Corner-loaded bass horn designs other than Khorn?

[Lime Twig]

Tonnes of info here for me to mull over, thanks.

Since I will be using my La Scalas for mid-bass, that's already a known quantity for me. I already know I like the sound of these horns for midbass.

I take your point that a Bertha style sub is not the way to go since my room is too small. (btw, it's 35' long x 20' across with 16' ceilings). Here's a shot from close to the wall looking across the dancefloor:

You can see the hybrid LS tops I built in the pic above. Here's a shot looking the other direction, showing the normal LS:

The thing I don't understand is what you mean when you say conventional horns sound like they have no bass up close. I mean, I know the basics, I understand why a large format horn like a Bertha would not have much bass up close, but there is so much variety in folded horns. The person I've been getting the most advice from has two sets of enormous J-scoops for example. One pair has plenty of bass up close, the others do not, owing to differences in horn length and throat size.

Some side notes: the RLA bins I was referring to were his Bertha designs from the Paradise Garage. I don't know anything about his use of the Olsons.

[djk]

"The thing I don't understand is what you mean when you say conventional horns sound like they have no bass up close. I mean, I know the basics, I understand why a large format horn like a Bertha would not have much bass up close, but there is so much variety in folded horns. The person I've been getting the most advice from has two sets of enormous J-scoops for example. One pair has plenty of bass up close, the others do not, owing to differences in horn length and throat size."

You are not discriminating between horn designs. Scoops have bass up close because they are not horns per se. Same thing with the tapped horns. It it the true front-load horn with a sealed back chamber (Klipschorn, Jubilee, MCM, EV TL4050, EV TL5050) that seem to have no bass on the dance floor. The reference cited from Olson is the only explanation (that makes sense) I have ever read on this phenomenon. Also, Dr Bruce Edgar notes this same behavior in his horns, and has done various treatments like facing the horn mouth straight down at the floor, and using some sort of sandbox device.

"Some side notes: the RLA bins I was referring to were his Bertha designs from the Paradise Garage. I don't know anything about his use of the Olsons. "

The "Big Bertha's" were made by EAW (BH882 with custom mouth extenders) and AFAIK were not available until the later 80s, previous to this (Studio 54 era) he used the Olson bins, a design dating back to the mid 30s.

[Lime Twig]

You are not discriminating between horn designs. Scoops have bass up close because they are not horns per se. Same thing with the tapped horns. It it the true front-load horn with a sealed back chamber (Klipschorn, Jubilee, MCM, EV TL4050, EV TL5050) that seem to have no bass on the dance floor. The reference cited from Olson is the only explanation (that makes sense) I have ever read on this phenomenon. Also, Dr Bruce Edgar notes this same behavior in his horns, and has done various treatments like facing the horn mouth straight down at the floor, and using some sort of sandbox device.

I wouldn't disagree with the physics: you're quite right to point out that a low frequency wave simply will not be audible right in front of a large horn, (and it's quite obvious that you know much more about this that I do!) what I'm reacting to is the idea that for this reason, conventional horns are inappropriate for dancefloors! That just seems to fly in the face of so many world-class club systems! Richard Long's venerated Berthas at the Paradise Garage, 54 and all are the stuff of legend. And even if Ministry of Sound has recently upgraded their Berthas to ported ASXs doesn't mean that the originals didn't sound great throughout the entire '90s!

The "Big Bertha's" were made by EAW (BH882 with custom mouth extenders) and AFAIK were not available until the later 80s, previous to this (Studio 54 era) he used the Olson bins, a design dating back to the mid 30s.

Interesting, I didn't know RLAs cabs were built by EAW. I have some doubts that the RLA Berthas were only a product of the late 80s however. In stories about the Garage system they are the constant fixture and the Garage closed in '87. Here's a sales brochure (no date, sadly) showing the stack with the Berthas and Levan extention.

[djk]

I would have to check my early EAW notebooks, it may have been as early as 1984 or so.

