New FAQ - How to design without measurement gear

[Ryan_M]

Re: New FAQ - How to design without measurement gear

I don't know how I missed this thread for so long but it was a nice find! Thanks again Paul (et al) for taking the time to share your knowledge!

I've done this type of stuff before but for whatever reason wasn't nearly as slick as your tutorial. Maybe a different program here or there or possible just because these are newer versions. I followed the instructions and before I knew it I was loading up the crossover design simulator... I kept having this nagging feeling like "that's it?". Of course following someones lead vs. doing completely on my own is a whole other animal, but it's still a testament to your authoring skills!

I have a couple questions though:

1.)when splicing in the modeled box response below 200Hz, do you adjust the SPL scale so it matches up the best with the existing curve? I assumed it should and that's what I did but I want to double check.

2.) From what I understand modeling the baffle step gives you the FULL baffle loss as if the speaker was way up in the air somewhere giving the theoretical 6db loss. If one wanted to only add say 4db of baffle loss then would I - after that is modeled - apply an "inverse" 2db in that section? again that's what I did because it looked right but I'm not sure.

I'm going to start a thread of my results because it went so well (using your method and then slightly modifying an existing design) that i'm actually a little suspicious that I did everything right.

Thanks again!

[Wolf]

Re: New FAQ - How to design without measurement gear

Sounds like you have the hang of it!
Keep it up!
Wolf

[shawn_a]

Re: Warning Possibly Heretical Controversy

Not heresy from my chair only because I agree with you. I evolved from being a modeling junky to using my instinct and ears with a smattering of measurements. Once a person has a goodly amount of projects under their belt and starts to understand different XO topologies and what happens when you do action X to piece Y in a filter I think that person really should be using their ears more and more. As I've said before, they will not lead you wrong as long as you are honest with yourself and know how an instrument or a person's voice should really sound. Listen for the details, the grit and minutiae in a recording. There's a wealth of info in the little spurious sounds too after all.

Case in point; I have one particularly clean recording where you can hear a music stand squeaking right of center of the orchestra as if someone had turned it to the side and then back to face them. That's a noise I know pretty well after spending most of my school life in music classes of one kind or another. I've listened to that particular part of the track more times than I care to admit because for me it is a reference bit of crud that I happened to know what sounded like in the flesh, or metal in this case.

I'm not dissing modeling at all because it's too valuable of a tool to use whether you're just getting started in the hobby or you are a seasoned veteran, so to speak. I still fire up the PCD when I get jammed by a design but I would rather spend my time listening to and adjusting a new project. For me that is where the fun really exists. I'll measure FR and Z as I go along but I don't let that data be my one and only rudder.

And I've ran headlong into what you said about the room doing some really interesting things to live instruments or voices. The stairwell at my mom's place is a super cool place to sing. Go figure it's right under the shower, another wonderful place to belt out some neat vocals. At some point I'm going to sit down on the bottom step and record some tracks.

shawn

[Jeff B.]

Re: New FAQ - How to design without measurement gear

I don't know how I missed this thread for so long but it was a nice find! Thanks again Paul (et al) for taking the time to share your knowledge!

I've done this type of stuff before but for whatever reason wasn't nearly as slick as your tutorial. Maybe a different program here or there or possible just because these are newer versions. I followed the instructions and before I knew it I was loading up the crossover design simulator... I kept having this nagging feeling like "that's it?". Of course following someones lead vs. doing completely on my own is a whole other animal, but it's still a testament to your authoring skills!

I have a couple questions though:

1.)when splicing in the modeled box response below 200Hz, do you adjust the SPL scale so it matches up the best with the existing curve? I assumed it should and that's what I did but I want to double check.

2.) From what I understand modeling the baffle step gives you the FULL baffle loss as if the speaker was way up in the air somewhere giving the theoretical 6db loss. If one wanted to only add say 4db of baffle loss then would I - after that is modeled - apply an "inverse" 2db in that section? again that's what I did because it looked right but I'm not sure.

I'm going to start a thread of my results because it went so well (using your method and then slightly modifying an existing design) that i'm actually a little suspicious that I did everything right.

Thanks again!

Correct on both counts. (I find most small speaker experience the full step though, but what you described is the way to add some back into the simulation if you want to).

