Understanding subwoofers

[Oddball]

Or you can have full range mains with cardioid down to 40Hz, monopole to 20Hz, side (of MLP) cardioid subs to 40Hz, dual monopole ULF to 15ish Hz directly behind MLP. Finish it off with center tower with cardioid to 40Hz … sounds real good to my ears

More than one way to skin the proverbial cat (sorry cat lovers)

Right, D&D 15 will get you to 40hz, what else at 105dB with clean response without real sub modules? Also not really sure what is monopole? Is that a sub or a cat, or a dog or a cross breed? And how are you integrating the zoo would be a relevant question. Of course there are multiple ways to skin anything. That is not the issue at all.

 

[SHB]

This makes no sense. Subs in the corner of the room crossed at 200 Hz means you lose localization cues. Subs spread around the room should only be used below 80Hz or so, this way they can't be located. You are also assuming that the sub has clean frequency response to well above 200 Hz which a lot of don't because they weren't designed to run that high.

To integrate even 2 subs much less 4 subs properly you need to have a decent amount of patience and a bunch of DSP available. Now throw in crossing them up in the localization frequency range and you've opened another can of worms.

First off, stereo subs located in the front corners will give you tremendous stereo separation from 200Hz to 20Hz. It would also work for mono with a lower XO point.

Having your subs a little wider than your mains will not be audible. We can hear stereo in low bass, but our sensitivity to stereo is less acute than in the mids and highs.

There are a few things, though, to consider:
• The mains will need to be delayed so that they are properly time aligned
• Corner placement will require some low EQ shelving due to the corner boundary acting like a horn (room gain… it’s like getting a couple hundred extra Watts in amp power)
• It could excite room modes that will need to be tamed
• I’d never buy a sub that can’t reach past 200Hz. I prefer two 12’s to a single 18 inch even though they move the same amount of air.

 

[MKR]

Right, D&D 15 will get you to 40hz, what else at 105dB with clean response without real sub modules? Also not really sure what is monopole? Is that a sub or a cat, or a dog or a cross breed? And how are you integrating the zoo would be a relevant question. Of course there are multiple ways to skin anything. That is not the issue at all.

What else has cardioid to 40Hz? Multiple solutions … Geithains, GGNTKT, Asci with upcoming module, Genelec with W371, Soundfield, maybe others. And the 15C is not full range cardioid by the way. And monopole sub config as opposed to dipole, cardioid, etc. Just mentioned that to differentiate. My mains have specific cardioid driver channel, then cross to sealed monopole below 40. Integration very easy with cardioid. Turn them on, play tunes, enjoy. Of course the mains and side subs are active DSP, that helps. Using HTP1 with no bass mgmt outside of crossing ULF at 40Hz.

 

[EJ3]

A question of definition. Two subwoofers in stereo + crossover 200 Hz. Should this be considered subwoofers or bass boxes?

If you place two two-way speakers on the two stereo subwoofers/bass boxes, in my eyes it becomes more or less two three-way speakers.


For my part, I'd rather have a good midbass punch with a fairly high SPL capability with relatively low distortion than dig down to 20 Hz. Or 30 Hz..maybe even, almost 40 Hz I can compromise in that case.
Both would be preferable but it costs a fair amount of money to get.

My pair of subs raw speakers top out at 80Hz, Crossing over at 200Hz is NOT an option.

 

[SHB]

Sub integration? Really?

It’s only hard if you don’t know how to do it.

The minimum XO slope for your setup should be at least 24dB/oct. and, ideally, higher. I like using Linkwitz/Riley filters. When I use outboard XOs, I prefer steeper than that for the sub.

You XO point should be set one octave above the -3dB spec for your mains. This reduces distortion and increases system dynamic range. Loudspeaker designers do the exact same thing when selecting the XO point from a tweeter to a mid.

Again, the sub isn’t just being used to add low bass. You’re expanding the capabilities of your speaker and improving its performance.

 

[levimax]

To me it seems there are a lot of inconsistencies around subs and subs integration that aren't talked about very scientifically even on ASR:

1. Why is that for electronics we want 100+ dB SINAD and we want 50+ SINAD for speakers above 100 Hz but somehow it is "OK" to have distortion of 13% (which is more or less that CEA-2010 standard) or even much higher like 30% (common for many famous brand subs) below 100 Hz i.e. SINAD of <10? I think distortion is more audible down low due to Fletcher-Munson i.e. between 20 Hz and 40 Hz we are 20 dB more sensitive so for many subs when they try to play 20 Hz they actually produce more audible distortion products at 40 Hz than at the 20 Hz fundamental. I almost never see distortion mentioned when discussing subs.

