My RS180 MTM Design

[PWR RYD]

Re: My RS180 MTM Design

I understand it's complex, but at the same time these values are based off linkowitz Riley work and those were pretty smart guys also. Also the. Ross over was still stated as 1700 hz. But still, I talking strictly cossover point and these values correspond to a point around 900 hz. So, I would just like to have someone hopefully jeff explain it so I can understand......or maybe he is low passing at 900 hz?

I think it is only proper for further discussions regarding your project be discussed in the thread you started about it.

[Jesse055]

Re: My RS180 MTM Design

I think it's related to this design and my question concerns Jeff's work and his stated crossover. All along this discussion the Rs 180 -4 and rs28 have been at issue. So I disagree with your intrusion. But thinks for helping.

[Jesse055]

Re: My RS180 MTM Design

I respectfully asked clarification and help, your response wasn't really helpful in explaining the why behind the values. Hopefully jeff can help and no this belongs here not there. Just a question on how he came up and e theory behind it. Don't know why that bothers you? Im by no means putting his design down as he is the guru just asking for the why.

[Silver1omo]

Re: My RS180 MTM Design

I respectfully asked clarification and help, your response wasn't really helpful in explaining the why behind the values. Hopefully jeff can help and no this belongs here not there. Just a question on how he came up and e theory behind it. Don't know why that bothers you? Im by no means putting his design down as he is the guru just asking for the why.

I would recommend you to get a XO simulator like PCD or winPCD and see for yourself. Pretty much the lowpass also suppresses the breakup of the woofers. If you use a textbook XO like you mention (.75mH and 11uF) you will get the cone breakup at audible levels:

Now, if you go with a better XO:

The breakup is at a level that should not be audible.

[Jesse055]

Re: My RS180 MTM Design

I would recommend you to get a XO simulator like PCD or winPCD and see for yourself. Pretty much the lowpass also suppresses the breakup of the woofers. If you use a textbook XO like you mention (.75mH and 11uF) you will get the cone breakup at audible levels:
[ATTACH=CONFIG]47685[/ATTACH]
Now, if you go with a better XO:
[ATTACH=CONFIG]47686[/ATTACH]
The breakup is at a level that should not be audible.

Thanks I kinda get what you are saying, but I guess my basic question is what is the LR2 formulas that these programs and online calculators are programmed by. And I don't mean I want to do the math with a calculator or by doing calculus. What my basic question is is what is the slope and frequency point at 1700 hz? Is it the .75 and 11uf or is it 1.2 and 20 Uf.

I appreciate your 2 graphs but the second graph minimizes the break up because the low pass is just kicking in at a lower frequency. Just wanting to know if his low pass was centered at 1700 hz . Both crossovers can't be LR 2 at 1700 hz. One is and one isn't, hopefully jeff can shed some light on is and teach me something. I know him and Murphy and a couple others are well respected crossover designers whereas most of us have to copy designs or rely on programs and calculators we don't understand. Just trying to settle this in my mind as I may try this crossover. That's the fun is trying it. But I'd still like to learn e why in the process maybe I won't ever waste all that time again with the calculators.

[isaeagle4031]

Re: My RS180 MTM Design

Actually yes both can be lr2, if we are only looking at electrical. But what we are really looking at is the acoustic roll off and not just the electrical. Jeff's crossover is probably closer to an lr4 acoustic. He has also accounted for baffle step in the crossover (if applicable).
Fwiw, don't get too hung up on lr2 this or bw3 that. Its more important on how the drivers integrate at the crossover point than their respective slopes.

[Jesse055]

Re: My RS180 MTM Design

Actually yes both can be lr2, if we are only looking at electrical. But what we are really looking at is the acoustic roll off and not just the electrical. Jeff's crossover is probably closer to an lr4 acoustic. He has also accounted for baffle step in the crossover (if applicable).
Fwiw, don't get too hung up on lr2 this or bw3 that. Its more important on how the drivers integrate at the crossover point than their respective slopes.

We'll I will be making a new crossover or two and test me with the old trial and error. Hope my ears can see the difference. If not then ignorant ears are bliss.

[Silver1omo]

Re: My RS180 MTM Design

We'll I will be making a new crossover or two and test me with the old trial and error. Hope my ears can see the difference. If not then ignorant ears are bliss.

http://goldenears.philips.com/

[djg]

Re: My RS180 MTM Design

Well, one person's hobby is another person's waste of time and money.

Or, be assimilated. Resistance is futile.

http://audio.claub.net/software/jbabgy/jbagby.html

[Jeff B.]

Re: My RS180 MTM Design

Thanks I kinda get what you are saying, but I guess my basic question is what is the LR2 formulas that these programs and online calculators are programmed by. And I don't mean I want to do the math with a calculator or by doing calculus. What my basic question is is what is the slope and frequency point at 1700 hz? Is it the .75 and 11uf or is it 1.2 and 20 Uf.

