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My RS180 MTM Design

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  • Jeff B.
    replied
    Re: My RS180 MTM Design

    Originally posted by Jesse055 View Post
    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

    Leave a comment:


  • Jesse055
    replied
    Re: My RS180 MTM Design

    Originally posted by Jeff B. View Post
    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

    Leave a comment:


  • Jeff B.
    replied
    Re: My RS180 MTM Design

    Originally posted by Jesse055 View Post
    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

    Leave a comment:


  • djg
    replied
    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

    Leave a comment:


  • Silver1omo
    replied
    Re: My RS180 MTM Design

    Originally posted by Jesse055 View Post
    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/

    Leave a comment:


  • Jesse055
    replied
    Re: My RS180 MTM Design

    Originally posted by isaeagle4031 View Post
    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.

    Leave a comment:


  • isaeagle4031
    replied
    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.

    Leave a comment:


  • Jesse055
    replied
    Re: My RS180 MTM Design

    Originally posted by Silver1omo View Post
    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.

    Leave a comment:


  • Silver1omo
    replied
    Re: My RS180 MTM Design

    Originally posted by Jesse055 View Post
    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:
    Click image for larger version

Name:	textbook.PNG
Views:	1
Size:	14.2 KB
ID:	1158544
    Now, if you go with a better XO:
    Click image for larger version

Name:	better.PNG
Views:	1
Size:	13.7 KB
ID:	1158545
    The breakup is at a level that should not be audible.

    Leave a comment:


  • Jesse055
    replied
    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.

    Leave a comment:


  • Jesse055
    replied
    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.

    Leave a comment:


  • PWR RYD
    replied
    Re: My RS180 MTM Design

    Originally posted by Jesse055 View Post
    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.

    Leave a comment:


  • Jesse055
    replied
    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?

    Leave a comment:


  • isaeagle4031
    replied
    Re: My RS180 MTM Design

    Fairly simple, yet complex at the same time. The online calculators assume that the woofer and tweeter are static loads. However, impedance varies with frequency. Jeff uses an excel spreadsheet that he developed (and many of us use for that matter.)

    Leave a comment:


  • Ryan_M
    replied
    Re: My RS180 MTM Design

    There is lots the online calculators don't account for...

    - Baffle step compensation
    - response of the drivers
    - dynamic impedance of the drivers
    - baffle diffraction effects
    - difference in sensitivies between the drivers
    - tonality of the speaker
    - time alignment and phase
    - presentation of the speaker
    - off axis response and power response
    - plus a few I'm probably forgetting

    The crossover is where the magic is. This is what makes greats like Jeff, well great. The online calculators will give you typically nothing that will function well besides to protect the drivers.

    Leave a comment:

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