The Boominator - another stab at the ultimate party machine

This has probably already been asked (I searched the forum but couldn't find anything) but what's the power consumption of the maxamp20 playing at loudest volume?
If I'd use a 7aH 12v lifepo4, or SLA if that matters, (I could calculate this meself if I get the power consumption I guess) how long would it last at the roskilde festival? Would I be set for all 9 days if I got a 10W solar panel too?

Also will there be a meetup this year too? :)
 
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Boominator MINI DIY Filter and Comments

I'm finally back.

After having done extensive calculations. Scratching my head and redoing them a couple of times, I can now finally say that I found out what the problem was.

It turns out my calculations were correct all along and that WINISD online calculates both closed and reflex cabinets incorrectly. Please be warned about this. Please use a different cabinet calculator or use the actual formulas.

That means the sketch-up drawing already posted of the MINI is correct except that you might wanna exchange the double front with a single 12mm instead as commented earlier.

To the filter there's not much to say. It's pretty self-explanatory. However, I strongly recommend using the ferrite choke if you are using a "filterless" class D amp like a maxamp20 or a Sure TPA3110. Even if you are not it is the better sounding option but the chokes that match can be tricky to find.

The filter is for the MINI only. Another one will come for the Micro or a dual amped MINI. A dual amped MINI is basically to get the very most out of the speaker you can use the SP60/4 instead of SP60/8. That means each side of the speaker is effectively a Micro and so must be dual amped and use the filter for the Micro.
 

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This has probably already been asked (I searched the forum but couldn't find anything) but what's the power consumption of the maxamp20 playing at loudest volume?
If I'd use a 7aH 12v lifepo4, or SLA if that matters, (I could calculate this meself if I get the power consumption I guess) how long would it last at the roskilde festival? Would I be set for all 9 days if I got a 10W solar panel too?

Also will there be a meetup this year too? :)

About 340mA (20mA lower than TA2020 amp).

There surely will be.
 
"mini" 12mm baffle question

I'm finally back.

After having done extensive calculations. Scratching my head and redoing them a couple of times, I can now finally say that I found out what the problem was.

It turns out my calculations were correct all along and that WINISD online calculates both closed and reflex cabinets incorrectly. Please be warned about this. Please use a different cabinet calculator or use the actual formulas.

That means the sketch-up drawing already posted of the MINI is correct except that you might wanna exchange the double front with a single 12mm instead as commented earlier.

To the filter there's not much to say. It's pretty self-explanatory. However, I strongly recommend using the ferrite choke if you are using a "filterless" class D amp like a maxamp20 or a Sure TPA3110. Even if you are not it is the better sounding option but the chokes that match can be tricky to find.

The filter is for the MINI only. Another one will come for the Micro or a dual amped MINI. A dual amped MINI is basically to get the very most out of the speaker you can use the SP60/4 instead of SP60/8. That means each side of the speaker is effectively a Micro and so must be dual amped and use the filter for the Micro.


Hi Saturnus

Welcome back, and thanks for all the head scratching that you do for our collective benefit :)

a couple of questions been bugging me tho......

On your sketchup drawing, the front baffles that are made up of two 6mm layers stuck together show that the "inside" layer has holes like the "internal" baffle between the drivers. Obviously this effect would be fairly difficult to achieve with a single 12mm baffle as the "holes" would have to be routed to a depth of 6mm...

I'm assuming that actually, these "holes" are not really needed but are a result of you using "copies" of the internal baffle in the sketchup diagram for ease of drawing. Therefore a straight 12mm baffle without 6mm deep "holes" will be fine.....

also

you have also previously mentioned that standard 6mm ply is actually 6.5mm and that may affect the calculations. Am I right in saying that his is no longer an issue?

Getting my ply cut now.....

BJ
 
Hi Saturnus

Welcome back, and thanks for all the head scratching that you do for our collective benefit :)

a couple of questions been bugging me tho......

On your sketchup drawing, the front baffles that are made up of two 6mm layers stuck together show that the "inside" layer has holes like the "internal" baffle between the drivers. Obviously this effect would be fairly difficult to achieve with a single 12mm baffle as the "holes" would have to be routed to a depth of 6mm...

I'm assuming that actually, these "holes" are not really needed but are a result of you using "copies" of the internal baffle in the sketchup diagram for ease of drawing. Therefore a straight 12mm baffle without 6mm deep "holes" will be fine.....

also

you have also previously mentioned that standard 6mm ply is actually 6.5mm and that may affect the calculations. Am I right in saying that his is no longer an issue?

