Thanks Art. I’ll get some time later today to run some more sims targeting 40hz Fb
Some things to note
SBA have replied with
“There is no hard and fast rule for that because it totally depends on the application. You would have to do a full system durability to find out for sure on the application.
You can use a thumb rule of 150% of added mass to the existing mms.
Example SB15SFCR-00 mms 62g.
Don't add more than about 93g”
Dual 8” PRs need tuning weight that is out of range of that rule of thumb but could work if it doesn’t fall apart. A single 10” NRX running safe weight tune with matching graphs on most parts with slight rise in group delay
Unsuccessful at locating any other drivers in the Vas to 8L with Fs of below 60hz
Active driver Sd is 143. This seems a bit high for a 6.5”er when compared to some of the 6.5” PR Sd
I know that you recommended against the single 10” NRX before but just how bad is a flat 106db with 300w down to 42hz and F3 39hz with 6-8L? Tentative new sims are drawing that
Some things to note
SBA have replied with
“There is no hard and fast rule for that because it totally depends on the application. You would have to do a full system durability to find out for sure on the application.
You can use a thumb rule of 150% of added mass to the existing mms.
Example SB15SFCR-00 mms 62g.
Don't add more than about 93g”
Dual 8” PRs need tuning weight that is out of range of that rule of thumb but could work if it doesn’t fall apart. A single 10” NRX running safe weight tune with matching graphs on most parts with slight rise in group delay
Unsuccessful at locating any other drivers in the Vas to 8L with Fs of below 60hz
Active driver Sd is 143. This seems a bit high for a 6.5”er when compared to some of the 6.5” PR Sd
I know that you recommended against the single 10” NRX before but just how bad is a flat 106db with 300w down to 42hz and F3 39hz with 6-8L? Tentative new sims are drawing that
Spent some time trying to read and understand what the various graphs mean and also tried to config the cab more space efficiently to claim more than 6Lbut not really feasible due to cab shape and single 10" PR
The best I can get while staying within tuning weight max recommendation and space that I want to make available works out to 10L driver volume. I can get this, but I will have to change the cab shape completely due to it needing a single 10" PR from the choices available to me at an affordable price. Units from US shops are unaffordable due to shipping charges
Creates a whole new set of issues. For one, the racer is out for the sub but on the bright side, I might be able to use them still in the v4 cab for the tops. I will have to think up a whole new config for the cab, as cant be laid down now. Leaning towards a tapered cab possibly sticking out of the stand on one side and a new stand
Onwards to v5..........still thinking about what form it might take. Will start with the best possible sims for the ZR6.4D in very limited spaces. By the results of my searching and the resounding silence re driver suggestions, this and the very difficult to get ZXI6.4D might be the only units out there with the potential for a clean musical bass speaker that can exceed flat 103db flat down to 40hz Fb with 10L and under volume
The best I can get while staying within tuning weight max recommendation and space that I want to make available works out to 10L driver volume. I can get this, but I will have to change the cab shape completely due to it needing a single 10" PR from the choices available to me at an affordable price. Units from US shops are unaffordable due to shipping charges
Creates a whole new set of issues. For one, the racer is out for the sub but on the bright side, I might be able to use them still in the v4 cab for the tops. I will have to think up a whole new config for the cab, as cant be laid down now. Leaning towards a tapered cab possibly sticking out of the stand on one side and a new stand
Onwards to v5..........still thinking about what form it might take. Will start with the best possible sims for the ZR6.4D in very limited spaces. By the results of my searching and the resounding silence re driver suggestions, this and the very difficult to get ZXI6.4D might be the only units out there with the potential for a clean musical bass speaker that can exceed flat 103db flat down to 40hz Fb with 10L and under volume
Falling apart and working poorly are a few reasons for the rule of thumb.
More excursion generally requires a larger surround area, which reduces Sd for a given frame size.
I don't recall recommending against any PR, but mentioned a larger PR requires more mass for a low Fb.
Two smaller PR with equal displacement potential to the single 10" could be mounted in opposition to cancel the moving mass force.
106dB at 42Hz sounds like it would be well within the SB29NRX-00 excursion potential, and if the additional mass is within 150%, it should be OK according to SBA's rule of thumb. That much unbalanced moving mass is going to make a lightweight cabinet want to move around.
