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Chris A

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

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How do I know if I need to use any stuffing, and or pyramid foam (for reflections) with my cabinet? My external dimensions are 25" wide (front), 17" deep with it being 13" wide in the rear, and 47" high. I am using 2 Emminence 15" Kappa C woofers with the EV DH1A compression driver (which is huge). The cabinet is 3/4" thick except for the front baffle which is 1 1/2" thick.

 

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I have not seen any reasonable tutorials for that other than "try and hear" method.

 

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My walls are also 3/4 inches thick so they will get excited by the woofers.

 

From what I have read DYNAMAT is very effective but really expensive and tuned for use with sheet metal so it seems that multiple layers wold be required for plywood.

 

I had read someone saying that the recycled tire rubber floor matting you see in gyms would make a good damper.  I have some of it here so I will try this first.  It is about 3/8 inch in thickness and is very heavy as if I want to add more weight to the cabinet.

 

Since my baffles are like sails in the wind I am attaching thick wool felt.  Again to placate me wondering if I shouldn't have done it if I don't.

 

For stuffing I am going to use the long fiber wool that has been used in all of my speakers for thirty years when I thought the transmission line was the answer.  There is no question (in my mind, at least) it is the best compromise stuffing.  I will not STUFF the cabinet.  I agree with Chris A that the back volume is not critical along with what is done with the volume; assuming that because of the small entry ports the reflected sounds we attempt to guard against with conventional speakers simply do not find their way into the output to any significant degree.  Speaking conceptually since I have no real idea.  

 

With a combination of some kind of heavy damper followed by THICK soft felt would probably be ideal taking care of wall damping and absorption without the use of stuffing but that much wool felt will cost lots of money so I am going to hope the wool, by itself, is plenty.

 

Luckily there are many ways to skin the cat and still have the skinned cat you always wanted.

 

RYTHMIK boxes assembled and attaching glue blocks for the 402 cabinets with the hope of having them assembled middle of next week. 

 

 

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My walls are also 3/4 inches thick so they will get excited by the woofers.   From what I have read DYNAMAT is very effective but really expensive and tuned for use with sheet metal so it seems that multiple layers wold be required for plywood.  

I had read someone saying that the recycled tire rubber floor matting you see in gyms would make a good damper.  I have some of it here so I will try this first.  It is about 3/8 inch in thickness and is very heavy as if I want to add more weight to the cabinet.

 

Since my baffles are like sails in the wind I am attaching thick wool felt.  Again to placate me wondering if I shouldn't have done it if I don't.

 

For stuffing I am going to use the long fiber wool that has been used in all of my speakers for thirty years when I thought the transmission line was the answer.  There is no question (in my mind, at least) it is the best compromise stuffing.  I will not STUFF the cabinet.  I agree with Chris A that the back volume is not critical along with what is done with the volume; assuming that because of the small entry ports the reflected sounds we attempt to guard against with conventional speakers simply do not find their way into the output to any significant degree.  Speaking conceptually since I have no real idea.  

 

With a combination of some kind of heavy damper followed by THICK soft felt would probably be ideal taking care of wall damping and absorption without the use of stuffing but that much wool felt will cost lots of money so I am going to hope the wool, by itself, is plenty.

 

Luckily there are many ways to skin the cat and still have the skinned cat you always wanted.

 

RYTHMIK boxes assembled and attaching glue blocks for the 402 cabinets with the hope of having them assembled middle of next week. 

 

 

 

 

 

The stuff I got was from Amazon, and it cost me about $120 to do 2 layers of each type for the full cabinet..  https://www.amazon.com/dp/B00URUIKAK/ref=cm_sw_r_cp_apa_i_cwfhFbT5NXHX9

 

https://www.amazon.com/dp/B07TKXMPH7/ref=cm_sw_r_cp_apa_i_qxfhFb33DCFAB

 

I hear you on the weight... I think mine are around 200+ lbs each.

 

 

Sent from my SM-G985F using Tapatalk

 

 

 

 

 

 

 

 

 

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I figured yours would be of similar weight.  Having a removable back makes the box much easier to deal with.  

