Help me out please!
11-12-2001, 03:12 PM
#1
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Help me out please!
Okay, first of all I must admit I'm no expert when it comes to car stereo stuff... so I go into Ultimate Electronics intending to buy an Infinity reference 10. However, they're out of them, and I ask the salesman what else they have in the same price range as the $85 reference subs.. he asks me what kind of amp I'm using and I tell him.. a DHD 400 watt max 2 channel amp. He tells me "Okay, so you realize your amp is probably running 50x2, as these knockoff companies usually lie about their power ratings. So, you should get some Rockford Fosgate HEs 8 ohm. You need some 8 ohm subs so that you can bridge your amp and it will knock the amp ohm rating down to 2, and the sub ohm rating to 4. You don't want to get the normal 4 ohm amps because it would decrease power output when you bridged it and they went down to 2 ohms." I know jack **** about ohm loads, is what he's saying right? I was just thinking of getting an Infinity Kappa online for $100 total, since it has an RMS of 200 and my amp is 400.. but he said since my amp isn't correct with the power rating, if I get a 4 ohm sub (like those Kappas) they will blow because my power will be too low. What do you guys think? Is it safe to get an Infinity Kappa, or should I go with an 8 ohm sub like he was saying? Thanks for reading this longass message, and any help you can provide would be greatly appreciated. I don't wanna end up buying a sub that I just blow immeadiately!
11-12-2001, 05:18 PM
#2
Re: Help me out please!
Originally posted by Neice Anne
Okay, first of all I must admit I'm no expert when it comes to car stereo stuff... so I go into Ultimate Electronics intending to buy an Infinity reference 10. However, they're out of them, and I ask the salesman what else they have in the same price range as the $85 reference subs.. he asks me what kind of amp I'm using and I tell him.. a DHD 400 watt max 2 channel amp. He tells me "Okay, so you realize your amp is probably running 50x2, as these knockoff companies usually lie about their power ratings. So, you should get some Rockford Fosgate HEs 8 ohm. You need some 8 ohm subs so that you can bridge your amp and it will knock the amp ohm rating down to 2, and the sub ohm rating to 4. You don't want to get the normal 4 ohm amps because it would decrease power output when you bridged it and they went down to 2 ohms." I know jack **** about ohm loads, is what he's saying right? I was just thinking of getting an Infinity Kappa online for $100 total, since it has an RMS of 200 and my amp is 400.. but he said since my amp isn't correct with the power rating, if I get a 4 ohm sub (like those Kappas) they will blow because my power will be too low. What do you guys think? Is it safe to get an Infinity Kappa, or should I go with an 8 ohm sub like he was saying? Thanks for reading this longass message, and any help you can provide would be greatly appreciated. I don't wanna end up buying a sub that I just blow immeadiately!
Okay, first of all I must admit I'm no expert when it comes to car stereo stuff... so I go into Ultimate Electronics intending to buy an Infinity reference 10. However, they're out of them, and I ask the salesman what else they have in the same price range as the $85 reference subs.. he asks me what kind of amp I'm using and I tell him.. a DHD 400 watt max 2 channel amp. He tells me "Okay, so you realize your amp is probably running 50x2, as these knockoff companies usually lie about their power ratings. So, you should get some Rockford Fosgate HEs 8 ohm. You need some 8 ohm subs so that you can bridge your amp and it will knock the amp ohm rating down to 2, and the sub ohm rating to 4. You don't want to get the normal 4 ohm amps because it would decrease power output when you bridged it and they went down to 2 ohms." I know jack **** about ohm loads, is what he's saying right? I was just thinking of getting an Infinity Kappa online for $100 total, since it has an RMS of 200 and my amp is 400.. but he said since my amp isn't correct with the power rating, if I get a 4 ohm sub (like those Kappas) they will blow because my power will be too low. What do you guys think? Is it safe to get an Infinity Kappa, or should I go with an 8 ohm sub like he was saying? Thanks for reading this longass message, and any help you can provide would be greatly appreciated. I don't wanna end up buying a sub that I just blow immeadiately!
First, i personally don't believe that the salesman understands ohms law. If i am correct, there can only be one impedance per cicuit. Therefor you can not have the subs at 4 ohms and the amp at 2 ohms. the impedance would be either 2 or four ohms for the entire cicuit. In short, i guess what iam saying is go with the one kappa for $100, your amp should have enough power to push the sub if you bridge the two channels together. Amp manufacturers usually rate their power output higher than it actually is, but i have never seen that large of a difference.
btw, maximadave if you are reading this, does this sound correct to you, i am not a certified installer, but i have done my fair share of installs, and have taken several classes in electronics.
11-12-2001, 09:26 PM
#3
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Re: Re: Help me out please!
Okay, thanks for the info.. the only problem is: I already have a nice Soundstream sub in this box, but it's a 2 sub box, and I'm just looking for another sub for the other spot. I used to have some other subs in there but they blew... I can't just get another Soundstream because the model I have in there is several years old and I don't know the model #.