To put the levels you are considering in perspective, 103dB at 39Hz sounds ~ equal loudness to 65dB at 1000Hz, a conversational level at one meter.
Outside, the level drops at -6dB per doubling of distance, 39Hz 97dB at 2 meters, 91dB at 4 meters, equal loudness to a whisper.
Art
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I wonder how the Z623 does it than when it's not even being pushed to the max. Even getting a clean flat response and matching its output seems not enough going by what you are saying. What can I expect by adding a second uint? One pair with each doing a clean 103db @ 300w........ I am a bit confused if that's a 3 or 6db gain? And whether if than it can approach the Z623 output class
Does conversational mean being able to hold a conversation over or as loud as conversation?
I prefer the idea of dual opposed PR units but the available 8" models are lacking in ability to carry the required weight to tune them. Something like a pair of Slaps8s might work but out of contention due to pricing and shipping for two units
Any thoughts on using two more ZR6.4Ds as dual opposed PRs? They are cheaper than the 10" NRX PR and @ same dia as the active driver, easy to fit into robot head. Would you be able to help me find what numbers to use for PR parameters if I use them unconnected? Do the existing parameters for Vas, Fs and Qms still apply? That's the numbers that WinISD needs to model the PR apart from the Sd and Xmax
Does conversational mean being able to hold a conversation over or as loud as conversation?
I prefer the idea of dual opposed PR units but the available 8" models are lacking in ability to carry the required weight to tune them. Something like a pair of Slaps8s might work but out of contention due to pricing and shipping for two units
Any thoughts on using two more ZR6.4Ds as dual opposed PRs? They are cheaper than the 10" NRX PR and @ same dia as the active driver, easy to fit into robot head. Would you be able to help me find what numbers to use for PR parameters if I use them unconnected? Do the existing parameters for Vas, Fs and Qms still apply? That's the numbers that WinISD needs to model the PR apart from the Sd and Xmax
Art, I tried to get some perspective on this and look for some plots that you would be familiar with. How does the current 103db flat to 40hz with 300w compare with the Keystone 12?
I'll go straight to trying to extract usable out a tiny box with the larger ZR12.4D. Once, I have ordered the modded mono FFA002 pair from Erica.C, I'll have 600wrms @4R x 2 to throw at that project
In the meantime, let's mark the Cub Sandwich project as parked as a false start. No point in making a good cab without a valid acoustic model. Let's move onto the next area that I wanted to trial the ZR6.4D
I need a good system in my smoking/digital studio/mini DJ studio chill space and have absolutely no space on the floor. Even something like the Z623 is too large a sub
Let's see if the ZR6.4D can serve here. The current sims show it can approach the Z623 in output and with a very smooth response. The driver is only 172mm wide and will fit nicely in a narrow desktop box. I like the idea of a pair of bass cabs as stands for a pair of 3" FR tops. Or even a two-way with these two drivers. Very inert boxes will be a must, so dual opposed PRs
One of my many sets of Z623s is currently used here. A boost is used on the lows to bring the lowest of bass guitar notes up to audible, while the overall volume knob is set very low
A nice looking pair of very slim and compact desktop speakers that can hit as hard as the Z623 system and clearing the floor would be nice, and I will make a serious attempt at that now. I can use these as DJ desk monitors for live use too
I'll go straight to trying to extract usable out a tiny box with the larger ZR12.4D. Once, I have ordered the modded mono FFA002 pair from Erica.C, I'll have 600wrms @4R x 2 to throw at that project
In the meantime, let's mark the Cub Sandwich project as parked as a false start. No point in making a good cab without a valid acoustic model. Let's move onto the next area that I wanted to trial the ZR6.4D
I need a good system in my smoking/digital studio/mini DJ studio chill space and have absolutely no space on the floor. Even something like the Z623 is too large a sub
Let's see if the ZR6.4D can serve here. The current sims show it can approach the Z623 in output and with a very smooth response. The driver is only 172mm wide and will fit nicely in a narrow desktop box. I like the idea of a pair of bass cabs as stands for a pair of 3" FR tops. Or even a two-way with these two drivers. Very inert boxes will be a must, so dual opposed PRs
One of my many sets of Z623s is currently used here. A boost is used on the lows to bring the lowest of bass guitar notes up to audible, while the overall volume knob is set very low
A nice looking pair of very slim and compact desktop speakers that can hit as hard as the Z623 system and clearing the floor would be nice, and I will make a serious attempt at that now. I can use these as DJ desk monitors for live use too
Like most subs designed for sound reinforcement use, the Keystone does not have flat response.
