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Discussion Starter · #1 ·
I'm using two eight inch woofers for bottom cab 31-7,000 Hz, then a 6/2in woofer 42-6,500 Hz, then the tweeter 1,400-20,000 Hz.these two will be in the box on top im planing on buying dayton crossovers.




Please HALP!
 

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Quote:
Originally Posted by alxvnd
I'm using two eight inch woofers for bottom cab 31-7,000 Hz, then a 6/2in woofer 42-6,500 Hz, then the tweeter 1,400-20,000 Hz.these two will be in the box on top im planing on buying dayton crossovers.




Please HALP!
There is no way you can get a proper alignment with a genaric crossover. Those are assuming an impedance that is whatever the crossover is rated at. I can almost guarantee that your speakers do not have that impedance at the crossover freq. You would have to look at an impedance curve to see if they do.


The general crossovers also assume a flat freq response. Most drivers are not flat. So the electrical and acoustical crossover freq are rarely equal.


Yes those will "divide" the freq-as they are intended to do-but whether or not they will give you a good sound-flat amplitude-flat phase is quite another.


Crossover design is almost not easy and has to be done for the particualr drivers used-not just random drivers.


Sorry.


But it could be a leaning experence and may be fun to play with.
 

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He's saying xover design is much much much more complicated than buying the "right" crossover from somewhere like parts express.


You could buy just about anything you want and it would have as good a chance of sounding good (or terrible) as any other off the shelf xover we might suggest.


To make even a marginal attempt to get just the basics reasonably close is going to take a lot of reading and likely a lot of trial and error.


Not to discourage you though. Designing your own speakers is a highly satisfying hobby. Just a bit of a steep (and long) learning curve.
 

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Do you want the easy way or the hard way?


The hard was is to design your own passive crossover. You'll need software and a measurement setup, and a learning curve.


The easy way is to design an active crossover. You'll still need the same tools (minus a soldering iron), but you can tweak and improve it as you learn.


You need measurement tools:
http://redspade-audio.blogspot.com/2...ent-setup.html

That's an entry level basic setup. Just fine for this.


I'd suggest a digital active crossover. Summary of choices here:
http://redspade-audio.blogspot.com/2...e-options.html


Now don't be fooled. It's not really quite so easy - more a matter of easier! The digital is very tweakable - let's be honest, first time around the real issue isn't the tools or the crossover, it's you sitting in the driver's seat.


Don't make the mistake of thinking you can buy an off the shelf passive crossover and it will work properly. A crossover is always a custom fit between box and drivers. The fact that you can buy one does not mean it's a good idea. If you aren't willing to design a crossover, but like the idea of DIY, copy a design or buy a kit.


But puh-leeeeeeaaaaasssseeeee don't buy one of those off the shelf passive crossovers.
 

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Discussion Starter · #6 ·
heres the parts i was going to use for the top seperate cabinet.Dayton XO2W-3K 2-Way Peerless 830883 Tang Band 25-302SH.For the bottom box

2 Pioneer B20GR30-51F Dayton XO3W-375/3K. do you know if this would work

well?thank you
 

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There are only so many ways you can say that something isn't a good idea.


For a start, a crossover adds an electric filter to the acoustic driver response. The two together make a summed slope and you aim for high and low pass sections to combine correctly at your chosen crossover point.


Here is an example. This is an active speaker I measured recently:



http://redspade-audio.blogspot.com/2...ve-system.html


See how the crossover occurs at 3k?


Had I chosen a stock crossover with the filters set at 3k, would it work?


The filters required to get that 3k crossover did not occur at 3k. I have a high pass at 2k and a low pass at 2.4k. This was determined with measurements. It's a custom job. It's not a refined design, just something I threw together quickly while I was learning how to use the software. But it's certainly better than buying an off the shelf crossover.
 

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Quote:
Originally Posted by alxvnd /forum/post/0


heres the parts i was going to use for the top seperate cabinet.Dayton XO2W-3K 2-Way Peerless 830883 Tang Band 25-302SH.For the bottom box

2 Pioneer B20GR30-51F Dayton XO3W-375/3K. do you know if this would work

well?thank you

Yes, that will be just perfect.
 

