Sub Box Design / Configuration Advice
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Joined: May 2004
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From: Sunbury Oh
Please Advise! A few System Configuration Questions from a Novice...
I've purchased the following items for install in my '98 C5 corvette:
- Kenwood eXcelon 679 Head Unit
(5v preout, Mp3/CD, etc)
- 1 Pair of Infinity Reference 6 1/2" Speakers
(60w RMS/120w Peak)
- 1 MA Audio MA120XE 12" Sub
(350w RMS/700w Peak, Dual 4ohm Voice Coil, needs .75-1.25 Sealed space)
- MA Audio HK204SX 1200watt 4 channel Amplifier
(4x75wRMS@4ohm stereo, 4x125wRMS@2ohm stereo, 4x175wRMS@1ohm stereo, 4x300wRMS@.5ohm stereo, 2x600wRMS@1Ohm Bridged)
- Scosche Wiring Kit for 800+ watt amps
(2x17' Pair RCA Audio Cables, 17' 4-gauge power cable, 6' 8gauge power cable, 4' 8gauge ground cable, 17' Blue Remote Wire, ANL in-line fuse holder, fused distribution block (4 outlet), fuses & terminals)
- Bundle of 16 gauge speaker wire to run to fronts
- 1 Sheet of 8x4 3/4" MDF board
- LOTS of Dry wall screws, Liquid Nail, and Silicone Tubes
I've already installed the head unit and the front 6 1/2" speakers.
First the important questions:
-> Since the kit runs 4 gauge to the distribution block and then 8 gauge to the amp, is that going to be too small of a wire for that amp or is that fine? Same thing with the ground wire, I was always told that the bigger the better-is that big enough?
-> Since the Amp is pushing 75w by 4 channels into 4 ohm I've about decided to go with the front two channels pushing the fronts but wasn't sure if that would be a problem since they are only rated to 60w RMS on the speakers, Should I think more seriously about throwing some more 6 1/2s in the rear locations and tying them in with the fronts to run them at a 2ohm load (125w per channel)? Or should I stay at 4 ohms for quality?
-> Since I'll most likely being pushing the front two channels at 4 ohm stereo I'm planning to bridge the rear 2 channels to a 2 ohm load for the 12" sub. Is that a completely bad idea? I'm sure seperate amps would be best but for now this is what I've got work with. I'm not sure what kind of power would be pushed by bridging at a 2 ohm load since they only posted the advertised power at 1 ohm. Any ideas?
-> Where should I run the wires (RCA's, Power, Front Speakers)? I thought about going up the center console for most direct path or possibly the passenger side. Should I consider splitting the routing for any reason?
-> Should I allow the Head Unit to continue running the Stock Bose 'twiddlers' and stock Bose rear speakers (both of which I have confirmed are 4 ohms) off the head unit's 22rms load for 'fill' or will that just muddy up the sound? I've read a lot in the Corvette audio forums that seems to advertise against running the 2 rear panel speakers since thier location is barely adequate even for 'fill' (they are pretty much right at your head).
-> I'll be running the 12 in a sealed box made of 3/4" MDF with about 1 cubic foot of space. Do I need to use Poly fill fiber (or whatever it is called) for that space or is it fine without it?
-> Is the 16 gauge speaker wire enough to be used for the subs as well or do I need larger?
-> Oh! And one last question for my personal knowledge. What is the real benefit of have the 5v preouts on my head unit? Does that basically mean that the signal sent from it is stronger/louder than say one with a 2v? If so does that mean I just wouldn't need to crank the amp gains up as much to achieve the ideal volume matching?
Thanks in advance for any advice you can give!
- Kenwood eXcelon 679 Head Unit
(5v preout, Mp3/CD, etc)
- 1 Pair of Infinity Reference 6 1/2" Speakers
(60w RMS/120w Peak)
- 1 MA Audio MA120XE 12" Sub
(350w RMS/700w Peak, Dual 4ohm Voice Coil, needs .75-1.25 Sealed space)
- MA Audio HK204SX 1200watt 4 channel Amplifier
(4x75wRMS@4ohm stereo, 4x125wRMS@2ohm stereo, 4x175wRMS@1ohm stereo, 4x300wRMS@.5ohm stereo, 2x600wRMS@1Ohm Bridged)
- Scosche Wiring Kit for 800+ watt amps
(2x17' Pair RCA Audio Cables, 17' 4-gauge power cable, 6' 8gauge power cable, 4' 8gauge ground cable, 17' Blue Remote Wire, ANL in-line fuse holder, fused distribution block (4 outlet), fuses & terminals)
- Bundle of 16 gauge speaker wire to run to fronts
- 1 Sheet of 8x4 3/4" MDF board
- LOTS of Dry wall screws, Liquid Nail, and Silicone Tubes
I've already installed the head unit and the front 6 1/2" speakers.
First the important questions:
-> Since the kit runs 4 gauge to the distribution block and then 8 gauge to the amp, is that going to be too small of a wire for that amp or is that fine? Same thing with the ground wire, I was always told that the bigger the better-is that big enough?
