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Discussion Starter #1
I have a few amps, two of them do 2-ohm (4 channel) and one has 4 ohms (5 channel) output. I'd like to use the 5 channel amp to keep things clean and neat.

Questions.
1. What OHM sub's should I invest in? Is there a sound difference between a 4 and 2 OHM sub?
2. I see videos of people wiring up sub's in series and parallel with parallel having less impedance; can you take a 4-ohm sub and wire it so it goes down to 2-ohm impedance using parallel (probably a dumb question)?
3. If I use the 5 channel amp that has the 4-ohm output and get 2-ohm speakers is that okay, and will it sound good?
4. Anyone have recommendations for 10" sub's that won't break the bank? I really don't want to spend over $100 for a sub. I have a box with 3 open 10" sub holes in it I'd like to use.

Thank you for your help in advance.
 

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I have a few amps, two of them do 2-ohm (4 channel) and one has 4 ohms (5 channel) output. I'd like to use the 5 channel amp to keep things clean and neat.

Questions.
1. What OHM sub's should I invest in? Is there a sound difference between a 4 and 2 OHM sub?
2. I see videos of people wiring up sub's in series and parallel with parallel having less impedance; can you take a 4-ohm sub and wire it so it goes down to 2-ohm impedance using parallel (probably a dumb question)?
3. If I use the 5 channel amp that has the 4-ohm output and get 2-ohm speakers is that okay, and will it sound good?
4. Anyone have recommendations for 10" sub's that won't break the bank? I really don't want to spend over $100 for a sub. I have a box with 3 open 10" sub holes in it I'd like to use.

Thank you for your help in advance.
When I was around 14 or 15 years old, I began the journey of partaking in performance audio and learned quite a bit about speakers and amps through my dad. This was before I learned that speakers don't make your car faster lmao, although they do make the ride fun!

1. This will be a 4 part answer (a, b, c, d) and each one builds upon the last. All of them together offer the holistic view of the answer to your question. Hope you like Ohms Law lol.

A) Your question depends a lot on the capabilities of the amp you have and/or want to run. The amp is designed and created to drive a speaker within a certain max power level (watts). 'Watts' is calculated by (Voltage) X (Amperage). An amplifier manufacturer designs an amp to drive a speaker within that certain wattage limit/rating as shown on the case. This limit is typically enforced upon the amp due to manufacturer and design requirements, amplifier circuitry design, internal component quality and specifications, input voltage/current limitations, etc.

B) Both speakers and amps carry an OHM rating, but mean very different things. The resistance/ohm rating given on the speaker is the actual resistance of the speaker/subwoofer coil. This is pretty close to constant, and doesn't change.

C) The resistance/ohm rating given on the output channel of an amplifier is more or less intended to be a warning rather than a rating. Attaching a speaker with a resistance value lower than the rating 'can' damage the speaker driver circuitry inside the amplifier. By enforcing a load resistance rating at the amp itself, the manufacturer designs the circuit in hopes that the attached load will stay as close to this as possible. Remember, when resistance drops, current increases. By enforcing the load resistance limit to say, 4 ohms, via a 'label' on the back of the amp lol, the manufacturer hopes that the maximum amplifier driver current will stay below a certain level and not be exceeded. The second you attach a lower-than-rated resistive load to the amplifier, RMS current levels will increase across the spectrum of operation. When the amplifier driver circuitry attempts to drive the speaker at a high level, it might actually do OK for a while but the current carrying capabilities of the amplifier output will be exceeded sooner than expected. Transistors do not like this :)

D) By increasing the resistance of the speaker at the amplifier output, you lower the total driven amperage of the driver circuit, but increase the amount of heat that needs to be absorbed by the speaker. Decreasing speaker resistance has the opposite effect, the amplifier takes the brunt of the heating and current increase, and will burn up components if allowed to be driven out of range for too long. You could probably run 2 ohm speakers on a 4 ohm rated amp forever, as long as you never turn the volume knob up above 3/4 of the way. But if you have a 2 ohm amp and 2 ohm speakers, these are designed to work together.


2. Resistance/ohm rating of a speaker is determined by the coil material and winding process. There is nothing that you can do to change a 4 ohm sub into a 2 ohm or vice versa. Also, wiring subs up in series is stupid and honestly a crappy way of trying to run 2 subs. You are intentionally cutting the voltage and current available from a single channel in half across both speakers. Unless lower volume and thump is what you are after, it's best to do 1 channel per sub, or bridge a 2 channel amp together to double the available channel current to a single sub.


3. Refer to answer #1. Speaking to the sound quality, as I realize I didn't answer this in #1, when it comes to subwoofers the lower the better. The lower rating just means that the speaker is able to be driven harder with more current than a comparable 4 ohm sub. If the speaker is designed properly, has a good cone and supporting materials, and is coupled to a good quality amplifier, a 2 ohm sub will out perform a 4 ohm any day.


