Search over ? Just beginning ?

[rickcr42]

Pissing on my own leg and trying to convince myself it is just morning dew ?

The tragic story goes like this :

A couple/three years ago I moved to smaller digs and had to let my refridgerator sized subwoofer go because no matter what off the wall tactics I could fathom in the dark recesses of that scary place known as "My Mind" (A.K.A. the Twilight Zone Bar & Grille) there was NO WAY this big mamma honker was squeezing in without being the dominant "OUCH DAMMIT ! WHO PUT THAT THERE ! @$%%^%" blunt object with edges (oxymoron ? Fk it) and it would be a matter of time before someone gunned it out the door after bumping into it over and over and over hiting the SAME EXACT SORE BODY PART until madness replaced reason and either it would get tossed or there would be a pile of marine grade plywood chunks strewn all over the main listening room looking as if someone luanched a fragmentation grenade into my house but instead of having shrapnel wounds i'm thinking hatchet marks would be the way.

Not only that my "new" room is a freakin' acoustic mongoloid bear in its layout with no single wall having a continuous span without any openings or breaks-not the best beginning when trying to tune the room to the system so add that to the room size which is smallish and this is one marriage I knew was doomed even before the "I Do" 's.The sub went and I have missed the last octave "foundation" in my music since and so have been searching for a solution that fits the room.Tall order when the requirements are limited size,highly efficient (my main system is 96dB/SPL/1W),capable of high SPL levels without breaking up-other than rattling shit off the walls and shelves-and must mate well with my current "mid woofer" box which was formerly a Klipsch Heresy but is now sans the original mid horn and tweets (still there but disconncted and blocked off for maintaining resale value).

This "bass box" and mid-high consisting of a JBL "potato masher" mid (at some point will be a wood salad bowl tractrix horn using the same JBL driver) and JBL "bullet" tweeter (also may be replaced in the future-EV T-350 horizontal though I DO like the bullets) is very fast in the passband of 50Hz-20kHz+ and has so far,and maybe my fault entirely,been a pain in the ass to mate with any of the smallish subs I have tried (sealed,front ported,bottom firing/bottom ports,etc).Either the subs failed to pass the "Quick and dirty" FM radio male announcer voice change test or if that passed ultimate downward bass extension so either a "thud" box,fine for movies,or brings nothing to the plate not already present at the buffet.

So I'm cruising this site I came across while looking for a ideas to make a turntable platter clamp and i'm groovin' to the pages being a total info junkie,forgetting why the hell I was there in the first place,and I come across an article on sub woofers that refers to a design from the dark ages of audio :

The ancient "air coupler" subwoofer from a 1950 magazine article-High Fidelity Vol.1 #1 (damn fine start methinks)

www.soundfountain.com/amb/aircoupler.html

www.soundfountain.com/amb/achighfid152.jpg

Here is the text portion from the above page :


LABYRINTH, AIR COUPLER, KELTON, HITACHI, JANIS

Subwoofers have existed since the early days of high fidelity. Even before World War II (according to Jean Hiraga in his excellent book 'Les hautparleurs' - Editions Fréquences. Paris, 1980) a man named Olney proposed a loudspeaker specifically designed for the reproduction of the low frequencies. Mr. Olney used a labyrinth (which was later tapered by Dr. Baily and became known as the 'transmission line' loudspeaker). The first issue of High Fidelity Magazine in 1950 describes another low frequency system: the 'air coupler', which is a long slim cabinet with a loudspeaker mounted on the back panel, radiating into it and just above the speaker unit is a wide port.

The cabinet is 6 feet tall (long). The Air-coupler is meant to reproduce the frequences from 20 Hz. up to around 350 Hz. The cabinet was complemented by a two way speaker or a dual concentric or a loudspeaker unit like a Goodmans Twinax or soime similar construction. Both air-coupler and full range cabinet had their low pass, respectively high pass filters. I have scanned the drawing from my (rare) copy of the first issue of High Fidelity magazine (summer 1951) and have put the drawing on another page. Just click on the drawing above. Maybe it could inspire you to build an air coupler and find the best crossover frequency."

Pretty damn cool.Pretty damn cheap/simple and just funky enough to peak my interest me being the type that thrives on going against the norm and dancing to my own beat (with a serious bass line !)


So I'm looking at this and thinking "hmmmm.....could be rabbit,could be....) and so I drop the page and the pics into a folder for future consideration/study.Cool.Potential but the reality is I will likely forget I even have the file tucked away until I do one of my periodic "file dumps" where I bust out a stack of CDROMs to unload all the crap I have cluttering up my hard drive and at which time both my burner and my Recycle Bin get worked hard.