 

That material is similar to what I applied to the horn.  It made a dig difference there and I only used a little bit since it was an experiment. 

 

So you really hear less resonance with this on the walls of your box?  Sure would make things easy in comparison to any other method I can think of.

 

Have one box assembled and get to see how everything fits inside today.  I had to make my boxes wider for the woofers to fit.  I think I will have to do some manipulation to get the assembly though the hole in the box.  I think the magnets are going to be closer to the walls than I had thought.  This will make it easier to use them as a brace but tricky to get in the box.

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I figured yours would be of similar weight.  Having a removable back makes the box much easier to deal with.    

That material is similar to what I applied to the horn.  It made a dig difference there and I only used a little bit since it was an experiment. 

 

So you really hear less resonance with this on the walls of your box?  Sure would make things easy in comparison to any other method I can think of.

 

Have one box assembled and get to see how everything fits inside today.  I had to make my boxes wider for the woofers to fit.  I think I will have to do some manipulation to get the assembly though the hole in the box.  I think the magnets are going to be closer to the walls than I had thought.  This will make it easier to use them as a brace but tricky to get in the box.

 

The carpenter missunderstood me, and that is why I ended up with a one piece cabinet. I think the way he did it was easier for applying the veneer though. I have not used any measuring equipment yet. I hope to have my new amp done soon so I can get Chris to tune ot for me. I think the bass I have with a cabinet is more than I have with the left and right without a cabinet. I will most likely have him do it the same way for the others,but I will have the rear panel access a little wider so I can get the woofers inside easier.  

Sent from my SM-T830 using Tapatalk

 

 

 

 

 

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Posted (edited)

There is no question your cabinets are beautiful and there is no question you can make them sound great with careful listening and DSP and stuffing adjustments.

 

My foolishness along with unbridled curiosity got the best of me today and I ordered one of those CELESTION AXI-PERIODIC drivers to hear what they can do.  Their ability to go lower than my JBLs makes me think that would be of great advantage in the crossover region.

 

I am very wary of ring radiators but very trusting of CELESTION engineering.

 

PARTSEXPRESS says I can try them for sixty days and if I think I should go back to the JBL I can return it.  They only had two left of which I am taking one.  So if I decide I love it I wonder how long I will wait for the second one.

 

Will let my opinion be known - should get them Tuesday.

 

My ALTEC friend thinks DANLEY has used these.  I have no idea.

Edited by rickmcinnis
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On 8/7/2020 at 3:27 PM, rickmcinnis said:

CELESTION AXI-PERIODIC

 

That is an interesting driver.

 

294-2142--celestion-axi2050-exploded-image.thumb.jpg.dff324f9d0eafb9a01e4b6c2c012d0f0.jpg

 

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Posted (edited)

Well, listened to one of them yesterday.

 

Did not want to open both boxes if I did not like what I heard with the one.

 

First impressions are very good.  If anything these are less resonant than the Truextent/2441s - less stridency on massed strings not as if the JBL were strident in any way, nowhere close, of course.  But after hearing the titanium diaphragm in the KLIPSCH supplied driver I was concerned.

 

CELESTION has tamed titanium.  With less EQ than was required before I get response to 22K - within a dB or so - I do not really want them flat up there.  I could have a rise if I wanted it.  Less EQ is required in general though the hump in the 1000 hz region is more pronounced but easier to quell. Nice shape.  One would think these drivers and the K-402 are very compatible.  One wonders if this is the driver Mr. Delgado will choose for his update of the JUBILEE?  He could not go wrong.

 

They really do go down to 300,  in fact real close to 200 - one could EQ them flat from 200 to 22k - but one worries if that would put stress on the driver and is not needed.  I like the idea of having a smooth slope instead of a cliff which is what the cutoff would be at 200 hz.

 

So I listened to one channel with the CELESTION and the other with the JBL,  I did not find the CLESTION channel calling attention to itself - always a good sign.  Listening to Sandy Denny on FAIRPORT CONVENTION's LIEGE AND LEIF her voice had more immediacy and dynamics from the CELESTION and a purity that I believe is due to the fact that I can get the woofer out of the way so much quicker with the CELESTION.

