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Ported LaScala (Tribute to the late DJK)

THD+N said:
The ports firing to the back wall make a HUGE difference (at least in my room / corners). You can use less EQ/PEQ which will help IM & Group Delay. Only use what you need (EQ/PEQ) instead of too much.
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If I have the ports vented to a wall... not near a corner. Will I still get some positive impact? Also, how far would the cabinets need to be from the wall? My ports will be 4" x 9.5".
 
It's a wall-construction/material-dependent (and, within that/any of them, frequency-dependent) issue.

Not the answer sought, I know, but that inquiry approaches "dialing" for the application so the answers become case-specific.

Old European stone house, one end -- new constr gypsum-rock only, opposite answer.

It's radiation impinging on an interface, to be a d*ck...but all the same rules for refl / transm / absor apply. Depends on what your walls are.

Start at ideal True Audio Speaker Topics: Spatial Loading

You want a hip-shot? 2" min.

Two hard drives ago, I could've told you what I was working on, but...I made this for a very good friend of mine, viola / orchestra player and audio-lover when we were talking about these sorts of things.

I think this particular plot was gypsum and I was trying explain that some specs are about what's transmitted and others are the opposite but the single-point values are only of the most topical use, and basically to point-out frequency-dependence.

I threw a set of keys on it, scaled as best as I could to match, and he "got" it. FWIW.


wall_stc_vs_keybd_freqs.jpg
 
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DLStryker said:
If I have the ports vented to a wall... not near a corner. Will I still get some positive impact? Also, how far would the cabinets need to be from the wall? My ports will be 4" x 9.5".
Click to expand...
Keep 'em 2 feet off the wall indeed.
Another room gain rule-of-thumb regarding the expected impact: Room placement +3 dB, corner placement +9 dB (and even more gain as you get lower in the frequency range). EQ/DSP becomes a nice tool to have if there are clear unfavorable effects in your room. (Room Modes is another term to dig into..)

Question to continue my own quest: Did you design those port dimensions, or what source did you use?

P.s. You'd actually save yourself a lot of potential problems if you're finicky about getting the sound right by not porting the La Scala's, and applying a low frequency cut plus supplementing them with multiple subwoofers in mono achieve great sound across the frequency spectrum. But the fun here is squeezing more out of the La Scala itself of course. ;)
 
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Apreggiator said:
Excellent result! How did you tune the PR and which one is it? Asking because Ime they are hard to 'get right'.
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It's a Dayton Audio RSS390 alloy cone PR. Because the enclosure simulated to 28Hz, I had 4 weight discs on it initially for more extension. That proved to be too much, with slow, boomy bass. I removed all of the weight to get the in room performance as shown above. prior experience has not been that they're in any way "hard to get right," it's a simple matter of measuring, adding or removing weight as needed; the Dayton RSS-390 makes it quite easy, as the weight is mounted via 70g fender washers on a threaded rod and secured temporarily via a wing nut and permanently via a nylock nut, once the ideal weight has been determined. That said, not all passive radiators are created equal: the Klipsch PR used in the Chorus and Forte models doesn't have any allowance for adding weight, so it has to be affixed with hot glue or other adhesives which is a pain.


THD+N said:
The doghouse tuning frequency will vary with enclosure volume. An 8 cu ft enclosure will need different length port tubes.
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not only that, but the woofer FS and QTS will affect the sound as well. The K-33, for instance, has the FS to play that low, but its Q is insufficient to play below 32hz: the sound gets boomy, wooly and indistinct because the driver doesn't have adequate damping control.
 
Yeah, the K33 and it's variants are not the best in a ported enclosure. That is one reason the old Heritage Cornholio, ahhh, I mean Cornwall was deemed "boomy" or had too much bass a lot of times.
 
THD+N said:
Yeah, the K33 and it's variants are not the best in a ported enclosure. That is one reason the old Heritage Cornholio, ahhh, I mean Cornwall was deemed "boomy" or had too much bass a lot of times.
Click to expand...
I'd meant to test whether that was purely the function of the woofer, or if it was also a limitation of ports, but the passive radiator exceeded expectations so much that I lost interest.
 
A properly tuned bass reflex alignment sounds great. The port (ducted or otherwise) does not cause any audible anomalies except as high output levels with noise (chuffing) if the port area is too small.

Three reasons bass reflex alignments sound bad:
  1. Improperly tuned alignment (assuming port area is adequate)
  2. Wrong woofer (spec wise)
  3. Enclosure volume is not correct
 
This was the spec sheet from the drivers that DJK had manufactured by Eminence.
Basically a K43, and what seemed to be his preferred woofer in the many ported LS clones he built.
IIRC he ordered 100 of them.

IMG_4684.jpeg

IMG_7235.jpeg
 
Apreggiator said:
Keep 'em 2 feet off the wall indeed.
Another room gain rule-of-thumb regarding the expected impact: Room placement +3 dB, corner placement +9 dB (and even more gain as you get lower in the frequency range). EQ/DSP becomes a nice tool to have if there are clear unfavorable effects in your room. (Room Modes is another term to dig into..)

Question to continue my own quest: Did you design those port dimensions, or what source did you use?

P.s. You'd actually save yourself a lot of potential problems if you're finicky about getting the sound right by not porting the La Scala's, and applying a low frequency cut plus supplementing them with multiple subwoofers in mono achieve great sound across the frequency spectrum. But the fun here is squeezing more out of the La Scala itself of course. ;)
Click to expand...
THD+N gave me the internal volume dimensions and port sizes. 5 cu foot internal volume, Celestion FTR15-3070e driver, two 4" x 9.5" ports.
 
Gigantic said:
It's a Dayton Audio RSS390 alloy cone PR. Because the enclosure simulated to 28Hz, I had 4 weight discs on it initially for more extension. That proved to be too much, with slow, boomy bass. I removed all of the weight to get the in room performance as shown above. prior experience has not been that they're in any way "hard to get right," it's a simple matter of measuring, adding or removing weight as needed; the Dayton RSS-390 makes it quite easy, as the weight is mounted via 70g fender washers on a threaded rod and secured temporarily via a wing nut and permanently via a nylock nut, once the ideal weight has been determined. That said, not all passive radiators are created equal: the Klipsch PR used in the Chorus and Forte models doesn't have any allowance for adding weight, so it has to be affixed with hot glue or other adhesives which is a pain.



not only that, but the woofer FS and QTS will affect the sound as well. The K-33, for instance, has the FS to play that low, but its Q is insufficient to play below 32hz: the sound gets boomy, wooly and indistinct because the driver doesn't have adequate damping control.
Click to expand...
Excellent! Thanks. :)
 
PR or ports can work front or back. The back loaded devices would benefit a (possible) few dB's of room gain.
 
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