Feel the vibes.


I haven't been adding much to my IB blog recently. My wife and I are still enjoying a couple of new (hired) films each weekend. The IB subwoofer continues to surprise and delight when the film asks for it. The system is also switched on for the odd, favourite TV series. Though TV soundtracks are never remotely on the scale of action films. Why should they bother when the average viewer is listening  to the TV's own speakers?

All our TV is sourced from our digital satellite receiver and two dishes. Terrestrial TV has never been successful locally due to our location in a hollow in the landscape surrounded by low hills. The Danish government chooses to code the Danish TV channels on satellite. This despite the highest TV license fee imaginable. 2260DKK = £264 GBP or $418 US. Is an exclamation mark really necessary?

Without a smart card one cannot watch Danish TV by satellite. The companies which provide Commercial TV channel "packs" just add in the Danish channels as an afterthought. Without  paying for a TV pack one cannot get a free smart card just for the Danish channels.

We can receive about 2000 different TV channels and probably almost as many radio channels . I've lost count of how many of these are free of coding. Literally hundreds and hundreds including HD channels. But no Danish channels at all.

For receiving Danish terrestrial TV we would need to take a chance on buying a digital tuner, antenna and possibly a mast to receive the digital Danish terrestrial channels. So we never see Danish TV. Nor listen to Danish radio. Not ever.

The irony is that the majority of immigrants to Denmark have satellite dishes to watch their home programmes. The government complains that they do not integrate fully into Danish society. (if at all) I wonder why? Could it be that the only Danish culture they ever see is in the checkout queue at the local supermarket?

This wasn't the real reason I started scribbling this post. We were watching a hired DVD of "X-men First Class" this evening. I went down to the kitchen to make a cup of coffee without pausing the film. The infrasonics in the kitchen and bathroom were quite remarkable. These rooms lie partly under the IB enclosure. So it is hardly surprising that one can hear the bass through the wooden floor. Which is boarded both above and below. Thus offering little attenuation or damping.

These infrasonics seem reduced upstairs. Or they are masked by higher frequencies. There is no shortage of weird pressure effects and the air being "shredded". (as I usually like to describe it) What seems to be missing are the very slow beating effects. Where each pressure cycle can be clearly sensed. Giving the illusion of almost being able to count the beats. Though one would need to be incredibly fleet of tongue to do so aloud. They are certainly present on classical organ music but not so often on films. Perhaps it is simply a case of being able to focus on the infrasonics downstairs in the absence of other frequencies?

It occurs to me to try a few REW sweeps with the microphone downstairs. Just to see what actually gets through the floor. My wife has often mentioned the kitchen ceiling rippling as she prepared a meal. Usually during one of my classical organ music, listening sessions. Or when she nipped downstairs to check a meal's progress during a film. Not quite the nausea that the array used to cause in the bathroom. But still worth trying an REW sweep or two:

NB. All doors between rooms were closed during testing. Peak frequency levels were lifted in REW to match the listening position. A Galaxy 140 SPL meter was used as the test microphone with matching REW .cal file. Meter set to low range, C-weighting on a 10m twin coax cable to Creative Live! external sound card: Only the subwoofer was in operation.

Too much complexity despite peak levels being matched?

Listening position ^

Some 9' from the manifold opening in the left wall.
Measured with the SPL meter placed on a cushion on the seat of my chair.
At normal, seated, ear level, with the SPL meter on a tripod the lower bass dominates more than this. 

Middle of IB enclosure ^

Only 3 feet from the 6' tall, 8 x 15" driver manifold. The enclosure is about 600cuft minus open storage. It is still very leaky to the outdoors at the very edge of the roof. Plans are afoot to finish the last row of insulation between the final pair of rafters before winter. The 45 degree sloping ceiling will then be finally boarded over.

Bottom of open stairs ^

There seems to be a distinct tuned port effect from the open stairwell. 20-25Hz is only borderline audible using sinewaves. My own audible barrier is at 25Hz as a very soft, fluttering effect.

Downstairs hall ^

A small space with a boarded ceiling below the IB enclosure. The hall doors to bathroom, kitchen and living room were closed. A double resonance.

Bathroom ^

Thinly boarded ceiling hiding the joists. It lies directly below the IB enclosure. A distinctly narrow plateau from 15-20Hz. Hardly surprising the vibes can be felt rather than heard!

Kitchen ^

Boarded ceiling between exposed joists partially under the IB enclosure.The peak is at 20hz with strong extension to even lower frequencies.

Other end of listening room ^

A triangular opening, about the size of a door, leads from one half of the attic listening room to the other. The room is split almost exactly in two by the chimney. A broad peak with an emphasis on the very low bass. 9-15Hz is all infrasonic.

