Karlson and Bass

An email discussion with a friend

I didn’t want to sound negative when everyone was getting excited about the Karlson speaker. Besides, I would have been outnumbered!

When I was investigating various options for my diy speakers, I came across the Karlson and some internet enthusiasm for it. So I looked further and found more comments to add some balance. The comments I kept are at the end of this article. After reading it you will see why I decided to abandon that idea.

Since the suggestion was that you might want to go to all the trouble of building the Karlson, I thought you would like to see some modern comments on it. It’s a lot of work to make a speaker like that, and I thought you would like as much info as you can get.

On the internet there are enthusiasts for almost anything, sort of like fan clubs. You won’t get an unbiased opinion from their web sites. Some of the worst misinformation is about older pieces of technology. Things that are mere curiosities, in terms of modern-day absolute performance, come across as buried treasure that is sure to bring you more joy than anything in today’s modern/corporate/faceless/plastic world. The revered, charismatic, slightly oddball, pioneering, obsessed individual inventor versus a nameless design committee in an uncaring Japanese corporate profit-oriented industrial giant. Only one of these products can possibly have soul!

I know I might be the only one in our audio group who won’t put personal listening impressions as the ultimate (and ultimately only) way of choosing audio equipment and tweaks. I insist on sound basic engineering, first and foremost. I don’t mind if it is old engineering, eg horns or valves, as long as it is sound. I also apply proper research findings on psychoacoustics in deciding whether some minor improvement in measurements can be heard by the human ear. It usually cannot. The ear is very good at one or two things, eg localising a sound source, but in most areas it is a rather blunt tool, regrettably. (No point in fussing about the difference in two very low levels of distortion, for instance.) There is a huge audiophile myth about the infinite subtlety of the ear’s resolution. Science has shown otherwise. So I am not a big fan of using measurements for fine tuning, but measured results have to be basically in good order. And finally, I absolutely agree with the group’s general consensus that listening by ear is very important. But, and it’s a big but, only if we don’t know what we are listening to! I have spent enough time studying (for my bit of consulting on the side that never turned into a wage earner) how the mind perceives and creates impressions, and how it processes data coming in through the five senses, that I know it is completely, completely futile to conduct listening tests where the changes are known to the listener. The mind’s (mostly unconscious) thoughts about the changes, and everything else going on in one’s life at the time, will always overwhelm the incoming data. If the listening test is set up double blind, or at the very least blind, then the results will be highly informative. And mostly very frustrating and disappointing because they show how poorly the ear can resolve most small changes. That is why a lot of audiophiles, married to the concept of the infinitely subtle ear, and convinced by their personal experience doing listening tests on subtle tweaks, try to attack the validity of the double blind test method and hence all the findings of the science of psychoacoustics.

How does my attitude put me at odds with the torrent of misinformation on the internet and the audiophile magazine communities? Well, it means I won’t consider bad engineering, and I’m not impressed by claims of sonic improvement by overengineering to the nth degree either (although I admire some of the massively engineered stuff out there as much as anyone, but I admire it as industrial art –even resistors!). And I won’t even read listening impressions except for amusement, especially the ones that start “so I hooked it all up and sat down for a listen, but it sounded like shit so I left it to burn in for 30 hours/days, then came back and ……”. Scientifically researched listening tests do grab my attention, but they are hard to come by, nay impossible in the internet fan clubs and industry-slave magazines.

So, what about your search for good bass? I reckon good bass is 90% a room problem, which means even with a ‘perfect’ speaker the bass will be 90% bad unless one is miraculously lucky. 92% bad with an average good bass speaker, 94% bad with a less good speaker. Sonic impressions comparing the speakers above may lead to a certain preference, but it won’t lead to good bass. Something has to be done about the room. The first 50% involves getting the frequency response right, which I am trying to tackle with a digital equaliser – I am sure it is worth it. The next 50% (hang on that adds up to 100 not 90 – oh, who cares) involves the time domain response of the room, and involves fancy equipment to measure, and one or both of expensive electronics and expensive/ugly room treatment. My plan is to do some modest room treatment one day, and wait for the fancy electronics to get better and drop in price into my reach. The reason I picked horn bass was for the huge uncompressed dynamic capability, the significantly lower distortion, and the fact that I knew I would be using an equaliser to handle the lumpy response. In your case I think your wooden floor really ‘tunes’ the bass, and not in a good way unless we like that visceral floor-shaking sensation (I must admit I like it, but it isn’t good bass ‘cos it only happens with certain notes). If I had a normal subwoofer and a wooden floor I would seriously think about bolting it to the brick walls, after finding the best location in the room for the flattest frequency response – or if I had an equaliser with it, just bolt it into a corner and equalise it.




