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12v bike trailer system (help needed)

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Topic: 12v bike trailer system (help needed)
Posted By: Goegon
Subject: 12v bike trailer system (help needed)
Date Posted: 27 July 2019 at 4:17pm
Hello,

I am planning on building a small 12 v soundsystem that can run a night on a car battery. It will be mounted on a trailer on a bicycle. (maybe I'll need a tandem because i think total weight will be quite a lot) It will be my first rig i build and after a week of researching I'm still quite in the dark. Bear in mind i still don't fully understand everything i need to know.

So far i was thinking of using a Tham18, a SMT212 and 2 tweeters (Beyma CP22), i guess i wil need a 3 way crossover to divide the 3 boxes (if someone has recomendations regarding this, happy to hear). And as far as i understand I'll need an amp for my sub and then like a 2 channel amp, 1 for the 12" drivers and 1 for the tweeters? Again if someone knows affordable D class amps that would fit here, i'd love to know.

All of the drivers i chose (the cabinet's recommended drivers basically) have a sensitivity above 90 Db so that should be okay right?
Yet if i put the RMS of just the subwoofer in a calculator it says i can run it 0.42 hours with a car battery. :s my guess is i just don't know enough about wattage use Tongue

What else would i need to make this system function? I'm talking bout all the little stuff no one talks about but are just as essential.

I hope someone here can help me out a bit  ^^

Thanks!



Replies:
Posted By: markie
Date Posted: 27 July 2019 at 7:17pm
First I doubt whether even a Tham 18 will keep up with a 2x12 mid top. Go for a single 12 + HF. Then to save weight just use 1 amp, 1 side for bass and the other for mid/top. Use a passive crossover in the mid/top.

Having saved the expense and weight of an amp and 1/2 the 2x12, Spend the saving on neo drivers (that will save your legs).

To save even more weight you might consider a Cubo 15 instead of the Tham 18. This will play slightly higher allowing you to use a decent 10" in the mid/top cab. Likewise the 10" will play a little higher so you can use a smaller/lighter/cheaper HF.


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If it's got wheels or tits it's gonna cost a fortune


Posted By: toastyghost
Date Posted: 27 July 2019 at 8:27pm
You won’t be driving the sub with anywhere near it’s RMS (or more likely, AES) rating for any considerable length of time. 1/8th of that is more likely, up to 1/4 if you really push it.


Posted By: Goegon
Date Posted: 27 July 2019 at 9:56pm
Originally posted by markie markie wrote:

First I doubt whether even a Tham 18 will keep up with a 2x12 mid top. Go for a single 12 + HF. Then to save weight just use 1 amp, 1 side for bass and the other for mid/top. Use a passive crossover in the mid/top.

Having saved the expense and weight of an amp and 1/2 the 2x12, Spend the saving on neo drivers (that will save your legs).

To save even more weight you might consider a Cubo 15 instead of the Tham 18. This will play slightly higher allowing you to use a decent 10" in the mid/top cab. Likewise the 10" will play a little higher so you can use a smaller/lighter/cheaper HF.


Thanks a lot for the recomendations, makes way more sense indeed! :)


Originally posted by toastyghost toastyghost wrote:

You won’t be driving the sub with anywhere near it’s RMS (or more likely, AES) rating for any considerable length of time. 1/8th of that is more likely, up to 1/4 if you really push it.


Okay, after another google search i realize i misinterpreted the term RMS, thanks for clearing that up. :)


Posted By: imageoven
Date Posted: 28 July 2019 at 1:15am
You don't want to use a car starter battery, they are designed for lots of current quickly, whereas you need fairly low current for a long time. Read up about leisure batteries (last much longer). Then read up about the various Lithium batteries (much lighter but more expensive and with other more complex issues)


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Keep pushing on, things are gonna get better.


Posted By: SamV
Date Posted: 28 July 2019 at 2:05am
You want class D amps, I'd use a minidsp + chip amps at around 36v. More expensive but maximises efficiency. But then just getting a car amp and a 120ah battery will sort you for the night anyways at loud enough volumes. Start with a leisure battery, think about lithium later, there's a bit of a learning curve to doing it safely. But if you do really want to go that way you can get decent units built for electric bikes for under a grand.


Posted By: studio45
Date Posted: 28 July 2019 at 12:35pm
First off, great idea :) Bike trailer rigs rock!

