This could very well be a little bit underwhelming. However, I have a Tropo 10in that I would like to switch since it is an under the seat box. The box has .85 cuft sealed, now that's the problem. I understand .85 isn't crazy, but this subwoofer calls for 1 cuft ported. I've been doing some models on SpeakerBoxLite ( I don't have WinISD) and it seems very promising. However, the port is the current issue; I am not fully set on a design just yet because of port velocity. Also, I think there are better minds on here that might be able to help. I have a 3d printer, so I can build any type of port. The truck that it is in right now is a 2018 Ram, I was thinking of making that long part of the box into the port but I am open to suggestions. If a port came out the back side I would have the ability to have part of the port outside the box. I want to aim for 38hz, since that seems to be the best for a flat line. However, it has 30m/s port velocity. Which I know can affect the performance of the sub.
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Which Tropo subwoofer 10-inch driver are you using? Is it the one with Qts=0.502 or the one with Qts=0.408?
Also, does your amplification have any provision for applying some parametric EQ in the low frequencies between 20Hz and 40Hz?
You might consider downloading and using VituixCAD. It has a very flexible simulator to help study low-frequency alignments associated with woofers.
Also, does your amplification have any provision for applying some parametric EQ in the low frequencies between 20Hz and 40Hz?
You might consider downloading and using VituixCAD. It has a very flexible simulator to help study low-frequency alignments associated with woofers.
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I have the dual 2 ohm version, which says to have a Qts=0.612
My amp which is a D4S JP8, only has lowpass and Subsonic and thank you for the suggestion I'll check it out. I think even if I tuned it to 50hz it would be way better then being sealed.
My amp which is a D4S JP8, only has lowpass and Subsonic and thank you for the suggestion I'll check it out. I think even if I tuned it to 50hz it would be way better then being sealed.
Thanks. I found the Tropo specifications for your driver with the Qts=0.612. I guess you'll be connecting it 2//2 = 1-ohm load? Your amplifier seems to be rated down to 1-ohm.
The D4S JP8 amplifier appears to have the following filters.
Low-Pass Filter: 35Hz – 250 Hz
Subsonic Filter: 10Hz – 50 Hz
Bass Boost: 0–9 dB
I guess that the infrasonic (also known as "subsonic") high-pass filter is a second-order peaking filter, with adjustable Q. This would allow it to achieve +6dB of boost when Q=2.0 when set appropriately.
I would be worth contacting someone at D4S to confirm how that Bass Boost is implemented, just to be sure.
You have a 0.85cuft enclosure, which corresponds to 24 litres. That's quite small as far as vented enclosures go. If we chose a 7.5cm port diameter, it would result in a quite long port to try and keep the vent air velocity within typical guidelines.
Here is a simulation of the driver in a vented-box enclosure, obtained using VituixCAD. The box volume is 24-litres, and the vent is tuned to 26Hz, using a 7.5cm diameter port of length 74cm. I've applied a 20Hz 2nd-order Butterworth high-pass filter to control the infrasonic cone excursion, as well as an 80Hz 2nd-order Butterworth low-pass filter. With a nominal 180W re 1ohm of input power, we get 105dB of SPL at the point where the vent air velocity has reached the first turbulence warning. The driver is still operating well short of its Xmax, so it could take a bit more input power.
The f3 of the vented-box alignment is 30.4Hz, which seems to be quite reasonable.
If we add a peaking 2nd-order high-pass filter to the existing subwoofer, we can get the following response. Here the infrasonic filter would likely need to be set to 30Hz, and the bass boost to +4.5dB or thereabouts. The simulated response has f3=29.5Hz, which is similar to that of the vented system modelled earlier. Note that we ae operating close to Xmax. You could give this set up a try to see if the simulation is reasonable.
The D4S JP8 amplifier appears to have the following filters.
Low-Pass Filter: 35Hz – 250 Hz
Subsonic Filter: 10Hz – 50 Hz
Bass Boost: 0–9 dB
I guess that the infrasonic (also known as "subsonic") high-pass filter is a second-order peaking filter, with adjustable Q. This would allow it to achieve +6dB of boost when Q=2.0 when set appropriately.
