Jensen 15" all paper woofers of the 1940s and 1950s

[@HiFiTown]

Thank you all for your interest and comments. To those curious about these smaller peaks: Resonance is indeed a component of a speaker’s frequency response, where energy is more efficiently converted to sound. If you’ve always thought of resonances as purely anomalous or undesirable, please take a look at some of the discussion below for more context. This concept has a long history, dating back to the early days of sound reproduction. More recently, it’s evident in designs like the whizzer cone, a British innovation from the 1940s, and Bozak’s famous use of ridges on the surround to accentuate specific resonance points. Even major sealed and ported manufacturers like AR, KLH, and EPI utilized the natural resonances of woofers in their high-production, first-order designs, often without complex crossovers. In this video, I briefly explain how impedance versus frequency charts can indicate and approximate frequency response by highlighting a speaker’s cone and resonance peaks.

[@mycomm-t9j]

It's nice seeing your channel. My father and I subscribed to Audio Mart years ago.I sold your father a new old stock Jensen 10 inch field coil speaker once and got to speak to him a couple of times.

[@HiFiTown]

Very cool! Great to hear from you... buying and testing these speakers over the years.. we learned how all the different designs sounded. Walt, my father wrote some articles on this in some of our last issues of Audiomart -- including a feature on the center woofer the very affordable (for now) P15R..... I hope to post those someday soon on the website to help everyone. So glad you are still in to audio! You can still find nice old Jensen speakers like this. These older speakers still set a high-bar as the physics of sound still applies.

[@mycomm-t9j]

It's good to see that you are still active with audio. I'm sure that you guys had a big influence on the interest people have in high efficiency speakers, tube equipment, and vintage gear today. Getting a chance to talk to your father was like meeting a celibrity back then. Keep up the good work. ​@HiFiTown

[@andrewmcleod9312]

Top video thank you very much. I love looking through old stuff. So much more feel and life than a lot of newer stuff now. And sometimes you find a real banger !! God bless have a great day my man !!

[@borsteldraaier]

Very interesting content and the test track choice is also COOL!!! Thanks

[@JosephCrowesDIYSpeakerBuilding]

Those small bumps are resonances which are not desirable outside of an instrument speaker. Those resonances could also be from nearby objects such as the table surface reflecting the sound back against the cone. Did you do the sweep with the driver suspended in free air?

[@HiFiTown]

Thanks for your comment. This is exactly what I was attempting to educate on, and I appreciate the thoughtful question. I completely understand your point of view as a conventional (post 1970s speaker builder -- such designs entomb speakers in a sealed or tuned, ported cabinet. In fact, in a traditional sense, you are correct-many builders strive to eliminate resonances, viewing them as flaws. A great way to seek one note bass that modern systems are so great at. However, these resonant points can actually be usable response features, not necessarily undesirable or detrimental to sound quality. This is apparent in highly regarded designs using "bass modules" made a little famous by EPI (which to add to the confusion, were sealed boxes). The spikes on the impedance chart typically correspond to resonant frequencies of the driver or the enclosure system. These resonances affect how easily the driver can move and thus impact the efficiency of sound production at those frequencies. For instance, a large impedance peak at a specific frequency-such as the resonant frequency of the woofer-shows that the driver will be particularly efficient there, often resulting in an audible boost in output. The test I conducted was in free air, with the speaker essentially hanging, free from enclosure effects or air pressure restrictions. What you’re observing is the raw electrical motor and cone assembly’s response in an impedance versus frequency layout. This has nothing to do with actual frequency response or cone breakup issues. Instead, these peaks represent points where the speaker is resonating and overproducing certain frequencies, akin to how a whizzer cone creates distinct peaks at specific points. If you were to sweep a speaker with a whizzer cone, you’d see one peak at the large diaphragm’s low free-air resonance and another at the whizzer cone’s resonant point-an excellent way to infer the speaker’s frequency response characteristics. Understanding these resonances is vital for high-efficiency loudspeaker design and tonal balance. These peaks aren’t necessarily problems to be dampened but can be leveraged. In the case of this Jensen speaker, for instance, we recommend using it either full range or with a light crossover slope of around 6 dB. This way, those resonant frequencies enhance the sound and support the mid-range performance at the crossover point. It’s a nuanced art, in the end your ears will have to decide.

[@HiFiTown]

@@JosephCrowesDIYSpeakerBuilding I also wanted to add that the same peaks are visible on multi element speakers with decoupling rings such as the Altec Biflex or even the 755 series - - these spikes are the mechanical/electrical depiction of the speaker's frequency response peaks)

[@JosephCrowesDIYSpeakerBuilding]

A surround resonance (for example) is not a desirable aspect but is considered an anomaly. It creates linear and non-linear distortion. Outside of musical instruments or resonant bass systems (bass reflex) there isn’t a case for it being desirable in a design.

