Sub with no pre-outs?
Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=11620
Printed Date: May 03, 2024 at 2:48 AM
Topic: Sub with no pre-outs?
Posted By: wrencher_25
Subject: Sub with no pre-outs?
Date Posted: March 29, 2003 at 10:56 PM
My girlfriend has a JVC deck with no pre-outs on the back...my question is can you hook up a sub off the the right and left speaker wires... that being L - and R+ My worry is that the sub will draw too much off of it without it being amplified and blow the fuse in the deck. The other question would be could you MAKE RCA cables off of the leads on the speakers...it IS an AC signal.........just find a ground wire and make the RCA. IS THIS POSSIBLE. I am still new to the industry and am looking for creative ways to work around problems. ------------- Andrew Weitzel
MECP First Class Installer
Replies:
Posted By: Qveon
Date Posted: March 29, 2003 at 11:04 PM
ok what you have to do is take the L&R out of the deck and plug it into the HI-Inputs of your amplifier and then you can run your sub off the amp's outputs.
Posted By: Qveon
Date Posted: March 29, 2003 at 11:05 PM
oh and i forgot, no you can't make a RCA cable because the input voltage would be too high for the amp.
Posted By: speedwayaudio1
Date Posted: March 29, 2003 at 11:12 PM
they have rca conversion kits that turn high level to low level rca
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Big Dave
Posted By: bberman1
Date Posted: March 29, 2003 at 11:13 PM
Get a high to low converter (LOC) with that you can tap into your rear speakers and it will convert the signal to a RCA. From the converter you can than run RCA cables to your sub amp.
Posted By: esmith69
Date Posted: March 30, 2003 at 2:00 PM
You'd never want to bridge the speaker outputs of a head unit, especially if you're sending it to a line output converter. That being said, the best solution would be to tap in to the back speakers' wires as bberman said, and this will give you a relatively clean signal to send to the amp via an RCA cable
Posted By: wrencher_25
Date Posted: March 30, 2003 at 2:16 PM
Awesome...thanks a lot for the tips. I'll see what kind of kits I can find in town.
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Andrew Weitzel
MECP First Class Installer
Posted By: bberman1
Date Posted: March 30, 2003 at 2:25 PM
Glad to help just ask any car audio shop for a good quality high to low converter.
Posted By: drvnbysound
Date Posted: April 01, 2003 at 2:47 AM
Im curious to know how "Andrew" has "MECP Certified Installer" as part of his signature, and still asking questions as this one? I would think, as a certified imstaller, one would know about a Line Output Converter.
Posted By: dragonrage
Date Posted: April 01, 2003 at 8:27 AM
High to low converter in a nutshell. This'll give you about 1V if if your deck is around 40W/chan. (from deck +) ____/\/\/\(10KOhm)/\/\/\_________(to amp +)
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(from deck -) ____/\/\/\(1KOhm/\/\/\____|
|_________________________(to amp -) ------------- 2009 Pontiac G8 in planning stage
HU: ?
Speakers: ?
Amps: ?
Posted By: wrencher_25
Date Posted: April 01, 2003 at 12:20 PM
Well, First of all drvnbysound - If you even READ my message all the way through, I said that I was still new to the industry.
If you really want to know about my full backround - I am still only 18 years old. I just spent (all in all) $9000 going to school in Toronto for a mere two months at the ONLY fully ACCREDITTED school car stereo school in North America. Now, I am MECP Basic Installer Certified. I am also MECP First Class Installer certified but I havn't even worked a full year yet. Anyone can have a piece of paper that says they're MECP certified. It doesn't mean that they are experienced installers. If you're worried about me going and giving crap replies to ppl, I don't reply to everything, just things that I know or have an idea on. Esmith69 for eg, seems to be very knowledgable on this site and has a lot of good responses. So before you start making judgements on people why don't you find out their full backround and where they're at in there career. OK? OK. ANDREW
Posted By: Velocity Motors
Date Posted: April 01, 2003 at 12:30 PM
Well represented Andrew & thanks for keeping your head on straight. All of us installers ( at least once or twice in our careers) will run into criticism & confrontations with customers or even other installer's. Nobody knows everything about all aspects of the 12 volt industry and everyone is entitled to their opinions. The best thing you can do is take the criticism and learn from it. Please keep in mind that if you are going to be criticizing a another member's techniques or project on this forum, that you keep the criticism contructive and something for the member to use as a tool to get bettter..... NOT to trash talk someone or rip his/her project apart.
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Jeff
Velocity Custom Home Theater
Mobile Audio/Video Specialist
Morden, Manitoba CANADA
Posted By: wrencher_25
Date Posted: April 01, 2003 at 12:36 PM
I completly agree. I just didn't find that critisism constructive at all. I find that poking at someones credentials (especially when they've worked their asses off for it) is something that I don't take lightly. And I know that I am still new, and I am VERY willing to learn and have a sheer passion for this industry. I love every minute of my job. It's keeping the critisism constructive and try to say it nicely...b/c lets face it, no one likes to admit their wrong. I think that critisism should me made about the topic, not the person. Thanks for the input Velocity Motor.
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Andrew Weitzel
MECP First Class Installer
Posted By: Velocity Motors
Date Posted: April 01, 2003 at 12:53 PM
No problemo Andrew.... good luck with the career of a mobile installer.
