If I'm going to filter the fronts, then why not filter the rears, and send all the bass to the sub?
So what would be the best solution here? I don't want to change any speakers, just add a sub. Would it be best to buy/make an amp for the stock speakers and run them with an active HP filter, and have a matching slope LP for the sub?
I noticed that the rears add a lot to the overall sound of the system, so I don't want to disconnect them.
I guess there are different schools of thought on active vs. passive filters. Amping the fronts would probably improve the sound regardless, so if you get the filters for free, there you go. If I were you I'd try the $10 bass blockers first to see if it helps.
remember that if you use active filters on the front and passive on the sub, the sub will be 90 degrees out of phase with the fronts. May not be noticeable at such low frequency and with the sub far away, but it will be there on paper if you're a stickler
As for the rears, i agree that they add depth. Not filtering them could help you isolate the distortion, and if you're worried about missing some frequencies, that might help.
remember that if you use active filters on the front and passive on the sub, the sub will be 90 degrees out of phase with the fronts. May not be noticeable at such low frequency and with the sub far away, but it will be there on paper if you're a stickler
As for the rears, i agree that they add depth. Not filtering them could help you isolate the distortion, and if you're worried about missing some frequencies, that might help.
I understand not wanting to spend much money but you are asking for to much from to little. In car audio it is always worth spending a few extra dollars for a better product rather then buying junk.
You don't have to spend huge amounts of money to get good SQ but you do have to spend some.
I could go on about what you should do but I don't think it will make a big difference because you arn't willing to spend money on reasonable products.
If you want to get a good sound you are going to have to upgrade some basic items. One is your sub amp. From what you are saying you are pushing your amp to the limit just to get bass. This should never be. My guess is that you are clipping that amp on loud bass notes. If you want your sub to match the rest of your system you are going to have to set it up corretly. If you have an O-scope it is easier to do but I am guessing you don't so here is how to do it. Disconnect your subs and listen to your stock system. Now flatten the EQ. I would recomend you dont touch the eq at all. Now listen to your system. Before you start setting up your sub I want you to listen how loud your system goes before it distorts. My guess is it will get pretty loud. Now that you have a mental image of when the system distorts you can tell if your sub or system is distorting. Now turn the gain and bass boost all the way down on your sub amp and hook your subs up. Play your system at a normal listening volume and start turning up your gain until the sub blends with your speakers. If you max the gain and have still not got enough bass then your amp is probebly a little small to be pushing your subs. You can make up for this a bit by turning up the boost about half way and turning your gain down to about half. From here turn the gain up till it matches you interiors. If you still max the gain turn it down a bit and leave it. That is about as much bass as you will be able to safely get out of your setup. This is all done by ear. Using an RTA is a waste until you have some way to truly tune your system.
If you are not satisfied with the sound at this point you are going to need to upgrade. Pushing your equipment beyond this point is going to lead to clipping and blown amps and subs.
If you find that your interior speakers distort at a level that isn't loud enough for you then you will have to upgrade to an external amp. The distortion you are hearing is going to be from your amps headunit, NOT from your speakers themselves. Even if you add bass blockers your amp is still going to be distorting at the same level.
You don't have to spend huge amounts of money to get good SQ but you do have to spend some.
I could go on about what you should do but I don't think it will make a big difference because you arn't willing to spend money on reasonable products.
If you want to get a good sound you are going to have to upgrade some basic items. One is your sub amp. From what you are saying you are pushing your amp to the limit just to get bass. This should never be. My guess is that you are clipping that amp on loud bass notes. If you want your sub to match the rest of your system you are going to have to set it up corretly. If you have an O-scope it is easier to do but I am guessing you don't so here is how to do it. Disconnect your subs and listen to your stock system. Now flatten the EQ. I would recomend you dont touch the eq at all. Now listen to your system. Before you start setting up your sub I want you to listen how loud your system goes before it distorts. My guess is it will get pretty loud. Now that you have a mental image of when the system distorts you can tell if your sub or system is distorting. Now turn the gain and bass boost all the way down on your sub amp and hook your subs up. Play your system at a normal listening volume and start turning up your gain until the sub blends with your speakers. If you max the gain and have still not got enough bass then your amp is probebly a little small to be pushing your subs. You can make up for this a bit by turning up the boost about half way and turning your gain down to about half. From here turn the gain up till it matches you interiors. If you still max the gain turn it down a bit and leave it. That is about as much bass as you will be able to safely get out of your setup. This is all done by ear. Using an RTA is a waste until you have some way to truly tune your system.
If you are not satisfied with the sound at this point you are going to need to upgrade. Pushing your equipment beyond this point is going to lead to clipping and blown amps and subs.
If you find that your interior speakers distort at a level that isn't loud enough for you then you will have to upgrade to an external amp. The distortion you are hearing is going to be from your amps headunit, NOT from your speakers themselves. Even if you add bass blockers your amp is still going to be distorting at the same level.
You guys seem to think it's ok to crossover a sub at 80hz and the fronts at 80hz. This is not true!!! If you are crossing over the sub at 80hz there are two huge problems. One is that the slope will let in freq. above 80hz. The second is that the second harmonic of 80hz is 160hz which is easily locatable. The ideal setting is 60hz and below for a sub so that the filter has almost no output at 80hz and the second harmonic is at a point closer to 80hz.
My sub is crossed over at 40hz with a 12db slope. I am not recomending this to you because you have such a basic system. I am saying that the lower you can crossover your sub the better. Which is the same for your fronts. The lower you can play them the better.
Also your crossover points don't have to be the same for sub and interiors due to the huge cabin gain. Many times the best settings are very different.
My sub is crossed over at 40hz with a 12db slope. I am not recomending this to you because you have such a basic system. I am saying that the lower you can crossover your sub the better. Which is the same for your fronts. The lower you can play them the better.
Also your crossover points don't have to be the same for sub and interiors due to the huge cabin gain. Many times the best settings are very different.
It might not have been clear, but I wanted to use passive filters on the factory speakers and active on the sub.
I will take care of the amp.
So 60 hz will be good for front/rear and sub? I will make an amp for the fronts/rears, running off 12v (just like the HU amp), and will run its signal thru a HP filter. Without the bass content, it should play cleaner and louder without distorting/clipping.
My sub will be in a really small box, and I will use a Linkwitz transform circuit. Once I get the box built, I will measure the in-car response of the sub, and then I will design the LT to flatten it out. I might add some EQ if it will be necessary. The way I see it is that using the same crossover frequency for interiors and sub should work. The LT should be able to flatten out the FR. Am I right, or is there something wrong with my thinking?
I suggest that you design your amps with adjustable crossovers so you can find the right combo for your car. Let me know once your amps are built and I can give you more help. If you are building an amp May I suggest you don't bother amping your rears and put more power to your front speakers.
If you use the same x-over point for sub and interiors you'll have major overlap at that point and on either side for at least 1 or 2 octaves. Because of the slope, in order to get closer to a flat response you'll want the points 1 octave apart for 1st order filters, 1/2 octave apart for second order, etc...I think. It's late and my math is fuzzy. But if you use a 6db/oct filter, when the points are one octave apart, they will cross each other at a point where they are each down 3db, and the overlap should bring it back up 3db. It won't be exact but it's definitely a good place to start.
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