Newbie Question - Amp's and Sub's

I know that this has probably been covered hundred's of times so I appologise to bringing it up again.  I saw several topics that seemed close to my question, but I can't seem to get my head screwed on straight and pull the answer out.

I'm hoping that someone here can help me understand a little more about car audio, specifically amps and subs.

If you've ever seen the inside of an MR2 you know that there is NO room. Factory system has 5 speakers: 4" in the dash, 3 1/2" in the rear pillars, and a 4" sub under the driver's seat which runs off the front channels.I've replaced the front 4's and the rear 3's with Boston's, and I've replaced the sub with a Radio Shack 4" sub woofer.At low to mid volume levels it sounds pretty good, but at anything louder it is all highs.I want some more volume, and I want full sound. So, I'm thinking it's time for subs.I've purchased caps to drop the base out of the Boston's. 300Hz for the rear and 200Hz for the front. I have lying around a box with two unknown brand 8" subs and a Boss 400W amp. Oh yea, the car has an aftermarket deck, Pioneer I think, that has pre-amp output currently unused.I was originally thinking that I would build boxes to go behind each seat, put one 8 in each box. But there are two problems with this, 1) that's where the t-tops go, and 2) the t-tops leak and the leak right there.So, I'm not thinking of putting one 8 in the passenger foot space. Too bad, because I know how to wire two speakers from the amp! 98% of the time I'm the only one in the car so using the foot space will not be a problem. I could also upgrade to a 10 later if I so choose. With the speaker here the passenger can still sit comfortably, just can't stretch out.So, finally to the question(s). How do you bridge the output of an amp? And if you do, do you need an 8ohm speaker?Again, I'm not after "Booming" sound I just want full sound, that I can crank when I get the urge The final question is, do you think that this arrangement will give me what I'm after or will there be a lack of mid range?Thanks,Craig

To bridge most amps, take the left channel positive from the amp and connect it to the positive terminal of the sub.  Take the right negative from the amp and connect it to the negative terminal on the sub.  This will give you a bridged output.  You will be just fine without an 8ohm sub, I'm assuming you're planning on using a 4 ohm single voice coil.  Is that the case if not let us know, because otherwise what I wrote won't apply.

that amp will be about 200 watts rms bridged it will not be 2 ohm stable bridged. only in stereo. in other words 1 2 ohm load on the left ch and1 2 ohm load on the right. you should not worry about 2 ohms. Get a single 4 ohm 10 and run the amp bridged. the amp will run at it's best at 4 ohms. my buddy has a mr2 and we put 2 ten under the front trunk space. It did ok. it did not slam but it did make for a fuller sound in the car. hope i helped you out. have fun with your project. Big Dave

By how you've described it, the speaker is a SVC (DVC's have 2 pairs of inputs (2 +'s and 2 -'s) instead of just 1 pair). The ohm rating is 4ohms (what is painted on the back of the sub is the overall ohm rating of the speaker). You can run that 1 sub fine with that amp. From what I've been able to find, you have a 2-channel amp that pushes 200watts per channel at 2ohms. "2ohm stable stereo" simply means that this amp can safely run a 2ohm load on each channel, and produce 200 watts per channel. If I read your posts correctly, you only want to run one 8" (or possibly one 10" later) speaker from this amp. Since your amp is bridgable, it should be at least stable at a 4ohm bridged load. So what you would do is run the speakers + to the Left + on the amp, then run the speakers - to the Right - on the amp (like your diagram on the amp shows). You have just bridged the amp (meaning you are combining both channels into 1) with 1 speaker. As for power ratings, if I did the math correctly you will get apx. 400watts to the speaker by doing this (probably a little less). Unless I'm confused, since your amp will do 200x2@2ohms, then it should produce 100x2@4ohms, which would relate to apx. 300-400x1@4ohms bridged. IMPORTANT Since you do not know what the speaker is rated at, and don't have any other make/model number to reference, I would highly recommend starting by hooking the speaker up to only 1 channel of the amp first and seeing how it sounds. You would only be pushing apx. 100 watts to it, but you would be able to hear if it was distorted. If you like the sound, then keep the setup. If it still isn't loud enough, then try the bridge that was described earlier, just be aware that 300-400 watts is alot of power to throw to an older single 8" speaker, and you run a serious risk of blowing the speaker (but if you've got the other to replace it, WTH!)Squirrel

