You need after breaking in to measure acurate T&S t sim if you want low end imho, that is less usefull if you use it for the midrange only. But if you construcct the box bigger it is easy to full in with plain material to reduce the volume later. Increasing artificially a volume with fiber material as far I understood is only for sealed volume and up to +20% something. You want BR, if you can't measure, trust good third party T&S measurements or make the load bigger to have not to remake it 🙂. Your friend put the red line : follow that to shape your low end, it will certainly be good enough, good low end enough and smoother integration with the room that a maximum flat magnitude and rapid dive of classic BR alignements. I.e. look at f6, f10... Sealed works like that with slow 12db slope, you can mimic that but have a lower extension thanks to the BR... perhaps. I am not a specialist, but understood it has to be tested 🙂
I believe all the guys I listed above used sim for the bass magnitude if I am exact, cause it is almost impossible to make it rigth in home rooms, I mean you measure the bass of the room, and the mic near tye port is not really acurate.
From the OSMC thread, you can read the challenge was to have good T&S auto measurement good enough to make good sims enough, then final tunning was finished with playing a little with the port length in the final listening room. I assume the filter does its thing also in the final result. Active DSP is surely a plus here due to the price of passive parts today.
Well that's the theory, certainly harder for real, will see that when I start my own 12PR320 BR inspired by the guys above, I should end in the same balls-park with few crossover difference imo...
I believe all the guys I listed above used sim for the bass magnitude if I am exact, cause it is almost impossible to make it rigth in home rooms, I mean you measure the bass of the room, and the mic near tye port is not really acurate.
From the OSMC thread, you can read the challenge was to have good T&S auto measurement good enough to make good sims enough, then final tunning was finished with playing a little with the port length in the final listening room. I assume the filter does its thing also in the final result. Active DSP is surely a plus here due to the price of passive parts today.
Well that's the theory, certainly harder for real, will see that when I start my own 12PR320 BR inspired by the guys above, I should end in the same balls-park with few crossover difference imo...
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I use Unibox a lot. You should not focus on the thermal power handling rating, but on the output you want. This is because mechanical power handling is much less.
I usually model for 100dB or even 105dB, and 110dB for subs if possible. There is really no need to exceed these numbers unless using them in a VERY large room meant for PA drivers. You also should factor in about 0.5 to 0.8 ohms for the DCR of the lowpass coil and wiring in most cases in the box model. Just don't do this twice and add too much in the multistage process with your files.
I watch xmax, port Mach, and the response shape. In a vented box, try and keep the xmax hill above tuning below the peak spec. (Use 1.15 as the overdive percentage in the upper right box, as this shows xmax at 15% Distortion.) Below tuning drivers unload and rely on the suspension damping, but this is not usually represented well in the program. Tuning above or below Fsb is a matter of taste, results, expectations, and performance. Tuning to Fs reduces xmax the most. Below allows more extension, and above can be a target result.
Tune the box in an approx volume for desired output. If the response looks good or what your target is, check port diameter, Mach, and xmax. If exceeding xmax, you have 4 options: change damping, change tuning, change power input, or change box volume.
I usually leave power alone. Reduce volume a little, readjust tuning for response shape, and check damping type for best results. Is the port dia sufficient? IE, no "OBS!!!" Will the port fit in the box? If not, maybe a PR alignment will better suit. Always check a box smaller than what looks really good, as sometimes 5 Hz extension is not worth twice the box volume.
I can accept a different response at times and get around the issues presented by adjusting like this. If a driver cannot keep it's composure to 95dB, then it is not enough for a living room as designed and may need more than one driver.
I usually model for 100dB or even 105dB, and 110dB for subs if possible. There is really no need to exceed these numbers unless using them in a VERY large room meant for PA drivers. You also should factor in about 0.5 to 0.8 ohms for the DCR of the lowpass coil and wiring in most cases in the box model. Just don't do this twice and add too much in the multistage process with your files.
I watch xmax, port Mach, and the response shape. In a vented box, try and keep the xmax hill above tuning below the peak spec. (Use 1.15 as the overdive percentage in the upper right box, as this shows xmax at 15% Distortion.) Below tuning drivers unload and rely on the suspension damping, but this is not usually represented well in the program. Tuning above or below Fsb is a matter of taste, results, expectations, and performance. Tuning to Fs reduces xmax the most. Below allows more extension, and above can be a target result.
Tune the box in an approx volume for desired output. If the response looks good or what your target is, check port diameter, Mach, and xmax. If exceeding xmax, you have 4 options: change damping, change tuning, change power input, or change box volume.
I usually leave power alone. Reduce volume a little, readjust tuning for response shape, and check damping type for best results. Is the port dia sufficient? IE, no "OBS!!!" Will the port fit in the box? If not, maybe a PR alignment will better suit. Always check a box smaller than what looks really good, as sometimes 5 Hz extension is not worth twice the box volume.
