Hmm, historically and assuming Altec, JBL were typical; prosound drivers were built stiff with only build quality, Fs being within spec on the high side and got their break in at its first sound check and as long as you used a recommended box they performed as advertised.
IOW, if wanting to truly break them in for HIFI/HT apps it's best done in a factory box at rated power or my preference, the pioneer's equivalent of Vb = Vas/1.44, Fb = 1.56x Fs be they accurate or not and it 'is what it is'. 😉
IOW, if wanting to truly break them in for HIFI/HT apps it's best done in a factory box at rated power or my preference, the pioneer's equivalent of Vb = Vas/1.44, Fb = 1.56x Fs be they accurate or not and it 'is what it is'. 😉
I don't think this is neccessarily true.
BTW I still don't understand what's the magic in the Vas/1.44 formula other than that was the pioneer's preferred box size for some reason.
BTW I still don't understand what's the magic in the Vas/1.44 formula other than that was the pioneer's preferred box size for some reason.
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Well I tried further break in time at various frequencies in 100 ltrs sealed. Fs won't come down past 35 - 36 hz and reverts back to measured specs posted, about 40 hz at 70 deg F room temp. These are going back. I'm not comfortable pushing them harder past 13mm p-p (actual mathematical xmax calculated via coil and gap diference). The suspension is very narrow on these. Spiders aren't any wider than the surrounds, which isn't good for excursion linearity. These aren't one of B&Cs better drivers. The 18TBW100 is superior to this driver. I dont like drivers with stiff marginal spider diameters compared to the VC. I also noticed the silicone spider coating on these is crumbling and shedding, which can get into the VC gap on the inside spider. Not a good design IMO.
As a follow up on this matter, I was told to further "break in" these drivers. Despite continuing to do so pushing the driver up to xmax, they won't budge past where they are after several hrs. I'm not comfortable pushing them past xmax, being this is actually an overload condition for any LF driver and will stress suspension components to the point of deteriorating prematurely, hurting compliance linearity. I highly doubt even after some extended outright abuse exceeding xmax running a 10 hz sine wave, they'll get any closer to meeting advertised factory specs if they don't even dip below 40 hz when sitting for a while in 70 deg F room temp.
I contacted PE to get an RA for these 18s based on the TSP variance. They refuse to pay for return shipping despite always stating adamantly up to 20% deviation of specs are allowed as an "industry standard". Now that I'm beyond that 20 % mark, they still won't accommodate me.
Every other pro driver I've used from any reputable company has met specs within 10% or better and stayed within this range after sitting at 70 deg F room temp. The only exceptions were all drivers made by B&C - 18PZB100, 8NDL51 and now 18NW100 (4 ohm version).
I talked with another OE who had used (past tense) B&C drivers in his designs and also stated TSPs being an issue with them. I myself have used alot of B&C LF drivers over the years3 and run into various issues with them spec wise. That will change if the situation doesn't get resolved. I also buy ALOT of stuff from PE and would at least expect them to back their products along with the promise of conforming to advertised specs within reason, especially if I further spend more money with them ordering replacements for these.
The difference in Fs on my 18NW100s is more than 30% if you consider measuring 41Hz after a fair amount of run-in when it should be closer to 30 hz. I'd be ok if it stayed at leastn 35 Hz, but it won't make it to that point unless I really take a sledgehammer approach to running them in. At that point they'll be abused and prematurely worn before being put into service.
Now that these B&Cs don't come close to falling within the 20 % deviation, I requested a return shipping label. Of course, as expected, they refuse to do so and their main reason for this is the TSPs being beyond 20 % deviation doesn't qualify as a factory defect. I strongly disagree. They just basically say to push these woofers until they drop in Fs and the other TSPs settle themselves in. They sincerely won't drop below the point I already got them to, being they're even outside of 20 % tolerance even after measuring TSPs right after being preconditioned, with the motor being close to 100 def F. Be warned that if you purchase drivers from PE and they're way out of spec, you will be on your own without recourse unless you pay for return shipping.
I've already accepted this big spec deviation on newer 8NDL51s, but I'm running those in the lower midrange where TSPs are less relevant to performance. Its a different situation with dedicated LF drivers.
I contacted PE to get an RA for these 18s based on the TSP variance. They refuse to pay for return shipping despite always stating adamantly up to 20% deviation of specs are allowed as an "industry standard". Now that I'm beyond that 20 % mark, they still won't accommodate me.
Every other pro driver I've used from any reputable company has met specs within 10% or better and stayed within this range after sitting at 70 deg F room temp. The only exceptions were all drivers made by B&C - 18PZB100, 8NDL51 and now 18NW100 (4 ohm version).
