Loudspeaker Myths: Crossovers, Bracing, Drivers Oh My!
Myth #6: Better Crossover Parts Don’t Matter
Well this is true if in fact the quality of the drivers, cabinetry and actual crossover design implementation are all subpar. In that case, replacing electrolytic caps with poly caps or iron core inductors with air core may make little or no audible difference.
Polypropylene Capacitors (left pic) ; Electrolytic Capacitor (right pic)
Electrolytic capacitors can have their place in crossovers if they aren’t in series with a high frequency driver, namely the tweeter. The problem with electrolytic capacitors is they exhibit very non-linear resistance behavior at high frequencies. This is why poly or Mylar capacitors are the preferred choice.
Air Core Inductor (left pic) ; Iron Core Inductor (right pic)
Laminated core inductors are convenient to use at bass frequencies where the capacitance value has to be large, often making it impractical to use air core. As long as the laminated core power handling is at least 2X higher than the rated power of the speaker system, the end results will likely be fine. However, air cores are preferred for mid/high frequency components because they are more linear and don’t experience saturation issues that laminate cores do which adds distortion. In addition, air cores don’t exhibit deleterious distortion caused by hysteresis which is common in iron cores and another reason why air cores are always the preferred choice and always more expensive.
Again none of this matters with a poorly-executed crossover design. We’ve seen far too many speakers that skimped too much on the actual crossover design allowing the drivers to operate out of their intended bandwidth or not properly integrating components that just made them sound like mush regardless if they produced good farfield measurements.
For more information on this topic see:
Loudspeaker Crossovers Identifying Myths and Facts about Good Design Practices
Myth #7: The Simpler Crossover is ALWAYS Better
Some companies rely too much on farfield frequency response without looking at the individual nearfield driver response curves. You can, for example, decide to run a midrange in a 3-way design with no crossover components at all to fill in a mid-bass response gap NEVER realizing how much intermodulation distortion that little driver will now be producing when high power low frequency content is running through it. At the same time, if you’re operating that driver out of its designed bandwidth without a crossover component, it will exhibit nasty effects of cone break up as you can see in the measurement below.
Woofer Nearfield Frequency Response of a Two-Way Bookshelf Speaker Operating it's Woofer with NO XOVER
Note that the near field woofer data is raw. (IE effects of port and baffle step are not applied)
The picket fence frequency response above 3kHz is where the cone is actually breaking up causing lots of distortion that will often be missed in a simple farfield frequency response measurement or sine-sweep least mean squares (LMS) distortion test. The driver is actually breaking up causing deleterious distortion artifacts which can often lead to listening fatigue and/or smearing of the sound.
Farfield Response of the Same Speaker (note the out of phase behavior between the drivers above 5kHz)
It’s interesting looking at the breakup node at 7kHz in the woofer response and the subsequent null in summed response. The tweeter must be completely out of phase and have a peak of its own at this frequency!
Ironically this could have all been fixed for just a few dollars by adding a low pass filter (LPF) on the woofer. This begs the question, did the profit margins or over generalized "science" get in the way of producing a truly good sounding and performing product?
In a three-way system with a dedicated woofer, midrange and tweeter, not having the good sense to put at least a capacitor in series with the midrange causes compromises in both efficiency and distortion. Decreased efficiency is caused by dropping the load impedance without increasing output and causing the midrange to over-excurse for a given program which in turn increases distortion.
We've seen numerous loudspeaker companies defend their 2- or 3-element crossover (i.e. resistor/capacitor network only) as being preferred to a more complex crossover network that their competitors employ. They argue that they custom designed their drivers to better integrate with each other, therefore not needing a crossover with steep slopes or an elaborate design to improve overall system impedance. In truth, they make an argument they themselves don’t believe, but insist on this path, since it is the least expensive means to a compromised end. When you see a very simple network, it is usually the result of a budgetary decision, not a performance decision.
Budget Designed Crossover (left pic); a High Quality Crossover (right pic)
Can you guess which crossover was in the speaker that produced the measurements above?
The KISS principle doesn't always work when it comes to building a crossover network for a loudspeaker. Take pause if you open the speaker box and see a 2- or 3-element crossover like the left picture above, recognizing that this was done ,in our opinion, for cost reducing purposes and/or design incompetence. While the speaker can still offer respectable performance nonetheless, its performance is likely not state of the art like you would find in more robust and often more expensive alternatives.
