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Help for Project: Horn OR 6 Order Bicycle 12V Sub?

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    Posted: 07 June 2018 at 5:17pm
Greetings! 

I've read forum posts back and forth the last weeks but couldn't find threads that fits my situation / project - so i'm hopying someone with some experience can give me a hint/oppinion what would be worth to work on the next weeks:

My plan is to build a Subwoofer on a Bicycle. First i was crawling the web to find some plans that would accidentally also fit on a bike (for example  https://www.freespeakerplans.com/plans/14-plans/basscab/24-mth-30 - MTH-30) but it was all not really suitable. So i decided to come up with a construction that fits on all bicycles if you got a decent front carrier. 



Conditions for the Bicycle Sub:

- I'm aiming for a 12" or 15" sub
- It's running outdoor only! (most 12V subs are tested in / build for cars but that will not suit my situation as it must be able to produce low bass in an open area)
- It should play Reggae/Steppas/Dub/Dubstep - so it should run between 30 and 80Hz if possible, starting from 40 Hz would be a compromise (that i can't avoid i guess).
- Max SPL is not the most important thing. Most of the time you should be able to still talk to each other if you're riding next to each other. Playing deep is more important. Nevertheless people within a 6m radius should be able to enjoy the bass while riding.
- It will be powerd by a 12V car battery
- I want to take it on long cycle tours (several months) so i'm planing to get a solar pannel to charge the battery (morning) and empty the battery in the afternoon -> So efficiency is a big deal here!
That's why i'm looking for a Horn / 6th Order design instead of just putting 2 18" to each side of the front carrier!
Efficiency is also the reason why i'm trying to get the mouth of the sub as close to the street as possible.
- Durability is also important. I decided for Horn / 6th Order designs instead of a simple bassreflex design so the chassi is protected from wet conditions. The best would be, if it would be able to operate during rain too. Also bounces during operation are to consider. 
- The sub mouth should face to the back (if possible) (because if it faces to the front wind (and rain) gets in, if it's facing to the side energy is wased because most of the time you are riding in a row instead of next to each other if you're in a group of cyclist)


This would be the dimensions (doted are the max dimensions if i would push it to the limits (nececy for all desings instead of one as i recognized later):

(one square is 5cm in reality)













So: After reading i came up with 2 options (but i'm open to everything else too!)

6th Order Bandpass:
Pro:
+ Relative small designs could also be tuned deep (compared to horn)
+ The chassi would be protected well against rain / dirt
+ I read it got 3db more SPL than BR designs - i'm not aiming for Max SPL, but i thought having 3db more SPL on half power would also make it more efficient, right?
+ Doesn't need to be played in group to get low.
+ If i read it right i could also put a good 12" in a box tuned to 32HZ and it would deliver that low bass (hard to reach with horn design)

Cons:
- Bass wouldn't be that clear
- I read it's hard to know if it's distroying itself, plus you need a high pass filter to cut frequencys under the tuning frequency
- Long group delay - but because reggae got's long basslines i don't think it would be too important here (for example compared if i would like to listen goa bassdrums through it).

Questions:
- Do you think the "dump bass" of a 6th Order desing would be so bad that it's not suited for a Reggae Bassline? (for example this one: https://www.youtube.com/watch?v=VxXWJ_wO3ZE)
- Is a 6th Order design also good if runed on 12V and half power (not pushed to the limit)?

Ideas:
Saw this plan in the web:  http://https://www.poweraudio.ro/diy/albums/userpics/10001/BP12.pdf - https://www.poweraudio.ro/diy/albums/userpics/10001/BP12.pdf (but i would need deeper tuning - so this would be more like this:  http://www.lean-business.co.uk/SPEAKER_PLANS/18_12_bandpass.pdf - http://www.lean-business.co.uk/SPEAKER_PLANS/18Sound_12_bandpass.pdf)


So this would be a quite Compact 12" design - Read somewhere that people tunes a 31l front chamber to 52Hz and a 64l chamber to 32Hz and that are the volumes i got too! Thus i would make the front chamber smaler so it got a 64Hz tuning as i read 1:2 would be a god ratio(?):