Middle of downstairs living room ^

Open to the listening room via the open stairwell. Actually a simple rectangular opening in the floor/ceiling. There may be a bandpass effect at work here. A 9Hz peak!

As expected, the lower frequencies dominate. With an emphasis on the infrasonics. This is hardly surprising given the ready willingness of boarded surfaces to resonate and retransmit the acoustic (cyclic pressure variation) signal which excited them in the first place.

From memory, the levels downstairs were 10-15dB below the listening room levels. Though I made no real effort to record them. REW has recorded all calibration levels as the same. So I had better get busy and record actual levels relative to the listening position. The information might be useful in that it will give some idea of bass "leakage" between rooms with wooden floors.


I have discussed contractor's, plate vibrators here before. Today I came across another. Outside a supermarket I was visiting was a very deep trench. A contractor was working at consolidating the gravel backfill. The noise he was making was all low frequency. My chest was resonating strongly which usually means somewhere up around 140hz. Though the clearly audible sound reminded me more of my high level tests with sinewaves at 40hz. Very unpleasant it was too! It was actually far more comfortable to go much closer than to stand 20 yards away loading my shopping. I don't know why this should be.

As promised I have checked the noise levels leaking downstairs and elsewhere:

I opened REW and chose Preferences, Subwoofer, Check Levels. Then I switched on the audio system. I set the level at 85dB(C) at the listening position using the system's volume control and the Galaxy140 SPL  meter. This was set to the 80-100dB range C-weighting  - Slow. I shut all the doors as I moved from room to room with the meter held aloft like an Olympic torch.

The levels were roughly 8-10dB down in the other half of the room. 10-15dB down in the downstairs living room, bathroom and hall. And, all of 20dB down in the kitchen. Turning off the speaker amp and repeating the exercise made no real difference. There was some variation (about 3-5dB) as I moved around in each space. There were measurably higher sound pressure levels against solid room boundaries.

The ceiling vibrations downstairs must be quite narrow band. On film LFE the IB easily hits peaks of 110dB+ as read directly on the SPL meter. This would easily equate to 90dB+ levels even in the kitchen.

I had no desire to set the system to a steady state SPL much above 85dB(C). It is not at all pleasant to subject oneself to loud, pink noise. Nor would playing high levels of sinewaves be any more comfortable.

No doubt one could eventually reproduce the resonant frequency of the downstairs ceilings. Provided, of course, one wore ear defenders while in the listening room. An aid downstairs to report any resonant effects, as frequency was adjusted up and down via the mouse, would speed things up. I would imagine these resonances lie deep in the infrasonic region rather than the audible.


I tried something I haven't watched for ages. Lord of The Rings: Return of The King. I laid the Galaxy 140 SPL meter down on a cushion about 9 feet from the IB manifold. It was left on Max Hold, C-weighting, 80-130dB range. By the time the film was finished it had hit 119.7dB(C). My wife was outside gardening for the first hour. She said the bass was very audible and rather repetitive. Boom-boom, rattle. Boom-boom, rattle! :-)

A small victory was gained against a continuing, slight problem of mould on the inner back panel of the manifold. I simply stapled a black, closed-cell foam, camping mattress onto the outer back panel of the manifold. (from top to bottom) The extra insulation, provided by the foam, seems to have cured the problem of continuous dampness. This only occurred on the lower back panel inside the manifold. The drivers and side panels seemed unaffected.

Only thin, office-type staples were used to fix the foam. To allow easy removal if desired. This panel is invisible from the audio room but I used black foam to match the manifold anyway. Checking with a torch shows that the inside back panel remains perfectly dry now.

I really must finish insulating the last bay of the roof above the IB enclosure. This requires working from above. Weather conditions never seemed suitable this year. With constant winds. Having fallen off the roof before I am not allowed up there if there is the slightest risk.

Click on any image for an enlargement.


Faulty CX2310 mute switches


Just a warning that the push button, channel mute switches (two of which are arrowed above) can be temperamental.  

Click on the image for an enlargement. Back click to return to the text.

Last night we watched a film on TV and we could hear no bass at all. Since we couldn't pause the film we watched it to the end and then went to bed.

Checking the next morning, we had completely lost one channel of bass and what remained was scratchy as hell. As if all four drivers had bottomed out on that channel! Which should have been impossible given the usual tiny excursions on an eight x 15" driver subwoofer.

I turned everything off and pulled every plug in the entire system and reinserted them all to clean the contact surfaces. That is quite a lot of plugs!

