I am planing to build a 3 way system, with a 15" woofer, i am very much into the old 80's JBL studio monitor sound.
My question is that when i look on different brands of 15" woofers, they are all more or less, recomended to PA, stage monitor or Subwoofers.....but not very often in a good old fasion HIFI speaker.
Is there specific parameters that i should look for in a 15" woofer, that makes it more suitable for HIFI (JBL sound) than others?
My question is that when i look on different brands of 15" woofers, they are all more or less, recomended to PA, stage monitor or Subwoofers.....but not very often in a good old fasion HIFI speaker.
Is there specific parameters that i should look for in a 15" woofer, that makes it more suitable for HIFI (JBL sound) than others?
For hi-fi, a few things matter differently w.r.t. PA applications.
1) you want a woofer with a not-too-high Efficiency Bandwith Product (EBP) = electrical damping = (Fs/Qes).
Because otherwise the woofer won't be able to reproduce really low frequencies.
A good rule of thumb is F3 (-3dB low frequency extension limit) = 0.4*EBP.
So, if you want your woofer to be usable down to 40Hz at least, its EBP must be < 100. If you want 1/3 octave lower (i.e., 32Hz), then it must be < 80.
Because of physics, this limits the efficiency, though. It's all a trade-off... So realistically, for a 15" woofer that can play low in a Hi-Fi setting you can expect 95-96dB/W(m) maximum (which is still A LOT).
2) you want a woofer that can play DETAILED even at low volumes. This means that it should have low inertia. This is harder to quantify, but a few parameters give you good hints.
One of such parameters is the (Fs/Qms) ratio = mechanical damping. In my experience, you want this to be LOW, preferably ~4 or even lower.
Also, PA woofers with ridiculously high power handling (1000's of Watts) are generally built to withstand abuse (thick cones, hard suspensions, etc.), NOT to be able to reproduce the subtleties of acoustic music at low levels. So, you may want to steer clear of those.
Unfortunately, even by setting these two simple criteria above,
i.e., say, (Fs/Qes) = approx. 80 and (Fs/Qms) = approx. 4,
you'll quickly realise that VERY VERY FEW current-production 15" woofers remain.
That's not surprising, because the modern hi-fi market is oriented towards small and (supposedly) "fast" (huge misconception!) 4"-8" mid-woofers, not big-*** 12"-15" woofers.
The Pro/PA market is instead replete with 15" woofers... but those are built to different goals (see above), and are therefore ill suited to domestic hi-fi: typically, you'll find (Fs/Qes) = 110...160 and (Fs/Qms) = 8...16 :-(
From memory, I think there are one or two current-production Beymas that may meet the criteria above. And then of course the $$$ TADs and Fostex's.
M.
1) you want a woofer with a not-too-high Efficiency Bandwith Product (EBP) = electrical damping = (Fs/Qes).
Because otherwise the woofer won't be able to reproduce really low frequencies.
A good rule of thumb is F3 (-3dB low frequency extension limit) = 0.4*EBP.
So, if you want your woofer to be usable down to 40Hz at least, its EBP must be < 100. If you want 1/3 octave lower (i.e., 32Hz), then it must be < 80.
Because of physics, this limits the efficiency, though. It's all a trade-off... So realistically, for a 15" woofer that can play low in a Hi-Fi setting you can expect 95-96dB/W(m) maximum (which is still A LOT).
2) you want a woofer that can play DETAILED even at low volumes. This means that it should have low inertia. This is harder to quantify, but a few parameters give you good hints.
One of such parameters is the (Fs/Qms) ratio = mechanical damping. In my experience, you want this to be LOW, preferably ~4 or even lower.
Also, PA woofers with ridiculously high power handling (1000's of Watts) are generally built to withstand abuse (thick cones, hard suspensions, etc.), NOT to be able to reproduce the subtleties of acoustic music at low levels. So, you may want to steer clear of those.
Unfortunately, even by setting these two simple criteria above,
i.e., say, (Fs/Qes) = approx. 80 and (Fs/Qms) = approx. 4,
you'll quickly realise that VERY VERY FEW current-production 15" woofers remain.
That's not surprising, because the modern hi-fi market is oriented towards small and (supposedly) "fast" (huge misconception!) 4"-8" mid-woofers, not big-*** 12"-15" woofers.
The Pro/PA market is instead replete with 15" woofers... but those are built to different goals (see above), and are therefore ill suited to domestic hi-fi: typically, you'll find (Fs/Qes) = 110...160 and (Fs/Qms) = 8...16 :-(
From memory, I think there are one or two current-production Beymas that may meet the criteria above. And then of course the $$$ TADs and Fostex's.
M.
What exactly do you mean with detail?