2. The "can't localize below 80 Hz" science has been replaced with more modern studies and the frequency is more like 40 Hz or even lower depending on the room. Despite this the old "80 Hz" number is used to recommend remote sub placement even though in many cases the remote subs are easy to locate and can be quite distracting. Outside of a few threads I seldom see this new research mentioned.

3. When you abandon full range speakers / co-located subs (maximum distance of acoustic centers of 1/4 wave length at crossover frequency) you abandon a "point source" transducer and all the advantages that come with it (much larger sweet spot, ability to use steep linear phase crossovers, much easier and better time domain performance, ability to have stereo bass, much easier to integrate). No one talks about these disadvantages and only mentions the possibility of smoother FR which is no doubt a good thing but it does not come without costs.

4. Group delay is mentioned quite often but the context is confusing and is usually considered "inaudible" at ~1.5 cycles. While 1.5 cycles may be OK for higher frequencies it is not clear that is the case at lower frequencies where at 20 Hz 1.5 cycles gives you 75 ms which is a lot. If nothing else it can make integrating subs with speakers and other subs that don't have the same GD curve very problematic. There is some credible science that a system with low group delay can reproduce "impact" better which certainly make intuitive sense.

The marketing done by the sub manufacturers and automatic integration system sellers makes it seem like clean LF reproduction to 20 Hz and sub integration (In essence becoming a speaker designer without good data or measurements) is easy but the reality is not so clear cut.

 

[levimax]

• I’d never buy a sub that can’t reach past 200Hz. I prefer two 12’s to a single 18 inch even though they move the same amount of air.

An 18" Pro Woofer Driver can play much lower and much higher than a 12" Subwoofer driver with lower distortion and higher SPL, there is more to it than theoretical air movement based on the area of the driver.

 

[SHB]

My pair of subs raw speakers top out at 80Hz, Crossing over at 200Hz is NOT an option.

Not to bust your chops, but go to Parts-Express.com and check out the comparably sized subwoofer drivers. All of the ones I’ve considered for designs (10”, 12”, 15”) are “flat” to about 800Hz or more.

I’ve seen that some of them, when tested, exhibit higher distortion above 150Hz.

Personally, I’d never consider a sub with less than flat 20-200Hz response. I’m running KEF LS50s and they have to be XO’d at 170Hz minimum.

 

[levimax]

Sub integration? Really?

It’s only hard if you don’t know how to do it.

The minimum XO slope for your setup should be at least 24dB/oct. and, ideally, higher. I like using Linkwitz/Riley filters. When I use outboard XOs, I prefer steeper than that for the sub.

You XO point should be set one octave above the -3dB spec for your mains. This reduces distortion and increases system dynamic range. Loudspeaker designers do the exact same thing when selecting the XO point from a tweeter to a mid.

Again, the sub isn’t just being used to add low bass. You’re expanding the capabilities of your speaker and improving its performance.

I agree with some of this but not the part about being easy. Trying to rely on speaker marketing specs to pick your crossover point is suboptimal. You really need to take measurements to see how both drivers are behaving at the intended crossover point. Many main speakers are not behaving linearly in either the frequency domain or the time domain at the bottom of their range and some subs are the same at the upper end of their range. The problem is these measurements are difficult to take and interpret in room at LF. To me this is the biggest advantage of tight ( 1/4 wave length or less) colocation as it makes things much easier and more reliable.

 

[sigbergaudio]

To me it seems there are a lot of inconsistencies around subs and subs integration that aren't talked about very scientifically even on ASR:

1. Why is that for electronics we want 100+ dB SINAD and we want 50+ SINAD for speakers above 100 Hz but somehow it is "OK" to have distortion of 13% (which is more or less that CEA-2010 standard) or even much higher like 30% (common for many famous brand subs) below 100 Hz i.e. SINAD of <10? I think distortion is more audible down low due to Fletcher-Munson i.e. between 20 Hz and 40 Hz we are 20 dB more sensitive so for many subs when they try to play 20 Hz they actually produce more audible distortion products at 40 Hz than at the 20 Hz fundamental. I almost never see distortion mentioned when discussing subs.

2. The "can't localize below 80 Hz" science has been replaced with more modern studies and the frequency is more like 40 Hz or even lower depending on the room. Despite this the old "80 Hz" number is used to recommend remote sub placement even though in many cases the remote subs are easy to locate and can be quite distracting. Outside of a few threads I seldom see this new research mentioned.

