Faital 15XL1400 for bass?

[agedhorse]

The efficiency of the woofer is a direct trade off in order to achieve the performance. There is no free lunch.

 

[Foz]

"The efficiency of the woofer is a direct trade off in order to achieve the performance."

Performance which will never be realized in typical usage absent killing the mid. We have a woof with certain abilities if fed enough volts - cross into the proposed mid at 300 Hz and you have built a system with a woof you can't use to anything close to full capability without putting the mid at dire risk = poor design efficiency as to the woof and a pending death sentence as to the mid. Either build a sub [might be a nice rig adjunct for outdoor gigs] or add mid range components that can keep up when the woof is put to full use.

My $0.02 is the current design is a waste of good parts.

 

[fast slapper]

That's not how it works...I run pretty much this exact rig several times a week with way more power and output than this design will see.

The BMS 15N850 I use is rated at 1200w and has similar xmax to the Faital. The amp I use can put out over 2500w and I clip it at times when having some fun. I'm definitely using all 13mm of xmax and more. The 8" I use is rated at 200w and crossed at 300hz LR24 and it has a dedicated 1200w channel going into it.

The box is eq'd flat from 45hz-18khz with dsp. Slight boost in the low mids on my channel strip.

Hasn't blown up or lost output during use and sounds very clean at high levels. If I change the crossover to 100hz then I definitely notice the limits.

 

[Wasnex]

That's not how it works...I run pretty much this exact rig several times a week with way more power and output than this design will see.

The BMS 15N850 I use is rated at 1200w and has similar xmax to the Faital. The amp I use can put out over 2500w and I clip it at times when having some fun. I'm definitely using all 13mm of xmax and more. The 8" I use is rated at 200w and crossed at 300hz LR24 and it has a dedicated 1200w channel going into it.

The box is eq'd flat from 45hz-18khz with dsp. Slight boost in the low mids on my channel strip.

Hasn't blown up or lost output during use and sounds very clean at high levels. If I change the crossover to 100hz then I definitely notice the limits.

Maybe some of the plots in this thread will help explain whats going on. I.E. most of the power is concentrated below 300hz.
Bass frequency/waterfall plots: what they mean to rigs

Also it's not about how much power a speaker can handle, it's about how much SPL it can produce. If the sensitivity of the bass driver is only 92dB, and the OP has a 900W amp. 900W will produce about 121.5dB max.

The B&C driver has a sensitivity of 96.5dB and is rated for 400W. 400W will produce about 122.5dB.

I believe we are talking about biamping, so gain will be adjusted to account for the difference in driver sensitivity.

 

[ThisBass]

The BMS 15N850 I use is rated at 1200w and has similar xmax to the Faital. The amp I use can put out over 2500w and I clip it at times when having some fun. I'm definitely using all 13mm of xmax and more. The 8" I use is rated at 200w and crossed at 300hz LR24 and it has a dedicated 1200w channel going into it.

Clipping the amp (2500 watts) does not automatically mean you'll definitely use all 13mm Xmax margin (or even more of it).

In real practice you don't play a sine wave sweep of steady power (2500 watts) and even if the amp clips there is need to consider power density (power distribution) at the bandwidth of interest.
Even if your 2500 watt amp clips randomly with generic audio program material you'd likely use not more than about 1/2 of 13mm Xmax margin.

To be more accurate on this topic (amp power vers Xmax) there was need to consider some more variables such as the cab design, furthermore your prefered music genre and EQ setting on either bass guitar or preamp, the usage of effects of a pedal board etc.

 

[kucor]

First of all, not much will be wasted as I got the Faital for free and B&C was last item on a clearance sale and was dirty cheap. So I may waste $50 of MDF and parts but at least will have a fun. I love speakers but with my knowledge I wouldn't buy expensive parts without complete projects (like Greenboy's). Speaker enclosure designing is very delicate but I think I can make a good result in this case. With your help of course

 

[agedhorse]

Because the region above 300Hz for bass guitar typically requires less than 1/4 of the power as below 300Hz, it's not a bad match to the woofer. Especially if you consider 800-1000 watts the real world limits of the woofer for long term reliability.

It's all about power density versus frequency.

 

[Foz]

AH:

You have a well deserved rep. for designing stout/reliable parts = I may be wrong but I can't see you releasing a design with such a weak sauce mid.

I am merely advising the OP to also eschew such half-assery.

To the point, if a 1400w AES continuous rated woof needs to be de-rated +/- 30% to 1000w for "long term reliability" then let's not buy into the idea we should up-rate the 200w AES style rated mid* 25% to 250 unicorn watts to match the proposed 1/4th "power density versus frequency" model above 300 Hz.