If I recall correctly, the 45" x 26.5" x 22.5" Keystone loaded with 2 Lab 12 does around 128dB at 40Hz at 300 watts, rising to 135dB ~110Hz.
It could do 103dB dB at 40Hz with under 4 watts.
Loaded with the BC SW115-4, sensitivity is slightly less, with smoother response, less thermal compression, and more output potential.
The 2x12 LAB12 Keystone is about +5dB at 40Hz and +14dB ~110Hz compared to the same drivers in a bass reflex of half the size with the same low corner frequency.
Though a pair of the BR have slightly more LF (using double the power) they can't come close to the upper bass output of the Keystone.
The Keystone Loaded with the BC 18SW115-4 has very similar sensitivity to the JBL SRX728S "98 dB 1w@1m":
The above outdoor ground plane tests using a BW25Hz HP and 125Hz LP filter were done with identical power level, sub position and test mic, "0dB" =96dB, if JBL's specification sheet is correct.
Note that JBL stops response at 200Hz, avoiding depicting the port resonance ~225Hz
Though nearly the same sensitivity, the Keystone with one BC 18SW115-4 has considerably more output potential due to it's Xmax being almost double that of the JBL SRX28 drivers.
Art
If the floor is full, why not hang it from the ceiling?
Or place it under your chair..
Bit occupied at the moment but thanks for the info. I’ll go through that table matching hearing levels over the frequency range and see what can happen on the porch
The volume of the heaving bed is used as safe storage for projects stock and in progress work, safe from kids
The current sub is on the floor and very much in the way of everything
I’m in a tiny home. Its a concrete floor and sandwich walls. The ceilings are composite sandwiches too. The chair is office type with my seating alternating between that and the “Heaving Bed”. Floor is too be kept clutter free
The volume of the heaving bed is used as safe storage for projects stock and in progress work, safe from kids
The current sub is on the floor and very much in the way of everything
One thing has become clear. I need to listen to some things with a meter on. It's very hard to know how loud a number is without any context
So if putting in a major effort for a flat response means it will be perceived by the ear as a falling response, then going back through various sub, multi and FR designs on the forum, I can't see anyone designing a rising LF response. They are usually drooping to a targeted F3
I do notice the bit about losses outdoors and room response augmentation or DSP or Eq compensation.......why is it so bad to just go for flat to the target frequency and compensate with whatever augmentation from the porch floor? Or use electronic compensation, or both? With the current sims at the driver's rated 300wrms and supported 600w peaks together with a 600wrms amp, can there be enough headroom to dial up a loudness curve in DSP to compensate for that falling ear response?
The next set of trials do not have a requirement for the system to get any louder than a z623 with the boost dial at unity in an indoor situation. Due to a wide glass door, the speakers/sub are in the corners either side of the main entrance and load with bass enough to not need boost, actually the boost knob is slightly turned down at the moment due to neighbours just hearing the kick in their bedrooms at late night when we can barely hear it 1m away
The ZR6.4D is beginning to look like something I haven't noticed in speakers before. It has this unusual 2.79L Vas for an LF unit. I think I can treat it like a type of rod that I had a part in developing that went on to be known as the modern butterfly jigger. This is a multi-stage rod. One stage is a fixed response to create the required action in a very heavy lure of around 300g about 100m or more down. The next stage is loading up on the fish. Here it shifts into another zone into the lower end of the rod and the rest folds away, This zone can load up to some tremendous pulls at a much shorter stroke. Bear in mind that from a rod engineer's point of view, the rod is a lever that the fish or bait has against you
How does this relate, well the ZR6.4D can match the z623, needs more power to do it, but it can and out of a smaller box too. And does all this as a much more inefficient driver under the rated driver Fs. It doesn't model as flapping away out of xmax or imploding into a black hole. The z623 has way too much output to turn up in this indoor location. Can the ZR6.4D be the basis for a high quality, quiet nearfield system that can go clean and low?
