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JBL HDI-1200P Subwoofer Measurements and Conclusion


1200 outdoor testing 

Testing on the HDI-1200P was conducted with the microphone facing the woofer at a 1-meter distance and then scaled back to 2-meters in our graphs by subtracting 6dB in output. The temperature was recorded at 65F degrees with 80% humidity. The subwoofer’s gain was set to maximum, phase was set to 0, and the low pass filters were left off.

1200P Frequency Response 

The above graphs show the measured frequency responses for the JBL HDI-1200P subwoofer. Here we see a fairly neutral response although not quite absolute perfection. JBL’s spec for the response as “28Hz - 150Hz (-6dB)” is accurate. The anechoic range of this sub is pretty much 30Hz to 250Hz, and the in-room response should be able to extend that down to 25Hz or so in average domestic room sizes. The ports look to be tuned to around 30Hz, so this is not the deepest-digging subwoofer around, but that is what would be expected of a small ported enclosure. This extension should be enough to capture 99% of recorded music bass content and 90% of recorded movie bass content. However, there are some movies with extremely deep bass that might lose something with a 30Hz roll-off. It is nice to see some real upper bass extension, and these subs could easily be crossed over as high as 200Hz if the user wanted. The advantages of this are that a multi-sub system can address room modes above standard crossover frequencies without worrying about localization. The subs are also likely to deliver a greater dynamic range than most speakers are able in this mid-bass band as well. This extended upper bass range can be useful, so it is nice to see here, and unexpected since many of these long-throw, small-cone drivers tend to be on the heavier side which can just kill the response above 100Hz.

1200P CEA bursts 

Bassaholic MediumThe above CEA-2010 measurements are short-term bursts that show the subwoofer’s clean peak SPL before heavy distortion sets in. Our measurements have been referenced to 2-meter RMS, which is 9dB down from the standard requirement for the measurements to be shown at 1-meter peak. However most publicly available CEA-2010 measurements are shown at 2-meter RMS, so we followed that convention. The HDI-1200P was able to pass a 25Hz test tone, although not comfortably since that frequency lay below the port tuning frequency. As the frequency response measurements show, this sub is built for 30hz and above. 50Hz and 63Hz turn in an especially strong showing here, and that range serve as the basis for the fundamental frequency for a great deal of music, so the HDI-1200P should be able to give a very solid foundation for music even at loud listening levels. The response does taper off a bit at 80Hz and above, and that could be due to the weight of the moving mass or maybe induction chipping away at higher bass frequencies. The 31Hz tone burst was amp limited, and frequencies above that could not be pushed into any significant distortion levels. The sub is exceptionally clean above 30Hz, and it is evident that non-linear distortion was a parameter that JBL took seriously in their performance targets. While the HDI-1200P doesn’t technically qualify for our Bassaholics ‘Medium’ room size rating since it misses the output requirement at 25Hz, I will give it a ‘Medium’ anyway since it considerably exceeds the requirements for the ‘Medium’ room size rating at 31.5Hz and above.

1200 Compression Sweeps 

Testing for long-term output compression was done by first conducting a 20-second sweep tone where 50Hz hit 90 dB with the subwoofer 2 meters from the microphone. We then conduct further 20-second sweeps by raising the gain by 5dB until no more output could be wrung out of the subwoofer. These tests show us the long-term continuous headroom that the subwoofer is capable of. The HDI-1200P holds its response shape fairly well out past the 100dB level, and then what looks to be a moderate induction-related peak pops up centered around 50hz. The aluminum shorting ring isn’t quite enough to negate induction effects completely, but that is not a surprise given the large 3” voice coil with such a long throw. It’s a lot of copper with a lot of motion under a lot of magnet. There are certainly less expensive subwoofers that do offer more output, but this is overall a respectable level of output for a small ported 12”.

1200 THD 

The above graphs show the corresponding total harmonic distortion to the long-term output graphs. Essentially, they depict how linear the subwoofer remains for the corresponding drive level seen in the long-term sweeps. The quantity being measured is how much of the subwoofer’s output is distortion and is shown here as a percentage. As we saw in the burst measurements, the HDI-1200P is very happy at 30Hz and above but isn’t really built for anything under 30hz. It should be kept in mind that while distortion takes off like a rocket below 30Hz, output falls like a rock below 30Hz, so any distorted output will be very far down in level relative to clean output. Take a close look at the response shape seen here, and it is essentially an inverse of the frequency response shape. So don’t think that the sub will make all kinds of distress noises if it is pushed to play deep bass since it drastically reduces all output below 30Hz. It might make some audible distortion if only fed sub-30Hz sinewave test tones, but it wouldn’t be loud in level, and in real-world use, any distorted output would be masked by the much louder signal content above 30Hz.