I appreciate your 2 graphs but the second graph minimizes the break up because the low pass is just kicking in at a lower frequency. Just wanting to know if his low pass was centered at 1700 hz . Both crossovers can't be LR 2 at 1700 hz. One is and one isn't, hopefully jeff can shed some light on is and teach me something. I know him and Murphy and a couple others are well respected crossover designers whereas most of us have to copy designs or rely on programs and calculators we don't understand. Just trying to settle this in my mind as I may try this crossover. That's the fun is trying it. But I'd still like to learn e why in the process maybe I won't ever waste all that time again with the calculators.

I think the other answers you got summed it up fairly well if you put them together. Calculators and textbook formulas are for theory, not for crossover design; they assume a perfectly flat infinite frequency response and resistance. Real drivers are bandpass devices (meaning they roll-off on both ends) with large deviations in frequency response and very reactive impedance loads. To make a crossover for these you need to optimize the circuit to work with the driver's real impedance and frequency response so that they combine to match your target response. This is where we would use terms like LR2, LR4, B3, etc, - in defining our target. In most cases, achieving an LR4 crossover will typically use second order circuits to combine with the driver roll-offs so that the result is LR4. It is impossible to do this without measurements and computer simulations. These are called optimized crossovers. My values were arrived at by optimizing my electrical circuit, using the driver's measured response on the baffle, and complex impedance, until it matched my target LR4 acoustic crossover at 1700 Hz (I also have to take phase shifts due to offset into consideration too). This is the way the design process works. You are welcome to download my Passive Crossover Designer spreadsheet and fiddle with it yourself if you want. It does require MS Excel to work though.

Jeff

[Jesse055]

Re: My RS180 MTM Design

I think the other answers you got summed it up fairly well if you put them together. Calculators and textbook formulas are for theory, not for crossover design; they assume a perfectly flat infinite frequency response and resistance. Real drivers are bandpass devices (meaning they roll-off on both ends) with large deviations in frequency response and very reactive impedance loads. To make a crossover for these you need to optimize the circuit to work with the driver's real impedance and frequency response so that they combine to match your target response. This is where we would use terms like LR2, LR4, B3, etc, - in defining our target. In most cases, achieving an LR4 crossover will typically use second order circuits to combine with the driver roll-offs so that the result is LR4. It is impossible to do this without measurements and computer simulations. These are called optimized crossovers. My values were arrived at by optimizing my electrical circuit, using the driver's measured response on the baffle, and complex impedance, until it matched my target LR4 acoustic crossover at 1700 Hz (I also have to take phase shifts due to offset into consideration too). This is the way the design process works. You are welcome to download my Passive Crossover Designer spreadsheet and fiddle with it yourself if you want. It does require MS Excel to work though.

Jeff

I need to get ms excel. Does the version of ms excel matter

[Jeff B.]

Re: My RS180 MTM Design

I need to get ms excel. Does the version of ms excel matter

It does. The program doesn't run in Excel 2013 or in Excel 2010 if it's a 64 bit application. It runs fine in 2010 32 bit and all earlier versions down to '97.

Jeff

[Jesse055]

Re: My RS180 MTM Design

It does. The program doesn't run in Excel 2013 or in Excel 2010 if it's a 64 bit application. It runs fine in 2010 32 bit and all earlier versions down to '97.

Jeff

Got the parts in and am ready to do this with the rs28f and one 180-4. I need 3 db of padding on the tweeter. This rest of the values on e original circuit will stay the same? Is at correct.

[Jesse055]

Re: My RS180 MTM Design

Since I'm using the one RS 180-4 instead of the 2 parallel rs180-8 I will need to pad the tweeters down 3 db. What resistor values will I need to hit the 3 db?

[kraigo]

Re: My RS180 MTM Design

OK, I am building a pair of these and since it might be helpful to future readers, here's what I have for the crossover parts

20uF - http://www.parts-express.com/dayton-...citor--027-252
10uF - http://www.parts-express.com/dayton-...citor--027-244
50uF - http://www.parts-express.com/50uf-10...citor--027-354
***Note that going with an NPE cuts about $30 (37.5%) off the total cost of the crossover and that Jeff said he used an NPE in the initial post

1.2mH - http://www.parts-express.com/jantzen...-coil--255-254
0.025mH - http://www.parts-express.com/jantzen...-coil--255-198
0.25mH - http://www.parts-express.com/jantzen...-coil--255-214

Since I'm using an RS28F-4, Mike Price is talking about a Zobel to tame the high end in this thread:

http://techtalk.parts-express.com/showthread.php?225603-RS180-MTM-Build-in-Oak-Pics/page2&p=1749425#post1749425

It adds $4.34 to the cost of the crossover:
2.5uF - http://www.parts-express.com/dayton-...citor--027-218
1 ohm - http://www.parts-express.com/dayton-...esistor--004-1

Please correct me if I've made any stupid mistakes. I haven't bought these yet.

Thanks in advance.

KO