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Chris A

A K-402-Based Full-Range Multiple-Entry Horn

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8 minutes ago, Khornukopia said:

In my experience, compression driver mounting studs are common. The K-402 throat does create a tight tolerance, so it is helpful to remove (or install) all four nuts using an even pattern, not just completely removing (or installing) one fastener at a time. After doing it a couple times and learning the technique, it becomes fairly easy.

 

 

I'm glad someone else thinks these studs are funky-doodle.  When I first got mine, the studs came off with the driver (when I swapped to the TAD's).  So, I had to get some more.

 

Initially, I bought some bolts.  Well, that didn't work out.  Finally found some studs and as you say, you have to draw them up evenly.

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Posted (edited)

For fun I listened to the "other" K402 with the supplied driver along with the one with the barely installed good CD.

 

Well, I guess if I had never heard a better driver I could learn to live with it but the top one and one-half octaves are pretty ugly sounding.  I made them slope downward to be able to enjoy listening.  I cannot remember what the sticker on the magnet says but it has a one as the last digit and I was expecting an A.  Not that it matters.

 

But the good part is even in this crude condition you can hear a grandeur from these horns.   Even with one mediocre driver and another driver barely attached to the horn you can hear there is something unusual here.

 

I am hearing glimpses of a disappearing speaker system.  Can't wait to get some boxes made!

A question for the scientist/engineer, Chris A,.:  I got a sheet of a butyl rubber sheet covered with a thin, but not foil-like, sheet of aluminum.  Figured i would place this upon the horn everywhere but where the baffle boards will be placed.

 

Do you think it would be a good idea or a bad idea to then place plywood on top of this and apply pressure to the whole thing or best to just use the plywood and leave out the rubber?

 

I cannot get a handle on whether we need to strengthen the walls or simply damp them.

 

What do you think?

 

Not that I have anything of interest to offer at the moment but I suspect you have posted your measurement protocols.  If you would supply that link I would like to get going with it so when i do have measurements worth sharing  they will be of some comparative use.

 

Take care,

[Moderator edit, deleted empty space that was below this]

 

Edited by dwilawyer
There was 3" of nothing at bottom of post

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4 hours ago, Coytee said:

Initially, I bought some bolts.  Well, that didn't work out.  Finally found some studs and as you say, you have to draw them up evenly.

When I changed out the K-691s for TADs I did not understand what the heck was intended. So I tapped out the holes in the TAD 1.4 to 2" snout and put bolts all the way through

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That's certainly one way to hold them tight!!!

 

 

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You must have the newer version of the 402?  Mine have that big white, flashing that they must have ground off, stripe on them.

 

I've debated on painting them but then....I have to take the drivers off....  so nah.

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14 minutes ago, Coytee said:

You must have the newer version of the 402?

Yes they're the latest I believe.

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Posted (edited)

Sorry about all of that wasted space on my last post.  I did not do that on purpose.  

 

No question drivers having a snout have an easier time - but I found with the studs that it went fine.

 

Thanks for your photographs babadono.  Looks like you removed the big cork spacer from the K402?  I have removed the stand to make it easier to make measurements plus I did not like all of that intermediary stuff - did not make a smooth transition.  As it is i am using a small amount of mortite to fill in the gap hoping this will not be needed with the CRITES rubber gaskets which I have ordered. Very nice people. Sure is much easier checking for alignment with these versus the INLOW which your hand could not fit into.

 

I have found that even a fifteen inches wide baffle will still need to be chamfered at the mouth side - the curve begins just before that.. My baffles will be closer to seventeen inches.  Hoping for an intimate contact for damping and strengthening.

 

I see my idea of using threaded rod is not realistic for the front of the baffle.  Will have to use a piece of wood and screws.  The front piece will be deep enught to make contact with the top and bottom of the horn. I want to be able to remove the baffle easily at the beginning.  Eventually I would probably epoxy the baffles to the sides but still retain this to squeeze the baffles into the horn sides.

 

Since I am going to follow what Chris A has recommended: placing the asembly in the corners as close as I can.  A bib for beneath the K402s will be needed.  Should this extend to the floor or should there be a gap?  These bibs will contain the RYTHMIK woofers for the first octave.

 

As I get to know these horns I am beginning to hear the resonances due, mostly I suspect, nothing attached to the mouth.  I am going to build a crude frame out of 2 x 4s to use in the interim.

 

Got my cutting list ready.  Now to pick up some plywood next week.