Then I switched everything back on and twiddled with every knob. I waggled every driver connecting wire and speaker cable. Nothing made any audible difference.

Time to get serious! So I took off the organ CD I had been playing and put on Bass Outlaws. Just to ensure I had a strong and continuous bass signal to play with.

Finally, I found that one CX2310 mute switch was electrically stuck in the mute position despite the light being off. It was very noisy when pressed in and out. While the other switch was scratchy and intermittent in its switching behaviour. It was this channel which was producing the rattly, scratchy noise in the bass.

A few repeated presses and both switch faults cleared. Suddenly all the bass came back with a vengeance! I often use these mute switches when testing individual channels with REW. So they may have had rather more exercise than is usual.

So now we know where Behringer saved the pennies on this inexpensive active crossover: On switch quality and reliability. Worth bearing in mind if you have similar symptoms.


The beast is loose at last!

Mixing in the LFE has released a violent monster. We have just watched "The Last Air Bender" with terrifying levels of bass suddenly unleashed from nowhere.

After the first warning, when the whole house shook like a leaf, I turned the EP2500 controls right down from 12 o'clock. When the house was still about to collapse I turned the LFE right down on the mixer control. A cut of about 10dB. I was till getting occasional red flashes on the BFD with every surface vibrating violently. I have never experienced anything like it before.

Years of messing about with downmixing had not prepared me for this. The highest I ever registered (during a film) before, was about 111dB(C) on the Galaxy SPL meter. It was brutal and certainly impressive but almost a whimper compared with the present performance.

Being completely dark at the time I had no way to tell what the cone excursions looked like. Eight 15" drivers moving in unison never felt so dangerous as they do now. I know the IB can do 135+dB on sinewaves above 30Hz without much sign of anything happening at all.

That seemed like mere child's play compared with what we just experienced. The walls, ceiling, floor and windows were shaking so hard I feared for the safety of the structure. The vibration through the floor was literally painful. The air around us was being shredded by an incredibly forceful shaking.

Every moment of film watching, prior to mixing in the LFE, feels as if it has been completely wasted. I hadn't a clue what I had been missing even on DTS. I had sound quality aplenty but the infrasonics were almost absent. My wife kept saying that the SVS cylinder was far more impressive. I am ashamed to admit she was right. I had been fooling myself that SQ was more important than the physical violence of which a large subwoofer is so easily capable.

I was so keen to believe that my IB was impressive that I shut out the memories of rattling eyeballs. The weird, slow waves of bass which passed eerily through the room. The terrible shaking of dragon's wings on LOTR. All this from a puny 12" driver in a cardboard cylinder covered in a thin rug.

Not even a better model either. My SVS was the cheapest (though tallest) of their range when I imported it.  No wonder it had turned my wife onto serious bass and infrasonics. We were both incredibly impressed right out of the box. We went around with a silly SVS grin for literally ages.

Then came the demand for more. For greater safety on the really serious peaks. The SVS seemed to peak at about 107dB on the meter when there was a loud bass roar. The IB seemed like the obvious answer at the time. It went a bit louder than the cylinder but was hampered by very non-spec drivers and a flimsy baffle wall.

Then the array gave way to a manifold and a serious gain in output and drop in vibration. Then newer drivers arrived to replace the old ones. Then I built all eight into a box taller than myself. Quite honestly it was all a complete waste of effort for films! We watched literally hundreds of films without the bass which the director had intended.

I was  very seriously handicapped by the lack of LFE. On music the IB went loud and deep. Only fear kept levels reasonably modest. On films the bass only went loud when the dialogue and everything else was far too loud. I read other people's descriptions of film bass and buried my head in the rock wool lining of my enclosure. I was in serious denial.

The weird thing was that I could easily make myself nauseous on organ music. Films were a loud disappointment. The bass was certainly there but not like it should and could have have been. It was exhausting sitting through an action film at reference level without the special bass sound effects.

Now I don't know whether to feel like a complete fraud or a complete chump. So much potential was just sitting there with so little reward. Until now. The mixer has finally allowed me to inject the LFE into the front channels.

The IB must have hit 130dB (briefly) on the effects at the start of the film we watched last night. "The Last Air Bender".  Without any exaggeration the vicious vibrations were really very frightening. My arm shot out to cut the bass on the mixer. Then I went out to the EP2500 and cut that to zero on both controls. I was still seeing occasional red (clipping) lights on the BFD. The air, floor and every surface in the room were still shaking incredibly violently at times. It sounded as if everything was literally going to come apart. An odd film with good points and bad.

