Car crossover for home use

 

New member
Username: Cristian

Post Number: 4
Registered: Nov-06
Hallo everybody,

I was given a car crossover networks. 3 - way. I have alredy some old speaker drivers and I want to use these crossovers for this speakers and built new housing for use in home. It will be enclosure type box with bass reflex tube. My question is : Can I use these crossovers or not. Maybe they are ment for use only in cars, where are different acoustics conditions then in the house?

Thanks in advance.
 

Gold Member
Username: Nuck

Post Number: 4621
Registered: Dec-04
David, crossovers are meant for specific applications. 3-way x-o's are even more complicated than 2-ways by a 2nd order.
Buy or find something pre-designed.
 

New member
Username: Cristian

Post Number: 5
Registered: Nov-06
Hallo Nuck,

Thank you for your post.Are you 100% shure that using car crossovers is not a good idea? Can you please confirm me that? I ask you to confirm this because finance factor is very important to me and I do not want to wait money unless is really needed.
Thanks again.

P.S. I would appreciate any other oppinion.
 

Gold Member
Username: Nuck

Post Number: 4624
Registered: Dec-04
David, try them and see.
 

Gold Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 9360
Registered: May-04
.

Car stereo crossovers operate the same way home units do. The problems you'll run into deal mostly with the power supply to the crossover. You'll have to find a power supply to drop your 120VAC, 15 Amp line down to the 12VDC, "?" Amps your crossover expects. This will place the crossover on a different ground plane than the amplifier which could result in a loud hum caused by a ground loop. This could prove impossible to solve. Or not. Try it and see if you want to spend the money on a project that might not work well.


The next problem is building a good sounding speaker is more than just gathering some parts and putting them in a box. How much experience do you have at building speakers? For the price of the drivers and enclosure plus the power supply for the crossover, assuming no problems arise with the grounding, you could buy some decent home speakers and save yourself a lot of headaches.


.
 

New member
Username: Cristian

Post Number: 6
Registered: Nov-06
As far as I know, there are 2 types of crossovers : 1. active 2. passive

My crossovers are passive and they do not need separate power supply, so there will be no problem. Am I right?
Other than that You think there will be no other problem regarding crossovers?
It is Visaton (Germany) manufacturer, well known for their speaker drivers. I have some experience with building enclosure, so I think there will be no problem regarding that.
Only thing that worries me is about crossovers.
Can I use them or not? (note: I know that the best thing is to try and see and then change them if something is not all right, but I do not have that possibility (do not ask why - it is a long story), so my final product will be based on your advice? That is why I ask this question and need answer from someone who is 100% sure? You said "Car stereo crossovers operate the same way home units do" so I concluded (if there is everything ok with power-that I think I do not need) everything will work just fine. Is this correct?
 

Gold Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 9362
Registered: May-04
.

No. You must have missed the sentence about speakers being more than a collection of drivers. If you have a passive X-over, you have more or less defined parameters that determine the slopes and filter action of the X-over components. In other words, the frequencies where the drivers are crossing one-to-another are already determined as is the amount of roll off and roll in for the high pass and low pass leg of each section in the X-over. I'm going to guess you don't know where the X-over frequencies are set for this freebie you own nor do you know the order of the filters, first order, second, third, fourth, cascaded seconds, etc. I will also assume you don't know whether the X-over has any correction circuits or baffle step network or whether any mechanical roll off of the drivers is accounted for in the X-over. All you know is you have a crossover. Correct? Series or parallel circuits? You don't know. You don't really know whether you have an active or a passive unit. Right? So you have what is essentially a totally unknown crossover with parameters you don't know and you want to build a three way speaker around this unknown. Do I understand that correctly?


Now I'm going to assume you are fairly young. I don't mean to squash your enthusiasm but trying to build a good sounding speaker from an unknown crossover isn't how I suggest you begin learning about building speakers. Car stereo drivers don't work very well inside your home. That is, from what you say, where this X-over was intended to work, in a car stereo. So let's assume you can't use the drivers this X-over was meant to mate with. Until you know the crossover frequencies and the slopes of the filters, at least, you cannot proceed with a well thought out plan. If a well thought out plan wasn't in your "plan" then you can stop reading here and go about putting some drivers in a box and using this X-over. You might like what you get and you might not. If dollars are important that's a chance I wouldn't want to take, 50-50 you'll like it or it will be crap.