You're pretty brave to be considering a THAM18 bin - those things are really big! Have you thought about how it will ride on the trailer?

I would suggest downsizing your plans a bit. Most bike rigs have a 12 or 15 inch bass bin and 8 or 10 inch mid-tops. You've got to consider getting the thing through standard 600mm doorways, and not having it so tall that it tips over when you try to go round a corner! Difficult with an 18" bin. It's less of a problem for it to be extra long, than to be tall or wide. 

The Carryfreedom "Bamboo" trailer design is pretty good, and easy to make. You can change the size to suit what you're putting on it. Or, consider a monocoque design - ie the wheels and towing arm are attached directly to the bass bin, which forms the structure of the trailer. 

You will want to be able to have the mid-tops "down" for transport and "up" for playing out. You can do this with top-hat fittings and two different lengths of 38mm pole, or you could have the mid-top on a hinged or telescopic pole that can move up and down, and lock in place.

Pioneer and Alpine make good Class D amplifiers. Or the other option is to buy amplifier and power supply modules from eBay, or a supplier like Wondom (aka Sure Electronics). This can work out a little cheaper but you then have to make a box for them (or mount them inside your speakers....) and wire them up, provide a volume control, crossover etc....

Don't get carried away with your power requirements. Sure you will probably end up using a bass driver that can handle 1000 watts. But 150 watts of real power is actually plenty to get such a driver pumping and - assuming an efficient design like a tapped horn - can easily get you to SPL's of over 110dB at 1 metre. You absolutely don't need a 1000 watt amp (and a REAL 1000 watt 12v amp will be huge, expensive and difficult to find)

If you have about 300 watts of real power from your amp, and it is about 70% efficient (a generous figure) you will be pulling an average of about 4.5 amps from your battery, so a 75Ah leisure battery should last about 16 hours (based on a figure of 12.5% average vs peak power) But you generally don't want to run your battery all the way flat, so expect about 8 hours of full-beans continuous use - more if you play at lower volume.

If you get an amp without such functions built-in, you'll need some kind of processor or crossover too - a lot of people use the MiniDSP. They are pretty cool because they power up from 5-24v, they come prebuilt and ready to work and you can change your system configuration quickly, but they have some disadvantages - they cost quite a bit, there's no limiters or compressors in them, and the output level is disappointingly low, so in a lot of cases you need a set of gain boosters between the DSP and the amps. Also consider the FreeDSP and Wondom JAB boards (all use the same Analog Devices ADAU1701 chip.)

I've had good success using analogue line-level crossover modules, eg there is a good board from XKitz that powers from a single +12v supply and can be easily configured to the frequencies you want. Or there is a guy called KMTech who does nice 3 and 4 way boards but you do need to arrange a +15/0/-15v supply for them. Again there's small modules you can buy on eBay that do just that. The analogue boards can't be adjusted on the fly of course, but offer superior input/output level capability and lower cost than the DSP solution.

Good luck with it bro! Would love to see some pics when she's ready ;)


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Studio45 - Repairs & Building Commotion Soundsystem -Mobile PA


Posted By: Goegon
Date Posted: 28 July 2019 at 1:15pm
Thanks a bunch for your input studio45.

Yeah i realised quite soon after i wrote this that 18" is quite a bit too large ^^ Now i'm thinking of building a tham15, and then just buying a decent full range 8" or 10" speaker since it looks like there's models out there that are quite decent for a price you couldn't build your own with. Was thinking of something like a turbosound iP82.  maybe add a tweeter or two.
Edit: Or instead of a turbosound i will go with one medium quality 10" woofer and 2 tweeters in a self build box, looks like more fun to me.

Prices of somewhat sturdy bike trailers are way to high in my eyes so i think i will weld one myself at a friend's workshop, the bamboo design is interesting but i don't know if i would trust it completely with expensive gear on it.  A monocoque design could prove useful too.

I'll have to do some digging to find an amp that suits me. Since I'm very new to all of this I'm gonna look for one that has build in crossovers, volume control etc. The less I do the less i can do wrong LOL
Edit: I'm going to try to figure out how to build an amp and crossover that fits this project, will be less expensive, better optimised and i will learn more like this.

