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

[rickmcinnis]

*

 

 

 

 

 

 

 

[Khornukopia]

42 minutes ago, rickmcinnis said:

I hear NO ill effects of using these drivers this low.  Every night I listen to them expecting to hear THE BIG FLAW and it has not appeared yet.  I love these drivers.

 

Cool. What is your hi-pass (crossover?) frequency to the Celestion compression driver?

[rickmcinnis]

-

[rick mcinnis]

Another thing I wanted to suggest to those about to put holes in their K-402s:

With a strip of paper  - mark it at 9 & 15/16 inches this will be ever so slightly large but is a mark on the yardstick - for the obsessive 9 and 59/64ths is even closer!

 

Use card stock.  Connect the two ends with some tape. You can then easily see where you are with your port.

 

There can be an advantage to putting an angle on the port.  I am going to try this - to have it continue the 45 degrees I want for the baffle.  Not there is a chance in hell of me getting that with any consistency.  I am not skilled with a router and my extra layer of baffle towards the mouth precludes being able to use one well.  I feel certain getting close is all that is needed.  Lots of barrel sanding bands are on hand along with sandpaper.

 

Draw a "circle" around the port -.75" out - (the thickness of the baffle in this case) to see where you need to finish up.

 

I am thinking about, for the sake of curiosity, of going ahead and cutting the holes in the other K-402 while it remains just a high frequency horn to hear and measure what happens.  I can use a sheet of paper with a blob of MORTITE on the back until I am ready to install in the second box.  It is finished but needs to be shellacked and that will take two weeks.

 

I know I will lose the frequencies in that part of the horn but want to see what happens above that.

 

Main motivation is go ahead and do it while I still remember what i did right with the first horn.  Using the epoxy to repair is easy but it does take lots of time to allow it to dry before adding a subsequent coating.  I am concerned that putting it on too thick, like BONDO, is a bad idea.

 

With hopes of helping someone not repeat my mistakes ...

 

Take care,

Edited September 3, 2020 by rick mcinnis
addition

[rickmcinnis]

-

 

 

[rickmcinnis]

*

 

 

[Lbk]

What size are ports, they look small. Didn't Chris suggest something like 2 in by 9.5 inch.port?

[rick mcinnis]

NPBK402 - I hope I got that right.  When I went back to find your name my note was lost so I have to start again.

 

Wondering what you did for stuffing your cabinets?

 

Finally was able to make a test fit of the whole assembly and the width of the hole I made is one inch too narrow.  I do not think I would want to make the hole one inch wider so having to make a one inch notch for the woofer magnet to slip by was a pain this far along but that is the glory of DIY.  Never sure whether to classify it as surprise or learning.

 

I hope the ports are not too small.  They should be 1/10 of the driver's SD.

 

Chris A made his more oval and mine are longer and approximately two inches wide.

 

All four RYTHMIKs are working with the one channel of the temporary lummox speakers and they are very fine. I had used three for a couple of years but installing number four made all the difference. Whether they have anywhere near the impact of the tapped horns I have no idea but the bass has great tone and just appears and dies away instead of making their impact noticeable.  This system is only for music and the RYTHMIKs will get as loud as I will ever need them to with very low distortion to my ears.  At 95 db the REW distortion graph shows less than one percent to below 20 hz.  It does sound that way - but that is one of the concerns with using REW - do we hear what we see?  Something i try to stay on guard for,. Plus I still am not sure how much faith one can have in those measurements.  I figure like all of the rest they are relative to each other, never absolutes.

 

Two of these are the "stands" for the K402s - the whole assembly will be in the corners of the narrow wall of my room.

 

Hoping this weekend to have one working and will post raw responses of the drivers.  If not this weekend then next weekend.

 

Then to begin in earnest on the right channel.  All of the woodworking is done - just the finishing and the port cutting and finishing.

 

Another thought for those who will try this - I am thinking the second one I will not use a hole saw.  I had used a Forstner bit on both the baffle and the horn.  I am thinking one might be better off drilling a hole and then using a jig saw to make the raw hole and then grinding away to get the final.   I found using a jig saw blade in the jaws of a VISEGRIP pliers made for easy cutting between the hole saw holes and now think it would be easier to just use this contraption to make the whole thing   (no pun intended)  You can go slow but I bet the process will take half of the time of using the Forstner bit since it would get too hot and melt the plastic so You ahd to wait for it cool  down.  This concerns the K402.  For the plywood baffle I will use the jig saw.

 

One thing for sure, as Chris A has state; with the magnificence of the K402 horn one can probably not go wrong with this.  I continue to marvel at how damned good it is.  I also have to say, with nothing other than my old JBL to compare it to - but the CELESTION Axi Periodic is exceptional.  Massed strings are simply electrostatic if not better in tone.  The highest frequencies measure up to REWs limit of 24kHz - that is the limit imposed by my setup. Overtones on cymbals are there in the right proportion and they sound like cymbals and not a PING sound like the absurdly expensive FOSTEX T500s which were about the dumbest things I ever bought.