So maybe an hour later I bounce into the asylum to read a thread or two to see if anything there is of interest and.....one...two...three.....

WHAMMO !

THE SAME DAMN DESIGN IS BEING DISCUSSED !

OK.Maybe not EXACTLY the same but more alike than different much as all ported designs have the same general gene pool and LAWS that bind them as a group.Cool ! Now we are cookin' baybee ! Something to actually bite into and chew on for a spell to see if the taste sits well and I gotta say I have one of those "hell yes this is what I am looking for" tinglies in the back of my head even though i have not actually built a model or HEARD a version of.Just seems "right"

www.audioasylum.com/scripts/t.pl?f=hug&m=121254

which led to this thread :

www.audioasylum.com/scripts/t.pl?f=hug&m=121166

and this page (look under "Tapped Horns")

diy.cowanaudio.com/

this early JBL patent :

diy.cowanaudio.com/images/air_coupler.jpg

a commercial tapped horn sub :

www.danleysoundlabs.com/DANLEY_dts20.htm

a DIY build that is not ugly :

www.speakerstore.nl/index.php?l=en&pg=12&prjID=33

www.speakerstore.nl/constructions/steppedhorn/steppedhorn.jpg

Another DIY example :

www.speakerstore.nl/index.php?l=en&pg=12&prjID=50

and ANOTHER thread/DIY example

www.speakerstore.nl/forum/viewtopic.php?t=238


1-does not get any simpler than this to build a "sub bass" box
2-goes deep,is efficient,is powerful if fed but should remain civilised in a smallish domestic environment fed smaller amounts of power (but if needed LOOKOUT DAMMIT ! WE BE JAMMIN' if the mood and power levels are right !)
3-Appears to be very "tuneable" to the driver and it so happens i have a pair of fifteeens sitting here "boxless" waiting to get back to work.The best part is this tuning can be done even after assembly by changing the port openings for either extension or power-FKN A COOL BUBBA !!!
4-Is a long SOB but the actual footprint is tidy enough to fit in any room with a high enough ceiling but better yet,I see no reason I can't use this beast laying on its side instead of upright and can even see where it can be played with a bit for long wall/short wall/corner firing port/etc to find the honey spot
5-And hell,if it outright sucks or is unworkable I am only out a sheet or two of plywood and maybe two hours of mechanical build time (cosmetics always take much longer-like for fkn ever)

Yeah.I am a bit amped about finding such an simple and CHEAP possible solution to a complex/potentially expensive problem that has been pissing me off on one level or another for a very long time.Not having that last octave is aggravating when you are used to having it and even though my Heresy's have 12 inch woofers they do at best 50Hz at the bottom end though unlike with a mini-monitor it is tight and flat (no mid bass hump) which makes the music sound a bit light even if it is what I personally consider a fairly accurate portayal of what I hear live.


THIS puppy gets built and soon dammit !

Should be fun no matter how it ends.............................


badeep badeep badeep...

[chris45set]

THAT looks like fun. I considered a transmission line before I built my sand filled open baffles for my PHY drivers a few years ago.
Fired an e-amil off to Bernard Salabert at PHY, very nice guy but he talked me out of the TL as he felt there would be too much low freq output in relation to the rest of the audio band.
Plus my listening room is pretty small and VERY soft (heavy carpet, overstuffed furniture, thick draperies and NO empty wall space). It eats high frequencies up. Wouldn't work with a mono-amped system, plus I like the fact that the PHY has no corossover network.

But I still wonder how that TL would have sounded. . . .

[southpaw]

Ive been too busy lately to stop by , but as soon as I do manage to..
I find Rick discussing another great idea. Im going to bookmark the links and will have to have a try at one point.

Cheers Rick!

[rickcr42]

Fired an e-amil off to Bernard Salabert at PHY, very nice guy but he talked me out of the TL as he felt there would be too much low freq output in relation to the rest of the audio band.

I am having a really hard time wrapping my brain around the "too much low frequency output" statement.

a-simple matter to back off on the woofer level control for system matching or NO subwoofer would work unless made specific to the main system it is to be used with (though yeah,more mismatches out there than happy mariages......on many levels )
b-the cossover region between the two is INFINITELY variable on any and all possible combinations of cutoff freqency,pass band volume and even phasing

....so I'm scratching my head on that one though knowing me i could be missing the obvious

In my own personal experience it is harder to get the ROOM to act right when you have true low bass and especially so if it is cube shaped (me) or small (me again) or has shit that can rattle (guilty as charged but being married means the room is multi-use family oriented not my own personal domain ) so crap buzzing and standing waves reinforcing certain notes enough to drive me friggin' nuts until corrected.