[@HiFiTown]

​@@JosephCrowesDIYSpeakerBuilding Resonances (and associated Linear Distortion) can (and commonly are) deliberately integrated into loudspeaker designs to improve frequency response or efficiency, even outside of those scenarios. (Bozak integrated a lip/ridge on their midrange, exactly right on the surround) Take whizzer cones on full-range speakers, for instance. These are secondary cones specifically designed to resonate at higher frequencies, extending the speaker’s treble response and allowing a single driver to cover a wider frequency range. In this case, resonance is deliberately utilized to enhance efficiency and sound quality, not just as an anomaly. DIY speaker builders often strive for oversimplification because it makes design concepts easier to understand and implement. Simplifying ideas like “resonance is always bad” helps streamline the decision-making process, without using (or trusting) one's ears. Focusing solely on eliminating resonances often results in designs that are highly controlled and compact but can sound sterile and lack efficiency. This approach tends to sacrifice the natural warmth and dynamic qualities that come from thoughtfully integrated Fs (and extensions thereof) characteristics.

[@theaudiofool5475]

​@@HiFiTown what a long story to say, " I hate the modern world and every thing that's older then you is great". 😂🤣

[@T_Burd_75]

It would be interesting to hear Scarlet Fire played on those speakers. ;-)

[@bobsmoot8454]

Early, his mother Lenice and his late father, Walt, absolutely know what sounds awesome, you can take their advice to the bank.

[@DIYhyfy]

Really cool drivers, nice video. So you understand, the peaks you're seeing in the impedance plot are resonances. These are not intended to be there. It's from poor design. They will cause a range of issues.

[@HiFiTown]

That’s the modern boiler-plate knowledge on resonance, sure, but it’s just one approach to speaker design. Resonance has historically been used by mainstream builders, going all the way back to (for acoustic suspension.. but way before for open back stuff) AR for sealed cabinets, and brands like KLH and EPI (see Bass Module, of the 1970s) . It’s a fundamental part of an effieicnt design without dips, and you don’t necessarily need to eliminate it with filter networks (like is done so often) -so long as you understand what the resonances are doing. Modern brute-force methods try to remove them entirely, but that often kills efficiency and detail. It’s a valid perspective, but only for modern, high powered stuff, and high sound pressue levels, in commercial settings. You should always test Impedance vs Freq on the bench first.. to view this -- before building any system "by the book". It may seem like a lack of design, but in this case, but, knowing the speaker’s origins. The frequency response (and seminal resonances ) were very likely intentional: the woofer was run full range in an open baffle (a cabinet without a back), and a tweeter was added with a 4 µF capacitor, creating a simple 6 dB first-order crossover. This setup was commonly used in the 1950s and can sound wonderful-unless you’re expecting unrealistic, booming lows like those from modern ported or sealed boxes. You will see the same resonances (by design) in any full range crossover-less speaker with a sub cone, or whizzer cone attachment. In fact, if you visit a high-end audio show today, you’ll notice these classic methods being used more and more. Even back in the 60s and 70s, many manufacturers were well aware of the benefits, using resonance to enhance efficiency and sound quality. And those resonance points? They actually make the speaker more efficient in those frequency ranges, providing an indirect way to describe frequency response without needing SPL measurements. For more context, check out my replies to the other commenter below.

[@theaudiofool5475]

​@@HiFiTown another long story with a lot of Bullshit😂

[@HiFiTown]

@ So you think Fs, T/S and outfits like Bell Labs don't count as well? Check out some writing on how dynamic speakers, sub cones, and full range drivers work. you might be thinking that there aren't modern manufacturers that embrace these physics?? - - plenty out there. Might not be the speakers you're into - - that's fine- - here's an example of a modern company trying to produce products somewhere to classic I haven't heard them but you can see they certainly harness the same principles. right or wrong... here is one example: kjfaudio.com/product/cube-audio-f10-neo-pair/ Each time you add a feature or shape cone to a speaker you're going to introduce similar peaks at whatever functional resonance points that attachment causes. It's legit speaker design.

[@theaudiofool5475]

@HiFiTown Yep, legit speaker design... 😏 From the twenties en thirties 😂

[@HiFiTown]

@ - Physics don’t change. The principles behind dynamic speakers remain the same, whether from the 1920s, 30s, or today. Marketing may push the idea that newer materials are inherently better, but every material comes with strengths and drawbacks. In loudspeaker design, it’s about harnessing those properties effectively. Modern materials and designs are just different-and intended fi handle cheap power / heat -- not necessarily superior.

