessly, the dialog is clear. After watching one movie, "Blood Diamond" I like it.

Here's a couple of pictures of the finished speaker.


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## drf (Oct 22, 2006)

looks good. :T I wish we could by drivers that cheap in Aus. AM$54 would by 2 3/4 really cheap 4"drivers, and nothing else. :hissyfit: 

If after a while you decide it isn't good enough you can experiment with active crossovers. I have found the learning curve to be actually easier with active than passive (that might just be my background in electronics though), and I have found them to be superior to passive. It really is horses for courses and personal preference though.


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## aceinc (Oct 24, 2006)

Well another exciting day in S Florida, I began testing the center channel. 

It sure would be nice, a lot easier too, if I knew what the **** I was doing. 

At any rate, last night while I was putting the xover wired correctly in the speaker, my lovely bride, got as many comforters, blankets, towels and pillows she could lay her hands on and covered as many hard surfaces as easily doable in our den. Not an anechoic chamber, but as dead as we can easily make it.

So I gathered up my tablet computer, microphone, RS SPL meter, an old pioneer receiver and a boatload of cables. My testing started with some pretty bad graphs, so I twiddled knobs on the L-pads without much luck. I had a real nasty peak at about 80hz, was down quite a bit at 2-4khz, and lots of other smaller dips and peaks.

So I pulled the xover out and tested the individual drivers. The bad peak at 80hz was definitely in the woofers. My Mids weren't doing anything below 1khz, but the tweets were doing what I expected, but they weren't as loud as I expected. After mucking about trying anything I could think of I finally decided that the mids weren't able to breathe because I had cut the holes too small. I had used a chamfer bit on my router to open the holes from the back while I was making the baffle, but evidently not enough.

So I covered the tweeters, removed the Mids got out my zip tool, and a dovetail router bit and started opening the holes. I Highly recommend that you get good clearance for the back of your drivers before you mount the baffle. I only nicked one finger with the router bit at 20+krpm, no stitches required, but when I put it all back together I had mid freq's down to 200hz.

I now had a dip from about 3k-8khz and the nasty hump at 80 hz, I tried adding various resistors to the mid and/or the woofersto level things out, and got a pretty decent graph, and the sound was pretty good, but I wanted more. So after dinner I my wife & I went to WalM*rt, and picked up some more Polyfill I came home and stuffed quite a bit into the woofer sections, and tested some more. It did have a slight beneficial affect, but not what I really wanted. 

At a bit of a loss, I decided to try one last thing, I got out some RS electrolytic Caps I had laying about, pulled the xover out and attached a 4.7u cap in series to the tweeters, and 50u paralleled with a 10u (net 60u) in series with the mid section. This yielded one of the best plots of the day, so I crimped everything down, and left it this way.

At some point I will revisit this, but only when I get someone that really knows what they are doing to help me. For now it sounds pretty good, and is lightyears better than the Onkyo center it replaces.

Here is the current graph;


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## bigguy (Feb 26, 2007)

So much eduk8shun available on this thread and all I wanted to know was where Paul got that nice cabinet... :bigsmile:

Like my dad always said...
"...buy em book and send em to school and all they do is eat the pages....."

lol
Dan

BTW.. that center channel looks great.. cant wait to get to the testing results...


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## FlashJim (May 6, 2006)

Great looking speaker. Post your bill of materials in case someone else wants to give it a try.


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