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miking a Fender Bassman cabinet Dynamic Microphones
Old 14th May 2018
  #1
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miking a Fender Bassman cabinet

A question about miking a vintage 4 x 12 Fender Bassman cabinet ( I believe it's called a pyramid cab....guess why)

Typically it's used with a removable frame with somewhat-protective grille cloth (pic 3) , which sits just inside the outer edge (you can see the black velcro tags in the first pic), but for recording I'd prefer to remove this to avoid rattles.

I'm wondering if the pyramidal shape serves to focus the 4 bass wavefronts centrally, and whether a mic would be best placed somewhere along that central axis line, where all wavefronts would 'converge', as if it were a lens ? If so, at what sort of mic distance ?

Or would you just mic a single driver, as per a conventional 2 x 10 guitar amp cabinet ?

Recommended mic(s) for this job ?
Attached Thumbnails
miking a Fender Bassman cabinet-bassman-cab-1.jpg   miking a Fender Bassman cabinet-bassman-cab-2.jpg   miking a Fender Bassman cabinet-bassman-cab-3.jpg  

Last edited by studer58; 14th May 2018 at 12:36 PM..
Old 15th May 2018
  #2
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wow!

for use with guitar, i'd take an sm57 and a md421 on top and bottom speakers (or swap one for a ribbon mic) - or a single u67 is almost always great!

single mic such as md421, re20, m88 if used with bass - or a u47fet wouldn't hurt either...
Old 16th May 2018
  #3
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jnorman's Avatar
Yep, mic a single cone with a 421.
Old 16th May 2018
  #4
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jnorman's Avatar
It’s called a pyramid cab because it took 10000 slaves 20 years to build it.
Old 16th May 2018
  #5
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tourtelot's Avatar
Wow, the mounting of those speakers looks like somebody's "good idea." Never seen that. Anyone with for-sure knowledge of the whys and where-fors?

Live or studio? Bass or guitar or?

I would guess that I would have to listen to hear what the actual sound was and go from there but for bass, the Sennheiser 421 or the EV RE20 seem like a good start.

For guitar, I might have to go with an SM57 on one cone (and maybe a good LDC a bit farther out.)

Hope you have a bit of time to listen before the gig.

D.
Old 16th May 2018
  #6
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Quote:
Originally Posted by tourtelot View Post
Wow, the mounting of those speakers looks like somebody's "good idea." Never seen that. Anyone with for-sure knowledge of the whys and where-fors?

Live or studio? Bass or guitar or?

I would guess that I would have to listen to hear what the actual sound was and go from there but for bass, the Sennheiser 421 or the EV RE20 seem like a good start.

For guitar, I might have to go with an SM57 on one cone (and maybe a good LDC a bit farther out.)

Hope you have a bit of time to listen before the gig.

D.
Definitely a legitimate Fender 'product'....not someone's hobbyist afterthought rebuild. However since the idea didn't persist beyond the late 60's, I guess it didn't excite imaginations, and it's a beast to lift ! It'll be for a studio session, with Fender Jazz Bass guitar.

I had the misfortune to be required to rewire the cabinet, and can report that each driver is partially enclosed in its own quadrant box...or rather partial baffles, as there are plenty of air spaces between them. There's certainly no attempt at horn loading or any masterwork of carpentry involved back there out of sight !

My idea about the 'central axial line outwards from the centre' was that there might be some additive effect to be gained from the contribution of 4 drivers all "beaming in" to a point...but I'm guessing there will be both additive and subtractive phasing at various points along that line...so it will be very much a case of trial and error.

