Horses for courses.
All I am saying is that I have never heard accurate bass reproduction from a passive speaker, at least not compared to the original sound in the recording studio. Passives always seem to 'smear' (over time) the bass making it softer but longer lasting than it really should.
Thanks to Art and Jim for highlighting the driver size / Sd issue... I have emailed AJ Designer and asked for clarification ie in the Diameter box do I use the "Nominal Diameter" from the driver spec sheet, or... Do I use a lower figure based on the actual cone area of the driver...??? I will let you guys know once I get confirmation from AJ.
Until then, I will assume the worst case ie I will revise the size / Sd using the cone diameter plus half the surround width? Art/Jim, is that a "safe" figure to use?
Thanks
A.
Until then, I will assume the worst case ie I will revise the size / Sd using the cone diameter plus half the surround width? Art/Jim, is that a "safe" figure to use?
Thanks
A.
Using Jim's suggestion for driver diameter a single driver still holds 100 dB SPL at 1 meter, but the cone travel increases to 6 mm at 40 Hz... Thats too close to X Max for me and the cone will be "bouncing around" .... Too many "ghost echoes"!
The good news is that is still well (1.5mm to spare) within X Max and only uses 150 watts of power ie less than 22% of its AES rated power.
So a pair will hold 103 Db SPL at 1 meter at 40 Hz with 6 mm cone travel...It will work, but I would suggest moving up a size to the Beyma https://www.beyma.com/speakers/Fich...rs-data-sheet-low-mid-frequency-12P80NdV2.pdf (or the Fe version if money is tight) which will reduce cone travel back down to around 30% of Xmax... I will do a sim using Jims formula for driver size.
The good news is that is still well (1.5mm to spare) within X Max and only uses 150 watts of power ie less than 22% of its AES rated power.
So a pair will hold 103 Db SPL at 1 meter at 40 Hz with 6 mm cone travel...It will work, but I would suggest moving up a size to the Beyma https://www.beyma.com/speakers/Fich...rs-data-sheet-low-mid-frequency-12P80NdV2.pdf (or the Fe version if money is tight) which will reduce cone travel back down to around 30% of Xmax... I will do a sim using Jims formula for driver size.
Looked at the price of the Neo Vs the Ferrite and the FE is way better value https://www.beyma.com/speakers/Fich...rs-data-sheet-low-mid-frequency-12P80FeV2.pdf so done a Sim for that.
A single driver maintains a continuous 100 dB at 40 Hz with just 80 watts (700 watts AES rated) and X max drops to 4 mm (+/_ 7.5 mm X max and +/- 26 mm before damage...!) so well within all limits.
A pair will hold 103 dB at 40 Hz.
Single driver holding 100dB
A single driver maintains a continuous 100 dB at 40 Hz with just 80 watts (700 watts AES rated) and X max drops to 4 mm (+/_ 7.5 mm X max and +/- 26 mm before damage...!) so well within all limits.
A pair will hold 103 dB at 40 Hz.
Single driver holding 100dB
@Hydrogen Alex --
So you're suggesting putting this 12" Beyma into a sealed 34 liter enclosure and using EQ to boost the bass.
I tried simulating the FR in WinISD. It showed -17 dB @ 40Hz.
That means +15 dB boost at that frequency to meet the required bandwidth. Max power on tap from the Hypex FA253 is 250W. At full power, the max SPL (based on driver's rated 99 dB/w) at 40Hz would be 108 dB/1m. Assuming no driver power compression. Maybe 105 dB if the bass boost has to be higher.
So that could actually work, at least "on paper".
Two downsides for me are price & availability:
Ferrite: USD349 at USSpeaker -- https://usspeaker.com/beyma 12p80Fe-1.htm Translates to well over $1000/pr.
Neodymium: USD500 -- https://usspeaker.com/beyma 12p80Nd-1.htm = CA$1500/pr
I could try hunting for less pricey drivers with similar specs on loudspeakerdatabase.com -- if this approach really works. Any feedback on Alex's posts above?
So you're suggesting putting this 12" Beyma into a sealed 34 liter enclosure and using EQ to boost the bass.
I tried simulating the FR in WinISD. It showed -17 dB @ 40Hz.
That means +15 dB boost at that frequency to meet the required bandwidth. Max power on tap from the Hypex FA253 is 250W. At full power, the max SPL (based on driver's rated 99 dB/w) at 40Hz would be 108 dB/1m. Assuming no driver power compression. Maybe 105 dB if the bass boost has to be higher.
