Calling the audio experts, please check my math/sanity...

[Gwerner74]

Truck in question is a 2015 RAM 2500 with the stock 6 speaker system and 8.4 radio. I wish an aftermarket head unit was in the cards for me right now but it's not so I'm trying to make the best of what I have at the moment.

So, in stock configuration:
- The dash speakers are 8 ohms and the front door speakers are 4 ohm. Since they're wired in parallel that's an impedance of 2.67 ohms per channel presented to the head unit.
- The rear door speakers are 4 ohms and are their own separate channels presenting 4 ohms each to the head unit.

I'm pretty sure I'm good so far, does anything sound off about my calculations or assumptions?

Now on to the check my math and sanity part.

I replaced all 6 speakers with JL Audio C2 series speakers, each one is rated at 4 ohms. So in my new configuration the dash speakers are 4 ohms as well as the front doors. That results in a 2 ohm load per channel presented to the head unit. I plan on doing the 4 ohm resistor mod to the dash speakers which will put me back to presenting a 2.67 ohm load per channel to the head unit, and the rear doors are still presenting the same 4 ohms per channel as the stock configuration.

The big question is, would there be any benefit to balancing the impedance between the front and rear channels or am I splitting hairs here? Seems like an imbalance having the front channels at a lower impedance/hotter signal than the rear channels. If there would be a benefit to balancing the impedance I would do the 4 ohm resistor mod to both the dash and front door speakers. Being they're in parallel that would present a 4 ohm load per channel to the head unit matching the rear.

Does all of that math sound right? Just trying to baseline the system before I tackle adding my amp and subs back into the equation. Since I'll be tapping the rear speakers for the sub amp input I know I'll have to take the input impedance of the amplifier into account for the rear channels, just want to have a solid baseline to work off of going forward. Thanks for your time!

 

[Black-Wolf]

BLUF: Your math is ok. Not sure it's worth the effort though - four ohms is the industry standard for automotive speakers, and most people just go with stock. As I'm not sure what you have for an amp (or if you have one), I don't know how many channels you actually have - but I'm assuming just four (FL, FR, RL, RR). By balancing the ohm load, you should be able to get pretty close to what is a "balanced" audio sound stage - where you (as the driver) are in the center of the stage and the music is around you and maybe a little to the front.

I'd look at trying to get 4-ohms on each channel. Your HU should be rated for that - and if your speakers are rated at 4-ohms, that'll keep them alive a lot longer than running a lower impedance on them.

Here's the detailed explanation:

1) Ohms. You want the speakers to be as close in impedance as possible to all the other speakers, or wired so that they're the same or close to the same.

2) RMS (Root Mean Square): This is the amount of power (on average) that your speakers can handle (there's also a peak - which is the max power they can handle for short periods of time - usually about 1.5x to 2.5x the RMS). Your amp or head unit will be rated to push a max amount of wattage- say 50w - so your RMS for the speakers you add can be a little lower as long as your peak is more than 50watts. A lot of this depends on how loud you play your system - keeping in mind that the louder you play, the more wattage you're pushing, and if you run a 50w/channel amp with speakers rated at 25w RMS and 50w peak, you ARE going to blow them eventually. I know that is a little wordy and confusing. Basically, try to match your RMS to your amp/head unit, and if you have to put lower wattage speakers in, make sure the peak is going to be high enough to more than handle the amp/HU wattage. Also, while you can put speakers in that have a higher RMS than your amp/HU can push, if you go to high, they'll sound too quiet. You won't blow them, but you'll have degraded audio in lower volumes.

3) Sensitivity: A speaker with a higher sensitivity rating (in dB) sounds louder at 1' than one with a lower rating (AT the ohms and wattage that the speaker is rated for - so regardless of the speaker's wattage and impedance, if it has 91dB sensitivity, it will sound louder than another speaker at 85dB sensitivity - ASSUMING that they are wired into a system that pushes the wattage at the rated impedance for that speaker!). The impedance will affect this because if you push a speaker harder by lowering its impedance, it will sound louder, and you will eventually blow it. The wattage a speaker can handle, is based off of the impedance it has - so a 25w speaker @ 4 ohms, becomes a 17w speaker @ 3 ohms. It will sound a little louder, but your amp/HU may be pushing too much to it - so, it winds up dying a lot sooner.

