ClubRoadster.net banner

1 - 12 of 12 Posts

·
Registered
Joined
·
374 Posts
Discussion Starter #1
I've been reading for a bit on stereo systems - most of it is over my head - to figure out a solution for my stereo as I love quality music while driving and the stock miata system is not cutting it. I've installed two systems before but I'm still a noob when it comes to planning what parts to put with each other.

I have an amp/subs that I took out of my previous car:
2 channel 500W amp
2 12" subs <-- there is no way these are fitting in the miata.

I bought a sub/box for the miata:
1 10" 300W sub.

Right now everything is stock on the miata. Just the stock head unit, and the 2 crappy door speakers.

If I were to run the amp I have now (2 channel, 500W) with the sub for the miata (1 300W sub) and nothing in the other channel does that mean that the amp will only put out 250W, just to that sub? I'm fine with the 50W shortage (as long as it doesn't damage anything) to the sub - I'm not trying to go deaf. If I comprehended what I was reading correctly, I would have to "bridge" the amp (is that just a switch on the amp?) to get 500W to come out of one channel, otherwise it will do 250W per channel.

If that is the case (only 250W going to the sub) then is there a way to hook up the other channel to the door speakers? Some kind of Y connection (anti-bridge? :woolery:)? If so does this cut the power in half to each of the speakers? (250/2=125 to each speaker?) Or is it an inconsistant flow of power to each? Of course I would wait to upgrade the speakers before running any more power to them.

Just for giggles, let's say I installed two 6x9's on my rear deck. Making a total of 5 speakers, 4 "door" speakers, and a sub. Is it possible to get a two channel amp to power all of that? The sound quality would probably suffer right? Just trying to understand the concept here.

What I'm trying to figure out is if I should sell my amp and the two 12" subs as a package and buy a different amp, or run the amp I have and just sell the subs for head unit money.

Sorry for the noob questions.
 

·
Registered
Joined
·
181 Posts
If you post a pic of the amp it will be easier to tell if it is bridged, or how it can be.
Most amps like that would put out 500w. and have two outputs that are actually connected.
This means that you would control the power difference by the resistance difference.
If you want 250W going to your sub, you need to figure out the resistance through your sub and match that in a parallel loop. Otherwise, it would put out all 500w to just the one.
You could get it to power speakers and subs, but you would need to do the physics on the resistance to run them parallel not in series and you would need to put a very small cap on your speakers so you dont blow them with the low frequencies that you send to the sub.
 

·
Registered
Joined
·
374 Posts
Discussion Starter #3

Uploaded with ImageShack.us


Uploaded with ImageShack.us


Uploaded with ImageShack.us

If it is bridged, I am pretty sure I'd want to un-bridge it. At least I would want to do whatever I need to do, in order to make it put out no more than 300W to the sub.

If the amp is rated 500W with two channels that means (in general) it is 2x 250W channels right? Then you can bridge it to get different outputs.

The door speakers are not as important at the moment, I was using those mainly to understand the use of channels.
 

·
Registered
Joined
·
648 Posts
Your best bet is to leave both channels bridged, and turn the gain down to zero and slowly increase it from there. Unless it is a "Class D" amplifier those values are peak output, not RMS (Root Mean Square) which is the nominal output. According to what I can find, it will put out 320w at 4 ohms as it's a class AB amp.

If you keep it bridged and the resistance through the sub is 4 ohms you could run the gain of that amp around 7-9 and be safely within the 300w rating of the sub (if it's 300w RMS).

Is the sub a dual voice coil or single and what brand and model is it?
 

·
Registered
Joined
·
374 Posts
Discussion Starter #5
Thanks for the useful information! I think I'm slowly starting to pick up on this stuff, it's like learning a new language with all the definitions lol.

The sub is a Boston G2, 4ohm single voice coil. (10" version)

I think it is this here:
http://www.crutchfield.com/p_065G2104/Boston-Acoustics-G210-4.html?search=boston+g2

Unless there is a knockoff brand of boston acoustics called "Boston". The picture looks identical though.

