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Multi-Way Conventional loudspeakers with crossovers

Open Source "Tower XL"
Open Source "Tower XL"
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Old 6th December 2018, 09:00 PM   #741
Aatto is offline Aatto  United States
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Open Source "Tower XL"
Hey Gable and thanks for the help

Regarding rear mounting, the TD8Ms front panel is not flat and has a angled frame, the TD15Xs have a rubber thing going around the frame which is not designed to be mounted behing the baffle, so rear mount is not an option , we may only need the front or flush mount, which will reduce the needed inserts
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Last edited by Aatto; 6th December 2018 at 09:03 PM.
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Old 6th December 2018, 11:03 PM   #742
tmuikku is offline tmuikku  Finland
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Gable, there is good measurement preparation paper by kimmosto, he recommends ARTA https://kimmosaunisto.net/Software/V...eparations.pdf
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Old 6th December 2018, 11:07 PM   #743
LORDSANSUI is offline LORDSANSUI  Brazil
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Quote:
Originally Posted by pcgab View Post
Is REW the right software to use? I'm familiar with taking measurements with REW, fwiw. I'm happy to use ARTA, or anything else that's open source/freeware, etc.
Hi pcgab, I'm planning to try RiTA software in near future, it's pretty close to Smaart and is freeware. It may worth a try.

Below there is a video that you can learn a little about it, the Youtuber also offer some videos comparing some softwares including RiTA and other famous.

The website is in Spanish but the software is in English.

YouTube

RiTA – EducaSound
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Old 7th December 2018, 07:44 AM   #744
Paul Vancluysen is offline Paul Vancluysen  Belgium
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Hi Gable,

Great that you will start with IEC baffle!

Here already some tips. Please ask for the info you are missing.

I have built a 225 Hz IEC baffle, made it in two parts and screwed together at the backside with some wooden boards. Easy to remove and replace. My baffle is placed a little above the ground in a way there is the same distance from ground, walls and ceiling for the longest FFT window without reflections.

For the inserts, in my case I only do flush mount. It is some work to make, but the most accurate without baffle diffractions and compatible with the in cabinet baffle mounting. In that way the drivers are all flush with the IEC baffle. You can leave the micro at same position on axis for all drivers. Interesting for AC measurement also.

As measurement, mls is recommended of course. 2 – 3 times repetitive is more than enough.

REW, I don’t know so good, but sometimes I use it to see measurements. Not possible to read absolute time of impulse start, I think. In REW I find it more difficult to set the start of the FFT window at the impulse start. In my Clio I have more resolution. It is important to set this time accurate to obtain the correct phase at the AC center. All by all I think REW can be used, it is also well known.
Maybe others can give you extra tips, also to measure AC.

No experience with Arta.

Measurement distance: 1m. 3m will be difficult in a room I suppose w.r.t. reflections.

Off axis: steps of 15 degrees in horizontal plane (one side) is ok. 15, 30, 45, 60 degrees. If possible to do 75 and 90 in your room, also welcome. Then I can calculate DI in a single hemisphere for drivers with the same horizontal and vertical response (midrange and woofer). But no really need for 75 and 90 degrees. Vertical off axis measurement in a room will be difficult probably. If possible at the upper side, nice. Then we can measure the chosen CD tweeter with horn also in the vertical direction. It has different horizontal and vertical off axis responses.

Voltage, minimum 1Vrms and normalizing to 2.83 Vrms is ok. For tweeter, start frequency 200 Hz, not lower.

Best to measure also the impedance on IEC. The results are a little different than free air, but more conform the infinite baffle response of the driver.

Nearfield measurements are interesting to check TSP. I do it with slow little sine wave sweep at 5 mm of the cone.

DC resistance of voice coil with accurate multimeter. Good to have a calibrated resistor around 10 – 20 Ohm to compare with.
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Old 7th December 2018, 11:47 AM   #745
mbrennwa is offline mbrennwa  Switzerland
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Quote:
Originally Posted by Paul Vancluysen View Post
As measurement, mls is recommended of course. 2 – 3 times repetitive is more than enough.
Nothing wrong with MLS, but I changed to sine sweeps, because you can set the bandwidth limits of the test signal.