I would be worth contacting someone at D4S to confirm how that Bass Boost is implemented, just to be sure.
You have a 0.85cuft enclosure, which corresponds to 24 litres. That's quite small as far as vented enclosures go. If we chose a 7.5cm port diameter, it would result in a quite long port to try and keep the vent air velocity within typical guidelines.
Here is a simulation of the driver in a vented-box enclosure, obtained using VituixCAD. The box volume is 24-litres, and the vent is tuned to 26Hz, using a 7.5cm diameter port of length 74cm. I've applied a 20Hz 2nd-order Butterworth high-pass filter to control the infrasonic cone excursion, as well as an 80Hz 2nd-order Butterworth low-pass filter. With a nominal 180W re 1ohm of input power, we get 105dB of SPL at the point where the vent air velocity has reached the first turbulence warning. The driver is still operating well short of its Xmax, so it could take a bit more input power.
The f3 of the vented-box alignment is 30.4Hz, which seems to be quite reasonable.
If we add a peaking 2nd-order high-pass filter to the existing subwoofer, we can get the following response. Here the infrasonic filter would likely need to be set to 30Hz, and the bass boost to +4.5dB or thereabouts. The simulated response has f3=29.5Hz, which is similar to that of the vented system modelled earlier. Note that we ae operating close to Xmax. You could give this set up a try to see if the simulation is reasonable.
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The following simulation in VituixCAD is of the infrasonic filter in the D4S JP8 amplifier using the assumption that it is a 2nd-order high-pass peaking filter. I've adjusted the boost to equal +6dB. From left to right, the set of 7 curves corresponds to frequency settings of 10Hz, 15Hz, 20Hz, 25Hz, 30Hz, 35Hz, and 40Hz. These are within the 10–50Hz operating range of the infrasonic filter (I chose to leave out the 45Hz and 50Hz settings as the graph was getting quite busy!).
With the Bass Boost control set to 0dB, all of the above filter functions would then likely turn into 2nd-order Butterworth high-pass filters with −3dB points corresponding to the frequency setting of the infrasonic filter on the amplifier.
With the Bass Boost control set to 0dB, all of the above filter functions would then likely turn into 2nd-order Butterworth high-pass filters with −3dB points corresponding to the frequency setting of the infrasonic filter on the amplifier.
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Sorry I've been busy with Finals just recently. Man, you are way more experienced than me. Just wondering why would you tune the sub so low, also sidenote 7.5cm diameter sadly would not be possible. I believe that the long part of the box has about an inch between the top panel and bottom panel. I believe with the restraint I would have to go with a slot port. However, I will be raising my seat an inch, so I can try an L shaped port out the top or just a port coming out the right or backside. Now the sub box(on the long part) is about 11 inch wide (front to back(side A) and about 18inches from the Side B to the subwoofer. On side A, I have around 10inches of room before it hits the back of the cab. On side b I have about 2-3 inches before it hits a seat mount (this is the longer side tho, so I believe it might be better for a port and simpler. Also another question, is the reasoning for increasing the bass boost and limiting the subsonic due to xmax limit at lower freq air velocity, just curious. Thank you for all your help, I am not used to getting the most out of a port and all the science.
I chose a low tuning (fb=26Hz) as I was assuming that the subwoofer's use case would be to have an extended low-frequency response.
The computed f3=30.4Hz would reproduce the heartbeat low-frequency signal on the first track of Pink Floyd's The Dark Side Of The Moon album, which happens to be right near there. 🙂 If playing the more modern track by Selena Gomez titled "I Can't Get Enough", then we have significant 29-Hz signal content. See the frequency analysis shown below of the whole of that track.
Of course, your description indicates that such a low vent tuning frequency does not seem to be viable in your situation.
If you tune the enclosure for fb=50Hz, you are going to get a very peaky response from your subwoofer. That's a result of its combination of Thiele–Small parameter. The high Qts value of the Tropo-10 driver does not go well with that high a value of fb. For the 50-Hz tuning, the natural unfiltered response looks like the following, with a big +5dB peak near 60Hz. This is likely to produce "one note" bass, and little if any effective bass extension.