Let's try to measure the z623 and see how much output is being used in a normal and intense day and a normal night. This will be the SPL target with a bit of a headroom factored in. We will start the next trails with sims first and see if it is worth building a new nearfield desktop monitors for a DJ producer type home studio and chilling
So if putting in a major effort for a flat response means it will be perceived by the ear as a falling response, then going back through various sub, multi and FR designs on the forum, I can't see anyone designing a rising LF response. They are usually drooping to a targeted F3
I do notice the bit about losses outdoors and room response augmentation or DSP or Eq compensation.......why is it so bad to just go for flat to the target frequency and compensate with whatever augmentation from the porch floor? Or use electronic compensation, or both? With the current sims at the driver's rated 300wrms and supported 600w peaks together with a 600wrms amp, can there be enough headroom to dial up a loudness curve in DSP to compensate for that falling ear response?
The next set of trials do not have a requirement for the system to get any louder than a z623 with the boost dial at unity in an indoor situation. Due to a wide glass door, the speakers/sub are in the corners either side of the main entrance and load with bass enough to not need boost, actually the boost knob is slightly turned down at the moment due to neighbours just hearing the kick in their bedrooms at late night when we can barely hear it 1m away
The ZR6.4D is beginning to look like something I haven't noticed in speakers before. It has this unusual 2.79L Vas for an LF unit. I think I can treat it like a type of rod that I had a part in developing that went on to be known as the modern butterfly jigger. This is a multi-stage rod. One stage is a fixed response to create the required action in a very heavy lure of around 300g about 100m or more down. The next stage is loading up on the fish. Here it shifts into another zone into the lower end of the rod and the rest folds away, This zone can load up to some tremendous pulls at a much shorter stroke. Bear in mind that from a rod engineer's point of view, the rod is a lever that the fish or bait has against you
How does this relate, well the ZR6.4D can match the z623, needs more power to do it, but it can and out of a smaller box too. And does all this as a much more inefficient driver under the rated driver Fs. It doesn't model as flapping away out of xmax or imploding into a black hole. The z623 has way too much output to turn up in this indoor location. Can the ZR6.4D be the basis for a high quality, quiet nearfield system that can go clean and low?
Let's try to measure the z623 and see how much output is being used in a normal and intense day and a normal night. This will be the SPL target with a bit of a headroom factored in. We will start the next trails with sims first and see if it is worth building a new nearfield desktop monitors for a DJ producer type home studio and chilling
Help me make sense of this one. From comments, I got the impression that the mid bass hump is not desirable and from what you say, the drooping low response will be even worse with the ears loudness perception. That's a 7db hump or 7db droop, is that designed in or is that how much legs the driver has?
For that matter, unless the rooms are guaranteed to provide rising LF gain of 10db or more, most frequency response models and measurements that I see online should be whisper quiet low bass as heard by the ear when compared to upper bass and that most designers prefer to reproduce an attenuated version of the material in the recording then that the producer intended
Nothing is near 65-80 dB at 1kHz in post #47.
The black (SMAART) graphs go to 125Hz and ~250Hz.
The different color traces are identified, the top three are the Keystone cabinet with different drivers, the lower two traces are bass reflex cabinets with the same low corner.
The JBL SRX728S graph is at one watt (2volts in to 4 ohms), the SMAART graph above compares the JBL SRX728 to the BC18 Keystone TH (tapped horn) both at the same drive level.
PA sub cabinets are designed for maximum output in a given space, whether in transport, venue use, or storage.
Their response is always processed with HP, LP and parametric filters for the particular application.
As amp power and processing is now built in to many PA (or studio monitor) cabinets, the raw response or sensitivity is not specified.
Designing for flat response below 40Hz requires much larger cabinet volume than typically desired, so EQ is used to compensate for the rising upper response.
Since cone excursion is at minimum at Fb, plenty of boost can be applied around it without exceeding Xmax.
Much (most) of pop music bass is in the 60-120Hz range, having more sensitivity in that range reduces average power, reducing heating. Most subwoofer failures are thermal, rather than mechanical.