First, i personally don't believe that the salesman understands ohms law. If i am correct, there can only be one impedance per cicuit. Therefor you can not have the subs at 4 ohms and the amp at 2 ohms. the impedance would be either 2 or four ohms for the entire cicuit. In short, i guess what iam saying is go with the one kappa for $100, your amp should have enough power to push the sub if you bridge the two channels together. Amp manufacturers usually rate their power output higher than it actually is, but i have never seen that large of a difference.
btw, maximadave if you are reading this, does this sound correct to you, i am not a certified installer, but i have done my fair share of installs, and have taken several classes in electronics. [/B][/QUOTE]
First, i personally don't believe that the salesman understands ohms law. If i am correct, there can only be one impedance per cicuit. Therefor you can not have the subs at 4 ohms and the amp at 2 ohms. the impedance would be either 2 or four ohms for the entire cicuit. In short, i guess what iam saying is go with the one kappa for $100, your amp should have enough power to push the sub if you bridge the two channels together. Amp manufacturers usually rate their power output higher than it actually is, but i have never seen that large of a difference.
btw, maximadave if you are reading this, does this sound correct to you, i am not a certified installer, but i have done my fair share of installs, and have taken several classes in electronics. [/B][/QUOTE]
11-12-2001, 09:40 PM
#4
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Well, I don't think the salesman new what he was talking about but he was attempting to make a valid point. Unfortunately he screwed up and tried to get technical when he didn't understand jack. The ohm load of two 8 ohm speakers bridged is 4 ohms. Now bridge a two channel amp and most often the amp sees half the speakers load. So a bridged amp fed 4 ohms will act as though it is operating into 2 ohms, but that is how it operates into 2 ohms stereo. Not two ohms bridged.
Your DHD amp may be fine for a pair of subs. I don't know their website, so help me out. Also, it is just as important to get a sub designed to work in the type and volume of enclosure that you have. Does the box have one or two chambers? Are they ported, sealed, bandpass? You need to measure the volume, length * width * average depth.
DHD sounds familiar. Is that Earthquake?
Your DHD amp may be fine for a pair of subs. I don't know their website, so help me out. Also, it is just as important to get a sub designed to work in the type and volume of enclosure that you have. Does the box have one or two chambers? Are they ported, sealed, bandpass? You need to measure the volume, length * width * average depth.
DHD sounds familiar. Is that Earthquake?
11-12-2001, 10:47 PM
#5
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[QUOTE]Originally posted by jmax
[B]Well, I don't think the salesman new what he was talking about but he was attempting to make a valid point. Unfortunately he screwed up and tried to get technical when he didn't understand jack. The ohm load of two 8 ohm speakers bridged is 4 ohms. Now bridge a two channel amp and most often the amp sees half the speakers load. So a bridged amp fed 4 ohms will act as though it is operating into 2 ohms, but that is how it operates into 2 ohms stereo. Not two ohms bridged.
Your DHD amp may be fine for a pair of subs. I don't know their website, so help me out. Also, it is just as important to get a sub designed to work in the type and volume of enclosure that you have. Does the box have one or two chambers? Are they ported, sealed, bandpass? You need to measure the volume, length * width * average depth.
http://www.dhdusa.com/5.htm#NTX-2003 check this page out, I think mine is much like an NTX-2006.. as for my box.. 2 chambers I believe (2 places for subs... 2 portholes..) It's a bandpass box. I'm not sure about the measurements off the top of my dome but... should be able to handle any of the lower end subs I'm considering, as they don't need tons of clearance...
[B]Well, I don't think the salesman new what he was talking about but he was attempting to make a valid point. Unfortunately he screwed up and tried to get technical when he didn't understand jack. The ohm load of two 8 ohm speakers bridged is 4 ohms. Now bridge a two channel amp and most often the amp sees half the speakers load. So a bridged amp fed 4 ohms will act as though it is operating into 2 ohms, but that is how it operates into 2 ohms stereo. Not two ohms bridged.
Your DHD amp may be fine for a pair of subs. I don't know their website, so help me out. Also, it is just as important to get a sub designed to work in the type and volume of enclosure that you have. Does the box have one or two chambers? Are they ported, sealed, bandpass? You need to measure the volume, length * width * average depth.
http://www.dhdusa.com/5.htm#NTX-2003 check this page out, I think mine is much like an NTX-2006.. as for my box.. 2 chambers I believe (2 places for subs... 2 portholes..) It's a bandpass box. I'm not sure about the measurements off the top of my dome but... should be able to handle any of the lower end subs I'm considering, as they don't need tons of clearance...
11-13-2001, 08:52 AM
#6
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Yeah, it sounds like that amp is pretty low on the power spectrum. 80 X 2 at 2 ohms. That's almost on the same line that they say 40 X 2 at 4 ohms. Almost no amp truly doubles output when you cut resistance(impedance) in half. What is the factory fuse size? I'm guessing between 15 and 25 amps. At 15 amps you might have an amp with 50 watts RMS at 4 ohms, maybe 150 bridged into 4 ohms. 250 to 300 watts RMS bridged if it's a 25 amp factory fuse. Never increase the factory fuse, unless you want the amp to melt.
