'Custom' in that during my most active DIY speaker years from '56 - '89 I learned that sealed often didn't work all that well down low in most homes/apartments in my locale [greater metro Atlanta], so experimentally found a vented tuning that worked much better overall using basic TL/horn design theory.
For the record, TTBOMK, Don Keele's is the original T/S theory EBS: [Thiele #9.5]: Vb = 2.6*Vas, Fb = 0.52*Fs, 0.625 Qts': [Qts] + any added series resistance [Rs]: http://www.mh-audio.nl/Calculators/newqts.html
No, sealed is just a pressure vessel, so it's strictly for vented alignments and didn't mean for you to literally try his math [or 'my' Altec X-Bass that I'd long since forgotten about posting], just the 'shelf' concept as my customs requires you to learn about mass loaded [vented] TL, horn design to do them.
That said, with such a low Qts, the basic vented concept should work in your app.
Regardless, without knowing any room dimensions, floor plan with speaker, listening positions, basic building structure details, etc., can't really recommend any ~ optimum sealed alignments other than making it with an over damped ~0.4 Qtc' since the room tends to increase it and provide access to reduce its net Vb if required to change the Fc:Qtc ratio.
For the record, TTBOMK, Don Keele's is the original T/S theory EBS: [Thiele #9.5]: Vb = 2.6*Vas, Fb = 0.52*Fs, 0.625 Qts': [Qts] + any added series resistance [Rs]: http://www.mh-audio.nl/Calculators/newqts.html
No, sealed is just a pressure vessel, so it's strictly for vented alignments and didn't mean for you to literally try his math [or 'my' Altec X-Bass that I'd long since forgotten about posting], just the 'shelf' concept as my customs requires you to learn about mass loaded [vented] TL, horn design to do them.
That said, with such a low Qts, the basic vented concept should work in your app.
Regardless, without knowing any room dimensions, floor plan with speaker, listening positions, basic building structure details, etc., can't really recommend any ~ optimum sealed alignments other than making it with an over damped ~0.4 Qtc' since the room tends to increase it and provide access to reduce its net Vb if required to change the Fc:Qtc ratio.
Thanks again for continuing the discussion.
My room is 10m wide, 2.7m tall, and the length varies across the width from 6m to a small section that is only 4.5m. Hard tiled floor,plastered brick walls, and plastered concrete ceiling. The room is an open plan kitchen/ living/ dining room
Of course there are some soft furnishings, including two dense( as apposed to fluffy) carpets, but largely it’s a hard room.
I have found that vented speakers overload the room very easily with bass standing waves/ modes. My acquisition of sealed speakers has been a revelation. Thus my fixation on sealed alignment.
However, the YG Carmel is a 6.5 woofer, 1 inch tweeter 2 way. They sound excellent, but I think they are a touch too small for the volume of the room. Which brings me to the two subs I want to incorporate. I have a feeling that an 0.5 qtc sealed box might just do the trick, but my question is largely an attempt to get some assurance that the money I plan to spend on building decent quality boxes is warranted for my application. An educated guess is what I’m after, as I have very little practical experience in these things.
You're welcome!
OK, 1st room mode is ~344/2/10 = ~17.7 Hz where 'cabin gain' begins boosting the low end assuming there's nothing to bleed it off and of course there's any local boundary gain. This is the type of scenario I usually had and where the EBS comes into play.
For instance, due to my house's oddball floor plan mine's at ~12.5 Hz, so with my ~20 Hz Fs, 0.21 Qts', 20 ft^3 Vas 15", desired 0.4 Qtc, I've no choice: Fc = [0.4*20]/0.21 = ~38.1 Hz.
OK, 1st room mode is ~344/2/10 = ~17.7 Hz where 'cabin gain' begins boosting the low end assuming there's nothing to bleed it off and of course there's any local boundary gain. This is the type of scenario I usually had and where the EBS comes into play.