* If you want to call the mid rating 400w, you should rate the woof at 2800w. See the spec.s linked below and note the AES style 2 hour power rating of each driver - 200w versus 1400w - and the trivial sensitivity disparity - 96 vs. 96.5 dB.

B&C Speakers
https://faitalpro.com/en/products/LF_Loudspeakers/product_details/index.php?id=201060150

===

OP:

Regardless of what you invested in that woof, it is worth a $1,000 bucks, and kludging a "born to die" mid onto to it would be an inverse sunk cost fallacy mistake IMO [**]. OTOH a pair of these mids would match up pretty well IMO = comfortably within the adopted 1/4th power rating above a 300 Hz xpoint [400w of dual mids versus 1400w of woof / de-rate both as you please]. BONUS: a vertically stacked pair of 8" mids high passed at 300 Hz would make for pretty good horizontal dispersion across the band.

Still and all, I'd just build a very nice sub with that fine assed 15XL1400 and use that mid with a more suitable woof.

YMMV

** How the Sunk Cost Fallacy Makes You Act Stupid

 

[agedhorse]

I look at a lot more than published power ratings when I develop my opinions.

One advantage of extensive testing and engineering analysis is that sometimes what "appears to be" on the surface is not in fact reality within the applications being discussed.

There are dynamic considerations and mechanical versus thermal limits that do not apply equally to both componentss.

 

[Foz]

AH:

Fair enough - but I've made enough mistakes to deserve my own opinion as to what's going to hold up versus what will not in a MI cab... well FWIW I think so anyway, at least in the context of a TB thread seeking opinions and advice.

That said, with deference to your extensive experience and expertise [as well as a laudable willingness to share your insights] I am willing to accept you 3:1 power ratio for a bass cab's woof/mid @ a 300 Hz xpoint as valid and reasonable - but I aint gonna bite on de-rating the woof 30% and up-rating the mid 25%. It's simply a bridge to far for my apparently conservative guesstimate of what will come.

Anywhoo - I guess we're gonna find out eventually.

 

[agedhorse]

It may be too far for you to grasp the concepts now, but if you were to have done enough real lab testing as well as the experience of tens of thousands of speakers out in the wild, you might come to a different appreciation of the science behind my opinion. I don't have the luxury to be wrong as the costs of a wrong "guess" can be VERY costly.

1. The 15" driver mechanically, even with the double spider, my experience is that 1400 watts "RMS" will result in significantly accelerated degradation of the suspension components. If you were to run the math in even a well tuned enclosure, I think you will end up running out of Xmax quicker than you think (at low frequencies). In a commercial environment, good common sense, and a realistic expectation of performance is not as common as you might expect. IF a manufacturer warranties a speaker for say 5 years, it is essential to understand how the speaker is likely to be (ab)used and rate the product accordingly. That would be an expensive driver (or recone) for a manufacturer to eat under warranty.

2. The mid driver has no such limitation mechanically when high passed at 300Hz, so it becomes almost purely a thermal limitation. When you model thermal limits, the duty cycle of the waveform applies, whereas in the mechanical model it does not. Assuming a minimum duty cycle of 50% of rated power, the program power rating of the driver may in fact be plenty valid (for this purpose). Now, when using an LR crossover alignment, the power at the crossover point is already down 50% (LR uses the -6dB knee specification because it's for constant power summing), therefore the low frequency power-bandwidth is not as imposing at it first appears. When you then apply the power-bandwidth spectrum of a bass guitar signal, really, only about 1/4 of the total power on average would go to the midrange driver. This is assuming that the sensitivities are reasonably close AT THE CROSSOVER POINT.

The combination of derating the woofer for long term reliability (yes, many manufacturers do exactly this because their extensive data and experiences override arm-chair guessing) and mid driver's thermal model which accounts for duty cycle and lack of mechanical limitations, actually yield a viable model IMO.

IF the cabinet was going to be used with heavy distortion, where the power-bandwidth spectrum of a bass guitar signal is quite different, I might not be as comfortable with the margin on the mid driver, but I certainly wouldn't be comfortable with the thermal model on a tweeter in that case either. I might also have to look more closely at the thermal model of the woofer, but the previous derating is probably adequate.

 

[ThisBass]

The B&C driver has a sensitivity of 96.5dB and is rated for 400W. 400W will produce about 122.5dB.