So that could actually work, at least "on paper".
Two downsides for me are price & availability:
Ferrite: USD349 at USSpeaker -- https://usspeaker.com/beyma 12p80Fe-1.htm Translates to well over $1000/pr.
Neodymium: USD500 -- https://usspeaker.com/beyma 12p80Nd-1.htm = CA$1500/pr
I could try hunting for less pricey drivers with similar specs on loudspeakerdatabase.com -- if this approach really works. Any feedback on Alex's posts above?
I just remembered I picked up some nice Eighteen Sound 12" neodymium drivers on a lark a couple years ago. They were cheap & I considered them for use in an Aino Gradient re @Juhazi but didn't go very far with them. https://www.eighteensound.it/en/products/lf-driver/12-0/8/12NW530
Tried WinISD simulation in a 30l sealed box: Down -14 dB@ 40Hz.
500W AES & 96 dB/W. So this driver could work very similar to the 12" Beymas @Hydrogen Alex suggests.
I have them on hand, and it's easy to cut another baffle for my test box. Have to try it. Maybe tomorrow.
Tried WinISD simulation in a 30l sealed box: Down -14 dB@ 40Hz.
500W AES & 96 dB/W. So this driver could work very similar to the 12" Beymas @Hydrogen Alex suggests.
I have them on hand, and it's easy to cut another baffle for my test box. Have to try it. Maybe tomorrow.
The cone diameter plus 1/3 to 1/2 of the surround contributing to Sd is a rough estimate figure.
The mounting flange, surround shape and width vary so much with different drivers that an estimate could be close, or off by a considerable amount based on nominal speaker diameter.
The piston excursion calculator I use for quick sealed box estimates
http://www.baudline.com/erik/bass/xmaxer.html
Uses this basic piston formula:
SPL = 112 + 10 * log(4 * pi^3 * Ro / c * (num * Vd)^2 * f^4)
Vd = (.83 * diam)^2 * pi / 4 * Xmax
The .83 diameter reduction of the nominal driver size in figuring Vd (displacement volume) to estimate Sd (effective piston area) may be close for some drivers, not so close for others.
Small, high displacement drivers may have considerably less Sd than the estimate.
Distortion and transient response issues aside, there is no question that doubling driver displacement in a sealed box increases output by +6dB SPL.
Vd (volume of displacement) is simply Xmax times Sd.
How Xmax is figured makes the volume of displacement (Vd) difficult to compare.
The Dayton RSS265HF8 lists Vd as 495.3 cm3 (14.3mm Xmax * 346.4 cm3 Sd).
Although the PD.103NR1 mid range driver you suggested lists Xmax at 7.5mm, and Sd as 346.4 cm3, it lists Vd as only 180 cm3 (0.18liters).
This means Precision Devices used 4.97mm Xmax to figure Vd.
The difference in low frequency output between the drivers would be more than 6dB, assuming enough power/voltage available to drive them to Xmax.
Art
Hi Mikessi,
That would be great to build up a pair of test cabinets and I would be fascinated to hear your thoughts on how they sound compared other drivers with more conventional loading.
Can I ask if your monitors will be in wall or on wall or placed against a back wall... Or are they desk or console mounted?
The reason I ask is room gain/boundary reinforcement makes quite a difference to any speaker here.
I have added a sim below using 100 watts which at 4.5mm cone travel is well below its Xmax limit of 7.5mm
Yes looking at -14 dB or - 15dB at 40Hz ref Zero dB or max level is alarming, but please remember the following... Its counter-intuitive but works beautifully!
A single driver holds 102 dB so a pair of speakers will hold 105dB at 1 meter (assuming zero room gain) at 40Hz ... Job done, no boost required, these drivers in 35 litres (remember thats a 40 litre cabinet allowing for the volume occupied by the driver and some bracing/damping etc) will hold 105dB at 40Hz with zero DSP boost applied...!
The only EQ' ing will be to reduce the frequencies above this to flatten the response.
This will allow you to get all the benefits of an ultra clean, low distortion bass and low/midrange because of all the reasons I detailed in my long post yesterday (or two days ago?) ie if you looked at the CSD plot of this driver/loading it is only having to dissipate approx 97 watts (the driver is 3% Ref Efficiency) Vs a heavy cone / low Bl driver with around 1% to 1.5% efficiency... Does not sound a lot? A 1.5% driver (half the efficiency will require twice the power ie 200 watts (or 300 watts if 1 % efficient) and it will have to dissipate 197 watts of power... Now the question is can you hear the difference ????????!!!!!!!!
