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djk

PPSL Vented LaScala

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exciting and interesting stuff dennis. get well soon! T

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Parts Express sells some 4Ω Visaton 8s that are similar to the SEAS, treated paper cone, rubber surround, about $45 each. The mass corner on the Visaton is similar to the K33 so it should work in the LaScala, I will have to run it in Hornresp to double-check. The Visaton drivers lack the bucking magnet and shield the SEAS have, so the PPSL mounting plenum would be easier to construct.

If the Visaton drivers model similar enough to the K33 and work in the LaScala, if a person could overcome the size of the woofer access door in a Khorn, would the Visaton drivers mounted to a PPSL plenum work in the Khorn and lower distortion and would overall efficiency of the bass bin change?

post-38331-13819831277048_thumb.jpg

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The PPSL plenum should work in the Klipschorn too.

The efficiency with the Visaton would be about the same (maybe 1dB less), the distortion would be lower, the frequency response would probably not change. 90% of the frequency response is from the horn, and that is not changed.

The mass corner on the Silver Flute drivers is higher, they are more efficient, have a higher x-max (than the Visaton), and cost less. My next experiment may use them (I happen to have eight on hand for another project).

My friend Dave informs me the SEAS plenum has a buzz in it, out it comes for some additional bracing. He bought a SLM and a test disc, but may still be borrowing my analyzer for the weekend.

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OK, this is one of the coolest things I have seen in a

while, much thanks to djk and the forum for introducing me to this idea.

So here’s my question: if one were to do this in a La Scala,

how would the extended/ported doghouse play into it for extending the

bass? How would one calculate the size

of the chamber extension and ports, if they were needed at all? I am very curious about how the listening

tests go.

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How would you remove the drivers that are flush mounted facing into the box if you had a problem with one? Were they installed and the box built around them?

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It looks like the whole aparatus simply gets slid into the place where the original woofer is located, so the porting is the same and you just slide the whole thing out if you need to service.

Check out the pics on the first page.

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Thanks tigerwoodKhorns, but I was referring to the modification that I frequently see on this forum where the doghouse volume is increased by adding a 10" section at the bottom, and 2 ports are tuned to lower the bass cutoff to mid-30's. I was asking if and how that would be done with the 8" woofers.

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The plenum slides in and uses the same T-nuts as the 15 it replaces.

The experiment was done on a vented LaScala (as explained earlier), with the two 4" dia x 7" long ports out the back side of the top enclosure. Most people build an add-on riser type enclosure and mount on the bottom.

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It looks like the whole aparatus simply gets slid into the place where the original woofer is located, so the porting is the same and you just slide the whole thing out if you need to service.

Check out the pics on the first page.

I was referring to the assembly construction itself, not how it fits into the doghouse. It appears that 2 of the drivers are not serviceable without taking the driver housing apart (with the assembly out of the speaker). Check out the pics on the first page.

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With the plenum removed from the dog house, removal of the accessible drivers would permit access to the front of the other drivers through the holes.

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With the plenum removed from the dog house, removal of the accessible drivers would permit access to the front of the other drivers through the jokes.

I had thought about that but it didn't look as if the inner box depth was wide enough to allow the whole driver to drop into and I knew they couldn't come out through the outer driver holes. It may just be an illusion on my part.

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" . . . through the jokes."

Don't you just love auto-misspell?

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" was referring to the assembly construction itself, not how it fits into
the doghouse. It appears that 2 of the drivers are not serviceable
without taking the driver housing apart (with the assembly out of the
speaker). Check out the pics on the first page."

The SEAS drivers have bucking magnets and a can-type shield that the Visaton and Silver Flute don't have. This required a special construction the others don't require. To service the drivers you would remove the plenum and remove the outside mounted drivers to gain access to the mounting hardware for the inside mounting drivers, the inside mounted drivers will now come out through the exit slot where it mates to the slot in the LaScala.

With the Visaton or Silver Flute it is much simpler, and the slot could be made the same width as the slot in the LaScala, and both sets of drivers would mount to the external surface of the plenum (unlike the SEAS model used).

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The SEAS drivers have bucking magnets and a can-type shield that the Visaton and Silver Flute don't have. This required a special construction the others don't require. To service the drivers you would remove the plenum and remove the outside mounted drivers to gain access to the mounting hardware for the inside mounting drivers, the inside mounted drivers will now come out through the exit slot where it mates to the slot in the LaScala.

AAAAAH. I see the extra cut in the slot now. I thought it was a straight cut slot. I missed that before, thanks.

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I did some rough math on cone area and the (4) 8s have around 200 sq inches of surface compared to the 175 sq inches of the single 15. Does this add any to the output since there is technically more area moving? Or does that not make much of a difference in this configuration. Also. Like some of the tapped horns I have seen the same cabinet can just be widened and add another woofer for more output. Could this be done on the la Scala bins to fit a (4) 10" configuration or (6) 6ohm 8"? I'm tossing around ideals for a build.

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Kappa 15C Surface Area of Cone (Sd)856.3 cm2

Beta 8A Surface Area of Cone (Sd)210 cm2 x 4 = 840cm2

In theory you could design another cabinet for other size drivers, but I was looking for drivers that would fit the existing design. The SEAS drivers were a one-off surplus driver that looked to have the right parameters. The Visaton and Silver Flute are the only others I have found that look right. There is a dual 12 PPSL design out there using a large front horn crossed to the EV HR9040, about 40" wide.

I only build horns for use at 150hz and above now, I just use the PPSL below them. My 35hz dual 15 design is 104dB/2.83V/1M, is that efficient enough for you? My smaller 27hz dual 12 design is 100.5dB/2.83V/1M, it's the same size as the bottom of the LaScala (2x2x2). I've done 27hz dual 18 designs, for a given cut-off frequency the efficiency and size are related, double the size and the efficiency goes up 3dB, half-size it and the efficiency goes down 3dB. There is no free lunch.

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Wasn't considering sd just diameter. Where's the top end of the dual 12 cut off at? This loaded into a la Scala bin or is it a different fold?

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With the Visaton or Silver Flute it is much simpler, and the slot could be made the same width as the slot in the LaScala, and both sets of drivers would mount to the external surface of the plenum (unlike the SEAS model used).

 

 

 

 

I was looking for drivers that would fit the existing design. The SEAS drivers were a one-off surplus driver that looked to have the right parameters. The Visaton and Silver Flute are the only others I have found that look right. There is a dual 12 PPSL design out there using a large front horn crossed to the EV HR9040, about 40" wide.

I only build horns for use at 150hz and above now, I just use the PPSL below them. My 35hz dual 15 design is 104dB/2.83V/1M, is that efficient enough for you? My smaller 27hz dual 12 design is 100.5dB/2.83V/1M, it's the same size as the bottom of the LaScala (2x2x2). I've done 27hz dual 18 designs, for a given cut-off frequency the efficiency and size are related, double the size and the efficiency goes up 3dB, half-size it and the efficiency goes down 3dB. There is no free lunch.

 

 

 

Does the design basically involve modeling the box the same as you would a sealed or bass reflex box? Also, do you just double the volume from the box model for the two drivers excluding the volume needed for the plenum or some other formula?

 

Is there a standard “rule” for the size of the cavity for the plenum (i.e. just large enough to mount the drivers) or is there a formula to work from for size and the impact on corresponding compression generated, frequency response band-width, etc.?

 

Thanks.

Edited by Fjd

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