Think I've figured it out. HF are my Far Field FR measurements. LF are the manufactures FR measurements?
Let me see if I can't help you out here with the process.
You are going to need another set of measurements next. Re-read Jeff's relative acoustic offset paper again if you need to and then measure the following keeping the mic and the volume knob at the exact same positions for each one (I suggest about 24" to 36" on axis with the tweeter but measure the distance exactly):
1) tweeter only
2) mid only
3) woofer only
4) tweeter and mid together
5) tweeter and woofer together
6) mid and woofer together
Then I'll need to know the mic distance you chose and the distances between the centers of the tweeter and mid, and tweeter and woofer on your baffle.
Now if you really want to do this right, you should also take a measurement of each driver's real impedance in the cabinet but that is going to require a little Limp jig (info here and here and/or google images for Limp jig) or something like the Dats system although the latter doesn't make much sense unless you want to really take all of this up as a permanent hobby.
However, we can probably work with the manufacturers' impedance measurements if we have to.
If you haven't done this already, it wouldn't hurt to re-do your initial measurements to see if you get the same results again.
Then I can work with your files and set you up in a xo program if you like.
You are going to need another set of measurements next. Re-read Jeff's relative acoustic offset paper again if you need to and then measure the following keeping the mic and the volume knob at the exact same positions for each one (I suggest about 24" to 36" on axis with the tweeter but measure the distance exactly):
1) tweeter only
2) mid only
3) woofer only
4) tweeter and mid together
5) tweeter and woofer together
6) mid and woofer together
Then I'll need to know the mic distance you chose and the distances between the centers of the tweeter and mid, and tweeter and woofer on your baffle.
Now if you really want to do this right, you should also take a measurement of each driver's real impedance in the cabinet but that is going to require a little Limp jig (info here and here and/or google images for Limp jig) or something like the Dats system although the latter doesn't make much sense unless you want to really take all of this up as a permanent hobby.
However, we can probably work with the manufacturers' impedance measurements if we have to.
If you haven't done this already, it wouldn't hurt to re-do your initial measurements to see if you get the same results again.
Then I can work with your files and set you up in a xo program if you like.
Ok great, i'll get onto this tonight. with regards to the tweeter+woofer together etc. Where should the mic be positioned? Assume half way between the two driver in question?
Well i am not going to waste of your time by what all are saying blah-blah.
As you suggest woofer for your 3-way design, its not scientific method and not difficult to find the best speakers which will be suitable for you. There are some important aspects which will help you to decide which speaker is best for you -
1. Always look at frequency response graph at its website, the more linear frequency response more better. If want to buy a Woofer then look for frequency response from 20-500 hz maximum and also for midrange with midrange frequency and tweeter for high frequency. A high-fidelity driver will have maximum 3 db fluctuation within its frequency range which it is intended to design.
2. If the speakers are going to be use for home theater then look for its off axis frequency response because not only off axis frequency response provide wide coverage of direct sound in the front but also diffuse the sound equally in all directions in the room with the help of reflection which will provide good ambient sound.
3. If manufacture didn't provide off axis frequency response in its graph then look for average calculation formula as an example- 8" woofer will provide good off axis frequency response upto 600-700 hz within 70-80 degree angle. A 70-80 degree angle is maximum to have good dispersion from the speaker.
4. Always look for high sensitivity speaker because it will provide lot of headroom for dynamics with low distortion. And also you will probably don't need higher watt amplifier if you have high sensitivity speaker used for home.
5. It is not difficult to decide for purchasing any speaker. Even if with cheap speaker drivers, one can build high quality speakers and also vice-versa. The extreme difficult works start like how you to design high quality speaker box which will provide low distortion in a full range frequency response, testing for frequency response and impedance response after speaker has build into the box, crossover design, equalizing frequency response with DSP etc. Speaker box affects a lot for speaker producing sound due to standing waves, diffraction and comb-filter. So, you have to gather lots of information before building a speaker box. There are lots of books available which will provide lots of information to be prepared for this type of project. Its time consuming, may take some months which is good because the more you gather information then the more u prepared.
6. Always look for manufacturer who has good reputation in a market. At least with that you can trust their details which they are providing in their website. Some manufacturer may manipulate details a bit to attract customers. If the budget is concern for you then don't go for expensive manufacturers, there are lots of other manufacture which produce good reputation in the market and also produce good speaker drivers with affordable price.
7. Always look for same and near sensitivity rating for woofer, midrange and tweeter. If the sensitivity of all drivers are close enough then you don't have attenuate any high sensitivity speaker in Crossover design to match with others..