[@hkr321hkr]

Was it the invention of the foam that transported the woofer to another level?

[@HiFiTown]

@@hkr321hkr Well that is a good question ... Foam and rubber have uses.. but not really. High-compliance surrounds, like foam or rubber, have been mechanical advancements that improved power handling and allowed for greater cone movement. However, they have not contributed to realism or lifelike sound reproduction. While early speakers in the 1920s used materials like leather or felt for surrounds-mainly for practical reasons rather than to enable significant cone movement-modern loudspeakers evolved alongside shifts in musical trends. As music recordings began to feature deeper bass, special effects, and synthesized sounds, the demand for extended low-frequency response grew. Foam and rubber surrounds allow for significant cone excursion, which is especially useful in acoustic suspension designs. In these designs, the loose compliance of the surround works with the sealed cabinet’s back pressure to produce substantial deep bass, sometimes reaching as low as 20 or 30 Hz. However, this comes at a cost: the large, uncontrolled cone movements can introduce acoustic distortions, compromising tonality and adding spectral contamination that can sound unnatural when compared to live or original music sources. Manufacturers have harnessed these principles to create compact speakers with impressive bass capabilities, but it’s a trade-off. The older paper-cone speakers, often designed with stiffer surrounds, excelled at delivering lifelike sound with minimal power, prioritizing natural tonality. In contrast, foam or rubber surrounds prioritize bass output, sometimes sacrificing musical detail and accuracy. It’s a balancing act between achieving deep bass and preserving the fidelity of the original musical information.

[@HiFiTown]

To those new to audio... questioning the usefulness of such speakers... The audio business has been trying disown the classic paper/ textile speaker for years with no avail.. Since the 1950s, we’ve seen a flood of new materials pitched as the ultimate game-changer in speaker design. It started with Styrofoam and various plastics in the ‘50s and ‘60s, followed by the so-called superior ceramic magnets. The ‘70s and ‘80s brought polypropylene, Mylar, and Kevlar, while the 2000s saw aluminum’s resurgence alongside trendy carbon fiber. Yet every material comes with trade-offs. Take aluminum: rigid and efficient, but it has a harsh ringing quality and a lack of naturalness-a flaw going back to the 1940s and ‘50s when Ted Jordan, working with GEC in Britain, pioneered some of the first aluminum cone speakers. Despite all the hype, nothing (or very little) captures the lightness, speed, and natural tone of paper and textile cones. Sure, new materials will keep coming, and it’s worth staying informed, but don’t always buy into the sales pitch. Sometimes, the classics are classics for a reason

[@Antonio-rv7pn]

''captures the lightness, speed, and natural tone of paper and textile cones'' True,but let's add that this is optimum when the paper/textile membranes are treated at an Art level,I mean impregnated with different resins,cellulose fibers mixed with cotton,silk,or double layered vacuum made sandwich construction(see 755,754a,728b(best,real life-like harmonics from magnet series,electromagnet series are even better!) from Western Electric)to improove velocity,stability,and speed's of sound trough ''this'' paper....oh,see Rehdeko,anyway not for the masses of people. Greetings from Romania!

[@theaudiofool5475]

😂 it's producing information? 🤣 It's producing resonances, huge colloration 😂 Thank God there is progress made in the industry 😅

[@HiFiTown]

Thanks to everyone who viewed and commented so far. In some ways... this was quite different from my usual content. Instead of showing speakers dusted, checked out... I presented them in their raw, rusty, and dirty state. It seems like a lot of people enjoyed seeing the equipment “as-found". So, I have a question for everyone: Do you prefer seeing vintage items “as found”-straight out of storage, with rust and dirt showing? Keep in mind, the rust and dirt rarely affect the sound quality, and this way, you know they’re that unwashed phenomena, haha (the speakers, not Dylan, haha) . This feels very much in line with today’s style, which is somewhat of a shift from how things used to be done. I also think it's cool to build your system that way (lacquer the rust, anyone?) The dust, not so much.. you'll need to achieve WAF in that case) Back in the 1980s and 90s, we’d often feel a bit put off at car shows. The trend back then was either to restore classic cars perfectly to factory specifications, no matter the cost, or to transform them into flawless resto-mods, painted up with pristine none-correct finishes. We always thought it was a bit odd, and part of us wished to see cars as they were-fixed with mods and with rust unapologetically on display. Fast forward 20 years, and that’s now the trend! We have concepts like Icon Derelict, where cars wear their rust proudly, sealed with linseed oil or lacquer. Resto-mods are now about blending the good parts of the old with the necessities of the new. So, what does everyone think? Do you enjoy seeing dusty cones and rusty frames, or would you rather see everything polished up, and perfect as can be? Let me know your thoughts!