For instance, due to my house's oddball floor plan mine's at ~12.5 Hz, so with my ~20 Hz Fs, 0.21 Qts', 20 ft^3 Vas 15", desired 0.4 Qtc, I've no choice: Fc = [0.4*20]/0.21 = ~38.1 Hz.
Thanks again GM
I have explored all kinds of calculators on the web. I guess my trouble is that due to my inexperience I cannot correlate the numbers on the screen to what I expect to hear. Kind of like explaining to someone what 5g acceleration feels like- you can’t know till you know.
So I’m going to build QTC 0.5 sealed boxes and see what I see. Hopefully it won’t be a waste of expensive Birch ply. I’m planning on using 30mm.
Thanks again for taking an interest.
I have explored all kinds of calculators on the web. I guess my trouble is that due to my inexperience I cannot correlate the numbers on the screen to what I expect to hear. Kind of like explaining to someone what 5g acceleration feels like- you can’t know till you know.
So I’m going to build QTC 0.5 sealed boxes and see what I see. Hopefully it won’t be a waste of expensive Birch ply. I’m planning on using 30mm.
Thanks again for taking an interest.
You're welcome!
Understood and why I suggested going larger [0.4 Qtc] and if required to increase it, then add scrap 'whatever' to reduce it and if wanting/needing to keep weight down like so many of us, find a local company that scraps/recycles large pieces of Styrofoam packing and anchor it with special Styrofoam glue
FWIW, I normally made the [~unfinished] top removable and used industrial grade neoprene foam gasketing tape to seal, though since then a plenty good enough neoprene foam tape is available as inexpensive window/door weatherstripping at the local hardware or similar store. The finished/decorative top was typically something fairly heavy such as marble, slate or most often a plant/whatever chosen by any 'significant other' as a token gesture to WAF or similar to mass load it, held in place with small pieces of industrial Velcro and ideally will be at least as heavy as the cab to ensure it will become ~ as one with the room's construction and if you believe your cab will be too heavy, don't, as Jeff proved with a ~265 lb horn speaker: Altec A7 mass loading
Pictures
Note: design such that no holes/hardware go through the tape, just evenly clamps it and then only need minimal compression, so if any squishes out, it's way too tight.
Understood and why I suggested going larger [0.4 Qtc] and if required to increase it, then add scrap 'whatever' to reduce it and if wanting/needing to keep weight down like so many of us, find a local company that scraps/recycles large pieces of Styrofoam packing and anchor it with special Styrofoam glue
FWIW, I normally made the [~unfinished] top removable and used industrial grade neoprene foam gasketing tape to seal, though since then a plenty good enough neoprene foam tape is available as inexpensive window/door weatherstripping at the local hardware or similar store. The finished/decorative top was typically something fairly heavy such as marble, slate or most often a plant/whatever chosen by any 'significant other' as a token gesture to WAF or similar to mass load it, held in place with small pieces of industrial Velcro and ideally will be at least as heavy as the cab to ensure it will become ~ as one with the room's construction and if you believe your cab will be too heavy, don't, as Jeff proved with a ~265 lb horn speaker: Altec A7 mass loading
Pictures
Note: design such that no holes/hardware go through the tape, just evenly clamps it and then only need minimal compression, so if any squishes out, it's way too tight.
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Fast decay is equally as important as a good transient attack, and considerably more difficult to achieve. This to my ear is key to bass sounding real (or fast; tight; musical; whatever currently trendy word is used to describe the sound). As we all should know from Fourier, the fast leading edge of a transient is reproduced by the HF driver, not the sub! The system's energy storage in ported/horn/TL etc. loadings makes this fast decay impossible to achieve; large horn and ported subs can easily be ringing a quarter of a second after the signal has ceased, compared with typically 10ms or less for sealed. A system Q of 0.5 with the necessary EQ produces the most accurate bass reproduction I have heard. An acid test of any sub is the fast double bass-pedal drumming in thrash metal/Metallica-type music. Like it or loathe it, this should be reproduced as an almost machine gun-like staccato, not the muddy, blurred 'pffffrrrrrttt' as it comes across on virtually all PA and domestic systems, which seem to aim for the lowest possible F3 in the smallest possible box as marketing bragging rights - therein lies the root cause.
