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Car audio for a push cart

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October 3, 2012 1:35:31 AM

Hello, Thank you for reading. I play sax and I just got some cool play along cd's so I want to start playing out on the street for tips. (it's called busking) here they have food carts and it might be true that they might provide AC I want to get mobile. So I have some speakers 8 ohm and an RV battery. I went to buy a used car amp and the guy said, oh O! you should or rather need 4 ohm speakers. for the main speakers I can wired the 8 ohms speakers to 4 ohms. However the sub I own is a 15" 8 ohm and needs to run solo, so to speak. any thoughts? bad idea? looking for help before spending good money.

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October 4, 2012 1:00:09 AM

A 15" 8ohm? Not that common for car audio but not a problem. What is the wattage needed to run the subwoofer? In your case I'd look for a good 4 channel amp and run the the sub off of the rear channel and the mids and tweets off of the front channel. How do you plan on sending the audio to the amp? How many speakers do you plan on running? A proper cart like that for playing sax music would do well with 2 quality 6" speakers with your fifteen to cover the lows. With your subwoofer you gotta go with a sealed box.
If you tell me the specs and make of the speakers and your budget I can recommend a quality amp, wire sizes, how to wire it, and the boxes to make. For an application like this I would make boxes for all the speakers.
Also just so you know the guy was full of BS about 8ohms not working. I think he doesn't understand amplifiers that well because they usually don't put 8ohm ratings on amps. 4ohm speakers will obviously reduce resistance so the amp can push more power and run more efficiently but other than that there's no problem with it. Any amp can handle 8ohms it's dropping down to 2 or less ohms that some amps can't handle.
October 4, 2012 7:31:41 PM

Thank you wip99gt,
you are awesome for the reply. OK the 15" is an Electro-voice I build the box a few years ago with an sub woofer amp I bought on ebay in the cabinet this amp was crap and the whole thing now sits in the garage and has for a few years now. So I'll have to dig the thing out and remove the cheap amp I put in it. I was going to plug up the spot where the amp was with the same wood I used to build the cab. I went to local pro audio shop and the guy helped me with the porting for this cab a 4" and I had to cut the depth for his measurements as to cabinet size and speaker out put. Anyway I can get more specific in a day or so. the speaker was from a PA system that I got at an auction I pulled it from a speaker system that the cabinet was trashed and full of rat droppings yuck.
As for high end I have many things to pick from a while back I got a wild hair and got a bunch of Altec 409T 8" Coaxial Speakers some with transformers. These were used as ceiling speakers back in the day nowadays the tube freaks like em as I guess the out put has a flat output.
I can put 4 them towards this project. I also have two large shure styled speakers with about 6X 8" speakers in them I got them with an old 20 watt power amp and it didn't get very loud. Tried to use for vocal system at a big band I play in didn't work for that. so... also I have some horns from the speaker system that pulled all the components from. However some might be blown as were the 8 Black widow 15"s I got from that action. OK now I am going on and on. I have a lot of stuff I will put a list together with as much info as I can get. I do like vintage however this is probably not the right project as I have heard the newer speakers run better on a battery system as they are more efficient.
Trying to do this for little cash as I am not sure the thing will work on the street for me. For one the weather is going to get cold up here Portland Oregon. and if it really good and loud I just might get it confiscated by the cops even though I have the free speech going for us. I read about bucking and the courts. If I am good it this I just might get a gig in doors with AC then I can use my Mackies (450's)with sub.

I am sorry I went on and on here thank you for reading this mess. I'll open my sub and get the info requested.
Thank you again
Edd

wip99gt said:
A 15" 8ohm? Not that common for car audio but not a problem. What is the wattage needed to run the subwoofer? In your case I'd look for a good 4 channel amp and run the the sub off of the rear channel and the mids and tweets off of the front channel. How do you plan on sending the audio to the amp? How many speakers do you plan on running? A proper cart like that for playing sax music would do well with 2 quality 6" speakers with your fifteen to cover the lows. With your subwoofer you gotta go with a sealed box.
If you tell me the specs and make of the speakers and your budget I can recommend a quality amp, wire sizes, how to wire it, and the boxes to make. For an application like this I would make boxes for all the speakers.
Also just so you know the guy was full of BS about 8ohms not working. I think he doesn't understand amplifiers that well because they usually don't put 8ohm ratings on amps. 4ohm speakers will obviously reduce resistance so the amp can push more power and run more efficiently but other than that there's no problem with it. Any amp can handle 8ohms it's dropping down to 2 or less ohms that some amps can't handle.

