4th order Linkwitz Riley. Delay the LF driver so that it acoustically aligns with the horn.
Not relevant as the predominant harmonic of a B0 string on a bass is 2H or ~62Hz. There is no need for a flat 30Hz. Most of the classic bass cabs like SVTs roll off well above 40, usually above 65Hz as a 34" bass cannot produce a fundamental stronger than the 2H until at least A1. Last fridge I measured was -3dB at 80Hz.
I'd say that bass cabs are not built like that because there is no output from any bass at its fundamental. It is because of Hoffman's iron law combined with the poor backs of roadies and players.
I agree with you that the second harmonic is dominant at the lower end. But that does not mean that there is no fundamental at all. The strings do visibly oscillate with their fundamental. If the rest of the chain can process it - it will also come out acoustically. Robinson-Dadson will also take it's toll of course - affecting the fundamental's perception. I often play my ERBs through my large MTMs , wich are down by about 6dB @ 30 Hz and the low end reproduction is a treat.
BTW: I guess the nonlinear behaviour of the pickups is at least partially responsible for the dominant h2 at lower frequencies.
Depending on what kind of music you are listening to it can make quite a difference whether a speaker goes to 30 Hz. or 40 Hz.
Regards
Charles
I agree with you that the second harmonic is dominant at the lower end. But that does not mean that there is no fundamental at all. The strings do visibly oscillate with their fundamental. If the rest of the chain can process it - it will also come out acoustically. Robinson-Dadson will also take it's toll of course - affecting the fundamental's perception. I often play my ERBs through my large MTMs , wich are down by about 6dB @ 30 Hz and the low end reproduction is a treat.
BTW: I guess the nonlinear behaviour of the pickups is at least partially responsible for the dominant h2 at lower frequencies.
Depending on what kind of music you are listening to it can make quite a difference whether a speaker goes to 30 Hz. or 40 Hz.
Regards
Charles
Its a trick used in some classic coaxial speakers. CD is behind LF cone, so lower xo order for HF helps with phase around xo frequency.
In your speakers it looks like same situation, horn is deeper than LF cone, so CD is behind acoustic center of the woofer.
Of course, with DSP you should be able to add time delay to LF to make that acoustic alignment. But Iam an analog guy, hence my recomendation for different slopes.
I never said that: I said the primary determinant of tone is the 2H and is more important. I play 5 and 6 string basses. You don't need a 30Hz f3 to be able to tell tone or timing, and live, it makes zero difference. You'll have a hard time convincing me that a 30Hz f3 makes any significant difference to a B0 reproduction over 40Hz, especially blind.
You have a DSP. So simply make the biggest box sealed box you can comfortably live with and equalize the bass response to taste in the room. At the end of the day the following factors will determine bass response with that driver (in order):
1) The room (dimensions and construction)
2) The drivers surface area
3) The drivers stroke (Xmax)
Of course, this assumes that you have enough amplifier power.
1) The room (dimensions and construction)
2) The drivers surface area
3) The drivers stroke (Xmax)
Of course, this assumes that you have enough amplifier power.
Umm my post is about recommendations on the crossover and slope for my drivers for coherency.
Well aware of the wonderful things dsp can do.
A lot of good no nonsense advice here. So I'll chime in. 
With a 15" woofer and a 1.4" CD I start at 700Hz 3d order and work from there looking at diver curves, overlaps, phase and combined response. With DSP I usually end up where Brett suggests, 4th order L-R or Bessel. With passive a sort of 3rd order whatever works thing. Often there is a good bit of electrical spread of underlap to get a proper blend. Finding the ideal acoustical crossover point often takes me a very long time, but getting one that "works" can be pretty fast.
Good luck. have fun!
With a 15" woofer and a 1.4" CD I start at 700Hz 3d order and work from there looking at diver curves, overlaps, phase and combined response. With DSP I usually end up where Brett suggests, 4th order L-R or Bessel. With passive a sort of 3rd order whatever works thing. Often there is a good bit of electrical spread of underlap to get a proper blend. Finding the ideal acoustical crossover point often takes me a very long time, but getting one that "works" can be pretty fast.Good luck. have fun!
I was addressing all the talk about what to do WRT the bass cabinet. Feel free to ignore ;-)
If you choose the right 15" (or thereabouts) woofer you can even use a 1" CD. I've seen lots of successful designs using a JBL 2226 and a B&C DE250 or any Radian 1" CD. There are a few 15" woofers what can reach 1kHz or more and several 1"CD that can easily dip below 1kHz (assuming you use an appropriate size horn/waveguide) in domestic use. In my experience, there are many more choices in horns and CDs if you stick to 1" - not to mention the improved top end.A lot of good no nonsense advice here. So I'll chime in.