 

I had hoped Chris A's heavy duty CA402s would have become available but I could not wait any longer.

 

Reading through the thread AGAIN I found this which told me in no uncertain terms that Chris A is a wise man.  These thoughts are extremely appropriate and timely in this era of models and experts:

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

I think that a lot of people make the mistake of believing simulations over real life a great deal. In my experiences I've seen otherwise bright engineers make that mistake periodically over my engineering career, often to the derision of the more experienced engineers that knew better (...from the school of hard knocks).  Fortunately, the enterprises that I worked in were guided by these most experienced engineers and those issues of over-belief in simulation were mitigated quite early before other less recoverable decisions were made from those simulation results. 

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

Those are the words of someone I will follow.

Edited by rick mcinnis

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On 5/31/2020 at 9:34 AM, rick mcinnis said:

As I get to know these horns I am beginning to hear the resonances due, mostly I suspect, nothing attached to the mouth. 

 

Hmmm, got me wondering.  The K-402 horns are delivered by Klipsch in several arrangements without the mouth attached to anything and in at least one case fully attached and in a box (KPT-305).  Are there significant differences in sound quality due to resonances for unattached mouths?

 

What is it you are beginning to hear exactly?

 

It is an appealing idea to my logical mind that the horn would resonate coloring the sound left undamped/not very stiff or rigid and mouth unattached, but, what seems logical ain't necessarily so!

 

and...even if this could be proved to be the case the question remains at what level of magnitude is it happening - in other words is it audible?

 

One thing I know in my following of ChrisA over the last years is that  measurements with a calibrated UMIC-1 and REW and the subsequent iterative dialing in of my speakers based on the K-402 makes a huge audible improvement!  So, clearly adjustments based on careful measurement do work.  We can correlate sound which the mic/software measure with what we hear.

 

I wonder if the UMIC-1/REW combo could measure any resonances of the type postulated?

 

I propose this test.  Tell me if you think it valid.

 

Hypothesis:

The K-402 horn playing midrange and high frequency sound/music with mouth unattached resonates so as to color the sound/music in an audible way. (note that this test will be confined to midrange and high frequencies so that it may be carried out on a K-402/CD combination prior to any MEH mods.)

 

Setup 1:

A third generation (thinner) K-402 with TAD-4002 CD will be mounted on its Klipsch stand (attached to mouth at 2 bottom holes only) and placed on top of a Jubilee bass cabinet in a corner of my living room with the bottom of the horn at height of the bass bin - 40 inches. My calibrated UMIC-1 will be mounted on a tripod with mic capsule at 45 degree angle and the tip at height of 54 inches - the middle of the CD at a distance of 3 feet from the horn mouth. Plentiful thick fuzzy absorbent material will be placed on the floor between the horn and the mic.   REW sweeps will then be recorded from 400 - 20k Hz going back and forth several times with ChrisA (if he's willing) to get representative measurements of this combination. Perhaps varying the sweep volume in an attempt to excite measureable resonances in the horn - (not the room.)

 

Setup2:

The very same K-402 and TAD-4002 samples mounted in a KPT-305 box (securing the full mouth flange at all 12 factory drilled mounting points)  Keeping other variables of measurement as constant as possible (mic position, dampening placed on floor in front of horn between horn and mic) the same set of sweeps will be recorded.

 

Analysis:

The recorded sweeps will be compared looking for differences possibly due to horn resonances.

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On 5/31/2020 at 9:34 AM, rick mcinnis said:

 

Thanks for your photographs babadono.  Looks like you removed the big cork spacer from the K402?

I removed nothing from the 402, except the K-691 driver that came with it. Perhaps the gasket in my case is still on the front of the K-691? They're on storage shelf long forgotten.

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IAt the moment the horns are supported by the front flange resting on concrete pavers atop a box along with a stack of wood to support the 2441.

 

Tomorrow the CRITES gasket arrive and then i am going to install those with the crude 2 x 4 surrounds.  Will be interesting to see/hear if it makes any difference at all.  I thought there was some consensus that it is a good idea to keep the mouth stiff - the whole horn ideally, of course..

 

I will have measurements of both to compare.  Whether what I think I am hearing is measurable by REW and my non usb mic - I did get the calibrated one from the folks in Michigan (?) and use a FOCUSRITE Scarlett2 USB box.  I know when I cleaned up the throat there was a measurable difference - whether that difference is audible is another thing and whether what we can measure is what we are hearing is the biggest mystery of all.  Still measurements are important as a comparative and a map of where you are going.  Once you get used to doing it you cannot live without it.  This could be both a good and a bad thing - could we start hearing what we are seeing?  One has to stay on guard!