 1200 2nd harmonic  1200 3rd harmonic

The above graphs depict measurements of the constituent harmonics from the long-term output sweeps and are what the total harmonic distortion measurements are composed of for the 2nd and 3rd harmonics. These individual harmonics can give us a clue as to what might be the cause of some quirk or non-linearity. We are only showing the 2nd and 3rd here because they more or less reflect the higher even-order and odd-order behaviors, although higher-order harmonics tend to be much further down as a percentage of distortion compared to the second and third.

What is interesting in the harmonic components of the HDI-1200P is that there are no odd-order distortion products to speak of within its operational range of 30Hz and above. JBL’s ‘Symmetric Field Design’ technology seems to be working extremely well! I don’t normally expect much of those kinds of marketing buzzwords, but the proof is in the pudding here. The nice thing about this is that the odd-order harmonics are much more audible than even-order harmonics, especially in music content, so what little distortion the HDI-1200P has is of the more benevolent variety. Even-order harmonic distortion can scarcely break over 5% which is what we also saw in burst testing. This is a very clean subwoofer that cannot be pushed into any audible distortion in its intended operating range.

1200 Group Delay 

Group delay is the measurement of how much time it takes for individual frequency bands of an input signal to be produced by the speaker. It can indicate that some frequency components are developing slower than others or are taking longer to decay. It is generally thought that 1.5 sound cycles are needed for group delay to be audible at bass frequencies, although there is an argument that group delay should remain under 20ms to be completely unnoticeable, but that is likely meant for mid and upper bass frequencies. Ported subs must necessarily exceed at least one cycle of group delay as a consequence of the ported design, but the HDI-1200P restricts its group delay to as little as possible. Port tuning frequencies just above one cycle and then quickly back down outside of port-resonance. The group delay is very unlikely to be anywhere near audibility since it occurs at such a deep frequency. By 40Hz, it is below 20ms which is one-fiftieth of a second, so the time domain behavior in music ranges is quite good. There shouldn’t be any audible bloat or overhang at all from the HDI-1200P, and those who hear that from a system with an HDI-1200P subwoofer are certainly suffering from room acoustics problems or calibration problems because it isn’t coming from the subwoofer itself.


I enjoyed spending time with the JBL HDI-1200P, and it was a treat to hear what it could do with the movies and music that I used with it. It is a fine subwoofer, but it absolutely should be for $3k. $3k is a lot of money for a subwoofer that doesn’t really dig deeper than 30Hz or compresses its response shape above 110dB. The basic performance attributes aren’t bad, but there are subs of similar size that surpass its overall performance level for a lower price point. What then is the reason to purchase the HDI-1200P? The reason is appearance and build quality. This thing is built like a tank and has some of the finest real-wood veneer I have seen on a subwoofer. It is a sub that offers very good performance and an attractive appearance that other household dwellers would be unlikely to object to even in rooms with a nicer decor. It straddles the line between a luxury item and high-performance audio gear.

1200P hero

The JBL HDI-1200p Subwoofer Beautiful Real Wood Veneer

JBL logo2The odd aspect of the HDI-1200P is that here is a modestly sized sub that compliments the HDI loudspeaker series, which are fairly large speakers for the most part. One would think that the buyers of the HDI speakers would be able to accommodate a larger sub than the 1200P, and that would enable JBL to get significantly greater performance by either tuning the ports for deeper frequencies or getting more output from the higher efficiency granted by larger enclosures. JBL instead opted for a smaller form factor that makes it acceptable for more household members. I would not have guessed they needed to do that, but I suppose JBL’s market research team knows their customer base better than I do. However, I am not here to evaluate JBL’s strategy but rather the individual product under review, so we have to take it on its own terms.

On its own terms, there is a lot to like here. While the HDI-1200P doesn’t dig down to extremely deep bass frequencies, it boasts audiophile-level fidelity above 30hz with superlative control of nonlinear distortion as well as very good time-domain behavior. Its dynamic range level is good although not quite spectacular. The inclusion of XLR inputs and a parametric EQ are niceties that tick checkboxes that you would expect to see in a sub of this pricing. It’s a classy-looking sub that isn’t very large and doesn’t resort to the usual gloss black finish for a high-end appearance (although gloss black is available to those who want that). And it has the kind of solidity that would be expected of fine furniture. It’s an expensive subwoofer, but it does fill a niche; high-quality bass from a small sub with high-end wood veneer and build quality. If that is your criteria, it won’t be easy to find a less expensive alternative. 


The Score Card

The scoring below is based on each piece of equipment doing the duty it is designed for. The numbers are weighed heavily with respect to the individual cost of each unit, thus giving a rating roughly equal to:

Performance × Price Factor/Value = Rating

Audioholics.com note: The ratings indicated below are based on subjective listening and objective testing of the product in question. The rating scale is based on performance/value ratio. If you notice better performing products in future reviews that have lower numbers in certain areas, be aware that the value factor is most likely the culprit. Other Audioholics reviewers may rate products solely based on performance, and each reviewer has his/her own system for ratings.