3. When you abandon full range speakers / co-located subs (maximum distance of acoustic centers of 1/4 wave length at crossover frequency) you abandon a "point source" transducer and all the advantages that come with it (much larger sweet spot, ability to use steep linear phase crossovers, much easier and better time domain performance, ability to have stereo bass, much easier to integrate). No one talks about these disadvantages and only mentions the possibility of smoother FR which is no doubt a good thing but it does not come without costs.

4. Group delay is mentioned quite often but the context is confusing and is usually considered "inaudible" at ~1.5 cycles. While 1.5 cycles may be OK for higher frequencies it is not clear that is the case at lower frequencies where at 20 Hz 1.5 cycles gives you 75 ms which is a lot. If nothing else it can make integrating subs with speakers and other subs that don't have the same GD curve very problematic. There is some credible science that a system with low group delay can reproduce "impact" better which certainly make intuitive sense.

The marketing done by the sub manufacturers and automatic integration system sellers makes it seem like clean LF reproduction to 20 Hz and sub integration (In essence becoming a speaker designer without good data or measurements) is easy but the reality is not so clear cut.

1. Agreed.
2. Disagreed, it's more like the other way around, good subs with low distortion and no resonances/rattly cabinets can be crossed at 100-120hz without being localised. Note that this is different than the discussion on benefits of stereo subs.
3. I think 1/4 wavelengths is a bit strict.
4. I don't think we have enough research here, but agree that it should be below 1 cycle if possible.

 

[DanielT]

My pair of subs raw speakers top out at 80Hz, Crossing over at 200Hz is NOT an option.

200Hz. Could be an option if you get a good integration. In practice a DIY three-way speaker (if you have two-way top speakers), with everything that means and is required to make a good speaker.

There are those here at ASR who have gone a step further and created four-way and - if I remember correctly- five-way speakers. Nowadays with digital filters and various speaker calculation programs, even happy amateurs can take on such projects.
Think a few years ago. Four or five-way speakers with only passive crossover components....brr how expensive and cumbersome (especially if you do different test iterations). Even worse if you also use higher-order filters.

 

[SHB]

An 18" Pro Woofer Driver can play much lower and much higher than a 12" Subwoofer driver with lower distortion and higher SPL, there is more to it than theoretical air movement based on the area of the driver.

Please show me any 18” pro woofer driver that has a resonant frequency (Fs) and output substantially lower than 40Hz.

Yes, their sensitivity is high, but they don’t reach low.

I have a Line 6 StageSource single stack PA rig for my bass amp. It has a dual 12” sub cabinet (L3s) that just makes it down to 38Hz. All of the 18” pro woofers I’ve seen are comparable.

Pro drivers are optimized for output level, not low frequency extension.

On the other hand, my Rythmik L12 subs are -3dB at 18 to 200Hz.

They’re apples and oranges.

 

[Oddball]

If you don't know how to do it as apparently @MKR does, I suggest you get going on the thread below. If you have the budget for gear it's pretty much autopilot solution, although for OCAs (not a member with the same name though) with fetish for stereo bass or envelopment - yet that can also be done.

The fact that the thread has 200 pages on ASR is also indicative of how much interest it got. Not easy to follow, but has a treasure of knowledge and individual cases with graphs that are most revealing.

Active Room Treatment (ART) by Dirac

Your spread is tight so I would not worry. Whatever settings you have they are working great. It is normal that spreads are wider at the each end of ART range. Even if you could have tighter spread, theoretically, I don't think you would be able to differentiate between this and tighter case...

www.audiosciencereview.com

The same can be (rarely) achieved through other means, but to the best of my experience not at the same cost and especially the cost of time involved with tweaking.

 

[thewas]

Important for subwoofers is the product of their linear displacement times their radiating surface, in times of digital equalisation and economical class D amplification things like Fs have become secondary.

 

[janbth]

1. Why is that for electronics we want 100+ dB SINAD and we want 50+ SINAD for speakers above 100 Hz but somehow it is "OK" to have distortion of 13% (which is more or less that CEA-2010 standard) or even much higher like 30% (common for many famous brand subs) below 100 Hz i.e. SINAD of <10? I think distortion is more audible down low due to Fletcher-Munson i.e. between 20 Hz and 40 Hz we are 20 dB more sensitive so for many subs when they try to play 20 Hz they actually produce more audible distortion products at 40 Hz than at the 20 Hz fundamental. I almost never see distortion mentioned when discussing subs.