Now i tried to stuff a 15" in it - it is possible if you but it in diagonal. Because you can't see it well on the scetches i try to explain it: Imagine the 15" would look like a bicycle light to the front - now put it 60 degrees to the right and 45 degrees to the floor - that's how it would use up the least space i thought. 
Nevertheless i would have truble to get the rear chamber big enough i guess... For the Front chamber i would have 60l (easy reachable) to 67l (max possible). Rear chamber could have 89l to 110 Liter max.


same from the side:















(Tapped) Horn:
Pro:
+ Sensitive

Cons:
- Bigger
- Go deeper in groups - but i'm just gone build one.

Questions:
- Do you think i can realize a horn that gets 35hz with the given dimensions? 
- There are 12" Plans that should go to 32hz:  http://wizardaudio.hu/hasznos/hangfal%20tervek/bass/tapped%20horn/30Hz-Cowan.jpg - http://wizardaudio.hu/hasznos/hangfal%20tervek/bass/tapped%20horn/30Hz-Cowan.jpg or  http://www.hometheatershack.com/forums/ed-subwoofer-build-projects/61637-tapped-horn-tc-s-epic-12-a. - http://www.hometheatershack.com/forums/ported-subwoofer-build-projects/61637-tapped-horn-tc-sounds-epic-12-a.html
But I guess i would need 15" to go that deep with a single unit outdoor?


Ideas:

I used a 12" but it could also be tone with 15" if that would be better. Messured 270cm Horn path (with 160 Liters), by using the space where i put in the battery in the scetch i could reach 300cm - like this 30Hz tuned version:  http://www.hometheatershack.com/forums/ed-subwoofer-build-projects/61637-tapped-horn-tc-s-epic-12-a. - http://www.hometheatershack.com/forums/ported-subwoofer-build-projects/61637-tapped-horn-tc-sounds-epic-12-a.html - but do you think the growth of the path is enough? One square is 5cm in the sketch, depth could be between 30 and 40cm. I thought to vary the depth to get more like a cone form for the path.



An other 15" version - but i guess it's to much back and forth to get a good sound, or what do you think?
Horn Lengh 170cm:



other options for 15" that i guess are worse for deep frequences than the one above:





Would it be possible to combine a W-Horn with a BR and get better bas than this project: http://www.freespeakerplans.com/plans/14-plans/basscab/12-mhb-4818 - https://www.freespeakerplans.com/plans/14-plans/basscab/12-mhb-4818 ? - It would definitely be more balanced on a bike!


Another Duble Horn without BR but 135cm length each:








So, what you guys think would be the best option to get enough bass in an outdoor environment (with least battery drain)?
I'm tending to the 12" or 15" 6th order design because it would be a lot easyer to calculate for me as i have no experience with calculating boxes at all. Also so far i guess i would get more bass out of these. Or would the bass from the horns be "enough" for medium volume too and using a 6th order for reggae/dub basslines would just sound crap?

Hope to get some advices here!
Thanks!
Ivo

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Hemisphere Quote  Post ReplyReply Direct Link To This Post Posted: 07 June 2018 at 6:45pm
Epic post! To offset it here's a short answer:

What you need IMO is a pair of tham12's. Two will be so efficient you can EQ up a substantial amount of 40hz when you absolutely need it, and the rest of the time enjoy huge bass pressure above 50Hz and massive battery life.

Also ride under a bridge or through a tunnel with a pair of tapped horns and see what happens LOL

Two will still be way smaller and lighter than any single driver option that will give you better bass for 12v


Edited by Hemisphere - 07 June 2018 at 6:50pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Hemisphere Quote  Post ReplyReply Direct Link To This Post Posted: 07 June 2018 at 7:01pm
Btw I see you say SPL is not the most important, and fair enough, but if efficiency is very important and you want to play for weeks instead of hours, you're gonna need the extra efficiency a pair can offer and reserve the 40-50hz band for special occasions. You'd be surprised how deep a system playing flat to 50 can sound, and also at just how hard it is to get a reasonable level of 40hz outdoors with any system.

