Only because of their baffle 'wings', which more importantly than lower LF gain BW is they set its polar response. 😉
'Theory', nothing! It's plain ol' physics of the situation and in theory/practice is 'dead on' when given the (most) correct input it allows. 😉
So can one state that a well designed horn with appropriate driver can extend response 50 to 75 percent further than the mass corner frequency ie. 8PE21 100 hz inlow horn being capable of a 1 - 1.2k xover?
With a ~916 Hz FHM, don't see why not if properly designed, but not familiar with it beyond a local not liking it too much IIRC. Design a horn based on tuning it to its sqrt(87*916) = ~282.3 Hz mean and it comes out something like this, so can in theory EQ it out to the driver's ~5 octave limit = ~2784 Hz and in reality according to HR based on its 1st reflection. 😉
I shook my head and fell down a wormhole.
Found a really good mass corner discussion between Tom Danley, Wayne Parham and Bill Fitzmaurice on another board.
Feel free to set me straight... I'm learning and trying to find my way.
Here are some takeaways that could be relevant to the discussion here:
Mass corner is fact BUT there is consistent proven measurements & response beyond this point!
Why? This what Danley had to say about measuring vs acoustic power sims: "The "DI" is totally real and what is described (reference to DJK's comments in the thread) making the on axis SPL greater than the acoustic power into a non directional (fixed directivity) source would suggest... the on axis SPL can be made nearly flat by choosing a horn who's directivity narrows at exactly the same rate, compensating the power roll off by focusing into a narrower and narrower angle. While this does change the SPL on axis, it does not change the power roll off"
What Danley also said: "...what is measured is what the horn does.
So, Hornresp acoustic power is NOT real world measured SPL (I should have known this and it went over my head thinking it was the same thing).
Keele & Leach math is based on "power" and here is where the mass rolloff comes in. I believe the sims are based on their math, no ?
All the acoustic devices making up a horn system (motor, diaphragm, flare, additional devices) plus speaker circuit including amp and crossover need to be considered and that is also not simulated.
While I admittedly know very little of building horns ... I imagine design experience allows one to move forward instead on getting too stuck on a simulated response.
Found a really good mass corner discussion between Tom Danley, Wayne Parham and Bill Fitzmaurice on another board.
Feel free to set me straight... I'm learning and trying to find my way.
Here are some takeaways that could be relevant to the discussion here:
Mass corner is fact BUT there is consistent proven measurements & response beyond this point!
Why? This what Danley had to say about measuring vs acoustic power sims: "The "DI" is totally real and what is described (reference to DJK's comments in the thread) making the on axis SPL greater than the acoustic power into a non directional (fixed directivity) source would suggest... the on axis SPL can be made nearly flat by choosing a horn who's directivity narrows at exactly the same rate, compensating the power roll off by focusing into a narrower and narrower angle. While this does change the SPL on axis, it does not change the power roll off"
What Danley also said: "...what is measured is what the horn does.
So, Hornresp acoustic power is NOT real world measured SPL (I should have known this and it went over my head thinking it was the same thing).
Keele & Leach math is based on "power" and here is where the mass rolloff comes in. I believe the sims are based on their math, no ?
All the acoustic devices making up a horn system (motor, diaphragm, flare, additional devices) plus speaker circuit including amp and crossover need to be considered and that is also not simulated.
While I admittedly know very little of building horns ... I imagine design experience allows one to move forward instead on getting too stuck on a simulated response.
With hornresp you can also see SPL at various angles, polar response, beamwidth and many other parameters.
So that means two things AllenB:
1) At the time of the mass corner discussion refenced above, 20ish years ago, Hornresp did not include all of those features
2) I have no idea how to use Hornresp properly
Danley did mention that a polar response measurement will identify that effect (SPL on axis) as one see's the radiation pattern collapse vey clearly.
Makes sense. I can only assume it was unavailable in Hornresp at one point.
Correct, just as HR predicts and alluded to in my comment re EQing it flat out to its 5 octave limit.
AFAIK.
AFAIK most of the relevant ones are including thermal power, inductance distortion, etc., but aren't part of the basic sim, you have to choose its option to see its effects. What it does assume is the driver being perfectly pistonic nor does it account for phase plugs or can sim complex profiles. Consider my sim, it has a ~6.685:1 CR, so unless the driver has been designed for such it will be severely power limited and even then further still because its rear chamber and front low pass filter chamber has compressed it so tightly it can barely move except under extreme power; IOW a classic pioneer's design from when a few watts was 'big' power and why the horns had to be so big to get sufficient acoustic power gain to offset it.
This thread got me thinking again about horns. Some years ago I explored this and moved in a different direction. Maybe it's time to try it now.
Would definitely appreciate your input.
I know the B&C 8PE21 are good for horns, but I thought of them as midrange horns, much as Inlow's 135Hz horn uses them. Norma's suggestion to use two per side sent me revisiting...I do have 4 of these drivers, so could 2 per side deliver excellent midbass? It's a bit counterintuitive as I use them as midrange in open baffle from 300Hz to 1200Hz now. Oh well.
I have 4 sealed subs (12" Rythmiks in DIY sealed boxes) that I have ran up to 80Hz. They can probably go a bit higher, but bass starts to get directional above that so would like to cross the horns no higher than 90Hz.