Good luck. have fun!
Oh course! I've done so on several rigs. In commercial PA speakers I never liked 15"+1" because the vocals never sound right to me. A 12 or 10 inch woofer with a 1" CD does better for voice. But for home use you certainly can get it right, if - as you say - you pick the right drivers.
A 15" (381mm) driver will start to narrow it dispersion at about 570Hz.
f = (2 * C) / (pi * D),
(2 * 343) / (3.14 * 381) = 573Hz
Where
C= speed of sound 343m/s
D= Driver diameter
Just an update guys!
From all your inputs, I tried out:
HP 12db/octave and LP 18db/octave at 1200hz
and
HP and LP at 900hz LR24db
Also delayed the woofer by around by .232ms based on formula recommendations from minidsp using REW.
Currently, in favor of the mismatched slopes approach, I dunno, vocals seem more integrated with this one.
Thank you all for the recommendations.
Will now research more on matching dispersion and the effect of distance and horn components.
Next time ill try to design around the room and components instead of the vanity of having a wood horn poor man's TAD 2402 hahahaha
From all your inputs, I tried out:
HP 12db/octave and LP 18db/octave at 1200hz
and
HP and LP at 900hz LR24db
Also delayed the woofer by around by .232ms based on formula recommendations from minidsp using REW.
Currently, in favor of the mismatched slopes approach, I dunno, vocals seem more integrated with this one.
Thank you all for the recommendations.
Will now research more on matching dispersion and the effect of distance and horn components.
Next time ill try to design around the room and components instead of the vanity of having a wood horn poor man's TAD 2402 hahahaha
I think your preference to the mismatched slopes has more to do with the higher crossover frequency than the mismatched slopes, but as I don't have direct experience with the drivers and horn you are using it's impossible for me to say. If you haven't already, I would try the 1200Hz with 24db LR slopes and see what you get. Don't forget to add the correct delay to adjust for the drivers acoustic centers as you change the crossover.Have some fun and listen to some music!
Dispersion should be more or less OK in either case (900Hz / 1200Hz) but I guess 900Hz would sound smoother (without narrowing) when sine swept from woofer into the horn.
Also, hornwannabe, could you please show some close-up shots of the compression driver throat and phase plug ? Also, is this driver the PA-D99 or the throatless PA-DE99 ? I'm asking since I guess it was you in the following thread.
https://www.diyaudio.com/community/...d-driver-that-can-reach-500-hz.321521/page-11
Also, hornwannabe, could you please show some close-up shots of the compression driver throat and phase plug ? Also, is this driver the PA-D99 or the throatless PA-DE99 ? I'm asking since I guess it was you in the following thread.
https://www.diyaudio.com/community/...d-driver-that-can-reach-500-hz.321521/page-11
Apologies for being a snippy little snot, but if you're going to present the arithmetic warrjon, please use the piston diameter. For typical JBL 15's that's about 12½ inches, ~318 mm.
Other member's points about the gradual increase in directivity are worth noting as well.
Again, sorry for picking nits.
Cheers
Other member's points about the gradual increase in directivity are worth noting as well.
Again, sorry for picking nits.
Cheers
Oh yes that is indeed me.
As you can see, my past idiot self got slapped by physics.
Was able to attempt a 500hz crossover.
A lesson I learned from this was:
Even if it's possible it doesn't necessarily mean it's a good idea hahaha
God this build was 3 years in the making since I finally finished it last year!
Anyway since you're so intent on the info, Ill attach the pics and I used theseto mate the horn to the CD
https://www.parts-express.com/Eminence-HA14-2-1-1-4-Aluminum-Horn-Adapter-290-5626
Attachments
That's really pancake and very thin but also has a large diaphragm (4") that might play down to 500Hz on a bigger horn e.g. ES-290, as used by Mr. Crowe. Unfortunately, these bi-radials are difficult to build, even when 3D CAD files are available in many cases.
The ES600 appears to be about 8" deep, of which two inches are the "lips" at the mouth, making this horn rather similar to the JBL 2370 in size. The 2370 was used along with the 2225 (same as you) in the 4671 model (which also looks very similar to yours) crossed over at 800Hz. However, considering the size of the horn (alone), it is likely that even the 4671 might actually sound better crossed at 1200Hz, as you have already discovered with your speaker.
The ES600 appears to be about 8" deep, of which two inches are the "lips" at the mouth, making this horn rather similar to the JBL 2370 in size. The 2370 was used along with the 2225 (same as you) in the 4671 model (which also looks very similar to yours) crossed over at 800Hz. However, considering the size of the horn (alone), it is likely that even the 4671 might actually sound better crossed at 1200Hz, as you have already discovered with your speaker.