JBL 2245H vs 2241H vs 2242H vs 2235H vs TAD 1601 Performance over the 30hz - 200Hz

[Ian Mackenzie]

I would look at it on the basis of where you want the box port frequency to produce the most output.

What is the goal?
Do you want very low sub bass output at the expense of higher bass output in the 35-50 region?
Do you want maximum visceral bass impact 35-50 hertz
Do you want maximum mid bass in a more compact enclosure 40-80 hertz

There are a few trade offs

On paper
1. The lower the box tuning (20-25 hertz) and the larger the enclosure (10-12 cu ft3)will produce lower maximum output from the port and woofer summed output at FB. This type of tuning will also have less maximum acoustic output in the 35-45 hertz region because the port output is much lower in the 20-25 region. If you want more low bass output look at multiple woofers and enclosures. (It’s subjective noticeably see below)

2. A somewhat less large enclosure volume (25% less than above ie 8-10 cuft3) with a higher port tuning frequency in the 28-36 hertz region will yield a system with significantly higher maximum acoustic output around the higher port tuning frequency. Consequently the maximum output below the port tuning frequency will diminish quickly. In practice this can be resolved with a high pass active frequency. For consumer applications this us generally not necessary. (This type of tuning is subjective most acceptable)

3. If maximum output as in a sound reinforcement application is an important look at the Xmax and peak excursion before damage of the driver for system reliability.

Maximally flat response, optimum volume or extended bass?
Some bass reflex enclosure simulators will offer preset tunings in these categories.

1. Maximally flat refers to the flattest system response in the pass band.
2. Optimum volume fits the closest response curve the high pass filter of tunings suggest
by the woofer TL parameters
3. Extended bass refers to a lower port tuning and a larger enclosure volume with a low
pass shelf curve in the response

Subjectively
Typically you will achieve a more visceral impact in option 2 with box tunings at 28-36 hertz and above with a somewhat smaller enclosure volume(8-10) This tuning will sound subjectively more dynamic than the same woofer with port tuning in the 20-25 region and larger enclosure 1.

The larger enclosure (10-12 cuft3) is more difficult to construct so that it is resonant free above 50 hertz. For this reason such large enclosure best limited to application below 80 hertz.

[1audiohack]

Scott,

… 2241/2242: you're tuning the woofers below their 35 hz Fs, this can become a slippery road at high level, more so for 2242 Fb @ 26 hz. I know JBL did it in tech sheet, but will they put in writing they'll recone it free if its been damaged, claiming abuse (used outside of normal terms/capabilities)? …

Richard

Tuning below Fs is not unusual or particularly dangerous.

JBL’s theater boxes 4642a and 4719?are tuned to 25Hz.

2242’s are pretty robust. I operated one slated for recone at 1800 Watts of low distortion 60Hz sine until I got tired of listening to it. That would be a direct connection to the 120V power grid.

Barry.

[Ian Mackenzie]

Tuning below Fs is not unusual or particularly dangerous.

I operated one slated for recone at 1800 Watts of low distortion 60Hz sine until I got tired of listening to it. That would be a direct connection to the 120V power grid.

Barry.

It’s been done already.

The Americans used isolated meeting chambers with multiple woofers humming at 60 hertz outside in the Cold War to keep secrets secret. But it didn’t stop counter espionage from within by Russian Moles.

[1audiohack]

It’s been done already…

Of course it has. The only thing new in the world it seems is the history you don’t know. Over and over, the ancients have stolen our secrets.

Barry.

[toddalin]

Based on the curves, as I have suggested, the 2241 gives the greatest "sense" of bass, even if it doesn't extend quite as low. Still, 32 Hz represents low C on the pedal board, and this is plenty low for what I listen to. Low E on a bass is ~40 Hz and the 2241 is all over the other varients at this frequency.

[RMC]

Hi Barry,

If my memory is correct many years ago Gene Czerwinski of Cerwin-Vega would go to trade shows and plug his Stroker woofer in 120V AC to show how robust it was. Have you stolen his "secret", lol.

That being said, downtuning puts more strain on a woofer. However nowadays with the larger excursion capabilities from woofers might explain that manufacturers are increasingly adventurous.

Ancestor 2240 had Fs 30hz and JBL modeled it in 10 cu ft but tuned it at 30hz, so at Fs not lower. The increased excursion capability of 2241 and 2242 probably lead JBL to be more daring in tuning these 5 hz below driver Fs in the spec sheets.

If you go from a B4 alignment to a B6, or straight for a B6, you down tune the box somewhat and then apply a boost/cut filter. The natural low end roll-off of the down tuned box, plus the cut filter, add to make an even steeper roll-off. My understanding is the 12 db/oct electrical cut filter has dual purpose: rolloff part of the Q = 2 boost near the filter's base on the VLF side, and at the same time mitigating some of the excursion strain put on the woofer using that same rolloff (two birds with one stone). So i'm a little skeptical that a sizeable downtuning with no filter would present little or no risk for a woofer at high drive. Wouldn't this mean the B6 cut filter has a single action only (rolling off part of the boost) and forget the rest like also helping decrease cone travel ?

