DIY La Scala mid upgrade options

[No.4]

I decided to take the first step and make a pair of baffles for the k401s. Tomorrow I will mount them to the horns and experiment with their distance from the front of the low frequency horns. I will do the same with the tweeters, though they will need a separate "simple" mount.

Bubo, the kappas I have are 4ohm.

Moray, I invested in a section of 1 1/4 sch40 this afternoon...even if the baffles are a significant improvement I am very intrigued by the karlson. I will begin working on these this week!

This is why I chose this design, so many possibilities!

Edited November 3, 2015 by No.4

[moray james]

I decided to take the first step and make a pair of baffles for the k401s. Tomorrow I will mount them to the horns and experiment with their distance from the front of the low frequency horns. I will do the same with the tweeters, though they will need a separate "simple" mount.

Bubo, the kappas I have are 4ohm.

Moray, I invested in a section of 1 1/4 sch40 this afternoon...even if the baffles are a significant improvement I am very intrigued by the karlson. I will begin working on these this week!

This is why I chose this design, so many possibilities!

Good for you but I strongly suggest that you experiment with some paper first untill you have the profile that you like best. I use photo copy paper the cheap thin kind or cheap 1/4" graph paper or cheap notebook paper they are thin easy to use as I said they store no energy. I use some thin wire from a long twist tie I burn the paper off to make a hoop to keep the paper round after it is cut. Paper is not only cheap it sounds good too. The easy way to make K-Tubes is to have a form tube to wrap them on which needs to be the just about the same diametre as your driver mouth I.D. Good luck. Have fun. Best regards Moray James.

[JohnA]

 

I would first try a baffle for the current two horns and also have the tweeter with the long dimenton vertical

 

I would not have thought that the baffle would make that big of a difference. With a hand on the outer flare of the horn during offending passages there is little to no vibration and no movement, however it would not be difficult to route a few panels to experiment with this.

 

 

Thank you very much!

 

The K-400, and likely the K-401, doesn't reach it's design cut-off frequency without the baffle.  My memory says that cut-off is 273 Hz, which is not the recommended 1 octave below the crossover frequency.  Undersized horns exhibit ripples in their amplitude response as they approach the cut-off frequency.  Your harshness may be partly the ripples and the baffle will reduce them. 

[longdrive03]

Excellent build!!!

[No.4]

Excellent build!!!

Thanks!

Last night I mounted the horns to the baffles and initially set up the tweeters on the the front of the baffle, centered and flush. I then listened for about an hour to tracks that had harsh passages. The baffles do indeed tame the mids considerably. They are not "perfect" but there is a huge improvement! Then, as seen in the photo below I fabbed some tweeter stands and on the recommendation of Chris A and marvel I moved the tweeters back about 17" from the front of the baffle. The effect was considerable. The sound stage definitely opens up and gives the room more depth. The tweeters seem to lose some of their analytical edge and the speakers as a whole sound more musical. (I try not to use subjective terms, but that was my observation) The combination of the addition of the baffle and the new tweeter placement changed the sound the speakers in a huge way. I need to listen some more and keep playing with the tweeter placement.

Moray, I have printed a few curves for the k tubes and found several threads on the topic. I may dig the old Mac out of the closet and draw a few curves with illustrator, should simplify the process. when you tried the single cutaway versions did you mount them horizontally, or at an angle?

Edit. I also plan on adding a panel above the k401 below the tweeters. I am curious to hear what effect it may have.

Edited November 5, 2015 by No.4

[Marvel]

I also plan on adding a panel above the k401 below the tweeters. I am curious to hear what effect it may have.

I can't see the tops of the LS whhen sitting down, but tried carpet scraps and other materials to see if i could hear a difference, but ig didn't seem to matter.

Bruce

[No.4]

I also plan on adding a panel above the k401 below the tweeters. I am curious to hear what effect it may have.

I can't see the tops of the LS whhen sitting down, but tried carpet scraps and other materials to see if i could hear a difference, but ig didn't seem to matter.

Bruce

 

Do you have the top panel above your mid horn? I am curious to see if any of the high frequency program is lost behind the baffle when seated. How far from the front of the baffle is your tweeter?

Edited November 5, 2015 by No.4

[Bubo]

 

I also plan on adding a panel above the k401 below the tweeters. I am curious to hear what effect it may have.

I can't see the tops of the LS whhen sitting down, but tried carpet scraps and other materials to see if i could hear a difference, but ig didn't seem to matter.

Bruce

 

Do you have the top panel above your mid horn? I am curious to see if any of the high frequency program is lost behind the baffle when seated. How far from the front of the baffle is your tweeter?

 

 

 

A possible simple test is tape a piece of string halfway inside the horn lens, and pull it snug to see if it clears the baffle without bending.

 

"The higher frequency sound waves have a shorter wavelength and thus don't spread out as rapidly. For this reason, the resulting directivity of these devices is far higher than physically possible with any loudspeaker system."

 

https://en.wikipedia.org/wiki/Directional_sound

 

If we are going to be moving the tweeters way back to align with the mid drivers, should we get longer lenses to control the diffraction so we are not hitting the tops of the cabinets?? Lenses also have their own baggage and reflections may become and issue with other effects.

[Marvel]

Mine were standard

I also plan on adding a panel above the k401 below the tweeters. I am curious to hear what effect it may have.

I can't see the tops of the LS whhen sitting down, but tried carpet scraps and other materials to see if i could hear a difference, but ig didn't seem to matter.

Bruce

 

Do you have the top panel above your mid horn? I am curious to see if any of the high frequency program is lost behind the baffle when seated. How far from the front of the baffle is your tweeter?

Mine were standard LS, so there is a top on the cabs. I made a baffle to mount the tweeter in, which rest on the top, slid to the back of the cab.