As for battery i currently have my eyes on this VRLA gel accu: https://www.accuserviceholland.nl/gel-12-100-vrla-lpcg-accu-12-volt-100-ah.html
As far as i understand you're allowed to drain it to 20% which means almost twice the party ^^

Right now the project is still in the mental phase, but after august I'm gonna start building it. Looking forward to it a lot, I'll definetly keep you updated with pics when the time is there :D


Posted By: studio45
Date Posted: 28 July 2019 at 2:00pm
I should add that you obviously don't build the trailer out of *bamboo*! I used 20x20mm square steel tube and a MIG welder. It is very strong. Old school/office desks are a good source of such tubes ;)

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Studio45 - Repairs & Building Commotion Soundsystem -Mobile PA


Posted By: Goegon
Date Posted: 28 July 2019 at 4:05pm
Okay that sounds way less wonky already xD


Posted By: Goegon
Date Posted: 29 July 2019 at 1:28am
Oof, so after a lot of searching i think i settled on driver choice...
One Tham15 loaded with Kappa PRO LFA-2 15"
and one top cabinet loaded with Beyma 8BX 8" and Beyma CP25.
for the tops I'll use a miniDSP 2x4 and let them crossover at ±5,5Khz
can i use the same miniDSP for the sub aswell?
Edit: or should i be looking at 4 ohm drivers instead?

Apart from the drivers i think the chain will look something like this:
110 Ah Gel battery -> circuit breaker -> car head unit -> miniDSP -> amplifiers -> speakers

does all that look somewhat okay? Please share your thoughts.
As for amplifiers I'm still too confused about them to settle on some...

Here are the links to the speakers in case you want to see the specs:
http://www.bax-shop.bel/15-inch-luidsprekers/eminence-kappa-pro-15-lfa-2-luidspreker-15-inch - https://www.bax-shop.be/nl/15-inch-luidsprekers/eminence-kappa-pro-15-lfa-2-luidspreker-15-inch
http://www.bax-shop.bel/8-inch-luidsprekers/beyma-8bx-professionele-coaxiale-luidspreker - https://www.bax-shop.be/nl/8-inch-luidsprekers/beyma-8bx-professionele-coaxiale-luidspreker
https://www.bax-shop.bel/tweeters/beyma-cp25-professionele-compressie-tweeter - https://www.bax-shop.be/nl/tweeters/beyma-cp25-professionele-compressie-tweeter


Posted By: slaz
Date Posted: 29 July 2019 at 11:45am
Originally posted by Goegon Goegon wrote:

Oof, so after a lot of searching i think i settled on driver choice...
One Tham15 loaded with Kappa PRO LFA-2 15"
and one top cabinet loaded with Beyma 8BX 8" and Beyma CP25.
for the tops I'll use a miniDSP 2x4 and let them crossover at ±5,5Khz
can i use the same miniDSP for the sub aswell?
Edit: or should i be looking at 4 ohm drivers instead?

Apart from the drivers i think the chain will look something like this:
110 Ah Gel battery -> circuit breaker -> car head unit -> miniDSP -> amplifiers -> speakers

does all that look somewhat okay? Please share your thoughts.
As for amplifiers I'm still too confused about them to settle on some...

Here are the links to the speakers in case you want to see the specs:
http://www.bax-shop.bel/15-inch-luidsprekers/eminence-kappa-pro-15-lfa-2-luidspreker-15-inch" rel="nofollow - http://www.bax-shop.bel/15-inch-luidsprekers/eminence-kappa-pro-15-lfa-2-luidspreker-15-inch - https://www.bax-shop.be/nl/15-inch-luidsprekers/eminence-kappa-pro-15-lfa-2-luidspreker-15-inch" rel="nofollow - https://www.bax-shop.be/nl/15-inch-luidsprekers/eminence-kappa-pro-15-lfa-2-luidspreker-15-inch
http://www.bax-shop.bel/8-inch-luidsprekers/beyma-8bx-professionele-coaxiale-luidspreker" rel="nofollow - http://www.bax-shop.bel/8-inch-luidsprekers/beyma-8bx-professionele-coaxiale-luidspreker - https://www.bax-shop.be/nl/8-inch-luidsprekers/beyma-8bx-professionele-coaxiale-luidspreker" rel="nofollow - https://www.bax-shop.be/nl/8-inch-luidsprekers/beyma-8bx-professionele-coaxiale-luidspreker
https://www.bax-shop.bel/tweeters/beyma-cp25-professionele-compressie-tweeter" rel="nofollow - https://www.bax-shop.bel/tweeters/beyma-cp25-professionele-compressie-tweeter - https://www.bax-shop.be/nl/tweeters/beyma-cp25-professionele-compressie-tweeter" rel="nofollow - https://www.bax-shop.be/nl/tweeters/beyma-cp25-professionele-compressie-tweeter


I'd agree with studio45's comments on just about everything .... here's a few of mine.

keep it simple as possible for a first-time setup.