Barry Mann    View profile

  More options Aug 14 1999, 4:00 pm 

Newsgroups: rec.audio.tech

From: niteb...@voicenet.com (Barry Mann)

Date: 1999/08/14

Subject: Re: Karlson speaker enclosures

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In <7p1pu0$ge...@barad-dur.nas.com>, on 08/13/99

   at 12:08 PM, "John Rutter" <jrut...@nas.com> said:

>Has anyone heard these?

>Here is a description, for those not familiar:


>If so what drivers were they using, what were your


>Apparently, speakerbuilder reprinted an article from the

>1950s on construction due to steady stream of requests.

>I've heard one rave review and one general comment on them

>being "boomy"

This is one of those audio legends that never seems to fade.

These enclosures were popular among the DIY crowd in the 50's and 60's.

I'm not aware of any commercial applications using these boxes, but there

may have been some.

These boxes are very complicated to build, because they have multiple

internal baffles and a logarithmic tapered opening in front. They also

tend to waste wood because they are hard to layout efficiently.

I built a pair and loved them at the time. They were remarkably efficient.

Yes, they were boomy, but at the time I was into boomy so that was

actually a good thing. One disadvantage of the design is that there is no

convenient spot to mount a tweeter, one must use a coaxial speaker or

mount the tweeter in a separate box. Since the woofer is mounted at an

angle, behind a baffle, the coaxial tweeter beam will fire out at an angle

that will not usually cross the listening position and there will be

internal early reflections.

Any DIY speaker always sounds good ("better than the 'commercial'

designs") to the builder, and my Karlsons were no exception. I used them

while in school and they were popular with my friends. Eventually, the

Karlstons went into storage. Some years later, after I became

professionally involved with audio, I dragged them out and gave a listen.

Even though I was the proud builder, it was impossible to be kind when

describing what I heard. Fortunately, I found a buyer who wanted a

"classic" set of speakers (cheap) and moved on.

They certainly looked impressive (or at least unconventional).

If you decide to build a pair, check to make sure your woofer will fit in

the space available.

niteb...@voicenet.com (Barry Mann)

Hi John,

John Rutter <jrut...@nas.com> skrev i en


: Has anyone heard these?

Actually yes, you are speaking about the enclosure type with that

exponential slit on the front, right?  - it was a musical instrument

speaker, and it was used for electric piano.

: If so what drivers were they using, what were your

: impressions?

Some 12" unit, I think it was a US made cabinet, but I'm at a loss in terms

of remembering the brand name on it, mind you: were are talking 'seen on a

stage once upon a time some 25+ years ago'. It just might - MIGHT - have

been an early Peavy, it WAS from one of the US ""instrument stuff

manufacturers"". I seem to be able to remember is main colouring as bluish.

As for sonic impression: midrangey ... possibly warmer than it would have

been with a normal front design.

: Apparently, speakerbuilder reprinted an article from the

: 1950s on construction due to steady stream of requests.


: I've heard one rave review and one general comment on them

: being "boomy"

They probably would so be, as a consequence of having improved coupling to

the air in the upper bass/low midrange. I wonder if a slight distortion

reduction may be a merit of the design, but you have to remember the day and

age of it. The prime parameter back then was efficiency, not linearity.

Could that rave review have been from a guy with some kind of single ended


     Kind regards

     Peter Larsen

AT-Højttalerværksted    View profile

  More options Aug 14 1999, 4:00 pm 

Newsgroups: rec.audio.tech

From: "AT-Højttalerværksted" <a...@image.dk>

Date: 1999/08/14

Subject: Re: Karlson speaker enclosures

Forget it ! It didn,t work either in theory or in practice. I seem to

remember Dick Pierce responding to the same question some months ago.

Regards, Alan

Randall Bradley    Newsgroups: rec.audio.tech

From: r...@ultra1.rdrc.rpi.edu (Randall Bradley)

Date: 1999/08/14

Subject: Re: Karlson speaker enclosures

        think of them as BAD horns... too small.

        So, the effect is a VERY choppy response, one that looks

        like a "comb filter".

        Not good for that reason. It is unlikely that there was

        any real efficiency gain over that of the driver itself,

        except as there may have been peaks in the freq response.

        It just looks neat.


                                BEAR labs

        the Karlsen name probably got confused in peoples minds with

        "Stromberg-Carlson" who at that time were still a highly

        regarded brand name electronic manufacturer! That might have

        added to the mystique.