I shall have to go back to the beginning and recalibrate the bass channels and the IB relative to the speakers. I remember leaving the IB/speaker calibration flat on "The Calibrator" DVD after discovering it was a a few dB "hot". The speakers didn't sound as loud as usual when we started watching the film and I turned up the volume to get clearer dialogue. That may be where the problems started.

Another update 26/2/11. Just watched XXX with Vin Diesel on DVD. The avalanche scene hit 117dB(C) Max hold on the Galaxy 140 with no red lights on the BFD. It sounded strong without the imminent threat of damage. The mixer BFD control was at 12 o'clock. I should have measured the explosion at the earlier drug bust helicopter scene. I think it was a bit louder. Exterminator Salvation played at up to 111dB(C).

March 2011 RED and Takers both peaked out at around 115dB with no red lights on the BFD. The hotel gunfight on Takers was spectacular. It was this scene I checked on the Galaxy 140 SPL meter afterwards. Both films were good fun.

Another update at the end of March 2011: Instead of previous attempts to balance the drivers I am trying balancing the orange lights on the EP2500. Previously I have tried to match the frequency responses of the two very different sets of AEIB15 drivers. This didn't work too well because it robbed the drivers of energy in their respective power bands. This greatly reduced impact and had me searching for alternative ways to get it back. OBs and small sealed boxes were tried but discarded on SQ and other grounds.

I am now using only one filter on the BFD. +16dB @ 20Hz with 120BW on the older 32Hz, vinyl coned drivers. They don't do deep bass without massive boost. Now both sets of drivers are still very different. The older 32Hz drivers are stronger higher up. The newer, paper coned, 13Hz drivers roll off early at the top end. How best to match them so they share their output to best effect? I have tried matching their excursions on programme material but this isn't ideal as it is so frequency dependent.

One day I was watching the orange lights on the EP2500. Just checking for clipping on very loud LFE effects. It was obvious that one channel had a continuous orange light while other only flashed on now and then. I have yet to see a red clipping light despite all my audio games. The two sets of drivers not only have very different physical characteristics but also different impedances. It occurred to me that I should try to match these orange lights on broadband LFE effects. The EP2500s controls ended up at 90 degrees to each other. I then physically checked the excursions with my fingertips on the outer suspensions of each set of drivers.

On bassy music (like Bass Outlaws) the drivers show quite serious variations in excursion. This is unavoidable. On deep and continuous LFE "roars" the drivers are much better matched. This suggests (to me at least) that they are now sharing output duties more evenly. The sound and feel very strong on films now. With some amazing infrasonic effects on recent films. I must find time to try some of the old bassy film classics like LOTR. I have never heard them played properly on my various IBs.

Of course nobody sensible would use two very different sets of drivers in one IB. I had no choice in the matter. I was originally supplied with a set of four very poor quality, very badly machined and cosmetically unfinished IB 15s.

After much fretting about the missing infrasonic bass I discovered they had a totally non-spec Fs of 32Hz instead of 16hz. I had followed a thread on an audio forum where another owner was complaining about his IB15s. So I tested my drivers myself. Using REW, a small amplifier and a series resistor I discovered Fs averaged nearly 33hz instead of the claimed 16Hz.

Later, when John H @ AE offered me four of his latest 16Hz IB drivers I discovered these were non-spec too. Measuring at 13Hz average Fs. He must have dumped some of the pre-production prototypes on me. At least they were properly finished this time. They cost me a lot of money to get delivered and cleared by the freight company.

John had originally told me he would pay my costs but didn't. After posting a favourable review on his AE forum I have now been banned. Presumably for speaking up about his non-spec drivers on another forum. It seems supplies of his excellent IB drivers have now dried up. He seems to be incredibly unlucky in his choice of workers and suppliers. Last I heard he was working alone to catch up on backlogs of unfilled orders going back for over a year! Dé jà vu!

Ironically, Fi, the only other supplier of specialist IB drivers, is restructuring. Henceforth production of all their HT drivers will be under the Blueprint name. It seems too many customers were using their HT drivers in car audio applications and breaking them. Several months without any IB drivers being available is causing some disquiet in IB circles.  Blueprint hasn't made any public announcements for several months.

If there is any doubt about the latest boost in performance of my IB you may find the following amusing: My wife had gone downstairs while I set up the system for a new hired film. She came back up with a bowl of yoghurt just as an LFE moment hit. She was so shocked she poured her yoghurt all down the front of my system rack! Of course I switched everything off as quickly as possible. Then there was an intermission while everything was cleaned up again. No damage was done but it is revealing of the incredible shock value we are now getting from the IB. :-)



The mutual benefits of a constructive forum


Forums are strange places. There are those who thank the regulars for their input. While completely ignoring the fresh ideas they themselves brought to the floor. Their own potential impact on the subject may be far greater than the safe council of those who regularly offer basic constructive advice. 