You have probably read this already:

soundmanshorty

01-10-2003, 12:52 AM

Richard
did some work with Kenton Forsyhte on box designs - Kenton is the
President of EAW. But they came up with some interesting box designs
together (one system that Richard had EAW build the boxes for was the
NYC Palladium this was completly all built & design by Richard and
Kenton, so EAW built all the cabnets as well as a couple other jobs) but
in those days EAW did do some work for Richard so the BH 882iP is the
Birtha & EAW used to make the extension as well for the 882iP -
& (EAW does build this box for me still with the extension if
requested) -

so this is the Birtha they just gave it an EAW model # which became the
BH 882iP but the box is basically the same the only diff is the throat
& there were 3 diff throats that Richard used. So this is one of the
3 throats therefor it is still a Birtha. 2, The marterial of wood EAW
uses for the throat is diff internally then the wood EAW uses
externally, When Richard built them with Curtis or Chuck they used the
same material wood thruout the box internally and externally. 3, The
third difference was the trap door in the back the EAW version has 2
trap doors 1 for each driver, Richard made one large trap door for
servicing the box. These are the only differences between the EAW
version of the Birtha or the RLA box besides what throat Richard would
spec to use for a job.

Now the EAW version is extreamly well built and really performs well
and it is a 2 Ohm box. In the 80`s Richard did`nt like to make his boxes
2 ohm boxes as amps became more powerful so he would build them as 4
ohm boxes,

I personally like 2 ohm bass myself but not many amps built today can
really do 2 ohm bass. In my opinion the only 2 amps that can really do 2
ohm sub bass is BGW which are Class AB Descrete technology & are
still made & i love or Crest pro series which is very good too,
these are the only 2 amps that really put out bass in a 2 ohm load all
night long without failing on you or get tired sounding.



Another thing, If your familiar with that EAW Avalon sub bass box with
that dbl 12in drivers, this box is a downsized version of the RLA
Puissance, the RLA box had 2 - 15s. EAW redesigned the box for 2-12s to
sell with there Avalon series and there big Avalon top is an upsized
modified version of the another RLA top box.

www.systemsbyshorty.com

---

soundmanshorty

01-10-2003, 02:56 PM

Ok
in the above posts i listed some info on the Birtha and i wanted to list
why the extension was used for the Birtha. The extension helped the
boxes pattern control it also allowed the box to play 3 DB louder and
drop the box down 1 octive.

But one of the main reasons they used the Levan extension was because
they found that the wave form was not completing at the mouth of the
Birtha on its own, so they used the extension to add additional footage
to the horn so the waveform would complete itself at the mouth of this
cabnet.

Once the extension was added the performance & output of this box
is unbelievable and unbeatable. This boxes output with a BGW 750 or a
Crown PSA 2 is amazing and can out do these newer made boxes with twice
the power it`s really an amazing box that Richard came up with.

www.systemsbyshorty.com

I have a shot of the original Studio 54 system (circa 1977) in an old computer that doesn't run. I'll have to see if I can recover the hard drive.

Have fun with your venture!

[djk]

Plans for Big Bertha (for crazy people):

http://www.dancetech.com/aa_dt_new/pa/plans/EAW_BH882.jpg

http://www.dancetech.com/aa_dt_new/pa/plans/bh882p_2d.pdf

Sorry, the link for the mouth extender is dead.

[Lime Twig]

Ok
in the above posts i listed some info on the Birtha and i wanted to list
why the extension was used for the Birtha. The extension helped the
boxes pattern control it also allowed the box to play 3 DB louder and
drop the box down 1 octive.

But one of the main reasons they used the Levan extension was because
they found that the wave form was not completing at the mouth of the
Birtha on its own, so they used the extension to add additional footage
to the horn so the waveform would complete itself at the mouth of this
cabnet.

Once the extension was added the performance & output of this box
is unbelievable and unbeatable. This boxes output with a BGW 750 or a
Crown PSA 2 is amazing and can out do these newer made boxes with twice
the power it`s really an amazing box that Richard came up with.

djk, thanks so much for the info. I hadn't read that old post of Shorty's and it's really helpful.

