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Active center speaker on a budget

ppataki

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Distance is not a problem, directivity is. It’s just the wrong way around ;)

Maybe this is a dummy question but anyway: are you worried about directivity because you need a wider sweet spot or is there something else I am missing here?
 
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voodooless

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Maybe this is a dummy question but anyway: are you worried about directivity because you need a wider sweet spot or is there something else I am missing here?
Basically with a small line array sweetspot is right in front, roughly the width of the array. That is still very narrow. Vertical directivity is also very very narrow. You’ll probably need to tilt the center up towards the listener as well. That last thing might not be a real issue.
 

ppataki

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OK, clear, thanks for the clarification
So to turn this around a bit: if I just need the sweet spot for myself listening on-axis at ear height then probably I don't need to care much about directivity 'issues' - is that more or less correct theoretically speaking?
Sorry for hicjaking this thread, happy to discuss elsewhere too ;)
 

abdo123

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OK, clear, thanks for the clarification
So to turn this around a bit: if I just need the sweet spot for myself listening on-axis at ear height then probably I don't need to care much about directivity 'issues' - is that more or less correct theoretically speaking?
Sorry for hicjaking this thread, happy to discuss elsewhere too ;)
The sound stage is determined by the directivity, if dispersion is not uniformly wide some instruments will sound larger than others, or even worse, the harmonics of the same instruments will sound larger than their fundamentals.

Speakers with better directivity (off-axis is the same as on-axis with just a lower amplitude) behave better in domestic rooms as walls are less radiated by sound once they’re toed-in and the reflected sound is similar in tonality to the direct sound.
 
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voodooless

voodooless

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OK, clear, thanks for the clarification
So to turn this around a bit: if I just need the sweet spot for myself listening on-axis at ear height then probably I don't need to care much about directivity 'issues' - is that more or less correct theoretically speaking?
Kind off. Note that there is also indirect reflected sound. It also has influence your perception. So usually you want this reflected sound (off-axis) to be as smooth as possible (and equal in response to the direct) as well. A normal line array still has some lobing, especially off-axis. Now that does not need to be a major issue depending on your room acoustics. A CBT would be a better option if you can live with a curved baffle.
1639432194922.png

Sorry for hicjaking this thread, happy to discuss elsewhere too ;)
So worries. Asking questions should always be allowed. Worst case, you get an answer, best case you plant some new ideas ;)
 

abdo123

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Kind off. Note that there is also indirect reflected sound. It also has influence your perception. So usually you want this reflected sound (off-axis) to be as smooth as possible (and equal in response to the direct) as well. A normal line array still has some lobing, especially off-axis. Now that does not need to be a major issue depending on your room acoustics. A CBT would be a better option if you can live with a curved baffle.
View attachment 172354

So worries. Asking questions should always be allowed. Worst case, you get an answer, best case you plant some new ideas ;)

It’s incredible how the ceiling is not radiated at all with the CBT, I didn’t know they effectively become a very good horn.
 
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voodooless

voodooless

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It’s incredible how the ceiling is not radiated at all with the CBT, I didn’t know they effectively become a very good horn.
A shaded array does even better in that regard:
1639433401889.png
 

Madjalapeno

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voodooless

voodooless

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I’m about to take the plunge and order the drivers. I’ve been looking at some alternatives for the Lavoce drivers, but it seems they seems to offer the best bang for buck by far. Also tried some 3~4” “subwoofer” drivers, but they are all about 80dB efficient and have so little power handling that maximum output is severely limited. You just can’t beat Hofmann's Iron Law.

If anyone has some alternative idea, let me know! The 11cm chassis diameter is the most important limitation here.
 
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voodooless

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Another thing is that B&C now added the 4MCX36, a variant of the 4” coax with higher efficiency.