"No more Cpt. Kirk chit chat"

If its too loud, then you're too old

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Don't worry, there are no dumb questions on this site. Most of us are trying to increase our knowledge as well As for your questions... 1) Words still undecided on running amps and not using all the channels. I have personally done this with Kenwood amps before and did not experience a problem. What I would suggest if you run only 1 speaker, is only hook up 1 RCA cable (that is to say if you only run the Left channel of the amp, only run 1 RCA cable using the left input). I said left because most mono setups default to the left channel. By not hooking up the right RCA, you wont have that signal going to the amp and not being used. Just a thought 2) The knob you are referring to is more connonly called the "Gain control". This is an adjustment that allows you to match the amplifier's input voltage to the headunit's RCA pre-out output voltage. By increasing or decreasing the gains, you adjust how "sensitive" the amp's input signal is. Common rule of thumb if you don't know the exact setting to use (or just want to tweak the system) is to turn the gains all the way down, turn the headunit about 3/4 of the way up in volume, then slowly turn the gains up until you start to hear distortion. At that point, back the gains down a little bit (back to a clear/undistorted signal) and you should be at the right setting. One thing to remember about adjusting gains, The higher the number, and usually turning the knob counter-clockwise, is called turning the gains down. The lower the number, and usually turning the knob clockwise, is called turning the gains up. In short, 4volts is a lower sensitivity level than 0.2volts. I believe most headunits have 2 or 3volt RCA pre-outs. But like I said, start low first, then raise the gains. And yes, if you turn the gains down you will be decreasing the amout of wattage that the amp will be outputting (I'm not sure of the exact math behind it though). That's why you start with the gains turned all the way down first (especially if the wattage of the speakers is in question!) 3) You are correct on DVC inputs. I just got into them myself, but all the ones I've seen have inputs on opposite sides of the speaker. Your speaker is a Single Voice Coil. Many SVC speakers (and even some subs) have the type of configuration that you mentioned (2 +'s and 2 -'s, but they are connected together). This is for ease of installation/mounting and different wiring configurations (parallel, series, parallel/series, etc). 4) Based on what you've described, I would suggest upgrading to either a single 4ohm 200-300watt SVC 10" sub ran bridged, or two 4ohm 200watt SVC 10" subs ran in stereo if you can fit both of them. There are still more options that you could do using 2, 4, or 8ohm subs, but unless you're really interested in them I'll stick with the above configurations. I wouldn't recommend DVC's yet unless you have the $'s to fork out, since they can be expensive, and the wiring gets even more complicated! But if you went with one DVC 10" sub, it would need to be 2ohms, wired in series and bridged for a 4ohm total load like this... If you're curious on more wiring configurations, here's a link to one of many wiring wizards out there. 5) Actually, the preferred installation method is to run the power wire straight from the battery (fused within 18 inches of the battery). The amp remote can be hooked up to the power antenna wire (if you tested and get signal with both the radio and CD player on). Are you still using the factory headunit? If not, what are you using and I can try to tell you what the remote line is (usually straight blue for remote and blue/white for power antenna on aftermarket headunits). If you are still running the factory headunit, I believe your power antenna wire is BLACK/ red. You could also hook it up to your ignition switch if you wanted too instead. You could also install a toggle switch on the remote line to manually turn it on/off. Hope that helped. I'm finally off work and getting ready to catch some ZZZZ's! Again, don't be afraid to ask any questions here Squirrel

"No more Cpt. Kirk chit chat"

If its too loud, then you're too old

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No prob. Glad to help. I've always preferred Rockford, but that's just me. JL makes good subs too. If you run some searches on this site, you can get some in depth professional opinions from guys who have been in the business for years.Squirrel

"No more Cpt. Kirk chit chat"

If its too loud, then you're too old

Donate to the12volt.com