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Quote:
Originally Posted by alxvnd /forum/post/19638459


heres the parts i was going to use for the top seperate cabinet.Dayton XO2W-3K 2-Way Peerless 830883 Tang Band 25-302SH.For the bottom box

2 Pioneer B20GR30-51F Dayton XO3W-375/3K. do you know if this would work

well?thank you

It is impossible to know if it will work well without building the box, installing the drivers and crossover, and measuring the result (and the measurements, by the way, can be significantly influenced by the room they are taken in and how they are placed). While the parts listed might "work", they probably will not sound all that good.


It has been said above, but to try to say it another way, passive crossover design has moved far beyond simply choosing which frequency you want to transition from one drive to another, and how abrupt you want that change to be.


The crossover is used to shape the response of the individual drivers as installed in the box to make the frequency response as flat as possible across the range of frequencies the combination of drivers is designed to reproduce (see the graph in the post above); this flat response target is called is called the "transfer function".


Where passive design gets really complicated when one tries to accomplish this goal without introducing unintended side effects like:


- Time delays which cause the sound from the drivers to reach your ears at different times (group delays). Or waves of sound which overlap in odd ways causing peaks and dips in the frequency response (phase shift). Basically, these problems creep in because the electric signal takes different amounts of time to make its way through the crossover network.


- Or causing that flat response to point somewhere other that at the listener or reflected non-flat response to reach the listener (lobing)


- Or peaks and dips in the in amount of resistance (impedance, expressed by the unit Ohms, as in an 8 Ohm driver) which, if unaccounted for, can make if difficult or impossible for an amplifier to drive the speaker (this is what is meant when someone says a speaker is a difficult load for an amplifier). Basically, as the electricity move through the passive crossover components, each component changes the resistance; the driver resistance and the crossover resistance must be accounted for to present the amplifier with a reasonable load to drive.


To design a passive crossover from the ground up requires learning some theory, learning how to use some kind of crossover design program (which gets you in the ballpark, design by trial and error alone and it will take years to come up with good design), learning the technical aspects of building the crossover like how to solder, buying the parts, building the crossover, measuring the result, and repeating the process until you get something worthwhile.


As stated above, if you really want to learn how to design crossovers, active crossover design (splitting the signal electronically into a specific frequency range, then sending that signal to an individual amplifier channel which drives a single driver) is much faster because you don't have to buy new parts and build/solder a new crossover every time you want to make a change, you just change the settings on the electronic crossover. Also, you could probably learn more about crossover design more quickly using an active crossover. And if you can use the active design to help you get a closer approximation of what the passive design should be.


The simpler DIY way to passive crossovers is to let someone else do all of the heavy lifting mentioned above and build a proven design (box design, driver choices, crossover network). You will learn some basics, you should get a worthwhile result, and you can decide if you want to delve into the other complexities further.
 

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Quote:
Originally Posted by alxvnd /forum/post/19638760


--


Are you being sarcastic?

Probably. It's one way of saying that if you had the skills required to design a speaker you wouldn't be asking these questions. IMO you should look at the projects on the PE site and build one of those.
 

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Discussion Starter · #12 ·
maybe i'll just stick with my jamo c405.Even though they just sound decent to

me I compared them to my friend polk ls70 and the polk sounded smoother and cleaner

comparing the two tweeters.There is a pair at the pawn shop problem is the woofers are blown

and they want 250 for them.So I would have to order the drivers from polk audio I suppose.
 

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I say buy and findout what they sound like.


Everyone has their own requirements. The OP does not know the reference point of all others posting here.


I will try to explain that reference point by saying that almost all DIYers here believe that if you do not have accurate measurements, exact XOs then you speaker will sound like crap and its not worth it at all. Every driver, every design has its own specs/measurements and each XO is built 100% for those specs/measurements. They never would accept off the shelf XOs but then again its not their money either, There are those who have enjoy off the shelf XOs. Is it perfect?? NOPE!! But then again no one lives in a perfect world do they?



Of course there is nothing better then learning on your own. Everyone needs starting reference point and that reference will never be found through opinion posted online.
 