 

I like the idea of the FASTON connectors instead of those stupid spring loaded things.

 

There is a neoprene foam on the face which makes an excellent gasket.

 

They are made in the United Kingdom and not in China - a very pleasant surprise.

 

In my most unhumble opinion they are worth every penny of what is charged.

 

AND I have a screen right at the face of the driver so i will not be as confused about where to put the ports in the horn.

 

Now I wonder if I should place them further back from the CD or leave them just where Chris A placed his?

 

Tomorrow a report on stereo.  Hope my enthusiasm has not been overstated in haste.

 

And to find a buyer for the JBLs ...

Edited by rickmcinnis
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This looks to be a superb driver for a 2 way system. Stating the obvious but i couldn't help it.

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Fears are unfounded.

 

Having both drivers installed has proved they do sound very good.

 

What is interesting is how quickly they reveal polarity.

 

Wrong polarity comes across with a grey sound and when you switch it there is immediate color and dynamics.

 

My amplifiers are capacitor coupled so I use the output cap as part of the crossover.  I have a surprising second order distortion peak (based on REW and I am not sure how much to trust those distortion measurements) in the mid 400 hz range.  I wonder if I have too little capacitance and the distortion is due to the level being boosted there?

 

I do have a dip in the region which is being corrected.  I am hoping with more capacitance I will need to remove some output.  Will find out this evening.

 

The JBL Truextents have a sweeter sound in the top one and a half octaves - not sure if that is real sound or euphemistic sound.  The CELESTIONS, at this point, strike me as that rarest of things in the 21st century - an honest reporter.  Only time will tell.  At this point I am starting to wonder if this is the 21st century's first "classic" driver?

 

I do not think one can go wrong using these.  Now to get the MEH cabinets DONE!

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On 8/13/2020 at 1:04 PM, rickmcinnis said:

Well, listened to one of them yesterday.

 

Did not want to open both boxes if I did not like what I heard with the one.

 

First impressions are very good.  If anything these are less resonant than the Truextent/2441s - less stridency on massed strings not as if the JBL were strident in any way, nowhere close, of course.  But after hearing the titanium diaphragm in the KLIPSCH supplied driver I was concerned.

 

CELESTION has tamed titanium.  With less EQ than was required before I get response to 22K - within a dB or so - I do not really want them flat up there.  I could have a rise if I wanted it.  Less EQ is required in general though the hump in the 1000 hz region is more pronounced but easier to quell. Nice shape.  One would think these drivers and the K-402 are very compatible.  One wonders if this is the driver Mr. Delgado will choose for his update of the JUBILEE?  He could not go wrong.

 

They really do go down to 300,  in fact real close to 200 - one could EQ them flat from 200 to 22k - but one worries if that would put stress on the driver and is not needed.  I like the idea of having a smooth slope instead of a cliff which is what the cutoff would be at 200 hz.

................

...............

...................

And to find a buyer for the JBLs ...

 If you are interested selling the Truextent diaphragms please shoot me a PM at your leisure (with their history,  model number and a price)

BTW, (and I do not mean to pollute the original thread), you might very well be crossing this driver too low. Also, did you have the diaphragms professionally installed or use a tone sweep when they were installed (many of those drivers of that era are not self centering and may need to be evenly torqued and shimmed - in spite of what some others may claim).

-Tom

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2 hours ago, rickmcinnis said:

I have a surprising second order distortion peak (based on REW and I am not sure how much to trust those distortion measurements) in the mid 400 hz range.  I wonder if I have too little capacitance and the distortion is due to the level being boosted there?

 

I do have a dip in the region which is being corrected.

I've found that the degree of overlap of the crossover frequencies in MEHs is much, much different than traditional multi-horn loudspeakers.  I would recommend playing with that overlap and greatly increase it (there are no drawbacks like there are with multi-horn loudspeakers like lobing, etc.).  Just EQ the resulting on-axis flat again.  I do recommend that you also do some off-axis polar measurements for grins.  I recommend taking a measurement at 10 degree intervals (horizontal, then vertical).

