DSL sells sealed FLH (front loaded horn) subs, for instance the DBH-218.
DSL sells BR enclosures, like these in the Studio Series:
Many of the DSL multiple entry horns, like the SH-50 use bass reflex ports:
The SH50 impedance dip at 90 Hz is the Fb, (frequency of box tuning).
The rise in response at 90 Hz peaks at Fb, filling in the falling response of the conical horn.
Art
ANY enclosure where the driver is buried and the output is thru a hole, port, vent, or horn is a BANDPASS ENCLOSURE.
A fourth order bandpass (BP4) port is it's only output exit.
The Synergy horn bass drivers have both a front BP port and bass reflex ports, so they are not a BP4 alignment.
At any rate, the OP's preference is for a BR alignment, not a BANDPASS ENCLOSURE. 😉
If a Synergy Horn has a BR port, then it's a BP6...still a BANDPASS ENCLOSURE.
The title of thread states FRONT LOADED BR, which equals a ported FLH or BP6P.
The title of thread states FRONT LOADED BR, which equals a ported FLH or BP6P.
The Sight of Sound: Revealing the Effects of Enclosure Design on Loudspeaker Performance
L-Acoustics crafts sound systems for arenas and concert halls. To accelerate the evolution of their bass reflex speaker designs, they simulated the effects of enclosures and vents on speakers' acoustic output and quality.By Alan Petrillo
September 2021
https://www.aes.org/e-lib/browse.cfm?elib=20776
The reference used by L'Acoustics to model their L-Vent is attached below.....
Non-linear acoustic losses prediction in vented loudspeaker using computational fluid dynamic simulation
Bass-reflex designs can exhibit strong non-linear behaviour around their resonant frequency with significant acoustic losses and parasite noise emission. These phenomena are mainly due to turbulences and flow separation at the port’s inlet and outlet. This work proposes a method to predict the resulting non-linear acoustic losses for a given loudspeaker, enclosure volume and port geometry. The approach consists of coupling computational fluid dynamics (CFD) simulation with loudspeaker non-linear motion modelization. Four different ports geometries mounted on one given loudspeaker enclosure are tested. The computed acoustic losses are compared with measurements and show a good agreement. The obtained results prove that the proposed method can predict non-linear losses with an average error less than 1 dB around the Helmholtz frequency.
Authors: Pene, Yves; Horyn, Yoachim; Combet, Christophe
Affiliation: L-Acoustics
AES Convention: 148 (May 2020) Paper Number: 10359
Publication Date: May 28, 2020
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"Maximizing Bass Reflex System Performance Through Optimization of Port Geometry" - Bryce Doll (2021) Thesis
Can and will are 2 different things. That's why port air speed is important. I TRY to keep port air speed around 10 m/s. Folks on avsforum.com think 20-25 m/s is acceptable. I think WINISD goes into the red at 15 m/s.
Still, all things being equal, a driver is going to move LESS in a BANDPASS ENCLOSURE than a Sealed or BR enclosure per a given voltage.
Less movement = less distortion.
Is data-bass.com up and running again?
On the site, you can do some comparisons with the same driver in various enclosure types to see what enclosure has the least distortion.
Still, all things being equal, a driver is going to move LESS in a BANDPASS ENCLOSURE than a Sealed or BR enclosure per a given voltage.
Less movement = less distortion.
Is data-bass.com up and running again?
On the site, you can do some comparisons with the same driver in various enclosure types to see what enclosure has the least distortion.
I chose a "Pro Audio" frequency.
You have to go into each individual test to see distortion levels.
https://data-bass.com/#/systems?activetab=cea2010&sort=31Hz:1,20Hz:1,mfr:-1&_k=97b5yo
Bandpass 4 life!
You have to go into each individual test to see distortion levels.
https://data-bass.com/#/systems?activetab=cea2010&sort=31Hz:1,20Hz:1,mfr:-1&_k=97b5yo
Bandpass 4 life!
So if Sealed and BR top out at 126dB at 31.5hz, what do you think the distortion levels will be for ALL the LOUDER bandpass enclosures at that SAME dB and frequency???
The AES paper linked in #46 has some very interesting measured results, the radiused hourglass shaped laminar port "D" had slightly less measured loss outdoors (-2dB) than the larger volume and area port "C" (~-2.5dB), even though it's Strouhal "St" number was far lower, indicating higher port velocity.
" A ST ≤ 1 will lead to flow separation and vortices formation" does not seem to predict the laminar port's measured output loss at high drive levels.
True, and the SPL may be more for a given voltage and volume of enclosure.
Less movement does not necessarily mean less distortion, higher driver loading does not come without consequence.
I did excursion and distortion measurements using a B&C18SW115 in both a TH (tapped horn- Keystone Sub/"18KS") and a BR (bass reflex) enclosure both with an Fb near 37Hz ("18BR37" or "18BR38Fb").
The TH averaged about 6dB more output than the BR, but the BR averaged half the distortion.
Art
Attachments
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No, the huge horns and Josh Ricci's quad 19" M.A.U.L rule that frequency range, no surprise, though BR and Sealed dominate the top 10 at 10Hz.
Clicking on the "CEA-2010" icon compares the maximum pass level at a defined amount of distortion, distortion levels being more stringent at upper frequencies.
Glad to see data-bass.com back on line!
BR = 10mm, 109.1dB & 115.1dB, 4% @ 35hz.
KS = 3mm, 117.8dB & 123.8dB, 5% @ 35hz.
The KS wins EVERY time in my book!
It would be interesting to know the Keystone's distortion level at the BR's dB levels???
Could the Keystone port location be the cause of the higher distortion level?
I think the TH mouth location affects distortion levels. The more the driver is exposed (you see the driver), then the higher the distortion level.
Which enclosure sounds better to your ears?
Uh PRO AUDIO is not playing 10hz music.
The 18ft3 TH is smaller than the loudest Sealed and BR enclosures at PRO AUDIO frequencies. Remember, the standard by the OP was 37hz.
Comparing Josh Ricci's distortion levels of TH at 5dB increases of drive levels, I'd guess the Keystone TH distortion would drop by about 50% on average reducing it's drive level by ~-6dB to approximate that of the bass reflex.
That said, the TH has more upper distortion than the BR, so would still be a bit higher.
Comparing the Gjallerhorn TH to the DTS-10 TH, the relative location of the driver to the mouth does not seem to affect the distortion distribution:
When equalized for the same response and phase aligned with top cabinets, I don't think I'd hear much difference at the same level. The TH having about +6dB more output capability would "sound better" when the headroom was required.
Paper delivery....
Maximizing Performance from Loudspeaker Ports - Salvatti et al. (2002)
Optimal Bass Reflex Loudspeaker Port Design - Bezzola (2019)
Loudspeaker Port Design for Optimal Performance and Listening Experience - Bezzola et al. (2019)
Reduction Of Bass Reflex Port Non-Linearities By Optimizing The Port Geometry - Roozen (1998)
Maximizing Performance from Loudspeaker Ports - Salvatti et al. (2002)
Optimal Bass Reflex Loudspeaker Port Design - Bezzola (2019)
Loudspeaker Port Design for Optimal Performance and Listening Experience - Bezzola et al. (2019)
Reduction Of Bass Reflex Port Non-Linearities By Optimizing The Port Geometry - Roozen (1998)