Just checked your space constraints properly (viewing from a phone so pics weren't easy to make out). Your volume requirements are in line with a pair of tham12's (they're 96 litres external and I see you're considering up to 170 litres internal)

Study the layout and see what you can do with it (path length, mouth size etc) - one equivalent on each side of the bike may be possible!


Edited by Hemisphere - 07 June 2018 at 11:05pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bitSmasher Quote  Post ReplyReply Direct Link To This Post Posted: 08 June 2018 at 1:33am
I like this, ambitious and creative...

Working backwards from the limitations of bike-mounted boxes, size and weight are your key considerations.

I'd suggest you make a mock-up box with cardboard, mount it on your bike and find something heavy to see what the weight feels like on the front end. 
You'd have to be clever to make a simple reflex box that size/shape that weighs less than 15kg.
If you want to get really specific with weight, calculate the square metreage of panel you'd need, include a few braces, then multiply that by what timber weights per sq/m. Maybe use 7kg per sq/m as a guide for 12mm ply. Add a driver weight, and a few hundred grams for connectors/hardware, paint and whatever else.
 
Now... the nitty gritty. Why 30hz bass? It is a lot of work to make move air at low frequency, especially outdoors - then consider that you're in motion, so wind noise and distance will diminish results for listeners.
Have you played around with speakers and test sounds to understand what you're trying to achieve?

I've been down this path a few times, and asked myself these questions.
First thing I did when attempting a build, was throw a few big weights on the bike to understand how the bike rode when loaded up. I also strapped up a piece of timber to learn how big a box I could carry around the streets.

My latest bike, a Yuba Mundo, has two bass boxes on the back - both measuring 75L x 23W x 45H (cm), sitting either side of the rear wheel- similar dimensions to what you're proposing, which makes for a 75cm wide bike.
The current solution is a pair of 12" reflex built from 12mm ply, tuned to ~70hz that weigh 12.5kg each (neo drivers). Granted I plan to build new boxes that use clever bracing and 9mm ply to drop a few kg.

Pushing the tuning lower achieved rapidly diminishing results, and attempting to build horns would result in an overly large and heavy box.
These sit on the back of a purpose-built cargo bike, and I find the overall width and weight to be impractical. I wouldn't want to ride a bike that had these mounted on the front!

A lot of my learning came from reading the Boominator build by Saturnus. He's a very clever designer that shared a lot of insights in his development of that system.
The key point to reinforce, that I am glad I learnt early on - you can't make bass without size or power. And that "perceived" bass (missing fundamental) is just as good as "real" bass when you're in any setting other than critical listening.
What's the point of building big, low bass if you can't carry it with you?

I would suggest starting simple with reflex or bandpass if you can do the math, 60hz is a good aim for cutoff. Try a few designs, make sure you can transfer then from pen to plywood, throw them in HornResp and see what you come up with.
I would love to be proved otherwise with my views, as I'm keen to see any sort of sound on bike, so please share your journey as you progress this idea...


Edited by bitSmasher - 08 June 2018 at 1:38am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Hemisphere Quote  Post ReplyReply Direct Link To This Post Posted: 08 June 2018 at 5:46am
He speaks about powering it with a car battery and solar panel..presumably on the same bike! It seems like a lot of the details haven't been thought out tbh, but if you really think you can carry a 200 litre external box and a car battery maybe you really can carry at least the box!

That's why I reckon 2x tham12 (in 12mm ply with neos) or functional equivalent within the space constraints is the way. You could run them pretty damn loud off a 7ah battery (2kg) with 20w each off a nice simple amp, which is all any solar panel you can carry on a bike will charge in a day anyway.