As always, hope that helps.
Cheers
A.
That would be great to build up a pair of test cabinets and I would be fascinated to hear your thoughts on how they sound compared other drivers with more conventional loading.
Can I ask if your monitors will be in wall or on wall or placed against a back wall... Or are they desk or console mounted?
The reason I ask is room gain/boundary reinforcement makes quite a difference to any speaker here.
I have added a sim below using 100 watts which at 4.5mm cone travel is well below its Xmax limit of 7.5mm
Yes looking at -14 dB or - 15dB at 40Hz ref Zero dB or max level is alarming, but please remember the following... Its counter-intuitive but works beautifully!
A single driver holds 102 dB so a pair of speakers will hold 105dB at 1 meter (assuming zero room gain) at 40Hz ... Job done, no boost required, these drivers in 35 litres (remember thats a 40 litre cabinet allowing for the volume occupied by the driver and some bracing/damping etc) will hold 105dB at 40Hz with zero DSP boost applied...!
The only EQ' ing will be to reduce the frequencies above this to flatten the response.
This will allow you to get all the benefits of an ultra clean, low distortion bass and low/midrange because of all the reasons I detailed in my long post yesterday (or two days ago?) ie if you looked at the CSD plot of this driver/loading it is only having to dissipate approx 97 watts (the driver is 3% Ref Efficiency) Vs a heavy cone / low Bl driver with around 1% to 1.5% efficiency... Does not sound a lot? A 1.5% driver (half the efficiency will require twice the power ie 200 watts (or 300 watts if 1 % efficient) and it will have to dissipate 197 watts of power... Now the question is can you hear the difference ????????!!!!!!!!
As always, hope that helps.
Cheers
A.
Attachments
Thanks Art,
I have assumed the worst and run new some new sims (see above) and I hope that if mikeiss is willing to build up some test cabinets he can have a listen to the different driver loading concepts and give us all some opinions... I would really love to hear if someone else hears what I hear!
Nothing wrong with EQing the driver to the desired response, assuming the amp has enough voltage swing to push the driver to the excursion needed for the output.
The Hypex FA253 can do 200watts (~40volts) at 8 ohms, and current limits to 250watts at four ohms, only 31.6 volts.
The 18 Sound 12NW530 sensitivity at 40Hz is around 76dB, at 200 watts (~40volts) may hit around 99dB.
Alex has been quoting a +3dB gain for two drivers in two equally sized boxes. Assuming mutual coupling (drivers within 1/4 wavelength of each other, mono LF signal), and ignoring room effects, the sensitivity increases by +3dB, and power doubled +3dB, for a total of +6dB.
Art
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PS, Re the driver SD formula to calculate the diameter of the actual cone and allow a few mm for the surround movement I took the drivers Sd from the spec sheet and used pi r squared ie for the Beyma 12 Pe80Fe with an Sd of 550, I arrived at a working diameter of 27cm as follows:
13.5 cm radius, so 13.5 squared = 182.25 multiplied by 3.14 = 572 square cm. Which is the 550 square cm plus 4% to allow for the surround movement.
Not sure if this is 100% accurate but its simple and must be very close.
Cheers
A.
13.5 cm radius, so 13.5 squared = 182.25 multiplied by 3.14 = 572 square cm. Which is the 550 square cm plus 4% to allow for the surround movement.
Not sure if this is 100% accurate but its simple and must be very close.
Cheers
A.
Thanks Art,
I was assuming a single 12 inch driver in each cabinet so when you add a second cabinet you gain the 3dB from doubling the Sd.
I also assume the cabinets a couple of meters apart, say on a mixing desk or console?.
Both drivers would remain an 8 Ohm load and driven by separate amps so they would not see a 4 Ohm load.
Is this not a 3dB increase in SPL?
Thanks
A
Assuming the listener/ measurement mic is in the center, equidistant from the speakers, you gain +3dB sensitivity from doubling the drivers and boxes.
Since sensitivity is increased by +3dB, the voltage applied to the pair of 8 ohm drivers could be reduced from 2.83 (one watt@8ohm) to 2 volts (one watt@4ohms) for the same output SPL as a single.
Assuming both drivers are driven with 2.83v, +3dB (2x1w=2w)power +3dB sensitivity gain=+6dB SPL.
