For what its worth, i have bought that driver and built a vented enclosure for it. Ive done a few tests and in a 9 cubic in box, it will shake the earth given enough power is driven into it.
I think the best i could manage was 105db @25hz
Im pretty sure if you built a bigger box and tuned it lower than i have (which was 23hz) you could get some pretty serious numbers with it, of course with that driver you can just throw SQ away.
I think the best i could manage was 105db @25hz
Im pretty sure if you built a bigger box and tuned it lower than i have (which was 23hz) you could get some pretty serious numbers with it, of course with that driver you can just throw SQ away.
Great! Well, I've bought one now so lets hope so.
As for the tuning, will this demarcate the lowest possible frequency I can produce?
I'm wondering how the tuning will effect its capabilities, for instance if I'm probably mainly going to want to be producing sine tones at around 18hz, does this mean it's best to tune to a couple of hz lower so it produces the 18hz comfortably? Will tuning it reeeally low, say to 5hz, affect its performance for higher frequencies?
I ask this as if there's a rule of thumb that can be applied... I realise this kind of thing might have to be determined by simulation.
As for the tuning, will this demarcate the lowest possible frequency I can produce?
I'm wondering how the tuning will effect its capabilities, for instance if I'm probably mainly going to want to be producing sine tones at around 18hz, does this mean it's best to tune to a couple of hz lower so it produces the 18hz comfortably? Will tuning it reeeally low, say to 5hz, affect its performance for higher frequencies?
I ask this as if there's a rule of thumb that can be applied... I realise this kind of thing might have to be determined by simulation.
I've just tried my hand at winisd but the specifications I've been given seem to omit certain details, or at least they're obscure to me... Re, Le, Pe, BL, dia, Sd, Z are all asked for but I can't see them in the table of info!
Here is all the info Inphase sent me earlier, will it be possible for me to calculate my enclosure size accurately? Or better yet... if anyone could tell me the volume I need for a 15hz tuned box I would be unbelievably grateful!
Dual 2ohm voice coil
Imp (Ohm): 4
Power (RMS): 1000
Voice Coil (size): 3.0"BASV/40
Magnet (pc x oz): 3x75oz
Dcr (ohm): 3.8
L (Mh): 6.935
Fs (Hz): 34.484
SD (msqM): 80.425
BL (TM): 24.61
Qms: 4.172
Qes: 0.447
Qts: 0.404
EBP (Hz): 85
n (%): 0.513
SPLo (db): 89.1
Vas (L): 57.783
Cms (mmm/N): 61.364
Mms (g): 347.136
Mmd (g): 333.774
Xmax (mm): 26
MD (mm): 205
OD (mm): 397
OH (mm):236
Md (mm): Φ379x8xΦ5.5
BC (mm): 353
Vd (L): 7.445
NW (Kgs): 16.5
Here is all the info Inphase sent me earlier, will it be possible for me to calculate my enclosure size accurately? Or better yet... if anyone could tell me the volume I need for a 15hz tuned box I would be unbelievably grateful!
Dual 2ohm voice coil
Imp (Ohm): 4
Power (RMS): 1000
Voice Coil (size): 3.0"BASV/40
Magnet (pc x oz): 3x75oz
Dcr (ohm): 3.8
L (Mh): 6.935
Fs (Hz): 34.484
SD (msqM): 80.425
BL (TM): 24.61
Qms: 4.172
Qes: 0.447
Qts: 0.404
EBP (Hz): 85
n (%): 0.513
SPLo (db): 89.1
Vas (L): 57.783
Cms (mmm/N): 61.364
Mms (g): 347.136
Mmd (g): 333.774
Xmax (mm): 26
MD (mm): 205
OD (mm): 397
OH (mm):236
Md (mm): Φ379x8xΦ5.5
BC (mm): 353
Vd (L): 7.445
NW (Kgs): 16.5
WinISD should auto calculate if you give it some inputs, just tab through it when you put something in and see what else you're missing. A lot of the stuff is not really 100% essential so if you read the help guide a list of necessities should be there.