Use a 12 or 15 bass box yes .... (i'd go for a good 12 myself) .... THAM 12 would be great.
But use e.g. 12mm ply and use some clever bracing to keep the weight down. Buy an off-the-shelf plastic mid-top (mebbe a EV ZX1 or similar) and use its built-in passive Xover.
Get a 4ch classD car amplifier (Pioneer, Alpine etc.) but use it as 4ch bridged into 2ch .... this gets you a good impedance match for 8 ohm drivers.
You can then use the ampifiers built-in Xover to cross between bass and mid-top. Ideally find an amp with variable HPF to suppress very low bass e..g below 50Hz (can make a big difference to battery life without sacrificing much subjective bass extension). It won't be as capable as a mini-DSP wrt Xover slopes etc. but _can_ still work quite well. DSP could be added later.

Construction-wise .... make sure to keep the CoG (centre-of-gravity) as low as possible.
Consider mounting some parts on the bike itself (e.g. amplifier, other bits of electronics).
Use a phone/tablet as music source ... a car-head unit will likely be too current-hungry.

When you've done principle contruction of the bulky stuff, take some time in quiet streets somwhere to practice handling the trailer - braking, emergency stops, evasive action in traffic, dodging pot-holes etc.
Don't underestimate the awkwardness of that amount of weight behind a bike .... it can take some getting used to.



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REMEMBER....POLITICIANS AND DIAPERS SHOULD BE CHANGED OFTEN AND FOR THE SAME REASON


Posted By: Goegon
Date Posted: 29 July 2019 at 1:37pm
Thank you so much for this really helpful post Slaz!
I feel like it's starting to come together.

I'll use a tham12 loaded with a B&C 12NDL76 because of it's 100Db sensitivity.
Then as you suggested the ZX1-90 8" because it's the lightest i can find.

A suitable car amp i found is the Alpine KTP-445A. it's a 4 channel amp with 45Watt per channel at 4 ohm, so that should give me enough power when i bridge it i think.
That amp doesn't have eq / filters as far as i see but a friend said he'll help me with making a passive crossover for the sub/mid. So let's see if that works out :)

For the battery i think i'll buy a VLRA 110Ah gel battery, should last me long enough if i don't cranck it up.

Will that + a circuit breaker for safety have me settled? Any other things i must consider? Like i heard you need to use thick wiring etc... Anything a noob like me might forget! LOL




Posted By: slaz
Date Posted: 29 July 2019 at 2:13pm
About car amplifiers in general .... they're nearly always rated with a supply of 14.6 V or so (as from the car's alternator/charging system) - but when you're using it as stand-alone, your mean supply voltage is more like 12.5V (starting from just over 13V and dropping to about 11.5V at end of discharge cycle. So because power relates to square of voltage, that equates to about 70% of the rated power.

So your 90W of bridged power is actaully about 65W.

I'm pretty sure Pioneer does an amp with 4 x 80W -> 4R or so .... worth having a bit more headroom with about 2 x 120W.

Oh yeah - another thought ....
If you have mains power close to where you're gonna store the rig - no problem, but if you have to lift the battery out to charge it, you (well, your back) will start cursing it pretty soon. Try to make everything easy-ish to remove from the rig for testing/trouble-shooting purposes.


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REMEMBER....POLITICIANS AND DIAPERS SHOULD BE CHANGED OFTEN AND FOR THE SAME REASON


Posted By: markie
Date Posted: 29 July 2019 at 2:18pm
Passive crossover from sub to mid is not a good idea. To get even close to good performance you'll need a huge inductor, expensive caps, and it won't even be close results wise to an active. You'll lose a lot of your already limited power.

Passive mid/top is fine, passive sub/mid, don't waste your time.


