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^^^

This subject of port tune has come up a lot on various threads, and I think it's important to reiterate a common theme from subwoofer designers. (Josh just answered this question better than I am doing it, but I still want to make some points.)

The port tune is only one aspect of determining a subwoofer's low-frequency output. I have, in the past, tried to discern port tunes of some subwoofers by looking at quasi-anechoic (outdoor, ground plane) graphs of their frequency responses. I think it is very hard to tell even from those graphs, because the way that DSP is applied is such a major factor in determining the low-frequency limits of the sub.

For instance, with subs like the JTR Cap 2400ULF, or the SVS PB16 Ultra, some mid-bass SPL is deliberately sacrificed in order to push more amplifier power into the
 

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If you guys ever model the JTR subs the port velocity is quite high, is this the port wind everbody talks about? I made some subs with higher velocity like that and one really can't hear anything unless at the limits but TR goes up dramatically.
I have not modeled the JTR subs.

My experience is that the Cap 1400 has higher port wind than the Cap 118HT, level matched and playing the same content.

From pure physics point of view, the 33mm X-Max driver (in the Cap 1400) should be more capable of producing higher port wind than the 19mm X-Max driver (in the Cap 118HT) when all else being equal.
 

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It probably has to do more with the size of the port and resulting port velocity. A higher tuned sub can get away with a bigger and shorter port which results in a lower port velocity. There are many different factors and of course with more excursion and power it pushes more spl through the port. 10hz 18 inch subs need to be massive to have very low port velocity and a higher resonance. JTR subs a tiny for 10hz subs and while there is boost to get flat. That also means the port velocity would be higher which can cause more port wind(I am guessing) but still not enough to chuff until maxed. Unless somebody has a huge room with just one sub it probably is never pushed.
 

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No actually I didn't see what you posted here and I am not sure what you said is valid.
What I said in the boded part below. How can a 15hz +-3db anechoic spec translate to reach 7-10hz in room versus 11-14hz in room of the v3611 with a 16Hz +-3db anechoic spec? Is that very confusing from being 15hz versus 16Hz anechoic, don't you think? Beside, you know a port sub rolls off heavily at port tune, I like to see proof of a 15hz (-6db) or a 13.5Hz tuned sub that can still go that low (7Hz) in room other than a closet sized room.

Based on the v3611 spec below, the 3 new psa lower tuned subs are spec’ed at 1hz lower than the current v3611. I did not know the 1hz lower at 15hz +-3db anechoic can translate to reach 7-10hz in room versus 11-14hz of the v3611? :confused:. Does anyone know the port tune of the v3611?

What has been determined so far is that the -3db point is below the port tune on the V3611 and the -3db point is above the port tune on the TV36. That can only mean the TV36 has a shallower roll off compared to the V3611.
First, -3db is not the same as +/-3db spec. +/-3db means -6db. Who determines the boded part above as it is so vague and misleading.
The best way to clear these confusions from PSA specs is to send a sub to Ricci.

Chucky posted some info on the FV25 that shows the same behavior.. the -3db point is actually 16hz, but has a 12hz tune...so that shows the -3db point doesn't define the subs extension capability.
What Chucky posted in that screenshot from data-bass is what Josh describes the effect of the Rythmik frequency and damping switches, NOT its frequency response nor port tune frequency.

 

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Ricci posted while I was typing this. He obviously explained it better then I did. With DSP the response can be shaped however the OEM choses...so using the old -3db point to determine a subs extension capability is old mythology in 2019...especially since OEM's no longer need to use set 24db or 48db per octave filters around the tuning point with todays amplifier technology.
I'll echo Ricci's comments, with some hope of simplifying a little further. While I would probably choose different ways to more clearly express the specification (or a picture says 1000 words here), you can pick what ever +/- tolerance you feel is relevant, but it's not like a speaker suddenly turns off when you get to a +/- 4dB window. :rolleyes: The deeper extending sealed subs all take advantage of the naturally shallower roll of and lack of a hard low frequency operational limit. With the right shape between 10-20Hz, or say 15-30Hz you will often see a very complimentary match to the low frequency gain function of most rooms that have a least 3 solid walls and a less than ~20' ceiling. Our SubMersive and F18 has demonstrated extension to 7-12Hz in most rooms with an anechoic response that fits +/-3dB from 18-19Hz to the above 120Hz. Of course I could spec the same box as being say +/-1dB from 30-100Hz AND +1/-10dB from ~13-250 Hz. It's just a matter of picking your window in a way that's applicable to the use. Similarly you will often see amplifier specifications +/- some fraction of a dB along with a much wider +/-3dB spec. If you really want to see what's going on, perform sweeps and increasing level into the limits, and for ported subs also get a nearfield measurement with the microphone ~0.5" from the woofer cone. Tom's already made a few references to the Data-Bass measurements of the X-21 vs what he saw possible in his product. You can see there what a big pro driver in a low tuned cabinet does with and without EQ. The response curve shown with the Behringer amp with 2 ports open is already a little flatter than I would set as neutral on such a product, and looking at the space between the raw and EQ'd response should give you an idea of what is going on with their new lower tuned subs. For a comparative reference, the response I optimized for the Terraform D18 subwoofer I did a limited run of almost 5 years ago were tuned to 10.5-11Hz and were -10-12dB at 10Hz vs the flat passband of 35-100Hz. This still gives a nicely rising VLF response in many rooms, regardless of the ground plane +/-3dB window.
 