Thiele/Small parameters can only predict how loud a woofer will play in a certain box at a certain frequency, when given a certain input voltage. Assuming your target frequency response is set and directivity differences are negligible, the only thing that differs between woofers is the amount of non-linearity. Assuming non-linearity is something we wish to avoid, detail at low volumes must be positively related to linear operation. Non-linearities are not captured in Thiele/Small parameters, as they assume linearity. So you cannot look at Thiele/Small parameters to tell how much detail a woofer has.
Woofers are minimum phase devices, so all phase related stuff (speed etc.) can be calculated from the frequency response. This usually is somewhat fixed as a design constraint, meaning that the phase response is also fixed.
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Before getting into purchasing drivers, one is to be clear about what kind of an approach it is to be employed in regard to filtering the drivers. Passive loudspeakers without any kind of EQ boost would have called for a different set of TSP than an actively filtered one. One can not count on high fidelity bass with a high of an Fs and a low of a Qts. Thin bass= not hifi, an audiophile prime directive. Observe a tell-tale sign of a woofer, its surround. What were those used in JBL of the 80's?
You are exactly right --- the 15 inch hi-fi woofer is largely a thing of the past. Parts Express has 2 models, although they do refer to one of them as a "sub-woofer" driver. Even the current model JBL 2226, is more of a pro driver than a hi-fi driver. If you are seeking REAL TRUE hi-quality deep bass, be prepared for a very large enclosure requirement.
https://www.parts-express.com/pedocs/specs/295-325-dayton-audio-dc380-8-specifications-46152.pdf
https://www.parts-express.com/pedocs/specs/295-470-dayton-audio-dcs380-4-specifications-46178.pdf
So would I be right in thinking by your criteria this is a nice woofer?
15LX60V2
LOW & MID FREQUENCY 15LX60V2 | Beyma
Looks to have a Fs/Qms ration of ~1.98
And a Fs/Qes of ~93
Thanks for your input.
With the Acoustic Elegance SBP15 you can make a closed box system with F3 = 35 Hz in a 150 L cabinet.
Acoustic Elegance SBP15 woofer for Sealed Box Applications
For this driver: fs = 21 Hz, Qts = 0.43, Vas = 359 L, 2.83V SPL = 92 dB, xmax = 14 mm peak.
In 150 L closed box: fc = 35 Hz, Qtc = 0.72.
After bafflestep compensation, you can realize an efficiency of 86 - 87 dB @ 2.83 Vrms, 1m (flat SPL in full space, -3 dB at 35 Hz).
I only did a study for this driver, not built a speaker.
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TRUE.
Not entirely true. The relations (ratios) of some parameters to others can still tell you something about how the woofer is constructed and hence be indicative of the likelihood of some non-linearities occurring and leading to loss of detail.
Let me explain.
There is one fundamental "lumped" parameter that measures a woofer's mechanical resistance at resonance, i.e.: Rms.
Now, Rms is a number, but in a real (as opposed to ideal) speaker unit, the mechanical resistance (Rms) is in fact observed to be non-linear with respect to diaphragm displacement. This may be due to a combination of a number of factors, among which: static friction (‘stiction’), hysteresis of the materials used for the spider and the edge surround, eddy currents in the voice coil carrier, imperfect ventilation of the pole piece, etc.
Assuming that static friction does play a role (whereby an additional amount of force needs to be applied in order to get the Woofer to budge from its rest position), when the applied electrical signal drops to very low levels, this effect would be expected to become more noticeable [*], since the initial departure from the rest position is now a larger % of the total required travel. This effect is, in principle, similar to the crossover distortion in class B amplifiers (which is also more readily perceived at low levels). Also, as a result of stiction, at low volumes the Woofer will move less than theoretically expected per unit of applied electrical force, resulting in acoustic compression and loss of low-level detail.
And experimentally, this effect appears to be more prominent in Woofers than in Mid-ranges or Tweeters, which is probably due to their comparatively larger moving mass which requires more robust suspensions, etc.
AND, the extent to which this undesired phenomenon manifests itself in a Woofer appears to be proportional to the ratio of its mechanical resistance at resonance to its moving mass, i.e., its overall mechanical damping, which is measured as (Rms/Mms) = 2*Pi*(Fs/Qms).
Thus, highly mechanically damped Woofers - i.e., those for which the (Fs/Qms) ratio is high - appear to gradually 'switch themselves off' as the volume is turned down, resulting in a perceived loss of dynamics in the bass and a brighter tonal balance at low volumes.
[*] at the other end of the scale, at large input levels and consequently large excursions, other causes for distortion become predominant, among which principally the non-linearities of the magnetic force factor (BL) and of the suspension compliance (Cms).
I agree. Also drivers with high excursion are often unsuited, that can also be a hint. For hifi there aren't huge excursions needed and are, in fact, contraproductive since that introduces intermodulation distortion (TIM), not very important in a subwoofer but critical in most 3-way speakers and highly critical in a 2-way system.
Yes, this one should be fine.
But then, of course, there may still be other issues with it that can't be easily gleaned by just reading the TSPs...
