Crescendo, it looks that the techniques of B&C (think it also counts for the Eminence 3015lf) are somehow different. What drives me bunkers is that in other software I don't get the same end results from these drivers. Somehow they seem to be able to extend the VC's without offering efficiency in the motor/VC relation. I really do question if their Xmax is 'reachable' in a linear behaviour. Did you find any usable distortion charts or excursion charts?
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Maybe I found a possible answer 
...
I think the problem with the B&C 18SW115 is because this driver uses a split-wire system (dual-coil) for their voice coil(s). That means two separate voice coils on the Former. When one coil exits the gap the other coil enters the gap. The advantage is obvious, extreme excursion. The downside is a dip or peak in the BL curve
.
This dip is caused by the space between the two separate coils (lowers the SPL in favour for LF) or if they overlap you will see a peak in the BL curve (higher SPL at cost of LF). I think that both effects cannot been ‘seen’ by HornResp.
In that case it makes excursion figures questionable which is another reason why to use AES power ratings instead of Xmax
... I think the problem with the B&C 18SW115 is because this driver uses a split-wire system (dual-coil) for their voice coil(s). That means two separate voice coils on the Former. When one coil exits the gap the other coil enters the gap. The advantage is obvious, extreme excursion. The downside is a dip or peak in the BL curve
. This dip is caused by the space between the two separate coils (lowers the SPL in favour for LF) or if they overlap you will see a peak in the BL curve (higher SPL at cost of LF). I think that both effects cannot been ‘seen’ by HornResp.
In that case it makes excursion figures questionable which is another reason why to use AES power ratings instead of Xmax
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From their website:
- 3400 W continuous program power capacity
- 116 mm (4.5 in) split winding copper voice coil
- 35 - 1500 Hz response
- 97 dB sensitivity
- 60 mm peak-to-peak excursion before damage
- Neodymium magnet allows a very high force factor and linear excursion
- Double silicone spider with optimized compliance
- Ventilated voice coil gap for reduced power compression
- Aluminium demodulating ring for very low distortion
Well DJK explain this:
If this Split-coil system is based on the US patent for: Push-Pull electromagnetic Transducer with increased Xmax
LINK
The right formula for Xmax would be:
Xmax = [Hvc :2] – [Hmg :2]
For the B&C that would be an Xmax of 10mm.
Now lets rock again:
The Xmax is 14mm and should be reached with 1700W (AES power rating). I'll use the first calculator to calculate the Eg Voltage for 1700 watts at 5.3 Ohms (Re driver). The outcome is Eg = 94.92V.
Lower it to 10mm and we get an Eg of 72V = 978.11W
1700 : 978.11 = Factor 1,7380
Factor 1,7380 stands for 2,4dB
To me 2,4dB at AES power (1700W) looks like a realistic figure for power compression, doesn’t it?
If this Split-coil system is based on the US patent for: Push-Pull electromagnetic Transducer with increased Xmax
LINK
The right formula for Xmax would be:
Xmax = [Hvc :2] – [Hmg :2]
For the B&C that would be an Xmax of 10mm.
Now lets rock again:
The Xmax is 14mm and should be reached with 1700W (AES power rating). I'll use the first calculator to calculate the Eg Voltage for 1700 watts at 5.3 Ohms (Re driver). The outcome is Eg = 94.92V.
Lower it to 10mm and we get an Eg of 72V = 978.11W
1700 : 978.11 = Factor 1,7380
Factor 1,7380 stands for 2,4dB
To me 2,4dB at AES power (1700W) looks like a realistic figure for power compression, doesn’t it?
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B&C SPEAKERS
"Sorry their Thiele-Small parameters states: Magnetic Gap Depth 14mm"
My mistake, I used this data:
B&C 18SW115-4 18" Neo Subwoofer LF Driver 4 ohm
So using the B&C data sheet numbers gives 13.5mm x-max, not 14mm.
AES power is a relatively wide-band (typically 50hz~500hz) pink noise and tells us nothing about x-max in a limited bandwidth application.
