DIY multi way active JBL speakers with bass system

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JBL 2446 on 2360 horns, 2123 midrange and 2226 midbass drivers. LMS Ultra 5400 subwoofers

This is the current state and concept of my fully active DIY big loudspeaker project. The system is built modular to allow for experimentation, but as the details are carved out the system will be more integrated and several drivers will be housed in one neat looking enclosure.

Make no mistake, these odd looking speakers are not intended to induce any kind of positive visual response, but they sound spectacular and you want to have your eyes closed while doing serious listening anyways, haha.

Goal of the active multi way loudspeakers

Deep, precise and punchy bass with powerful dynamics across the board at low distortion levels. The mids needed to be transparent and the top end should be airy and detailed without sounding harsh and etched. Furthermore, the system needed to be fully active to avoid any passive components in the signal chain (besides cables). As for the expenditure involved, the system needed to be fairly affordable without any types of esoteric components.

Waterfall of all subwoofers and midbass modules from 20-500 Hz

This is the waterfall of the system between 20-500 Hz up to 300ms (about 1/3rd of a second). If you know how to read these waterfall measurments you will agree that it is very good and that the bass is dry and tight as the low frequency energy is not lingering on in the room for a long time.

System details

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Because I care somewhat about surround I use Yamaha CX-A5000 surround sound processor. It's a past flagship of Yamaha prior to the current CX-A5100 and the prepro is very capable yielding very good sound quality. For rear channels I use a pair of JBL LSR308 which are small active studio monitors. They serve their purpose to create some immersive feel when watching movies. I don't use a center channel as the large JBL 2360 horns have a very wide dispersion pattern and I'm basically satisfied running a phantom center channel as this system is mainly for music.

For crossover, delay and other parametric EQ filters a pair of miniDSP 4x10 HD are used. They each have 8 analog output channels and – for the price – a very high level of fidelity. Unfortunately, miniDSP is somewhat prone to noise issues but that has been solved by trading away some headroom by using passive line level attenuators. The attenuators are necessary regardless of noise issues due to the difference in sensitivity between the drivers, and by using analog attenuation you don't risk loss of resolution by reducing the signal in the digital domain.

Transducers and what they contribute

The loudspeakers are 4 way + the addition of 4 subwoofers to achieve a powerful and dynamic low end. All enclosures are closed for a few reasons; firstly to keep the size of the system down as bass reflex with a low tuning gets very big, secondly, to keep extension and little group delay, and thirdly because of design complexities of ported vs sealed subs and midbass modules.

In the following table there's an outline of each driver and how they are being used, in additon to the manufacturer's specification sheets are linked. Furthermore, the JBL drivers are older legacy drivers and the ones still available new are very steeply priced, so I've included eBay links for those of you who want to see the market price for used drivers as it's possible to get great deals on these drivers through eBay.

Transducer and horn Pcs Highest Frequency Lowest frequency
JBL 2404H (spec) (eBay) 2 20 kHz 8 kHz
JBL 2446H (spec) (eBay) with 2360A horn (spec) (eBay) 2 8 kHz 1.2 kHz
JBL 2123H (spec) (eBay) 2 1.2 kHz 300 Hz
JBL 2226H (spec) (eBay) 4 300 Hz 60 Hz
TC Sounds LMS Ultra 5400 (spec) (eBay) 4 60 Hz  

Here are some acoustical measurments with variable smoothing (less smoothing down low, and more up high) depicting the performance of the loudspeakers without the subwoofers and rougly set crossover settings.

Measurement of acoustic performance with the crossover settings for the 4-way loudspeakers

The early high frequency drop off is due to the measurement microphone.

Measurement of the loudspeaker as a whole with set crossover settings

These measurments were taken from sweetspot and are not gated, so there's obviously room for improvement and the focus is on optimizing the phase and PEQ filter settings to improve the frequency response and timing further.

This is the left speaker only and with the subs included and a low-shelf filter with positive gain it sounds really awesome, but an idea worth experimenting with is to use steeper filters than 4th order Linkwitz-Riley, particularly between the upper midrange horn and the UHF as some signs of aggressiveness can be heard due to the 10kHz ringing in the 2446 diaphragm. Loading 2446 with Truextent's Beryllium diaphragms will probably remove this problem all together, as Be has less high frequency ringing than the original ribbed Titanium.

As a test BW 4th order filters were implemented and they yielded better subjective results in comparison to the LR 4th order filters. They sounded less harsh and overall more natural and is currently in place.

TC Sounds LMS Ultra 5400, 4 x 18" long throw subwoofers

These cover the range from 60 Hz and down and due to room gain there is ample headroom downwards of 10 Hz :) As consensus has it these these drivers are the best long throw drivers in the world and they sure sound like it. They were not cheap and for the same price you could have doubled if not quadrupled the surface area with other drivers and probably exceeded the performance, but when you are space limited you need to take a pick.

I've shoken my head in disbelief many times listening to the deep and precise bass from these drivers. There is nothing even resembling one note bass and there is perfect pitch all the way down and below human hearing, where they are able to create a deep feeling of pressure in your ear and room. You can perceive the bass, but not hear it. They are truly excellent for movies to say the least, and they also do a fantastic job for music reproduction. I would not want a stereo system without a bass system again. The bass is just too important.