 

Here is a distortion plot (in percent of the fundamental) of my center K-402-MEH with dual diaphragm BMS 4592ND as an example, on axis, nominally at 80 dB at 1m:

 

1448478832_K-402-MEHHarmonicDistortion().thumb.PNG.1aaa85f964f3697af50e7969c8c92b9f.PNG

 

The top harmonic is actually THD, not second harmonic. The second harmonic is the red trace.  All the harmonics are below the noise floor of the room in this plot.

 

Chris

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Chris, in your experience, what is a good crossover frequency for the MEH design? (2inch compression driver mated with a pair of 12 or 15 inch woofers). I get wary of running the compression driver too low. 

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Well, the answer may surprise you...

 

I run the natural response of the woofers and then compression driver, after flattening the SPL response of both sections individually.  Then I look at the natural crossing point of the two.  In the case of the BMS 4592ND, I believe that was 550-600 Hz. 

 

I use first-order crossover filters (effectively) to take out the 90 degree lead of the woofers to the compression driver.  Voila! Time alignment.  When I did this (and stopped trying to tell the compression driver and the woofers where to cross using the crossover and PEQs), all the performance measurements got better and it sounded better.  I simply trim off the response of drivers that is not needed using attenuating PEQs in order to keep the crossover interference band SPL response flat. 

 

Chris

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Posted (edited)

Thanks for your comments, Chris A.

 

I am not yet in MEH NIRVANA so my experience is purely with two separate horns.  With both the CELESTION and the JBL by themselves there would be a distortion peak somewhere in that range - even with the mic one meter from the horn.  Not a BIG peak but enough to stand out.  I thought it could be my amplifiers or something inherent to the horn.  I am using the First Watt SIT1 to drive the compression drivers and these have an output impedance of 4 ohms.  I wondered if that was the cause.  These amplifiers are capacitance coupled, one stage amplifiers so i have used the output capacitance as part of the high pass filter.  BUT I have found trying to use that as THE high pass filter does not work as well as instinct would suggest.  It is much better to use much more capacitance than the filter would call for.  There is much less distortion.  I know there is a best value but I have yet to find it.  At the moment I am using about 140 uF.  (edit: AND PEQs) When I would use 30 uF there was a surprising amount of distortion.  So much for my instincts.

 

Now that I have discovered these things will go much lower than the JBLs i am wondering if I should not re-think my port locations?  I will take measurements this evening of the CELESTIONs by themselves and I would appreciate your opinion.  The trade off is do I allow for a smoother roll off for the CELESTIONs or for the woofers?  I do like the idea of getting the woofers out of the way quicker.  I rarely listen about 95 dB and when i do i am obviously not going for the highest quality!  I am convinced the CELESTIONs are not stressed with the lower cut off.

 

Thanks for bringing up crossovers in general.  So are you not using first order filters?  I have no been able to tell if you have or haven't.  I know you posted some screenshots of your XILICA settings; I cannot find them again - of course if I spent enough time I would.   I have tried it both ways in my rudimentary setup and do see not hear much difference.  Though my heart and mind like the idea of using the PEQs only.

 

I tried my idea of using the recycled rubber gym flooring as an outside covering of the boxes and it will work very well.  Damps the wall and does not raise the Q.  I like the way the stuff looks and I have plenty of it laying about so I am glad to put it to use.  Figure i will use the GREEN GLUE to hold it in place though I suspect i will need the help of some screws at the top.

 

But the big quandary is whether to move the slots closer to the mouth since I do not need as much extension from the woofers.  I was planning on using a one inch width slot with a half circle on each end - 7 inches of length - whatever is needed to make 43 square centimeters.  Maybe slide them down about 1.5 inches from your position.  Just curious what your first thoughts are on that, please. 

 

AS always, thanks for this project!