I can accept a different response at times and get around the issues presented by adjusting like this. If a driver cannot keep it's composure to 95dB, then it is not enough for a living room as designed and may need more than one driver.
Room gain is more theoretical, you'll normally encounter room modes which have both ups and downs.
Right, room gain begins around its longest eigenmode dimension, so a huge room by most folk's standards, but corner loading OTOH can reach +9 dB in theory IF the room's construction is sufficiently rigid/massive.
Do you mean broadband, without changing bass extension?
As you say, the size is a factor. Theoretical room gain requires a room without loss, but rooms tend to be lossy, too much so.
As you say, the size is a factor. Theoretical room gain requires a room without loss, but rooms tend to be lossy, too much so.
?? Indeed! Started to post more, but the length alone means few folks here will ever meet the primary goal, so moved on, but if one has a below grade concrete basement/bunker or similar...........
Even flexible walls with a limit to their excursion can theoretically behave as airtight at DC, which is a criterion for room gain.
In any case, if there's a point to be made it's probably that you will need to consider your room in order to see what you get at lower frequencies. Clearly some of this can be seen theoretically, but it will come down to measurements.
In any case, if there's a point to be made it's probably that you will need to consider your room in order to see what you get at lower frequencies. Clearly some of this can be seen theoretically, but it will come down to measurements.
For sure, I just pointed out a starting point that normally is the end of it on most audio related forums. 😉
I'm sorry that you were swept up in this GM, my problem is with the link provided by @diyiggy
OP then took room gain as creating bass extension, which in theory it would if it were an issue. What the link actually refers to is a modal issue which can work either way to extend or reduce bass extension, and in any case can cause a rough response.
OP then took room gain as creating bass extension, which in theory it would if it were an issue. What the link actually refers to is a modal issue which can work either way to extend or reduce bass extension, and in any case can cause a rough response.
What does this mean? Can you please explain the "Xmax hill" in one of my graphs in the starting post, for instance? And what's "peak spec"?
i have called that honeycom in my post, but the word is not acurate as the peaks and nulls are not as tigth from each others as with the high frequencies the word is usually used for. As said Allen, the good word is "room modes," typically nodes of "pressure" or not making spl dips and peaks according size and shape of the room at different locations. you can play a little with that by speakers and listening chair position...
I really do not know how to measure acuratly a room for those modes with a simple mic and low spl signals, i.e. the gears we usually have to measure our drivers and loudspeakers. I remember there is something related to this in REW if I am correct but do not know if it's is acurate... IMO here for most of the noobs in which camp I am.
Click the tab at the bottom for your model, vented please. Scroll down to the xmax plot. The red line should be at driver xmax plus 15% if you set your dynamic overdrive to 1.15.
The xmax curve should come in high on the left below tuning and fall to a minimum dip at the tuning you chose. Just higher in frequency should be a small hill above tuning. I try to keep this area at rated xmax +15% and not higher than the red line. Lower the tuning and the hill rises. Raise tuning and the hill decreases. Above the hill, the driver should be well below xmax and not an issue.
Below resonance, port is just leakage.
Cone excursion is very high since the system is un loading
Lower tunings prevents the box from unloading faster
" The Hill " gets smaller if you tune high...yes
But in reality power handling just goes down
since higher tunings just cause the box to unload faster.
seems most magically ignore the cone excursion graph below resonance.
Problem with most software.
Incredible tools and basic formulas to find a ideal volume
for a drivers mechanical ability.
then the main cause for people to over analyze the info
Speaker is, what a speaker is.
With floor, ceiling and walls etc etc.
response looks nothing like the simulator transfer function
Software quickly gives you best volume for drivers
mechanical property. The more important part.
Vent doesnt really need to be tuned 3 to 5 Hz above or below drivers free air resonance.
Unless you want to tune extremely low so it behaves more similar to a sealed box
as far as not having massive amounts of unloading.
Otherwise it has been and always will be a hole in a box.
And just needs to be tuned to only be a hole ( leakage) close to free air resonance.
Otherwise as long as the box isnt to big or small.. that is it.
A speaker is what a speaker is.
So yes im agreeing to lower tuning.
Cone excursion is very high since the system is un loading
Lower tunings prevents the box from unloading faster
" The Hill " gets smaller if you tune high...yes
But in reality power handling just goes down
since higher tunings just cause the box to unload faster.
seems most magically ignore the cone excursion graph below resonance.
Problem with most software.
Incredible tools and basic formulas to find a ideal volume
for a drivers mechanical ability.
then the main cause for people to over analyze the info
Speaker is, what a speaker is.
With floor, ceiling and walls etc etc.
response looks nothing like the simulator transfer function
Software quickly gives you best volume for drivers
mechanical property. The more important part.