Meant as supplement.
The numbers are valid for a sinusoidal signal wave form (steady state).
With real world signals such as a bass guitar or (generic) audio program material we have to consider the crest number of the signal to predict the max SPL for 400 watts of amp power.
Most often the SPL in practice is roughly about 10..12dB down vers sinusoidal considerations.

 

[ThisBass]

* If you want to call the mid rating 400w, you should rate the woof at 2800w. See the spec.s linked below and note the AES style 2 hour power rating of each driver - 200w versus 1400w - and the trivial sensitivity disparity - 96 vs. 96.5 dB.

Also meant as supplement
Besides the "AES style 2 hout power rating" its quite ineresting to know that the AES equation for power handling equals to

P=U^2(rms)/Zmin

while most of all other standards use the following equation to predict driver power handling

P=U^2(rms)/Znom

That's interesting cause nominal and minimal impedance can differ quite drastingly dependent on the driver in question.

Its also interesting that both equations do predict a more theoretical power handling cause there is no Urms*Irms measurement neither one way nor the other.

 

[agedhorse]

Correct, part of the reason for derating is related to the "2 hour" must survive part of the power handling test. The 200 hour test results in a lower power handling number.

 

[ThisBass]

AH:

Fair enough - but I've made enough mistakes to deserve my own opinion as to what's going to hold up versus what will not in a MI cab... well FWIW I think so anyway, at least in the context of a TB thread seeking opinions and advice.

That said, with deference to your extensive experience and expertise [as well as a laudable willingness to share your insights] I am willing to accept you 3:1 power ratio for a bass cab's woof/mid @ a 300 Hz xpoint as valid and reasonable - but I aint gonna bite on de-rating the woof 30% and up-rating the mid 25%. It's simply a bridge to far for my apparently conservative guesstimate of what will come.

Anywhoo - I guess we're gonna find out eventually.

a little bit off topic but never the less it may contribute to the topic.
Mechanical power handling wise lots of engineers try to consider (poorly) the Xmax modelling versus input power.
The software shows a nice plot that clearly tells how much the cone does displace [mm] versus a given input power, sinusoidal sweep with steady power.

But the plots do not tell anything about how much of power (or voltage) really was distrubted to a distinct bandwidth in real practice once a bass player plays the bass guitar powered by a distinct amout of watts yet some clipping of the amplifier.

What I try to tell is that its every time neccessary to consider power density for the bandwidth of interest. Once a cab modelling tells that Xmax was exceeded at 80 Hz for 400 watt input power then it does not mean just the same time that in real practice Xmax was (also) exceeded, yet some amplifier clipping.

Same consideration is also valid for max acoustical power plots.
In real world practice an amplifier does rarely (if ever) push all of its power into a "tight" bandwidth, such as is for any sine sweep considerations.

edit,
even pro engineers sometimes try very hard to comprehent this topic.
I don't tell any name cause the person in question does not contribute to the TB form anymore.

 

[Foz]

Welp. Setting aside in depth and relevant perspectives on the OP's choices viewed through various lens... the disparate likelihood of mechanical versus thermal failure in the 2 proposed drivers / woofer power de-rating calculated with an understanding of best practice policies promulgated to avoid potential exposure to expensive warranty repairs / the variance arising from use of nominal versus minimum resistance in the 1000 wacky ways speaker manufacturers define power ratings / the variance of resistance & sensitivity per frequency / etcetera....

I'm calling our 200w mid driver a weak sister when paired with our 1.4kw woof @ 300Hz xpoint.

That pairing is in IMO red-lining the mid even with traditional bass equipment and a player with a no-bark collar installed.

God forbid that in a pinch the damn thing ever gets used by the keyboard player or the bass player has a fever dream, slips the his collar, and starts pounding B3 instead of F1 or his foot slips and he steps on a swollenwoolymoogalfuzzulator.

My $0.02

 

[Wasnex]

Welp. Setting aside in depth and relevant perspectives on the OP's choices viewed through various lens... the disparate likelihood of mechanical versus thermal failure in the 2 proposed drivers / woofer power de-rating calculated with an understanding of best practice policies promulgated to avoid potential exposure to expensive warranty repairs / the variance arising from use of nominal versus minimum resistance in the 1000 wacky ways speaker manufacturers define power ratings / the variance of resistance & sensitivity per frequency / etcetera....

I'm calling our 200w mid driver a weak sister when paired with our 1.4kw woof @ 300Hz xpoint.

That pairing is in IMO red-lining the mid even with traditional bass equipment and a player with a no-bark collar installed.