The lowest tuning that I would aim for with this driver would be 35Hz. This produced the following results, with both the low-pass and high-pass filters active. Compared to the fb=26Hz tuning case, here the f3 is much higher at 36.2Hz. Of course, this tuning results in a much shorter vent than before: Lv = 38.4cm for Dv = 7.5cm.
The computed f3=30.4Hz would reproduce the heartbeat low-frequency signal on the first track of Pink Floyd's The Dark Side Of The Moon album, which happens to be right near there. 🙂 If playing the more modern track by Selena Gomez titled "I Can't Get Enough", then we have significant 29-Hz signal content. See the frequency analysis shown below of the whole of that track.
Of course, your description indicates that such a low vent tuning frequency does not seem to be viable in your situation.
If you tune the enclosure for fb=50Hz, you are going to get a very peaky response from your subwoofer. That's a result of its combination of Thiele–Small parameter. The high Qts value of the Tropo-10 driver does not go well with that high a value of fb. For the 50-Hz tuning, the natural unfiltered response looks like the following, with a big +5dB peak near 60Hz. This is likely to produce "one note" bass, and little if any effective bass extension.
The lowest tuning that I would aim for with this driver would be 35Hz. This produced the following results, with both the low-pass and high-pass filters active. Compared to the fb=26Hz tuning case, here the f3 is much higher at 36.2Hz. Of course, this tuning results in a much shorter vent than before: Lv = 38.4cm for Dv = 7.5cm.
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In relation to the vented-box response simulations that I provided, I did not offer a case where there was any bass boost being provided by the infrasonic ("subsonic") filter. That filter was being applied in pure high-pass-only mode. It was there to reduce the driver excursion at frequencies below the vent tuning frequency, fb, which might otherwise occur if there is energy in the signal in that lower frequency range. The woofer would oscillate a lot, but little to no sound would be produced, due to port–driver cancellation effects.
For example, if the vent was tuned to 50Hz, what would happen when reproducing the Selena Gomez track? Well, the two main bass peaks in that song are at 29Hz and 44Hz. The 29Hz peak is a tad higher in level than the one at 44Hz. Any 29Hz signal would result in a lot of cone movement but essentially no sound output. If the amplifier is cranked up, the woofer would be flailing around, going through very large excursions, which could bottom it out. The infrasonic filter would need to be set to about 40Hz to protect the driver from excessive displacement in the vented system tuned to 50Hz or so.
I can see that you noticed that the high-pass filter reduced the vent air velocity as well as reducing the driver displacement. The reduction in vent air velocity below fb is of only secondary concern, as it is the peak in the vent air velocity that we need to try and keep in check as much as possible.
For example, if the vent was tuned to 50Hz, what would happen when reproducing the Selena Gomez track? Well, the two main bass peaks in that song are at 29Hz and 44Hz. The 29Hz peak is a tad higher in level than the one at 44Hz. Any 29Hz signal would result in a lot of cone movement but essentially no sound output. If the amplifier is cranked up, the woofer would be flailing around, going through very large excursions, which could bottom it out. The infrasonic filter would need to be set to about 40Hz to protect the driver from excessive displacement in the vented system tuned to 50Hz or so.
I can see that you noticed that the high-pass filter reduced the vent air velocity as well as reducing the driver displacement. The reduction in vent air velocity below fb is of only secondary concern, as it is the peak in the vent air velocity that we need to try and keep in check as much as possible.
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I'd like to make a suggestion, which is based around the flexibility offered by your present D4S JP8 amplifier (it seems a very flexible, well designed unit). Just go with the driver in the as-is closed-box enclosure; there's no need to deal with the intricacies of introducing a port.
The Tropo-10 has a quite high Qts=0.612, a moderately large diameter, and a small Vas. This tends to make it a more suitable candidate for use in the available compact closed-box enclosure. All that you'll lose is a little bit of maximum output level, but you won't have to deal with any port noises at high input powers.
Below is one possible closed-box enclosure solution, designed with lots of low-frequency extension in mind. It includes about +4dB of peaking boost coming from the appropriate setting of the infrasonic filter to 25Hz and the bass boost to +4dB. These are facilities offered by your power amplifier. Here f3=25.9Hz, with a rounded knee, which will make use of the available "cabin gain" at those low frequencies. Peak SPL output is 100dB for 75W re 1.0ohms. The actual power dissipation is less than that, as a result of all the filtering that's going on. The driver's Xmax is reached at 25.9Hz.