4. Sorry, I've never ran subs smaller than 12 inch!


One more little nugget of good information! Subs sound the best when they aren't allowed to exceed RMS design power, basically half of their rating. Any higher and you begin to enter distortion. You want to double the rating of the speaker in comparison of the amp. If you have a 600 watt amp, buy a 1200 watt speaker. At max volume, short of any frequency band distortion of the incoming audio signal from a source, you will not be able to distort that subwoofer at all. It will sound clean and loud all the way to max volume. Also, try not to increase the amp gain knob above 50-75%. Beyond that, you also invite distortion.



Happy thumping!
 

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Civic turbo Hx/Ex
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Discussion Starter #4
Holy cow that's a great explanation, thank you for that. So, when you say to get a speaker that is designed for double the amp rating you are referring to RMS or max wattage? I honestly don't know what size amps they are but will go out there and check. I'm looking to put these in my Toyota 4runner, so the speed isn't necessary. ;) I miss the thump.
 

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Discussion Starter #6
The first amp is infinity reference 7541a, 4 channel 111 watts x4 continuous or RMS. Then it says 111, 139, and 278 watts at 2 or 4 ohm... Not too sure what that means, please explain why it has all the different power wattages.

The second amp is an MB Quart PAB 5400, 5 channel, Power Handling: 4 x 55W RMS + 1 x 200W RMS @ 4 Ohm, or 4 x 80W RMS + 1 x 300W RMS @ 2 Ohm.

I guess the 2nd amp is better? So I should get a sub that can handle 600W?
 

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Discussion Starter #7
I also have a 2 channel cadence amp 300W 100RMS x 2 channels @ 4Ohm that I've used in the past with the box with the 3 open speaker slots. I bridged the wires to one input for my 3 JL audio 10" speakers.
 

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The first amp is infinity reference 7541a, 4 channel 111 watts x4 continuous or RMS. Then it says 111, 139, and 278 watts at 2 or 4 ohm... Not too sure what that means, please explain why it has all the different power wattages.

The second amp is an MB Quart PAB 5400, 5 channel, Power Handling: 4 x 55W RMS + 1 x 200W RMS @ 4 Ohm, or 4 x 80W RMS + 1 x 300W RMS @ 2 Ohm.

I guess the 2nd amp is better? So I should get a sub that can handle 600W?
2nd amp is "technically" better, because of the higher sub output. With it being a 5 channel and the specs listed, it looks like the 4 channels at the lower wattages pass through a different filter set (mid and high pass combined filter) and it has a dedicated low pass filter that feeds a more powerful driver for only a sub. Typically, this is what this means. What it means for you, is that if you are looking for ONLY a sub amplifier, you have to leave the other 4 channels unused and only use the 5th dedicated amp channel. If you hooked or bridged the other 4 channels to a single or multiple subs, you wouldn't get low bass from them, only the mid and high parts of the audio spectrum. If you are using the 300w channel, yes get a 600w sub for the best audio quality!

The reason the first amp has 3 wattage ratings, is due to the variance in resistance allowance that you might hook to the channels, as well as potential ways you could bridge the channels together. That amp was actually not intended to be a sole subwoofer driver type amp, and is really more for a multi-speaker car setup with 1 speaker at each of the 4 interior corners, powering those speaker across the full audio spectrum. With a subwoofer attached, the mid and high range will still be audible, but will not be as clear as with smaller speakers designed for mid or high range audio output. Honestly, this amp would be best to power some really good quality 8" or 6x9" 3 way speakers that have 3 full integrated speakers into the housing that cross the spectrum, like this:

speakers2.jpg


speakers1.jpg
 

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I also have a 2 channel cadence amp 300W 100RMS x 2 channels @ 4Ohm that I've used in the past with the box with the 3 open speaker slots. I bridged the wires to one input for my 3 JL audio 10" speakers.
Out of all the amps you posted, this one would be the best candidate to solely drive subwoofers. If you are using the existing vehicle speakers wired to your head unit to provide the mid and high sound, then run the sub out RCA's to this amp. Bridge the two channels, get a large 10" or 12" sub and the largest box you can fit in the area you plan to put the box, but do NOT use a box with bass ports if the box is large or if installing them into an open interior vehicle design with no closed trunk.

Bass ports in speaker boxes are used to exhaust air that is being pounded/oscillated by the sub cone, to be used within the confines of your actual vehicle space (like a trunk) to simulate a larger closed box. People who drive SUVs with an open trunk concept can seriously notice the thumpage of their subs in ported boxes decrease when they roll down the windows. Closed, large, well sealed at the edge boxes made of high quality thick MDF supports the BEST bass sound on lower powered subwoofer systems (<1500watts).

I would usually destroy or equal larger, more powerful systems that used ported boxes with my 600W single channel Pioneer amp with a 1200W Sony sub in a very large high quality box in the back of my Blazer. Most people couldn't believe the noise coming from this single sub on full volume. Oh the good old days!
 

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