My guess is, that to really lower distortion enough to be audible, you have to go for the waveguide route. A waveguide would raise the output level around maybe 8-10dB - and when lowering the level again in the filter to get a smooth response, you lower distortion too.
Lowering the crossover for the midrange, moves you further away from the breakup of the cone, too - again lowering overall potential audible distortion.
A 1dB drop in amplitude isn't going to make much difference.
Here is a 4th order version of the same, have a look at the difference in the tweeter level at 1K. In the 4th order it is 30 odd dB down, in the 2nd order only about 16dB down. When you choose low slope crossover there is much more asked of the drivers far away from the crossover point and that needs to be considered when choosing drivers intending to use that topology. For low order woofer and mid I would suggest looking at the Scanspeak Discovery drivers as they are very well behaved for a really wide bandwidth. This makes designing a crossover for them much simpler and cheaper 🙂
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Thanks. 1Db drop doesnt make much difference but maybe it could help a bit for the baffle step bump in that area.
I went for the SBacoustic drivers. Got them for a good price and order is on the way.
I choose : SB26ADC ; SB12MNRX2 ; SB23NRXS45-8
They look to be well behaved too and have wide bandwidth.
Like mentioned before targetting XO would be 300-3k Hz. (although I seem to get better simulation with 2k3-2k5, so maybe land there)
When I add some Y offset of the drivers, -120mm for the mid, -400 for the woofer, the dip is almost totally gone. It is the same for LR2 or LR4
For the tweeter it would be better to cross it @ 3K then.
Much will be different when the drivers are measured in the cabinet. Then you will know what you have and can start looking at what will work best.
Not necessarily the SB26 you have ordered has good low frequency output and if you are going to use an Augerpro waveguide it is more important to match the directivities at the crossover point.
When woofer is closer to the mids the dip on axis gets bigger (relative as we speak of 1db when y value is the same. But gives a much smoother DI.
Here woofer with Y -300mm (closest possible with 4"mid and 8" woofer)
and here with woofer @ -500mm
So it is important to keep the drivers as close as possible? Even the woofer?
Here woofer with Y -300mm (closest possible with 4"mid and 8" woofer)
and here with woofer @ -500mm
So it is important to keep the drivers as close as possible? Even the woofer?
@fluid Would it make sense to make some simulations with ideal drivers adapted to the baffle that going to be used?
I made some sims with LR2 and LR4 for mid/tweeter (ideal driver not adapted to the baffle) and outcome is very different. Dig dip with LR2 from 3k to 10k
only small dip at 3-4k with LR4
I made some sims with LR2 and LR4 for mid/tweeter (ideal driver not adapted to the baffle) and outcome is very different. Dig dip with LR2 from 3k to 10k
only small dip at 3-4k with LR4
In those simulations the drivers have no directivity and the directivity of the cabinet is not included so it tells you very little. You can try and make simulations in Vituixcad to include driver and baffle diffraction to get a better idea of the way the woofer and mid will react to distance. Z depth matters as well but can only be estimated without an actual measurement.
It is very hard to say what is the best positioning for the drivers as it depends on so many factors, putting them close together might work or it might be the worst position.
If only designing a speaker could be done with a paint by numbers approach.
Does anyone have the same drivers and can provide the Z-offsets? The drivers are not so uncommon I guess
SB26ADC
SB12MNRX
SB23NRXS
SB26ADC
SB12MNRX
SB23NRXS
If you haven't seen it already have a read of Vineeth's 3 way design thread
https://www.diyaudio.com/community/threads/a-3-way-design-study.376620/
Lots of good information and analysis in there and I made him some BEM cabinet simulations later in the thread.
https://www.diyaudio.com/community/threads/a-3-way-design-study.376620/
Lots of good information and analysis in there and I made him some BEM cabinet simulations later in the thread.
Check the SB site, they have a white paper with some offsets, 18MM for 6 inch vs. tweeter. 16MM for 5 inch to tweeter. My guess for 4 inch would be 14MM. When I used the 4 inch mid I only had a USB mike so I couldn't get a measurement. I have a better setup now, but I'm to lazy to go back and measure again.