Bicycle Trailer / Sub + Stereo system build

[goddestroyer]

Hello, friends. I am an experienced cyclist, audiophile, and mediocre stereo system / speaker builder.

I intend to build a bike trailer stereo system, and I'm prepared to thoroughly research and design the setup.

Main desired qualities in the system will be, in order of priority:
1. power efficiency- best sound for the longest running time off of the most manageable battery
2. bangin-a$$ bass
3. enough mid range and hi end to clearly make out the song that is playing from up and down a block. louder than boom box level, but quiter than rave-level.
4. light weight as possible, though not as important if it sacrifices the above items.
5. anti-theft and durability. This is going to be more of a party-bike setup, so I should rarely ever be away from it when I take it out, but im still planning on bolting down the amp and having metal grills over all the speakers.


I have seen setups before on bikes of a full car stereo head unit running off a car battery, complete with amp and sub. I feel like power could be saved by finding an amp that has both Low Freq/mono sub output and at least a stereo pair of amplified speaker outputs. Then i would simply run an ipod out to RCA inputs on the amp.
- Does an amp like this exist, that is perfect for the application?

I'm probably using some pretty high quality two way 4ohm Focal car speakers that I have sitting around, and I'm thinking a 12 inch sub in a quality pre-built ported enclosure.

My design is currently leaning towards downfiring the sub towards the street, with a trailer design that is open to let the sound blast through. this will keep the sub more protected from damage and theft, too.

So I guess to be more pointed I am mainly looking for amp and battery advice for such a setup, as I have built a good deal of speakers, car systems, and home systems, but the amp and battery are central to this particular design.

Please discuss some models I should look into. thanks guys!

[Pete Schumacher ®]

http://www.parts-express.com/project...roject=Podzuma

[john trials]

I'm curious: What is the intended usage? When, and how often would you use such a trailer?

[jclin4]

One possible use: ride to the park to meet your friends for a Sunday barbeque. Listen to your favorite tunes while the goat meat grills!

[fbov]

Or maybe these kind of events:
http://www.denvercruisers.com/

1. power efficiency-
Go pro speakers, digital amps. Here's a thread on one good amp option; the clones are affordable.
http://www.avsforum.com/avs-vb/showthread.php?t=1334237

2. bangin-a$$ bass
Aint happenin' outdoors. Ask the pro sound folks what it takes to get 120dB at 50Hz without walls. They all use horns, which are only loud in one direction. Don't aim deep, and add a peak; you'll get a thump that propagates, but no subsonoics. Think 50Hz with a peak just before it falls off, crossed fairly high since you're co-located, perhaps 150Hz?

3. enough mid range and hi end to clearly make out the song that is playing from up and down a block. louder than boom box level, but quiter than rave-level.
The question here becomes both up and down the block? Again, really high output comes from controlled directivity, either up the block or down, but not both... unless you make it a 4 channel system. Aim each channel 90* from the other and alternate L-R-L-R. With CD drivers, you won't hear the ones not aimed at you, so everyone hears stereo.

4. light weight as possible, though not as important if it sacrifices the above items.
Neodymium magnets weigh less but cost a lot more. Lead-acid deep cycle batteries have great reserves, but weigh a ton.

One strong recommendation is to put the mass as low as you can, for stability.

5. anti-theft and durability.
That's up to you... and there are other folks who've done this; look up their sites and threads, if you haven't already.

Needless to say, the hardest part will not be choosing drivers but integrating them so they play nicely together. You may want to consider an active XO so you can tweak as needed.

HAve fun,
Frank

[DanP]

Don't aim deep, and add a peak; you'll get a thump that propagates, but no subsonoics. Think 50Hz with a peak just before it falls off, crossed fairly high since you're co-located, perhaps 150Hz?

+1 to that. You're not going to be able to get efficiency from the speaker without sheer size, but you can trick the listeners into thinking the bass is louder than it is by following Frank's advice.

Some "tricks" you can use are:

Make the speaker enclosure as big as you can without compromising your other requirements- if you do it right, this will translate directly to efficiency.

Don't waste energy as heat - use class D amps or something similarly efficient.

If you can afford to trade cost for weight, use Lithium Ion batteries. Otherwise, car batteries are a great bang for the buck.

Using a bandpass alignment for the subwoofer will offer the ultimate in protection and the large degree of flexibility inherent in the design can be used to tailor the bass hump.

This sounds like a very cool project. Post pictures as you build it.

Dan

[goddestroyer]

@pete: podzuma looks pretty cool, but I can already tell its not going to have the bass I am after. I am going to be playing predominantly houston gangster rap on the system, and it simply has to slap the block. I dont think any integrated speaker combo is really going to do the trick for me.