I'm wondering about our conversation earlier about hearing low end in front of a big sub and what Shorty's comments above say about that:

"they used the Levan extension was because
they found that the wave form was not completing at the mouth"

Now, I understand that a 30Hz wave is somewhere around 34' long. So, it makes sense to me why a bass horn has to be big, why you need a big mouth, and also why you simply couldn't hear it in front of the speaker. What is this issue of having the wave front "complete" at the mouth though? You said something earlier about how horns translate (what was it?) pressure to velocity? Do waveforms behave differently INSIDE the horn? I assume there must be something of this order going on since we CAN hear 30Hz sounds right on front of a direct radiator.

[Lime Twig]

Interestingly, in my digging around the Wave Music forum archives, I found this later post from Shorty:

"the EAW 882 horns never kicked or delivered what the real berthas /
levans did, i remebered hearing the system at Palladium which EAW made
everything in that system for Richard, Richard designed that system with
Kenneth Forsyth of EAW and EAW manufactured all the cabinets. All the
other rooms with these EAW 882s he used it didnt really do anything
compared to his earlier systems or kicked like other berthas ive heard
before that werent 882s. Nice find online, (referring to the same 882 drawings posted earlier) thou alot isnt on those plans" (from 2006)

[DrWho]

For in close bass, I don't like conventional horns, they feel like they have no bass. A tapped horn is not actually a horn in the range that we want it to work in, and does not suffer like a conventional horn does.

I'm not sure I buy the argument you gave about the velocity and pressure wave phase shifting after the mouth of the horn...

I also think the reason conventional bass horns feel like they have no bass up front has more to do with the fact that large bass horns are often used in large speaker clusters where the listener is naturally going to be away from the midbass/midrange energy. Our ears use higher frequency cues to aid our perception of low frequency energy.

There is also the issue of far-field polars versus nearfield polars when multiple cabinets are being used.

[djk]

Do you understand what Olson was trying to say?

I'm not entirely sure that I completely understand his explanation, but it sounds like he knows what he is talking about (he also has a masters in acoustics and a doctorate in physics).

"I also think the reason conventional bass horns feel like they have no
bass up front has more to do with the fact that large bass horns are
often used in large speaker clusters where the listener is naturally
going to be away from the midbass/midrange energy. Our ears use higher
frequency cues to aid our perception of low frequency energy."

That sounds good, but it doesn't make sense to me either. I can have a big stack of direct radiators replace a similar size stack of big horns, and there is bass up close with the direct radiators, and not with the horns.

This stack originally had 50hz Fc bass horns, four 15s driving a 1728 square inch mouth (the MCM is 1472.6 square inch mouth) , they had fantastic bass in the back of the room, and nothing on the dance floor.The horn bass units were the same height and width as the DR units, but deeper. The MF and HF were the same.

[DrWho]

I couldn't find Olson's original comments after searching for several minutes through the other links presented, but maybe I was skimming too fast. I guess all i can say is that I've never experienced this outdoors with all sorts of bass horns. Has all your experience been indoors? I've often wondered what the effects of modal behavior would be on a horn since it is a passive device and the horn model assumes free air after the mouth, which isn't true when you've got reflections coming back into the mouth...

[djk]

However, horns can sound like they have no bass right up close.

Up close the phase angle between the pressure and the particle velocity in a
spherical sound wave is 90*, this corrects itself at at a distance as it
becomes a plane wave.

See Olson, section 1.5, Fig. 1.2, 1.3

----------------------------------------------------------

• Posted by

djk (M ) on February 16, 2004 at 01:02:13

In Reply to: Re: Voice of dissent - don't have book - what
distances are "typcial"?<nt> posted by freddyi on February
15, 2004 at 16:21:55:

The charts show phase angle vs distance
and particle velocity
vs distance. Distance in both cases expressed as (2Pi/W)D, wavelength
and distance assumed to be in feet.

For a 10* difference at 40hz it works out to like 22.5 feet.

For a 30* difference at 40hz it works out to like 8.2 feet.

The ratio of the absolute magnitude of the particle velocity to the
pressure starts to flatten out beyond 8.2 feet for 40hz.

The very high losses at low frequencies would indicate that mic
in the mouth is meaningless, but should be measured at a great distance
and use inverse square to find the 1M spl (which is standard).

I've had people come up to me and tell me they couldn't hear
anything coming out of a cabinet, it must be blown.

