kipman725: thanks for the link. The last time I measured T/S parameters was years ago, before I had REW. From memory, it involved measuring with a DMM and affixing a known mass to the cone of the driver. I think I still have the required apparatus in a box somewhere. This seems much simpler in some ways. I will measure and post the results, though it may be a while before I can get around to it. How about using one or two of the Eminence Kappa 15C per side instead? I have two, and buying a pair more is relatively inexpensive. Is there not some advantage to using two and a compression chamber/front chamber rather than a single large driver? Again maximum SPL is not a priority relative to sound quality at more reasonable volumes. The venue is not a nightclub, and the emphasis will be on having the deep bass there in the same way that a critical listener would want a sub to integrate with his mains in a home setting.
ticknpop: Based on the drawings posted by maxolini, the Berthas with extension look to have around a 130 cubic foot volume each. Two would be 260 cubic feet. The volume that I have available is around 480 cubic feet. While I'm sure that the two Berthas would sound good, I would need to build a half height Bertha with extensions. I feel like I can probably build a stage with a couple of straight horns built into it, or maybe horns with one bend, much more easily than a pair of W cabs. Also, will a pair of Berthas with extensions do 20 HZ?
I think the single Bertha was good to roughly 30hz. It’s not the cubic feet, its the mouth area that counts. The standard 8 foot mouth Bertha 3.5 x 8 = 28 sq feet. The double stacked 10 mouth version is 3.5 x 10 x 2 = 70 sq feet mouth. Horn calculator for a hyperbolic expansion horn will tell you the cutoff. The RLA 3000 controller / crossover bandpass limited the low end to 30hz at 12 db/octave. You don’t want to overdrive the horns below the cutoff, it eats drivers. you will not miss the last 10hz. You could get lower with big reflex boxes and the correct drivers, but you won’t get the dynamics of the bass horn.
Did Richard tell me he’d done or was hoping to build a pair of straight concrete bass horns on Long island or am I dreaming? (It was almost 40 years ago). If you can do a straight horn with as big a mouth as possible would be pretty dam good. Hyperbolic is the fastest expansion rate to a given cutoff, but has higher distortion in the top end of its bandpass. The Bertha high pass cutoff was 100hz /18db octave. If you have room for an exponential expansion the HF distortion is lower.
in your case figure out what the biggest mouth you can do at the front of the stage.
then figure out how much depth you would need for exponential and hyperbolic expansions to build the horns. either mouth area or depth will be your limiting factor. Don’t forget the space for the rear chamber and service access. Don’t get too obsessed about 20hz ( I have 2 JL Audio F212v2 at home - they go low) the dynamics of really large mouth bass horns is still impressive. Multiple reflex boxes with lots of power for stadiums is good too, but not as effortless as big horns to me.
Did Richard tell me he’d done or was hoping to build a pair of straight concrete bass horns on Long island or am I dreaming? (It was almost 40 years ago). If you can do a straight horn with as big a mouth as possible would be pretty dam good. Hyperbolic is the fastest expansion rate to a given cutoff, but has higher distortion in the top end of its bandpass. The Bertha high pass cutoff was 100hz /18db octave. If you have room for an exponential expansion the HF distortion is lower.
in your case figure out what the biggest mouth you can do at the front of the stage.
then figure out how much depth you would need for exponential and hyperbolic expansions to build the horns. either mouth area or depth will be your limiting factor. Don’t forget the space for the rear chamber and service access. Don’t get too obsessed about 20hz ( I have 2 JL Audio F212v2 at home - they go low) the dynamics of really large mouth bass horns is still impressive. Multiple reflex boxes with lots of power for stadiums is good too, but not as effortless as big horns to me.
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Speaking of watch the processor settings to take care of the drivers , it was tick pop or somebody who wrote that the drivers used in the original Bertha's was custom made by eminence??
And that one time they swapped the drivers with some JBL's and some other brand can't recall ,and the drivers were shredded to pieces in less than 6 hours.
I asked what failure and it was the cone broken.
So I guess the custom drivers had a very stiff or different material cone? Or just plain a stronger motor? (Higher BL)
Well just some food for thought regarding this project.
4 18ds115-8 will be forgiving unless you use 20k bridged amps on each cab and be reckless on the DSP 😁
And that one time they swapped the drivers with some JBL's and some other brand can't recall ,and the drivers were shredded to pieces in less than 6 hours.
I asked what failure and it was the cone broken.