The huge efficiency boost on basically any other alternative cuts down so much on all other weight, cost and complexity issues, that the weight and size of the enclosures is justified. Looking at around 106dB/Watt, so literally 1/10 the power requirements of a single 15" reflex. 122dB with a 2x20w class D chip amp, which again cuts substantially on weight and size requirements, and costs.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Hemisphere Quote  Post ReplyReply Direct Link To This Post Posted: 08 June 2018 at 6:07am

Something like this, essentially. Centre space for electronics. Fit whatever path length you can within your size constraints, that's the right path length, and whatever bass response that affords you with a pair of 12" drivers, whether it's 50hz or 55hz or even 58Hz, that's enough bass extension. Remember the added efficiency of a design like this plus the small extension boost from using a pair of horns gives you headroom to EQ up bass at least 10Hz lower than cutoff, even 15Hz at quite enjoyable levels.

Simple build as tapped horns go, seems like it'll work to me. With a bit of creative thinking you might be able to squeeze a few cm of additional path length out of the centre point as electronics in this design would be compact enough to store elsewhere, but that would introduces extra complexity to the design and build for minimal gains.


Edited by Hemisphere - 08 June 2018 at 6:25am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Shortrope Quote  Post ReplyReply Direct Link To This Post Posted: 08 June 2018 at 8:14am
Definitely go for the Tham12 it’s a Savage little Sub. 
As the others have said ditch any plans for 30hz. 
Get a leisure Battery not a Car Battery. 
My Tinnitus is coming along nicely!!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote JonB67 Quote  Post ReplyReply Direct Link To This Post Posted: 08 June 2018 at 9:23am
I take it its not for on road use then? Like at all even a little bit? All that weight on the steering will mean youre slower to manuver and could make an easily avoidable accident into an unavoidable accident. 


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Post Options Post Options   Thanks (0) Thanks(0)   Quote Shortrope Quote  Post ReplyReply Direct Link To This Post Posted: 08 June 2018 at 9:39am
Tham 12s aren't light even with a Neo driver.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mini-mad Quote  Post ReplyReply Direct Link To This Post Posted: 08 June 2018 at 12:20pm
Originally posted by Shortrope Shortrope wrote:

Tham 12s aren't light even with a Neo driver.

...cut it to half width and use a 6.5inch driver on each side. 12mm ply with as much bracing as the design will allow without screwing with it to much...

One per side...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SubMeditation Quote  Post ReplyReply Direct Link To This Post Posted: 08 June 2018 at 12:48pm
Greetings!


Thanks for the tree quick reponses! 


First: So far everyone suggested me to get 2x12“ instead of 1x12“ or 1x15“. 

As i understood the reason for this is because 2x12“ both producing say half the spl 40hz of a 15“ are even more efficent than one 15“ producing 40hz? Is this correct?  Otherwise i don’t understand why 2*12“ should play deeper than 1*12“ (considering they cant be placed directly next to each other)?


I heared a 12V system with 4x12v car batterys running 2*18“ scoops and 2*HD15 plus tops, turntable and co running more than 6 houres (maybe two houres on max SPL (which was not different than 2 scoops from 220V) so i assume that running one 15“ for 4 houres with 300W (300/12=25A -> battery with 100AH -> 3h play time if you consider having some 7“ or 5“ tops with 75W each aswell (total 450W/12=37,5A) - that’s approximately the play time i’m looking for and want to get the deepest Hz out of that 300W budget). 

So two 12“ running on 150W each would be more efficient (on deep Hz not SPL) than one 12“ or 15“ running on 300W?



Second: So far everyone was suggesting taped horns. I would like to know what is the reason for that? Why is a 6th order box not considered as an option? Is it because of more building experience of taped horns here in the forum or because the speaker would need more Watts because of the pressure in the box?

For example what do you think about this design: https://www.poweraudio.ro/diy/albums/userpics/10001/BP12.pdf

(Still i thought running the sub between 40 and 80hz like usual in reggae/dub, but the second chamber of this design is tuned to 120hz - and i guess a tham12 should also be used up to 150hz, rihgt?)