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October 5, 2012 12:29:03 AM

Cold up here in Portland? I live 200 miles North of Edmonton Alberta, we'll see a couple days a year below -50 celcius. Either way though playing a sax outside below the freezing point doesn't sound like much fun to me.
Most of my experience is with car audio. I've hooked up some Altec speakers before for home audio and have seemed pretty good. Those are a pretty low wattage. They're rated at 16 watts rms and 32 max. I'm guessing the sub is a low wattage as well. For an amplifier I would think about an Alpine MRP-F300. Its a really good bang for the buck amp and pretty power efficient. You could run two off of each front channel and at 2/3 to 3/4 gain you should see close to the rated wattage for the speakers. Then with the rear two channels bridged an 8 ohm subwoofer should get close to 75 watts rms. You'll only need to use 16 gauge wire for all the speakers and 12 gauge for the power and ground wires. That should make for a pretty cheap kit. Do not waste your money on an amp install kit. Go to a electrical store for the power wires as you should be able to get 10 feet, all I think you need, of good 12 gauge wire for a few bucks. Good 12 gauge wire is rated for 35 amps so around 400 watts at 12V DC.
Here's the amp:
http://www.ebay.ca/itm/ALPINE-MRP-F300-CAR-AUDIO-STEREO...
With your sub box and wattage I can understand going with a ported box for something like this and with a sax I see the difference be negligible vs a sealed but sound quality is always better in a sealed. I always try to recommend sealed but I think this is one of the few times, other than SPL cars of course, that a ported might be the better option.
If you do this project and blow the speakers I have a set of Alpine component speakers that I'm eventually removing from one of my project cars you can have for free.
October 5, 2012 7:17:16 PM

Hello Wip99gt,

Wow your cool thanks for the info. I did buy a used amp off of craigslist yesterday 30 bucks US and the guy delivered it to me (funny how that works out) (I think people just don't want you to know where they live) it's OK. What the guy had as an old Kenwood KAC-642 I understand it's about 12 years old and the power rating is like 40w X 4 @ 4ohms and this unit has no cross-over.

In the next few days I will hook it up and see just what sort of sound pressure levels I can get. I will use the few speakers I have here and then if not good see what I can try out from friends and things.

The one thing that seems important to me is I will be on a car battery and that will drain as the thing plays I hope to get 3 to 4 hours before a real loss of power. So a smaller amp draws less power I know this and really efficient speakers would make a big difference, we will see how the experiments go.

My mum (Mom) was from Canada (Winnipeg). They keep sending my uncle back paid for by the state LOL well its true. Anyway yes it does get cold here but not like you guy do there the rain here is mostly the problem.. So on my music cart I want to build in a large umbrella and add some tiki lights if I use this at night.

As to just where am I going to use this thing. Here in Portland the west coast Portland (Oregon) we have an odd thing that is sort of new called food carts and it's just that like concession carts that have a food idem that might be just odd or different. They are in parking lots and have circled the wagons so to speak 6 to 10 and open space in the middle so that one spot I am thinking of. Also the sporting arenas and as people walk to the and from the game just set up where they can be entertained for a short amount of time. So that my plan with the cart deal yup summer will better as I could do the farmers markets and Downtown stuff as well. Also no one can smoke inside bars now days here and that also lends itself to some opportunity's.

So that is my business plan so to speak. by the way I am 57 yrs old and not a kid so making famous is just not going to happen so all I want to do is play my sax make a few bucks and call it good.
I'll let you know what happens. One last thing while we do have noise ordinances in this area the Free Speech in the Bill of rights is a big deal and will keep the cops at bay even with amplification. I read all about this already on line its called busking and the 9th circuit court of appeals has made some rulings on this enough for me to feel like it's worth a try.

-50 Celsius would not see me out side let along blowing my sax No way. I have worked in Alaska (Fairbanks) but that was summer. You are much stronger than I am. Thank you again for all the help. I will let you know
Edd
October 5, 2012 11:56:28 PM

They have those food carts all over Edmonton now too. Its gotten popular everywhere I think. It makes sense to try it. A day at the farmers market could net you some decent change and be fun. In Edmonton they use city hall for the Farmers Market in the winter and let all the buskers in as well, it's worked out pretty good. Now for busking in the city I think it's a $50 yearly permit you need to get here but they never check for it.
That amp should do you pretty well. It's power efficiency won't even be in the same league as that Alpine but an RV battery should easily power it for most of the day. Most of them I see are 700 cca plus and deep cycle so their meant for it.
I get stuck going to Winnipeg at least twice a year. I hate that city with a passion.
November 15, 2012 5:03:06 AM

Wow your cool thanks for the info. I did buy a used amp off of craigslist yesterday 30 bucks US and the guy delivered it to me (funny how that works out) (I think people just don't want you to know where they live) it's OK. What the guy had as an old Kenwood KAC-642 I understand it's about 12 years old and the power rating is like 40w X 4 @ 4ohms and this unit has no cross-over.

In the next few days I will hook it up and see just what sort of sound pressure levels I can get. I will use the few speakers I have here and then if not good see what I can try out from friends and things.

The one thing that seems important to me is I will be on a car battery and that will drain as the thing plays I hope to get 3 to 4 hours before a real loss of power. So a smaller amp draws less power I know this and really efficient speakers would make a big difference, we will see how the experiments go.

My mum (Mom) was from Canada (Winnipeg). They keep sending my uncle back paid for by the state LOL well its true. Anyway yes it does get cold here but not like you guy do there the rain here is mostly the problem.. So on my music cart I want to build in a large umbrella and add some tiki lights if I use this at night. http://www.obd2toolbar.com/
November 28, 2012 11:58:13 PM

Look for led lights, they use very little power. Remember that you can always hook up more batteries if need be. Keep them in a parallel circuit to maintain the 12v you need. I have 2 1000cca batteries in my jeep and 4 1000cca batteries in my work truck.
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