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Dave A

Super MWM

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8 minutes ago, jwc said:

Dave.  Just a reminder....I like your curve.  Just adding points for thought.

 

Full reflector would look "something like" this: 

 

Not saying do it......just a point

I think Dave made the backs removable, so he could add more material to them, which "might could" improve the higher end of the band by a few Decibels, in theory anyhow.

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11 minutes ago, jwc said:

Full reflector would look "something like" this: 

 

That would make more sense to me (just logic and nothing else), so the wave front wouldn't just bounce straight off the back and up the throat.

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400 ain't all that high, but as you move up in the spectrum sound waves want to turn corners less and less.  So it stands to reason 400 wants to turn less than 40 does.  I'd experiment with more diversionary tactics if it were me, if reasonably feasible.  Maybe even something kind of swoopy.

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3 hours ago, jwc said:

Dave.  Just a reminder....I like your curve.  Just adding points for thought.

 

Full reflector would look "something like" this: 

 

Not saying do it......just a point

 

 

 

 

Smwm-hack-01.jpg

The decision  process here was that I wanted to maintain expansion so that if I drew a circle where the 9.25" dimension from plenum end to back side there would be no reduction in  volume. The splitter could have been larger but I was not given or able to find info on what size was right so I guessed.

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So.  Tell us about the bass.  It has to be in your face.

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1 hour ago, jwc said:

So.  Tell us about the bass.  It has to be in your face.

Well my wife keeps telling me I need to turn the bass up and come in the house and feel the beat. Now you know how women misrepresent things like that but all kidding aside it is awesome. My purpose in hearing those big pipe organs has been accomplished. It is surprising how much bass I had been missing and the combination of Audacity and a horn capable of playing lower notes has been eminently satisfying.

  I had a pair of EV-TL440's which were good to 20hz. They were very fatiguing and in short order somewhat painful, These S-MWM's of course don't go as low but man are they fun. I find myself looking for  firework and lightning and helicopter audio and the clear sound and thump is amazing.

 

  I went by Cory's a while back and he demoed his Jubes with an x-box and  Star wars game. The thump of explosions was pretty darned good and the sound effects great. But they were like you were in the general area of the action and these S-MWM's put the booms two feet away.  You know you are invited to stop in if you are ever up here.

 

  I have a poor listening environment and I wonder what they would be like in a good one. Some day I am going to roll them to the big door in my shop, point them out and let them rip.

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10 hours ago, Dave A said:

Some day I am going to roll them to the big door in my shop, point them out and let them rip.

Yes, and with only 8 watts, they will do plenty of ripping at around 115 db!

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4 hours ago, ClaudeJ1 said:

Yes, and with only 8 watts, they will do plenty of ripping at around 115 db!

Yes, music for the whole valley. SO do you feel guilty yet about making me spend my money???

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Guilty?  Another emotion comes to mind as he awaits the royalty payments you're getting yet further behind on!

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7 hours ago, Dave A said:

Yes, music for the whole valley. SO do you feel guilty yet about making me spend my money???

Never. It was fun to be part of the evolution on your dime! But I do think you should try JWC's modification. I believe it would improve the high end of the woofer acoustically between 300-400 Hz. Now you know why I wanted you to make the backs removable.

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Scrolling back through this thread to reply to someone and I was thinking how hard it is to get information sometimes. I had discussed a splitter with the La Scala being bigger and having an arc to it with with corner rounds on the outside internal corners also figuring sound might behave like water and rounded transitions would create less "turbulence". Among those who responded the idea was it generally poo pooed and that is why I did not consider this for the S-MWM. I had also posted pictures of the splitter before install but I guess no one caught that to tell me other wise. There were also comments to the regard that PWK did not have splitters in the MWM and so they are not needed.

 

   So what I am doing today is trying to get definitive best practices for the splitter and the outside corners. Due to the size of the cabinet and the degree of difficulty in holding it all squarely in place I had to make the back to be glued in and change is not going to be simple or easy. I am willing to consider doing this is it will bring about significant improvement. I would like to hear from those with real practical design knowledge and or hands on build results they can tell me about that incorporated this kind of idea. It is possible to make this from say 1/8" formed aluminum and screw these things in from the front without removing the back. 

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Also a bump on what the lowest practical hz limit is on the 402+1132 combo. I have seen the literature on various drivers but asking for practical real user experience or tech advice from someone who knows.

