passive crossover, assistance needed

I have read through the material posted, and am having a little bit of trouble understanding it (mostly due to the fact that it is 1:20 AM).

The vehicle is a 1991 Eagle Talon, which has 3.5" or 4" speakers in the top of the dash, 6.5" speakers in the doors, and 6.5" speakers in the rear panels.

I am planning to use all Memphis speakers: MC4 in the dash, MC620 in the doors, and MC620 in the rear panels. I will also be using a MC104 in a sealed fiberglass enclosure in the cargo area. The sources of power will be an Alpine CDA-9847 head unit for the speakers, and an Alpine MRP-M500 for the sub.

The cones on the speakers are made of woven carbon fiber, and the tweeters are aluminum.

Output on the CDA-9847 is rated at 18 watts RMS (4-ohm), and the M500 is rated at 250 watts RMS (4-ohm).

The MC4 is rated at 25 watts RMS, the MC620 is rated at 50 watts RMS.

I am planning to use the dash (woofer and tweeter) and door speakers (woofer only) to make a 3-way system. Also planning to eliminate the tweeters on the rear speakers.

The dash speakers mount facing upward to the windshield, the door speakers are low and to the front, and the rear speakers are mid-height between them and facing at a slight angle towards the front.

The 6.5" will have a 150Hz (1st) HP. The sub will cover frequencies below that.

I was thinking of putting a 5kHz (2nd)HP on the tweeters, 4.5kHz (2nd) LP on the 4". Not sure of the X point for the 6.5/4 though.

Looking for advice on crossover frequencies at all points. Also looking for some advice on how to actually construct the crossovers.

This is a fairly complex request, but I have no doubt that somebody will be able to help me.

Welcome to the forum.  The first response you will hear is that your plan is a poor one.  There are a few things, and it isn't just your planned crossover points.

OEM audio system layouts should not be duplicated in their entirety when going to an aftermarket setup.  While the dash speaker etc. layout did the trick with the proprietary OEM engineering and satisfied the majority of casual users (more speakers!), it doesn't transfer well to higher end aftermarket.  You should be building a system that far outshines the original, not duplicating it as is.

I suggest you rethink your design to much simpler measures.  Employ two amplifiers, a four channel for the fronts and rears, and a mono amp for the sub.  An alternative to that is to use a two channel amp for the fronts, head unit power for the rears, and a mono amp for the sub.  Use the passive crossovers that are bundled with your chosen replacement speakers.  Leave the dash located speakers out of the new plan altogether.

That, then, makes this a simple job.  The amplifiers' active filters will separate sound at the subwoofer crossover frequency range, and the car's front/rear speakers all provide the same full frequency range above sub level.  The quality of the results, and how your system can sound stunning compared to those of acquaintances, is in how well you achieve the design and construction of the subwoofer enclosure, the mounting and angle of front door components, the damping of sheet metal in the doors and other susceptible metal panels, the selection of quality gear and ample power, and the wiring of the power/ground (including upgrades to the OEM wiring).

I could have just advised you on how to construct the passives, but that's not going to do you any good.  You're heading off on the wrong path with your intended design.

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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

Ahh, I knew I would get a response similar to that when I posted. Didn't expect it to be the first one. LOL

I know there are far better ways to build an audio system than what I am wanting to attempt. I was not asking for a lecture about all the other variables that I know how to control. I am not looking to go the route of a 4-channel for this setup. I have been there and done that. This care is to be a budget project, the main reason I am using the Memphis stuff I already have, as opposed to using my MBQuart components. Also the reason for using the single, low power 10". The cost of the entire system is going to be in the range of $700-$800 if I were buying everything new. This is a completely different monster that the $4000 system in my other car.

I have extensive knowledge in the automotive industry as a whole. Professionally trained in electrical, body, paint, upholstery, and most aspects of 12volt. Personally taught in engine, drivetrain, and suspension.

I have not built any crossovers before. Although this may not be the best designed system in the world, it will suffice to learn more about the area in question.

I appreciate the advice on the design, and understand the weak points. This is for personal knowledge and something to help me use a bit of free time.

So, I guess my question should be reworded. So, lets try it this way...

If I were using a 1" aluminum tweeter, 4" speaker, and 6.5" speaker to construct a single channel, what would the recommended cross over points be?

There is no way to answer that question. Pretty much every 1" tweeter will require a different crossover design to properly match up to a given 4" speaker. Choose a different 4" speaker and the design changes again. Even mounting locations can have an effect on the ideal crossover design. Choosing crossover points isn't a Russian roulette process. It requires careful selection of the individual drivers to work together well and then proper testing of each speaker to design the crossover. And when you are finished you can expect the crossover to cost more than the price of the speakers.

I recommend that you read through my "Advanced front speaker systems how-to" sticky in this forum as it describes a little bit the processes mentioned above.

If all you wanted to do was experiment with building a passive crossover, why didn't you say so?

