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  • The Perfect Center Channel – The Rule Breaker

    Posted by Toids_DIY_Audio on January 19, 2023 at 6:22 am

    The Rule Breaker

    We have all heard that a horizontal MTM is the worst orientation for a center channel speaker.  Yet, it is still the most widely used.  Why?  Well that is pretty easy, it works the best in most people homes.  It is easy to fit under a television in a cabinet.  That got me and @Elliott thinking.  Can we make a horizontal MTM that not only is functional for your living room decor, but also has the dispersion characteristics that you really need to give everyone the best sound?  Well that is what we are trying to accomplish with the Rule Breakers.

    The Problem

    If you aren’t familiar with the issue at hand, a horizontal MTM, has a good dispersion up and down, but side to side we get a lot of cancellation of waves, which make any seats not directly in the center of the speaker terrible.  Basically anyone off to the side will be missing a lot of content, and when we are talking about voices, the main dialogue of the movie, that is a really big deal. It is not uncommon for people on the side to ask you to turn it up or even ask you what they said.  They aren’t hard of hearing (probably) but they are missing some of the most important content.

    So how are we going to fix it?

    It must be said, that some companies have already tried to fix it, similar to the manner we are. The most common fix is to put two woofers on either side with a normal tweeter and midrange sitting  vertically.  Basically the theory is to cross the  midranges over with the woofers low enough that we eliminate most of if not all of the wave cancellations.  The issue with this, is the size of the center channel is typically fairly large, meaning you still have the same problem with fitting it in a normal room.  So how will our project differ?

    Simple, we are still going to use a normal MTM with no larger than 4″ woofers (although you could size this project up with larger woofers if you want). Now typically you would cross this over with a tweeter.  The issue with the tweeter, is it has to crossover too high.  And we really do not want to crossover any higher than 500hz.  Enter the BMR.  BMR stands for Balance Mode Radiator.  And without getting too technical it can get very low (as low as 100hz) and still extend it’s high frequency up to 20Khz!  The best part, a BMR has amazing off axis response.  By using this, we should be able to cross over low enough, to make this no longer an issue.


    • Make a small MTM that does not suffer from the horizontal off axis issues most center channels do
    • Make it affordable – as close to $100 as possible
    • Make it small enough to fit most spaces
    • Make a bigger brother that can dig deeper

    Driver Selection

    Woofers: TCP115-8 4″ woofers

    BMR: TEBM46C20N-4B

    The BMR is by far the most expensive driver, but seeing as we are asking so much of it, it really should be.  But after looking at all the BMR drivers, this seemed to be the best one we could get our hands on. And it should easily be capable of what we are asking of it.

    Now we choose the TCP115-8 in order to get a lower impedance.  Two of them wired in parallel will give you an 4 ohm load.  Now I know some people are going to think this is going to be an issue with their receiver, as most are only rated at 8 ohm.  But based on where this going to be crossed over, I think this will be a very easy load for the amplifier. Of crouse, this we won’t know until we test it. Thankfully I have 4 different receivers I can test this on to make sure it is not an issue.

    Suitable Boxes

    This is interesting the TCP115’s can either go well in a sealed or ported box.  WIth that in mind, there will be two boxes that you can build.  A larger ported box that @Elliott is building and a smaller sealed box that I am building.  The advantage of the sealed box is it should fit in anyone’s living room and in most cabinets.  The downside is you will want to cross it over between 80-120hz based on your room.  The Ported will be able to go down closer to 50hz and is more for those who really want to use these for the whole surround.  And honestly, these really could be used for all speakers.  And should make for a heck of a surround sound when finished.


    Stay tuned and make sure to subscribe if you want to know the updates as they come out.  This is going to be fun!

    Toids_DIY_Audio replied 3 weeks, 5 days ago 2 Members · 2 Replies
  • 2 Replies
  • Nicholas

    November 8, 2023 at 4:13 am

    Where’s the love for this speaker design? Seems like you solved a real problem. What happened to the old thread? It was pretty dead too.

    I built mine and I like it. I love how small it is. It’s plenty loud for our small living room. My wife still complains about not being able to hear dialogue tho. So, not sure if that’s just the mix of modern TV shows and movies, our amp settings or the fact we don’t listen very loud.

    I have very few points of reference and very mediocre audio judging ability. I’d love to know how other people like theirs. So come on people whwre is the love?

    If anyone cares I actually bought the parts to build two more. I figured these would make great desk monitors because I can mount them up on my desk that is in the corner of the room and still get good sound when I’m not sitting right in front of them.

    • Toids_DIY_Audio

      November 10, 2023 at 7:20 am

      Honesty, I do not know. I just bought all the part to make two more of them for my living room. My whole front soundstage is going to be rule breakers. I think Elliott said he wanted to use them as rears. Which honestly would be a cool idea. But I agree, I am surprised as much as you.

      As far as still having issues sometimes, it might be the mix, or even the receiver. Also could be the placement. Wiht some more information, we could try to help you narrow it down if you want.