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Multi-Way Conventional loudspeakers with crossovers

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Old 15th December 2018, 11:26 AM   #3131
3wayaddict is offline 3wayaddict  Netherlands
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I still found the measurements to be unrealistic in the lower region below 30 Hz so instead of a 0 - 20 kHz sweep measurement I went to use the SPL meter and the tone generator. And boy, these woofers are in for some serious depth. Calibrating the level to 75 dB with pink noise. I found out it is a smooth rising response to 77 dB @ 30 27 Hz, this is because of the slight intended bass boost because I like a little bit extra thump. Then going lower, in my room these puppies are pushing an F3 of 21 Hz! with still reasonable output in the 15s!
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Old 15th December 2018, 07:44 PM   #3132
planet10 is offline planet10  Canada
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System Pictures & Description
Quote:
stacks of solid MDF also make the structure extremely stiff
It would be stiffer yet if you’d used quality plywood. Nice job otherwise.

dave
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Old 15th December 2018, 08:02 PM   #3133
gzubeck3 is offline gzubeck3  United States
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Quote:
Originally Posted by 3wayaddict View Post
I positioned them properly, added damping material and set the filters and DSP. I have covered all walls of the woofer chambers with damping. I first also did this with the midrange chamber but I removed most of the material again in the end, only leaving the back walls covered to really make sure there's no echoes. With all walls covered the sound became overly bright, lost all of its snap and the SPL dropped with I think nearly 6 dB. It was just absorbing way to much of that magical Satori acoustics energy. My special design of midrange chamber is already doing a amazing job of diffusing the sound waves!
Now with the DSP properly set up, the speakers obviously sound even better, a lot. Man these speakers are just some of the best I've ever heard. Listening to Natalie Merchant - "The Peppery Man". It's as if those cowboys are hidden behind my speakers. And the snap and overal beauty of guitar chords have gotten even better!
I'm assuming that the first graph is what your system sounds like without the dsp alterations. If you do decide to rebuild your passive crossovers I would create a little bit of a bbc dip in the 800-2000 hz range as it looks like baffle diffraction is playing a part in the mid range frequency area. I would also chamfer the front baffle as it looks like you've gone to a lot of work to build good cabinets and this helps when playing louder and also off axis listening.
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Old 17th December 2018, 06:10 PM   #3134
HammerSandwich is offline HammerSandwich
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Originally Posted by 3wayaddict View Post
I made the midrange chamber round with 25 mm plates with smaller getting holes in them.
Thanks for the extra info. Interesting approach!
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Old 17th December 2018, 10:32 PM   #3135
3wayaddict is offline 3wayaddict  Netherlands
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It's a fully active system so I can easily make changes to the crossovers but I don't think a dip in the midrange is necessary because I really like the way it sounds right now and don't think I'll want to change it. And I don't like equalizing the sound to make it seem sound nicer. Just give me the pure flat sound. If then doesn't sound nice, I'll rather look at making changes to the cabinet or drivers.
I was actually planning on making the baffle rounded and actually had it in my design because I think it looks nice and mainly of course for diffraction but the CNC machine I had acces to isn't able to make 3D movements. You need a 5-axle machine to do that and those are unfortunately pretty hard to come by. Luckily my parents are in the interior business and have a lot of contacts with woodworkers and furniture builders so maybe I will some day get to properly rebuild the cabinets.

By the way. What do you guys think of semi-venting the midrange? Just some small holes to let the midrange breathe just a little bit to avoid compression. Not that my midrange doesn't sound nice, AT ALL, but I see some companies like Wilson Audio, and I do think I can hear the midrange slightly changing at higher volumes in a bad way. It's not that worse at all but I just think I can hear a little left potential. Though, at over 15 L my midrange chambers already are rather huge for a 118 cm^2 Sd midrange which should really limit compression. Do you think compression already is pretty much impossible?
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Old 17th December 2018, 11:23 PM   #3136
gzubeck3 is offline gzubeck3  United States
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Quote:
Originally Posted by 3wayaddict View Post
It's a fully active system so I can easily make changes to the crossovers but I don't think a dip in the midrange is necessary because I really like the way it sounds right now and don't think I'll want to change it. And I don't like equalizing the sound to make it seem sound nicer. Just give me the pure flat sound. If then doesn't sound nice, I'll rather look at making changes to the cabinet or drivers.
I was actually planning on making the baffle rounded and actually had it in my design because I think it looks nice and mainly of course for diffraction but the CNC machine I had acces to isn't able to make 3D movements. You need a 5-axle machine to do that and those are unfortunately pretty hard to come by. Luckily my parents are in the interior business and have a lot of contacts with woodworkers and furniture builders so maybe I will some day get to properly rebuild the cabinets.