Vent doesnt really need to be tuned 3 to 5 Hz above or below drivers free air resonance.
Unless you want to tune extremely low so it behaves more similar to a sealed box
as far as not having massive amounts of unloading.
Otherwise it has been and always will be a hole in a box.
And just needs to be tuned to only be a hole ( leakage) close to free air resonance.
Otherwise as long as the box isnt to big or small.. that is it.
A speaker is what a speaker is.
So yes im agreeing to lower tuning.
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Thanks, I had not noticed this. I'll use this feature henceforth. No need to put a hard restriction on the linear Xmax as the cutoff.
Yes, I tried this, and played with it. I now understood what you meant by the "hill", and I can see that with a higher box tuning. But when playing with it, I realised that with the SB17NBAC drivers, if I try to keep the "hill" below the red Xmax line, then I have to tune too high, and other artefacts showed up. See the basic T/S parameters of the driver below. Note the "Linear Cone Overdrive" set to 1.15 in the top right corner.
With these, I set up a vented box, 18 litres volume, and box tuning high enough (it's at 60Hz) to get the hill to fall below the red line
But once I do this, I get this response graph:
In this response, I'm getting a 5dB peak at 70Hz, and the gap between the red Xmax line and the blue "unlimited" SPL line is quite large at 70Hz ... it's about 10dB.
So, I'm not comfortable with this big peak, and I'm wondering what I've achieved with this if the "unlimited" SPL at 70Hz is so much higher than the Xmax limit. What would you suggest I do?
Huge peak, otherwise high Q, such as a filter response having high Q
is a box too small , or tuning too high
Just a Quick eyeball of posted specs
Driver Fs is 30 Hz
and Vas is 42 liters
So 60 Hz tuned way too high
and 18 liters is way too small.
Not having calculated Efficiency Bandwidth Product
If the enclosure posted was " Auto Calculated"
to common QB3 or C4 vented or reflex alignments in the software.
And it is giving very high tunings, or weird box sizes.
It could also be likely this speaker was designed to be in
a sealed box. And also designed to seem to have more bass
by creating that peak, by design in a sealed box.
So some drivers with odd specialized mechanical behavior
might model strange in a vented application. Since the software
will come up with strange numbers attempting to "align" the driver according
to theory. But otherwise EBP might be low and suited for sealed.
Even in some cases still have high enough EBP for vented.
But otherwise more suited sealed.
If the driver shows same peak in a sealed box and even a large
sealed box. The peak like some" sealed" drivers was intentional by design.
Or as mentioned if suitable for vented application.
Tuning is way too high and box way too small.
is a box too small , or tuning too high
Just a Quick eyeball of posted specs
Driver Fs is 30 Hz
and Vas is 42 liters
So 60 Hz tuned way too high
and 18 liters is way too small.
Not having calculated Efficiency Bandwidth Product
If the enclosure posted was " Auto Calculated"
to common QB3 or C4 vented or reflex alignments in the software.
And it is giving very high tunings, or weird box sizes.
It could also be likely this speaker was designed to be in
a sealed box. And also designed to seem to have more bass
by creating that peak, by design in a sealed box.
So some drivers with odd specialized mechanical behavior
might model strange in a vented application. Since the software
will come up with strange numbers attempting to "align" the driver according
to theory. But otherwise EBP might be low and suited for sealed.
Even in some cases still have high enough EBP for vented.
But otherwise more suited sealed.
If the driver shows same peak in a sealed box and even a large
sealed box. The peak like some" sealed" drivers was intentional by design.
Or as mentioned if suitable for vented application.
Tuning is way too high and box way too small.
In the last graph, see the 100dB horizontal like. On the Y-axis, we can see the 100dB power output. If you see this horizontal like, it cuts the red Xmax line at 70Hz. This means that I'll get flat frequency response (X-max limited) down to 70Hz, and then the SPL will slope down at 12dB/oct? So, there will be an F3 of abut 60 Hz?
Or is there something else I need to do to change the design to get better bass extension without this huge 10dB gap between Xmax and unlimited SPL?
Great. Thanks.
Can you give me any other tuning where I can get bass extension better than a sealed box with Q=0.7, and still have a gap between the "unlimited" SPL and the Xmax-limited SPL at something reasonable, like 5dB?
That was after all the original intent of my starting this thread. Basically, what tuning should I use to avoid damage to the driver in actual use due to over-excursion, and yet get decent bass extension?
This is what I like about Basta! Same woofer, 26-ish liter enclosure, vent tuning 35Hz. What you see is the max output level and the max drive voltage per frequency, regarding Xmax. Since music doesn't have a linear response, this is what is relevant to me.
If you're worried about LF excursion damage, use a B6-tuning (Keele) or DSP, with appropriate tuning of the reflex port. That is more than enough protection for domestic situations.