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Re: 3pi with Sonido SCW-300 [message #70317 is a reply to message #70314] Mon, 28 November 2011 07:55 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 17606
Registered: January 2001
Illuminati (33rd Degree)

Assumimg your woofer models well in a basic T/S simulation, I would probably start with the same cabinet - same driver/horn mounting locations, same port location, etc. Then dial-in the crossover as described earlier in this thread. That way you'll know you're starting from a point that is 90% done already. All you'll really have to do is to adjust the crossover to account for the differences in the behavior of your midwoofer in the crossover region. You'll need measurement equipment, of course, but it could be that the crossover works as-is, or maybe with just a few uF change on a capacitor or something like that.

Re: 3pi with Sonido SCW-300 [message #70331 is a reply to message #69968] Tue, 29 November 2011 17:13 Go to previous messageGo to next message
chakija is currently offline  chakija
Messages: 14
Registered: October 2011
Location: Serbia
Chancellor
Wayne, original box for 3pi is not suitable for these woofers because they need more volume to have proper bass response (according to winISD).
I think i need cca 30l more box volume.
Is there any way to add volume to original 3pi without ruining perfect forward lobe too much ?
Here are measured T/S parameters for mine 2 woofers:

Fs 32Hz
Mmd: 25 g
Mms: 31.12g
Cms: 0.795 g
Rms: 2.721 kg/s
Vas: 260l
Xmax: 4,5mm
Sd: 480cm2
Re: 1mH
Bl: 9.95 Tm
Qms: 2.3
Qes: 0.48
Qts: 0,397
no: 1.7213
SPL: 94.3 db-1W/1m
Re: 3pi with Sonido SCW-300 [message #70332 is a reply to message #70331] Tue, 29 November 2011 17:48 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 17606
Registered: January 2001
Illuminati (33rd Degree)

The forward lobe will be right as long as driver spacing and crossover phase are right. That part is really a function of the crossover and of the midwoofer and horn position on the baffle.

The stock box will work with your woofer, but as you've seen, response will fall off below 80Hz. As long as you're running flanking subs, that will be fine.
If you change box size, what's affected most is the Helmholtz tuning and the position of standing wave nodes. Those will change bass, midbass and lower midrange characteristics. My suggestion is to start off by making the box proportions and port position similar to the standard model. In other words, just grow the box by the amount needed, but keep the same proportions. Put the port at the same distance - about 300mm (center-to-center) and diagonal. I would still suggest you check the response with measurements, paying attention to the bass and lower midrange. But these suggestions will give you a good start.

Re: 3pi with Sonido SCW-300 [message #70336 is a reply to message #69968] Wed, 30 November 2011 17:00 Go to previous messageGo to next message
chakija is currently offline  chakija
Messages: 14
Registered: October 2011
Location: Serbia
Chancellor
Hi Wayne,
I took your advice and made original box proportionally larger so that inner volume is cca 137 liters. I applied distance between horn and upper edge and 285mm c2c for woofer and tweeter.
I decided to flush mount woofer because i like it that way Smile and i will fix alignment with crossover if needed. Material is MDF, front baffle 25mm and side are 19mm. Bracing in corners is 30x30mm and other two are 20x50mm made of hardwood. I made BR vent 105 because bass box pro (that i am simulating with) showed too big vent noise for smaller diameter. I will fine tune length later, but it will be around 70mm.
If you say this all is good enough, i will send cutting plans in workshop asap Very Happy
One more question... do you have any experience with motor run capacitors used in crossover instead of "audio grade" caps?

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Re: 3pi with Sonido SCW-300 [message #70345 is a reply to message #70336] Wed, 30 November 2011 19:49 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 17606
Registered: January 2001
Illuminati (33rd Degree)

Motor run caps are hit and miss. Some are excellent, so it's worth experimenting with them, in my opinion. But some are too lossy and others just plain sound bad. The ones to avoid are the poly caps. The oil filled ones are the ones you want.

Box simulators that show port airspeed almost always give DIYers the wrong impression. If you're building a prosound subwoofer, then you really need the displacement capacity and the performance at full excursion is important. But hifi mains are completely different and you shouldn't be overly concerned with airspeed "chuffing" problems.

If you're push the woofer hard enough to get port chuffing, then you have other problems anyway. We aren't expecting a lot of excursion from the mains - don't want it - because it causes intermodulation distortion, which is a bigger potential problem than vent noise.

The rule of thumb is to keep port airspeed under 100KPH. But the box simulators usually calculate airspeed at full excursion. This is unrealistic. If you want to get a better idea of minimum port size for mains, run the numbers at a fourth of full excursion.