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Here is Tom's quote from the PSA subwoofer thread and their Facebook page.

Source https://www.facebook.com/powersoundaudio/
These are exciting times for PSA owners. Having such a attractive trade-in program really benefits the consumers. I was pleasantly surprised to learn that all 3 drivers would be offered. The pre-order pricing is so attractive that I even considered ordering a TV36ipal myself.

In the PSA thread I read of some folks inquiring about single driver versions, rather than dual 18s. I immediately thought about the X21s Seaton Sound offers. The 21" versions of the same B&C drivers are offered. Also, both passive (w/DSP recommendations) and active versions are options. https://seatonsound.net/product/x21subwoofer/

I suspect that the X21s and TV36Xs will measure similarly (X21 ipal ds115-4 was already tested by @Ricci). I'm foaming at the mouth to directly compare the two with the same driver model because I suspect there will be a difference in tactile response as the X21 has front facing-ports and variable tune while the TV36X have the single down-facing port.

I'm sure both have ample TR. I just see it as a good opportunity for learning more about TR in regards to port & driver orientations.

I read that PSA may be offering more premium wood veneers in the future (S1510 & S3010 only at the moment). Previously I had mentioned that Seaton, JTR, DSS and Funk offer premium veneers (not just wood) on all of their products. Rythmik recently reminded me that Jim Salk can build any Rythmik sub with premium veneer.
 

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I havent heard many of the latest subs...do people in the know think they all sound the same or whats the dealio? is it all about TR? what type of spl's are people trying to compare subs at? I can do 120's db and think I have very weak bass...even my old man thought my bass was weak when demo'ing his classical stuff. 120 db's and weak bass...who woulda thunk?


edit to add my space is 20k cuft open layout....so not a knock on subs per se.
 

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Josh and Mark covered it well. You may have missed @basshead81's follow-up.
What was being questioned is why the TV36 -3db point (15hz) and the V3611 -3db 16hz if the TV36 extends deeper?



The Answer:



With today's DSP amplifier technology, -3db doesn't reveal a ported subs extension capability or tuning point. Many use to assume -3db was the area around the ported subs tune. In the past with analog amps that was probably a safe bet, but with DSP things can be manipulated more. I didn't realize this until I did some research this morning.



So even though both the TV36 and V36 have a similar -3db, the extension capabilities are completely different. Being the TV36 -3db point is above it's port tune tells me there is much less DSP applied down low to get the -3point down into the mid teens. However with the V3611 having a 18-19hz tune but a -3db of 16hz tells me it's requires much more DSP down low to get a flat response.



So in the end we can't base anything on -3db alone. The TV36 is going to play lower with much less effort because there is less DSP applied and it's hitting those frequencies on it's own.



I bring this up to try and paint a example of the difference in capability between the 2. If I am spending 2599.00 on a sub this is the technical stuff I like to know. Some just see a new toy and throw caution to the wind and that is OK but not how I roll.



Hopefully this helps others understand that again, even though both subs -3db are within 1hz, that doesn't mean they will have the same capabilities below 20hz.



I probably should of waited to post my initial question on this topic from a Computer so it was more clear. I am not a Mike Thomas on a keyboard by any means. :)
PSA, JTR, and Seaton all have their own DSP tuning techniques and their own sound signatures.

Nathan Funk has and will build ported subs, but he will strongly recommend his sealed offerings first.

@Mark Seaton hasn't mentioned it lately, but he once mentioned a killer idea for a next-gen Teranova. Mark, does the X21 negate the development of a new Teranova design?

TERRAFORM!
 

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Josh and Mark covered it well. You may have missed @basshead81's follow-up.