It’s the other way around: We are 20 db less sensitive. The Fletcher-Munson (equal loudness) curves mean we have to turn up the volume in the bass in order to achieve the same perceived loudness.

 

[DanielT]

3. When you abandon full range speakers / co-located subs (maximum distance of acoustic centers of 1/4 wave length at crossover frequency) you abandon a "point source" transducer and all the advantages that come with it (much larger sweet spot, ability to use steep linear phase crossovers, much easier and better time domain performance, ability to have stereo bass, much easier to integrate). No one talks about these disadvantages and only mentions the possibility of smoother FR which is no doubt a good thing but it does not come without costs.

..(maximum distance of acoustic centers of 1/4 wave length at crossover frequency)..

How do you solve it in practice with, for example, a two-way speaker that has a crossover point at, say 2.5 kHz. It's hardly even physically possible to place the woofers and tweeters so close to each other then.

In a three-way speaker crossover around 300 Hz, 1/4 wave length, c-c distance around 30 cm. It might work.

 

[john61ct]

This thread is EXACTLY relevant to where my thinking is at.

I want maximum flexibility to VERIFY myself where my preferences land with respect to the several tradeoffs.

My limit is about 1 cuft per enclosure and I need to set the first crossover ~200Hz to get the best out of the main bookshelf pair.

Those are not trueSubs, but MBM couplers and yes co-located "basstands". I hope to get down to 80 maybe 60Hz at decent SPL.

At the very bottom trueSub, given the size limitation I do not expect high bandwidth, if I can touch 20Hz with a "wise boost" maybe up past 35Hz. I expect Mono is fine that low, but if needed may still do more than one, if not for SPL then tackling room modes with free placements? Two would at least let me test for stereo even without any localization.

Now in between - guesstimating 35-60 maybe up to 80Hz - I definitely want to test Stereo co-location, try for envelopment possibilities with conducive source content, maybe synthetic multichannel attempts.

If not, then move on to testing "smoothing" for a wider set of LPs rather than just for me in the sweet spot.

Ideally I could switch profiles easily, "A" critical music maximum "point source behavior" - dynamic range, stellar soundstage, crisp transients clarity, bass very tight, maybe some envelopment

vs "B" films - couch + wider bass smoothness for big boom effects + center voices clarity

vs "C" dance party mode.

I look forward to spending hundreds if not thousands of hours on the required learning curve REW, various DSP tools...

And doing all this on unrealistically low budgets, measured in a couple/few hundred a month with occasional abuse of the CCs.

 

[SHB]

I agree with some of this but not the part about being easy.

Hey, man, I’m just saying that if you do the research and buy the right equipment, it’s not a big deal… at least, not for me.

I didn’t say that it’s effortless and could be done with any system.

“…But, I can’t do it with my equipment!“

Sorry, but that doesn’t invalidate anything I’ve stated. It does mean that your rig needs upgrading.

One other thing: lacking a thorough bench test, a great rule of thumb is to crossover one octave above the main speakers’ -3dB spec. Depending on the speaker, even higher than that may work best.

One thing is the same for all loudspeakers: as I previously stated, the lowest octave they render is the area where they are least linear and produce the most distortion.

Using subwooferS (emphasis on the plural), moves those abnormalities below the range of most music and improves your system’s dynamic headroom by at least 6dB.

But, hey, do it wrong or pick equipment not up to the task task and it won’t.

I don’t think any of this is debatable.

 

[Oddball]

To me it seems there are a lot of inconsistencies around subs and subs integration that aren't talked about very scientifically even on ASR:

1. Why is that for electronics we want 100+ dB SINAD and we want 50+ SINAD for speakers above 100 Hz but somehow it is "OK" to have distortion of 13% (which is more or less that CEA-2010 standard) or even much higher like 30% (common for many famous brand subs) below 100 Hz i.e. SINAD of <10? I think distortion is more audible down low due to Fletcher-Munson i.e. between 20 Hz and 40 Hz we are 20 dB more sensitive so for many subs when they try to play 20 Hz they actually produce more audible distortion products at 40 Hz than at the 20 Hz fundamental. I almost never see distortion mentioned when discussing subs.

It's easy. If you have a distortion problem and can actually hear it then just stack up more subs. But even a single sub with reach to 20hz will do better than any passive tower that aspires to reach to 20hz. Or 30hz for that matter.