"The “Xvar” value reported in our data (generally after the traditional “X-max” value) is measured this way. Beyond this excursion limit, the magnetic field seen by the voice coil, or the total suspension compliance, or both, drops to less than 50% of their small signal value, producing high distortion levels, strong variations from small signal behavior and power compression
"If this Split-coil system is based on the US patent for: Push-Pull electromagnetic Transducer with increased Xmax"
I doubt that the B&C driver is constructed like this, and for several reasons. Patents are one, JBL (and others have similar patents). The real reason is the listed flux density for the B&C driver (1.16T). The double-gap split-coils MUST have lower flux density, because of the higher gap volume (JBL 2268 0.49T, 2269 0.6T, PAsub PA460 0.55T). The magnet structure is also not deep enough either.
"Sorry their Thiele-Small parameters states: Magnetic Gap Depth 14mm"
My mistake, I used this data:
B&C 18SW115-4 18" Neo Subwoofer LF Driver 4 ohm
So using the B&C data sheet numbers gives 13.5mm x-max, not 14mm.
AES power is a relatively wide-band (typically 50hz~500hz) pink noise and tells us nothing about x-max in a limited bandwidth application.
"The “Xvar” value reported in our data (generally after the traditional “X-max” value) is measured this way. Beyond this excursion limit, the magnetic field seen by the voice coil, or the total suspension compliance, or both, drops to less than 50% of their small signal value, producing high distortion levels, strong variations from small signal behavior and power compression
"If this Split-coil system is based on the US patent for: Push-Pull electromagnetic Transducer with increased Xmax"
I doubt that the B&C driver is constructed like this, and for several reasons. Patents are one, JBL (and others have similar patents). The real reason is the listed flux density for the B&C driver (1.16T). The double-gap split-coils MUST have lower flux density, because of the higher gap volume (JBL 2268 0.49T, 2269 0.6T, PAsub PA460 0.55T). The magnet structure is also not deep enough either.
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I'll try to answer or argue your statements in the best possible way but I hope you understand the issue is not about the technique but about the method I'm using for calculating power compression.
Quote: “AES power is a relatively wide-band (typically 50hz~500hz) pink noise and tells us nothing about x-max in a limited bandwidth application.”
True, accept the AES rating also tells you the continue power handling of the coil and this is important factor I'm using. As you know the excursion is almost never the reason why a quality PA driver engineered for LF, gets killed. 99% they will get fried by overpowering or power compression. In case they do get killed by over excursion it's because of the lack of a Low-Cut filter.
There is NO evidence whatsoever that indicates that Tapped Horns with an Fb that is higher than the Fs of the driver, gives higher excursions than basreflex cabs or to more precise 6th order cabs, tuned that way they give the same impedance response.
Now let's use logic:
From real live measurements we know a TH is about 5dB higher in efficiency compared to a basreflex. At max power it still is 5dB higher compared to a basreflex. How would that be possible if excursion was higher in a TH???
If excursion was getting higher during more input power in a TH the 5dB difference should rise also, but it doesn't.
If excursion was higher in a TH, a basreflex should be able to compensate that with extra power...
(don't try that at home folks)
Quote: “I doubt that the B&C driver is constructed like this, and for several reasons. Patents are one, JBL (and others have similar patents).”
The patent on Push-Pull electromagnetic transducers is since the 90ties free of royalties and use, the original on which most 'new' concepts are based dates from the 70ties. In car audio many other brands, besides JBL, that use exactly the same principles and indeed there are plenty similar patents. Actually, the principle comes from a much older industry in the form of dual-coil electro magnets and dual-coil magnetic switches for instance.
15 years ago Monacor released their SPH-450TC (which is fabricated in.... Italy!). This driver was till last year our secret for infra subs for PA purposes. It uses the same technique and principles of dual coil push pull as B&C (what a coincidence, another Italian company). So what makes you think a JBL patent for Car Drivers is needed here?
“The real reason is the listed flux density for the B&C driver (1.16T).”