PSA, JTR, and Seaton all have their own DSP tuning techniques and their own sound signatures.

Nathan Funk has and will build ported subs, but he will strongly recommend his sealed offerings first.

@Mark Seaton hasn't mentioned it lately, but he once mentioned a killer idea for a next-gen Teranova. Mark, does the X21 negate the development of a new Teranova design?

TERRAFORM!
The X21 is a cabinet I already had designed and programmed that works really well for huge rooms and big bass appetites. The 9-12Hz VLF tuning of the Terraform designs I've done is a different animal, both the PR bandpass versions and direct radiating versions like the Terraform D18 which pennynike has 4 of working under his 6 Othorns (DIY 21" B&C woofer tapped horn Josh Ricci designed). I'd describe the X21 to by my take and preferences for a ported sub for a big open room. I'd prefer if it was a little shallower, but I didn't want that added complexity of bending large ports in that particular design. Unfortunately I didn't have enough time with the new amplifier in the box before sending it down to the TX meet, and the max level behavior wasn't dialed in quite the way I like it.

Remembering how involved I am with various calibrations and system set ups, I'll re-iterate that I often find location to be the much bigger issue than maximum VLF capability. There are cases where the huge ported box can work and is a fun option, but as you experienced in the Star Wars Theater, enough sealed 18s can be extremely impressive while being dramatically easier to carry in and place in a basement or 2nd floor theater. This is one reason I developed the 2 sealed 18" packages for theater designers and installers rather than a production Terraform design. Originally we were going to do a custom pair of Terraform cabinets for the Star Wars theater, and I'm very happy we changed plan for the 8x sealed 18s. I think next year we'll add some more sealed subs to the rear of the room to further smooth things out and allow more control of the bass through the room. They will either go in the rear fabric wall, or may even load in from under the floor cavity.
 

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Ok, I think I've got it straight now. Ipals were tested in the sealed dual-opposed cab.

https://data-bass.com/data?page=driver&id=54
https://data-bass.com/data?page=driver&id=69
If guys are looking to model anything, B&C has great data on most of their woofers. You can see in this thread on the DIY forum where the North American Sales Manager, Bennett Prescott, posted up Klippel data for the 18DS115 woofer which is their next most capable 18" after the 18IPAL.
 

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Ok, I think I've got it straight now. Ipals were tested in the sealed dual-opposed cab.

https://data-bass.com/data?page=driver&id=54
https://data-bass.com/data?page=driver&id=69

Thanks

There's also the little sub I put together for the 21Ipal's called the Skhorn. (See my avatar pic) That's where mine live these days.


Another good B&C woofer is the 21SW152-4. It slots in between the 21DS and the Ipal. Results for those are also at DB in a variety of cabs.

The X21 is a cabinet I already had designed and programmed that works really well for huge rooms and big bass appetites. The 9-12Hz VLF tuning of the Terraform designs I've done is a different animal, both the PR bandpass versions and direct radiating versions like the Terraform D18 which pennynike has 4 of working under his 6 Othorns (DIY 21" B&C woofer tapped horn Josh Ricci designed).

I still regret not making Axpona and getting a chance to hear that ridiculous system and the Star Wars theater. :(
 

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There's also the little sub I put together for the 21Ipal's called the Skhorn. (See my avatar pic) That's where mine live these days.


Another good B&C woofer is the 21SW152-4. It slots in between the 21DS and the Ipal. Results for those are also at DB in a variety of cabs.




I still regret not making Axpona and getting a chance to hear that ridiculous system and the Star Wars theater. :(
Had a couch ready for ya bro :D
 

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Ok, PSA TV36 Neo or FV25HP. I really feel like taking a chance on the TV36 Neo, but FV25HP has been tested and it’s numbers are great . I know any comparisons would really be speculation, but I need help lol.
 

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Ok, PSA TV36 Neo or FV25HP. I really feel like taking a chance on the TV36 Neo, but FV25HP has been tested and it’s numbers are great . I know any comparisons would really be speculation, but I need help lol.

It will be speculation. If you can get both and compare then that would be the best. Otherwise you will always be guessing.




Sent from my iPhone using Tapatalk
 

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You would need to give us a little more information. How big is your room? Open or sealed? Concrete or suspended floors? Movies or music? What subs did you have before? Buying duals or single sub? Any particular characteristic you're looking for in a sub? But, even with that, you are correct, it would be pure speculation at this point.

If you aren't in a hurry, I would wait to see the specs and impressions out in the wild for the new PSA subs.

Todd
 
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