@john_trials: Intended usage? in my younger days I had cars with totally bangin systems, in fact that was the only thing that kept me in cars for a few extra years, but alas I am a tree-hugging hippie and I live car-free. Bikes everywhere, for everything, all the time. The sub-trailer is going to come with me on practically every trip out that is not commuting to work and getting groceries. every joyride and day ride with friends, as well as critical-mass style group rides. and yes, BBQs in the park to pick up some strange

@fbov: as for being heard up AND down the block, I was speaking figuratively, the design i've been drawing up so far has the speakers pointing out about 30 degrees from straight, each.
And I agree with your ideas about the low-ends, which is why i'm leaning towards a big ported box enclosure, and my unfounded theory that if i downfire the sub, it will hit the street and travel out, vs if it was just pointing outwards it seems like the bass waves would diffuse faster into the open air. Think there's any merit to that?
batteries- Im all open and ready for any of your recommended battery links, as my only experience with Li batteries is in laptops and video cameras.
its not the end of the world if i have to use a full on lead acid battery, at the end of the day sound is more important than weight for this.

I will definitely update this thread with my progress, soon I will post my sketches thus far. Here is one of the bikes I will cruise this on:

[andykriech]

Here is one of the bikes I will cruise this on:

Ahh...StingRay, banana seat and a sissy bar...brings back memories from way back...

[goddestroyer]

hell yeah, mane. that was a custom build too from an old salvaged rusty frame. had a buddy powdercoat it candy black.

I'll also be pulling the stereo on a regular road bike and touring bike and basically whatever bike.

[duanebro]

I second the bandpass idea. And a deep cycle battery.

[goddestroyer]

I second the bandpass idea. And a deep cycle battery.

Do ya'll have any battery charger suggestions? that is also an area I don't know anything about (yet) since my systems have previously been in cars. I would like to spend most of my budget on the audio components rather than the battery and charger, so I just need the cheapest charger that can fully do the job.

[goddestroyer]

Here is the very early general idea.
Main research points I'm trying to solve:
- is there an 4-channel amp that can independently eq or low-pass its different channels, so i can dial the sub in independently of the speakers?
- if not, what would be the best component to employ between the amp and drivers, to independently eq each stereo channel pair?
- is there a way i can make the 4-speaker setup work as shown, or would that require all 8ohm speakers? (i have pretty much the 4 speakers pictured, sitting around)

I'm kind of just sharing my research as I go here, anf maybe someone will chime in with something useful that saves me time. thanks!

[duanebro]

I think most 4 channel amps can do that. Do you have a budget for this project?

[bkeane1259]

I think you're heading in the right direction for sure.

There are a number of car audio amps that will do what you want. Just get a 4-channel amp with filter controls that is 2-ohm stable and you will be set there. Channels 1&2 will drive your 4 coaxial drivers in parallel (2ohms) and the sub can be bridged across channels 3&4 (I'd keep the load at 4ohms there).

THIS AMP will accomplish what you're thinking for a pretty low price point.

Manufacturer's link: http://www.poweracoustik.com/pa2012/...mf-1600-4.html

EDIT-- I'm not an electrical engineer, so I would seek some advice from the electrical gurus around here as to how long your battery will last with such a setup. I'm thinking a class A/B amp driven at high volume might drain a battery quicker than you'd think, so please look into that.

[Brian Steele]

Please discuss some models I should look into. thanks guys!

So, you're looking for something like this then?

[goddestroyer]

Thanks for the links, I'll check it out. So far its seemed like D-amps are the way to go for sure.

Been randomly looking through 4-channel D amps, but I havent conclusively seen one that can independently EQ each stereo pair...

budget: ~$1k, but I'm trying to go as thrifty as possible UP TO that amount. Since I don't use cars it's really liberating to not pay dmv fees, gas, parking fees and tickets, maintenance, insurance... being free of all that allows me to blow cash on fun crap like this.

[goddestroyer]

@brian - yeah that is in all reality not too far off from what im going for, but I will have less than 8 speakers, and no horns. Aiming to be about half that size, and look a whole lot prettier.

[bkeane1259]

They are out there....JL makes exceptional Class-D amps but you will pay much more for that quality. Not sure if you wanna put that into a bike setup, but if your budget is $1k, then $300 for the amp is not out of line.

http://www.amazon.com/NexD-XD400-Car...ata/B0039AQVEM

[duanebro]

http://www.sonicelectronix.com/item_...er-P900.4.html

I like this one. I think it used to be about $199. As a bonus it is very small.

[goddestroyer]

Great, dude! Thats the best one ive seen so far, meets so much of what im looking for! That might just be the one!