SVS 20-39CS volume/tuning question (1 Viewer)

[Brian_E]

I've been doing a ton of modeling with the Shiva in approx. 105L tuned somewhere between 18 and 20Hz, hoping to achieve (on paper at least) somewhat similar performance as the SVS 20-39CS. I would be using the AVA250 for power.
I read TN's review of the 20-39CS in TSS, and I noticed he stated that they are in 3.75 cu.ft. and use a 4"x15" port. I'm just trying to figure out how that tunes the enclosure to 20Hz. LspCAD tells me the port would need to be about 18.25" long, and this is just for a non-flared port. Since SVS uses flares, wouldn't the port need to be even longer to achieve a 20Hz tune in that volume?

 

[Julian Data]

Hi!
SVS doesn't use the Shiva driver so the T/S specs will be different.
The smaller the diameter the port the shorter the distance and vice versa for the bigger the diameter the port the longer the port. The number of ports also consitutes more in length.
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[Tom Vodhanel]

>>>I read TN's review of the 20-39CS in TSS, and I noticed he stated that they are in 3.75 cu.ft. and use a 4"x15" port. I'm just trying to figure out how that tunes the enclosure to 20Hz.

 

[Brian_E]

Hi Julian,

SVS doesn't use the Shiva driver so the T/S specs will be different.

I'm aware of this, but I didn't think T/S specs had anything to with tuning an enclosure. I was under the impression you tune a box, not a driver.
TV:
Wow. So if 3.75 is the actual, and by effective I assume you mean "what the driver see's". This would mean for a tune of ~20Hz the with a 4"x15" port your driver would need to see about 125L or 4.414 cu. ft. I didn't know lining the enclosure would give you this kind of increase in effective volume.
Or am I still missing something?
BTW, TV, Congrats on your success with SVS. You took the dream most of us DIYer's have and made it a reality. If I didn't like building and tinkering with stuff so damn much I would have gotten an SVS a long time ago, but that just would've been too easy.

 

[Tom Vodhanel]

>>>TV:
Wow. So if 3.75 is the actual, and by effective I assume you mean "what the driver see's". This would mean for a tune of ~20Hz the with a 4"x15" port your driver would need to see about 125L or 4.414 cu. ft. I didn't know lining the enclosure would give you this kind of increase in effective volume.>Or am I still missing something? If I didn't like building and tinkering with stuff so damn much I would have gotten an SVS a long time ago, but that just would've been too easy

 

[John Morris]

SVS doesn't use the Shiva driver so the T/S specs will be different.

What driver DOES SVS use in the 20-39cs?
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Take Care,
merc
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DTCP, DFAST, 5C, DVI, and HDCP smell like DIVX!!!

 

[Jack Gilvey]

Their own.

 

[John Morris]

Jack: Thanks. I didn't know they manufactured their own drivers too! Wow!
I wonder why they aren't making their own Ultra drivers too? Maybe they found that TC Sounds could do it (make a custom version of the Mass2012) for less or that they needed their own manufacturing facility to keep up with the demands for their current line.
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Take Care,
merc
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DTCP, DFAST, 5C, DVI, and HDCP smell like DIVX!!!

 

[Patrick Sun]

I would surmise that SVS designs the drivers, using the current technology/material/baskets available to their driver makers, and then incorporate some tweaks to squeeze more performance out of them. If you notice, there are a lot of mega-drivers with the cast basket look to them. Most of those would be made by one or two driver makers who have a boatload of those baskets, and it's just a matter of mating the right size magnet/motor/voicecoil/cone to the assembly per the design spec for a desired level of performance.
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PatCave; HT Pix; Gear; DIY Mains; DIY CC; Sunosub I + II + III; DVDs; Link Removed

 

[Jack Gilvey]

Jack: Thanks. I didn't know they manufactured their own drivers too!

They don't. I believe they're a custom-made driver from TC Sounds. Not available apart from the sub.

 

[John Morris]

Pat and Jack: Thanks guys for clearing up my confusion on this matter.

They don't. I believe they're a custom-made driver from TC Sounds. Not available apart from the sub.

That makes sense. TC Sounds makes some dang nice drivers. I wonder how many other subwoofer manufacturer use custom designed, yet TC Sounds manufactured, drivers in their subs?
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Take Care,
merc
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DTCP, DFAST, 5C, DVI, and HDCP smell like DIVX!!!