As viable alternative for the Lavoce drivers I found Monaco’s SHP100c. Only two would be needed to match the max output of the coax. Above 100hz the Lavoce quartet will be louder, but the question is if that is very useful? The Monaco’s will go lower though. Question here is: what would be really useful? Another advantage of two drivers is that it will give a smaller package. It’s to bad there are no distortion measurements of any of these drivers. I know from the past though that the Monacor drivers perform very well in this regard.
 
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voodooless

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I’ll just continue my monologue ;). Found some measurements of the Monacor. Looks pretty good.

I also found out that the datasheet provided by toutlehautparleur of the Lavoce driver is rather different from the one on the official site. The FS is much higher on the official one, which is not good for my purpose.not sure what to think of this.
 
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voodooless

voodooless

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Arnandsway

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What! That is cheap indeed. The main issue however is that it’s to big.

Maybe I should think about mounting it on top of the TV instead of below it..
I've read some comments on this forum, I think it's here somewhere where it could be beneficial to have the center channel above your screen. But I have no idea if this holds true or not (or in which situations it does).
 
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voodooless

voodooless

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The general agreement seems to be to just choose the place that gets the tweeter closest to the mains tweeter alignment. At the moment in my case that would be below the TV, but the margin is small.
 
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voodooless

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So with the KEF unit, it might look something like this for a over TV mounting option:
1643019464485.png

Obviously, I stole the design elements from the Blade. Could use 4x FaitalPro 5FE100. Rough size is 25x30x30 cm (WxDxH). Would also make nice surround speakers as well.
 

howard416

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Er, not sure if it's too late, but you could technically fit an OX20SC00 and an SB65WBAC25 on top of each other. That'll get you down below 600 Hz, easy.


http://www.zaphaudio.com/blog.html (search for OX20)

From ~200 Hz down, you can have a down-firing slot-loaded woofer behind the baffled drivers, with a bit of tweaking I think you could keep the 1/4 wave pipe resonance out of its passband and give yourself more room for a bigger woofer (shallow but wide). Two of these? http://www.loudspeakerdatabase.com/Peerless/GBS-135F25AL02-04

No time right now to do more research/thinking, sorry.
 
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voodooless

voodooless

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Er, not sure if it's too late, but you could technically fit an OX20SC00 and an SB65WBAC25 on top of each other. That'll get you down below 600 Hz, easy.
SB65WBAC25 really doesn't get super loud, but I think it's an interesting idea nevertheless. It is a very nice driver.
From ~200 Hz down, you can have a down-firing slot-loaded woofer behind the baffled drivers, with a bit of tweaking I think you could keep the 1/4 wave pipe resonance out of its passband and give yourself more room for a bigger woofer (shallow but wide). Two of these? http://www.loudspeakerdatabase.com/Peerless/GBS-135F25AL02-04
Looks like fun. Might work indeed. However, these low-profile woofers often have quite bad distortion figures.
No time right now to do more research/thinking, sorry.
All hints help, so thanks a lot!

On the other side of things, I've been thinking and deliberating with the wife, and possibly I'll be canceling the project in favor of a trio of Genelec 8030C's (LRC). They won't get as loud as this center concept, but It's readily made, good quality, very good value, and my wife likes the design well enough to tolerate it in the living room. And looking at distortion figures @ 96 dB already, I think it should do pretty well.

On the one side, I like to do some DIY again. On the other side, I have too little time for it anyway and chances are high I end up never finishing the project...
 

howard416

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SB65WBAC25 really doesn't get super loud
From a distortion standpoint, or a power handling standpoint?

If the former, smart selection of the HP frequency helps get away from rising bass distortion, assuming your other drivers & physical considerations allow it.

If the latter, if you restrict the bandwidth, you can increase the overall effective SPL capability (same power handling, less spectrum coverage).

Admittedly, it only takes 20 W and has a sensitivity around 80 dB / W @ 1 m... (4 ohm driver with 83 dB / 2.83 V @ 1 m), but in practice, for a center channel application I think you can really push much harder. In use, you should able to achieve much more, but don't expect full-power sine sweeps.
 
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