Audioholics Rating Scale

  • StarStarStarStarStar — Excellent
  • StarStarStarStar — Very Good
  • StarStarStar — Good
  • StarStar — Fair
  • Star — Poor
Bass ExtensionStarStarStar
Bass AccuracyStarStarStarStar
Build QualityStarStarStarStarStar
Fit and FinishStarStarStarStarStar
Ergonomics & UsabilityStarStarStarStar
Dynamic RangeStarStarStarStar
Attached Files
About the author:

James Larson is Audioholics' primary loudspeaker and subwoofer reviewer on account of his deep knowledge of loudspeaker functioning and performance and also his overall enthusiasm toward moving the state of audio science forward.

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Recent Forum Posts:

Prolix posts on October 09, 2021 15:27
I have a Revel b112, which I gather is pretty much a sealed version of the hdi-1200p. When I run audyssey its raw in-room response is flat through 20hz in my living room with 10' ceilings. It doesn't have the impact of the dual monolith 12s I have in the basement, but it's enough to blow the minds of regular humans, and it doesn't look out of place. I've been very happy with it for a number of years.
TLS Guy posts on October 08, 2021 00:03
Eppie, post: 1508969, member: 94526
Thank you for the graphs and photos. Does the depth of the box factor heavily in the calculations or is it primarily the length of the TL that yields the desired results? I was wondering if it would be practical to try and design an enclosure less than 11" deep or does that lead to a width and height that would not be practical? Sorry, but I haven't had the opportunity to play with the TL design software yet.

The pipe volume Vp is related to the VAS of the driver. The higher the VAS the larger the pipe volume needs to be. Understanding this was George Augspurger's great contribution to TL design.
Eppie posts on October 07, 2021 23:53
TLS Guy, post: 1508936, member: 29650
Here is the response of slim TL sub using the 10" Dayton sub driver….

Thank you for the graphs and photos. Does the depth of the box factor heavily in the calculations or is it primarily the length of the TL that yields the desired results? I was wondering if it would be practical to try and design an enclosure less than 11" deep or does that lead to a width and height that would not be practical? Sorry, but I haven't had the opportunity to play with the TL design software yet.
TLS Guy posts on October 07, 2021 18:33
Eppie, post: 1508900, member: 94526
Leon Speakers has been using the approach of designing slim cabinets, specializing in low profile side mounts and sound bars and offer slim subs (not TL) but the specs list them as only going down to 30Hz (in-wall) and 28Hz (slim build). Paradigm also sells in-walls but seem reluctant to post full specs. They only state the the low freq. extension is 19Hz-17Hz, but lack of proper specs seems rather telling. JL Audio seem to have a more interesting design approach, but even those tall Fathom subs are only rated down to 25Hz -3dB.

I imagine that any slim sub will face challenges due to limited excursion, especially since long excursion seems to be the buzz word with subs. I think you have your work cut out for you. We've seen what small drivers can do in the SVS 3000 Mirco and KEF Kube, which seems to imply that larger diameter drivers with shallow baskets would be the way to go. How deep is the in-wall in your great room? Do you think that there is a TL design that would work with a relatively shallow cabinet? I would assume that a TL design would require some minimum depth for the physics to still work. What about a driver array using multiple smaller subs to increase surface area but reduce depth, or would that just create a bloody mess?

Here is the response of slim TL sub using the 10“ Dayton sub driver.

This is the in room response of the three front speakers and sub, at all seating positions and the far side of the dinning room table. The green line is taken over the Kitchen cook top.

This is the TL

It is 11” deep, 5' long and 25“ high.

This is the room.

Note there is an open stairway.

That one driver fills the space very evenly, due to what organ builders refer to the encircling phenomenon of pipes.

The sub is very efficient and power is reduced 5 db below the other speakers or it overpowers them.

Cone excursion is not a problem as the pressure in the pipe at the driver is high and pipes control the driver like a vice. In my studio I use a total of four 10” SEAS Excel drivers in the right and left bass TLS. I have never bottomed the drivers despite vibrating the room, even at modest volume.

The best thing of all is that the bass quality is much higher than from a standard ported or sealed sub. It is incredibly realistic. Even that lone 10" driver can allow an organ to fill that space with authority.

There is no doubt whatsoever in my mind that TL subs, produce the most realistic and natural bass of any other design.
Mark E. Long posts on October 07, 2021 18:02
Verdinut, post: 1508925, member: 80194
No, you can't get an efficient infrasonic LF response from a little box, period. You will only get efficient subwoofer response below 20 Hz with a ported design.
Verdinut, post: 1508925, member: 80194
No, you can't get an efficient infrasonic LF response from a little box, period. You will only get efficient subwoofer response below 20 Hz with a ported design.
Iam quite aware of that my comment was a ment in jest .
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