A lot of these JBL monitors and hifi speakers of that time had a foam surround. While they have a high inner damping (=few to none resonances) and very low production cost, they were not long-time stable. A lot of these just crumble and tear, I don't remember any of the JBL drivers with foam surround which survived, the ones you can get now used are either re-foamed, re-coned or in really pitiful condition. There are drivers with relatively long-living foam surrounds but I would definitely not make my choice upon that because there were (and still are) loads of really cheap and bad drivers with foam surrounds aswell.
Dude, that's just a rule of thumb. It depends strongly on what you are planning.
The JBL 2226H is known as a very good choice for very good sounding speakers. If you don't need/want a speaker that goes very deep, it is indeed a very good choice, you can expect ~50Hz f3 vented. If you want to go low and want/need it to be standing close to the wall, it is often still an excellent choice (tip: 75l tuned to 40-35Hz, goes down to 30 Hz with roomgain).
Of significantly higher quality than the units that I posted earlier. Of course an increased price tag comes along with them !
Please allow me to share what I have learned, when it comes to bass sound quality. For DEEP bass, it's best to use a true hi-fi style woofer (the ones that are becoming rare) but for MID-Bass, a pro style, hi-efficiency unit yields the very best results.
Of course, for a world-class system, a combination of both, is what you would want.
Really great answers everybody, thank you very much.
Here comes a little stupid question....why are there this big price difference in ea 15" drivers, yes i know you will say "quality" but a speaker are a pretty simple thing, a membrane, a magnet, a voice coil, and the structure...right?
A magne ti a magnet...right, the voice coil is a not rocket science.......just trying to understand what it is that seperate the low cost 15" driver from the very high cost 15" driver?
Here comes a little stupid question....why are there this big price difference in ea 15" drivers, yes i know you will say "quality" but a speaker are a pretty simple thing, a membrane, a magnet, a voice coil, and the structure...right?
A magne ti a magnet...right, the voice coil is a not rocket science.......just trying to understand what it is that seperate the low cost 15" driver from the very high cost 15" driver?
OK, from a designer stand point, driven by over 50 years at it: The general woofer question is a good one, but alone it doesn’t really get you anywhere.
Speaker design is a “system” effort. Solving a set of problems as best one can, given one’s real-world limitations.
Before you go chasing a woofer, you need to have a firm grasp on what you want it, more importantly, NEED it to do. Answer a few basic questions relative to system performance goal(s), setting boundaries. Once you have a solid idea of what your system needs to do, things get a lot easier. And, the likelihood of a successful outcome increases exponentially!
How much can one really spend?
How big an enclosure can I live with?
Low frequency cut off?
How big a room?
How loud do you need to play in your room?
Passive or active crossover.
Your personal abilities.
Do you really need a 15”? Would a 12” or 18” be better suited for your circumstances, performance goals?
And other potential issues. If you want a good ending, you must do your homework.
It is all too common for well-intended DIY speaker builders to throw money at speaker projects and yet so many end up being very unhappy with the results. The learning part is always good, but it’s even better to end up with something that works well and meets expectations.
Being overly simplistic, it’s like you have decided you need 20” wheels on your next vehicle. But what kind of vehicle? How are you going to use it… so on? I don’t wish to appear to be condescending. Just want to send you off in a positive, coordinated direction.
And contrary to what I have read so far in this post, there are many good choices for 15” hi-fi application woofers. You just need to know what you are doing before you can make an intelligent decision on which one suits your need(s) – goals the best. I would even say, hi fi woofer choices have never been better. Especially when it comes to performance for the money spent.
Speaker design is a “system” effort. Solving a set of problems as best one can, given one’s real-world limitations.
Before you go chasing a woofer, you need to have a firm grasp on what you want it, more importantly, NEED it to do. Answer a few basic questions relative to system performance goal(s), setting boundaries. Once you have a solid idea of what your system needs to do, things get a lot easier. And, the likelihood of a successful outcome increases exponentially!
How much can one really spend?
How big an enclosure can I live with?
Low frequency cut off?
How big a room?
How loud do you need to play in your room?
Passive or active crossover.
Your personal abilities.
Do you really need a 15”? Would a 12” or 18” be better suited for your circumstances, performance goals?
And other potential issues. If you want a good ending, you must do your homework.
It is all too common for well-intended DIY speaker builders to throw money at speaker projects and yet so many end up being very unhappy with the results. The learning part is always good, but it’s even better to end up with something that works well and meets expectations.
Being overly simplistic, it’s like you have decided you need 20” wheels on your next vehicle. But what kind of vehicle? How are you going to use it… so on? I don’t wish to appear to be condescending. Just want to send you off in a positive, coordinated direction.
And contrary to what I have read so far in this post, there are many good choices for 15” hi-fi application woofers. You just need to know what you are doing before you can make an intelligent decision on which one suits your need(s) – goals the best. I would even say, hi fi woofer choices have never been better. Especially when it comes to performance for the money spent.
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