Another tuning option, shown below, produces a maximum SPL of 102dB, with an f3=29.5Hz. This includes +4dB of bass boost when the infrasonic filter is set to 30Hz. That's still a good result for a "subwoofer".
If we wish to trade off a little bit more low-frequency extension for a higher maximum output level, then the following alignment can be considered. It produces a maximum SPL of 104dB when Xmax is reached, using an input power of 125W re 1.0ohms. The infrasonic filter was set at 35Hz with +4dB of bass boost. This is also a quite good result.
The Tropo-10 has a quite high Qts=0.612, a moderately large diameter, and a small Vas. This tends to make it a more suitable candidate for use in the available compact closed-box enclosure. All that you'll lose is a little bit of maximum output level, but you won't have to deal with any port noises at high input powers.
Below is one possible closed-box enclosure solution, designed with lots of low-frequency extension in mind. It includes about +4dB of peaking boost coming from the appropriate setting of the infrasonic filter to 25Hz and the bass boost to +4dB. These are facilities offered by your power amplifier. Here f3=25.9Hz, with a rounded knee, which will make use of the available "cabin gain" at those low frequencies. Peak SPL output is 100dB for 75W re 1.0ohms. The actual power dissipation is less than that, as a result of all the filtering that's going on. The driver's Xmax is reached at 25.9Hz.
Another tuning option, shown below, produces a maximum SPL of 102dB, with an f3=29.5Hz. This includes +4dB of bass boost when the infrasonic filter is set to 30Hz. That's still a good result for a "subwoofer".
If we wish to trade off a little bit more low-frequency extension for a higher maximum output level, then the following alignment can be considered. It produces a maximum SPL of 104dB when Xmax is reached, using an input power of 125W re 1.0ohms. The infrasonic filter was set at 35Hz with +4dB of bass boost. This is also a quite good result.
Alright thank you so much, a lot of information I am learning from you and I will definitely put theses to the test tomorrow. I did forget to mention that the box has polyfill on the inside walls, I don't know if that changes anything. Now quick question, the wattage that is being plugged in here, is that input signal to the amp or the output signal.
You're very welcome; I'm trying to help as best I can and am learning a bit about tuning these closed-box subwoofer alignments using car audio amplifiers.
The wattage that I am using is the output signal. Using the 125W re 1.0ohms example, this corresponds to an output voltage at the amplifier's speaker terminals of 11.18V. This voltage is what remains relatively constant while the amplifier supplies the current needed by the impedance of the speaker load, which varies as a function of frequency.
If the box has polyfill on the inside walls, that won't make a big difference to the tuning. Compared to the no-fill case, adding some polyfill increases the "effective" volume of the enclosure, making the volume seen by the driver greater than the physical volume. Using polyfill in this way does alter the tuning a little, by lowering the system resonance frequency of the driver. If the polyfill only lines the inside walls rather than filling the entire enclosure, the effect would be relatively small.
The wattage that I am using is the output signal. Using the 125W re 1.0ohms example, this corresponds to an output voltage at the amplifier's speaker terminals of 11.18V. This voltage is what remains relatively constant while the amplifier supplies the current needed by the impedance of the speaker load, which varies as a function of frequency.
If the box has polyfill on the inside walls, that won't make a big difference to the tuning. Compared to the no-fill case, adding some polyfill increases the "effective" volume of the enclosure, making the volume seen by the driver greater than the physical volume. Using polyfill in this way does alter the tuning a little, by lowering the system resonance frequency of the driver. If the polyfill only lines the inside walls rather than filling the entire enclosure, the effect would be relatively small.
Note that when big and/or long vents aren't an option, make the max size/length and critically damp them to get the desired response, power handling or at least a pleasing performance.
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It appears that I have been barking up the wrong tree, probably in the wrong forest too.