8. If you don't have Subwoofer, and you don't want to use it in future also. Then go for speakers which will have deep low frequency response upto 20hz. The fact is that look for point at its spl graph for low frequency range in which it will start to attenuate -3db which is called f3.
I hope this information will be enough for clear your mind.
As you suggest woofer for your 3-way design, its not scientific method and not difficult to find the best speakers which will be suitable for you. There are some important aspects which will help you to decide which speaker is best for you -
1. Always look at frequency response graph at its website, the more linear frequency response more better. If want to buy a Woofer then look for frequency response from 20-500 hz maximum and also for midrange with midrange frequency and tweeter for high frequency. A high-fidelity driver will have maximum 3 db fluctuation within its frequency range which it is intended to design.
2. If the speakers are going to be use for home theater then look for its off axis frequency response because not only off axis frequency response provide wide coverage of direct sound in the front but also diffuse the sound equally in all directions in the room with the help of reflection which will provide good ambient sound.
3. If manufacture didn't provide off axis frequency response in its graph then look for average calculation formula as an example- 8" woofer will provide good off axis frequency response upto 600-700 hz within 70-80 degree angle. A 70-80 degree angle is maximum to have good dispersion from the speaker.
4. Always look for high sensitivity speaker because it will provide lot of headroom for dynamics with low distortion. And also you will probably don't need higher watt amplifier if you have high sensitivity speaker used for home.
5. It is not difficult to decide for purchasing any speaker. Even if with cheap speaker drivers, one can build high quality speakers and also vice-versa. The extreme difficult works start like how you to design high quality speaker box which will provide low distortion in a full range frequency response, testing for frequency response and impedance response after speaker has build into the box, crossover design, equalizing frequency response with DSP etc. Speaker box affects a lot for speaker producing sound due to standing waves, diffraction and comb-filter. So, you have to gather lots of information before building a speaker box. There are lots of books available which will provide lots of information to be prepared for this type of project. Its time consuming, may take some months which is good because the more you gather information then the more u prepared.
6. Always look for manufacturer who has good reputation in a market. At least with that you can trust their details which they are providing in their website. Some manufacturer may manipulate details a bit to attract customers. If the budget is concern for you then don't go for expensive manufacturers, there are lots of other manufacture which produce good reputation in the market and also produce good speaker drivers with affordable price.
7. Always look for same and near sensitivity rating for woofer, midrange and tweeter. If the sensitivity of all drivers are close enough then you don't have attenuate any high sensitivity speaker in Crossover design to match with others..
8. If you don't have Subwoofer, and you don't want to use it in future also. Then go for speakers which will have deep low frequency response upto 20hz. The fact is that look for point at its spl graph for low frequency range in which it will start to attenuate -3db which is called f3.
I hope this information will be enough for clear your mind.
Here's my take 2 measurements 🙂 I positioned the mic mid way between the drivers, when taking combined measurements. I've done near and far field for every driver + combo.
When measuring the tweeter, whether on its own or combined, I started at 100Hz. The other drivers start at 20Hz
Far-Field mic distance: 33”
Near-Field mic distance: ¼”
Tweeter – Mid distance: 4 ½”
Tweet – Woofer distance: 14 ½“
Hope these are correct and thank you again!
Measurements can be downloaded from here:
https://drive.google.com/file/d/0Bwwef9FGi6GibzBTUWxzY3RNdWc/view?usp=sharing
p.s. i'm happy to not use a Limp jig and go with the factory impedance results.
When measuring the tweeter, whether on its own or combined, I started at 100Hz. The other drivers start at 20Hz
Far-Field mic distance: 33”
Near-Field mic distance: ¼”
Tweeter – Mid distance: 4 ½”
Tweet – Woofer distance: 14 ½“
Hope these are correct and thank you again!
Measurements can be downloaded from here:
https://drive.google.com/file/d/0Bwwef9FGi6GibzBTUWxzY3RNdWc/view?usp=sharing
p.s. i'm happy to not use a Limp jig and go with the factory impedance results.
No, the mic position does not change nor does the power level. On axis with the tweeter, about 30ish" away for every single measurement for the relative acoustic center data. Set it up once and then don't move it. What we're doing is using the fixed mic position and the fixed driver positions and then the summing of the different driver FR's to tell us where the acoustic center of each driver is. It's simply about the geometry and the different times it takes sound to travel the different path lengths.