I talked with another OE who had used (past tense) B&C drivers in his designs and also stated TSPs being an issue with them. I myself have used alot of B&C LF drivers over the years3 and run into various issues with them spec wise. That will change if the situation doesn't get resolved. I also buy ALOT of stuff from PE and would at least expect them to back their products along with the promise of conforming to advertised specs within reason, especially if I further spend more money with them ordering replacements for these.
The difference in Fs on my 18NW100s is more than 30% if you consider measuring 41Hz after a fair amount of run-in when it should be closer to 30 hz. I'd be ok if it stayed at leastn 35 Hz, but it won't make it to that point unless I really take a sledgehammer approach to running them in. At that point they'll be abused and prematurely worn before being put into service.
Now that these B&Cs don't come close to falling within the 20 % deviation, I requested a return shipping label. Of course, as expected, they refuse to do so and their main reason for this is the TSPs being beyond 20 % deviation doesn't qualify as a factory defect. I strongly disagree. They just basically say to push these woofers until they drop in Fs and the other TSPs settle themselves in. They sincerely won't drop below the point I already got them to, being they're even outside of 20 % tolerance even after measuring TSPs right after being preconditioned, with the motor being close to 100 def F. Be warned that if you purchase drivers from PE and they're way out of spec, you will be on your own without recourse unless you pay for return shipping.
I've already accepted this big spec deviation on newer 8NDL51s, but I'm running those in the lower midrange where TSPs are less relevant to performance. Its a different situation with dedicated LF drivers.
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it must be annoying getting a unit specs. this happens with Scan-Speak from time to time.
Before you send it back, does the different TSP change/affect your box design? in the past i've noticed that my tsp are different, they "balance out" and changes the box model by no more than 1/2dB or 1 or 2 Hz.
If the different TSP affect your box design, then you might have another good reason for exchange for something that is fit for purpose.
Before you send it back, does the different TSP change/affect your box design? in the past i've noticed that my tsp are different, they "balance out" and changes the box model by no more than 1/2dB or 1 or 2 Hz.
If the different TSP affect your box design, then you might have another good reason for exchange for something that is fit for purpose.
They affect the box model considerably. The F3 and F10 points are both higher up thanks to the Qts not responding as proportional to Fb and Ftc.
I've decided to look for the 4 ohm version of the Lavoce SAF184.03 since it meets the criteria for almost identical tuning I had planned with the 18NW100.
I've used similar Lavoce drivers before and they've always measured right on point to published specs for me. They're also cheaper and have more xmax without any noteworthy drop in sensitivity.
I've used similar Lavoce drivers before and they've always measured right on point to published specs for me. They're also cheaper and have more xmax without any noteworthy drop in sensitivity.
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The 4Ω is 30Hz vs. 31Hz, the Vas is 203.5dm3 vs. 252dm3 (stiffer) and Mms is 33 grams more than the 8Ω:
As it says under "Parameters"
"Thiele-Small parameters are measured after a high level 20 Hz sine wave preconditioning test."
I would assume a "high level" would be ~ the "Nominal Power Handling" of 1199W (one watt less than the 8Ω 😉) , around 73.5 volts into the specified minimum impedance of 4.5Ω.
That said, at 20Hz the impedance is ~18Ω, only 300 watts.
As I recall, you have only applied 15volts, a small fraction of the driver's free air power rating.
I would not feel uncomfortable (with hearing protection on..) preconditioning the 18NW100-4 driver with around 73.5 volts at 20Hz.
I did not notice any suspension deterioration after (accidentally) applying 120V to a B&C18SW115-4 several times, though was startled by the output!
At 35Hz Fs, off by less than 15%.
I would bet the Fs would come in closer to 30Hz with proper preconditioning and (at minimum) a 4v test.
Preconditioning a stiff driver designed to withstand 2400 watt peaks in free air for 2 hours according to the AES2-1984 "The rated power of the device shall be that power the device can withstand for 2 h without permanent change in acoustical, mechanical, or electrical characteristics greater than 10%."
is not abuse.
The short look I took didn't turn up the 4Ω SAF184.03 specs, but it's over 16 pounds (44.6%) heavier than the 18NW100, that won't change with a preconditioning test 😉 .
Art
I see your point Art. B&Cs deriving of specs does appear to be under extreme conditions, at least more extreme than I'm used to with a new driver. I dont understand why they are so far off compared to the other companies, some of which are owned or run by B&C themselves.
If this is sincerely the case they spec their drivers this way, it makes it difficult for multi purpose applications where the sub won't be pushed nearly as hard. In this case, a completely different set of specs should be given or at least some form of compensation factor to determine how far off the driver will be at room temp.