If it is a bandpass box the only holes in the wall of the box should be for ports. Their should be no woofer, or woofers visible or accessible without a plexi window. And no average to moderate priced box with a plexi window can be considered good as the plexi is generally 3/16 to 1/4 inch thick, will flex like crazy, and introduces four more edges where a leak is likely.
If it is a simple ported box then the woofer cones fire directly into the vehicle, and through a port. Both ported and bandpass will be very dificult to find a woofer that will match the box volume and tuning frequency. The box volume can easily be decreased with filler material, but increasing the volume could be difficult. Finding a woofer to mount in the hole is easy, with minor modification to the box.
Many newer woofers can match the output of an older woofer that needed a bandpass or ported box. Without the difficulty of tuning a box. In addition to that most manufacturers now post box recommendations on the net. But finding a woofer that will match the output and tuning of your current woofer, in the same box, will most likely waste time that you could otherwise spend designing and building an enclosure for a new woofer, or for the single woofer you already have in your possession. And it sounds as though your amp is insufficient for two woofers, in fact will barely vibrate a single woofer.
If it is a bandpass box the only holes in the wall of the box should be for ports. Their should be no woofer, or woofers visible or accessible without a plexi window. And no average to moderate priced box with a plexi window can be considered good as the plexi is generally 3/16 to 1/4 inch thick, will flex like crazy, and introduces four more edges where a leak is likely.
If it is a simple ported box then the woofer cones fire directly into the vehicle, and through a port. Both ported and bandpass will be very dificult to find a woofer that will match the box volume and tuning frequency. The box volume can easily be decreased with filler material, but increasing the volume could be difficult. Finding a woofer to mount in the hole is easy, with minor modification to the box.
Many newer woofers can match the output of an older woofer that needed a bandpass or ported box. Without the difficulty of tuning a box. In addition to that most manufacturers now post box recommendations on the net. But finding a woofer that will match the output and tuning of your current woofer, in the same box, will most likely waste time that you could otherwise spend designing and building an enclosure for a new woofer, or for the single woofer you already have in your possession. And it sounds as though your amp is insufficient for two woofers, in fact will barely vibrate a single woofer.
11-13-2001, 08:47 PM
#7
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Well despite what it would seem from the technical data, the amp seems very capable of pushing subs... I used to have 2 10's in there and the difference when they were in there was significantly different than from when just my Alpine is goin (with it's own amp) and now that I just have the Soundstream in there, the difference is significant from just the Alpine and is also less hard than when I had the 2 other subs in there. Anyway, do you have any specific reccomendations for me regarding what ohm of sub I should get, or maybe just what sub would be good in a bandpass box as I described? If so I'd appreciate it!
11-13-2001, 08:57 PM
#8
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Sorry, I prefer sound quality instead of sound quantity. So I have no suggestions for bandpas subs. I am sure that any sub sounds better than none at all. People have looked at me with dismay when I have told them that a single eight in a sealed box can seriously thump until they heard one of the old subs I built for my wife. It's all relative. If your alpine is yor headunit it is 5-12 watts RMS per channel. So 50-120 watts RMS will be about twice as loud.
11-14-2001, 07:54 AM
#9
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Originally posted by jmax
Sorry, I prefer sound quality instead of sound quantity. So I have no suggestions for bandpas subs. I am sure that any sub sounds better than none at all. People have looked at me with dismay when I have told them that a single eight in a sealed box can seriously thump until they heard one of the old subs I built for my wife. It's all relative. If your alpine is yor headunit it is 5-12 watts RMS per channel. So 50-120 watts RMS will be about twice as loud.
Sorry, I prefer sound quality instead of sound quantity. So I have no suggestions for bandpas subs. I am sure that any sub sounds better than none at all. People have looked at me with dismay when I have told them that a single eight in a sealed box can seriously thump until they heard one of the old subs I built for my wife. It's all relative. If your alpine is yor headunit it is 5-12 watts RMS per channel. So 50-120 watts RMS will be about twice as loud.
11-14-2001, 08:40 AM
#10
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" If your amp is truly stable at 2 ohms then you want two four ohm speakers. Wire them in parallel, and then you have your two ohm load."
It two ohm stereo stable. That is different from being 2 ohm bridged stable. If you parallel wire two subs for a 2 ohm load you need an amp that is stable into a bridged 2 ohm load. Your amp is stereo 2 ohm stable, but not stereo 1 ohm stable as it would need to be to push that load.
It two ohm stereo stable. That is different from being 2 ohm bridged stable. If you parallel wire two subs for a 2 ohm load you need an amp that is stable into a bridged 2 ohm load. Your amp is stereo 2 ohm stable, but not stereo 1 ohm stable as it would need to be to push that load.