Now specific answers:



@Hemisphere: Yeah, i assumed 40hz (or even 30hz) are hard to reach, maybe i was a bit optimistic after reading through a lot of car-sub threads (that run on 12v too but are in a really small room and thus not comparable - you’re right). Still, couldn’t a 6th order bandpass design deliver 40hz?





@bitSmasher: You’re right, weight is important. I assume 20-30kg weight at the end - not easy, but because traveling speed would be 15km/h most it should be managable. I rather go 5km/h slower but have a proper bass with me than carying a smaler box but cant really get setisfying bass.

Still i would prefere to build the box when i got a plan what should go in because of different shapes of the box with different plans (some not even equal considering size for left an right).


Considering weight: I read this thread: 

http://www.avsforum.com/forum/155-diy-speakers-subs/1365445-building-mobile-music-system-bicycle-setup.html

where someone is building a BR box out of a „Sonotube“ - i never saw this tubes before, but do you think it would be stiff enough for 40hz tuned 6th Order bandpass boxes? - i thought i could be critical and not beeing able to vibrate to be a resonance box, but it would be extremely lightwise… - so maybe it would be usable for a taped horn design?


Why 30hz? Well, you’re right, mybe i read to much car-sub threads in the last weeks, and i thought about wind noise too but wasn’t sure wich hz it will affect. Still i would be willing puting effort & wight + battery life least, compared to an option that will give me 40hz instead 50. 

At home i got an Adam sub10 that gets me 25hz so i know what i’m talking about, and i analysed the frequency of „obliterate“ by bukkha and it got it’s maxima at 32hz - that’s why i thought 30hz would be used if possible. 

So a BR tuned to 70hz is not an option for me. 








You’re right, horns would make it more havy, so you have build a BR for a bike, what do you think about a 6th order tuned to 40/80 maybe? You said lower tuning would be lead to „diminishing“ results - in case of battery life or what (sry, not an native speaker here). 


Thanks for the tip, i’ll google the Boominator build by saturnus next time i’ve got spare time.





 

@Hemisphere:

The idea was putting the car battery on the back carryer and the solar pannel ontop of the box, or on the back carryer, or on a small single wheel trailer (by the way this would be an option for carrying a sub too. So if i can’t get proper bass with a box on the front caryer i just would go with a sub18 and put in on the trailer - but i would prefere a design that i could use without trailer and most importat: that other people can build too without having a trailer)


Refering your build sketch: I thought the lenght of the path is deciding what frequency the taped horn is boosting. With that small path i assume it’s not boosting anything low - or am i wrong?

I planed to put the electric (amp, battery) on the back caryer, so i don’t need to save space for that in the box.


@Shortrope: What’s with 6th order designs tunded to 40hz?

An what is a "leisure Battery"? If i google it i just get other batterys that work with Pb aswell (considered LiPo batterys too, but they are too expensive if you want 100ah, plus they are not as durable considering heating in the sun)


@JonB67: Yeah, it’s for on the read use 70% of the time. I’m planing with 20-30kg and are experienced with driving with front carrier luggage bags.


@mini-mad: Why two 6.5 istead one 12"? I thought one big one can deliver more low hz than two small ones? Still low hz is more important to SPL for me.




But again thanks so far for you're ideas! 

But still i'm interested why everyone is suggesting me even 2 x tham12 that goes to 50hz instead of one 6th order 12" tuned to 40/80hz that i could run on double the Watts than the tham12s?





 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Hemisphere Quote  Post ReplyReply Direct Link To This Post Posted: 08 June 2018 at 12:51pm
Yes smaller drivers would definitely be fine for one a side.

It's the efficiency benefit of the pair which you really want to harness, and your design constraints are calling clearly for two regular boxes not one bizarro-box.

To see what a good 6.5" driver can do in a tapped horn, see this design by Volvotreter: http://wp.volvotreter.de/projects/th-2/the-tangband-38hz-horn/

98.5dB efficient and useable to 38Hz. A shorter version of this with the same driver (something like the awful sketch I posted) would be great and you could get a decent 45Hz response at least.
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