Related...I think:
I was wondering about doing a 2.5 way where the .5 was ported and the other (same driver) was sealed. What major issues are there here? I see phase (~60deg) and a peak at F3 in group delay...anything else?
Regards,
Aaron
Edit: the phase shift and group delay were specific to my model on RS125's using Zaph's measurements.
I was wondering about doing a 2.5 way where the .5 was ported and the other (same driver) was sealed. What major issues are there here? I see phase (~60deg) and a peak at F3 in group delay...anything else?
Regards,
Aaron
Edit: the phase shift and group delay were specific to my model on RS125's using Zaph's measurements.
'2.5 ways are best suited to identical bass drivers' - probably depends how low you cross them over; I'm currently using a 2.5 way with 5"Peerless mid-bass & oddball 8" bass units, crossed over at around 120Hz - I'm very happy with them.
5" & 8" units in separate cabs, both ported; the 8" units are EBS alignment (because they're both different units - cabs tuned differently to get same response).
I'm going to try blocking the ports on the 5" cabs & add an extra cap in the xover to see how they sound, but with a touch of bass boost at the amp, this system sounds really solid & clear - love it...
Cheers,
Pete McK
5" & 8" units in separate cabs, both ported; the 8" units are EBS alignment (because they're both different units - cabs tuned differently to get same response).
I'm going to try blocking the ports on the 5" cabs & add an extra cap in the xover to see how they sound, but with a touch of bass boost at the amp, this system sounds really solid & clear - love it...
Cheers,
Pete McK
As pointed out above, it seems it really is a 3-way, but using the same drivers for the mid and bass. On another forum, I got this methodology from djarchow:
"1. Measure spl and phase of all drivers on the actual baffle.
2. Designed the XO for the transition between the mid/woofer and the tweeter but didn't include any baffle step compensation in the XO.
3. Then I designed a cascaded XO for the .5 woofer. By cascaded, I mean that the input to this XO section was the output of the full range woofer XO. I needed about a 1st order low pass acoustic rolloff from about 150 hz to about 1000 hz where the mid woofer XO started kicking in and rolling the .5 woofer off with a 4th order slope.
4. Then I went back and reoptimized all the sections of the XO to more closely match my target responses and started listening and voicing the XO.
The hard part was getting the .5 way driver to fill in for the bafflestep loss completely yet still roll off soon enough not to mess up the mid/tweeter XO region."
Problem for me: no measurement equipment! Also, is all that necessary?
Based on the RS125 model, I'm looking at the sealed F3 of ~100Hz and a baffle step around 700Hz. So, the sealed driver would need help from 700 down to 100Hz. A simple LP on the ported 0.5 starting around the 700Hz could compensate for the BS and only have ~600Hz of overlap of ported and sealed drivers. Is this correct thinking?
"1. Measure spl and phase of all drivers on the actual baffle.
2. Designed the XO for the transition between the mid/woofer and the tweeter but didn't include any baffle step compensation in the XO.
3. Then I designed a cascaded XO for the .5 woofer. By cascaded, I mean that the input to this XO section was the output of the full range woofer XO. I needed about a 1st order low pass acoustic rolloff from about 150 hz to about 1000 hz where the mid woofer XO started kicking in and rolling the .5 woofer off with a 4th order slope.
4. Then I went back and reoptimized all the sections of the XO to more closely match my target responses and started listening and voicing the XO.
The hard part was getting the .5 way driver to fill in for the bafflestep loss completely yet still roll off soon enough not to mess up the mid/tweeter XO region."
Problem for me: no measurement equipment! Also, is all that necessary?
Based on the RS125 model, I'm looking at the sealed F3 of ~100Hz and a baffle step around 700Hz. So, the sealed driver would need help from 700 down to 100Hz. A simple LP on the ported 0.5 starting around the 700Hz could compensate for the BS and only have ~600Hz of overlap of ported and sealed drivers. Is this correct thinking?
s7horton said:
The midrange section of a crossover is notoriously difficult to design so the obvious advantage of a 2.5 way is that none of the mid-bass drivers requires a low-pass filter. However in my experience a well-designed "true" 3-way is superior in sonic quality, mainly because it allows each driver to remain well within the frequency range they are the most comfortable with (i.e. where the response curve is the flattest). Some say that that this reduces the need for compensation circuits but one could argue that it also introduces phase coherency issues in turn require complex compensation at the midrange level.
I guess it comes down to budget and how much of a headache you're willing to deal with
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