It says the RMS range for the sub is 75-300W, so as long as I don't turn the gain on the amp up ALL the way I'm likely to be in safe operating range. Correct me if I'm wrong.

In order to bridge this amp I would have to run the positive wire and negative wires furthest from each other for one sub right?

(+) + - (-) <-- the parenthesis indicate where I would put the wires on the terminals.

I'm tryin to interpret the information on the amp from this site: http://www.rockfordfosgate.com/products/product_details.asp?item_id=112089
 

·
Registered
Joined
·
648 Posts
Connect your speaker wire according to the "2Ω Minimum" diagram (one positive to one negative, it looks like the outermost terminals) and keep the gain low to begin with. As long as you keep the output of the amp below the 300w max of the sub you'll be fine.

Is this a new amp and sub, or used equipment?
 

·
Registered
Joined
·
374 Posts
Discussion Starter #7
Sweet thank you!

I had the amp in an older car of mine, but I was running two much larger subs off of it. The 10" sub I bought off a member on here, I'm pretty sure it was used. It appears to be in flawless condition though. So I would answer used equipment lol.
 

·
Registered
Joined
·
19 Posts
That amplifier is mono (one channel). Even though there are two sets of terminals, they are wired together as one, that's why it says "outputs paralleled internally". just wire your sub up to the positive and negative terminals and you will have 320w of power.

For your other speakers, you will need to buy another amp or run them off your head unit. You can check out my audio build here.
 

·
Registered
Joined
·
648 Posts
Sweet thank you!

I had the amp in an older car of mine, but I was running two much larger subs off of it. The 10" sub I bought off a member on here, I'm pretty sure it was used. It appears to be in flawless condition though. So I would answer used equipment lol.
Okay good. I know I smoked an amp once, and someone swore it was from not 'warming' it up. A less than fun experience to say the least, but I haven't bought any amps or subs for a good 6 years now. My old school Orion gear (pre-DEI buyout) is still running strong.

That amplifier is mono (one channel). Even though there are two sets of terminals, they are wired together as one, that's why it says "outputs paralleled internally". just wire your sub up to the positive and negative terminals and you will have 320w of power.

For your other speakers, you will need to buy another amp or run them off your head unit. You can check out my audio build here.
I've never understood why they would do that, making a mono amp and wiring it properly would be much easier and less hassle, unless they're just adapting an existing design to market 'two' amps utilizing the same housing.
 

·
Registered
Joined
·
19 Posts
I've never understood why they would do that, making a mono amp and wiring it properly would be much easier and less hassle, unless they're just adapting an existing design to market 'two' amps utilizing the same housing.
It's not that uncommon and there's nothing that 'improper' about it. Having two sets of terminals makes it easy to wire multiple subs to your amp. Say you had two 4ohm subs, you could wire them each directly to the amplifier instead of stringing them together. This gives you a better quality connection. Whether it's actually necessary is debatable.
 

·
Registered
Joined
·
939 Posts
I'll tell you right now, you are way over powered. The stock head unit and speakers are crap. Your money would have been better spent with an upgraded head unit and speakers. The stock HU runs maybe 10 watts RMS/Ch. Aftermarket HUs usually run 20 watts RMS or more pair that to a decent set of speakers and you would be suprised how much bass you can get out of that without a sub.
 

·
Registered
Joined
·
374 Posts
Discussion Starter #12
jmorken thank you for the information, I'm surprised I didn't see your audio thread when I searched. Good job on that!

JMB that's good that your equipment is lasting you, I could see audio equipment really adding up if it keeps "failing to warm up" lol

Lazyguy I agree 100% on the head unit and speakers. I've got plans to upgrade those very soon, and I think I'll probably run them off a new head unit. When you say I'm over powered are you referring to the amp - sub relationship? Or just bass in general? I respect people's preferences on what they use for their likings, and personally I'd rather have too much bass and turn it down than to not be able to turn it up high enough.
 
1 - 12 of 12 Posts
Top