Let's now assume you get lucky and the person who "gave" you this X-over can tell you the information you need to get started. You now have to find drivers that will work with those numbers. As a beginner speaker "designer" that's not how you want to go about this project. Normally you start with the drivers and then determine what X-over will work best with that selection. By putting the X-over first, you haven't got much of a chance of building something that really sounds good. Now, if good sound wasn't in your plans and you just wanted to build a speaker because you have a X-over, you can stop reading here.


Speaker design is, as I said, more than just gathering the parts and sticking them in a box. Let's say you know the first crossover frequency from low to mid, you now have to find a driver that suits that frequency range and determine whether that driver will suit the box you want to build. Will it have the frequency extension you want for the size of box you want? Will it have the correct "Q"? Will it roll off at the correct rate to mate with the midrange? Is it the right impedance for your amplifier? These are just a few of the decisions you will have to make just for the low frequency driver. More decisions must be made for the other two drivers. Then what if the whole system gets put together and you need to "change them"? You say you can't. And you might as well just figure that you are going to have to adjust something with the way this system is being built. Even if you could, do you know how?


I would say that makes these X-overs pretty worthless to you unless you want to live with lousy sound that you paid a fair amount of money for. You are starting at the wrong end of the equation and you don't have the ability to make any changes if needed. You are starting at the cheap end of what goes into a speaker and thinking about putting lots more money into a project you don't understand. That is not how you build a speaker.


On the otherhand, everyone has to start somewhere. There isn't a speaker designer I know who doesn't look back at how horrible their first dozen designs actually sounded. But they usually started these projects with more than an unknown X-over as the basis for their efforts.



If you want a speaker, buy a pre-designed kit which has all the components included and can offer some very good sound for a few dollars. You will be buying a tested product that has some guarantee of success and saving money over a commercial product. You will also have some pride in what you build and will learn more about speaker construction that your projected route will get you. Otherwise you can easily end up with a piece of junk that you have no use for and neither will anyone else. Put these X-overs aside and spend your money wisely instead of building a house just because someone gave you a brick.


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New member
Username: Cristian

Post Number: 7
Registered: Nov-06
Dear Jan,

Thank you for your time and patience for explaining me all of this.
I am sure that I have passive crossovers and I will use them with speaker drivers that originaly came with those crossovers. The speakers are expensive (relatively), and I do not have the money to buy a new speaker in that class. That is why I choose to build a enclosure. I ran to different oppinions about using car speakers in home. One of the oppionins is that the only thing that values is T/S speaker parameters, and based on the Qts factor it can be decided is building enclosure is a good idea. I assume there will be no problem with midrange driver and tweeter. The real issue will be bass driver. I entered the T/S parameter in program Winisd and SpeakerWorkshop, and calculated that right volume of enclosure will be around 40L. I heard that if Qts value is less that 0.7, than speaker is meant for enclosure, and if Qts value is between 0.7 - 0.9 than speaker is meant for infinite volumes (luggage trunk of car). The Qts value of my speaker is 0.39 and I concluded that there will be no problem.
Is this right or I have received wrong information from someone who was not sure about this issue.
Based on your last post, I belive that You have the right knowledge to answer me correctly.

Looking forward for your answer.
 

Gold Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 9364
Registered: May-04
.


Well, we've covered quite a bit of ground in a short time from not being sure whether your X-overs were passive or active to putting T-S values into a speaker building program.


You are going to get plenty of opinions about how to build a speaker. Mostly because so few people agree about what makes a speaker sound good in the first place. If everyone likes something different, then it stands to reason most people won't agree on how you should build a speaker. That is partially why there are hundreds upon hundreds of speaker companies on the market now. Everyone can put numbers into a speaker building program and call themself a manufacturer. So, first of all, I would suggest you have some idea whether you will like the speakers you are about to pump a fair amount of money into. There's little point in building something you don't like, particularly if money is tight, and, as I said, you are starting from the wrong end of the stick when it comes to building a speaker. Someone has given you a horse and now you want to hit a home run. Having a X-over doesn't really qualify as a good reason to sink money into drivers if you are not absolutely certain you will like the results.