You can tune any box to 15hz, all you need is the correct length and area for the port. For vented enclosures the driver becomes unstable under the tuning frequency, so to be safe its best to put a high pass filter right around your tuning frequency.
As to your question about the tuning frequency, the lower you go the less response you will get in the higher regions. It will sound muddy and the response will suffer to a certain extent.
It would help if you could tell us what kind of db you would want to hit at a certain frequency, from there an enclosure could be modeled to reach your goal (It most likely will be some crazy number like 4000 cubic inches)
Also i think i missed this, but what is the model name of the driver that you purchased?
1) Below Fb (box tuning) excursion rises rapidly, the speaker will "unload", flapping rather than making useful sound.
2) If you want to go below 18 Hz, tune lower, but at Fb the speaker excursion is lowest. The excursion increases to maximum about 1/3 octave above Fb, so tuning much lower would compromise the output at 18 Hz.
The further below Fs the Fb is, the less output for a given box size.
3) 5 Hz tuning is not practical, a sealed cabinet would give better performance.
T/S specs tutorial: TS Parameters (Thiele/Small Parameters) - Home Theater Forum and Systems - HomeTheaterShack.com
FYI, I just uploaded the WinISD Pro driver file, so install this much better version of WinISD, then DL the file into its ‘driver’ folder:
WinISD Pro Tutorial and Download (A detailed guide on how to use WinISD Pro) - Home Theater Forum and Systems - HomeTheaterShack.com
Downloadable WinISD Pro Files - Page 3 - Home Theater Forum and Systems - HomeTheaterShack.com
Once loaded, you’ll be able to look at the specs in the ‘driver editor’ and note which specs I inputted [green] and what specs it calculated [blue]. These often calculate different [and considered more accurate] basic T/S specs.
Note too that in this case [DVC], 'Re' [Dcr] tells us that the VCs are wired in series, so the number of VCs [2] and connection [series] must be set before loading Re, BL are inputted, otherwise you’ll get seemingly unsolvable errors no matter what you change when trying to save the file. I haven’t actually read its ‘help’ file or HTS’s tutorial, so there may be more info on the subject.
GM
FYI, I just uploaded the WinISD Pro driver file, so install this much better version of WinISD, then DL the file into its ‘driver’ folder:
WinISD Pro Tutorial and Download (A detailed guide on how to use WinISD Pro) - Home Theater Forum and Systems - HomeTheaterShack.com
Downloadable WinISD Pro Files - Page 3 - Home Theater Forum and Systems - HomeTheaterShack.com
Once loaded, you’ll be able to look at the specs in the ‘driver editor’ and note which specs I inputted [green] and what specs it calculated [blue]. These often calculate different [and considered more accurate] basic T/S specs.
Note too that in this case [DVC], 'Re' [Dcr] tells us that the VCs are wired in series, so the number of VCs [2] and connection [series] must be set before loading Re, BL are inputted, otherwise you’ll get seemingly unsolvable errors no matter what you change when trying to save the file. I haven’t actually read its ‘help’ file or HTS’s tutorial, so there may be more info on the subject.
GM
I wish I knew where to find that little plot from decades ago that shows Litres of cone displacement vs Frequency, with the SPL lines plotted over.
It shows how much Sd area times Xmax is needed for an SPL at any particular frequency.
An instant answer from where to start.
After you have sufficient cone displacement, either by going bigger driver or going to more drivers, you can then start designing a cabinet for an enclosed bass or infra sonic driver. But you could go infinite baffle or even open baffle. Both these do not need any cabinet.
It shows how much Sd area times Xmax is needed for an SPL at any particular frequency.
An instant answer from where to start.
After you have sufficient cone displacement, either by going bigger driver or going to more drivers, you can then start designing a cabinet for an enclosed bass or infra sonic driver. But you could go infinite baffle or even open baffle. Both these do not need any cabinet.