 

I have no real idea where what I have called resonances are occurring.  They are not audible like a LP tick, of course.  More like that stuff we call digital noise - that bit of haziness that permeates everything = but is nothing like it used to be.  We have come a long way with digital playback.  I am one perfectly happy with REDBOOK since nothing much I am interested in comes in high resolution so I concentrate on that.  I have bought a few 24/96 downloads but I did not have the REDBOOK version - namely ABBEY ROAD 2019 mix - I know one thing - the 2019 mix sounds much better than my original CD release which is more unusual than it should be.

 

As it is with any audio component - it does take a while for the excitement of new to wane and one starts hearing things they did not at first.  Of course, these are minor in the extreme but that is what all of this audio kookery is about - trying to get a little but closer.

 

To make this clear - I was comparing them to a horn I had lived with for seven or so years.  I was well acquainted with their foibles - or more properly their foibles were plainly revealed by the 402s.  Every device has its weaknesses.

 

Never for a minute do I not consider I could be dreaming.  I was just wondering if others had noticed this, too, over time.

 

There is not a doubt in my mind these are the finest sounding loudspeakers I have ever heard.  I am so anxious to get a box built to heare 60 or lower Hz to 18 KHz coming from one source - it is all I am thinking about.  (which made me think how strange it is we honor Mr. Hertz by usually writing Hz but not with Mr. Volta.  I guess he should have dropped that vowel for a bit of extra infamy?

 

To meet Chris A's advice to get the box within 18 inches of a corner - and knowing the limitations of my woodwoerking abioities i am going to make a box with another box on the back going from top to bottom but about one-third the width.  This will get me much closer to the corner with a 45 inches width - my box will be slightly larger in the width and the height - and having a slightly larger internal volume than the KLIPSCH box per Chris A's measurements - assuming 3/4 inch material.

 

The small box will extend 16 inches behind - 26 inches tall and 16 inches wide.  I am not worried about those two dimensions being the same since much of this area will be filled with the compression driver and the larger back chamber I use.  The chamber is a PVC plumbing cap that is the same diameter as the jbl.  Much of the internal area has been filled since it would be too big as is and I have no way to cut it down accurately.  I do not doubt this limits its ultimate power output but this means nothing to me since I do not want to know what that would be.  The use of wool and wool felt in the enclosure does make an audible difference to me.  As long as a placebo works why fight it!

 

The box sides will be sixteen inches which will make it easier to find a way to attach the woofer baffles to the cabinet walls also to add damping stuff.  Finding a way to put some pressure on the top and bottom of the horn with the enclosure is something I want to try.  

 

All thoughts and cautions are appreciated.

 

 

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Any sketches of how the cabinet will look?

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Nothing much to sketch - just basically two boxes.

 

At the moment the plan is.

MAIN BOX - outside dimensions

Front 44 inches wide by 32 inches tall by 16 inches deep

 

SMALL BOX - outside dimensions - centered on the back

17.5 inches wide x 17.5 inches deep x 32 inches tall - the hole in the MAIN BOX will be 16 x 29 inches - the back of the MAIN BOX which will hold the SMALL BOX will be removable and there will be a removable panel on the back of the SMALL BOX.  Access is needed to make adjustments to stuffing and damping along with supporting the compression driver.

 

So 33.5 inches of depth at the center which should fit tight enough into my corner to work well down to 60 to 70 Hz.

 

All dimensions subject to change, of course.  Hoping these will work.  Cutting to begin Saturday and then the dimensions will be etched in baltic birch plywood.

 

Got the wood today.  18 mm baltic birch for $58.00 per sheet which I think is a very good price.  

 

 

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What I cannot figure out is 2 boxes?

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A small box attached to the back of the big box to allow the thing to get further into the corner.  

 

The small box will be 2 pieces of 3/4 plywood for each side to make a very broad glue joint.  T

 

The small box will be the same finished height of the big box and centered on the back.  I like the idea of having, initially, two access points to adjust things.  The back fo the small box will eventually be glued.  The back of the big box will be removable

 

Easiest way to do it and less wasteful of plywood.  Along with my inability to make a clean inside 90 degrees cut. 