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Jeff
Velocity Custom Home Theater
Mobile Audio/Video Specialist
Morden, Manitoba CANADA
Posted By: dragonrage
Date Posted: April 01, 2003 at 12:56 PM
Did you end up getting a high to low converter? I've had some people criticize the way I mentioned but there's nothing wrong with it. It's cheap (under $1), it takes up almost no room, and it's simple. Some people on here have said that it's improper and to spend the money to get a real high to low converter, but they just don't know how it works. The other way it could be done is using an op amp and the formula: gain = Rfeedback / Rin. But for an opamp you'd need a DC offset to not need to use the negative voltage supply. So if you haven't gotten a high to low converter, I'd use the original circuit I posted. I use it now and it works. Though as my sig says I'm getting a new CD player soon anyway :)
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2009 Pontiac G8 in planning stage
HU: ?
Speakers: ?
Amps: ?
Posted By: wrencher_25
Date Posted: April 01, 2003 at 1:55 PM
Dragonrage... Your way looked really interesting (using resistors) and would make a lot of sense. The buddy I took school with recommended the same thing but we didn't know the right values of resistors. The prob is...i don't know the power rating of the amp that I have. (I bought it used unfortunately) But it does have a "HI input" and I was thinkin bout just soldering directly to the pins. But if you know the rating of the amp then maybe you could help me with the resistance values. I would actually like to know how to calculate those values if you don't mind. But the model of the amp is a Pheonix Gold QX 2180. I don't know the power ratings or ANY of the specs which makes things difficult. Thanks for the help too!!! ------------- Andrew Weitzel
MECP First Class Installer
Posted By: dragonrage
Date Posted: April 01, 2003 at 7:27 PM
Well, you don't need exact values. But I will show you how I came up with those. Formulas used: P = V^2/R, voltage divider So using the above formula, if you had a 40W/chan deck,
40 = V^2 / 4
160 = V^2
V = 12.65
So you have 12.65 volts peak out If the top resistor on my schematic before is R1 and the bottom is R2 and we'll call the voltage at the amp Vamp
Vamp = Vdeck(R2/(R1+R2))
Vamp = 12.65(1/11)
Vamp = 1.15V Note that you don't NEED about 1V, most amps go down to about .25V, and up to at least a few volts. You can play around with the values as needed. ------------- 2009 Pontiac G8 in planning stage
HU: ?
Speakers: ?
Amps: ?
Posted By: drvnbysound
Date Posted: April 01, 2003 at 10:58 PM
I wanted to take the time and apoligize for my previous post. I did not intend for you to take it as as I "poking fun" at you. I have been in the industry going on 5 years now, and you are the first person I have come across who is MECP certified and was unfamiliar with LOC's. I, as most people I know, got into the business by installing equipment in their personal cars, and friends cars, before attempting, or even thinking about taking the MECP test.
Personally, I am an Electrical Engineering major at Florida State University. Currently, with the help of a friend, about to open a stereo shop here in Panama City, FL. Odd thing, is that I have not even taken the MECP test personally, nor have I flipped through the pages of the study guide. However, I have previously worked at various shops, doing everything from custom fiberglass enclosures to mobile video systems, and whatever else I was called upon to do. I have the understanding of how most mobile electronics products work, though my studies as an engineer. Once again, just seemed strange to me, that you were MECP certified and had the lack of hands on experience with the acutal products. Again, I apoligize for my previous post.
Posted By: wrencher_25
Date Posted: April 01, 2003 at 11:48 PM
To be perfectly honest.....I am MECP certified but still within the first weeks of my working experience....school trained me well for that test but I know that it means nothing until you have the hands-on-experience. There are a lot of ppl out there more skilled and trained and it will only take time before I gain that experience and will really be able to call myself "elite" or a "master" installer. It all takes time. But enough about that.....lets get back to what's important.....and that's car audio. ------------- Andrew Weitzel
MECP First Class Installer
Posted By: wrencher_25
Date Posted: April 01, 2003 at 11:50 PM
Thanks a lot dragonrage.....i'll keep that one handy and play with some figures. I know some decks are 50W/Channel and so on.....i get it now. Thanks so much. ------------- Andrew Weitzel
MECP First Class Installer
Posted By: wvsquirrel
Date Posted: April 02, 2003 at 12:02 AM
In case you wanted it, here's your QX manual. Sorry it's an all inclusive manual for the QX amps, but I couldn't find one online that just covers the QX2180. I'm assuming it's a QX Chrome, because Phoenix didn't have anything for the 2180 listed under the QX Black (at least not that I saw). ------------- Squirrel
"No more Cpt. Kirk chit chat"
If its too loud, then you're too old
Donate to the12volt.com
Posted By: wrencher_25
Date Posted: April 02, 2003 at 2:44 PM
Thanks so much wvsquirrel. That was awesome. Did u just do a random search on the net to get that or is there a manual site that you got that from. I've been looking for that on the net.
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Andrew Weitzel
MECP First Class Installer
Posted By: wvsquirrel
Date Posted: April 02, 2003 at 11:14 PM
Most of the major manufactures offer online/downloadable manuals for their products on their websites. Some are easier to find then others though (some have a link that says Manuals, some are under the Downloads sections, and some you actually have to click on the product first then get the option for the manual). The 12Volt's links section has just about every manufacturer you could think of. I've pulled manuals from Rockford, Kicker, Pioneer and Phoenix so far for people who have asked for them. Glad I could help ------------- Squirrel
"No more Cpt. Kirk chit chat"
If its too loud, then you're too old
Donate to the12volt.com
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