2241 is a little different story than the others in the sense that its a high Qts driver, with these having more ability to naturally sustain (no EQ or filter) flat bass in a deeper bandwidth, than lower Qts units. Eargle has a couple of examples of this.

That Qts leading to a C4 standard alignment with some ripple in response (though it can be pretty small). A C4 is normally tuned lower than driver Fs for flat response, otherwise a response bump may appear (subject to cab size). The other two (2240 and 2242) will lead to Qb3 alignments or a derivative of this if the user models it his own way as i do.

In the traditional 18" SR woofer JBL went from 2240 Qts .23, to 2241 Qts .40 and then 2242 Qts .275 . So from low to high then back to somewhat low Qts respectively. (Btw back to high again with 2269 .36 !)

Hard to say exactly why this going back or so to an older "recipe" for 2242 but i may risk the following: high Qts woofers don't have as good transient response and likewise for their C4 alignments (Dickason and Eargle). In other words maybe users and sound contractors especially didn't recognized the 2240 sound in the 2241??

Finally, not everyone has the means to recone at will, i guess that's an incentive to keep a driver alive and well.

Richard

[RMC]

I previously posted this from Eargle's Loudspeaker Handbook, regarding cabs Fb shifts. Different application but the same downtuning principle and its impact (originally a Gander & Eargle AES paper).

[RMC]

Also i previously posted, from E-V's Pro Sound Facts, about step-down mode, essentially the same as downtuning initially. Having seen examples their slight reduction mentioned here is in the 2-3 db range. Applying a 3 db derating corresponds to half the power, so a 500W driver becomes a 250W unit. Besides E-V says if you need full power capacity from a woofer then don't step-down (downtune the cab).

[Ian Mackenzie]

One of the less considered woofer properties is linearity.

Linearity in the context of the cone area, Xmax and power compression defines linearity.

The 2245H can be tuned on paper to the same response of a 2235H.

The audibility of the 2245H is astonishing. It has more authority and impact. The larger driver also couples better to adjacent room boundaries.

Another consideration is that JBL measured the LF specs of systems using a passive low pass woofer crossover network. JBL took advantage of the benefits of the L1 dcr in the woofer filter to modify the total system LF response thus improving the voicing. The action of the DCR is to increase the total woofer QTS. By re tuning the enclosure volume and port frequency an improvement in LF extension while maintaining sensitivity can be obtained. Hoge has published documents on the subject. Gary Margolis former applications engineer at JBL also published some optimised LF tunings. Greg Timbers then implemented a Bessel tuning in the M9500 using staggered enclosure tunings.

In the DD67000 dual woofer system Greg Timbers originally designed the DD66000-67000 as a tri amp system. The additional inductor DCR of the low frequency passive crossovers benefits the LF extension and voicing of the passive system.

But in the tri amp mode the system sounded too lean so we added a 100 hz LF shelf filter with +4 db of boost. I don’t recall the specific +4 db frequency. Greg just knew what was required.

If you have a flexible dsp active crossover l would encourage experimenting with modest 0 - +4 LF boost at or above the port frequency and listen to the results with your system in your room. A subtle lift in the response below 100 hertz can really improve the overall balance of a system.

If using an 18 inch external self powered sub just dial in the level of the sub and listen. Measurements with REW will enable validation of your actual LF response including all the dips and peaks.

[short_circutz2]

Tuning below Fs is not unusual or particularly dangerous. JBL’s theater boxes 4642a and 4719?are tuned to 25Hz. 2242’s are pretty robust. I operated one slated for recone at 1800 Watts of low distortion 60Hz sine until I got tired of listening to it. That would be a direct connection to the 120V power grid. Barry.

To attest to JBL being robust...Bit of background first...My father is from a very small community kind of in the middle of nowhere. Electronic parts were hard to get your hands on. Dad jad the first rock band in his community in the early 60s and was a JBL fan right from the start. He was using a normal edison type plug and socket to join his D130 loaded cab to his guitar head. Until someone "trying to be helpful" plugged the cord for the speaker cab into the wall outlet instead. 115v of 60Hz was all you could hear in the hall until dad made it to the stage to unplug it. That D130 not only surived the punishment, but dad went on to play many years thru that cabinet. To think that even a very much older 15 rated at a fraction of the power of the 2242 was also able to survive this just shows how robust JBL has always been.

[RMC]

short_circutz2,

On the other hand, in the most spectacular failure thread, both 2242 in your example were ripped and smoked!

This should remind people even the 2242 is not invincible to abuse. Hence my previous caution.

So you win some and you lose some...

Richard

[1audiohack]

Man has never made anything that man can’t break.

I earn my living trying to overcome the above.

Barry.

[Mr. Widget]

Man has never made anything that man can’t break.

I earn my living trying to overcome the above.

Barry.

With emphasis on “earn”!

Widget

[RMC]

I wonder though if 2269 with huge excursion capability and power capacity might have survived such DJ abuse ? (assuming it existed at the time)

[DerekTheGreat]

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