The other personal "bitch" is matching the types so for instance I never have been happy with matching a ported sub or a bandpass sub with my current speakers,something just goes wonky making the entire systme sound "wooly" no matter how adjusted and that is not acceptable to me.I want to hear "tension" in my bass not boom and thud so it must be tight.so tight in fact it should not be noticed with the woofer assist on or off until there is some actual content calling for the extra kick and that STILL should not be heard but more felt in the nuts.
A true horn loaded sub would give me that (and then some) but there is no posibility of fitting any that I know of in my current room as configured without totally pissing off the wife and that path is not one i want to travel until or unless there is no other way then all bets are off

Back to the above.

I seem to have a leaning towards the TL or quasi TL for bass though why I can't say and this is just a more workable version of what was formerly my first choice-the Fried "Coffin" sub woofer which is a different beast though similiar in more ways than dissimiliar being again more "quasi" TL/tapped horn than pure TL.

a "true" transmission line in the classic sense of the word uses line damping to smooth the response both electrically (resistive) and acoustically so the "box" works as advertised pretty much in any room and with any amp because the parameters are stable but using this method you lose big time on efficiency.
Low efficiency in my case would mean I would have to make up the loss in amp power and when you try to compensate with muscle for any losses in self power it usually means

A-compression of the bass notes when you run out of steam due to having already reached the full potential of either tha amp or the drivers
B-Expensive monster amps in combination with "stacked" woofers,also expensive and space gobbling which eliminates any advantage the TL would have over a full blown horn like the Edgar subs,the Bass Tuba series or the Lab horn.

Because the above is more of a hybrid of a horn (thus called a "tapped horn") and a TL it gains better efficiency (hence less power needed OR less compression of the bass for the same power levels) and still terminated the back wave properly preventing bass-note cancellation.

At least in my limited knowledge of electro-acoustics is how I understand it.

another "plus" is the variability of the design that says to me I can FORCE this type of enclosure to work with prettymuch any driver with a low enough F3 and finally there are ZERO angles in a couple of the versions making construction a snap because all the cuts are straight cuts and all the joints simple reinforced butt joints-something within the capabilities of any would be builder who is either able to make a straight cut without screwing up or in a pinch to have to local lumber yard cut at a price that doesn't beat you up.

For instance home depot charges $2 per cut so figure whatever a sheet of 7 ply furniture grade plywood goes for,multiply that by two then add up the cuts at $2 per and the price to build is right in line with Team El Cheapo standards

some reference points :

Product details from the "Godfather" of the Transmission Line Loudspeaker,I.M. "Bud" Fried :

www.t-linespeakers.org/classics/TLS80/index.html


My "former" first choice sub,the Fried "Coffin" :

www.t-linespeakers.org/classics/coffin/index.html

and a more domestic freindly version of the coffin :

www.t-linespeakers.org/classics/friedH/fried_H.html

The "tapped horn" is a first glance an upright coffin sub with the speaker driver moved to the long side panel instead of the end panel as in the IMF version so in essence quite alike but more harmonious with a real world home/wife/family/freinds in the placement due to the footprint being easier to squeeze into.The main difference being the footprint is more condusive to use in a real world living room where not EVERYONE is impressed with how your gear looks so the goal more of a family freindly harmonious integration than "look how coool I am" which more often than not has the opposite effect on anyone that has a mental thought process above box of pencils.

somewhere between the lines of all the above is a subwoofer I can live with.It doesn't have to be a world beater just needs to give me back a solid "floor" for my music and with a little bump up in EQ/VOL add the "Special" back to movie audio "Special Effects"

[chris45set]

Rick, you are not missing the obvious, only the simplicity.
My driver is, essentially, a single "full range" device with a co-axial tweeter.
The paper coned portion is good from ~ 32Hz to 10kHz where the tweet takes over.
So the 12" portion is not just a woofer, but also handles the midrange as well.
And there is no crossover, the two "naturally" roll into each other, the tweet stepping up as the paper cone rolls off (at least if one believes the marketing hype . . .).
Plus I use a single stereo 45 SET amp so there is nothing between the XFMRs and the drivers except cable.
I considered Lowthers for awhile, but these seemed a more reasonable compromise as I did not want to add or split drivers anywhere close to "the magical midrange".

See link

www.phy-hp.com/English/Products/KM30_SAG_E.html

Also, don't know if you have seen this, but I found it very educational and Mr. King seems to know his stuff.

www.quarter-wave.com/

Good luck with your design, should be an interesting journey

[PinkFloyd]

Rick disappeared of the face of the planet in April 2007, wherever you are big guy I wish you well, you're welcome back here anytime.

Pinkie.