how best might DJK's proposed PP La Scala be realized?

[karlson3]

DJK (R.I.P.) came up with an idea for a simple push pull La Scala variant with given dimensions close to that of Peavey's FH1 W-bin.  I assume the inner woofer

would mount through an access panel like LS and the 2nd outer woofer ("top" in his discussion) on the back of the cabinet.   An access panel spaced from the 2nd

woofer couples the front of that woofer's cone to the shared doghouse back-chamber volume through the channels formed by the upper and lower ramp boards.

 

I wonder how far the top woofer's access door/cavity would have to be spaced from its cone to function properly?  

 

One goal of the design is to have a cabinet whose HF extension is high enough to meet a 1" format compression driver.

 

Using 12pe32, it probably would subjectively have less bass weight than K33 in LS - but assume would be quite responsive.

 

How well do you it would work in practice?   The beamwidth of a mouth that size is getting pretty narrow up high.

 

 

 

[Marvel]

He had one the was a slide in module that fit inside the  regular woofer chamber. I think it was one of the engineers Dennis worked with at Rockwell Collins who had the LS built with it. I'll dig a round for it.

 

Bruce

[Marvel]

This will work...

 

You need to save the pics, Freddy, they aren't on here.

 

[karlson3]

Many thanks  - I get the idea that the way shown in DJK's sketch was expected to play higher than the easier to retrofit PP plenum  - ?  Did you figure out if the University Classic throat section could be cut accurately for a modest fee *and shipped )? - I know the Classic doesn't go "low" by today's standards but would expect it to "sound good".

[Marvel]

The pieces my son cut were perfect. We would have to cut a few more to make sure the whole throat came out right. He might get to this. @Invidiosulus  We've both been busy, but that's what we thought of offering sonce it's the crazy cuts.

 

I have some mwm bins to pick up. If my wife and I decide they are too bigh, I'll get back to the classics.

 

Bruce

[zobsky]

This is what he had in mind ( a plenum with pairs of PP woofers to replace the single K33

 

 

 

)

[glens]

Got a link to explain why front to back instead of face to face?

[Marvel]

7 hours ago, glens said:

Got a link to explain why front to back instead of face to face?

 

There is some discussion here, and links to other explanations. Here is an old post from Dennis (DJK) on the design,

 

http://db.audioasylum.com/mhtml/m.html?forum=hug&n=150851&highlight=ppsl+djk&r=&search_url=%2Fcgi%2Fsearch.mpl%3Fforum%3Dvintage%26searchtext%3Ddifference%2B222%2B299

 

The push pull action helps cancel non linearities of the divers, among other things, thereby lowering distorion. Sure miss Dennis around here and his passing is leaving a hole in the diy community. Sort of a sidetrack to the story, but I liked this posters post about Dennis (and this was a long time before he passed away.)

 

"DJK has been spot on with everything he's suggested over the years and he's an excellent engineer, one of the small number who's comments I take at face value as correct."

 

He had a phenomenal memory. I posted something around 2002 on here, related to equipment I borrowed from him in the mid '80s. I was wrong on the details, but he remembered everything. His brother is similar.

 

Bruce

 

 

 

 

 

[jwgorman]

I got to hear these in a custom pair of belles at one of DJK’s friend’s place. Very articulate. I too never really questioned his suggestions or recollection of specs. 

[Marvel]

28 minutes ago, jwgorman said:

... one of DJK’s friend’s place

 

Was that Dave?

[jwgorman]

Yes, that sounds right. I bought some Lascalas from him. 

[Marvel]

I only heard the name from someone at Rockwell Collins, now Collins Aerospace, who worked with Dennis. I had tried to find out more about Dennis' passing.

[jwgorman]

I actually learned about his passing here. He introduced me to Dave. I have no additional information about DJK’s death. Some great memories from the Audio Room days though. He could make anything: better, faster, tougher. 

I was an engineer at Rockwell and left in 2011. 

[Invidiosulus]

On 4/29/2019 at 4:29 PM, karlson3 said:

Many thanks  - I get the idea that the way shown in DJK's sketch was expected to play higher than the easier to retrofit PP plenum  - ?  Did you figure out if the University Classic throat section could be cut accurately for a modest fee *and shipped )? - I know the Classic doesn't go "low" by today's standards but would expect it to "sound good".

 

On 4/29/2019 at 10:43 PM, Marvel said:

The pieces my son cut were perfect. We would have to cut a few more to make sure the whole throat came out right. He might get to this. @Invidiosulus  We've both been busy, but that's what we thought of offering sonce it's the crazy cuts.

 

I have some mwm bins to pick up. If my wife and I decide they are too bigh, I'll get back to the classics.

 

Bruce

Later on this summer.