Thank you for your suggestions...there should be enough time for experimenting before recording
Old 16th May 2018
  #7
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Quote:
Originally Posted by jnorman View Post
It’s called a pyramid cab because it took 10000 slaves 20 years to build it.
.....and a goodly proportion of those numbers to haul it up the stairs to the gig !
Old 16th May 2018
  #8
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i remember reading an interview with tom dowd where he mentioned putting mics (ev?) between the 4 speakers, although on different stacks (marshall?) when recording cream live.

for use with bass you might try to put one speaker out of phase: could get you a somewhat different pattern of the whole cabinet and might be 'interesting' with a fig8 in the right spot (or just a huge mess and a very bad idea...)
Old 16th May 2018
  #9
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Fender Bassmen were v pop for Gtr in the 60s before the advent of big PA
An insensitive Ribbon like a STC 4033a would be a good central plant with some air around it
Modern Ampegs sound good and don't weigh like the Titanic thanks to class D
Old 16th May 2018
  #10
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Yes a little web searching turns up that the cabinet itself was regarded as a poor enclosure... which soon became rattle-y and was prone to falling apart...which tallies with the glued and stapled assembly given to it !

The amp head was built from about '68 onwards, and the cabinet seems to have only lived from 1972-77, before being discontinued.

Also not much loved for a middle heavy sound from the 30 watt speakers originally installed...so more likely a better candidate as a guitar rather than a bass amp ? However the video below implies that the odd speaker array would serve to disperse the mids moreso than a typical flat infinite baffle...again, more useful for electric guitar perhaps than bass

The Bassman 100 head, as Roger mentions, seems to have a lot of flexibility built into the lead channel, as this video shows: https://www.youtube.com/watch?v=_4B2sul6w-Y

Anyway...a historical oddity, but at least you know a little more about it now, if you should strike one at a future gig or recording session.

I'd guess now that miking an individual speaker might be the best approach, as many of you have suggested here already
Old 16th May 2018
  #11
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emrr's Avatar
I've had good success at the point the middle two focus together with bass. I have a Sunn 6 x 10" cabinet that's similar, two vertical stacks that angle in toward each other, and there's also something additive in the very bottom at that focal point.
Old 16th May 2018
  #12
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Quote:
Originally Posted by emrr View Post
I've had good success at the point the middle two focus together with bass. I have a Sunn 6 x 10" cabinet that's similar, two vertical stacks that angle in toward each other, and there's also something additive in the very bottom at that focal point.
Good to know...I'll try that...thanks Doug !
Old 16th May 2018
  #13
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tourtelot's Avatar
A little OT but I used to tour with a club band who had a bass player who had an Ampeg SVT rig. Eight 10" speakers in the cabinet and that cabinet in a large-assed road case.

My buddy and I did it all; mixed FOH, set up band gear and drove the truck, Oh those were the days.

Anyway, whenever he and I would encounter a set of stairs, that goddam SVT cabinet would make one of those trips, the one down the stairs, by being set at the top and kicked over to slide down the stairs.

Gotta say, it made it through the whole tour in more-or-less working order.

D.
Old 13th February 2019
  #14
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I've been recording this same bass cabinet/tube amp (Fender Bassman 135) combo today with a LF dynamic mic: Avantone Pro Mondo
Avantone Pro
Avantone Pro MONDO | RecordingHacks.com

The mic sounds quite impressive..I'm looking forward to using it on kick drum, and perhaps tuba with a wind orchestra soon also.
I'm sure the 'red sports car' look will appeal to drummers ! It's my mid-life crisis mic...couldn't afford the sports car so the mic stands in for it ....

Don't know how it would fare on double bass in an orchestral setting, the inbuilt 'aggressive' eq-ing might not suit that instrument as well as it does serious air-movers like electric bass cabinet or kick... and it may not have the necessary sensitivity to pick up playing nuances in the instrument like a condensor or ribbon mic can ?

Last edited by studer58; 4 weeks ago at 03:16 PM..
Old 13th February 2019
  #15
Gear Addict
Just a quick FWIW on the cabinet posted originally, from the eye of a speaker designer:

- There'll be some horn loading due to the shape of the baffle. I'd expect a bit of gain in the 1-300Hz region.
- The 2kHz+ range will have an interesting dispersion pattern - as each driver starts to "beam" up there, you'll have more of that range on-axis with the drivers, rather than on-axis with the cabinet (as you get with a typical 4x12")
- Since the rear of the cabinet isn't enclosed, you'll have the usual open-backed-cabinet interactions with the room.