By the way. What do you guys think of semi-venting the midrange? Just some small holes to let the midrange breathe just a little bit to avoid compression. Not that my midrange doesn't sound nice, AT ALL, but I see some companies like Wilson Audio, and I do think I can hear the midrange slightly changing at higher volumes in a bad way. It's not that worse at all but I just think I can hear a little left potential. Though, at over 15 L my midrange chambers already are rather huge for a 118 cm^2 Sd midrange which should really limit compression. Do you think compression already is pretty much impossible?
There is a db dropoff with an entirely closed cabinet. I've heard about 3 db so you have to account for it in your design. For me I would think that the midrange is less affected than if you we're running a two way and the cone was being pushed to distortion limit on the low end frequency. Maybe some others have some experience there. By the way are your woofers run in parallel or series. Is there an advantage to having two woofers in series or are you doing something different with your active crossovers and multi-amp setup.
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Old 18th December 2018, 07:07 AM   #3137
3wayaddict is offline 3wayaddict  Netherlands
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I'm running two 8 ohm woofers in parallel because I think 4 ohm is a nice nominal resistance for a active system where there's no difficulties with a passive network and because the 8 ohm versions of this woofers performed slightly better in simulation because of the higher force factor. The differences were ever so slightly but it's the small things that matter.
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Last edited by 3wayaddict; 18th December 2018 at 07:09 AM.
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Old 24th December 2018, 12:32 AM   #3138
XMechanik is offline XMechanik  Poland
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A modest 2-way system with SBA SB16PFC25-4 and Seas 27TBFC/G.

At first step only manufacturer's datasheet and simulation data were used, just out of curiosity how far the actual effects from the simulations would be. The result (for this particular design) is that the simulations are in the +- 2dB path with relation to the measurements, with the exception of the 60-80Hz and 2-2.4kHz regions where the error is a bit higher.

System Pictures & Description-sys_resp_simul2-png
Green: characteristics determined from simulations (target). Blue and red: measured characteristics of L and R speakers.

(more about the first step of the design)

In the second step the system crossover was designed based on measurements. The target response was changed to be linear rather than contour-like.

System Pictures & Description-sys_resp2-png
Frequency characteristics:
cyan: dBspl with nearfield LF measurements included,
green: dBspl for the second speaker (low frequency measurements are not included)
red: dBspl for the second set, reversed polarity,
gray: impedance module (with 4R horizontal line marker).

(more about the second step of the design)
Attached Images
File Type: jpg p_sysfr.jpg (102.4 KB, 418 views)
File Type: png sch_meas_lin.png (21.5 KB, 413 views)
File Type: png sys_resp_simul2.png (142.4 KB, 469 views)
File Type: png sys_resp2.png (96.3 KB, 465 views)
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Old 24th December 2018, 10:45 AM   #3139
wolf_teeth is offline wolf_teeth  United States
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Likely not the right place for a build thread, nor for constructive criticism, but the 43 ohm resistor across the woofer is likely going to get HOT as it will see the entire bass range. If you honestly have to have this part for some reason, make it 25W+ rated.

Normally, this would be to likely to droop the Fs magnitude of the woofer to bring down the ripple that the LP coil would induce from this. It still is not the best idea for a fix in this regard. My opinion if you have to have it, is to keep the value above 50 ohms. You don't want a lot of current going through it, and the value is better above this point.

Later,
Wolf
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Old 25th December 2018, 09:13 AM   #3140
XMechanik is offline XMechanik  Poland
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Quote:
Originally Posted by wolf_teeth View Post
Likely not the right place for a build thread, nor for constructive criticism
I'm sorry that I possibly posted in the wrong thread. If this is the case, could someone help please and redirect this to more appropriate place...

Quote:
Originally Posted by wolf_teeth View Post
but the 43 ohm resistor across the woofer is likely going to get HOT as it will see the entire bass range. If you honestly have to have this part for some reason, make it 25W+ rated.

Normally, this would be to likely to droop the Fs magnitude of the woofer to bring down the ripple that the LP coil would induce from this. It still is not the best idea for a fix in this regard. My opinion if you have to have it, is to keep the value above 50 ohms. You don't want a lot of current going through it, and the value is better above this point.

Later,
Wolf
Power handling of the 43ohm resistor was also my concern so I did the following estimation:

For the 4ohm midwoofer applied power handling is given as P=40W so the max RMS voltage can be estimated
P=(U^2)/r => U=(P*r)^.5=(40*4)^.5=12.6Vrms (17.8V sine amplitude). Exceeding this for a longer time would probably damage the speaker.

This voltage was used for estimation of max power dispatched in the 43ohm resistor (assuming worst case frequency for which coils make short circuit and capacitors are circuit breaks), P=(12.6^2)/43= 3.7W so the conclusion was that there should be no problem as even the cheapest 5W resistor still has some power headroom (actually I applied 10W resistor for this one).

Simple experimental verification. The system was played with average signal levels (volume control at 10-11 o'clock position) for approx 2 hours then resistor temperature was measured with a simple procedure (touching finger). I wasn't hot at all in fact it didn't even feel warm.

Why is this resistor used - it makes a significant correction in the mid range, see graph. Blue:resistor removed from the circuit, Gray: resistor used.
Attached Images
File Type: png 43ohm.png (13.9 KB, 44 views)
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