Darius, the speaker is the 'InPhase PowerDrive15 3000W 15" dual 2Ω voice coil subwoofer'.
I had been planning on building a sealed cabinet.... just from the impression I've got from advice and reading elsewhere that they would be better suited to the very low frequencies I want to generate... I also have less than a week to build this thing and thought it would be simpler to construct.
My primary target, for my first installation, is 18hz up to 100db. Ideally, though, I would like room to manoeuvre and experiment with lower freqs in future, perhaps another 3-5hz lower. Its most important that I get a good 18hz wave though, I don't want to tune so low it becomes detrimental to the sound at 18hz. Any recommendations for an appropriate tuning?
Weltersys, I'm afraid I'm not sure of the implications of your answers 1) and 2) because I'm ignorant as to how low or high excursion affects sound quality/volume. Excursion is at its lowest at fb (able to move less air?), but then rises rapidly (i.e. suddenly gets too high) when you go below box tuning? What is the ideal excursion from the speaker?
I'm feeling inclined just to tune 4hz below, to 14hz, how does that sound? (pun not intended)
I had been planning on building a sealed cabinet.... just from the impression I've got from advice and reading elsewhere that they would be better suited to the very low frequencies I want to generate... I also have less than a week to build this thing and thought it would be simpler to construct.
My primary target, for my first installation, is 18hz up to 100db. Ideally, though, I would like room to manoeuvre and experiment with lower freqs in future, perhaps another 3-5hz lower. Its most important that I get a good 18hz wave though, I don't want to tune so low it becomes detrimental to the sound at 18hz. Any recommendations for an appropriate tuning?
Weltersys, I'm afraid I'm not sure of the implications of your answers 1) and 2) because I'm ignorant as to how low or high excursion affects sound quality/volume. Excursion is at its lowest at fb (able to move less air?), but then rises rapidly (i.e. suddenly gets too high) when you go below box tuning? What is the ideal excursion from the speaker?
I'm feeling inclined just to tune 4hz below, to 14hz, how does that sound? (pun not intended)
1) Tune the box to 18 Hz, and test that the excursion minima is actually at 18 Hz using a white dot painted on the cone.
2) At Fb, the port puts out most of the SPL, the cabinet is a Helmholtz resonator, just like a jug will hum when you blow across the neck (port).
Ideally, you want excursion to be at or under Xmax, as distortion rises rapidly above Xmax, and additional power does not translate in to more SPL.
3) You will sacrifice LF output at 18Hz by lowering the Fb to 14Hz.
Use an external port so you can change tuning if you want (longer is lower, you can have duct tubes of differing length) and block off the vent if you want to go much lower than 18 Hz.
You want vent velocity to be below around 15 meters per second to keep the port from chuffing, you are looking at some big, long PVC tubes.
Have fun!
100dB at 18Hz is nearly impossible with a single 15" driver (at 1m), you will break your driver trying that! You would need a huge horn or more cone area.
Check this Data-Bass
The best single 15" is this HSU http://www.data-bass.com/data?page=system&id=100&mset=110
Check this Data-Bass
The best single 15" is this HSU http://www.data-bass.com/data?page=system&id=100&mset=110
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IIRC, none of Data Bass tests are done at one frequency, and there are none with an Fb of 18Hz.
Check out the sim in #19, a pair of Lab 12" can do 112 dB at 19 Hz with only about 5 mm excursion in a ported cabinet. Removing one driver would make little difference in level at Fb.
At Fb, the driver will generally burn rather than break- the OP is primarily trying to get the 18 Hz eyeball resonance happening.
With the 15" he purchased, in the correct box size, tuned to 18Hz, the box should easily be able to achieve 100 dB+ at Fb.