T-S parameters have become the heart and soul of speaker design in the last few decades since they can give a reasonably good estimate of how to build a low frequency system. They help determine the enclosure volume and box type and can, to some extent, predict the final "Q" and low frequency extension of the system (which are inter-related, change one and you affect the other). They do not, however, predict what the finished system will sound like since the T-S parameters deal only with the last octave of a speaker system's performance. Unless you are doing something unusual with the mid and high frequency drivers' enclosures, T-S parameters only get you a rough approximation of the enclosure volume and, if you use a vented enclosure, the port size, shape and length for a given low frequency extension. The bass response can still suck after doing the math and the best designers build several prototypes before deciding which will be the final design. Did you know the shape of the port's intake and output and where it is placed in the enclosure will make a discernable difference in the bass quality? These are the things you learn as you gain experience and I hope, if you proceed with this project, you gain some valuable knowledge by learning such small things that will make the speaker better. But, I'm still concerned with the idea you are unable to change the X-overs since that implies you are going to build one box and that's going to be the finished product.




Now, I'm going to assume you have heard the speaker you want to build used in a home system and not just in a car and you like what you heard from the finished product. If you haven't heard the speakers in a home situation, then you still might want to consider whether this is the system to build. Many, if not most, of the drivers designed for the small space of an automobile have characteristics which are undesirable in the home and plugging the T-S parameters into a design program won't tell you the end result or allow you to change the results. Driving the air inside a few hundred cubic feet of car interior is quite different from driving the more than one thousand cubic foot volume of a typical room. Overcoming road noise is not a problem the driver must face inside your home but might have been designed into the driver or into your X-over. Clarity is achieved by frequency manipulations in a car that will be unsuitable in your home. If you are unable to change the X-overs to make the appropriate alterations, you are still facing a perilous finish to this prject. And, consider that the drivers as they are used in your car are flush mounted to the baffle of the interior panel. This changes a number of parameters and is not how you will use the speakers in your home. Simple correction networks for many of the problems that exist in most modern home speakers are probably missing from the car stereo X-overs you have in your possession. Therefore, I would draw two conclusions. First, I am still warning you about building a speaker based upon an existing X-over from a design "foreign" to home audio. Second, there are important considerations to put into your project other than T-S parameters. If gathering T-S parameters was the only thing that determined what made a good sounding speaker, we'd all be plugging numbers into a program and pulling out our table saws and wood clamps.



I honestly think the best thing for me to do at this point is to turn you over to someone who might be better equipped to answer your questions as they arise. There are several DIY speaker supply companies out there that will give excellent advice to someone in your situation. Give Parts Express and Madisound a call. They both have a wide selection of drivers that might substitute at a lower cost and will give you good answers to building a design based upon your specific knowledge and situation. At this point I suggest you slow down on your internet searches since you will be getting conflicting messages based on the experience of lots of people - many of whom have never attempted what you what to accomplish and might have a very different idea of what they want to accomplish.


My opinion is you shouldn't attempt this project based on the fact you have X-overs; that is, excuse the term, a dumb reason to build a speaker. Yes, you may not be able to afford speakers of this quality, but I still get the feeling you don't know what the quality of the finished product will be in your home. I'll guess that's not the opinion you want and you will proceed anyway. In that case, let me just add we've not discussed what type of amplifier you have to drive these speakers and whether they will be suitable for use with that amplifier nor have we mentioned what type of sound you want to have. Just buying expensive drivers isn't a guarantee of sound you will like. The Qts of the driver you are considering makes it a fairly dry sound that, in a typical vented enclosure and in your room's cubic volume, might not suit your tastes if you listen to "young people's" music. This doesn't, at a Qts of 0.39, sound like a speaker that will "rock" when used in a home audio system. And, as I mentioned above, the Qts of the low frequency driver isn't going to determine what you finally hear from the completed system.


Place the names of the two companies I mentioned into a search engine to get phone numbers for their technical assistance staff. Give them a call with the T-S numbers of the prospective L.F. driver and the efficiencies and impedance of all the drivers. Determine whether you have a series or parallel connection in your X-overs. With that information they will give you better advice one-on-one than anyone on line can manage.



Good luck.


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New member
Username: Cristian

Post Number: 8
Registered: Nov-06
Dear Jan,

This all sounds very complicated for me. That is why I decided not to waist more time and money on something that might not work well. So, I will sell crossovers and other parts for DIY I already have, start saving some money and buy already predesigned speaker kit - probably Starlet kit from Visaton.
Thank you on your explanation and advice, you helped me a lot.

Best regards
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