Myth #8: Less Cabinet Bracing is Better Because It Lowers Panel Resonance
This again is nonsense as we’ve demonstrated in the articles below. Lowering panel resonance is a bad idea because it typically places it right within the driver bandwidth that is producing the largest amplitude vibrations. Devices like accelerometers and even high power impedance measurements can give you a good idea of where resonances are that need to be squashed but you can also tell a lot about a cabinet design by simply knocking on the side and top panels all around the cabinet. If it sounds like a high pitch thwack, that’s a good thing. If it sounds like a low frequency thump that doesn’t instantly decay, that means the panels aren’t very rigid which will typically result in boomy or bloated bass response or chesty midrange. Properly bracing a cabinet requires a good understanding of acoustics and budget not just for the panels but for the labor of properly installing them into the cabinet.
Panel resonance manifests as launching of sound waves from an axis that is not the design axis. This effects the polar/power response and is, in our belief, a major deterrent to good imaging. The resonance decay is longer too. Speaker cabinets that resonate do not disappear into a room.
It is worth noting that there can be movement in a portion of a cabinet that is cancelled by opposite polarity movement in another. Numerical simulation using coupled physics between structural mechanics and fluid mechanics and physical testing in a controlled environment are ways to determine if there are actually significant unwanted acoustic emissions. Harman uses a laser vibrometer to scan all surfaces at all frequencies.
For more information on this topic see:
Loudspeaker Cabinets Identifying Myths and Facts about Good Design Practices
Myth #9: We Make our Own Drivers For Superior Performance and Consistency
I believe statements like this are quite insulting to all of the very talented acoustical engineers working for reputable driver companies. The fact of the matter is VERY few loudspeaker manufacturers truly make their own drivers as can be seen in our article below.
Scan Speak 9500 Tweeter (left pic) ; Tweeter from Loudspeaker Manufacturer (right pic)
Which tweeter do you think has better power handling, lower Fs, and better sound?
For more information on this topic see:
Do Loudspeaker Manufacturers Really Make their Own Drivers?
Most companies will NOT reinvent the wheel. They will use standard baskets, ferrites, top plates, etc. They will typically call one of the driver vendors and ask them to customize an OEM part by either changing the voice coil impedance or the cosmetics of the faceplate.
The idea that the major reputable driver companies like SEAS, Scan Speak, Focal, etc. can’t produce a superior product with tight tolerances is not only arrogant presumption, but it’s untrue. They have been doing it longer – for generations! They must compete in the marketplace against the other companies that have also been doing it for generations.
There are certainly cases a designer may choose to customize a specific part to meet their design requirements since nothing off the shelf can meet their needs. Choosing to make your own parts has nothing to do with the fact that driver companies can’t produce reliable and consistently good parts. Most of the best loudspeaker designs in the world use very high quality OEM parts and achieve excellent consistency in design and performance. The reality again is if you can claim “we make our own drivers” it gives the consumer the illusion of exclusivity to help your product stand out.
Myth #10: The Constantly Evolving Speaker
I call this myth the evolving speaker for the simple reason that some companies love to throw a spin on their products every couple of years just to make them new and appealing again. They often make cosmetic changes or slight changes to drivers or the crossovers. While this can result in better performance, be a bit leery if a company goes through revision cycles as often as a parent changes a baby’s diaper. Speaker technology doesn’t evolve nearly as quickly as electronics. A properly designed speaker built a decade ago is still relevant today. No recent earth shattering science has reinvented the wheel or taught us how to build a better mousetrap. However, if a company gets a bad review or sees their sales drop one quarter, or if they want an excuse to raise prices, you may often see the next revision of their speaker hit the shelves as the best thing since apple pie or sliced bread. Again, take these claims with a grain of salt.
The real changes in the past few decades have been in measuring the speaker more than in designing it. Having tools like Klippel and Finite Element Analysis (FEA) to model things on a computer has changed much more so than the product or the quality of it.