 

I have found that using the high and low shelving filters in xilica allow much smaller level adjustments and this eases the effect they have on adjacent filters.  At the same time they do add an element of surprise, too, since they interact with PEQs differently than you might expect. Differently that how PEQs interact with each other.

 

Sorry,  I had lots to say

 

Take care,

 

 

[NBPK402]

NPBK402 - I hope I got that right.  When I went back to find your name my note was lost so I have to start again.   Wondering what you did for stuffing your cabinets?  

 

 

I have not stuffed my cabinets yet. On the first one I used a dynamat type marerial and a soundproof material. On the 2nd one I have only placed a few squares of the soundproof material, and in the one that is in the shop the cabinet is being made thicker, and will be a rectangle the same size as the horn when viewed from the front. This will be the center channel, and will be on top of my 90" wide AV rack. The center will be laying like most people have their k402s...not like my left and right which are vertical. I am going to be trying some sheep wool on the center channel, and also I am going to try some bracing inside all of the cabinets.  Now on the first one the bass is about 5db more than on the one with only a few pieces of soundproof material inside. We will see how the center is since it will be 9" shorter, but also a full rectangle... the left and right have angled sides going from 24" to 12". 

How high are your stands? I am thinking of making some stands to bring the left and right channels up to the the height of the center channel, or angling them (not sure if I can angle enough without becoming unstable). I will be trying some diy stands that will match the height of the center channel on the AV rack. I am doing this because my left and right channels are too low with our current seating, and most likely our new seating will be at least the height we are currently using. I am also curious how raising the speakers will effect the bass...right now, the bottom of the horn is 9" off the floor, and the speakers are within 2' of the rear wall, and side walls (corners).

 

Even though mine are not tuned completely yet due to us stopping when we had problems with consistent measurements, and my changing of the gain measurements on the amps (to try and get the levels were we wanted them). Now I have Icepower amp modules with no gain controls and we are ready to proceed when Chris is ready. I think he is waiting until we get the center completed so we can do them all at once...which is fine with me. I have to say that last night I listened to some master recordings on Tidal and I was very impressed as to how good they sound, and cannot even imagine how much more revealing they will be once we have them fully tuned.

 

Sent from my SM-T830 using Tapatalk

 

 

 

 

 

 

 

 

 

[rick mcinnis]

That is interesting as always!

 

I am a believer in the wool and will have this as a low density stuffing but wonder about the walls?

 

I have used good sized blobs of modelling clay on the walls which does reduce the resonance.  I figure a side benefit will be where I place the rockwool sheets (cut to size) this will give some space between the rockwool and the cabinet side.  Nothing but speculation at this point! But that is how I plan to begin. With the 3/8 inch heavy rubber gym flooring on the walls I am hoping audible contributions from the cabinet will be minimal.  There will be a block of some kind between the woofer magnets and the side walls - that will be it for bracing.  The assembly will connect with the bottom of the cabinet just to take the weight off of the horn.  I will not do this for the top so there is no vertical bracing, only mass.

 

The boxes for the RYTHMIKs have the same dimensions as the K402 box - 33 inches wide x 23 inches deep - the boxes are 22.5 inches tall.  They may have some concrete pavers placed between them and the K402 box (which is 45.5 inches tall) if I think the K402 is too low.  I would rather use those concrete pavers on top of the K402 box.  One way or another there will be pavers placed on top - that is what will be used to damp the top panel.  The bottom should be damped just fine by the sub box's top and the cabinet's weight upon that box.  The boxes are very heavy but with the backs left off I can put the bottom on the sub and them lever it up straight with help.

 

These dimensions create a box of more than double the correct volume for the RYHTMIK woofer so there is a v shape for the side walls and about 200 pounds of sand are used to fill this space.  These will make a very sold stand for the K402s.  

 

Another interesting thing about using the xilica - at this point with my BIG MONO setup I am putting both left and right outputs from the DAC into the two channels of the xilica - I do not have that many mono recordings so something was needed.  This was easy and very effective. Frrst thing you notice is it is louder this way - I guess 3 dB louder but ti sounds ore than that.  Only makes sense but it took me by surprise.  I am not overloading the output stage.  I think it is best when the one green LED is on most of the time =- NOT for the woofers of course.

 

A simple Lpad attenuator at each amplifier input allows one to keep all of this in balance - without the attenuators, even before mono, the output of the xilica would require setting the volume control at less than -15 dB which does not seem ideal to me.  I am using the MATRIX Sabre DAC at full output.  I figure there are enough level controls as it is.  Obviously I am using the xilicas for all control purposes.

 

xilicas' can have their episodes.  The one box I am using will no longer allow me to enter numbers.  This caused me alarm since I worry that since they are sounding so good I hate the idea of taking a chance reinstalling the firmware.  THEN I discovered what those buttons do on the bottom of the screen.  I now no longer care about having the ability to enter numbers.  The buttons are easier to use.  I am usually more curious than this.  I have had them almost two years and am just now discovering what they are for.