In terms of micing the thing, you'll need to experiment. The treble is dispersed in weird ways, so moving the mic by a few inches will probably change the tonality. I'd recommend distant micing first, since the horn is part of the cabinet's sound.

If you don't get good results that way, I'd then look at close micing one of the cones.

A wild-card would be to put a mic (maybe an omni) riiiiiiight at the apex of the horn and see what that gets you. Probably a lot of low-mids and not much above 1kHz, but blending that with a close-mic'd cone would give interesting results.

Chris
Old 13th February 2019
  #16
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Quote:
Originally Posted by chris661 View Post
Just a quick FWIW on the cabinet posted originally, from the eye of a speaker designer:

- There'll be some horn loading due to the shape of the baffle. I'd expect a bit of gain in the 1-300Hz region.
- The 2kHz+ range will have an interesting dispersion pattern - as each driver starts to "beam" up there, you'll have more of that range on-axis with the drivers, rather than on-axis with the cabinet (as you get with a typical 4x12")
- Since the rear of the cabinet isn't enclosed, you'll have the usual open-backed-cabinet interactions with the room.

In terms of micing the thing, you'll need to experiment. The treble is dispersed in weird ways, so moving the mic by a few inches will probably change the tonality. I'd recommend distant micing first, since the horn is part of the cabinet's sound.

If you don't get good results that way, I'd then look at close micing one of the cones.

A wild-card would be to put a mic (maybe an omni) riiiiiiight at the apex of the horn and see what that gets you. Probably a lot of low-mids and not much above 1kHz, but blending that with a close-mic'd cone would give interesting results.

Chris
Thanks Chris, that gives me a few directions to try in terms of trial, error and experimentation BTW the rear of the cabinet is enclosed...see attached pics. However there are small air gaps in the front pyramid baffle face-joint edges of around 8mm, so the cabinet is not fully sealed (in the front (speakers) face at least)

I believe the design didn't have a long life in the product lineup, maybe a couple of years or a little more ? Reports from users in the bass forums explain why...the cabinet wasn't well made and was unable to stand up to the rigours of touring and being moved often, and the pyramid faces began to flex with the weight/leverage of the drivers.

The boxes tended to self-destruct and required constant attention and reinforcement. I guess the weight, size and construction complexity eventually worked against the design...in favour of simpler cabinet constructions ?
Attached Thumbnails
miking a Fender Bassman cabinet-img_0437.jpg   miking a Fender Bassman cabinet-img_0442.jpg  
Old 14th February 2019
  #17
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This comment isn't specific to that cabinet (sorry!) but I've had great luck with omni condensers on bass amps in the past. The lack of proximity effect keeps the lows clean, avoiding that tubby sound, and it captures a sort of "growling" sound that I really like, despite my inability to describe it well.
Old 14th February 2019
  #18
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Quote:
Originally Posted by Ebeowulf17 View Post
This comment isn't specific to that cabinet (sorry!) but I've had great luck with omni condensers on bass amps in the past. The lack of proximity effect keeps the lows clean, avoiding that tubby sound, and it captures a sort of "growling" sound that I really like, despite my inability to describe it well.
Yes that makes a lot of sense...instead of relying on dynamic/cardioid proximity effect, 'aggressive eq shaping' (have a look at most of the kick mic response plots: Shure 52, Sennheiser 602, AKG D112 etc) you have the native clean LF extension of an omni...I recall using a Behringer ECM8000 for that purpose many years ago and being quite surprised how good it sounded (once the hiss was rolled off) It did seem to pull in more of the cabinet's interaction with the room however, which is not necessarily desirable...but that's more a placement issue probably
Old 4 weeks ago
  #19
I agree with Doug

You should try to figure out where all the speakers converge and mike it there. It might be two feet out but so what? Aim the cab away from the drummer and use a direct box also.The latency on two feet is minimal. EQ the high end out of the cab mike and EQ the low end out of the direct. Mix together.