So I guess the custom drivers had a very stiff or different material cone? Or just plain a stronger motor? (Higher BL)
Well just some food for thought regarding this project.
4 18ds115-8 will be forgiving unless you use 20k bridged amps on each cab and be reckless on the DSP 😁
It was Celestion and JBLs that didn’t survive 6 hours in a Bertha. EAW may have used RCF in their 882 and Richard used a custom Eminence. I’m sure their are experts on this site who can advise on modern drivers once you have some horn size data.
Not making fun and I wish to be there when those cabs was deployed,but those old drivers only had 6-8mm xmax at the time , hornresp wasn't there at the time, paper pencil and calculator.
Horn plans was shown at least from Internet , if that is not right,hope that somebody can post the original ones.
And yes here ,
Are people who know their stuff from 30 ,40 years audio wise.
Horn plans was shown at least from Internet , if that is not right,hope that somebody can post the original ones.
And yes here ,
Are people who know their stuff from 30 ,40 years audio wise.
Yes better drivers today with higher x max, but the whole point of using a horn is to reduce driver excursion for a given SPL level. You need higher xmax for reflex/sealed box to get high SPL at low frequencies. Intermodulation distortion increases with increased cone travel. Paul Klipch published that 50/60 years ago in the ” Dope from Hope” papers he authored.
There’s often no room for a proper bass horn ( and who sells one?) so lets put 10kw of switchmode power into a lot of higher xmax drivers with toaster wire for voice coils to handle the power it takes to compensate for small box. Then use dsp to compensate for the small box volume, manage driver excursion, low end cutoff, etc - it works. But I like really big bass horns……
There’s often no room for a proper bass horn ( and who sells one?) so lets put 10kw of switchmode power into a lot of higher xmax drivers with toaster wire for voice coils to handle the power it takes to compensate for small box. Then use dsp to compensate for the small box volume, manage driver excursion, low end cutoff, etc - it works. But I like really big bass horns……
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My clueless idea is using much bigger cone area in not so small sealed boxes, yes lots of Xmax SI HS24 has 38mm capability(100mmP~P)you probably wouldnt need a bazillion watts too dig very deep into the low teens, with a 6 driver array its like nearly 2000"2 Sd, only take up approximately 100cf space total and you'd have the ability to move them around to help combat room nulls.
Horns to get this low would be absolutely massive and be a nightmare to make adjustment if it doesn't work as planned
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Yes your never going to get a 20 hz or less horn to fit anywhere, so your idea is best. At work in our 1500 sq foot workshop for big power supplies I use 8 reflex JBL 18 because If I put a Bertha in we have no room to work. Also 4 of 12 inch 2202, and 4 of JBL 2395/2441 horns and 2405 - lots of old school JBL - I was playing Erika Badhu pretty loud yesterday
I haven't used Hornresp for years, but have started to re-familiarize myself with it. I think I get some of it, but I haven't worked out how to vary the front and back chambers, or how to use a compression chamber with more than one driver feeding it. Because I don't have the T/S parameters for my 18 inch drivers, for anyone who feels like giving this a go, please feel free to use the driver or drivers of your choice.
The available volume is 20' X 12' X 2.5' which is 600 cubic feet. The available horn mouth opening is 20' X 2.5', for a total area of 50 square feet (4.645 square metres). This volume and mouth area would ideally be split into two in order to make two horns, but if one horn is better, that is fine as well. If it is one horn, I would like the opening to be centered on the stage face. I am not opposed to the horns (or horn) having bends. -3DB points of 20 and 60 Hertz would be ideal. Please see my attached drawing, and the reposted drawing and photos originally posted by AllenB, for more detail. SQ rather than SPL is the priority, so there is no need for nightclub level output.
The bottom rectangle is the available mouth area. The available horn length for a straight horn is 12' (3.65M), but I am not adverse to a bend/fold if it will help hit my target frequency range cleanly.
This would appear to substantially increase the overall length of the horn by using the walls and the mouth of the other horn to do so.
Both of the two photos above show horns that seem to be intended to cover a much larger range than my desired 20-60 Hertz, which would make the curved portion more of a requirement.
You had a look into the LAB horn?
With hornresp you are on the right path With your limited range you just need anough lenght and mouth area. Use a standard ration and fold it up.
But when your goal is ultimate sound quality you should look into double bass array (DBA). You think a lot about how to produce these low frequencies but you totally forget about the room! When you build your horn you can't move it - you have a fixed position of your mouth. But POSITION in the room is everything in low frequency reproduction.