-> Since the Amp is pushing 75w by 4 channels into 4 ohm I've about decided to go with the front two channels pushing the fronts but wasn't sure if that would be a problem since they are only rated to 60w RMS on the speakers, Should I think more seriously about throwing some more 6 1/2s in the rear locations and tying them in with the fronts to run them at a 2ohm load (125w per channel)? Or should I stay at 4 ohms for quality?
-> Since I'll most likely being pushing the front two channels at 4 ohm stereo I'm planning to bridge the rear 2 channels to a 2 ohm load for the 12" sub. Is that a completely bad idea? I'm sure seperate amps would be best but for now this is what I've got work with. I'm not sure what kind of power would be pushed by bridging at a 2 ohm load since they only posted the advertised power at 1 ohm. Any ideas?
-> Where should I run the wires (RCA's, Power, Front Speakers)? I thought about going up the center console for most direct path or possibly the passenger side. Should I consider splitting the routing for any reason?
-> Should I allow the Head Unit to continue running the Stock Bose 'twiddlers' and stock Bose rear speakers (both of which I have confirmed are 4 ohms) off the head unit's 22rms load for 'fill' or will that just muddy up the sound? I've read a lot in the Corvette audio forums that seems to advertise against running the 2 rear panel speakers since thier location is barely adequate even for 'fill' (they are pretty much right at your head).
-> I'll be running the 12 in a sealed box made of 3/4" MDF with about 1 cubic foot of space. Do I need to use Poly fill fiber (or whatever it is called) for that space or is it fine without it?
-> Is the 16 gauge speaker wire enough to be used for the subs as well or do I need larger?
-> Oh! And one last question for my personal knowledge. What is the real benefit of have the 5v preouts on my head unit? Does that basically mean that the signal sent from it is stronger/louder than say one with a 2v? If so does that mean I just wouldn't need to crank the amp gains up as much to achieve the ideal volume matching?
Thanks in advance for any advice you can give!
Last edited by Ssseeya; Jul 13, 2004 at 12:43 PM.
Le Mans Master
Joined: Dec 2002
Posts: 7,981
Likes: 37
From: Piedmont, SC Currently Own: 99 Nassau blue FRC. Previously Owned: 84,95,98 Indy Pace,01 Z06
I have a 12" box that fits in the center compartment I would sell for $95 shipped if you are interested!! It has black carpet!! I have my 12" in it at the present time, so I could send you pics if you are interested in how it looks! Jason
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Joined: Feb 2004
Posts: 63
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From: Jackson MS
re:
I am probably going to get blasted on some of my comments, but here goes. There are others on the forum that will probably have some better advice. Your questions are pretty generel stereo questions.. I hope some of my input helps!
-> Since the kit runs 4 gauge to the distribution block and then 8 gauge to the amp, is that going to be too small of a wire for that amp or is that fine? Same thing with the ground wire, I was always told that the bigger the better-is that big enough?
Yes, the bigger guage the better. I would never go smaller than 10 ga for amp power. The size needed depends on the power required by the system and the length of cable run. Your amps arent so large that you need anything bigger than 8 guage.
-> Since the Amp is pushing 75w by 4 channels into 4 ohm I've about decided to go with the front two channels pushing the fronts but wasn't sure if that would be a problem since they are only rated to 60w RMS on the speakers, Should I think more seriously about throwing some more 6 1/2s in the rear locations and tying them in with the fronts to run them at a 2ohm load (125w per channel)? Or should I stay at 4 ohms for quality?
I would stay with what you have planned. You can get more power with what you are mentioning, but I think it would be riskier. Remeber - Distortion kills speakers, not power.
-> Since I'll most likely being pushing the front two channels at 4 ohm stereo I'm planning to bridge the rear 2 channels to a 2 ohm load for the 12" sub. Is that a completely bad idea? I'm sure seperate amps would be best but for now this is what I've got work with. I'm not sure what kind of power would be pushed by bridging at a 2 ohm load since they only posted the advertised power at 1 ohm. Any ideas?
No problem bridging the amp for a sub. But the lower the ohm rating, the more stress (and heat) you are creating for your amp. The sub has a dual voice coil so you have some real possibilities with bridging it.
-> Where should I run the wires (RCA's, Power, Front Speakers)? I thought about going up the center console for most direct path or possibly the passenger side. Should I consider splitting the routing for any reason?
I would probably do the passenger side, but wait and see what someone else says here...
-> Should I allow the Head Unit to continue running the Stock Bose 'twiddlers' and stock Bose rear speakers (both of which I have confirmed are 4 ohms) off the head unit's 22rms load for 'fill' or will that just muddy up the sound? I've read a lot in the Corvette audio forums that seems to advertise against running the 2 rear panel speakers since thier location is barely adequate even for 'fill' (they are pretty much right at your head).
Take all the BLOSE out!!
I am a believer in having a soundstage and some rear fill. Get youself some 4.5" speakers for the stock real location and run them off your eXcelon HU. Fairly good speakers are of that size are not expensive.