I did this with a bass player once who had two Kustom tuck and rolls with 15" JBLs that were set at an angle to each other. It was awesome.
Old 4 weeks ago
  #20
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Quote:
Originally Posted by chris661 View Post
Just a quick FWIW on the cabinet posted originally, from the eye of a speaker designer:

- There'll be some horn loading due to the shape of the baffle. I'd expect a bit of gain in the 1-300Hz region.
- The 2kHz+ range will have an interesting dispersion pattern - as each driver starts to "beam" up there, you'll have more of that range on-axis with the drivers, rather than on-axis with the cabinet (as you get with a typical 4x12")
- Since the rear of the cabinet isn't enclosed, you'll have the usual open-backed-cabinet interactions with the room.
How is this a horn, and how did you get all this just from looking at a picture of the box...?
Old 4 weeks ago
  #21
Gear Addict
Sam,

Definitions of "horn" will vary, but the loosest definition that applies to all horns is this - a pipe that expands in area towards the terminus.
You can argue about the old-school horn maths and how some modern HF horns don't really follow the old rules, but it's a long-winded argument and I have no interest in it. Horns expand towards the terminus, in the most basic sense. Any quarter/half-wave loading, directivity control, etc is all down to the designer.

In this case, the drivers are mounted part-way between the apex and terminus, but the concept holds. You might even call it a "tapped horn", although DSL currently have a patent on that. Their subwoofers should probably be called double-tapped, since the driver actually has two entry points into the horn.

Anyway.

With regards to how I can tell all these things from a picture, here's my reasoning:

- For one, I ran a quick simulation of 4x drivers, guestimated some dimensions and found the horn resulted in gain in the lower midrange, compared to a flat baffle. The dimensions will tie into which frequencies are affected, but the fact is that the horn shape will "focus" the sound a little.
This is the sort of thing that you can start to estimate in your head once you've designed, built and measured a few speakers.

- While I'm sure you know all about how the directivity of a cone driver varies with frequency, I'll fill in the gaps for those that don't:

If we assume (for now) that a cone driver has a perfectly rigid and massless cone, we can see that all of the cone will be radiating at all frequencies - the entire cone can follow the movement of the voicecoil perfectly. I'll discuss what happens when we remove that assumption later.

So, if the entire cone is radiating, that means that when the frequencies get high, the wavelengths become small compared to the cone.
As a result, we'll have interference when listen off-axis from the speaker - we get pressure waves coming from different places, which means there's a time-of-flight difference, resulting in phase difference, resulting in cancellations.

Go further off-axis, and the distance between the near edge and far edge of the cone becomes greater, which means the cancellations will start happening at a lower frequency.

Anecdotally, we can back this up - ever noticed how guitar amps sound incredibly harsh if you put your ear right in line with the speaker, but moving off to the side a few inches makes the sound more mellow?
That's it, you're experiencing the narrow dispersion of the 12" cone at frequencies above about 1kHz.


Now, let's take a look at the assumption we made earlier. We know for a fact that cones aren't massless, or perfectly rigid. That means they can bend.

How exactly the cones bend is a huge topic that I won't go into much. The good ones manage to do something very clever - they decouple the outer edge from the voice coil at high frequencies.
That means the edges of the cone aren't doing anything up there, which means your radiating area gets smaller, and you can have wider dispersion in the treble.
Other cones will try to stay very rigid, which means they'll ring like a bell at some high frequency - check out the response curves for an aluminium-coned midbass (something by Seas, for example).

The long story short on bendy cones is this - most drivers in the PA world have paper cones, which are quite flexible, but also quite well damped. They don't ring like a bell if you excite a high-frequency resonance.
That also means they do manage to reduce the high-frequency radiating area a little, which in turn means the off-axis response isn't as poor as you'd expect from a perfectly rigid cone, but the narrowing of dispersion in the high frequencies does still occur.


I hope that answers your questions, but if you have more, feel free.

Cheers,
Chris
Old 4 weeks ago
  #22
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i'd like to hear a folded horn, a la Klipsch La Scala domestic speaker, placed in the corner of a room...as an electric bass cabinet. I bet you'd get much clean low bass from that ?

