Custom 3 way speaker

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Brad2525

Audiophyte
I am making a custom 3-way front speaker. The question is what do you suggest my crossover points should be and what type of crossover should I use.

All 3 speakers are 4 ohms.

The Tweeter is a ribbon tweeter with a RMS is 25 watts and Usable Frequency Range 1900-18kHz

The midrange woofer has a RMS of 300 watts and Usable Frequency Range 95-9.5kHz

The sub woofer has a RMS of 200 watts and Usable Frequency Range 10-400 hz

I am powering it with a 575watt @ 4ohms per channel. So I need a crossover that can handle that much watts.


What are you suggestions on the crossover, I am thinking I might need to make one.
 
S

shadyJ

Speaker of the House
Staff member
I hope you are not expecting a high fidelity speaker here. The crossover points should be determined by the linear operating bandwidth of the speaker, the woofer diameter, the cabinet size and type you are placing them in, and so on. If you are doing something just for fun, I would place the crossover points an octave into each driver's linear frequency bandwidth. You might try 200 Hz and 3 kHz. It won't be perfection, but it looks like you aren't taking your project too seriously anyway. On the other hand, if you are taking this project seriously, you can not just select the parts you are using based on a nebulous spec like "usable frequency range" and power handling. You need to do some serious homework for a good three-way speaker. On the off-chance that you are really trying to build a really good speaker, you might try reading this book first.
 
B

Brad2525

Audiophyte
I am not planning on going cheap if that is what you mean. But there are some limits, like cavity of the speaker is limited to about 6" deep, 15" wide and anywhere from 40 to 60" tall. These dimensions are because i want it mounted into the wall. So the woofer is 8" and is the CDT-800CF. I was going to do a sealed enclosure because from what i understand the woofer hits 0 db around 200hz if it is not ported. I am not sure what to do about the midrange which is a DS18 PRO-NEO8 8" which i hooked up in a temp system and sound good but I am thinking it is not as high quality as i wanted so i might switch them out. The tweet is the Dayton Audio AMT3-4 Air Motion Transformer Tweeter 4 Ohm, i know it is not the best tweeter and the AMTPro-4 is better but money is not unlimited. So right now i have already into it $600 dollars for the speakers and 300 for the amp. I still need to build the crossover and speaker box.

So I would like as high fidelity as possible on my budget.

Does this help? Do you have suggestions for a better Midrange woofer?
 
TLS Guy

TLS Guy

Audioholic Jedi
I am not planning on going cheap if that is what you mean. But there are some limits, like cavity of the speaker is limited to about 6" deep, 15" wide and anywhere from 40 to 60" tall. These dimensions are because i want it mounted into the wall. So the woofer is 8" and is the CDT-800CF. I was going to do a sealed enclosure because from what i understand the woofer hits 0 db around 200hz if it is not ported. I am not sure what to do about the midrange which is a DS18 PRO-NEO8 8" which i hooked up in a temp system and sound good but I am thinking it is not as high quality as i wanted so i might switch them out. The tweet is the Dayton Audio AMT3-4 Air Motion Transformer Tweeter 4 Ohm, i know it is not the best tweeter and the AMTPro-4 is better but money is not unlimited. So right now i have already into it $600 dollars for the speakers and 300 for the amp. I still need to build the crossover and speaker box.

So I would like as high fidelity as possible on my budget.

Does this help? Do you have suggestions for a better Midrange woofer?
Going about it the way you are, you will have a very low fidelity speaker.

You don't have the first clue how to go about it. No, not the first clue.

We continually get these posts, of I'm building a three way speaker and how to I do it and I'm tired of it.

Well we can't reply meaningfully here, as it is literally a text book, which we can't put in a post like this.

You can't just buy drivers and expect to make a speaker. You have to carefully select drivers that it is feasible to blend into a decent speaker. If you just buy speakers at random, then you will almost certainly have a combination that will not work whatever you do.

After making sensible choices, then you have to decide the optimal loading of the woofer and work out the optimal box form the Thiel/Small parameters of the woofer.

In your selection you should have chosen drivers that can be crossed far enough apart to make the band pass gain manageable. This is where three ways get really tricky and a major reason why you never choose a three way for your first project as they are a very steep climb indeed.

Crossover points and slopes are determined by the acoustic responses of the drivers and their break up points. This requires computer modelling. Before computer modelling in the early eighties this was a huge task with a lot of trial and error. Even then just about no one got a three way right unless they were very lucky.

One absolute rule is that you can never make a speaker worth listening to from an off the shelf crossover. All speakers require unique and custom crossovers designed with consummate skill and care.

You have already got way off on the wrong foot by purchasing drivers before you have a functional design. You were miles away from the design purchase point.
 
S

shadyJ

Speaker of the House
Staff member
I am not planning on going cheap if that is what you mean. But there are some limits, like cavity of the speaker is limited to about 6" deep, 15" wide and anywhere from 40 to 60" tall. These dimensions are because i want it mounted into the wall. So the woofer is 8" and is the CDT-800CF. I was going to do a sealed enclosure because from what i understand the woofer hits 0 db around 200hz if it is not ported. I am not sure what to do about the midrange which is a DS18 PRO-NEO8 8" which i hooked up in a temp system and sound good but I am thinking it is not as high quality as i wanted so i might switch them out. The tweet is the Dayton Audio AMT3-4 Air Motion Transformer Tweeter 4 Ohm, i know it is not the best tweeter and the AMTPro-4 is better but money is not unlimited. So right now i have already into it $600 dollars for the speakers and 300 for the amp. I still need to build the crossover and speaker box.

So I would like as high fidelity as possible on my budget.

Does this help? Do you have suggestions for a better Midrange woofer?
You can maybe make a fun three-way speaker as a project, but it isn't going to approach the level of quality that a professional would make. Better mid woofer doesn't matter. My advice is not to take it too seriously. I would use an active system like miniDSP or Berhinger DCX2496 to do the crossover. You will struggle getting all the levels right otherwise, because these drivers all have very different sensitivities, and who knows how their impedance loads will add up. You can't just buy a bunch of different drivers and expect greatness. There are computer programs that will generate a crossover schematic for you for different drivers, but I haven't used any of those.
 
BoredSysAdmin

BoredSysAdmin

Audioholic Slumlord
lsiberian

lsiberian

Audioholic Overlord
To design a good 3-way speaker.

I suggest
You find a strong midrange with a wide band. Everything else builds off that midrange.
You use a minidsp and do fully active speakers. It will make your life much easier.

My 3-way has a Dayton dome midrange. I love dome because it eliminates the need to build a secondary enclosure. AMTs are another good choice.

Designing and building a 3-way is not a simple task. It requires an engineering mind to pull off and it will take you more time than you are estimating.
 
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