I did a quick simulation on Hornresp. Ideally the horn should be longer, but this length already is likely to have me sleeping in the doghouse for a couple of nights so don't want to go longer. Mouth is rather large, though, at 50x75cm (19.7x29.5"). Kept it conical for simplicity.
The first section was initially intended to be used as a compression chamber but I'm thinking compression is meant to extract more sensitivity out of the system, but my system is active and I would either use a 400W Hypex UcD or 75W KT88 (depending if I need a midrange on top) and this driver is sensitive already so I didn't think compression was needed. So kept it constant and short.
The second section was just a swag, as was the % of total length that it got.
Rear chamber was a swag too.
I'm kind of thinking the simulation looks too good to be true. Seems like something I could cross at 80-90Hz and take it to about 700Hz. Maybe even let go of about 7dB and shave the response to get to 1kHz where I could get my tweeter to get with a larger waveguide.
Looking forward to your feedback. What modelling mistakes am I making? Should I expect this to achieve great performing midbass horns with 2x 8PE21?
Thank you!
Would definitely appreciate your input.
I know the B&C 8PE21 are good for horns, but I thought of them as midrange horns, much as Inlow's 135Hz horn uses them. Norma's suggestion to use two per side sent me revisiting...I do have 4 of these drivers, so could 2 per side deliver excellent midbass? It's a bit counterintuitive as I use them as midrange in open baffle from 300Hz to 1200Hz now. Oh well.
I have 4 sealed subs (12" Rythmiks in DIY sealed boxes) that I have ran up to 80Hz. They can probably go a bit higher, but bass starts to get directional above that so would like to cross the horns no higher than 90Hz.
I did a quick simulation on Hornresp. Ideally the horn should be longer, but this length already is likely to have me sleeping in the doghouse for a couple of nights so don't want to go longer. Mouth is rather large, though, at 50x75cm (19.7x29.5"). Kept it conical for simplicity.
The first section was initially intended to be used as a compression chamber but I'm thinking compression is meant to extract more sensitivity out of the system, but my system is active and I would either use a 400W Hypex UcD or 75W KT88 (depending if I need a midrange on top) and this driver is sensitive already so I didn't think compression was needed. So kept it constant and short.
The second section was just a swag, as was the % of total length that it got.
Rear chamber was a swag too.
I'm kind of thinking the simulation looks too good to be true. Seems like something I could cross at 80-90Hz and take it to about 700Hz. Maybe even let go of about 7dB and shave the response to get to 1kHz where I could get my tweeter to get with a larger waveguide.
Looking forward to your feedback. What modelling mistakes am I making? Should I expect this to achieve great performing midbass horns with 2x 8PE21?
Thank you!
At a glance your throat chamber would be the area of the cone and its volume would be the air trapped between the throat baffle and the cone ? I'm pretty sure the compression ratio comes from the area of the cone vs the area of the throat, so the 1cm length at 150 would not do anything.
8PE21 would usually find itself in a horn that is better crossed higher than 100Hz. On the other hand I've seen it used as a subwoofer in a successful tapped horn, but these are different. The resonance was midband.
2kHz might be good if the wave is well formed and not too narrow.
2kHz might be good if the wave is well formed and not too narrow.
You can't cheat on horn length..
I tried using various 15" drivers in shorter exponential horns. Never got a sound I was happy with ~ 90 Hz to 350Hz.
They modelled / measured okay though.
In fact my first larger conical effort with a 15" sounded better. Didn't fit though a regular door though😂
Longer exponential horn, 12" driver, job done.
I tried using various 15" drivers in shorter exponential horns. Never got a sound I was happy with ~ 90 Hz to 350Hz.
They modelled / measured okay though.
In fact my first larger conical effort with a 15" sounded better. Didn't fit though a regular door though😂
Longer exponential horn, 12" driver, job done.
Hmm.......150 cm^2 throat, 440 cm^2 effective driver Sd = ~2.933 CR, nearly the ~3:1 limit for narrow BW point source horn drivers, so not much low distortion power handling, especially over a wide BW, though obviously a lot better than my earlier instructional sim.
yes, I think that is what I explained in the post.
Here's the same total length, same exit mouth area (S4), same S3, same S1 but compressing to S2=150cm2 and L12=10cm so I reduced L23 by 10cm.
Compared to post #71 what I see is a bit more efficiency at the bottom (albeit reaching to 100Hz rather than 80-90Hz) and dropping faster at 600Hz. Since the compression brings the added efficiency that doesn't seem to be so valuable in the context of available amp power, drops response faster and increases complexity in the build then I was concluding it wasn't worth doing. Happy to be pointed to stuff I might be missing.
When I built my midbass horns I built a 12" version (JBL 2020H) and a 15" version (EVM 15L), both using same mouth size, Expo, JBL version longer to account for smaller throat. I ended up choosing the 15" version, but very little between them soundwise. 15" version very close to the Edgar midbass horn.
You have the same compression in both versions, but the 2nd version should be modelled using the Vtc tab to allow for the different volumes, instead of modelling the throat chamber as part of the horn.
Thank you!!!
I had that wrong. I didn't intend to include compression but didn't realize S1 was for both drivers together...now that I think about it...it should have been obvious. Oh well.
Now with S1=Sd.
Yeap. Not trying to cheat it. How long was your exponential horn for the 12" to cover 90 to 350Hz?
I believe that was JLH using it in a subwoofer. Very knowledgeable! I'm far from that. Do you know how long was that horn, or how high did he play it?