I would also be concerned with standing waves, as already mentioned earlier in this thread. Larger ports tend to be more prone to cause midrange ripple. Not that I'm opposed to large ports - far from it - if you can have your cake and eat it too, all the better. A large port situated so that there is no midrange ripple is just fine. But it does bring back an issue I've mentioned before. You'll need to test this loudspeaker to see what effects your changes have made.

Having said that, I wouldn't worry about it too much. You only went to a 4" port, which probably won't give you any trouble. Hard to say, really, since the port length also comes into play. Only measurements will tell you for sure.

So you'll definitely want to get out the measurement gear and test the speaker, looking not only for the position of the nulls but also for ripple in the lower midrange, between 80Hz and 200Hz or so. These are the two things most likely to need adjustment. If you find ripple in the lower midrange, you'll want to change the size, shape and/or position of your port. If you find ripple in the crossover region, or if the nulls aren't above and below the centerline by approximately +/-25°, you'll need to adjust crossover component values. I find the midwoofer values are usually easiest to modify without a complete redesign. A little movement of one of two component values will shift the nulls and slightly change the response.

Good luck!

Re: 3pi with Sonido SCW-300 [message #71193 is a reply to message #69968] Thu, 02 February 2012 14:30 Go to previous messageGo to next message
chakija is currently offline  chakija
Messages: 14
Registered: October 2011
Location: Serbia
Chancellor
I finally managed to "complete" boxes for my 3pi clone.
I must say that results are very very satisfying Very Happy
For now I feel like I don`t need to adjust anything in crossover. Sonido woofers are really superb performers. Bass is very well defined, and goes low enough. They blend with B&C250 perfectly with your 3pi crossover. They show absolutely no sign of cone breakup and sound very linear and smooth.
I used a little program called "Box notes" that helped me to determine right proportions for box. BR pipe is made of 3 peaces of 20mm birch plywood as you explained in plans for 3pi.
Woofer is offset 10mm from vertical axis because of side standing waves. I believe that this is not audible, but it is not bothering me aesthetically so i decided to give it a try.
Final outer dimensions for boxes are 870x540x380mm.
Note my pink high-end stands. They are ofc temporary, but in this sloped position I have best results. Back side of box is resting on some 3mm rubber pads.
I tried to put them on some 150mm stands but got much worse bass response.
For now here are some final pictures of boxes. I hope that I will menage to put some pictures from building process.
I am really enjoying the sound of this great loudspeakers.
I want to thank you Wayne for all your generous contribution for DiY community!


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Re: 3pi with Sonido SCW-300 [message #71194 is a reply to message #71193] Thu, 02 February 2012 15:22 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 17606
Registered: January 2001
Illuminati (33rd Degree)

Looks very nice! Thanks for reporting back with your impressions of the Sonido woofer!

Re: 3pi with Sonido SCW-300 [message #74439 is a reply to message #69968] Sun, 11 November 2012 14:56 Go to previous messageGo to next message
chakija is currently offline  chakija
Messages: 14
Registered: October 2011
Location: Serbia
Chancellor
It has been almost 9 months since i have assembled my 3pi sort-of loudspeakers, and boy what a listening joy did they bring me.
In meantime, I have had mine H290 plastered with cca 2 lb of plumbers putty Smile .
I have one issue that is bothering me...
Sonido woofers sound really good, with beautiful mids and nice lows.
However, i think that manufacturer has been too optimistic with sensitivity specs.
Only with cca 70R value on R1 I found DE250 enough tamed to play together with sonido.
I dont know how much is it in db but sure is plenty.
I am afraid that with this much attenuation i will "kill" loudspeakers dynamics Smile
Other values on crossover are same as on original 3pi, and I feel no need to adjust anything.
So, my question is, if I apply this much attenuation on R1, which values on crossover would I need to adjust to have best response ? (this is mostly refereed on R2)
Re: 3pi with Sonido SCW-300 [message #74443 is a reply to message #74439] Mon, 12 November 2012 01:08 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 17606
Registered: January 2001
Illuminati (33rd Degree)

Please see the link below for a chart of values for various attenuation levels:
Re: 3pi with Sonido SCW-300 [message #74453 is a reply to message #69968] Mon, 12 November 2012 15:48 Go to previous messageGo to previous message
chakija is currently offline  chakija
Messages: 14
Registered: October 2011
Location: Serbia
Chancellor
Thanks again Wayne!
Chart was very helpful.
For now, i settled with 42R R1, 12R R2, 0.25uF C1.
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