The flux density is a general number and doesn’t explain/show the differences created by a gap between the coils. Only the differences in a BL curve could be an indication. I said could because there are ways to suppress the dip in BL curve caused by the gap between the coils.
“The double-gap split-coils MUST have lower flux density, because of the higher gap volume”
Absolutely true! The Flux Density is the product of the coil in relation to its surrounding magnetic field. The higher the gap the lower the magnetic field. To overcome this problem you need to use stronger (JBL used more layers of) magnets.
If you look at the B&C driver you can see the relative high magnet cap (compared to other drivers with NEO magnets) that gives an indication of several layers of NEO magnets or long ‘tube’ Neo magnets. Therefore they are able to produce enough magnetic field force to cope with lower Flux density as result of splitting the two (or more) coils.
Secondly, the huge price difference from these drivers (18Sound 18NLW9600 uses similar engineering techniques) also indicates the extensive use of high power NEO magnets. I’m not talking after market prices but prices for quantity orders of >100 pieces.
“The magnet structure is also not deep enough either.”
Maybe you should buy one and compare with traditional NEO magnet driven drivers with similar BL. I think you comparing to much to JBL pictures of their car driver with extreme deep voice coils. The differences here are diameter in Voice coils. B&C’s VC diameter is 116mm and they use of NEO magnets instead of large layered traditional ones.
Btw, the 18Sound 18NLW9600 uses 4 coil system and have a power compression figure of 2,2dB (isn't that another Italian company ).
Quote: “AES power is a relatively wide-band (typically 50hz~500hz) pink noise and tells us nothing about x-max in a limited bandwidth application.”
True, accept the AES rating also tells you the continue power handling of the coil and this is important factor I'm using. As you know the excursion is almost never the reason why a quality PA driver engineered for LF, gets killed. 99% they will get fried by overpowering or power compression. In case they do get killed by over excursion it's because of the lack of a Low-Cut filter.
There is NO evidence whatsoever that indicates that Tapped Horns with an Fb that is higher than the Fs of the driver, gives higher excursions than basreflex cabs or to more precise 6th order cabs, tuned that way they give the same impedance response.
Now let's use logic:
From real live measurements we know a TH is about 5dB higher in efficiency compared to a basreflex. At max power it still is 5dB higher compared to a basreflex. How would that be possible if excursion was higher in a TH???
If excursion was getting higher during more input power in a TH the 5dB difference should rise also, but it doesn't.
If excursion was higher in a TH, a basreflex should be able to compensate that with extra power...
(don't try that at home folks)Quote: “I doubt that the B&C driver is constructed like this, and for several reasons. Patents are one, JBL (and others have similar patents).”
The patent on Push-Pull electromagnetic transducers is since the 90ties free of royalties and use, the original on which most 'new' concepts are based dates from the 70ties. In car audio many other brands, besides JBL, that use exactly the same principles and indeed there are plenty similar patents. Actually, the principle comes from a much older industry in the form of dual-coil electro magnets and dual-coil magnetic switches for instance.
15 years ago Monacor released their SPH-450TC (which is fabricated in.... Italy!). This driver was till last year our secret for infra subs for PA purposes. It uses the same technique and principles of dual coil push pull as B&C (what a coincidence, another Italian company). So what makes you think a JBL patent for Car Drivers is needed here?
“The real reason is the listed flux density for the B&C driver (1.16T).”
The flux density is a general number and doesn’t explain/show the differences created by a gap between the coils. Only the differences in a BL curve could be an indication. I said could because there are ways to suppress the dip in BL curve caused by the gap between the coils.
“The double-gap split-coils MUST have lower flux density, because of the higher gap volume”
Absolutely true! The Flux Density is the product of the coil in relation to its surrounding magnetic field. The higher the gap the lower the magnetic field. To overcome this problem you need to use stronger (JBL used more layers of) magnets.