I contacted D4S technical support to try and obtain some further information regarding the D4S JP8 amplifier. From what I was told, it appears to have the following filters:
Low-Pass Filter: 35Hz – 250 Hz, 2nd-order, 12dB/octave, Linkwitz–Riley (−6dB at the cut-off frequency)
Subsonic Filter: 10Hz – 50 Hz, 2nd-order, 12dB/octave, Linkwitz–Riley (−6dB at the cut-off frequency)
Bass Boost: 0–9 dB, centred on 45Hz with Q = 2.5
Using those parameters, a possible closed-box alignment would be as shown below. Here the high-pass and low-pass filters are set to 10Hz and 50Hz, respectively. No bass boost is applied (the PEQ1 setting is 0dB). With these settings, the response is −6dB at 94Hz relative to the peak SPL. As there is a great deal of complex interaction between the response of the driver and the response of the filter, that −6dB of 94Hz point doesn't correspond to the 40Hz setting of the low-pass filter. You can see that the maximum power input is 60W around 15Hz or so, while above 30Hz it stays below 14W.
By increasing the high-pass filter setting to 25Hz, we can obtain approximately 3dB more maximum output SPL when Xmax is reached. The response is −6dB at about 105Hz relative to the maximum SPL.
I contacted D4S technical support to try and obtain some further information regarding the D4S JP8 amplifier. From what I was told, it appears to have the following filters:
Low-Pass Filter: 35Hz – 250 Hz, 2nd-order, 12dB/octave, Linkwitz–Riley (−6dB at the cut-off frequency)
Subsonic Filter: 10Hz – 50 Hz, 2nd-order, 12dB/octave, Linkwitz–Riley (−6dB at the cut-off frequency)
Bass Boost: 0–9 dB, centred on 45Hz with Q = 2.5
Using those parameters, a possible closed-box alignment would be as shown below. Here the high-pass and low-pass filters are set to 10Hz and 50Hz, respectively. No bass boost is applied (the PEQ1 setting is 0dB). With these settings, the response is −6dB at 94Hz relative to the peak SPL. As there is a great deal of complex interaction between the response of the driver and the response of the filter, that −6dB of 94Hz point doesn't correspond to the 40Hz setting of the low-pass filter. You can see that the maximum power input is 60W around 15Hz or so, while above 30Hz it stays below 14W.
By increasing the high-pass filter setting to 25Hz, we can obtain approximately 3dB more maximum output SPL when Xmax is reached. The response is −6dB at about 105Hz relative to the maximum SPL.
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Interesting, I might have to try that real world and see. I tried the other way you suggested and I will say it is impressive for what it is, nothing like my 12in though sadly. I was doing some models on this software with a port and I would like to get your opinion on them.
This is with a 40cm^2 port area and 45cm length, I know the velocity is a bit higher. However, I'm sure this wouldn't draw too much concern knowing it is pointing to the back wall under a seat. I decided to play around with the filters(never did before) and made the velocity a tad lower. I did put 2 ohms, because that is how it is connect right now(probably will change) but I also know my amp will be able to put out 700-800rms at 2ohm.
Sidenote, I am not against a sealed enclosure whatsoever, I am just eager for the best output. Like I said I am use to my Audiopipe 12in and very sad to get rid of it. Thank you so much for your effort and teaching. I really appreciate it.
This is with a 40cm^2 port area and 45cm length, I know the velocity is a bit higher. However, I'm sure this wouldn't draw too much concern knowing it is pointing to the back wall under a seat. I decided to play around with the filters(never did before) and made the velocity a tad lower. I did put 2 ohms, because that is how it is connect right now(probably will change) but I also know my amp will be able to put out 700-800rms at 2ohm.
Sidenote, I am not against a sealed enclosure whatsoever, I am just eager for the best output. Like I said I am use to my Audiopipe 12in and very sad to get rid of it. Thank you so much for your effort and teaching. I really appreciate it.
In your Tropo 10 driver specifications, the Rms value is 0.01. That is way too small, and doesn't match up with the Qms value, from which it is derived. A more accurate value for Rms is 7.0, and it was calculated using the values of Sd, Fs, Qms, and Vas for the driver. Also, the Mms value that you have used is 0.29 grams, which is clearly incorrect; the CT Sounds data mentioned that Mms = 175.98g.
Those sorts of errors will cause your simulations to be quite inaccurate. I'll be interested to see the revised simulations.