--------------------------------------

[Don Richard]

I think that one reason for direct radiators sounding louder than horns are that horns have less distortion than direct radiators. Some pro sound subs are actually held in high esteem for creating this distortion. One of the worst sounding shows I attended recently had 6 2-18" JBL subs, stacked 3 high on either side of the stage. Loud but lousy, mostly 60-100 Hz output.

Another reason direct radiator subs can sound louder is boundary reinforcement/cancellation. At low freqs the sound wave is large relative to the size of the cabinet. This results in the sound wave diffracting around the cabinet 360 degrees. The small size of the tapped "horns" and bandpass horns results in the same situation as with acoustically small direct radiators. Sufficiently large horns are nearly immune from such boundary effects.

[djk]

"I think that one reason for direct radiators sounding louder than horns
are that horns have less distortion than direct radiators."

Not true of my PPSL designs.

Side-by-side, my PPSL have less distortion than horns.They are so clean they sound 'funny' at first listen (lack of distortion).

I suggest anyone that really wants to know, just buy a cheap sheet of whatever, a cheap pair of drivers (must be the same model number), and try it.

As to whether or not Olson is correct, I don't care. Inside, or outdoors, the direct radiators seem to have more bass on the dance floor area.

[CECAA850]

Side-by-side, my PPSL have less distortion than horns.They are so clean they sound 'funny' at first listen (lack of distortion.

I suggest anyone that really wants to know, just buy a cheap sheet of whatever, a cheap pair of drivers (must be the same model number), and try it.

Any pics, drawings or literature you can post links to? I'm intrigued. I can't wrap my head around a push pull slot loaded sub without a little help.

[Don Richard]

Not true of my PPSL designs.

Side-by-side, my PPSL have less distortion than horns.They are so clean they sound 'funny' at first listen (lack of distortion.

PPSL _ Push Pull Slot Loaded ?

If so, is it a direct radiator or a bandpass box? Bandspass subs do have low harmonic distortion but the cones do not radiate directly.

There are push-pull horn loaded subs that feature low distortion, the Pi 12 being one.

[djk]

"Any pics, drawings or literature you can post links to? I'm intrigued.
I can't wrap my head around a push pull slot loaded sub without a
little help."

Here is the basic idea:

It may be implemented as sealed, vented, di-pole, etc.

"If so, is it a direct radiator or a bandpass box?"

Because the front cavity is so small, its resonance lies outside of the range we would normally run it in. As such, I just model it as a direct radiator, not a bandpass.

"There
are push-pull horn loaded subs that feature low distortion, the Pi 12
being one."

Where do you think Wayne got the idea? You can go through the archives at Audio Asylum (2003 time frame). Wayne did a lot of work with this idea, he also found out that the PP gave inexpensive drivers better performance than expensive drivers with shorting rings in the magnets (to reduce distortion).

Jon Risch (Peavey) found out that expensive drivers with shorting rings also benifited from PP mounting, although not as much as cheaper drivers did.

Wayne P and Tom D were going back-and-forth about push-pull mounting on one of the pro sound forums. Shortly after that we saw some push-pull models from Danley.

Someone did a dumax test on a pair of inexpensive 8s and found that PP mounting allowed for about 3dB more maximum output vs conventional mounting of the same drivers, the BL curves were symetrical . The Danley SPUD uses PP 8s.

[CECAA850]

Are the drivers wired out of phase?

[PrestonTom]

Are the drivers wired out of phase?

Electrically, they are out of phase, mechanically they are in phase (IOW, they are pushing air in unison)

[CECAA850]

Are the drivers wired out of phase?

Electrically, they are out of phase, mechanically they are in phase (IOW, they are pushing air in unison)

If they're electrically out of phase, they're mechanically out of phase BUT it appears they would be acousticaly in phase (pushing air in unison as you stated). It's an interesting concept. I've never heard one nor can I figure out why this configuration would lend itself to lower distortion than a normal ported sub.

[Fjd]

I believe that harmonic distortion is reduced because the variations in each of the driver’s cones, spiders, and suspension are cancelled out because one driver will be inversely proportional to the other.