I seem to recall the coupling of the driver to the air column was very efficient, meaning that you could get by with a smaller cone driver, less excursion, lower power amp...and thus overall much lower distortion. Efficiency was 105dB/watt at 1 metre. A portable transistor radio could drive it to deafening levels....and using a typical hifi amp the speaker could be cruising at 1 or 2 on the output dial !

That Klipsch sound always seemed effortless, at least in the bass region (a bit shouty in the mids)...though it tended to excite resonances in the turntables and tonearms of the LP record replay devices it was contemporaneous with

The Klipsch LaScala – Old School | TONEAudio MAGAZINE

La Scala Floorstanding Speakers | Klipsch
La Scala II Floorstanding Speakers | Klipsch

Last edited by studer58; 4 weeks ago at 05:14 PM..
Old 4 weeks ago
  #23
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Quote:
Originally Posted by chris661 View Post
Sam,

Definitions of "horn" will vary, but the loosest definition that applies to all horns is this - a pipe that expands in area towards the terminus.
Calling this a horn or claiming horn-like performance just because the center of the baffle tilts inwards is a stretch as far as I'm concerned.

Quote:
With regards to how I can tell all these things from a picture, here's my reasoning:

- For one, I ran a quick simulation of 4x drivers, guestimated some dimensions and found the horn resulted in gain in the lower midrange, compared to a flat baffle. The dimensions will tie into which frequencies are affected, but the fact is that the horn shape will "focus" the sound a little.
This is the sort of thing that you can start to estimate in your head once you've designed, built and measured a few speakers.
I have never been able to predict the sound/performance of a loudspeaker just by looking at it...especially when we don't even know the specifics of the components...never heard of any such thing.
Old 4 weeks ago
  #24
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Quote:
Originally Posted by studer58 View Post
i'd like to hear a folded horn, a la Klipsch La Scala domestic speaker, placed in the corner of a room...as an electric bass cabinet. I bet you'd get much clean low bass from that ?

I seem to recall the coupling of the driver to the air column was very efficient, meaning that you could get by with a smaller cone driver, less excursion, lower power amp...and thus overall much lower distortion. Efficiency was 105dB/watt at 1 metre. A portable transistor radio could drive it to deafening levels....and using a typical hifi amp the speaker could be cruising at 1 or 2 on the output dial !

That Klipsch sound always seemed effortless, at least in the bass region (a bit shouty in the mids)...though it tended to excite resonances in the turntables and tonearms of the LP record replay devices it was contemporaneous with

The Klipsch LaScala – Old School | TONEAudio MAGAZINE

La Scala Floorstanding Speakers | Klipsch
La Scala II Floorstanding Speakers | Klipsch
There are some very good reasons why almost nobody makes folded horns anymore...with modern efficient components and very high-power amplifiers there is no real advantage.

As a bass caba folded horn would probably suck...one of the bad things about folded horns is that horns will present a resonant, dispersive, and nonlinear wave propagation. They also tend to have limited bandwidth and unless the horn is very big or you load them in a corner the 'sweet-spot' is relatively small.
Old 3 weeks ago
  #25
Gear Addict
Quote:
Originally Posted by Samc View Post
Calling this a horn or claiming horn-like performance just because the center of the baffle tilts inwards is a stretch as far as I'm concerned.


I have never been able to predict the sound/performance of a loudspeaker just by looking at it...especially when we don't even know the specifics of the components...never heard of any such thing.
Sam, you're welcome to suggest another definition for a horn. The debate rages on. I've decided on the simplest approach although others will disagree.


Just because you can't do it, it doesn't mean it's not possible. Some people can look at a section of code and say exactly what it's going to do. Others can look at an engine and tell you roughly how much power it'll put out.
I can look at a cabinet, and I'll have a good idea of the physics at play, and how that will affect the sound.

Do you think the guys that design speakers for a living keep making prototypes until something works, or do you think, perhaps, there are ways of predicting the performance of a loudspeaker?

Chris
Old 3 weeks ago
  #26
Gear Addict
Quote:
Originally Posted by Samc View Post
There are some very good reasons why almost nobody makes folded horns anymore...with modern efficient components and very high-power amplifiers there is no real advantage.