Your HU/amp is also rated for a specific impedance as well - and typically, if you have a higher impedance speaker your wattage/channel decreases for the HU/amp.

Does that help confuse you more? Trust me: I'm an electrician and it confuses the heck out of me too sometimes.

V/R

 

[Atcer2018]

I’m humbled at the knowledge you two gentlemen have. Aside from the technical mathematics when the OP states they will be adding an amp back into the system do you mean a mono amp(s) for the sub(s) or a four channel amp for the non subs? If you are adding a four channel amp into the system is that four channel bi-amp capable? If it is you could use the head unit to drive the rear speakers and use the four channel in bi-amp mode to drive the four front speakers negating a need to balance the system with all 4 ohm speakers.

 

[BWL]

Word of warning that the dash speakers at 4ohms may be a bit too much. Most guys opt to add a resistor to the dash speakers to cut a few db and keep them more in line with the door speaker volume.

 

[Gwerner74]

BLUF: Your math is ok. Not sure it's worth the effort though - four ohms is the industry standard for automotive speakers, and most people just go with stock. As I'm not sure what you have for an amp (or if you have one), I don't know how many channels you actually have - but I'm assuming just four (FL, FR, RL, RR). By balancing the ohm load, you should be able to get pretty close to what is a "balanced" audio sound stage - where you (as the driver) are in the center of the stage and the music is around you and maybe a little to the front.

I'd look at trying to get 4-ohms on each channel. Your HU should be rated for that - and if your speakers are rated at 4-ohms, that'll keep them alive a lot longer than running a lower impedance on them.

Here's the detailed explanation:

1) Ohms. You want the speakers to be as close in impedance as possible to all the other speakers, or wired so that they're the same or close to the same.

2) RMS (Root Mean Square): This is the amount of power (on average) that your speakers can handle (there's also a peak - which is the max power they can handle for short periods of time - usually about 1.5x to 2.5x the RMS). Your amp or head unit will be rated to push a max amount of wattage- say 50w - so your RMS for the speakers you add can be a little lower as long as your peak is more than 50watts. A lot of this depends on how loud you play your system - keeping in mind that the louder you play, the more wattage you're pushing, and if you run a 50w/channel amp with speakers rated at 25w RMS and 50w peak, you ARE going to blow them eventually. I know that is a little wordy and confusing. Basically, try to match your RMS to your amp/head unit, and if you have to put lower wattage speakers in, make sure the peak is going to be high enough to more than handle the amp/HU wattage. Also, while you can put speakers in that have a higher RMS than your amp/HU can push, if you go to high, they'll sound too quiet. You won't blow them, but you'll have degraded audio in lower volumes.

3) Sensitivity: A speaker with a higher sensitivity rating (in dB) sounds louder at 1' than one with a lower rating (AT the ohms and wattage that the speaker is rated for - so regardless of the speaker's wattage and impedance, if it has 91dB sensitivity, it will sound louder than another speaker at 85dB sensitivity - ASSUMING that they are wired into a system that pushes the wattage at the rated impedance for that speaker!). The impedance will affect this because if you push a speaker harder by lowering its impedance, it will sound louder, and you will eventually blow it. The wattage a speaker can handle, is based off of the impedance it has - so a 25w speaker @ 4 ohms, becomes a 17w speaker @ 3 ohms. It will sound a little louder, but your amp/HU may be pushing too much to it - so, it winds up dying a lot sooner.

Your HU/amp is also rated for a specific impedance as well - and typically, if you have a higher impedance speaker your wattage/channel decreases for the HU/amp.

Does that help confuse you more? Trust me: I'm an electrician and it confuses the heck out of me too sometimes.

V/R

Thanks for the reply! I’m a very out of practice former electronics technician so I’m pretty much relearning everything I’ve forgotten over the years. You are correct in your assumption, just dealing with 4 channels, (FL, FR, RL, RR). Using the stock 8.4 head unit, no amp at this time.