Thank you. A friend who listened to my (PA) system described the subtlety of reproduction - half jokingly - as being able to tell if, on the ethnic music I was playing, the drum skin was goat or antelope! Beyma AMT HF drivers played a big part too!
Sorry about bringin this up after a year or more.
Question regarding Q and the mass of a passive radiator.
I have two sets of very large floorstanding full-range speakers, VMPS Super Tower and Super Tower III, designed by the late Brian Cheney.
Each speaker uses a 15" downward-firing passive radiator. Morite putty is attached to the PR, and the end user is supposed to add or remove it to achieve the desired bass response.
I desire a low Q, tighter, flatter response. Generally speaking, would this mean more putty to increase mass or less putty to reduce mass? The instructions discuss what to listen for, but I'm interested in the more theoretical explanation.
Question regarding Q and the mass of a passive radiator.
I have two sets of very large floorstanding full-range speakers, VMPS Super Tower and Super Tower III, designed by the late Brian Cheney.
Each speaker uses a 15" downward-firing passive radiator. Morite putty is attached to the PR, and the end user is supposed to add or remove it to achieve the desired bass response.
I desire a low Q, tighter, flatter response. Generally speaking, would this mean more putty to increase mass or less putty to reduce mass? The instructions discuss what to listen for, but I'm interested in the more theoretical explanation.
My experience with good bass is not concerning only Q of the total box.
But also the quality of the driver itself.
The theory wants for best impulse response a driver with:
1. Infinitely stiff cone
2. Infinitely light cone
3. Infinitely mellow suspension
Besides all this we want no distortion coming from the electrical motor.
For a good bass reproduction I choose drivers with a stiff cone and if possible not too heavy cone with a not too stiff suspension.
The named Peerless XLS are known to be more like car Hifi drivers with heavy cones and very stiff suspension.
With such a driver you rarely achieve the most accurate bass reproduction.
But also the quality of the driver itself.
The theory wants for best impulse response a driver with:
1. Infinitely stiff cone
2. Infinitely light cone
3. Infinitely mellow suspension
Besides all this we want no distortion coming from the electrical motor.
For a good bass reproduction I choose drivers with a stiff cone and if possible not too heavy cone with a not too stiff suspension.
The named Peerless XLS are known to be more like car Hifi drivers with heavy cones and very stiff suspension.
With such a driver you rarely achieve the most accurate bass reproduction.
The thread started 22 years ago, and after ~two years dormant, davidc! revived it to ask about the Q factor of a cabinet using a 15" passive radiator in place of a port.
I wonder how much the down firing passive radiator suspension has sagged since it was installed, and how that has affected Fb and Q..
Which Q factor - Qtc (box) or Qts (driver)?
Didn't read this thread, but from the title - Qtc is the only factor which influence impulse response of the closed box loudspeaker, there are no other factors (not counting enclosure panel vibrations, internal resonances, etc.).
Vented/ported box loudspeaker is a different story...
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Ideally and mathematically yes, in reality the air (in a closed box), the driver (its cone, suspension, motor, etc.), the box itself can be highly non-linear so that it doesn't follow the ideal principle, and they can even add different types of distortions.
The air in the box is way more linear than driver's suspension and motor. Cone resonance and box resonance may disturb the "mathematical/theoretical" impulse response, but won't change the "tightness" of the closed box loudspeaker (OP title).
Cone, suspension and motor are nonlinear, but they don't influence the "tightness" of the closed box loudspeaker (OP title) - it remains dominated solely on Qtc.
Cone, suspension and motor are nonlinear, but they don't influence the "tightness" of the closed box loudspeaker (OP title) - it remains dominated solely on Qtc.