The following parameter values for the driver are what I think are the correct ones, and I have used these in my simulations. Note that I calculated the value of Rms from the other parameters, as it wasn't provided by CT Sounds.
A 10-inch driver is often likely to be outperformed by a 12-inch driver for low-frequency extension and output. Just on radiating area alone, the 12-inch driver is about 40% bigger.
Those sorts of errors will cause your simulations to be quite inaccurate. I'll be interested to see the revised simulations.
The following parameter values for the driver are what I think are the correct ones, and I have used these in my simulations. Note that I calculated the value of Rms from the other parameters, as it wasn't provided by CT Sounds.
A 10-inch driver is often likely to be outperformed by a 12-inch driver for low-frequency extension and output. Just on radiating area alone, the 12-inch driver is about 40% bigger.
With the parallel connection, as per CT Sounds Thiele–Small driver parameters, here is a simulation of the response. This is with a Av = 40cm^2 port area and Lv = 45cm length, which matches your values. The vent tuning is fb = 31.1Hz in this configuration, with a vented-box enclosure volume of Vb = 24.0litres. Note that I adjusted the high-pass filter to be at 35Hz, rather than the 40Hz that you used, otherwise there was a bit too much attenuation of the low-frequency response occurring.
Can you clarify how the 2-ohm connection is going to work? Have you just connected up one of the driver coils? I'm not sure what's going on, and I note that the CT Sounds data corresponds to the 2 // 2 connection, producing the 1.08 Ω load that is defined in their datasheet.
Apologies for the wrong values, I got them corrected now thank you. The idea that I had for tuning it so high on the subsonic was due to the port velocity at around 1000-1200 watts ( I know it wouldn't be the consistently, but I figured it did still affect the subwoofer). Right now it is just hooked up to 2 connections, I believe, now I can also change it. (But I don't know how much that would affect it other than it's power, which there is more than enough) Also I do see what you are saying on the website it does only show both voice coils hooked up. However I must be running it at 1 ohm already, I do not remember entirely because it has been sitting basically all year. But when all said an done it will be hooked up as 1 ohm.
This one I tried bass boost of 3db on it with the subsonic= 35hz and highpass= 55hz, understanding that the velocity is a tad bit up there. However, I do not know how bad that is since it is at 26hz and I am sure that would not hurt the sub.
This one is with the subsonic at 40hz and lowpass at 55hz with the 3db boost. I figured since it is at 45hz like you said that it should not kill the port velocity, but I am unsure. Also this is the port area in my picture, I don't know exactly why it is 1 hz difference. Peaks at 47hz with 108db.
I think taking the model you just made is probably the best option right now, it is a tad louder than a sealed enclosure and still has a low port velocity.
Once again apologizes for the confusion and thank you for your patience and help.
This one I tried bass boost of 3db on it with the subsonic= 35hz and highpass= 55hz, understanding that the velocity is a tad bit up there. However, I do not know how bad that is since it is at 26hz and I am sure that would not hurt the sub.
This one is with the subsonic at 40hz and lowpass at 55hz with the 3db boost. I figured since it is at 45hz like you said that it should not kill the port velocity, but I am unsure. Also this is the port area in my picture, I don't know exactly why it is 1 hz difference. Peaks at 47hz with 108db.
I think taking the model you just made is probably the best option right now, it is a tad louder than a sealed enclosure and still has a low port velocity.
Once again apologizes for the confusion and thank you for your patience and help.
@addam There is a 1Hz difference in the port tuning frequency because our two enclosure models use different values of Qa (absorption loss) and Ql (leakage loss). I used Qa=50 while you used Qa=20 (a higher loss), and I used Ql=7 while you used Ql=100 (a much lower loss).
The settings that you've chosen seem to be producing a relatively narrow response from your subwoofer. If that's the aim, then that's a reasonable choice of settings. I tend to favour a broader and flatter response from a subwoofer, as it's usually called upon to deliver a wider range of frequencies than those occurring near a peak in its response.
The settings that you've chosen seem to be producing a relatively narrow response from your subwoofer. If that's the aim, then that's a reasonable choice of settings. I tend to favour a broader and flatter response from a subwoofer, as it's usually called upon to deliver a wider range of frequencies than those occurring near a peak in its response.
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