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Old October 18, 2010, 10:13 PM
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Quote:
Originally Posted by vulcan500rider View Post
Very cool. I can't believe that the 12" is running off that power alone--particularly with three other speakers running off the same output.

Thanks for the crossover diagram, as well; I don't think I'm really anywhere near that level yet...but you never know for the future.

On a complete sidenote, I revisited the first page of this thread, and looked over all the pictures. I notice that in the one you have what appear to be the Tritrix MT surrounds on pedastals. Did you go for the vented or non-vented version? I'm thinking about making my surrounds the vented version, but I'm not sure where to put it, or how much of the cabinet to fill (which may be trial and error anyway, but I don't even have a ballpark guess). Any thoughts?

Cheers,


Sean
Yeah there's no lack of base from the 12's. I mean it's not make your vision go blurry kind of bass but certainly enough to get complaints from the neighbours. Thought the sound isn't that great when I crank it. I'm probably going to make my own amp using these soon. They've gotten great reviews and even converted some tube guys.

Those little MT's are the Dreydels. They use the Dayton RS150S-8, and the Seas 27TDFC... quite a bit different from the tritrix. At the time I was building them I made them ported since I didn't have a sub. Once I got my sub going I plugged the holes to make them sealed. TBH it probably didn't make much of a difference since these are pretty bass limited to begin with - their strength is the mids and highs.

The standard opinion is you should use sealed speakers when crossing to a sub. I'm not an authority on the subject and I don't know the whole reason why but I'll take a guess. The port adds to the bass out put but you don't get a doubling of the output as a whole since the port output is 90 out of phase with the woofer output - well that for the tuning frequncy and gets worse as you go lower in frequency - so the summed output is shifted some degrees. Which is fine when they are by themselves though there are those that argue this phase shift is audible. The big trouble comes when mating this up with a sub. Be cause if your mains are ported its bass output will have that phase shift but the subs wont so you wont get a proper summation and you'll get some wobbles in the frequency response around where the crossover frequency is. Some sub amps have a continuous phase adjust to try to compensate for this but it really only compensates at one particular frequency. A sealed speaker is supposed to track much better through the crossover region.

Now that's a nice theory but it kind of goes out the window when you put the system in a real listening room. Any room will play havoc on smooth bass response so these 'wobbles' may play nice with the room response and kind of iron things out but it may/probably will make things much worse.

If it were me I'd probably make em sealed. BUT the only times your going to be using surrounds is for movies and I think it's be MUCH harder to to pickout any frequency response irregularities watching a movie vs. listening to music where FR and more importantly phase alignment are more critical. However is a whole lot easier to make a ported box sealed (just plug the port) than make a sealed box ported. If you like build the ported if you want to hear the differences, that's part of the beauty of DIY. You could also take it one step further if you wanted to play, since the ported boxes will be bigger than the dedicated sealed versions you can try to hear the differences the box size makes on the box Q and you can easily make a larger box smaller - just put some bricks in through the woofer hole.

Sorry for the novel but one last point. Typically you stuff a sealed box and line a ported box. The stuffing would mess wit the port response and diminish it's effectiveness. But usually some stuff is stuck to the sides of the cabinet to dampen the box so it stays dead. There's some expensive solutions out there for this like dynamat but people use a lot of more readily available (and cheaper) alternatives. Popular materials are roxol safe'n'sound insulation, acoustice ceiling tiles, roofing matt - lots of alternatives out there - google them. Some people leave em naked too. Though you want to make sure you add lots of bracing to the box to make sure it's solid and then they usually just add a wad of stuffing behind the woofer to kill the back wave. Again one of those things you can play with to get the effect you like.

BTW could you clarify what you mean by "don't know where to put them"?

Take care,
Ryan
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