God forbid that in a pinch the damn thing ever gets used by the keyboard player or the bass player has a fever dream, slips the his collar, and starts pounding B3 instead of F1 or his foot slips and he steps on a swollenwoolymoogalfuzzulator.

My $0.02

I have some big JBL 2350 horns with 2445H compression drivers with 4" diaphragms. The drivers are only rated for 150W continuous/300W program above 1khz. I believe the sensitivity of this pairing is around 111dB 1W/1m, so 150W would produce about 133dB. Using your logic these would not be sufficient to use with the 15XL400 despite the ability of the horns to play almost 10dB louder than the 15XL400. Instead we need to find a 1.4kW compression driver?

I totally get your logic but it's not inline with how engineers design speakers. And if you don't know, @ThisBass and @agedhorse are accomplished engineers.

Due to differences in sensitivity, the 8" driver can play as loud as the 15XL400, also let's not disregard that the human ear is much more sensitive to mid range frequencies than bass. I.E. as far as human perception, the 8" will seem louder. So, as long as the crossover and gain are properly configured, it's unlikely to be a problem if the bass player slips their collar and starts pounding B3 instead of F1. Would it be possible to blow the 8", yes. Would it be possible to blow the 18", yes. If you do stupid stuff things break.

Good luck finding a suitable 8" that will handle 1.4kW, and hope you have a fat wallet .

 

[ThisBass]

God forbid that in a pinch the damn thing ever gets used by the keyboard player or the bass player has a fever dream, slips the his collar, and starts pounding B3 instead of F1 or his foot slips and he steps on a swollenwoolymoogalfuzzulator.

Basically B3 stores way less power (average power RMS) versus F1
Interestingly the loudness level may be perceived quite similar for both notes on the instrument but power wise I'd derate about -6..10 dB for B3.

Conservative consideration.
-6dB equals 1/4 of power

1200 watt / 4 = 300 watts

The power rating for the 8" mid driver equals 200 watts (thermal)

The total signal (bass guitar signal) shall not distort in an audible way so I assume about 9dB crest factor for the signal in real practice.

200 watts RMS thermal power handling of the driver
Signal crest equals ~9dB
Necessary amp power (RMS) to amplify 200 watts RMS with a signal crest of ~9db
~1200 watts (RMS) amp power

edit
we have to consider mechanical power handling, we have to consider thermal power handling, we have to consider power density at distinct bandwidth of interest, we have to consider crest factor of the signal to be amplified, we have to consider provided amp power, we have to consider different sound settings and pedal board effects, we have to consider different power coming along with different notes played on the instrument, we have to consider different music genres, we have to consider that player Jeff does push different amount of power with just the same gear and settings versus Player Jack.
And last but not least we have to consider that Fourier analytics does not tell the whole story cause there is almost always lots of transient noise involved that contributes to sound and feel and power handling demands.

IMO its such a fascinating interaction of very many variables that makes this science unique and, every time very interesting and very fascinating.

 

[agedhorse]

In MY opinion, that 200 watts RMS rated driver is certainly a viable candidate and in fact may be an ideal match for that driver WITH ALL OF THE FACTORS considered.

Fortunately, I am entitled to my opinion, and you are entitled to your opinion.

 

[Foz]

I have some big JBL 2350 horns with 2445H compression drivers with 4" diaphragms. The drivers are only rated for 150W continuous/300W program above 1khz. I believe the sensitivity of this pairing is around 111dB 1W/1m, so 150W would produce about 133dB. Using your logic these would not be sufficient to use with the 15XL400 despite the ability of the horns to play almost 10dB louder than the 15XL400. Instead we need to find a 1.4kW compression driver?

LOL - yeah right. Have I suggested we need a 1.4kw mid?

You should read the spec.s of the woof and mid drivers in question... 111 versus 96 dB sensitivity aint in it.

Good luck finding a suitable 8" that will handle 1.4kW, and hope you have a fat wallet .

I think we have a suitable mid driver... I am merely opining that using just one red-lines the part... so use two.

Other well informed persons disagree - and have provided well reasoned argument for why it'll all work out.

Nonetheless, I cringe when the OP's purported laid back / down low playing style is brought up as a design criteria. I would prefer the thing was designed to be resilient for other styles and signal sources that could very likely get fed to the beast in real world use. Beef up that mid section and that cab'd have a shot at getting passed on to the grand kids in working order.

Or just build a sub with $1000 woof and call it sorted.*

YMMV

*Maybe per AH's advice put a label on the back saying "1,000 WATTS MAXIMUM INPUT"