There's also another issue I have with this woofer. The silicone impregnated spider is shedding its silicone in the form of little crumbs as I push the driver harder. I've had this stuff get into a driver VC gap before with disastrous consequences. The VC eventually burned in some spots during heavy use and the driver needed to be rebuilt. My 18PZB100s did this despite being advised not to worry about it.
If this is sincerely the case they spec their drivers this way, it makes it difficult for multi purpose applications where the sub won't be pushed nearly as hard. In this case, a completely different set of specs should be given or at least some form of compensation factor to determine how far off the driver will be at room temp.
There's also another issue I have with this woofer. The silicone impregnated spider is shedding its silicone in the form of little crumbs as I push the driver harder. I've had this stuff get into a driver VC gap before with disastrous consequences. The VC eventually burned in some spots during heavy use and the driver needed to be rebuilt. My 18PZB100s did this despite being advised not to worry about it.
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The crumbs do look like the silicon was over applied in places, which would tend to raise Fs until shed.
I'm surprised those crumbs could stay in the gap long enough to cause heat issues.
Do you have photos of the burnt VC?
@weltersys Sorry, I don't have any pics of that. I had to send the drivers back. The silicone accumulated in the top part of the gap and lodged itself in small clumps.
PE actually stepped up and sent me a return shipping notification for the 18NW100s. I'm very pleased they did this, as it shows they care about my business, as I've been a decent customer since the early 1990s.
I don't recommend the 18NW100s for anything but PA use and only if you're not expecting accurate and detailed low end. They're not that type of driver aside from the TSPs being so divergent from typical measurement conditions. I don't recommend narrow spiders on higher excursion drivers, especially if you're expecting higher resolution LF. I have a strict policy of never tuning ported enclosures lower than driver Fs. Distortion goes up under this point just from a logical POV as you're fighting basic physics. I know its common in the PA world to tune drivers with Qts > .42 in ported boxes lower than Fs, but that has never sounded good to my ears.
I don't recommend the 18NW100s for anything but PA use and only if you're not expecting accurate and detailed low end. They're not that type of driver aside from the TSPs being so divergent from typical measurement conditions. I don't recommend narrow spiders on higher excursion drivers, especially if you're expecting higher resolution LF. I have a strict policy of never tuning ported enclosures lower than driver Fs. Distortion goes up under this point just from a logical POV as you're fighting basic physics. I know its common in the PA world to tune drivers with Qts > .42 in ported boxes lower than Fs, but that has never sounded good to my ears.
I have 6 of this the 8ohm version on two double 18s and two single 18s tapped horns capable for earthquake shake bass
Distortion goes up because of increased excursion towards lower frequencies, not because of where the driver's Fs is, at least this is how I experienced. So you don't like sealed boxes either? Basically they can interpretable as vented boxes with 0 Hz Fb. Drivers with Qts > .42 typically not very good for vented boxes anyway in my opinion, those doesn't have enough damping for realworld speakers, even if the simulations don't show this. But some may like how those underdamped speakers sounds.
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@YSDR I do like sealed boxes alot. They have inherently lower distortion at lower frequencies if you're well under xmax and usually better midbass without the port leakage. Ported boxes can have lower distortion numbers when excursion is lower around Fb.
The compliance of a sealed box is more linear than the driver's own suspension, but only if Vb isn't too small.
Acoustic suspension designs are my favorite sealed type of enclosures, but mechanical power handling takes a hit down low, sort of like a ported box when it unloads.
Generally I aim for QB3 ported alignments, where Fs = Fb and Vas = Vb. At a QL of 7 this ends up with drivers that have a Qts of .37 - .41
It takes a very capable driver to play clean in a small sealed box. Most drivers made for this purpose have very low Qts and Vas. Electrical power handling must be high when pushing the whole system down past Fb and the cone has to be as stiff as a board. Flimsy cones are very bad at loud bass in small enclosures.
The compliance of a sealed box is more linear than the driver's own suspension, but only if Vb isn't too small.
Acoustic suspension designs are my favorite sealed type of enclosures, but mechanical power handling takes a hit down low, sort of like a ported box when it unloads.
Generally I aim for QB3 ported alignments, where Fs = Fb and Vas = Vb. At a QL of 7 this ends up with drivers that have a Qts of .37 - .41
It takes a very capable driver to play clean in a small sealed box. Most drivers made for this purpose have very low Qts and Vas. Electrical power handling must be high when pushing the whole system down past Fb and the cone has to be as stiff as a board. Flimsy cones are very bad at loud bass in small enclosures.