[maynardg]

Re: Warning Possibly Heretical Controversy

I still fire up the PCD when I get jammed by a design but I would rather spend my time listening to and adjusting a new project. For me that is where the fun really exists. I'll measure FR and Z as I go along but I don't let that data be my one and only rudder.

Ditto. In the final voicing stage (to which the most overall time is devoted, by far), I've been misled by trying to get too perfectionist and overworking XO's (earlier, LSPCad, more recently PCD). It may be that I find it easier to spend time in front of the computer. Easier, but but not better in the later stages of XO work.

The "art" part of the process is a discipline as well - to be informed, but not driven, by the model.

[WayneN]

Re: New FAQ - How to design without measurement gear

Excellent thread Paul!

It’s nice to see steps in layman’s terms, its people like yourself, Jeff B, Wolf, dlr, and the many other seasoned veterans taking the time to share the knowledge you’ve gained over the years.

Ten years ago and a couple of back surgeries later I changed jobs from Head Custodian to IT, I was asked to write three tutorials on how to use the 3 different Energy Management Systems in one School, Barber Coleman, Honeywell and Johnson Controls, I know firsthand how much time is involved in taking information and converting it into layman’s terms, I cant thank you gentlemen enough for doing this!

It might be just me? But I find after sitting in front of a computer for 6-8 hours a day I prefer to read my information or articles in paper form, it would be great if you gentlemen could have your information available in a PDF this way we could download it, print it and keep it in a binder for reference.

Jeff, I do have your 35 page guide printed and in my binder with a tab under your name, just need to get all the renovations done then I can sit down and do some serious reading

Thanks again gentlemen for all your efforts and knowledge sharing!

WayneN

[Ryan_M]

Re: New FAQ - How to design without measurement gear

Sounds like you have the hang of it!
Keep it up!
Wolf

Correct on both counts. (I find most small speaker experience the full step though, but what you described is the way to add some back into the simulation if you want to).

Excellent.

I've come up with a few more questions...

1.) Would the cavity of the adjacent driver (as well as it's surround) cause a diffraction ripple for the tweeter? If so, is this taken into account in the modeling? Or can it be?

2.) What about driver spacing? I've read the XO frequency should be less then one wavelength. Is this something that is automatically included in the modeling or something I just need to be aware of.

3.) How do you model an MTM? Again I've read the mid spacing should be less than the wavelength at the XO frequency. Are there any other pitfalls or does it go similar to an MT?

4.) I notice a lot of boxes are designed to be just wide enough to give clarance for the largest driver. Is there a reason other than just cosmetics that the baffle should be kept narrow? I've played with the diffraction sim and I can see differences widening the baffle by an inch or so but I don't know what to consider better or worse.

5.) Is there a standard convention used for speaker orientation when modeling? i.e. straight on at tweeter level. AFAIK the rule of thumb is to set up an equilateral triangle between the speakers and listener for a standard setup, and most people like the speakers to be facing straight ahead - for cosmetic reasons. If the speaker height was setup the the tweeter was at ear height then that would put the woofer slightly below a few degrees vertically and both tweet and woofer would be off horizontally. Should I be including this in the modeling? Do others? Am I getting too nit-picky?

[dlr]

Re: New FAQ - How to design without measurement gear

Would the cavity of the adjacent driver (as well as it's surround) cause a diffraction ripple for the tweeter? If so, is this taken into account in the modeling? Or can it be?

This can at times be more influential than the baffle edge. In between tweeter and adjacent driver is the first place I look to add felt. Hard coned drivers tend to diffract more, possibly due to there being little cone damping and/or the cone depth is greater. Modeling seldom shows this as it's so varied. Measurements are needed, but it's unlikely to be useful to try to fix it in the crossover as it's very sensitive to axis. Use of felt fixes the issue for pretty much all axes.

I'm also not aware of any studies that indicate whether or not there's any real audibility. Where it may be more likely to come into play might be trying to use the crossover to fix it that only does so on some particular axis.

dlr

[E Biddy]

Re: New FAQ - How to design without measurement gear

I'm following the guide and I get to the "auto extract phase" part and I press the button and nothing happens. I'm pretty sure that I didn't miss a step and all of the other steps worked perfectly.

Any help is appreciated.

Eric