Quote:
Originally Posted by Paul Vancluysen View Post
REW, I don’t know so good ... Maybe others can give you extra tips, also to measure AC.
MATAA
(Of course this is the very best audio testing software that ever existed ;-), but I admit it's not easy to set up if you don't know what you're doing.)

Quote:
Originally Posted by Paul Vancluysen View Post
Voltage, minimum 1Vrms and normalizing to 2.83 Vrms is ok. For tweeter, start frequency 200 Hz, not lower.
How do you set start frequency with an MLS? Do a high pass filter to the MLS signal first?

Also, I never really how signal levels are set... I believe it's trivial, but some of my synapses seem to run in circles with this. Will the measurement results be the same in terms of SPL level if different test signal forms (with different spectra) are used as long as the signals all have the same RMS voltage (MLS, sine sweep, white/pink/red noise, etc.)?
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Old 7th December 2018, 03:54 PM   #746
Paul Vancluysen is offline Paul Vancluysen  Belgium
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Matthias,

How stupid can I be, of course with a mls measurement, frequency start cannot be set to 200 Hz. I meant for the tweeter impedance measurement with a swept sine, to limit the low frequency to 200 Hz. And also not more than 1 Vrms on a tweeter.

Concerning the relation, voltage and SPL with different measurements. With the Clio I measure different SPL levels at the same rms output voltage for swept sine and mls. I don’t know anymore which one is higher or lower. I think it is related to power level and bandwidth of noise sources. I have no answer for it at this moment. I will have a look at later and do some tests again with my Clio.
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Old 7th December 2018, 04:19 PM   #747
pcgab is offline pcgab  United States
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Open Source "Tower XL"
Thank you Paul, and everyone.

I think I have what I need to finish preparing for the measurements.

Cheers,
Gable
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Old 7th December 2018, 05:01 PM   #748
Juhazi is offline Juhazi  Finland
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REW supports 2-channel measurements now, with loopback wire for timing reference. But of course it's priorities are for room response analysis. It's impulse response export choices are not always suitable for simulators, most of which prefer MLS based formats.

Other choice is Holm Impulse (free) or OmniMic (registration fee to get full features)
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Old 7th December 2018, 07:58 PM   #749
mbrennwa is offline mbrennwa  Switzerland
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Quote:
Originally Posted by Juhazi View Post
... impulse response export choices are not always suitable for simulators, most of which prefer MLS based formats.


Why would it matter if the impulse response was measured with an MLS or other test signal? An impulse response is an impulse response is an impulse response...
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Old 9th December 2018, 09:15 AM   #750
Paul Vancluysen is offline Paul Vancluysen  Belgium
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In attach a proposal for a plan to realize the Tower XL prototype.

Headlines are:

1. IEC baflle measurement of all drivers
SPL on and off axis, impedance and AC (acoustical center)

2. Make infinite baffle driver models using the IEC baffle measurements
To compare all responses with datasheet values. Calculate the AC offsets.

3. In cabinet measurement of all drivers
SPL on and off axis, impedance

4. In cabinet response simulations of all drivers
To compare with the “in cabinet measurements”. Using Leap or other software.

5. Create SPL and impedance curves (and frd’s) for X-over design
Using TSP data and measured cabinet responses and do some splicing. To be done in Leap or other software.

6. Design of X-over
To choose filter concepts some digital designs can be done at first, using miniDSP or other digital processor.
Starting with a passive filter is possible too.
To be done in Leap or other software.

7. In cabinet measurement of filtered drivers
SPL on and off axis axis

8. In cabinet measurement of the sum response
SPL on and off axis

9. Listening, tweaking with measurement checks

10. Build passive filter if not done yet.
- Check SPL on axis of each driver and the sum response, impedance at input of X-over
- listening test.

More details about the measurement conditions and contents in attached document.

Comments are welcome.
Attached Files
File Type: pdf Plan for Design Tower XL project.pdf (158.3 KB, 32 views)
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