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If it's got wheels or tits it's gonna cost a fortune


Posted By: studio45
Date Posted: 29 July 2019 at 2:18pm
I'd also look at smaller batteries than a 110Ah monster. I stoat about with little 16Ah units, like you'd get in a mobility scooter or golf trolley. I carry one spare in my pannier, and I've never run out of juice in the middle of a gig yet! 
A 110Ah is 25kg on its own - you want to try and keep your trailer weight below 50kg, so that doesn't leave a lot of weight for wood and drivers...


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Studio45 - Repairs & Building Commotion Soundsystem -Mobile PA


Posted By: slaz
Date Posted: 29 July 2019 at 2:39pm
Good point. Try to make your system accomodtae (in some way) different size/shapes of batteries.
See if you can rope your mates into carrying extra batteries on their bikes !

Incorporate a voltmeter into your amplifier setup so you can keep an eye on it.


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REMEMBER....POLITICIANS AND DIAPERS SHOULD BE CHANGED OFTEN AND FOR THE SAME REASON


Posted By: Goegon
Date Posted: 29 July 2019 at 2:51pm
Originally posted by studio45 studio45 wrote:

I'd also look at smaller batteries than a 110Ah monster. I stoat about with little 16Ah units, like you'd get in a mobility scooter or golf trolley. I carry one spare in my pannier, and I've never run out of juice in the middle of a gig yet! 
A 110Ah is 25kg on its own - you want to try and keep your trailer weight below 50kg, so that doesn't leave a lot of weight for wood and drivers...


I was worried about the running time but maybe unrightfully so.
But running at 100 watt on a 16Ah will give me close to 1 hour according to https://mbharris.co.uk/12-volt-sound-system-battery-calculator/ (?)
I plan on using this for small free parties, i'd like to get at least 6 hours out of it...
I had a limit of 80kg in mind, i won't be partying alone so i could switch bikes with a friend if it gets too tiresome. Maybe I'm being unrealistic. But you think 2 x 16Ah batteries will get me to 6-8 hours?




Posted By: markie
Date Posted: 29 July 2019 at 3:19pm
Bear in mind that the online calculator assumes a continuous load. Music is not continuous. Every time the kick drum comes through you will be on peak load, but in between each beat the load will be considerably less. The actual time  (depending on music content0 will possibly be 2/3 times as long as if the load was continuous.

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If it's got wheels or tits it's gonna cost a fortune


Posted By: toastyghost
Date Posted: 29 July 2019 at 4:16pm
Originally posted by markie markie wrote:

Passive crossover from sub to mid is not a good idea. To get even close to good performance you'll need a huge inductor, expensive caps, and it won't even be close results wise to an active. You'll lose a lot of your already limited power.

Passive mid/top is fine, passive sub/mid, don't waste your time.



You can get around that by putting the filter set for the sub channel(s) before the amp, instead of in the sub. Same for the HPF on the passive mid-high channels.


Posted By: studio45
Date Posted: 29 July 2019 at 6:32pm
As in "passive line level"? Probably not a good idea for 12v applications, as there's always some insertion loss with passive filters and you're usually struggling for enough signal level from the source anyway! Could use gain blocks to get it back of course, but that means extra hissssss

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Studio45 - Repairs & Building Commotion Soundsystem -Mobile PA


Posted By: mobiele eenheid
Date Posted: 29 July 2019 at 7:06pm
Most stereo information is in the mid range, so you could use one output for sub, 1 output for both the 1" drivers in the coax and use the remaining 2 outputs for stereo left and right from the 8" Beyma's.

Alternatively you could use a passive filter for the 8"/1" coax (~ 2.5 kHz) then use 1 output of the miniDSP for the sub, 2 outputs for the 2 coax tops and the remaining output for the intended slot tweeter (personally wouldn't use those) or as monitor.


Posted By: lola_handycam
Date Posted: 12 April 2020 at 12:30pm
Ho Geogon, 
Would it be possible to hear from what you managed to build ? even get photos or link to facebook maybe ? I'm currently in the situation of building something similar and would love to hear experience feedback ! 
Does it fits the belgian gabber rave standards ? haha 
Cheers !
https://forum.speakerplans.com/member_pro.asp?PF=22916 -
https://forum.speakerplans.com/search_.asp?USR=Goegon -




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