Getting my ply cut now.....

BJ

Please ask your supplier. 6mm ply is usually 6.5mm. If you don't use 12mm front baffles it will be tricky to get everything right without having to do a 1mm routing.

If you're using 6.5mm ply in double layer, then yes, the holes should be there. They are not accidental. They can be left out with 12mm ply. No need for routing.

Eventually I will update the drawing to be with 12mm front baffle only to remove the immediate confusion.
 

As far as I can tell:

The woofer has 476.8uF in series. This will reduce the hump from the small sealed box and extend the f0/f3 by 20Hz or so. I don't know what the effect is of the second smaller capacitor parallel to the larger one. Any comments on that? No low pass filter so roll-off will be the woofer's natural roll off.

The tweeter has 3.3uF in series. Being an 6ohm load this would result in a 8000Hz first order high pass filter.

I have no idea what the inductor does in series with the tweeter...:eek:
 
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If you're using 6.5mm ply in double layer, then yes, the holes should be there. They are not accidental. They can be left out with 12mm ply. No need for routing.

Thanks, I know its academic because I'm going to use 12mm for the baffles but I'm curious, what is/was the purpose of the holes in the second layer? and why does using 12mm instead mean that they are not neccessary?

Thanks

BJ
 
The tweeter has 3.3uF in series. Being an 6ohm load this would result in a 8000Hz first order high pass filter.

I have no idea what the inductor does in series with the tweeter...:eek:

The choke is simultaneously a resistor. Read the 0.4-0.6 DCR requirement. And a resonant inductor to help the class D amp due to the very low self-inductance of the tweeter voice coils. It's also actually about 7200Hz as the impedance is only nominally 6 ohm. It varies. But really not at all. It's a very soft roll-off that is assisted by the cabinet diffractions and you must not forget the natural frequency response of the drivers either. Speakers don't reproduce flat frequency response curves. Far from it. Please consider all factors that can and do affect reproduction before designing speakers.

I guess I'm asking for when it was 3900hz as you imply?
 
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The choke is simultaneously a resistor. Read the 0.4-0.6 DCR requirement. And a resonant inductor to help the class D amp due to the very low self-inductance of the tweeter voice coils. It's also actually about 7200Hz as the impedance is only nominally 6 ohm. It varies. But really not at all. It's a very soft roll-off that is assisted by the cabinet diffractions and you must not forget the natural frequency response of the drivers either. Speakers don't reproduce flat frequency response curves. Far from it. Please consider all factors that can and do affect reproduction before designing speakers.

Would a resistor in series with the inductor also work? As you said, a inductor with 0.4-0.6DCR is very hard to find, while a low DCR inductor + a simple resistor can be found easily.
 
Thanks, I know its academic because I'm going to use 12mm for the baffles but I'm curious, what is/was the purpose of the holes in the second layer? and why does using 12mm instead mean that they are not neccessary?

Thanks

BJ

Technically. It had 2 functions. One to break up sound waves, and second to increase volume a tiny bit. If you are doing 6mm ply anyways, you might as well do the holes as you can drill them out using the same template as the center braces. If you're using 12mm baffle the effect is so tiny that it's not worth the effort to make the routings.
 
Would a resistor in series with the inductor also work? As you said, a inductor with 0.4-0.6DCR is very hard to find, while a low DCR inductor + a simple resistor can be found easily.

They are not more tricky to find than I could find them on all major electronics suppliers, ebay and aliexpress within 2 minutes.

For example B78108S1153K EPCOS | Mouser
 
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Yes, it is true that when cabinet is basically unknown and thus we don't know exactly what effects it might have then using a 6.8µF on a Dayton ND16FA crossed over to a Monacor SP60/8 is a good starting point that in most cases with achieve an acceptable result.

Here, I know exactly what cabinet it is in, the exact distance between drivers and so on, and therefore I can design the filter specifically for this.
 
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They are more tricky to find than I could find them on all major electronics suppliers, ebay and aliexpress within 2 minutes.

For example B78108S1153K EPCOS | Mouser

Ah, I was looking in the wrong direction. Thanks.

Would a simple panasonic bipolar capacitor suffice for the filter or would you use a audio grade bipolar capacitor?
 
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