The benefits of any constructive discussion are always mutual. Provided the exchange of ideas continuously redefines the possible within the flexible framework of the already known.

Hierarchical battles for supremacy are infinitely wasteful of time and energy. The pedant, dictator and bully block all progress until they can be finally overthrown. Their egos are all that they have to offer and this is poor sustenance for any form of true creativity. Their only purpose is in building their tinpot armies. With marching bands rigidly goose-stepping across their ego's empty parade ground.

The finest teachers are those who allow others to expand to fill their own potential. Thereby increasing the sum of human knowledge by facilitation and open questioning. Rather than forging endless bottlenecks and hurdles to overcome.

The best advisers do not dictate rigid rules. Instead, they allow others to answer their own questions in a creative way. The safety net only remains in place should they stumble. Or lose their nerve while scaling the heights. While still unfettered by dragging ropes.

Criticism and negativity do not fan the spark in the kindling of human endeavour. The freedom to explore new ideas should be a universal right. We learn far more from our mistakes than we ever do by slavishly following the footsteps of those who went before. That way lies the tyranny of countless rigid rules and regulations and stifling conformity. The chronically septic appendix of religion and dogma. Which sap the energy of all human society at present. Crippling its victims and all those they lock into their self-built, universal asylum.

A strong framework is still vital to avoid repeated, easily predictable failures through ignorance of what went before. Though the accepted forms should always be flexible enough to allow our minds to soar free. To continuously push the boundaries of the possible. This is the only real way forwards without extravagant waste. To dare to be different is the root of all human creativity. Not merely for its own sake but to add to the sum of the whole. Fear of failure must be the most common and contagious of human weakness.

Decoration has its place but never at the expense of fitness for purpose. The triumph of pointless detail over function is never a useful goal. This path leads to ostentation and finicky gargoyles. Mere competence only delays damnation by faint praise. Does an ark really require a gilded figurehead?

The finest creations are those which beguile us with their staggering simplicity. Those things which make us ask why nobody thought of it before. It seems so obvious that it was unthinkable. To have dared to have tried was all that stood in its way. These things have a unique beauty which does not jar. They leave us in awe at the genius behind it.

Perhaps the opposed driver, infinite baffle manifold should be included in the list of apparent simplicity concealing true genius? The manifold offers cancellation of reaction forces and the compact application of huge driver cone area. While maintaining coherent phase at the mouth. All without raising the free air resonance of the multiple drivers and achieved with the simplest of inexpensive and commonplace board materials.

No doubt further slight improvements are possible using more rigid materials. Though at the risk of greater complexity in manufacture. Moulded concrete, for example, offers far greater mass and rigidity at the expense of intricacy in producing a suitable mould which will safely avoid voids. Reaction forces are not the only drivers of sympathetic vibration in our building structures. Cyclic air pressure waves can set walls and even concrete floors into movement. Colouring the sound by spoiling the frequency response by addition and subtraction, cancellation and delayed output and phase changes.

Who knows what changes in manifold geometry might offer? Would a suspended (ABR?) diaphragm provide improved SQ or further reach into the deep infrasonic region? An entire wall could become a suspended diaphragm. Driven by multiple manifolds for uniformity of drive and massive pumping force. Several walls might be so treated at the expense of requiring more adjacent rooms as enclosures. Though the ceiling and attic/overhead rooms could be utilised. With ducts to the rear of the wall diaphragms. New 'miracle' carbon based materials are constantly being hyped in the media. Could these become our desired low mass, ultra-lightweight and completely inflexible diaphragms?

The sub-10Hz region seem to defy accurate reproduction with low distortion at suitably high levels in comparison with the rotary subwoofer. Is there any limit to the number and size of drivers which might be brought to bear on the problem of ULF reproduction? Apart from expense, of course. Would pumping losses between the listening room and enclosure eventually inhibit the potential for true ULF output? Is there an asymmetric arrangement between listening room and enclosures which would change our present knowledge of ULF reproduction? Has anybody mathematically modelled the IB in all its variations?

Several people have tried porting huge boxes. Port noise seems to be a common feature of their efforts. The vast flares required for equally large ports have yet to be applied to the efforts I have heard of so far. We have had little feedback as to the bandwidth and phase relative to the driver cones. One imagines the maths of the common reflex enclosure are not much affected by a huge leap in scale.

The most common drivers used for IB have a rather high natural resonance. Will steady improvements in drivers bring new fare to the IB table? Or will some new technology sweep all dynamic drivers into the bin of obsolescence?