Here's a general method to approach Xover filter design: Start by choosing the tweeter Xover point by determining the tweeter fs and then at least double it for a 3rd order or higher topology, or triple it for a 2nd order or less.  Choose a mid by analyzing the FR and resonance behavior of drivers, looking for one with flat response at least an octave above the tweeter high-pass point.  Low-pass the mid using the same topology as you HP the tweeter.  Now note the sensitivity difference between the tweeter and mid and design an l-pad for the tweet to bring them within +/- 1db of each other.  Choose a woofer within +/- 1db of the mid, and if you can't then you'll have to pad the mid and increase the padding on the tweet so they all match.  To determine the HP for the mid, check it's fs and choose a Xover point above fs yet also in the linear FR range of the woofer.  Use a steep Xover (3rd order or above) to keep the woofer out of any resonance bands and depending on the diameter of the driver, out of its beaming band as well.  This will give you a starting point.   I recommend using a good modeling program to simulate your network and drivers before you begin building to save time and money, but if you don't have access to something like LEAP then you can do it old-school and just start wiring components together until you get it right.  Make sure you have plenty of coils and caps and a stack of alligator clip jumper wires and build a test network and run some sweeps and tones with your measuring mic in each speaker's near field to determine if there are other resonance bands or nasty FR peaks that you'll have to tame using notch filters.  Fine-tune the Xover component values to adjust response so the net output from all drivers is what you want at each Xover point.  Measure the impedance curve of the system sweeping from 20-20K to determine the lowest load point and make sure you have chosen Xover components that add enough impedance to keep it above whatever the lowest target load point might be.  Determine if the woofer and/or mid need a zobel by measuring out of band FR due to gross impedance changes. 

That will get you started.  There is a lot more to consider including distortion and on-axis VS off-axis output levels and what alignment to use for the enclosure if you're building home audio gear, etc.  But in a car most of these factors are generally not variable so you end up with what you get.  :)

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DYohn] wrote:

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f all you wanted to do was experiment with building a passive crossover, why didn't you say so?

Here's a general method to approach Xover filter design: Start by choosing the tweeter Xover point by determining the tweeter fs and then at least double it for a 3rd order or higher topology, or triple it for a 2nd order or less.  Choose a mid by analyzing the FR and resonance behavior of drivers, looking for one with flat response at least an octave above the tweeter high-pass point.  Low-pass the mid using the same topology as you HP the tweeter.  Now note the sensitivity difference between the tweeter and mid and design an l-pad for the tweet to bring them within +/- 1db of each other.  Choose a woofer within +/- 1db of the mid, and if you can't then you'll have to pad the mid and increase the padding on the tweet so they all match.  To determine the HP for the mid, check it's fs and choose a Xover point above fs yet also in the linear FR range of the woofer.  Use a steep Xover (3rd order or above) to keep the woofer out of any resonance bands and depending on the diameter of the driver, out of its beaming band as well.  This will give you a starting point.   I recommend using a good modeling program to simulate your network and drivers before you begin building to save time and money, but if you don't have access to something like LEAP then you can do it old-school and just start wiring components together until you get it right.  Make sure you have plenty of coils and caps and a stack of alligator clip jumper wires and build a test network and run some sweeps and tones with your measuring mic in each speaker's near field to determine if there are other resonance bands or nasty FR peaks that you'll have to tame using notch filters.  Fine-tune the Xover component values to adjust response so the net output from all drivers is what you want at each Xover point.  Measure the impedance curve of the system sweeping from 20-20K to determine the lowest load point and make sure you have chosen Xover components that add enough impedance to keep it above whatever the lowest target load point might be.  Determine if the woofer and/or mid need a zobel by measuring out of band FR due to gross impedance changes.

That will get you started.  There is a lot more to consider including distortion and on-axis VS off-axis output levels and what alignment to use for the enclosure if you're building home audio gear, etc.  But in a car most of these factors are generally not variable so you end up with what you get.  :)

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Wisenheimer...

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It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

Everything so far mentioned is correct. You are trying to do something that shouldn't be done the way you are thinking of doing it, with placement that shouldn't be even thought about...

Additionally, you are really asking questions that can't be answered with a set frequency answer. While what you WANT to end up with might, juusst MIGHT be possible, it's going to be an arduous journey at best.

I also appreciate your training and self teaching, but audio isn't any of the things you listed... I guarantee it. There is SO MUCH MORE to audio than understanding the transmission of the 2007 Volvo that you are installing in; and while these might not be the answers you are seeking, we really are trying to help you to the best possible end.

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It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

I'm sorry if I lost you when I lumped audio in with all 12volt. I do not have as much training in audio as I would like, and plan to continue to learn.

Again, I appreciate all of the responses so far. And understand this system will not sound very good done this way. But, I would much rather work something in a car than on a test bench when I can.

I know the frequency response ranges on each speaker will be a big factory in deciding crossover points. Can't seem to get anybody from Memphis to give me one of their graphs, which would really have made my life easier.

I have already noticed that the highs are very harsh, almost to the point of painful, with the speakers being on the top of the dash. When I do the final setup in the car (a while down the road, still have to do alot of other work first) I am planning to build some custom lower door panels with pods to put a nicer set of components in. I would put them in the kick panel, but space is at a premium in that area. As I said, just wanting to tinker with something and see what I can learn in the process.

Again, thank for the replies. I am off to experiment a bit.