The place escapes me, but there was an informed article about this

enclosure design some years back.  The Karlson was breathlessly

advertised back in the fifties and acquired a certain following.  It

purported to be an act of genius.  The authors of the article in question

ran the enclosure through all the tests and, moreover, worked out all the

math on the enclosure.  It combined reflex loading with a horn.  The

baffle sloped back into the enclosure and a "horn" mouth was approximated

by simply attaching two curved face pieces to the upper half of the

enclosure.  The authors of the article in question point out that Karlson

had no engineering training whatever and worked from instinct.  It was a

remarkable instinct, however, for they demonstrate how at every turn in

his design, Karlson made the worst choice possible.  The measured

response of the enclosure is the worst ever published.  A side benefit

was that you could use any speaker driver in the enclosure--Karlson said

they were all optimal in it.  This was back in the days when folks bought

raw drivers and mated them to an enclosure, before T-S notions (first

popularized by Nowak of Jensen Loudspeakers in 1962) prevailed.

Doug Purl

Ted Grusec    View profile

  Newsgroups: rec.audio.tech

From: t...@dgbt.doc.ca (Ted Grusec)

Date: Mon, 17 Oct 94 03:36:54 GMT

Local: Mon, Oct 17 1994 12:36 pm

Subject: Re: Karlson speaker enclosure

I have had private, casual conversations with a world-renowned

loudspeaker researcher who said that the Karlson was one of the worst

enclosures he had ever seen, on both theoretical grounds and in

measured responses including subjective assessments.

Dear Dick and group - I own a pair of original

Karlson's and am aware of the extravagant claims and of the interference

"dips" created by the "Karlson Coupler" plus some peaks from the crude

horn formed by the intersections of the "front shelf" and sloped baffle


I have frequency measurements by Paul Klipsch which show the horrendous

"suck-outs".  Also, I suspect the very low frequency response is just

that of a vented box of equivalent volume to tha Karlson's back chamber

and same Fb (44Hz in the case of a 15" Karlson box.

What I don't see in Klipsch's graph but seem to hear and measure is a

gain' above direct-radiator use of the speaker involved between 70Hz and

300Hz.  My Karlson in this range is rough but as loud or louder than my

homemade 3/16 size 55Hz m=.6 Horn.  Dick - do you have any explanation

for this??  I really like a karlson for electric bass guitar although for

it's bulk, a reflex cabinet with two 15" could be built (or two little 3

c.ft. boxes for portability)


Fred Ireson

Ron  <ron...@yahoo.com> wrote:

>BTW, another attribute of the Karlson system was its tremendous


What "tremendous efficiency?" The efficiency was and is

determined by the reference efficiency of the driver, despite

Karlson's rather bizarre and unsupportable claims about how the

slot worked. Indeed, the slot provides, if anything, an

acoustical inertance, mass loading the driver somewhat and thus

REDUCES the efficiency. The effect is small, to be sure, but

there is no such "tremendous" increase in efficiency.

That they were of moderately high efficiency is simply because

many of the drivers of the day had moderately high efficiency to

begin with. And, as Small quite clearly demonstrated, there is a

clear and reciprocal link between efficiency and lower frequency

limits of drivers, as the resonant frequency of a driver goes as

the efficiency goes as the third power of the driver's resonant


At wavelengths proximal to and longer than the dimensions of

the slot, the slot has NO effect save increasing slightly the

mass load on the driver, thus have a deleterious effect on

efficiency. Above that, the response is dominated not by the

slot but by the chamber in front of the woofer, setting up a

rather complex but resonant load. Efficiency is not

"tremendously" increased. There may well be many peaks whose

effective levels are above that of the broadband reference

efficiency of the driver, but that hardly constitutes an

increase in efficiency, at least in any sense of the term

accepted in the industry.

You can't fool mother nature, even when you have a patent number

you can stick on it.

>I sold quite a few with the Mullard 44 SE tube amp (that I

>also manufactured). It was rated at 4 watts per channel...

And with a basic efficiency of 90 dB/W, which many of these

drivers had, that means that music, cranking along at 85 dB, is

using but a fraction of a watt in a modest-sized listening room.

Just like ANY other speaker with that kind of efficiency.


|            Dick Pierce            |

|   Professional Audio Development  |

|   1-781/826-4953  Voice and FAX   |

|       DPie...@world.std.com       |

>>In article <8q0f5vomdqo6sul60le6dsvg2u0a2h6...@4ax.com>,

SO, let's try this again. You have no objective direct

comparisons. Same driver in two different enclosures, or two

matched drivers compared in a time-proximate fashion. You know,

the way the rest of the world is required to do it. You have no

measure of efficiency, like the rest of the speaker world is

required to do.

>>Yes, that was the explanation. But the explanation was wrong.