[moray james]

Excellent build!!!

Thanks!

Last night I mounted the horns to the baffles and initially set up the tweeters on the the front of the baffle, centered and flush. I then listened for about an hour to tracks that had harsh passages. The baffles do indeed tame the mids considerably. They are not "perfect" but there is a huge improvement! Then, as seen in the photo below I fabbed some tweeter stands and on the recommendation of Chris A and marvel I moved the tweeters back about 17" from the front of the baffle. The effect was considerable. The sound stage definitely opens up and gives the room more depth. The tweeters seem to lose some of their analytical edge and the speakers as a whole sound more musical. (I try not to use subjective terms, but that was my observation) The combination of the addition of the baffle and the new tweeter placement changed the sound the speakers in a huge way. I need to listen some more and keep playing with the tweeter placement.

Moray, I have printed a few curves for the k tubes and found several threads on the topic. I may dig the old Mac out of the closet and draw a few curves with illustrator, should simplify the process. when you tried the single cutaway versions did you mount them horizontally, or at an angle?

Edit. I also plan on adding a panel above the k401 below the tweeters. I am curious to hear what effect it may have.

When I used the single cutaway version K-Tube I used them parallel to the floor centred at seated ear height with the solid section of the tube facing the outer walls adjusted so that from the listening position I could look directly down each tube, you can play with the toe in to your liking. Best regards Moray James.

PS: you should try rotating the tweter so the long axis is vertical as that is the way it was designed to be used it is a diffraction horn. Give it a try I expect you will like it better that way. I run my K79 (I replaced the factory H3 lens with the K79) that way on my Heresy3.

Edited November 5, 2015 by moray james

[Marvel]

Here's a pic of tweeter up top. It's an eminence apt150, which when purchased was the same driver as Bob's CT125, with the Eminence horn. This would also work with the k77/ct125 mounted.

Bruce

Edited November 6, 2015 by Marvel

[No.4]

 

 

I also plan on adding a panel above the k401 below the tweeters. I am curious to hear what effect it may have.

I can't see the tops of the LS whhen sitting down, but tried carpet scraps and other materials to see if i could hear a difference, but ig didn't seem to matter.

Bruce

 

Do you have the top panel above your mid horn? I am curious to see if any of the high frequency program is lost behind the baffle when seated. How far from the front of the baffle is your tweeter?

 

 

 

A possible simple test is tape a piece of string halfway inside the horn lens, and pull it snug to see if it clears the baffle without bending.

 

"The higher frequency sound waves have a shorter wavelength and thus don't spread out as rapidly. For this reason, the resulting directivity of these devices is far higher than physically possible with any loudspeaker system."

 

https://en.wikipedia.org/wiki/Directional_sound

 

If we are going to be moving the tweeters way back to align with the mid drivers, should we get longer lenses to control the diffraction so we are not hitting the tops of the cabinets?? Lenses also have their own baggage and reflections may become and issue with other effects.

 

From the seated position the driver is not obstructed. I also re-mounted the tweeters so they are vertical. My initial response to this change is that the highs are little more clear and the soundstage is a little more accurate. This will require much more A to B listening. The best change so far has been the change in location of the tweeter. Positioning it above the mid driver has had a huge impact. This is something that every La Scala owner should try. It is a five minute mod that is totally reversible.

[Full Range]

That's a very similar tweeter position to my setup

Edited November 6, 2015 by Full Range

[JohnA]

If you will examine the graph in the lower right of this attachment, from an E-V brochure, you can find the polar response of the T-35 in both long axis horizontal and vertical.  The Horn *is* a diffraction horn, but the effect exists only below 5000 Hz and the beam width is wider with the long axis horizontal above 5000 Hz.  Since the crossover point for the Heritage series using this tweeter is 6000 Hz, Mr. Paul had it right. 

Edited November 6, 2015 by John Albright

[Chris A]

John, that's an interesting description.  My understanding of diffraction horns is that they need the diffraction as the frequencies increase, not decrease.  The tendency of a horn is to beam at high frequencies--if you catch my drift.  If the diffraction slot is too far away from the throat, then it doesn't become effective in the frequency region where it's needed to spread out the higher frequencies, and the slot loses its function, except as an impedance bounce point for internal (evanescent) modes.

 

The reason why diffraction horns sound like frying bacon is the so-called "cut-on frequency" where the higher order modes/harmonics of sound in the horn begin to exit the horn's mouth at a 1/4 wavelength equal to the diameter of the throat).  In the case of a tweeter, however, not many people can hear above 20 kHz (at the turn-on of the exiting HOM harmonic frequencies, that is) so the tweeters sound okay to our ears--but probably not to the dogs and cats in the house...if they could tell us. 

 

Chris

Edited November 6, 2015 by Chris A

[JohnA]

I have the ramaining pages of the brochure, if you want them.  They bounced around the Forum a few years ago. 

[Chris A]

Yes, if you've got links to them on the forum handy.

[Guest David H]

Since the crossover point for the Heritage series using this tweeter is 6000 Hz, Mr. Paul had it right.

 

On which speaker Vertical Cornwall or conventional.

 

Looks to me that it makes little difference how it is mounted.

 

Dave

Edited November 7, 2015 by GotHover

[Marvel]

He got it right by saving a bunch of wood on the LS, Belles and Khorns. Wouldn't save any on the Corns either way.

Bruce

Edited November 7, 2015 by Marvel

[Guest David H]

He got it right by saving a bunch of wood on the LS, Belles and Khorns. Wouldn't save any on the Corns either way.

 

It was a Joke, don't get in a twist.

 

My point was the T35 works comparably in either vertical or horizontal configurations. I suspect Mr. Paul knew this well, and that's why it was used in both configurations.

 

 

 

Dave