I once imagined large numbers of SEDs (Sound Emitting Diodes) embedded over the listening room's entire wall surfaces to provide truly enormous piston area. Reproducing ULF at high levels with only microscopic  linear movements per unit. All thanks to the vast total area in comparison with coned drivers.

It would probably need a wireless system to drive each SED without the near-infinite complexity of wiring each and every unit. Built-in battery power per SED unit could be "flashed" with light or an EMP to recharge all the units at intervals. A "wallpaper" type backing material with billions of printed SEDs would seem the most obvious means of applying the sound reproduction system to the walls and ceiling. Though spraying in a support/adhesive medium might be possible if SED unit orientation was irrelevant to function. A spherical expanding/contracting flexible SED shell would make this possible. All a long way off and highly dependent on developing new technology.



Mixing it.

It has been a bit quiet around here so I ought to bring things up to date: Don't get too used to the new blog format or colours. I will be playing for a while yet. Somebody messaged me that they couldn't read the text. I had some sympathy with their plight. I had been trying to adjust the transparency of the post background for days but couldn't find anything about it online. In the end I have reverted to an opaque background. Highly legible but just a tad boring compared with a translucent background. I may play with these colours some more. I have now taken the (flash) shine off the AEIB15 drivers to avoid glare. Feel free to comment if you have anything constructive to add on how you think the appearance may be improved. I have tried most of the Blogger templates without success on a slightly transparent text background. 


To the point: I was becoming ever more tired of a lack of bass impact on BluRay and Dolby Digital 5.1 films. Setting "All Bass to Mains" on my old Yamaha E800 amp/processor was robbing the IB of its full potential. The downmixing to put the bass through the front two channels compressed the dynamic range and/or discarded the LFE. The E800's SubW out socket had remained (almost) unsullied since purchase. Though I had tried connecting the SVS cylinder once or twice.

RX1602 16 Channel Mixer

When I was first playing with IBs I had bought a cheap mixer. A Behringer Eurorack Pro RX1602. It had remained in its box unused. The original idea was to use it to push the missing LFE into the system somewhere. As I had concentrated on music and automatically chose DTS, when watching films, I had left the mixer simmering on the back burner. I hated having it just sitting there unused but a long series of roundtuits had intervened in its promising career. I had no real desire to add yet another box to the music chain. So if it was used it could only be used on the subwoofers. The speaker signal must be left well alone.

Rear of RX1602 Mixer

On music IB bass can be as thunderous as desired. It can blow out windows and lay waste over a wide blast radius. 135dB+ on the SPL meter on sinewaves? No problem at all, Sir! The room and downright cowardice usually set the limit on how load I could play real music. A steady 110dB(C) on Metallica is usually my limit.

On films it was a different matter altogether. Without the LFE input I had to play everything very loud to get any real bass. It was no use just turning up the IB wick. That just made everything ponderous and heavy without increasing the dynamic peaks. Playing very loud may have produced plenty of loud bass but it was exhausting to experience a whole action film. Coming back from an errand in the kitchen the film always seemed shockingly loud. (pardon?)

CX1310 2.1 Channel Active crossover

Because it is intended primarily for music my system is run as stereo throughout the chain. All the way from from the source to the two sets of drivers in the 6' high IB manifold.

Films use dual mono L&R on the front mains fed by the E800 surround processor. For both music and films the IB bass is split off from the Front Main speaker channels with an active crossover at 80Hz. A Naim NAP180 drives the Mission 753Freedom, floor standing, main/stereo speakers from the Hi channel of the Behringer CX2310 active  crossover.

Stereo music ignores the E800 surround receiver/processor and the power it provides for the Centre and Rear speakers. So the E800 is left switched off for music.

Rear of CX1310 active crossover

How to get the missing dynamic range into my very powerful IB subwoofers system had largely eluded me since I first started. The system worked fine on music CDs. It worked well enough on DTS DVDs. Dolby Digital DVDs needed to be played too loud but were still rather gutless in the way of bass dynamics. If I wanted loud bass then so was everything else! BluRay disks were usually a bore from the bass point of view. Which may explain why I have bought so few of them. Apart form the eternal problem of rarely wanting to see a film twice within two years. With the unique exception of Hot Fuzz. Of which we never seem to tire. :-)

It may be that I need a new receiver with all the latest "bells and whistles" to maximise BluRay's audio potential. ((I hope I'm not being too technical for some of my audience here. ;-) )  However, I have absolutely no desire to buy a new receiver, with its built in obsolescence. I'm not prepared to upgrade constantly as manufacturers vie to make up silly names for their latest hyped-up formats. If I really wanted an electric room heater I'd buy a heater. Not an AV receiver.