 

 

 

 

Edited by rickmcinnis
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2 hours ago, rickmcinnis said:

I am not yet in MEH NIRVANA so my experience is purely with two separate horns.  With both the CELESTION and the JBL by themselves there would be a distortion peak somewhere in that range - even with the mic one meter from the horn.  Not a BIG peak but enough to stand out.  I thought it could be my amplifiers or something inherent to the horn.  I am using the First Watt SIT1 to drive the compression drivers and these have an output impedance of 4 ohms.  I wondered if that was the cause.  These amplifiers are capacitance coupled, one stage amplifiers so i have used the output capacitance as part of the high pass filter.  BUT I have found trying to use that as THE high pass filter does not work as well as instinct would suggest.  It is much better to use much more capacitance than the filter would call for.  There is much less distortion.  I know there is a best value but I have yet to find it.  At the moment I am using about 140 uF.  (edit: AND PEQs) When I would use 30 uF there was a surprising amount of distortion.  So much for my instincts.

I have never lost a compression driver due to overload, much less one that was damaged via a SS amplifier (especially one with 10 w output like your SIT-1).  I recommend removing the excess reactance and bi-amping using a DSP crossover.  The entire reason for using direct coupled drivers to amplifiers is to remove all the electrical reactance that can be removed.  If you are using passive crossovers or "safety blocking" capacitors in line, I recommend instead using DSP crossover and direct coupling--unless you're using a low-reliability tube type amplifier that tends to fail with voltage on the outputs.

 

2 hours ago, rickmcinnis said:

Now that I have discovered these things will go much lower than the JBLs i am wondering if I should not re-think my port locations? 

Did you include a picture or drawing of your ports?  The ports that I have detailed in the prototype K-402-MEH are more than sufficient to do the job without any added gnashing of teeth or wringing of hands 😉  I recommend using those first and foremost.

 

Chris

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Posted (edited)

Chris A,

 

I know it is impossible for you to keep up with what everyone here is doing but I have been using the XILICA boxes for almost two years.  I use an XP2040 for each channel.

 

The SIT 1s are for the compression drivers and a First Watt J2 turned into mono blocks with a choke input power supply drive the woofers.  The RYHTMIKs have their own amplifiers.

 

With a capacitance coupled amplifier you have no choice but to use a cap on the output unless you have a driver that can handle DC.  What I have found is that setting this capacitance for what the desired crossover point would require does not work as well as having lots more capacitance and using a PEQs to make the HP.  You get the crossover point you want but the distortion as measured by REW is MUCH higher - five times higher.

 

The SIT1 comes with over 1000 uF of electrolytic capacitance with a 5 uF bypass.  I have removed those and place caps at the speaker.  Much easier to adjust that way.  I have found that approx 130 uF works the best so far though I will slowly take away capacitance until the distortion goes up.  With the minimum amount of capacitance distortion as measured by REW goes up substantially.  This could be caused by numerous things.  I am not using any electrolytic capacitors at the moment.  Though some say there can be a good effect from using them even though this is considered apostasy by others.  One has to find out for themselves.

 

Still would like to know if you are using the first order slopes within the XILICA or only PEQs.

 

So if I take my response curve and then look at the REW EQ window and set the crossover to match my curve it says I have a fifth order Butterworth at 300 Hz.  I am not using the XILICA first order crossover - just two PEQs.  If I set the crossover higher (obviously) I could get a less extreme acoustic slope order and that is something I will try before I assemble the MEH.  Still have plenty of shellacking of the cabinets left to do.  I like sealing all surfaces of the cabinet and this takes time.  There are lots of pieces!

 

Since my temporary setup with the Edgar Seismics as lower midranges/mid bass are much happier with the 300 hz crossover it was good that the CELESTIONs allowed this.  Getting those 18 inches JBLs to go higher up in frequency requires lots of boost.  There is no question this is the best this temporary setup has ever sounded and I suspect COULD ever sound.  Having no experience with the CRITES woofers I have no idea how easily they reach 500 Hz.  I know you posted a raw response curve but i cannot find it.  Would you mind posting it again along with your current XILICA settings for the CRITES?  I would be very grateful, AGAIN!

 

Take care,

Edited by rickmcinnis
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