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Dave A

Super MWM

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4 hours ago, jwc said:

Remember, the reflector is an attempt to obtain "slightly more horn loaded material" after 300Hz.

 

image.thumb.png.fa20c527b57bcf17d8b5131c8713e566.png

Actually what I would do would be to open the cad file and derive precise dimensions and prebuild the whole thing and then make a removable panel on the back side which would allow me to change things around at a whim. By the way on the Edgar attachment I never had a page 13.

  This does make sense in that it does more uniformly continue expansion where the straight dumping from the plenum end to around the bend does not have that as is.

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2 hours ago, PrestonTom said:

Dave, My friendly advice is that you might be over-analyzing this. 

 

My memory is that an engineer from Klipsch mentioned that 1) some of the versions of the bass bin did have reflectors and it was later found that these were not necessary and were then dropped from the design. 2) that there are two views - either  thinking about the waveform traveling down the path as analogous to a "ray of light". This is the Bruce Edgar way of looking at things and hence the "need" for a reflector. In contrast, the other view is to think of the waveform as fluid in a pipe and the requirement is that the cross-sectional needs to continually expand. So with this view, the reflector is not necessarily needed. This later view was favored by a certain engineer at Klipsch.

 

Regarding the need to lower the crossover point: I think JWC is correct. Extending the bandwidth downward is asking quite a bit from the 1132 driver. Of course, this could be verified by some distortion measures if anyone is willing or able to make them. 

 

I think you are viewing your FR measures (with a low pass roll off at 400Hz or so) as a glass half empty rather than half full. It is fine to have a low pass roll off from the bass bin of 3-6 dB at the nominal crossover point. It simply becomes part of the net (overall) crossover. Although you may want to think carefully about the steepness of your crossover filtering. I saw nothing in FR plots that indicated a major problem. Yes, you will need to add a few PEQs to knock down some peaks but that is not a problem (I assume you will be using DSP, if not, I hope you consider that strategy). 

 

Good luck,

-Tom

Not analyzing as much as looking for best practices from people who have been there before. It is a shame there is no way to visualize sound waves as they propagate and see what works best. They have FEA software for many things now but I don't remember reading of any for sound waves and I expect the market of potential buyers is to small for programs being written for it.

  Really I am quite happy with the results but if there is improvement beyond electronic tinkering to be had I am interested. You never know until you seek the answers and at some point in time someone has to try it too. Sound propagation seems to be one of the fields that does not have specific rules laid down with proven singular best practices and so we see all the competing designs and no clear cut winner.

 I regard Paul as a genius having come up with what he did and I assume some math and lots of intuitive engineering insight to do what he did before computers and software was around.

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Those measurements, as has been said, already look pretty good. You always have to look at those and then listen to a LOT of music you are familiar with.

 

Bruce

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2 hours ago, Dave A said:

By the way on the Edgar attachment I never had a page 13.

 

Notice how the full reflector in this example squeezed out a little more after 300Hz...

 

image.thumb.png.786c24af18899fdf51ee85faf5f3e25f.png

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2 minutes ago, Dave A said:

before computers and software was around.

 

Even before electronic calculators!  Lookup tables and/or a slide rule!

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On 7/12/2019 at 9:48 PM, Dave A said:

I find myself looking for  firework and lightning and helicopter audio and the clear sound and thump is amazing.

 

Did you ever get a chance to download & hear my recording of Apollo 11 taking off?

 

Put that on 11 while eating your Rice Crispies & call me in the morning!!

 

 

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Yes I did and it does sound good. What was even better was a Japanese fireworks video I downloaded from Youtube. Fantastic fireworks and up to 48" shells so lots of boom which these do rather well if I must say.

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On 7/20/2019 at 6:55 AM, jwc said:

If you truly are interested in taking the back off and trying a reflector, I would be glad to help.   As Claude said though.....consider fiddle with PEQ first.  My suggestion there, would be to add a +PEQ to the LF after the 400Hz XO point.  Possible 350Hz PEQ +3-4dB.  You can tinker with the Q's and see the response.

 

jc

I agree with this from in incremental, procedural, point of view. But, I'm still curious as to whether the reflector would boost the high end. Remember that Klipsch evolved the MWM into a 4-way after initially doing a 2-way with a huge Gauss compression driver crossed at 400 Hz. Going 4 way with a conical midbass horn allowed for a very powerful 300 Hz. output, before PWK came up with the Quad K55-throat, which could be used for you to make a 3-way with YOUR own tweeter. According to an interview I had with Gary Gillum in 2008, he said that Quad Manifold had the greatest power density of any midrange driver he ever tested. also Keep in mind that those K55/Atlas drivers are designed to go down to 100-200 Hz. for a handheld pager!  That yet untried combination could end up sounding better overall since it would have greater angular dispersion above 8 Khz than just the K-402 while the Quad Manifold, full of K55's, would easily cross at 250-300 Hz. in the K-402.

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On 7/11/2019 at 2:59 PM, Dave A said:

I have a question in to Roy to see what the lowest safe crossover point for the 1132 is. I can't find any definitive answer for lowest crossover point on these and if someone knows I would appreciate finding out.

I normally don’t suggest going lower than 500 ha but that’s in a cinema setting. For home, I would say not below 400 but it ultimately depends on the all “requirement”. Don’t go deaf on me......