So, finally, I have decided to drag the unused mixer into the system. It would handle both stereo and dual mono on the Front Main bass channels only depending on source. (i.e. CD Player or BDP) The only real difference is the mixing of the missing LFE into the front two channels on films.

At last I no longer need to set the E800 to "All bass to mains". It is now set to 5.1 for both Dolby and DTS. This immediately precludes the automatic compression on DD5.1. Nor is LFE discarded any more.

At this point, I have only had a chance to squeeze the mixer into the middle of the rack and swap over to the new cables. The mixer has stereo jack sockets only, for balanced operation. As I had no stock of stereo jack cables in my collection I had to go shopping for cables first.

Once I had everything safely in place, "Expendables" on BD was my first test subject. It had sounded strong and powerful on a hired DVD. But fell flat on the BluRay disk which I had bought my wife for Christmas. She loves "things blowing up" so the disk seemed like a good way to feed this unusual taste in films. On the BD disk I had played the same scenes repeatedly without the mixer but it just would not come to life at any level. I kept wanting to turn the overall volume down. Not further up!

Despite the very rudimentary mixer set-up I was getting intermittent red flashes on the BFD bars. That was a new experience! Instead of peaking at 103dB on my test scene (with over-loud dialogue) I hit 109.7dB(C) on the Galaxy 140 SPL meter on the very first trial. 6dB is not to be sniffed at when one is hungry for more impact! More importantly this was at far more comfortable overall listening levels.

The mixer LED bars hardly showed any signal so I still have some settings to play with. The EP2500 power amp on the IB was showing steady orange lights but no red for clipping. No sign of cone excursion on the eight 15" drivers so there's plenty in reserve if I can only tease it out.

Here's a diagram of what the basic system looks like so far: (ignoring sources of course)

Don't ask me why I drew it upside down, compared with reality, but that's just me. (PhotoFiltre drawing and text)

Note that the mixer only intervenes in the front mains/stereo speaker, bass channels coming from the CX2310 active crossover. So it has no effect on the Stereo/ Front Main speakers' SQ. The Missions go down to 40hz at full power. So an 80Hz crossover suits them fine. On full range material they are supposed to be good for 110dB. With an 80Hz crossover they can probably go louder as an easier load on their Naim NAP180 amplifier.

Just as before, not switching on the E800 has no effect on music. The mixer must be left on because it passes the stereo channels onwards to the big EP2500 amp which powers the IB subwoofer drivers.

Behringer Feedback Destroyer two channel parametric filter.

I have a choice over BFD input levels (domestic or pro) but haven't examined this possibility in conjunction with the mixer yet. I'd like a lot more headroom before the red lights come on! Later on. I found that the push button selection was the answer to removing the red clipping bars on the BFD.

Rear of BFD.

With so many different level controls in the chain the possibilities are endless. On films the Naim preamp no longer seems to have any effect on bass levels until well advanced. (far higher than I would ever listen to music) The E800 volume control affects everything now. Before the mixer was inserted it had no effect on the subwoofers. I shall have to play around with level settings to maximise dynamic range without increasing the dialogue and ordinary sound effects and film music levels. It will be a real pleasure to enjoy shots and explosions at thunderous levels without actually having to listen at reference level.

The real question is why did I wait so long? My old SVS cylinder used to manage 107dB(C) peaks on the Galaxy SPL meter. It was rare indeed that I ever saw the same peaks on the IB on films.

More details will follow when I have had a chance to play with level controls. Pictures too, when I have tidied up the "knitting" behind the stack of boxes in the rack. You have no idea what is involved in a rack tidying session with 10 boxes vertically arranged! Many of the cables are yards long and coiled up with zip ties (tie-wraps) keeping the weight off the plugs and sockets. I may even pull the whole thing out from the wall once the mains is safely switched off. Fortunately most of the XLR signal plugs are marked with Dymo labels. Maintaining L&R between boxes is always a problem without labels.

Front and back of the system rack. (after tidying up!) 
Stop laughing at the back! :-)

As all the mains sockets are on the right and all the wall sockets on the left I dressed each mains cable along the horizontal bars and tied them to the rails with several zip ties. I try to avoid tying more than one cable in at a time. There are always reasons to remove one box or cable and snipping and replacing multiple ties holding several cables quickly become a bore.  Hum has never been a problem but having the mains cables at right angles to the signal cables is probably good practice. 

My usual musical instrument and cable shop only has minimum 2 metre lengths on display. I could do with 1 metre (3') or even less, for most of the connections behind the three Behringer boxes. Though not all. Lots of longer cables go off to the big IB amp, the Front speakers and the LCD TV. 

