Need for a sub is to my thinking a multiple choice answer with three options:
A. No subwoofer needed.
B. Subwoofer absolutely needed.
C. DSP and/or more PTT6.5s or 8s needed.
For my day-to-day use its "A" no sub. The PTT6.5+PRs get to below 30 Hz in my room and when movie directors add really deep sonic effects they are clearly audible. The tracks on my music centric bass-demo playlist result in dropped jaws and exclamations of "did you hear THAT!" I believe part of my satisfaction is my typical listening levels averaging below 90 dB.
Add in a strong home theater mix or musical tastes and listening levels running to the Ministry Of Sound Classical concert cited above and your answer is "B" bring on the subs. I would not advise hitting a PTT6.5+PRs system without high pass protection with the trip-wire scene from 1917 at THX level. Those applications are why 15" subs are so widely available and 18" and even 21" woofs keep coming to market. I'm working on a post on how I overloaded the PTT6.5+PRs using a classical music piece with the volume control and EQ at silly levels.
Option 'C' is looking forward to an attempt to reset the state-of-the-art with bass depth and output capability along with the industry leading low distortion PURIFI brings. I expect most of you know it is very common in modern powered subs and advanced table top all-in-ones like B&W Zeppelin and Naim Mu-so to combine bass boost below system Fs along with dynamic limiting. The 'oh-shyt' moment I metioned above occured while I had the EQ elements of that enabled and got complacent and left soft dynamic limiting on the To-Do list. The glimpse I enjoyed of what lies on this path was very tantalizing. Start adding multiple PURIFI woofers per channel and (IMHO) it will reset the state-of-the-art for both bass depth and distortion at high levels.
correct. below the tuning the woofer and PR are getting out of phase so forces are more like reinforcing rather than cancelling. There might be a frequency range where there is a bit of cancellation but it is for sure not wide band. The net force can of course be calculated and plotted with a bit of math/physics. The side mounted PRs cancel forces from a simple symmetry consideration
Let's get real. My prototype design with the PTT6.5X-04" in a 21L box, using a regular ol' 2.5" diameter port, goes all the way to 35Hz (F3). People said it couldn't be done, but it can be done, if you pay attention to the power handling, excursion and air velocity at the port tuning frequency, and remember to include the baffle step losses.
It doesn't start to complain until about 99dB @ 40Hz. Power handling drops like a rock below 30Hz, but honestly there isn't much musical content below 30Hz, as demonstrated on my FFT of the live concert.
Which is only 10dB less than the enormous speakers that they replace, that are 6 times as big, and almost twice as wide, and 3 times as heavy. Besides, these big speakers spend half their time at 0dB (off), and no-one in my house wants to look them either.
When Scan-Speak came out with their 18W midwoofers, with 6.5mm excursion, it really put companies catapulted companies like Wilson Audio, Sonus Faber and ProAc.
Now in C21 Purifi Transducer Technology shows that they can go on step further...
Small is in, and it's here to stay...
It doesn't start to complain until about 99dB @ 40Hz. Power handling drops like a rock below 30Hz, but honestly there isn't much musical content below 30Hz, as demonstrated on my FFT of the live concert.
Which is only 10dB less than the enormous speakers that they replace, that are 6 times as big, and almost twice as wide, and 3 times as heavy. Besides, these big speakers spend half their time at 0dB (off), and no-one in my house wants to look them either.
When Scan-Speak came out with their 18W midwoofers, with 6.5mm excursion, it really put companies catapulted companies like Wilson Audio, Sonus Faber and ProAc.
Now in C21 Purifi Transducer Technology shows that they can go on step further...
Small is in, and it's here to stay...
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Similar figure in Vituix with 2x Purifi PRs, 12L volume. Between 30Hz to 150Hz there's a clear in-phase PR component that adds up to the main driver SPL. There's an out of phase component as well that will contribute to the cabinet "rocking" if PRs are rear mounted. Tried to figure out the out of phase energy component via LTSpice that is not cancelled out, does not seem like much yet not sure I got it right though.
The Newton forces are simply mass times acceleration for each driver (and hence goes to zero towards 0Hz). At the tuning frequency the PR’s do most of the SPL, ie they have most of the acceleration whilst the active driver excursion is at minimum. since the PRs are much heavier than then active driver they produce much stronger forces than the active driver for the same SPL (eg if the driver was in a sealed box). Having two PRs instead of one quadruples the total mass needed to keep the tuning frequency whilst area doubles. That doubles the Newton force for the same SPL. The least force is obtained using a port (small area low mass high excursion). But even a port gives Newton forces - although it is a bit mind twisting to imagine
The other thing to be mindful of, is the proximity of the passive radiators to the active one. Midrange leakage through the PR cone is a real phenomenon, and If using dual PR I’d try to keep them as far away from the active driver as possible.
btw, @mainframe
Yevgeniy’s released plans for his 6.5” 2 way.
full plans to build your own are now available, and a small price to pay, I’d say, for builders looking for a solid design, with an excellent tweeter too:
https://hificompass.com/ru/projects/2-way-systems/puriwave-purifi-ptt65x08-nfa-01viawave-srt-7
btw, @mainframe
Yevgeniy’s released plans for his 6.5” 2 way.
full plans to build your own are now available, and a small price to pay, I’d say, for builders looking for a solid design, with an excellent tweeter too:
https://hificompass.com/ru/projects/2-way-systems/puriwave-purifi-ptt65x08-nfa-01viawave-srt-7
I don't understand. I don't have any problem with pages.
I'm asking mainframe if he would he would consider updating the OP to include Yevgengiy's design, as only he can do that.
Perhaps there's been a miscommunication...
Nice build, what turned me off initially was the (expected) chuffing noises that were reported by a builder. Seems this artefact is mitigated by dampening the port with cloth/felt, aesthetically it is less pleasing to my eyes
I don’t think there’s anything stopping distributors from shipping to you:
http://viawave.ru/en/contacts
Yes, if they still have stock. Not exactly easy, due to sanctions, to do business with Russia if you’re in the USA or in EU.