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On 7/20/2019 at 1:15 PM, jwc said:

 

Notice how the full reflector in this example squeezed out a little more after 300Hz...

 

image.thumb.png.786c24af18899fdf51ee85faf5f3e25f.png

I am a big fan of dr Edgar but I don’t consider sounds ways to be light rays. These reflectors serve to continue the expansion rate thru the turn. It’s really all about path length difference. This difference will determine where you will get the first null. 

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On 7/20/2019 at 11:01 AM, Dave A said:

Actually what I would do would be to open the cad file and derive precise dimensions and prebuild the whole thing and then make a removable panel on the back side which would allow me to change things around at a whim. By the way on the Edgar attachment I never had a page 13.

  This does make sense in that it does more uniformly continue expansion where the straight dumping from the plenum end to around the bend does not have that as is.

This drawing shows quite the negative expansion rate at the “reflector”. As you plot the expansion you must keep a zero to positive expansion rate thru the turn. Otherwise it will produce some distortion. Just my two cents. 

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44 minutes ago, Chief bonehead said:

I normally don’t suggest going lower than 500 ha but that’s in a cinema setting. For home, I would say not below 400 but it ultimately depends on the all “requirement”. Don’t go deaf on me......

500hz it will be. You are right to caution on going deaf. Since these arrived my wife complains she has to repeat herself. It is too easy to turn these up and I have had to get a DB meter to monitor things.

 

42 minutes ago, Chief bonehead said:

his drawing shows quite the negative expansion rate at the “reflector”. As you plot the expansion you must keep a zero to positive expansion rate thru the turn. Otherwise it will produce some distortion. Just my two cents. 

On my final plan I went with a circle drawn at the end of the plenum that would contact the sides and back and also the faces of the diverter figuring to keep the expansion rate as high as it could be. Is this a what you would consider a zero to positive expansion rate?

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40 minutes ago, Dave A said:

500hz it will be. You are right to caution on going deaf. Since these arrived my wife complains she has to repeat herself. It is too easy to turn these up and I have had to get a DB meter to monitor things.

 

On my final plan I went with a circle drawn at the end of the plenum that would contact the sides and back and also the faces of the diverter figuring to keep the expansion rate as high as it could be. Is this a what you would consider a zero to positive expansion rate?

Yes. 

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On 7/21/2019 at 9:57 PM, Chief bonehead said:

This drawing shows quite the negative expansion rate at the “reflector”. As you plot the expansion you must keep a zero to positive expansion rate thru the turn. Otherwise it will produce some distortion. Just my two cents. 

Good of you to respond, Chief. Just the fact that you did makes this piker/amateur horn designer happy for a moment.

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How far back on super MWMs can the K402s be positioned in active setup to compensate for delays using Xilica or DBX active crossovers?

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I would have thought you would use the actives to compensate for the delay, not moving the horn??

 

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6 hours ago, parlophone1 said:

How far back on super MWMs can the K402s be positioned in active setup to compensate for delays using Xilica or DBX active crossovers?

@Chris A ? I would think using with a Xilica you could adjust delays such that you could place the 402 pretty much where ever on the Super MWM that you would like. Even to the point of some of the energy bouncing off the top of the bass cabinet instead of going out into the room (which is probably bad).

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Well, since the Xilica can delay up to 650 ms per channel, that equates to 735 feet of set back of the K-402s that's available to you.  Practically, it means that if you can hear and see the K-402 in the venue from standing at the SMWM bin, you can correct the relative time delay on-axis.  (Large off-axis time alignment is another issue, however... 🙂)

 

Remember that the Xilica is a professional crossover, i.e., not a consumer device, so the issues of arena and stadium installation time alignments is very much a real application of that large value of delay capability that's available with the XP and XD series crossovers.

 

Chris

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So @parlophone1 we use the delay functions in the crossover to compensate for the positioning of of the drivers, we don't position the drivers to compensate for the delays of the crossover. I was a little confused by your question.

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It's generally better to place the mouths of all the horns near the same vertical plane, and correct the delays using a DSP crossover.  This will get you time alignment at large lateral off-axis listening angles, e.g.:

 

KPT-MCM-Angled-2.jpg

 

Putting the mouths of the horns at set back positions to match the acoustic centers of each horn/driver physically (à la Avantgarde Trio style) actually creates issues with horn mouth obscurations off-axis or excessive lobing within the sound field due to the exaggerated vertical and lateral spacing of the different "ways" of the loudspeakers. Also, the time alignment shifts as you move more and more off-axis.  This forces the listening of these type of loudspeakers on-axis, very much like older audiophile systems having a limitation of where you listen to them in-room:

 

header-trio-classico.jpg

 

Commercial cinema loudspeakers must have sweet spots as large as the auditorium seating that they cover--eliminating the archaic audiophile need for "sweet spot listening".  The only limitation is stereo listening, whereby in order to get a balanced phantom center image, you must be sitting on centerline between the left and right loudspeaker arrays (which is a limitation of stereo recording and playback itself).  In multichannel soundtrack and music playback, loudspeakers designed for commercial cinema must make every seat in the house a viable listening position, locking in the center of the acoustic image using loudspeaker arrays of 5.1+ loudspeakers.

 

Chris

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