2. The "can't localize below 80 Hz" science has been replaced with more modern studies and the frequency is more like 40 Hz or even lower depending on the room. Despite this the old "80 Hz" number is used to recommend remote sub placement even though in many cases the remote subs are easy to locate and can be quite distracting. Outside of a few threads I seldom see this new research mentioned.

I really doubt that on my practical experience. If you are referring to "envelopment" that is really long shot.

3. When you abandon full range speakers / co-located subs (maximum distance of acoustic centers of 1/4 wave length at crossover frequency) you abandon a "point source" transducer and all the advantages that come with it (much larger sweet spot, ability to use steep linear phase crossovers, much easier and better time domain performance, ability to have stereo bass, much easier to integrate). No one talks about these disadvantages and only mentions the possibility of smoother FR which is no doubt a good thing but it does not come without costs.

This is just limitation of how you perceive bass management. It is actually solved problem, but you are probably not aware of it. It's always good to read the news when you are invested in the topic.

4. Group delay is mentioned quite often but the context is confusing and is usually considered "inaudible" at ~1.5 cycles. While 1.5 cycles may be OK for higher frequencies it is not clear that is the case at lower frequencies where at 20 Hz 1.5 cycles gives you 75 ms which is a lot. If nothing else it can make integrating subs with speakers and other subs that don't have the same GD curve very problematic. There is some credible science that a system with low group delay can reproduce "impact" better which certainly make intuitive sense.

I will not comment on this one as between FQ response, decay and phase, last thing I would need to pay attention to is GD. And unless using some moonshine gear, this will generally be a problem solved.

The marketing done by the sub manufacturers and automatic integration system sellers makes it seem like clean LF reproduction to 20 Hz and sub integration (In essence becoming a speaker designer without good data or measurements) is easy but the reality is not so clear cut.

No sub manufacturers can integrate the subs for you. They can provide some tools but they won't affect rest of the speakers so they are really not the ultimate solution. That appears clear from the circumstances under which they offer their help?

 

[EJ3]

Not to bust your chops, but go to Parts-Express.com and check out the comparably sized subwoofer drivers. All of the ones I’ve considered for designs (10”, 12”, 15”) are “flat” to about 800Hz or more.

I’ve seen that some of them, when tested, exhibit higher distortion above 150Hz.

Personally, I’d never consider a sub with less than flat 20-200Hz response. I’m running KEF LS50s and they have to be XO’d at 170Hz minimum.

First, my mains semi-anechoic (with no EQ of any type) FR is +-2DB 26Hz-20KHz.

Why in the world would I want to go up to 200Hz? That is well into woofer territory (which is definitely not needed from a sub in my system).

Parts-Express has nothing like this:
Perhaps you haven't tried a real sub: a 24" sub in a large transmission line, 60x28x24? (in my case, a pair). Yes, I know, not living room friendly and yes, my wife does not like them. And they will eventually be replaced by something more aesthetic.

Some construction notes of the subs I'm talking about (now out of business [1927-2015]).
(They may soon be back, though (according to them): Renowned for coining the term “High Fidelity,” Hartley—an iconic innovator in loudspeaker design—has returned to production under the stewardship of Tri-Art Audio. In collaboration with former owner Richard Schmetterer, we are committed to preserving and advancing the Hartley legacy. All milling, fabrication, and finishing are undertaken in-house at our manufacturing facility in Kingston, Ontario, Canada.
Hartley Loudspeakers are currently in pre-production as we refine the final details for launch. Comprehensive product information—including specifications, pricing, and shipping options—will be released gradually as we move toward our formal debut in Spring 2026.
We sincerely appreciate your interest and look forward to reaching this exciting milestone, and to sharing the full scope of our next-generation designs in the months ahead.)

THE HARTLEY POLYMER LOUDSPEAKERS​

In the past, very spl people have known about HARTLEY speakers. Audiophiles, engineers, musicians, recording technicians, scientists and other professionals who use sound or consider sound to be a very important part of their lives or careers. No matter what the price, HARTLEY speakers are considered among the best available anywhere in the world. Meticulous hand-crafting and unique problem solving of the physics of loudspeakers are the reasons for our long standing reputation. We don't sell a lot of speakers that way, but we don't have to compromise our standards either. In fact some of our drivers require over fifty hand operations to build.