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You could use modeling clay (what, about 20#?) and gradually build it all up, measuring sweeps as you go.  I've heard that can work for horn development.

 

Also, you could "track-thin-kerf-jigsaw-cut" the back panel out near its perimeter, mount it to a new panel and mount that back onto the box with screws.  (Just thinking out loud how I might spend someone else's time and money.)

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11 hours ago, Dave A said:

Scrolling back through this thread to reply to someone and I was thinking how hard it is to get information sometimes. I had discussed a splitter with the La Scala being bigger and having an arc to it with with corner rounds on the outside internal corners also figuring sound might behave like water and rounded transitions would create less "turbulence". Among those who responded the idea was it generally poo pooed and that is why I did not consider this for the S-MWM. I had also posted pictures of the splitter before install but I guess no one caught that to tell me other wise. There were also comments to the regard that PWK did not have splitters in the MWM and so they are not needed.

 

   So what I am doing today is trying to get definitive best practices for the splitter and the outside corners. Due to the size of the cabinet and the degree of difficulty in holding it all squarely in place I had to make the back to be glued in and change is not going to be simple or easy. I am willing to consider doing this is it will bring about significant improvement. I would like to hear from those with real practical design knowledge and or hands on build results they can tell me about that incorporated this kind of idea. It is possible to make this from say 1/8" formed aluminum and screw these things in from the front without removing the back. 

Since JWC and I are strong on the idea that potential natural ACOUSTIC improvement at the more critical 300-500 Hz. range by adding reflectors, thereby mating with the upper end, I would say hold off until you have exhausted all the improvements that can be made with PEQ FIRST! Then go back for a second look if those other things don't work for your ears. I think the curves you posted look very encouraging to going with the PEQ route with your Xilica.

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2 hours ago, glens said:

Also, you could "track-thin-kerf-jigsaw-cut" the back panel out near its perimeter, mount it to a new panel and mount that back onto the box with screws.  (Just thinking out loud how I might spend someone else's time and money.)

I had thought about cutting a square panel out of the back side that could be mounted back in with various sizes of deflectors. I really only need that section to be removable. The idea of a curve on the deflector on the backside and the inside corners to make sound "flow like water" with fewer ripple inducing disturbances is something I had discussed before but seemed to draw no interest or definitive answers. With limited knowledge but thinking practically about things it just seemed to me that sound could handle to some degree like water  or air flow and curved transitions would enable more uniform flow with fewer "eddies" in it causing audio problems. I see tons of sharp angular transitions in speaker cabinets though. I would think curved corners would also break up any standing wave problems these S-MWM's might have.   

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15 minutes ago, ClaudeJ1 said:

Since JWC and I are strong on the idea that potential natural ACOUSTIC improvement at the more critical 300-500 Hz. range by adding reflectors, thereby mating with the upper end, I would say hold off until you have exhausted all the improvements that can be made with PEQ FIRST! Then go back for a second look if those other things don't work for your ears. I think the curves you posted look very encouraging to going with the PEQ route with your Xilica.

Yes this is my plan. I might still pursue a better splitter or diverter  after I get things set with the xilica just to see. 

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Dave.

 

These are just suggestions..... you have a fine horn there.  I will admit, I haven't followed this thread closely as my work schedule is tough and I am absent from the forum at times.

 

You don't HAVE to do anything to the horn but having the system as a two way could create a challenge.   It's a lot to ask for the 1132 to play 300Hz all the way out.  400hz out....yes without playing at pro sound levels.  You could go that route and PEQ the the "small hole" in the response close to the XO point.  In your active crossover, you have a choice to try the PEQ as "full range" before the active XO or "isolated" after the XO to effect just the LF or HR.  Your active experts here can help with that.  

 

It's easy for the armchair critics to come out AFTER we see the FR curve.  If the final result did reach strongly to 400Hz, but you had big dips after 100Hz, I might suggest something to tame those.  

 

I'm not an expert, I just have some experience.  My opinion of reflectors in a non-sub folded horn design, is what I call a "full reflector" that isn't curved.  I'm certainly aware of the criticism of that route....I've heard them before.

 

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

 

 

 

 

 

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

 

image.thumb.png.fa20c527b57bcf17d8b5131c8713e566.png

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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

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