FYI:
b
PS: Derate all SPL figures in the Picture hereinabove with 2.2 to at max. 3 dB,
I simulated an 8 Ohm load instead of 4.b
Data-bass measurements are ground-plane. Placing the sub near wall we give extra boost at low range. This Alpine has large Xmax, so perhaps it can do 100dB+ ok.
This my 2x15" closed sub in a smallish room. Drivers were bottoming below 30Hz, but they have only 12mm Xmax. Room pressurization can be seen below 30Hz
This my 2x15" closed sub in a smallish room. Drivers were bottoming below 30Hz, but they have only 12mm Xmax. Room pressurization can be seen below 30Hz
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So I'm at risk of breaking my driver if I deviate from playing just one frequency? I'll bear that in mind!
Bjorno - thank you for all the calculations! My next question was going to be how I go about about transferring the information from such simulations into the actual form of an enclosure but it seems you answered it for me already. I need to start building this thing tomorrow if I'm going to be able to meet my deadline - could you please post/send some more detailed drawings or ones that I might be able to build from easier?
These plans aside, my simulation in winisd says that with a 140l box for 18hz I would need one circular port, diameter 4.7 cm length 8.0 cm (+ 'end correction 0.732' which was there automatically)... I don't know if this sounds right. I was adjusting the size of the box to make it bigger to make the port shorter and more practically sized, i.e. not several metres long.
If I were to follow this rather than bjorno's plans is it just a case of fitting the driver in a box with this volume with an 8cm port/tube going into the box, or are there considerations re positioning etc. I'm not aware of? I've been finding things are rarely as simple as I first imagine. For instance I would prefer the port to be more or a slit/vent type thing along the bottom but it's giving me a vent diameter (4.7x4.7cm) and length of 10.67cm. How I can make this diameter into a workable figure for the size of a vent opening is a mystery.
Also do I definitely need to stuff it? Considering my time limit and lack of money I was wondering if I could do without.
Bjorno - thank you for all the calculations! My next question was going to be how I go about about transferring the information from such simulations into the actual form of an enclosure but it seems you answered it for me already. I need to start building this thing tomorrow if I'm going to be able to meet my deadline - could you please post/send some more detailed drawings or ones that I might be able to build from easier?
These plans aside, my simulation in winisd says that with a 140l box for 18hz I would need one circular port, diameter 4.7 cm length 8.0 cm (+ 'end correction 0.732' which was there automatically)... I don't know if this sounds right. I was adjusting the size of the box to make it bigger to make the port shorter and more practically sized, i.e. not several metres long.
If I were to follow this rather than bjorno's plans is it just a case of fitting the driver in a box with this volume with an 8cm port/tube going into the box, or are there considerations re positioning etc. I'm not aware of? I've been finding things are rarely as simple as I first imagine. For instance I would prefer the port to be more or a slit/vent type thing along the bottom but it's giving me a vent diameter (4.7x4.7cm) and length of 10.67cm. How I can make this diameter into a workable figure for the size of a vent opening is a mystery.
Also do I definitely need to stuff it? Considering my time limit and lack of money I was wondering if I could do without.
Stuffing lowers SPL, don't stuff a ported box used for under 100 Hz.
1) The driver is at risk of breaking when you hit Xlim, which is way more than Xmax. The voice coil will be more likely to burn from sine waves than the surround or spider ripping, but for some speakers Xlim is when the voice coil hits the back plate, that can take out a driver in one hit.
Keep an eye on the excursion, don't exceed Xmax by much.
2) A port that small will be useless at high volume. Consider that the driver can displace a couple liters of air- if the port does not contain more volume than that, the air will be blown out of the port.
You can use that blowing air for party tricks, but it is no good for making eyeballs flop in their sockets.
Design a large enough port to keep the velocity low, since the LF is not accompanied by HF that would mask port noise, even 15 m/s is on the high side.
PVC is much easier to play with than slotted ports, just hang it outside the cabinet.
Once you have finished with your 18Hz venture, you can just plug the port and have a smoother response and more excursion control over a wide band of frequencies.
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