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Old 6th September 2011, 09:09 AM   #2311
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Quote:
Originally Posted by rubennn View Post
Question for Saturnus actually regarding this function in WinISD: How does one find the optimal tuning frequency for the specific driver? Because there is clearly a difference when choosing another driver
That depends on what you consider optimal tuning

winISD is a little cumbersome when finding the optimum tuning frequency as it (as it should) uses different calculations depending on the speakers Qts. However, for one that does not want to use standard tunings that approach is useless. You have to use the winISD online tool, plot in the 3 driver specs and find the "optimum" Vb and Fb there. From those numbers you can calculate your own tuning frequency depending on Vb and desired Qtc by hand.
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Old 6th September 2011, 09:35 PM   #2312
rubennn is offline rubennn  Denmark
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Originally Posted by Saturnus View Post
That depends on what you consider optimal tuning

winISD is a little cumbersome when finding the optimum tuning frequency as it (as it should) uses different calculations depending on the speakers Qts. However, for one that does not want to use standard tunings that approach is useless. You have to use the winISD online tool, plot in the 3 driver specs and find the "optimum" Vb and Fb there. From those numbers you can calculate your own tuning frequency depending on Vb and desired Qtc by hand.
Enlightening information. Still, some things make me wonder.

When designing a boombox for outdoor use, what are you looking for? I guess that the rise +3 dB just around the downward rolloff frequency is wanted. Are you just messing around with Vb and Fb until you get something that looks usable?

This is what I see:
Click the image to open in full size.

Here I just put it some random values in Vb and Fb and used the specs from the HP-10W. But as I can see you are apparently tweaking the tuning frequency somehow to be 69.8 hz (or whatever the new tuning frequency for the HP-10W was) down from the previous tuning frequency of 82 hz. That's where I can't follow you anymore

I hope this is not me being stupid and asking silly questions, but it could be cool to fully understand the meaning behind everything related to boomboxes - of course
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Old 6th September 2011, 11:05 PM   #2313
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Originally Posted by rubennn View Post
When designing a boombox for outdoor use, what are you looking for? I guess that the rise +3 dB just around the downward rolloff frequency is wanted. Are you just messing around with Vb and Fb until you get something that looks usable?
No, I think I've said it 5 times already in this thread. Use the winISD online. Click "optimum". note the resulting Vb and Fb.

Then to get Q=1.207 instead of Q=0.707 divide Vb with Pi and multiply Fb with square root of 2. That gives Q=1.207 with a +2.82dB peak which is optimum for an outdoors boombox. Very simple.

For other tunings, use other calculations. Don't just assume you can just fiddle around with winISD setting blindly, and think it works in real life. It usually doesn't.

Note. The tuning frequency (defined by Fb) was never 82 Hz for any version of the Boominator. New or old. The 82 Hz was the lower 0dB point which is the outdoors equivalent of the tuning frequency, ie. the lowest frequency the speaker can realistically produce.

The tuning frequency, Fb, is in standard calculation equal to the lower -3dB frequency but that's not relevant when your have another tuning Q than the "optimum".

Last edited by Saturnus; 6th September 2011 at 11:10 PM.
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Old 7th September 2011, 06:15 AM   #2314
rubennn is offline rubennn  Denmark
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Well thanks a lot for your help, Saturnus (once more). I am getting the same numbers as you now ^^

Bookmarked this post for greater good also (I can't believe I've missed the 5 times you've written it).
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Old 7th September 2011, 02:57 PM   #2315
donnib is offline donnib  Denmark
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Can anyone tell me how deep the cut in the center brace has to be where it has to go around the port ?
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Old 7th September 2011, 03:12 PM   #2316
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I'm guessing you mean this?
Click the image to open in full size.

On the SketchUp drawing it's 92mm.
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Old 7th September 2011, 04:30 PM   #2317
donnib is offline donnib  Denmark
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Originally Posted by Kostecki View Post
I'm guessing you mean this?
Click the image to open in full size.

On the SketchUp drawing it's 92mm.
Yes, thank you

Last edited by donnib; 7th September 2011 at 04:35 PM.
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Old 10th September 2011, 12:35 PM   #2318
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@ rubennn,

What are your thoughts on the half Boominator? Are you satisfied with it's performance?
(I'm sorry if this has already been answered but this is a pretty huge thread.)
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Old 10th September 2011, 03:03 PM   #2319
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Originally Posted by Djimmi View Post
@ rubennn,

What are your thoughts on the half Boominator? Are you satisfied with it's performance?
(I'm sorry if this has already been answered but this is a pretty huge thread.)
I'll just answer that with a quote, since i also needed info on that subject some time ago

Quote:
Originally Posted by rubennn View Post
I can vouche for the half boominator. It works for me and worked for my camp also. There are 2 major cons and 3 major pros for building such a boombox. Deciding how much they each weigh is up to you:

Half boominator:
Pros:
- You'll save money
- Half the power use at max. vol. due to system impedance being 8 ohm instead of 4 ohm (and thus also lowering output - see cons)
- The boombox weighs less

Cons:
- As far as I can recall you lose 6 dB in sound pressure level at max. vol. because of the 2 drivers instead of 4 and system impedance is 8 ohm instead of 4 ohm.
- Sound quality is compromised and phase problems may occur (still WAY better than any store bought boomblaster!)

I like both the half boominator and the full boominator. But I would advise you to build the full boominator if you are going to be 16 people. If you wanna party with a half boominator you should be less than 10 people - it's simply not loud enough.
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Old 10th September 2011, 07:25 PM   #2320
rubennn is offline rubennn  Denmark
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Let me also put it like this (in addition to what Kostecki posted):

For next years Roskilde Festival I'm planning to building the full boominator. I want to host small techno/house parties for my friends at the festival camping site.... And for that I need the full boominator (maybe also with a more powerful amplifier, but I'm not sure about this yet)
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