As a bass caba folded horn would probably suck...one of the bad things about folded horns is that horns will present a resonant, dispersive, and nonlinear wave propagation. They also tend to have limited bandwidth and unless the horn is very big or you load them in a corner the 'sweet-spot' is relatively small.

Sam, what you've said here says to me you haven't experienced what horn-loaded subwoofers can actually do.

Take a look at Danley Sound Labs, and also read up on the Orthorn tapped horn. There's also the LAB Horn, which is a little long in the tooth but still a viable way of getting below 30Hz.

Folded horns are a way of using a bigger box to get more output from a given driver complement. That means you need less power (since you're driving fewer cones) to reach the same SPL.

Some of the most intense bass I've ever experienced was from folded horns - it was a case of your vision was always blurry, the frequency just changed.

I won't argue horns are the epitome of low-frequency reproduction, but they have more merit than you seem to think.

Chris

PS - Direct-radiating speakers (ported boxes etc) aren't even slightly efficient - the really high efficiency ones might reach 5% over a useful bandwidth.
Old 3 weeks ago
  #27
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Quote:
Originally Posted by chris661 View Post
Sam, what you've said here says to me you haven't experienced what horn-loaded subwoofers can actually do.

Take a look at Danley Sound Labs, and also read up on the Orthorn tapped horn. There's also the LAB Horn, which is a little long in the tooth but still a viable way of getting below 30Hz.

Folded horns are a way of using a bigger box to get more output from a given driver complement. That means you need less power (since you're driving fewer cones) to reach the same SPL.

Some of the most intense bass I've ever experienced was from folded horns - it was a case of your vision was always blurry, the frequency just changed.

I won't argue horns are the epitome of low-frequency reproduction, but they have more merit than you seem to think.

Chris

PS - Direct-radiating speakers (ported boxes etc) aren't even slightly efficient - the really high efficiency ones might reach 5% over a useful bandwidth.
I'll just say this, the amount of pro sound and bass cab manufacturers not making folded horn subs is telling...and there are some good reasons why given what we can achieve with simpler, better sounding and less expensive designs. Danley does not make a folded horn sub as far as I know and my comments were strictly about folded horns.
Old 3 weeks ago
  #28
Gear Addict
I suspect you'll find that all* of Danley's subwoofer designs are horns that have been folded. They're called tapped horns because the driver is mounted such that it fires into two parts of the horn simultaneously.

*Oh, except their 1x12" ported box.

Chris
Old 3 weeks ago
  #29
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Quote:
Originally Posted by chris661 View Post
Just because you can't do it, it doesn't mean it's not possible. Some people can look at a section of code and say exactly what it's going to do. Others can look at an engine and tell you roughly how much power it'll put out.
I can look at a cabinet, and I'll have a good idea of the physics at play, and how that will affect the sound.
I do not know anybody, not even professional designers who can look at a box or engine and accurately predict the performance...With all due respect, this is absolute voodoo.

Quote:
Do you think the guys that design speakers for a living keep making prototypes until something works, or do you think, perhaps, there are ways of predicting the performance of a loudspeaker?
I KNOW for a fact that the guys who design loudspeaker systems for a living use mathematical formulas, the laws of physics and computer simulation to design those boxes/systems. All predictions are based on known parameters of the components and the specific design of the box, and even then, they do a lot of testing to verify their calculations and design. That why they invest in expensive computer programs and anechoic chambers.

A picture might be worth a thousand words, but it can't tell you the performance of a loudspeaker, engine, airplane or a gun.
Old 3 weeks ago
  #30
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i haven't come accross many folded horns used as subs in years besides the occasional turbosound floodlights (which are quite fun to revisit every now and then - as long as i don't have to array/stack them!) but compared to more current designs such as the clair cp-218, they pale pretty quickly... - efficiency is simply not much of an issue anymore in live sr these days, like it or not.

and speaking of getting a clue of a cabinet (i just bought a new system with 3-way tops): besides some very generic design characteristics, there is no way of just looking at it and making any meaningful judgements on sound...
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