If you look at the B&C driver you can see the relative high magnet cap (compared to other drivers with NEO magnets) that gives an indication of several layers of NEO magnets or long ‘tube’ Neo magnets. Therefore they are able to produce enough magnetic field force to cope with lower Flux density as result of splitting the two (or more) coils.
Secondly, the huge price difference from these drivers (18Sound 18NLW9600 uses similar engineering techniques) also indicates the extensive use of high power NEO magnets. I’m not talking after market prices but prices for quantity orders of >100 pieces.
“The magnet structure is also not deep enough either.”
Maybe you should buy one and compare with traditional NEO magnet driven drivers with similar BL. I think you comparing to much to JBL pictures of their car driver with extreme deep voice coils. The differences here are diameter in Voice coils. B&C’s VC diameter is 116mm and they use of NEO magnets instead of large layered traditional ones.
Btw, the 18Sound 18NLW9600 uses 4 coil system and have a power compression figure of 2,2dB (isn't that another Italian company
).
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Before I get all kinds of backfire, this might be the possible answer to the problem Crescendo is facing by using my method for calculating power compression for the B&C. Till now I haven't seen any argument that it isn't possible. However, if that is the answer, HornResp doesn't have a problem and it is only a matter of using the right Xmax formula.
But besides Crescendo’s problem and DJK’s testing of the sustainability of my statement about the engineering properties of the B&C the real issue here is:
Does the Power Compression calculating method works?!
I hope that's where other members will jump in. One thing I do know, the outcomes seems to be very close to factory specs and some measurements. Nevertheless, I still consider (this time I don't mean it sarcastic) the possibility that the outcomes could be an example of 'strange' coincidences...
But besides Crescendo’s problem and DJK’s testing of the sustainability of my statement about the engineering properties of the B&C the real issue here is:
Does the Power Compression calculating method works?!
I hope that's where other members will jump in. One thing I do know, the outcomes seems to be very close to factory specs and some measurements. Nevertheless, I still consider (this time I don't mean it sarcastic) the possibility that the outcomes could be an example of 'strange' coincidences...
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When I modeled the 18NLW9600, it wasn't but ~0.6dB louder (at 30Hz) and ~0.2dB louder (at 40Hz) than the B&C driver. And that was at more than twice the power you're planning on giving it. Not worth the extra $200, in my opinion. If I were planing on feeding my drivers 600W, I would probably go with the 18LW2400 or LF18N451. You should have extra power at your amps before 'extra' at the drivers!
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You may have noticed I wasn't mentioning split gap anywhere and I tried to concentrate on Split-coil. I started with "If this split-coil system is based on the US patent…". I also keep other possibilities open like overlapping coils (post 423). I do realise when I introduced the formula [Hvc :2] – [Hmg :2] the second part of the formula is based on dual gap system. Although I have different reasons to doubt there are dual gaps (you should be able to measure different magnets fields from the outside), it could be helpful if you explained your reasoning behind why the B&C can not have a split gap.
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Didnt know about those woofers
Didnt notice those woofers before as the site I frequent www.usspeaker doesnt have the RCF ...
The RCF is very similar to the B&C ... RCF always copies B&C or is the other way around ?
Didnt notice those woofers before as the site I frequent www.usspeaker doesnt have the RCF ...
The RCF is very similar to the B&C ... RCF always copies B&C or is the other way around ?
Thanks fellow Dutchman , for pointing me out. I guess that didn't make sense and seems where confusion started (Dat krijg je van al dat gezwam in het Engels, lol). Although the method seems to work it still doesn't make sence for the Eminence 3015lf for instance.
, for pointing me out. I guess that didn't make sense and seems where confusion started (Dat krijg je van al dat gezwam in het Engels, lol). Although the method seems to work it still doesn't make sence for the Eminence 3015lf for instance. For the other readers, this is where I went wrong, Xmax is given by B&C from 10% THD measurements while my method uses the traditional way of calculating Xmax. Is that what your point was about DJK?
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WRT the 3015LF, I do believe the coil is .75" long and the claimed xmax is rated at 10% distortion.