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Quote:
Originally Posted by alxvnd /forum/post/19639379


maybe i'll just stick with my jamo c405.even though they just sound decent to

me i compared them to my friend polk ls70 and the polk sounded smoother and cleaner

comparing the two tweeters.there is a pair at the pawn shop problem is the woofers are blown

and they want 250 for them.so i would have to order the drivers from polk audio i suppose.
Quote:
Originally Posted by penngray /forum/post/19639462


i say buy and findout what they sound like.


Everyone has their own requirements. The op does not know the reference point of all others posting here.

A little more obvious now


Quote:
Originally Posted by penngray /forum/post/19639462


i will try to explain that reference point by saying that almost all diyers here believe that if you do not have accurate measurements, exact xos then you speaker will sound like crap and its not worth it at all. Every driver, every design has its own specs/measurements and each xo is built 100% for those specs/measurements. They never would accept off the shelf xos but then again its not their money either, there are those who have enjoy off the shelf xos. Is it perfect?? Nope!! But then again no one lives in a perfect world do they?


Of course there is nothing better then learning on your own. Everyone needs starting reference point and that reference will never be found through opinion posted online.

+1
 

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I should post, I would never do it!!



but then again, I have so many DSP choices that I never will buy and XO period. IMO the OP should spend $170 on the MiniDSP and learn how to buid an active XO
 

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A simpler project would be to buy the Polks cheap, find some woofers that fit and work well enough in the box and bi-amp them with MiniDSP. You would then be crossing over in a less critical region and you could make some kind of attempt by ear, or better yet do some measuring.


penngray, I see what you are saying, but as you know it's likely to get a poor result. The idea of diy for many is to get something that works for less than what you'd otherwise pay. But if you are thinking of doing a fubar DIY speaker, you might as well just buy second hand.
 

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I just think "poor results" is a big moving target for most poeople and unless there is a good reference point they seldom will know the real differences.


There is a good and simple reason most BOSE owners still like the sound of their BOSE speakers



I understand the correct way to help the OP is to explain all the pitfalls of buying a premade XO board what I do not understand is how we can simply conclude it will always sound horrible (For someone else) going with that method? Audio has a HUGE grey area where subjective conclusions vary wildly.
 

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Quote:
Originally Posted by penngray /forum/post/19640821


I understand the correct way to help the OP is to explain all the pitfalls of buying a premade XO board what I do not understand is how we can simply conclude it will always sound horrible (For someone else) going with that method? Audio has a HUGE grey area where subjective conclusions vary wildly.

I agree with you and the strict objectivist sometimes seem to forget that the point is enjoying the sound.


IIRC, there is actually data to suggest that the differences in subjective evaluation of speakers can be based on objective differences in our physiology, like the shape of our outer ears, as well as less easily measured differences like the first learned language we learned or even the kind of music we tend to listen to.


I actually think there is a chance the generic crossover might sound OK or even good, especially in the context of what the OP has heard before. I think the more ordered and thoughtful approach that the majority here seem to subscribe to is more likely to yield better results, albeit with much greater effort and expense (and for many of us the learning and experimentation is where the fun is, which is why the effort and expense makes sense).
 

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Just as long as he understands the isssues involved. There are 2 main ones. Firstly, the filters probably won't be where they are needed. So each driver may either overlap or have a gap in the middle. Either way it means they probably won't integrate together, so you get a bump or a dip where they cross. It could be small and not too obvious, or it could be really obvious. It depends how far it is from the ideal.


The second issue is that there are other things a crossover does that will be left out. One of them is bafflestep. It's not a problem here if the speaker gets placed against a wall, where it will never sound it's best, but if you move it out for better midrange and sound stage, there's a good chance it will start to sound thin in the midbass and mid.


It's a bit of a gamble because it's an unknown how big these issues will be and how far off target the result is.


If he were to try the bi-amping, he could probably do it well enough for a start with some reasonable guesses and not even have to measure. The more critical tweeter mid xo is already done.
 

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Paul, definitely good advice.


Of course Im still thinking the best way to learn is too buy and find out the truth



Anyways, I know you joined in 2004 but I just want to say thanks for your recent contributions!! I hope you stick around.
 
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