 

As with most DIYers it will be overbuilt since I do not have ability to know what can be done without.  I do not think anyone ever went wrong with a box that was too sturdy.

 

I doubt i will be exploring the limits of that!

 

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Posted (edited)

Got my plywood today.

 

For anyone wanting 4 x 8 Baltic birch in the Atlanta area  - SUWANEE LUMBER is Suwanee - close to Buford - is selling the sheets for $57.00. The price was so good I thought they were confused but it is the good stuff.

 

I have settled on the dimensions of the big box - conditional on whether Chris A thinks i am going wrong - 44 inches wide - 37 inches tall - 16 inches deep.

 

Would there be any deleterious effects from the box being that tall with the horn centered?  I could move the horn closer to the top but having it centered would make it a little easier to get the baffles attached to the top and bottom of the box. Since there needs to be a baffle underneath I know the height is not important all to itself.  The baffle below will be an enclosure for the RYTHMIK woofers.  Luckily they do not require large enclosures to go as low as I would want.  As is in my room they extend to 15 Hz with an actual rise in response after EQ.  Not that I wanted a rise but that is how it works out AT THE MOMENT to get the flattest response. 

 

I got some of this stuff from McMASTER CARR and it seems to do some damping.  I suspect more than one layer is needed.  i figure this with some way of having contact with the box for the top and bottom of the horn to really settle down the horn?

https://www.mcmaster.com/9709T29

 

With the horns mounted in a temporary 2 x 4 frame I am able to place 12 x 12 concrete pavers (with a thick felt between horn and paver) on the top with pavers underneath making gentle contact.  The top and the bottom make a satisfying sound when tapped.  The side are much better than when none of this was done but the baffles will make all of the difference in the world.  Won't be able to use the concrete in the box but it shows me how much good reasonable pressure on the walls can make.  The CD is supported by a stack of wood for the moment. 

 

McMASTER CARR is an amazing store!  Like the ultimate HOME DEPOT.

 

Another idea is to not remove the ribs entirely but make them 3/8 inch at their tallest - make a corresponding cut in the baflles to get a centering device.  The cut would only be as long as needed - not across the board.

 

 

Edited by rick mcinnis
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15 hours ago, rick mcinnis said:

For anyone wanting 4 x 8 Baltic birch in the Atlanta area  - SUWANEE LUMBER is Suwanee - close to Buford - is selling the sheets for $57.00. The price was so good I thought they were confused but it is the good stuff.

 

That is a good price.  If I send you the money will you buy a couple of sheets and mail them to Michigan.  On second thought, that won’t work.

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29 minutes ago, DizRotus said:

 

That is a good price.  If I send you the money will you buy a couple of sheets and mail them to Michigan.  On second thought, that won’t work.

 

Yeah, the 19mm thick stuff won't fit through the automatic stamp-cancelling machine.

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On 5/31/2020 at 11:34 AM, rick mcinnis said:

Sorry about all of that wasted space on my last post.  I did not do that on purpose.  

I fixed it. It happens.

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At the beginning of the Chris A project he had mentioned that there could be advantages to vertical mounting of the K402.

 

Since this would make it lots easier to get closer into the corners and generally a less bulky installation I changed mine from horizontal to vertical this morning.

 

I think it works better but there is no question they are too high.  I have never had a system that sounded this good while walking around the room but that is not something i normally do.  I am not saying it sounds immensely better - it is as much different as better.  So the rationale is actually gaining some floor space.

 

So considering it again. What I wanted to do at the beginning but got worried the horn wall was too curved and now I realize it would not be any more of a problem than the other set.

 

It would stiffen the largest wall which needs the stiffening most but I wonder, since I have no idea, if this wall puts the ports in a less ideal place?  Looks like the ports are going to be much nearer the surrounds where I suspect the short walls, just by their obvious nature will place them closer to the center of the cone.

 

What do you think, Chris A?

 

I have a bunch or MORTITE and so i applied it to one of the horns - It does make the walls sound duller when you tap them.  I am not hearing anything at the moment.  More of one of those things you do so you don't have to wonder if you should do them.  Wish stainless steel shot was not so expensive - would probably make a good combination mixed into the MORTITE.  But not a chance.  No lead - does something weird to everything it touches.

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@rick mcinnis How far off the floor are you running them as vertical...mine are about 13" off the floor.

 

Sent from my SM-T830 using Tapatalk

 

 

 

 

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