 

One interesting thing, since I have found that polarity is important to get the best possible sound one can only change one channel's polarity at a time.  With mono recordings there is close to absolute silence as one would expect but with stereo recordings it depends. ii figure when the phase has only been reversed in one channel we get a real idea of how much stereo information there is.  So far, on ALL pop, rock and jazz recordings there is mostly cancellation.  Lots more remains than with a mono recording; there is audible output.  With most but not all orchestral recordings there is 3 to 6 db less than both channels being in phase.  I have not looked at the RTA analyzer when doing this so those numbers are a very imprecise guess. But I would tend to believe this marks a STEREO recording.

 

One thing about listening to one main loudspeaker and four subwoofers scattered about the room is how good it actually is.  Getting the bottom octave close to right has a tremendous amount to do with what we perceive as spaciousness.  I could live with it if i had to.  The experience is more intimate in that all of the sound is plainly coming from one source and it is good at revealing small details since everything is concentrated.  Once you listen for about an half hour it is amazing how the brain starts filling in the blanks and the longer you listen the bigger the sound that is perceived.

 

I wonder if this would be anywhere as enjoyable with anything but a K402 horn.?  I doubt it.

 

If one cannot afford two of these I know I would rather listen to one of them than a equally as expensive stereo setup.  Certainly a path to consider - start with mono and add the second channel as finances allow. 

 

Luckily I am a stereo guy and can be happy with two channels.  I heard Bill Gaw's monster system so I know how good home theater (multi channel) sound can be but I could never afford all of that stuff nor have a room to place it in.  

 

Take care,

 

 

[NBPK402]

I have some Roxul r60 rockboard too...I guess 8 could measure and then put it in the cabinet, but I wonter about it chunking and landing inthe woofer baskets. Are you going to cover it with AT fabric or something too?

Sent from my SM-T830 using Tapatalk

[rickmcinnis]

*

[rickmcinnis]

 

NBPK402,

As far as how i plan to use the rockwool in the cabinet - I am not sure what brand I have - I got from a company selling acoustic devices here in Atlanta. 

 

I do not find the stuff to have any tendency to chunking.  It is plenty sturdy.  I will use it in an "edge on" configuration with the idea that i will be using all of the material as an absorber - none of the pieces will be against a flat wall and I will not be using that much or it.  No more than a 2 x 4 foot sheet for each cabinet.  Of course, this will be cut up.

 

I will be suing wool between it and the woofer cones and am hoping the wool will catch any rockwool dust.  Being in the fabric business it would be very easy to cover it with something if I find that to be necessary.  If anything I would put a fabric covering around the woofers and let the dust fly within the cabinet.

 

Take care,

[rickmcinnis]

*

[rickmcinnis]

*

[Chris A]

20 minutes ago, rickmcinnis said:

Maybe Chris A mentioned this but an easy way to find a smooth crossover region is to use the global EQ to make what you have flat - then measure the response of each driver and then remove the global filter, measure again and mimic the response of the Global EQ'ed response.

You might also experiment with increasing amounts of crossover overlap.  In an MEH, that overlap actually is good (surprisingly) since there is no lobing from the single horn aperture, and all the output between the woofers and compression driver get fully summed within the horn aperture, leading to a homogeneous phase exiting the mouth of the horn. The increased crossover overlap can be used to fill in any extreme off-axis polar losses in the crossover region from the woofer thru-ports subtracting from the full horn wall reflections.

 

Chris

[Chris A]

37 minutes ago, rickmcinnis said:

I can only hope others will give it a try.  A speaker for music lovers in every parameter of music performance.

Me, too.  I've been impressed by the sound I hear, and not so much by Beranek's law. 

 

I assume that there will be further  improvements found over time and tricks to make the fabrication and assembly easier, as well as dialing it in.  I've tried to stay away from this thread to encourage those discussions.  

 

I only caution those who would make large initial changes their own K-402-MEHs in the area of the woofer port (the "off-axis" ports) location, size, and remaining horn wall areas between the ports on each wall.  I recommend doing Hornresp and even perhaps even some boundary element modeling (BEM) simulations (if you're able) before making large changes in that particular area.

 

My guidance on my prototype came from careful study of Danley Synergy horn off-axis woofer ports. I was clearly very lucky in my first attempt by "staying inside the lines" in that particular area.  In my measurements, I could see that making a large mistake in that area would have prevented a successful outcome.

 

Chris

[NBPK402]

I have a little dilemma... I was going to put the center k402 on top of my 29" tall rack (sideways), but then my 86" tv would have to go on top of it. The tv looks like it is at a perfect height on top of the rack. I think I can rearrange the equipment and put the k402 in the center angled upward... Has anyone any experience with the speaker being on the ground, and angled up toward the mlp vor the center? Our MLP is about 12' from the rack front.

 

Sent from my SM-T830 using Tapatalk

 

 

 

 

[Khornukopia]

18 hours ago, NBPK402 said:

Has anyone any experience with the speaker being on the ground, and angled up toward the mlp vor the center?

 

Forum member @Cantilope had posted this picture about his MEH center speaker a few years ago, and he was happy with the sound of his system.

 

[NBPK402]

Thank you! Now I know it will work out nicely. I should have my center by next week...just waiting on the casters to raise the rack up 6 more inches.

 

Sent from my SM-T830 using Tapatalk