I understand. How about the vertical position of the mic. Where about's should that be... ear level? Use the same fixed point for all 6 measurements?
you only need far field for Mid and Tweeter. Near field for woofer only. After that adjust the db level, according to the distance. Then splice with up frequency response with woofer, Mid and Tweeter.
For more detailed information read this below -
https://www.google.co.in/url?sa=t&r...EQPmR873uE7yEw-DHdQM7w&bvm=bv.142059868,d.c2I
For more detailed information read this below -
https://www.google.co.in/url?sa=t&r...EQPmR873uE7yEw-DHdQM7w&bvm=bv.142059868,d.c2I
The height for the mic should be the same as the height of the tweeter and it should be directly in front of it, ie. at a 90* angle to the tweeter not off to the left or right. Then, yes, use that same mic position for all 6 measurements. In truth, you only need 5 of those but I like to have a 6th to double check the woofer acoustic center position.
Why would you not also want to blend the woofer near and far field measurements?
Thank you. I've now positioned the mic level with the tweeter, which in my setup is around ear level.
All measurements taken far-field at 33", with no change to dB's.
New measurements here:
https://drive.google.com/file/d/0Bwwef9FGi6GiMER1dm1SSXZVbDA/view?usp=sharing
Fingers crossed i've got this nailed, this time 🙂
All measurements taken far-field at 33", with no change to dB's.
New measurements here:
https://drive.google.com/file/d/0Bwwef9FGi6GiMER1dm1SSXZVbDA/view?usp=sharing
Fingers crossed i've got this nailed, this time 🙂
Excellent. Hopefully that should do the trick. I'll know for sure once I start working with the files.
Ok, results were just a little different than I was expecting which means it's worthwhile double checking.
Can you run those 6 measurements one more time? Change the mic distance a little, say to 27" or 30" and because I haven't mentioned it before, make sure you are using an SPL about equivalent to your normal listening levels. Everything else is the same as before.
Can you run those 6 measurements one more time? Change the mic distance a little, say to 27" or 30" and because I haven't mentioned it before, make sure you are using an SPL about equivalent to your normal listening levels. Everything else is the same as before.
I've just ran them at 27" as a SPL that approximated my listening level.
https://drive.google.com/file/d/0Bwwef9FGi6GibW5laTlaQkxOSU0/view?usp=sharing
https://drive.google.com/file/d/0Bwwef9FGi6GibW5laTlaQkxOSU0/view?usp=sharing
because the woofer with far field measurement will include room mode. That's why it is better to have near field measurement with low frequency only.
Thanks spark, I'll get back to you.
Well, what distance do you define as farfield and what gate are you using on it?
Well, what distance do you define as farfield and what gate are you using on it?
Just spotted a problem with the mid range driver. I'd covered the back of the magnet with some bitumen sheet, however it seems there is a channel through the centre of the driver (front to back). I'll remove the bitumen sheet and post new measurements in the next hour. Sorry!!!
Ok, take 6 of the measurements below.. I've also included a Near-Field of the Mid just in case that's needed. Sorry I hadn't spotted this driver design feature earlier! I think I must have gotten carried away with the dampening goal for the enclosure 🙂
https://drive.google.com/file/d/0Bwwef9FGi6GiYTlGU3FJdnRMeUE/view?usp=sharing
https://drive.google.com/file/d/0Bwwef9FGi6GiYTlGU3FJdnRMeUE/view?usp=sharing
Looks like you are getting used to taking measurements now. 😀
It wasn't a problem at all, there was no change in the mid's FR, but you will want to keep that back vent on the mid open in the future.
I can't tell you why, but the 1st set of 27" measurements was better than the 33" ones. The acoustic center calculations look more realistic this time. I'll run your 2nd 27" files through the process as well just to verify 1 more time. Then I'll start to work up a xo for you. If you want to try your hand at it yourself I can attach the program with the appropriate files too (XSim or PCD? I can't remember which you prefer).
Also, can you link to where you are getting your xo parts from so I can see what values etc you have access to.
It wasn't a problem at all, there was no change in the mid's FR, but you will want to keep that back vent on the mid open in the future.
I can't tell you why, but the 1st set of 27" measurements was better than the 33" ones. The acoustic center calculations look more realistic this time. I'll run your 2nd 27" files through the process as well just to verify 1 more time. Then I'll start to work up a xo for you. If you want to try your hand at it yourself I can attach the program with the appropriate files too (XSim or PCD? I can't remember which you prefer).
Also, can you link to where you are getting your xo parts from so I can see what values etc you have access to.
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