I would do plenty of measurements in the room before even thinking about such a project to be sure the planned position of the horn mouth is fitting and a good idea.
And - do you REALLY want 20Hz for live music/DJ? Or what is the purpose? There are no 20Hz with live bands, it's just low frequency noise of moving microphones etc. With electronic music you could use the extended FR when you especially write/perform for it.
But to be honest 20Hz are mostly explosions and dino footsteps for home cinema ;-).
My reference listening speaker for mastering audio goes down to 20Hz (and below) - which is cool to get the higher frequencies right and detect mistakes from mixdown and rumble during the recording. And watching movies ;-)
With hornresp you are on the right path With your limited range you just need anough lenght and mouth area. Use a standard ration and fold it up.
But when your goal is ultimate sound quality you should look into double bass array (DBA). You think a lot about how to produce these low frequencies but you totally forget about the room! When you build your horn you can't move it - you have a fixed position of your mouth. But POSITION in the room is everything in low frequency reproduction.
I would do plenty of measurements in the room before even thinking about such a project to be sure the planned position of the horn mouth is fitting and a good idea.
And - do you REALLY want 20Hz for live music/DJ? Or what is the purpose? There are no 20Hz with live bands, it's just low frequency noise of moving microphones etc. With electronic music you could use the extended FR when you especially write/perform for it.
But to be honest 20Hz are mostly explosions and dino footsteps for home cinema ;-).
My reference listening speaker for mastering audio goes down to 20Hz (and below) - which is cool to get the higher frequencies right and detect mistakes from mixdown and rumble during the recording. And watching movies ;-)
and let's not forget the fact that there's a stage going over this horn, playback is one thing but live mic's are another.
and i for one can't imagine what it will take to isolate the stage floor from the sub.
and i for one can't imagine what it will take to isolate the stage floor from the sub.
Ideally they would be in the same plane as the main speakers - phase/time delay , but the ear is not as sensitive to LF phase as it is to midrange wavelengths.
the Japanese pictures - the big multi cell crosses over at least 300 hz , likely higher
and the split section mid horn 600 hz or more ( that horn isn’t a good one).
I’d really like to see a low/ mid horn with both systems down to to the 100z area Or lower.
maybe they blend OK back a distance.
some early Western Electric horns. The WE 555
in the middle 3 horns went low for dome driver
the Japanese pictures - the big multi cell crosses over at least 300 hz , likely higher
and the split section mid horn 600 hz or more ( that horn isn’t a good one).
I’d really like to see a low/ mid horn with both systems down to to the 100z area Or lower.
maybe they blend OK back a distance.
some early Western Electric horns. The WE 555
in the middle 3 horns went low for dome driver
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Its hard to articulate this point effectively but in live sound high output capability is a key requirement for fidelity, there is far less control of the level of playback in comparison to recorded music. This is because of the acoustic sound of the band that you can't turn down and the much greater dynamics. I tend towards extreme over provisioning of the FOH system, on many occasions this has got me out of difficult situations where the gig has turned out to be different to what was anticipated. This kind of thinking would make be cautious about not building much more output capability into a major project such as this than you think you need. After all if the woofers are moving a small faction of xmax they are likely to be more linear anyway....
IamJF: Sorry about the delayed reply. I figured it was time to get to know Hornresp better after a long absence. I'll post my sims using Eminence Lab15s shortly. I will probably end up with two horns that are good to 25-30Hz. The lack of flexibility that is the case with built in horns is definitely a concern, and I will try to figure out the best place to terminate the horns in the room. Ideally, the horns would be part of the stage so as to kill two birds with one stone, but there is some placement flexibility as they could also be built into raised booth seating, as well as run down a wall and then out. Bands will be a small part of business, and the main system (or a secondary system) will be able to take care of that requirement without the horn sub. It will be mostly DJs, but it will not be a nightclub. A listening bar/lounge is more the goal. Sound quality is the priority and not SPL. The main system will likely be a pair of Klipsch Jubilee. Ideally it will be like a big listening room in an audiophiles home.
This looks like an interesting PA setup, but isn't what I'm looking for. If I was on Fantasy Island, and could ask Mr. Roarke for my ideal system, I would ask for a point source capable of 20 to 20000 Hz. The Klipsch Jubilee, with DSP, covers 340 Hz and up with one horn and is effectively a point source in that range. A MEH version of the K402 can go lower still.