As my system stands right now the FL and FR channels are at 2 ohms each, 4 ohm dash and 4 ohm door speakers wired in parallel. I’ll do the resistor mod next week once my resistors from Digikey arrive. That’ll push the front channels back to 2.67 ohms which is what they were with the factory speakers. I’ll see how it sounds and then go from there. I’ll probably just fade to the rear. Bit rather than mess with balancing the load front and rear.

 

[IDSandman]

Oh boy. Are you not amping the fronts/door/dash rear doors? Adding a sub without amping those/some is not going to sound balanced. Adding a dsp amp like audio control to the fronts and rewire the dash, removing them from parallel to dedicated will make a ton of difference acoustically. Esp with a sub. The kicker key in bi amp is a great way to achieve this as well.

 

[Gwerner74]

Oh boy. Are you not amping the fronts/door/dash rear doors? Adding a sub without amping those/some is not going to sound balanced. Adding a dsp amp like audio control to the fronts and rewire the dash, removing them from parallel to dedicated will make a ton of difference acoustically. Esp with a sub. The kicker key in bi amp is a great way to achieve this as well.

I’ve run a sub without amping the mains in multiple vehicles over the years with no issues.

 

[IDSandman]

I’ve run a sub without amping the mains in multiple vehicles over the years with no issues.

It won’t have issues but sound very imbalanced and sub heavy. I prefer to build balanced systems. The stock head unit doesn’t have enough power to run aftermarket speakers efficiently. Plus the parallel system sounds like garbage.

 

[Gwerner74]

It won’t have issues but sound very imbalanced and sub heavy. I prefer to build balanced systems. The stock head unit doesn’t have enough power to run aftermarket speakers efficiently. Plus the parallel system sounds like garbage.

I hear ya, my ultimate goal down the road will be to add a 6 channel amp to drive the doors and dash speakers but it’s just not in the cards at the moment so I’m trying to make the best of what I have to work with right now.

 

[IDSandman]

I hear ya, my ultimate goal down the road will be to add a 6 channel amp to drive the doors and dash speakers but it’s just not in the cards at the moment so I’m trying to make the best of what I have to work with right now.

I hear ya man. Good luck with the build!

 

[14ramdjh]

sorry, i dont get it. the ram trucks, i would consider very noisy. it seems to me you are going for a high end audio experience that i would use at home. i have the same unit in my ram and i am very happy with it. the sound proofing in these trucks totally sucks. lets start a Theard on sound proofing

 

[MrTinkertrain]

I will just say wow! You gentleman really can make things sound amazing even if it can confuse the hell out of you! There is another option you could try. Leave out the dash speakers all together and either use those holes for a set of tweeters or mount the tweeters in the doors. Assuming you went with components in the front doors. That’s what I did with mine and ran the front and rear off a 4 channel amp and subs off their own mono amp. All with the stock head unit and sounds pretty nice. Sound deadening however really is a must! A pain to strip the truck of everything but so worth the time and the beer!

 

[Atcer2018]

Sound deadening however really is a must! A pain to strip the truck of everything but so worth the time and the beer!

You got that right! Most would be surprised how much a few 6x8 inch strips in the doors and rear of the cab quiet the interior.

 

[BWL]

sorry, i dont get it. the ram trucks, i would consider very noisy. it seems to me you are going for a high end audio experience that i would use at home. i have the same unit in my ram and i am very happy with it. the sound proofing in these trucks totally sucks. lets start a Theard on sound proofing

Jack's Full Dynamat Build

Goal: full dynamat, dynaliner, dynapad and hoodliner build over next few weeks I will post pics and add comments along the way. Any questions, just ask! Dynamat and Dynapad full interior BEFORE roof - used 71 sq ft for each.

www.ramforum.com

A bit of an older thread, but pretty thorough.

 

[Tominator223]

Olboy. You smart math guys , mean I shouldn’t have put those kenwood 8ohm house speakers in my trunk in the 80’s. . My 2cents