JBL 2226, 2 x 15" midbass

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As great as the LMSU drivers are, they are engineered for the sub bass and are not as excellent in the midbass region. They lack the same chest pounding punch and smack of the lighter weight pro drivers with higher sensitivity, don't get me wrong, the sub-drivers will make your stomach turn, but the tactile chest pounding lies around 70-125 Hz and nothing beats a pro driver in that area. If you want punchy midbass you need speaker that can reproduce it or you need to build a two way bass system with subwoofers for the deepest bass and prodrivers for the midbass.

These drivers are excellent at giving you that tactile chest pounding action and they also do fairly well towards the 300 Hz mark, but it's all downhill from there. It would be beneficial to swap these drivers out with something better, like JBL 2216Nd, but those are rather costly and not particularly easy to get a hold of.

JBL 2123, 10" lower midrange

These drivers are extremely important for the lower mids and creating the snap of the tactile punch. Again, the tactile chest punch lies between 70-125 Hz, but the punch also has a lot of overtones, and these overtones stretch far above that and a lot of the important information in the perception of the punch stretches up to 1-2 kHz and even above that. If you can't reproduce the overtones, the punch is felt but not heard. If you have it optimized the punch will be felt and you will blink as a reflex each time the punch hits.

If JBL 2226 is run too high they will paint with a wide brush and sound a little dull and grainy, not particularly detailed. The JBL 2123 10" midrange was a huge upgrade in this regard. It's fast on its feet and makes the whole system sound tighter and more natural. By adding the 2123 some of the load on the compression driver above it is also lessened and it too performs better.

The 2123 midrange drivers sit in a couple of fairly simple, but heavily damped closed boxes. These enclosures were mainly built for test purposes and will be rebuilt to higher standards.

JBL 2123 DIY midrange driver enclosure unfolded before glue

Here are the finished enclosures for the 10" midrange drivers.

JBL 2123 enclosures

The boxes turned out fairly nice and will be repurposed as cat houses after they're rebuilt :)

JBL 2446 with JBL 2360A horns for the upper midrange

JBL 2360A horns directivity and disperison pattern

Some people use these in 2-way configurations, often together with a 2226 in a chunky bass reflex enclosure tuned to 35-40 Hz. To get more output in the top end they use heavy amounts of EQ, arguing that the high power ratings and sensitivity of these drivers have no problem with that in a home environment where you mostly cruise around fractions of a watt, even during dynamic bursts.

I tried doing this but used several 2226 in sealed instead of ported boxes. Unfortunately it was seriously lacking on both sides of the spectrum. Some people feel that pushing a few drivers out of their comfort zone is better than adding to the complexity by introducing another driver and the troubles of integrating it, but after having tried to extract maximum performance in a 2-way setup there was no other way about it than to add another driver above them.

There are several shortcomings in pushing these above 8 kHz, the first one being the 4" diaphragm becoming beamy at these short wavelengths, the second being not to consider the narrowing dispersion pattern which is evident from JBL's specifications on the big 2360A horns. As is obvious they become directional above 10 kHz. This will skew the soundpower vastly, and research has found that a uniform soundpower curve is preferable. The third reason is that 2446 with (ribbed) Titanium diaphragms has a lot of ringing around 10 kHz, and if you add EQ you are just going to make matters worse. They hare going to sound harsh and piercing with EQ on top. Some people swap out the Ti diaphragms with Truextent's Beryllium diaphragms and that will lessen the ringing, but you still have the same issues with directionality of the big diapragm and the narrowing of the 2360 horns above 10 kHz.

When running 2446 in 2360 with aid on top however, they are magical. They are super quick and dynamic with amazing details and a true bargain for the second hand price they run for.

JBL 2404, Ultra High Frequency Transducer

As touched upon in the discussion about 2446 the top end is lacking. JBL 2404 UHF ensures great top end clarity and detail with a better dispersion pattern than the JBL 2360 horns at these high frequencies.

Wooden bracket for mounting JBL 2404 to JBL 2360 horns

The ring radiators are mounted to a pair of prototype brackets which in turn are mounted to the large 2360 horns using the stock holes intended to secure the horns to ceilings etc using wires. In other words, I've flipped the 2360 horns 180 degrees and screwed mounted the brackets to them using those holes. The bracket is going to be rebuilt to be less obtrusive but I can't stress how important it was to get this transducer positioned below the large horns and how much it contributed to the overall detail and air of the system.

With the 2404 you get much more high end shimmer and detail, and it doesn't sound etched and sibilant like it does when you boost the 2446 Titanium diaphragms with massive amounts of EQ. It's a cheap driver and well worth it, but you'll obviously have to tackle another crossover point.

Amplifiers

With an active system you also need a lot of amplifiers.

The speakers are driven by 6 x Anaview AMS0100-2300 amplifier modules in bridged mode in a DIY amp. These amplifiers are used to power the midrange, upper midrange and the ultra high frequencies. In addition, 2 x AMS1000 which are bigger and meatier modules are used to drive the midbass. The subwoofer system is driven by a pair of Labgruppen FP14000 clones from Sanway. In other words every driver in the system has a separate amplifier channel (and DSP channel).

Seeing as the midbass drivers can handle 600W of power each, AMS1000 is a bit small and I've also got a pair of Behringer INUKE NU6000 without the DSP module (to avoid an additional ADDA conversion as that adds to the noise floor and may be detrimental to the sound quality). I aim to do some amplifier reviews and comparisons in the future, so going into the amplifiers' performance is outside the scope of this article. What I can say though is that I'm excited about the performance of the Anaview amplifiers and the system as a whole. It looks weird (like a DIY audio work in progress project should), but it hits higher than it looks. :D

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