SBAcoustics NAC-61 SB17NBAC35-4 and SB26ADC000-4 .FRD .ZMA sharing

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#41
Oh! Mr. Dave design of reverse polarity of tweeter seem work best. I will use your crossover design for my speakers. I am so gratitude to Mr. Dave's afford for helping other people whom lack of knowledge and experience. I am agree with Mr.Turbowatch 2 ( I have to listen more. I apologized for some of my manner, I will improve myself)
back to crossover, I want to know why reverse polarity of tweeter seem better than??? I never think about reverse polarity before because original NAC-61 has no Polarity reverse in tweeter.
 
#42
Troels doesn't post reverse null images for his LR crossovers. A personal choice I suppose.

The reason the tweeter polarity is reversed is:
a) you have a flat baffle
b) I have used a steeper slope on the SBNAC to damp the breakup and to get phase alignment with a flat baffle.

Now - 2 caveats with my crossover:
1. I have based this on simulation and not measurements. there's always a chance I've got something wrong
2. There is no off axis data to show you how the speaker will behave in the room / power response. that is - it may look good on-axis but may have more peaks and dips due to the slopes chosen as you move off axis. Without measurements, there is no certainty here
 
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#44
I would buy a couple of extra resistors so you can pad the tweeter down some more. Say 1 ohm and 2 ohm. Also make all resistors 10w. The resistor in the woofer circuit I haven't modelled for power handling but shouldn't need more than 10w. You could double up to be sure if you can't buy a 20w resistor. That is 2 * 1ohm in parallel
 
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#47
The last crossover I posted had a 2 ohm tweeter resistor. This provides a "flat" on axis response, but you may find the tweeter too hot in your room. By using 3 ohms, then 4 ohms, here is how it pads down the tweeter

Light blue line = 2 ohm tweeter resistor
Medium blue = 3 ohm resistor
Dark blue = 4 ohm resistor

These changes do not require any other crossover changes.

1694565805359.png
 
#48
The SB17NBAC may have a peak as shown ~ 760Hz. I say may, as this is all simulated data, no off-axis measurements, so whether this peak is real or not I can't guarantee.

However, if you find vocals a bit "shouty" on the speaker. it could be this peak. I have added a notch filter highlighted below. you can see how it flattens the region. It does require quite a large inductor (4.7mH)

1694566885755.png


Impedance is not impacted (i.e. minimum is still 4.5 Ohms ~ 2700Hz
1694566927188.png
 
#50
I found this measurement I took of the SB17NBAC35-4 (I have 2 waiting to go into a project). Although this gate is extremely short, there is no 760Hz hump. Unfortunately I can't recall the baffle size and measurement conditions. In otherwords, I don't think that notch filter will be needed:

1694568719654.png
 
#52
I am so gratitude for you help so much. I think in case of 760hz peak can not correct by crossover. Maybe I use EQ in Jriver Media player software to adjust about 2db around that problem. However if crossover can be redesign to cope with it, I will be so glad to adjust.
 
#54
The last crossover I posted had a 2 ohm tweeter resistor. This provides a "flat" on axis response, but you may find the tweeter too hot in your room. By using 3 ohms, then 4 ohms, here is how it pads down the tweeter

Light blue line = 2 ohm tweeter resistor
Medium blue = 3 ohm resistor
Dark blue = 4 ohm resistor

These changes do not require any other crossover changes.
Thank you so much mr. dave. I will add 1R resistor next to 2R resister to pad down the tweeter.
 
#58
I can't play loud in my bedroom. It will bother neighbor even i close windows and turn on air condition. The fine is expensive if he sue. I usually play around 60-72db max distance 2 meters. However i have 2nd amp 6n2 4p1l push pull around 8 watts.
 
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