-> I'll be running the 12 in a sealed box made of 3/4" MDF with about 1 cubic foot of space. Do I need to use Poly fill fiber (or whatever it is called) for that space or is it fine without it?
Either way. Poly fill is cheap, I ususally use it in any box I have. It will help the sound, and trick the sub into thinking it is a bigger box.
-> Is the 16 gauge speaker wire enough to be used for the subs as well or do I need larger?
Odds are you are going to have a short run from the amp to the sub. I would use some better quality wire than what came in a kit. What you have is fine though.
-> Oh! And one last question for my personal knowledge. What is the real benefit of have the 5v preouts on my head unit? Does that basically mean that the signal sent from it is stronger/louder than say one with a 2v? If so does that mean I just wouldn't need to crank the amp gains up as much to achieve the ideal volume matching?
You got it. Leave the gain down and let the higher (cleaner) voltage signal provide good sound. I woulndt have anything less than 5v pre-out if buying a new HU.
-> Since the kit runs 4 gauge to the distribution block and then 8 gauge to the amp, is that going to be too small of a wire for that amp or is that fine? Same thing with the ground wire, I was always told that the bigger the better-is that big enough?
Yes, the bigger guage the better. I would never go smaller than 10 ga for amp power. The size needed depends on the power required by the system and the length of cable run. Your amps arent so large that you need anything bigger than 8 guage.
-> Since the Amp is pushing 75w by 4 channels into 4 ohm I've about decided to go with the front two channels pushing the fronts but wasn't sure if that would be a problem since they are only rated to 60w RMS on the speakers, Should I think more seriously about throwing some more 6 1/2s in the rear locations and tying them in with the fronts to run them at a 2ohm load (125w per channel)? Or should I stay at 4 ohms for quality?
I would stay with what you have planned. You can get more power with what you are mentioning, but I think it would be riskier. Remeber - Distortion kills speakers, not power.
-> Since I'll most likely being pushing the front two channels at 4 ohm stereo I'm planning to bridge the rear 2 channels to a 2 ohm load for the 12" sub. Is that a completely bad idea? I'm sure seperate amps would be best but for now this is what I've got work with. I'm not sure what kind of power would be pushed by bridging at a 2 ohm load since they only posted the advertised power at 1 ohm. Any ideas?
No problem bridging the amp for a sub. But the lower the ohm rating, the more stress (and heat) you are creating for your amp. The sub has a dual voice coil so you have some real possibilities with bridging it.
-> Where should I run the wires (RCA's, Power, Front Speakers)? I thought about going up the center console for most direct path or possibly the passenger side. Should I consider splitting the routing for any reason?
I would probably do the passenger side, but wait and see what someone else says here...
-> Should I allow the Head Unit to continue running the Stock Bose 'twiddlers' and stock Bose rear speakers (both of which I have confirmed are 4 ohms) off the head unit's 22rms load for 'fill' or will that just muddy up the sound? I've read a lot in the Corvette audio forums that seems to advertise against running the 2 rear panel speakers since thier location is barely adequate even for 'fill' (they are pretty much right at your head).
Take all the BLOSE out!!
I am a believer in having a soundstage and some rear fill. Get youself some 4.5" speakers for the stock real location and run them off your eXcelon HU. Fairly good speakers are of that size are not expensive.
-> I'll be running the 12 in a sealed box made of 3/4" MDF with about 1 cubic foot of space. Do I need to use Poly fill fiber (or whatever it is called) for that space or is it fine without it?
Either way. Poly fill is cheap, I ususally use it in any box I have. It will help the sound, and trick the sub into thinking it is a bigger box.
-> Is the 16 gauge speaker wire enough to be used for the subs as well or do I need larger?
Odds are you are going to have a short run from the amp to the sub. I would use some better quality wire than what came in a kit. What you have is fine though.
-> Oh! And one last question for my personal knowledge. What is the real benefit of have the 5v preouts on my head unit? Does that basically mean that the signal sent from it is stronger/louder than say one with a 2v? If so does that mean I just wouldn't need to crank the amp gains up as much to achieve the ideal volume matching?
You got it. Leave the gain down and let the higher (cleaner) voltage signal provide good sound. I woulndt have anything less than 5v pre-out if buying a new HU.
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Joined: May 2002
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From: Clemson University SC
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Originally Posted by TexasTechEx
I would stay with what you have planned. You can get more power with what you are mentioning, but I think it would be riskier. Remeber - Distortion kills speakers, not power.
Distortion does not kill speakers in any way. Power kills speakers. This is a myth spread for far too long. It came about when people started cranking the gains on amps that made less than the power a speaker was rated for(for example, a 200 rms amp on a 300 rms speaker). The amp would clip heavily(thus distortion), and the increased power from clipping(close to 400 rms) would kill the speaker. This started the myth, and people all over propogated it to say that distortion kills speakers. The same type of situation happened with stiffening capacitors.
Anyway, as long as he is careful setting his gains to avoid overpowering the speakers, he will be fine with 75 rms per channel to just the front speakers.
I'll get around to replying to the rest of this post sometime...right now I need some sleep(it's 1:30 am after a long day).