Of course it is once corrected for the ear sensitivity as per the loudness scale. The low end sits around 40-50hz about 105db on the yellow trace in that thread. So the actual perception would be similar to 1kz at between 65-80db. Thats a very droopy response once corrected for loudness scale
My bass is strung with BEAD and I see a few 5 strings live on Rototom stage
Let's leave correcting for the ear sensitivity scale for another time and as more understanding arrives. I spent the past hour getting some readings at my listening position. This is seated on the Heaving Bed, working on the keyboard and listening with the 2.1 Logitech Z623 at a distance of 1.8m from the sub and mains, Sub is in a corner, 60cm from the back wall, 30cm from the port side firing onto heavy block out curtains
Setup for readings
Playing back my normal daytime video playlist in Windows Media Player. WMP graphic Eq is normally set flat. I have taken down all but the last three sliders, with the highest being 125khz slider. These three are left at unity. Covered the mains with heavy blankets until mostly drowned out. Sub boost is left slightly below unity as normal. Z62333 main volume knob is set to half-way as normal, WMP volume is set to max as normal and system volume controlled from windows
Daytime level
With windows volume at 38. The SPL peaks around 60db with music
Evening level
With windows volume at 16. The SPL peaks around 56db with music
Late night level
With windows volume at 12. The SPL peaks 50db with music
A 40hz tone is just becoming solidly audible at 39db and I can feel it through the body as well and the audible perception rises and peaks at over 80hz but starts diminishing by 90hz
There may be issues related to the SPL meter app and the frequency response of the iPhone internal mic but if the proposed 2.0 channel 2-way speakers can be developed to read just as well or better on the same equipment and settings than it would be a successful project......of course it needs to sound as good too
Setup for readings
Playing back my normal daytime video playlist in Windows Media Player. WMP graphic Eq is normally set flat. I have taken down all but the last three sliders, with the highest being 125khz slider. These three are left at unity. Covered the mains with heavy blankets until mostly drowned out. Sub boost is left slightly below unity as normal. Z62333 main volume knob is set to half-way as normal, WMP volume is set to max as normal and system volume controlled from windows
Daytime level
With windows volume at 38. The SPL peaks around 60db with music
Evening level
With windows volume at 16. The SPL peaks around 56db with music
Late night level
With windows volume at 12. The SPL peaks 50db with music
A 40hz tone is just becoming solidly audible at 39db and I can feel it through the body as well and the audible perception rises and peaks at over 80hz but starts diminishing by 90hz
There may be issues related to the SPL meter app and the frequency response of the iPhone internal mic but if the proposed 2.0 channel 2-way speakers can be developed to read just as well or better on the same equipment and settings than it would be a successful project......of course it needs to sound as good too
@weltersys
Art, thanks a lot for your generosity with your time, guidance and education. Much appreciated and I am very grateful. Please excuse any oddness on my behalf. I know I have spoken a lot from misconceptions and errors in data. Now let's see if your patience will pay off and if I have learned enough to attempt an elegant implementation with this driver. Looking something like this at the moment for one side of the stereo pair. For the SPL estimation, do I add 3db or 6db for the second cab? It will have its own amp. Project signal is 1w and 10db boost at 42hz. Amp will be 300wrms mono for the LF unit and 100wrms mono for the HF unit in the active two-way with DSP
Would really appreciate your thoughts on these results on meeting or exceeding the current listening position results? Would this have the potential to develop a low reaching and nearfield mini Dj studio monitors with? Am I now correctly modelling for ear sensitivity/efficiency losses to accurately monitor the bass instruments?
I am also making the assumption that room loading will further augment this bass response and I would be able to properly use DSP as ballast and take away rather than add thus further improving things like group delay and excursion thus improving distortion numbers?
Art, thanks a lot for your generosity with your time, guidance and education. Much appreciated and I am very grateful. Please excuse any oddness on my behalf. I know I have spoken a lot from misconceptions and errors in data. Now let's see if your patience will pay off and if I have learned enough to attempt an elegant implementation with this driver. Looking something like this at the moment for one side of the stereo pair. For the SPL estimation, do I add 3db or 6db for the second cab? It will have its own amp. Project signal is 1w and 10db boost at 42hz. Amp will be 300wrms mono for the LF unit and 100wrms mono for the HF unit in the active two-way with DSP
Would really appreciate your thoughts on these results on meeting or exceeding the current listening position results? Would this have the potential to develop a low reaching and nearfield mini Dj studio monitors with? Am I now correctly modelling for ear sensitivity/efficiency losses to accurately monitor the bass instruments?
I am also making the assumption that room loading will further augment this bass response and I would be able to properly use DSP as ballast and take away rather than add thus further improving things like group delay and excursion thus improving distortion numbers?