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Building custom (Half) Boominator (first project)

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thevox View Drop Down
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    Posted: 12 July 2020 at 2:46pm
Hi Smile
I'm planning to build a custom battery powered boominator-like speaker made for the outdoors. While I I understand a bit about speakers, audio and electronics I'm completely new to this. I would really appreciate some feedback :)

I have based my plans of other peoples plans of the boominator and read a lot of Saturnus's posts. Here are the plans (some questions inside there):

Plans:


Box

Plywood Box (10+ mm, 7+ layer) 

54x30x40 or bigger (64.8 L- 80 L) I might make it slightly larger if needed but

Screws

Sandpaper


Soundproofing (stuffing, waterproof-ish) inside box


Vent tube (bass reflex) - 2x (Diameter: 53mm x 10-54 mm) // Bass Reflex 2x Handles 60x100mm len: 20mm


I've tried using some software (Basta!) to make better decisions :)

But I'm kinda stuck on how to tune(?) calculate optimal port size/length. I want to focus on the 80-100 hz range.


Waterproof box inside for electronics (thinking of some kind of lunchbox with some screws)


Metal Woofer Grill 10”-12” (2x)


Speaker Drivers


Woofers (2x): P.audio HP-10W

96 dB/w, 10”

Max. 100W, 8 Ω

50-4000 hz (90-3000hz crossover)


Tweeters (2x): Monacor MPT-005 (?)

94 dB/w, 85x85mm

Max. 115W, 4-8 Ω

4000-20000hz (3500hz crossover)

Resistor/Capacitor protection and high pass

Resonance fix (fill up grooves with sealant acrylic?)




Electronics


Amplifier (min. 30W 4-8 Ohm, 90%+ efficiency, class T/D)

Alternatives: Lepai 2020/2024A

TDA7498 based

TA2020 based


I'm planning to get a lot of my electronics from AliExpress

Battery

Type: SLA, Deep-cycle Marine Battery / LifePo4, LiPo (not preferable?)

I think Sealed Lead Acid batteries seem like a good option (cost/size/power).

Capacity: 7-14 Ah (2x parallel 7Ah)

Voltage: 12v (cut off at ca. 11.5v)

Est. battery life: 50 h ?


DC Power Supply (12v, 6a?) - Can I buy a high amp psu? Does this impact anything other than max potential power?

^ C13 Connector (with rubber cap?)

Copper cables, high gauge


Battery Management System

Normal battery protection (over-, discharge protection, etc.)

automatic DC switch & charging


  • Voltage boost converter on DC power (boost volume)


^ I'm a bit lost here (BMS), I can't seem to find a good option here or how to build this system (I don't mind using a manual switch for charging/switching/boosting but I'm trying to aim at foolproof system but im a newbie so easy is also good)

Thank you in advance! Tongue 
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lutkeveld View Drop Down
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Post Options Post Options   Thanks (1) Thanks(1)   Quote lutkeveld Quote  Post ReplyReply Direct Link To This Post Posted: 12 July 2020 at 3:29pm
Your pictures dont work :)

Sure Electronics has the BCPB2 and BCPB3, which allow you to make a 21V lithium pack. Lighter weight, built in protection and no need for a boost circuit :)
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thevox View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote thevox Quote  Post ReplyReply Direct Link To This Post Posted: 12 July 2020 at 3:37pm
Sorry here are the pictures in order.
https://gyazo.com/932180c3dc4cf21fdb1550d03348ac65 - https://gyazo.com/932180c3dc4cf21fdb1550d03348ac65
https://gyazo.com/19d63c6d6b64f181858495a47952cf21 - https://gyazo.com/19d63c6d6b64f181858495a47952cf21

Thanks for the suggestion. The Sure Electronics (BCPB2/3) BMS looks good, but because of cost/cap and dangers of Lipo I'd rather use 12v Lead Acid or marine batteries.
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thevox View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote thevox Quote  Post ReplyReply Direct Link To This Post Posted: 12 July 2020 at 3:38pm
I've seen and read a lot your posts lutkeveld SmileHeart


Edited by thevox - 12 July 2020 at 3:39pm
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lutkeveld View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote lutkeveld Quote  Post ReplyReply Direct Link To This Post Posted: 12 July 2020 at 5:33pm
The Halfinator is not meant to face one way. The design is meant to be bipolar with the magnets glued to a centre brace.

Have you seen my Halfinator build? You can see some of the techniques and electronics I used.

Lithium is not really dangerous if its properly protected. Most horror stories are from the RC world where people pull 100+ amps current without protection. All phones, laptops etc use lithium.

But lead acid also okay and indeed cheaper per Watthour.


Edited by lutkeveld - 12 July 2020 at 5:33pm
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thevox View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote thevox Quote  Post ReplyReply Direct Link To This Post Posted: 12 July 2020 at 6:02pm
Sorry for the stupid question, but are there any benefits of this bipolar design, in regards to sound/power, outside of the more spread sound (360)?

Benefit from magnets across from each other?
Are the bipolar speakers in your build in phase or out of phase?

Basically, how stupid is it to face them both forwards?
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lutkeveld View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote lutkeveld Quote  Post ReplyReply Direct Link To This Post Posted: 12 July 2020 at 6:12pm
The main benefit is two-fold:

1) Bipolar speakers dont need baffle step correction:
High frequencies beam in one direction, while low frequencies spread omnidirectionally.
Because the low frequencies spread around, they will have half the power of the higher frequencies if you measure it at the front side.
However if you have another speaker on the other side doing the same thing, you counter this effect.

You can correct this effect with a DSP. If you dont, the bass will be lacking compared to a bipole construction.

2) Bipolar speakers are stronger/stiffer:
Because of the magnet to magnet construction with the centre brace, the construction is much stronger. However, if the speakers face one way you can still get adequate strength with enough bracing and/or thicker plywood.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote thevox Quote  Post ReplyReply Direct Link To This Post Posted: 12 July 2020 at 6:23pm
Thank you so much for clarifying! Smile I will look at changing my design

In this bipolar configuration, do you connect both of the woofer the same (+/-)? Same phase?
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lutkeveld View Drop Down
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Post Options Post Options   Thanks (1) Thanks(1)   Quote lutkeveld Quote  Post ReplyReply Direct Link To This Post Posted: 12 July 2020 at 6:33pm
Same phase wiring to the amp indeed. That way they move outwards/inwards compared to the centre of the speaker at the same time. 
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