>>Simply look again at the fact that a slot, ANY slot, at

>>wavelengths larger than the dimensions of the slot, provides

>>nothing more than an acoustic inertance: a mass. And mass

>>loading ANY driver reduces its efficiency. At wavelengths

>>shorter than the dimensions of the slot, cavity resonances and

>>diffractions dominate, and none of these "increase efficiency

>>tremendously," the simply perturb the frequency response. Now,

>>it's altogether possible that a seriously unflat response is

>>perceivable as "higher efficiency."

>But it was concurrently perceived as very extended frequency response.

>Seems to me you again dismiss what it sounded like, in favour of your

>idea of what it should have sounded like.

No, sir. we are dealing with claims, in this case YOUR claims.

>>But the DEFINITION of efficiency is the ratio of total acoustic

>>power output to electrical power input, and neither Karlson or

>>anyone else has provided a single piece of data to support the

>>assertion that the enclosure provides any such "tremendous"

>>efficiency. It's a trivially simply measurement to perform to at

>>least get a  rough estimate, and it's a completely repeatable

>>experiment. All that is needed is one Karlson advocate to

>>provide such a measurement, and have that measurement repeated

>>by someone without the vested interest, and the claim all of a

>>sudden becomes quite credible.

>The issue is not the technical difficulty of measuring efficiency, but

>the hassle involved. You need an anechoic chamber (or at least, a flat

>roof top), a Karlson enclosure, a very large flat baffle, a full range

>driver, not to mention an oscillator, high power amp and SPL meter.

>You need to install  the speaker at lest twice. It will take the

>better part of a day, at least.

Thank you, kind sir, for telling me a technique of measuring

efficiency, despite the fact this is something I do on nearly a

daily basis and have done for over a quarter century.

And if I can do it, why didn't Karlson.

Karlson CLAIMED that the enclosure "can give you 10x the

efficiency," (exactly quoting his literature) and "2 more

octaves of bass." These are TRULY EXTRAORDINARY claims, they

violate the fundamental efficiency/bandwidth/enclosure volume

relationship not by a small bit but by an order of magnitude.

Take, for example, that for a given enclosure size, efficiency

goes as the CUBE of the low frequency cutoff. Assume the claim

of "2 more octave of bass" is correct: that suggests an

efficiency decrease by a factor of 64, yet they are ALSO

claiming an increase in efficiency of up to 10 times. TRULY

extraordinary claims require truly extraordinary evidence. To

date, for a period of 40+ years, not a single shred of

supporting evidence has been advanced.

>And what for? To prove a claim made for a 35 year old design? Frankly,

>I don't care.

Fine, then why make the claims if you don't care. Why make them

in a newsgroup whose charter is to discuss the technical aspects

of audio?

>Certainly, not enough to go through the exercise.

Well, that seems to be a disease that has inflicted pretty much

every single Karlson advocate because not a single one has

advanced a single piece of data to support the claims.

>However, if you feel the need to prove me (and others with fond

>Karlson memories) wrong -- be my guest...

Gee, how about those how are MAKING the claims to prove the

claims FIRST. That's the way it's done everywhere else, or is

Karlson also allowed to ignore those conventions as well as the

laws of physics.


|            Dick Pierce            |

|   Professional Audio Development  |

|   1-781/826-4953  Voice and FAX   |

|       DPie...@world.std.com       |

From: bassma...@aol.com (BASSMANCP)

Date: 24 Feb 2003 15:41:39 GMT

Local: Tues, Feb 25 2003 12:41 am

Subject: Re: http://www.karlsonkit.com

Hi there,

I have some Karlson experience. I have built about 30 of them. If you build

them right, it will not be *fun* and they will still sound like Karlsons....not

good. I will speak about my experience with the perceived efficiency though. I

used Karlsons for subs at an outdoor gig for years. I cut them off at 150 to

keep the secondary cavity resonance from being heard (Karlson midrange is

unusable by today’s standards & I'm being kind). I would use only 200 watts of

QSC power per pair of speaker's. It took a lot of mid/hi drivers and power to

keep up with the bass all over the place from the Karlsons. Big low end from a

small cabinet has uses. Unfortunately, it was designed as a full range enclosure

and it is not a good choice for that. I can't stress enough that it takes quite

a bit of know how to build them right, and I notice many of the web designs are

not to original spec. (not that it matters ;o)

I have also tried 604 coaxes in them. You have to resize the cab (which Karlson

recommended against) and the horn almost makes it to front of the front baffle.

I think I have the original 15" and 12" articles on .pdf. You can also put a

revolving plate in the front opening (simplified) and it sounds closer to a

Leslie than any other clone I have heard. That is my favourite application. If

you do build them, make a router template....you'll need that....

Good luck!

Chris P