Bonus Myth #11 "Digital” Ready Speakers
Watch out for speakers described as “Digital Ready”. This terminology was popular back in the early 80s when the CD player first hit the market and manufacturers were clamoring to get a piece of the digital pie. Nowadays, “Digital” usually tends to be associated with “White Van” speakers built in some Chinese factory or somebody’s garage loaded with cheap drivers and electronics, designed to look impressive with flashy brochures and outrageously high retail prices to confuse the inexperienced buyer.
For more info on these brands, visit Scam Shield.
I think it’s important to realize that virtually every loudspeaker company is going to try to sell you a convincing story as to why their speakers are “better”. There is certainly nothing wrong with having pride in your company’s products and services. It is important to realize that many of the claims that companies make, even in the name of “science,” must be welcomed with cautious skepticism just like a glowing review from an AV magazine online and in print. Discerning the science from science fiction will help you make a more informed purchasing decision. I love a good Sci-Fi show like the next guy, but let's keep the Technobabble out of loudspeakers.Points of Consideration:
- Not all manufacturers' “science” is equal even if they build their company core philosophy off the discoveries founded at the NRC decades ago.
- Manufacturers have limited budgets to buy samples of competing products to directly compare against. Thus small sample sizes can often lead to over-generalized conclusions of product superiority.
- Marketing can often triumph over engineering in a final product design cycle. Manufacturers don’t operate on a fixed profit ratio regardless if they sell direct or through brick & mortar channels so price may not be a good indicator of performance.
- We (consumers and manufacturers) all have our particular biases and preferences on how things should sound.
- We aren’t robots. Sound is NOT always the only determining factor of speaker preference. We must be able to live with the speakers and also have spousal approval. There is value in that!
Don’t discount the small speaker company in favor for the giants out there. Some of the smaller companies offer a greater variety of customization both aesthetically as well as performance options. They often don’t simply slap together a speaker box from a machined piece of medium-density-fiberboard (MDF) but instead hand-build and test each product leaving their facility.
Read the reviews, observe the measurements, listen to the opinions on the forums, but most importantly…. test the products for an extended period of time in your own listening environment to see if a particular speaker is right for your needs.
Remember these great words from Captain Spock "logic is the beginning of wisdom, not the end."
Must Watch Speaker Myths Interview with Gene DellaSala (left) and Hugo Rivera (right)
I would like to personally thank the following people for their contributions and/or peer review of this article, all of whom are true experts in their respective fields. Their contributions enabled us to make the most comprehensive and accurate article possible on the very complex topic of loudspeaker design and testing dealt with herein.
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Recent Forum Posts:
listener training can help immensely like having the potential listener/buyer learn what real instruments sound like in live music situations of all types. i was able to make my own decisions after i acquired these skills and relating the sound of speakers and electronics to those learned real sounds.
i still strive to hone my perceptive and correlative skills. do i believe in speaker break-in? well, yes. i may not subscribe to the multi THOUSAND hour period but perhaps greater than one hundred.
wire? yes, they are different but miniscule in difference compared to speakers or electronics. the better (cleaner, that is lower distortion) the electronics and speakers, the more you can hear. big bucks on wire isn't an option for me and i have never purchased any for more than $100. i do own a couple of $1k interconnects that were won at raffles and those ARE better than most.
that will be enough from me for now.
wlmmn, post: 1052898
Gene, I love these videos that offer a refreshing break from the intellectual dishonesty of marketing brochures. I love hearing marketing BS get a kick in the teeth with cold hard facts! As someone with extensive schooling and field experience as a live sound and recording engineer, I feel like I don't hear or read enough “reality check” time in home-theater-oriented websites. I would've gone on an angry 10-minute rant on the “digital” speaker part. Like you said in another video, you don't hear a lot of this stuff in the pro audio market because it's not tolerated among technical people who have studied signal flow and the physics of sound.
Thank you very much for your compliments and insightful feedback. Unfortunately its a challenge to speak your mind these days without offending people (either manufacturers or fanboys of the products you are referring to). We try to remain brand neutral in these videos but there always seems to be offended parties nonetheless thinking we are specifically talking about them more so than a trend we may be observing. Hugo is pretty new to this industry and he couldn't help notice all the marketing fluff around speaker cables and speakers. So we just let the camera roll and I spoke my thoughts. My apologies to anyone that suffered hurtfeelioma