Center channel considerations

[Hezz]

Caratje,

Just a few responses to your questions.

Placing the tweeter higher up between the center of two mid bass drivers in the horizontal center channel configuration is one method of helping to alliviate part of the problems created by that design.

As to the different speaker volumes.

The center channel has less volume which makes it's bass response less good than the mains. This is done as a compromise because the center does not need as good of bass response. But unfortunately all things come at some expense because the transient response of the speaker is also not as good when the volume is lowered but with bass reflex designs this is less of a problem because the box is leaky.

Also, because the center channel speakers are ideally placed near the TV they usually have to be smaller in size by necessity. This does not however, improve certain aspects of the sound quality.


The separate chambers in the mains is probably because they are actually a 2.5 way design. Often only one speaker is the mid-bass and the upper one functions as a mid only. The seperation is to keep the lower frequency signals from modulating the midrange speaker which makes it more accurate.

It is also possible that the separate chambers is just an inexpensive way of bracing the speakers without having to make extra cuts. Since the total volume of the speaker cavity must be large enough to account for both speakers. So if you divide the speaker in half with a wall you are just giving each speaker it's own space and creating a brace at the same time.

Hezz

[merlinx76]

One guy makes me consider new mains and the other tries to convince me I need a better receiver. Yeah the amp is a chip amp, I can see a huge IC through the vents at the top. I have an old Realistic amp that even sounds a little better (at least on the speakers I tried it on) . I was thinking about getting a high end pioneer (not elite but the highest standard line) but I've decided that's way down the list... I shouldn't be even considering it really.


About the Vifa MG18... I was eyeing already and you read my mind pretty much. I was just spacing out the hundreds of questions.

It's cheap, should be adequate although when you figure the cost of the whole thing by the time it's finished an extra little on the woofer doesn't make a whole lotta difference either.

I'm not sure on the TV stand either. It looks better but then I am stuck with the speaker at that exact spot and angle. If I make it separate I can try different positioning: i'll try above the TV,then I can put the TV on a temporary bench and angle the speaker below it. If I keep it below I can just make a small stand for it. This way if my listening room changes I can easily adapt the speaker if need be.

Are we going for form or function?

[cjd]

Hey, I don't think you need new mains. Not really - that was an attempt at humor.

Why not add bucking magnets to the same Vifa woofers you're using in your mains?

C

[Hezz]

Merlin,

In the end it's only you who knows what will work best for your home theater setup. I think the MG18 is as close as your going to get to your mains for a similar speaker. As far as the Tv stand cabinet goes that is purely a function thing for me as I am building a front projector. If you do not have these goals then a standard box may be the best for you. But bear in mind that there are not many placement options with a TV. Your either on top which means that unless your tv is large the speaker has to be quite small. Or underneath on a shelf. OF course you can place it on a stand in front of the TV but most people don't like the aesthetics of that.

I hope you don't think I am trying to change your priorities. I think It is fine that you are pursuing your speaker and sound transducers at the present time. I only wanted you to consider the source issue as it is bigger than you might think.

Keep us posted on your progress as it is interesting to see what you decide to do. One thing I would do is to look at some commercial designs which might work for you.

Here is a variation on the MTM which alleviates some of the problems that the MTM has in the horizontal orientation.

Hezz

[Hezz]

Also, there is no reason why this configuration would not work well.

Hezz

[merlinx76]

Originally posted by cjd
Hey, I don't think you need new mains. Not really - that was an attempt at humor.

Why not add bucking magnets to the same Vifa woofers you're using in your mains?

C

You already know what I am just now figuring out... I'm gonna build a lotta speakers. I caught that bug that's been goin' around.

I guess that's 1 more thing to consider; DIY shielding. I don't know if I can recalculate the T/S params after i put a bucking magnet though.

[caratje]

Hi Hezz,

Thanks for trying to answer my questions, but of course I am not yet fully satisfied...

My fronts are indeed base on a 2.5 way principle with a semi separation between the tweeter+mid woofer and bass-woofer, but as far as I understand the center too (I think identical filter!!!) and that one is just one big open box??? But maybe this makes the full volume available for the bass-wafer larger!!!

So, I guess I kind of understand what has been done during the designing of the center speaker, having the fronts as 'holy' reference. At this moment I am sticking to that design and if I am not satisfied I might experiment with using the 2-way design (like my rears) or do measurement and reconsider the filter, but I expect it will be all fine!!!

Oh, CJD's remark on adding bucking magnets, I am not 100% sure if he is meaning the same, but shielding a woofer is for the largest part just putting a magnetic shield over the original magnet of the woofer. Basicly you can do this yourself on none-shielded woofers, but don't ask me for details on how to do this and how affective this will be???

Maybe my last question is a little of the original subject, but if you consider to put your center speaker above your television screen instead of below (height difference will be comparable and floor space is pretty important to me), how to do this best?

That means, is the wall beter than the ceiling (concrete ceiling, but very very hard!!!)

And do I still need spikes (between speaker and stage or fixate speaker box directly to wall/ceiling)


C U,

Joep