Believe me, no PA company would double their powered subwoofer inventory if that only gained +3dB SPL
Hi,
To clarify things a bit more, when radiating area is increased coupling between driver and air becomes better. This results in higher sensitivity(efficiency) as long as driver array size is small compared to wave length. At a certain point, of course, less is gained by adding more and more drivers so no free energy.
Regards
Eighteen Sound Thiele-Small parameters are measured after a high level 20 Hz sine wave preconditioning test.
The Fs may drop after that preconditioning loosens the suspension.
Not to belabor the low frequency cut-off you decide for your monitors, but since the mid 1990s five string basses with a low B (31Hz) keeping up with low synth parts seem almost as common as four string bass low E (41Hz) notes were in the decades preceding.
Hearing (and seeing) the low end of Billie Eilish's recent Grammy performance was an example of how low a lot of pop music goes now.
Post #6 shows how ~<25 Hz is common, with stuff dropping well below that, although mixed at much lower levels than the 50-80Hz "haystack" we commonly hear :
https://www.diyaudio.com/community/...r-mastering-friend-with-focal-solo-be.408946/
Anyway, with the 10" or 12" you are considering, you could EQ flat to 20Hz and decide whether the content down that low is useful for the music.
With the Hypex FA253 you can limit the output to keep excursion under control.
Art
The Fs may drop after that preconditioning loosens the suspension.
Not to belabor the low frequency cut-off you decide for your monitors, but since the mid 1990s five string basses with a low B (31Hz) keeping up with low synth parts seem almost as common as four string bass low E (41Hz) notes were in the decades preceding.
Hearing (and seeing) the low end of Billie Eilish's recent Grammy performance was an example of how low a lot of pop music goes now.
Post #6 shows how ~<25 Hz is common, with stuff dropping well below that, although mixed at much lower levels than the 50-80Hz "haystack" we commonly hear :
https://www.diyaudio.com/community/...r-mastering-friend-with-focal-solo-be.408946/
Anyway, with the 10" or 12" you are considering, you could EQ flat to 20Hz and decide whether the content down that low is useful for the music.
With the Hypex FA253 you can limit the output to keep excursion under control.
Art
Thanks for all that @weltersys
Re the T/S parameters -- this driver is mostly broken in, methinks. I've driven it with various test signals & music for a while, so even if the suspension does loosen up some more, it won't be much.
Re the bass: I'm simply going by what my friends tell me is in the music they record & master. I have no doubt that electronic & digital instruments can make all manner of powerful low bass sounds. The question here is whether my mixing/mastering friends feel they want/need that monitoring capability. 35 Hz, they say is plenty good enough. They get by with less right now.
And as you say, if anything changes, DSP in the Hypex FA253 is there to make changes as necessary.
Re the T/S parameters -- this driver is mostly broken in, methinks. I've driven it with various test signals & music for a while, so even if the suspension does loosen up some more, it won't be much.
Re the bass: I'm simply going by what my friends tell me is in the music they record & master. I have no doubt that electronic & digital instruments can make all manner of powerful low bass sounds. The question here is whether my mixing/mastering friends feel they want/need that monitoring capability. 35 Hz, they say is plenty good enough. They get by with less right now.
And as you say, if anything changes, DSP in the Hypex FA253 is there to make changes as necessary.
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Yes but not in any easily viewable form. BB ply mostly 19mm thick, except 24mm for front baffle. Finish, I don't know yet. I'd like it to resemble this Neumann KH310 (which is for horizontal position w/ mirror image pair) -- but if a 12" woofer goes in, it'll have to be resized.
Basic idea is to smooth & streamline the baffle as much as possible, mount the JA0801 dome from behind into a shallow waveguide like in this Neumann, and maybe do the same with the tweeter -- depending on which one used. The 2 contenders are SB26ADC with resonance absorber (aka KEF peta-puck) and Brandon waveguide vs HiVi RT2C-A Planar Isodynamic Tweeter. Again, I picked up a pair of the RT2C-A recently on speculation because Solen had them on sale at less than half price. https://www.parts-express.com/HiVi-RT2C-A-Planar-Isodynamic-Tweeter-297-406?quantity=1
The latter is somewhat like the NEO series from B&G & GRS but seeming better quality control. It seems to have super wide dispersion way past 10kHz. But good down to maybe 4kHz (in a stretch). Not sure whether to tackle a waveguide for this 13x50mm diaphragm.
In either case, I would consider making the tweeter/mid on a symmetrical baffle that could be rotated so the speaker can be used vertically or horizontally w/o losing the controlled dispersion of the tweeter/mid being up/down. Like the Neumann KH420. A bit more complicated to build but...