THE CONE​

Only in recent times do we find companies using cone materials other than paper: polypropylene, Kevlar, aluminum, synthetic polymers and other plastic formulations to name a few. Their more recent revelations was our understanding over FIFTY years ago! Starting with polymerization to paper cones, in 1956 Dr. Harold Luth, chief engineer and Master Chemist developed the World's First Synthetic Loudspeaker Cone. Until that time the only non-paper cones were that of Bakelite paging speakers used by the Navy. To accomplish this truly revolutionary feat Dr. Luth had to invent a new synthetic to which the world had never seen. A series of monomers cross-linked became the solution which led to other problems and solutions. Plato's' loudspeaker cone is one that has: no mass, infinite stiffness, perfect geometry and ultra-fast sound transmission time. Dr. Luth choose a molding process with a special fabric carrier and internally molded ribs. With his physicist hat on (and pipe) he designed a superior geometry never before seen. The cones were shallow, incredibly light and stiff and could withstand high molecular pressure without edge nodding and bending.

THE SURROUND​

Most speaker driver manufacturers use foam, treated cloth or butyl rubber as their compliant surround. Foam, untreated will deteriorate inside-out from humidity and moisture in the air. Treated cloth is much less compliant, and exhibits more resonances. Butyl rubber a much better choice will break-down due to ozone in the air. The solution Dr. Luth determined due to his extensive background in chemistry was silicone rubber. Totally inert, extremely low resonance, proper durometer, impervious to moisture, as well as UV rays and a lifetime of greater than 99 yrs. Every other manufacturers surrounds are glued to the cone. This can lead to spurious resonances and even separation at the joint. Dr. Luth's solution was to change the chemical mix during molding from polymer to silicone rubber thus eliminating a joint completely. A seamless molding solution!

THE VOICE COIL (MSG Models)​

The dual voice coil in the HARTLEY speakers (220 MSG & 207 MSG) is based on a principle first developed by the British physicist, A.C. Barker, in 1938. Barker's "duode" coil consisted of two coaxial windings, isolated by a plastic film. By transformer action, high frequency signals imparted to the copper windings were induced on the aluminum shorted turn. The aluminum tube could move independently of the copper windings to vibrate the speaker cone to which it was connected. Barker's voice coil, although sound in principle, was never fully successful because he was never able to fully isolate the two sets of windings with the materials available at that time. However, developments in synthetic chemistry have enabled us to produce a highly compliant silicone compound, only 4 mils thin, which isolates the windings effectively and permits the inner aluminum tube to move independently at high frequencies. The HARTLEY aluminum tube is a complete circuit not slotted. It should be noted that in the HARTLEY speaker, the aluminum and copper windings are each connected to respective sections of a dual cone. In the Barker voice coil, the aluminum tube was the only part of the assembly fastened to the cone. Electrically, the dual voice coil may be considered an air-cored transformer, modified somewhat by the presence of a small amount of iron on the pole piece of the speaker magnet structure. The copper windings and aluminum tube comprise a voltage step-down transformer, in which the copper turns are the primary and the aluminum tube the secondary. Signals fed to the copper windings of the voice coil are induced by transformer action on the aluminum shorted turn. Because it is a step-down transformer, the induced voltages are lower and the current higher than the primary voltages and currents. Air-cored transformers are quite inefficient at low frequencies. Consequently, the current induced in the aluminum tube begins to drop sharply at 2000cps and virtually disappears at 1000cps. An elegant way of eliminating a crossover with its losses and distortions.

THE HEAT SINK (HS MODELS)​

All HARTLEY HS woofers employ a unique "heat sink" which is actually the aluminum tube the voice coil is wound on. The tube is cut so that a significant portion protrudes through the apex of the cone allowing the greatest concentration of heat (around the coil windings) to be dissipated through the tube outside the cone and into the air. During the coil winding a special high temperature epoxy, manufactured by HARTLEY, is applied to all layers of the windings and baked in with a temperature of over 450 degrees F. This extreme temperature far exceeds the rating of the copper wire itself!

THE SPIDER​

In the first HARTLEY speakers in the 1920's our spiders were made out of Bakelite and had four legs that were bolted to the magnet structure. The shape defined the name "spider". Today we still employ the same design but with materials to meet 21st Century standards. Spiders for the polymer series are made from tri-laminate fiberglass which is impervious to adverse weather conditions and strong enough to withstand parallel and perpendicular forces.

THE FRAME​

Most driver manufacturers use stamped steel frames. These stampings are inexpensive but they exhibit unwanted resonances. Ringing is often used when referring to this steel frame. All HARTLEY polymers drivers use a sand-cast aluminum frame, light and strong, inert and then polished. Yes, an expensive way to make a speaker frame.....also the best!
(EJ3: in their opinion and mine [for the moment]).