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12" frontal mid tops

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Daganjah View Drop Down
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    Posted: 29 June 2020 at 11:43am
hello everybody!
im looking for a 2 way 12" mid top speaker plans 
I currently have a MT-122 box that I built (I made a single speaker box with no tweeter).
I'm running a 5 way sound system and I want to change the design of my tops.
I don't want to use any horn design
what would you recommend?
thank for your help!
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studio45 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote studio45 Quote  Post ReplyReply Direct Link To This Post Posted: 29 June 2020 at 2:15pm
Where in the world are you based mate? That will affect which drivers and materials you can get.

12" reflex designs are simple to make, you don't really need a plan; you just need to calculate the required volume and port size using WinISD or BassBox, or any similar software, and then work out a box based on that. You may not even need it to be a reflex box, depending on how low it needs to play - if not very low, a sealed box may be OK, and much simpler.

If you're a woodwork beginner, rectangular boxes are OK; if you can deal with cutting accurate angles, trapeizoid boxes are better (ie wider at the front, narrower at the back). 


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Post Options Post Options   Thanks (0) Thanks(0)   Quote Daganjah Quote  Post ReplyReply Direct Link To This Post Posted: 29 June 2020 at 7:16pm
Thanks for your reply!
I already got b&c 12fw76 drivers. 
I don’t have any experience with calculating software.
How complicated is it to use them?
About the woodworking, I have plenty of experience:)
What about the tweeters? Do I consider them in the calculating software?


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Post Options Post Options   Thanks (0) Thanks(0)   Quote snowflake Quote  Post ReplyReply Direct Link To This Post Posted: 29 June 2020 at 7:55pm
if you have a two way mid top, how are you getting to a five way system?
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csg View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote csg Quote  Post ReplyReply Direct Link To This Post Posted: 29 June 2020 at 8:21pm
3 different sorts of bass bins
“The fact is this is about identifying what we do best and finding more ways of doing less of it better”
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Digbethdave Quote  Post ReplyReply Direct Link To This Post Posted: 29 June 2020 at 9:59pm
Originally posted by csg csg wrote:

3 different sorts of bass bins
4 bullets and some piezos
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Daganjah Quote  Post ReplyReply Direct Link To This Post Posted: 30 June 2020 at 4:50am
I have 6 scoops, 2 15x2 reflex kick bins, 4 mid top 2way and 4 super tweeters 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote studio45 Quote  Post ReplyReply Direct Link To This Post Posted: 30 June 2020 at 2:22pm
Originally posted by Daganjah Daganjah wrote:

Thanks for your reply!
I already got b&c 12fw76 drivers. 
I don’t have any experience with calculating software.
How complicated is it to use them?
About the woodworking, I have plenty of experience:)
What about the tweeters? Do I consider them in the calculating software?



The software is quite easy to use. The most complicated bit is entering your driver's Thiele-Small parameters, this is a list of numbers on the datasheet. They've got to be entered correctly and there are quite a few. If any are wrong, the software will either throw up an error, or generate nonsense.

When you have entered them, it's simply a matter of selecting a sealed, reflex or bandpass box to begin simulation.

The software will then have a "guess" at a box size (and port size/length if required) and generate a graph of the expected output level vs frequency. Then you change the box size and port sizes, and see how the graph changes, in real time. Normally the goal is to get the lower bass extension down as far as you can, but:

There are other graphs too, like phase, driver excursion and group delay - they've all got to be as close to "good" as you can get them, for the design to work well.

The phase graph shows you how the output phase angle changes with frequency (-180 to +180 degrees). It will be a crazy looking graph with many sawtooth shapes on it, and it's near impossible to get it to be flat (that would represent an unattainable "perfect" speaker). On a basic level, you want this graph to show as little change in phase as possible over your driver's intended operating range, but don't spend too long trying to get it perfect. The actual angle is not very important, only the variation.

The group delay graph is another way of looking at the phase data. It shows the delay in milliseconds vs frequency, caused by the resonance of your port tuning and box size. Again, the best scenario is as little change in GD as possible over your intended range. Large spikes are to be avoided, as they represent a frequency "ringing" or "booming" in the box, which will sound bad. A nice flat or gently sloping GD graph gives a dry, well-controlled bass sound.

The driver excursion graph is pretty self - explanatory - it's how far the cone moves for a specified power input, vs frequency. You want this to stay under your driver's Xmax figure, when the power input is what you want to give it (For eg a 300 watt driver you would set the simulated power to 300 watts). Some of the software will draw a red limit line at Xmax on this graph for you, so it's easy to see if you stay under it.

When you've got all your graphs looking the way you want them, you take the box volume and port size figures from the software, and work it out in real life. Then build a test box out of cheap material, and check if it sounds OK. 

You don't need to include the tweeter in the simulation. Tweeter horns are what they are, you just select one that's big enough to play down to the frequency you need it to, and the right shape to get the dispersion you require. Tweeter drivers aren't simulated by the majority of software, and it's expected that you simply take the manufacturer's figures as truth, and select an appropriate crossover point based on those. 

You do need to take the volume occupied by the tweeter driver and horn into account when calculating your box size, otherwise your box volume will be too small by that amount. Similarly the volume occupied by the port is not accounted for by the software, so you need to add it on when working out the size.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Daganjah Quote  Post ReplyReply Direct Link To This Post Posted: 30 June 2020 at 5:23pm
Wow thanks for all the information!
It look like I have alot to learn
I’ll try to follow you instructions and use the software you recommended. 
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