The Fortec Star Passion HD satellite receiver has finally lost its place in the rack and will go under the TV once I have a coax coupler to extend the cable from the dishes outside. Or, more accurately, from the DiSEqC box which the dishes feed into.

RX, CX & BFD stack. Mixer, Crossover and Subwoofer Equaliser.

My rack is just the right width for these boxes but I prefer zip ties around the tubular frame uprights to hold them in place. I can guarantee that if I drilled the rack I would want to move the boxes up or down within a week! Not fixing them to the rack means the boxes slide backwards when turning them on or off with their press switches. These Behringer boxes should always be turned on first and turned off last to avoid loud thumps in the speakers and subs. Completely unforgivable these days, if you ask me.
I have yet to try setting the Front Main speakers to Small for films. With the former system I had no choice. The bass for the IBs was split from the Front speaker channels. With the mixer in place I now have a choice. Though I shall have to be careful about not cascading crossovers.

A quick test of the "Expendables" motorcycle scene (on BD) was very satisfactory with Mains still set to Large. With thunderous bass at appropriate moments but without any "heaviness" in between. Realism above all else. I'll happily swap 10dB of potential headroom for 3dB of actual dynamic range. A dull roar has no impact (at all) compared with a sudden loud shock from nowhere. Which is why heavy metal is so boring for some listeners. Everything is at the same level without any contrast. Metallica excluded. They know how to build to a crescendo from a quiet riff.

The BFD wants to stay with domestic input level settings. Switching it to Pro settings produced two vertical row of bars on almost no bass. I'm using only a 1/4 of available level on the mixer L&R Main Out knobs. The yellow LEDS on the EP2500 are about right with only 1/4 setting on the twin control knobs. Bass sounds quick, deep and absolutely effortless. "Brutal" is my preferred term for the realism of IB bass but I may have overused it just a tad.

A quick check of the Bass Outlaws CD provided massive bass when called for. There seems to be no limit as to how loud it will go if desired. Not that one wants to swamp the speakers. Balance in all things. It also saves destroying the house. The rattles from the walls, floor, windows and other items  sometimes make me wish I had a sealed concrete cellar to play in.

Following the recent changes I have finally fitted trunking across floor in front of the double doors. In doing so I managed to pull the bananas out of the Naim power amp. Then I discovered that one set of IB drivers wasn't working. I had been stripping out the Component cables to the TV and HDMI to the satellite receiver and had dislodged an XLR plug. More fiddling with the help of a pencil torch and all was well again. 

I was just testing my mixer controls with organ music. The bass on Guillou's, "Cesar Franck Complete Organ Works" is shockingly good. (Rather oddly, I have read critical comments on both Guillou and Franck on YouTube organ videos)  This double CD is a DDD recording: 92292 from Brilliant 

The detail,  texture and weight are in a class of their own. Franck is easily my favourite organ music composer and this my favourite CD. I used to prefer Vierne but was never that keen on Bach. Though he does have some very pretty tunes. I have access to a large, free collection of CDs at the Odense Music library. My ISP also offers loads of free downloads of organ music CDs. 

My vinyl collection of organ LPs is also steadily increasing thanks to occasional finds at charity shops. I haven't counted my organ LPs for a while but the numbers must be close to 60 by now. Few of them remotely match the best CD's for bass. Though many LPs have a uniquely "live" and emotional quality which CD never matches. Perhaps I should repeat my SQ listening test comparisons between the CD63SE and the LX70A on Franck instead of Clannad? :-)


I noticed something interesting while out on my daily bike rides in the recent days of thick mist. The low frequencies were heard earlier and much later as vehicles approached and receded respectively. The sound also carried far better than normal. So I was made aware of a vehicle coming long before normal. Conversely I had to suffer their racket for long after they had disappeared into the mist. 

My guess would be an inversion layer. One which stopped the low frequencies from escaping vertically to be scattered and absorbed in the atmosphere. Low frequency (long wave) sounds are known to travel much further than higher frequencies. Large animals use deep sounds to communicate at great distances. Particularly in the forests where higher frequencies would be rapidly absorbed by the intervening twigs and leaves. 

I wondered at the time whether the inversion layer was performing as an acoustic boundary (layer). Further augmenting the low frequencies by providing additional boundary gain. This strange acoustic effect was certainly very noticeable but was completely absent after the mist had lifted several days later. It may be that forests provide similar conditions. The bare trunks of the trees would offer a clearer pathway for lower frequencies. While the dense mass of branches, just above, would form a partial barrier to vertical absorption. It may be that a form of low absorption, transmission line or wave guide is involved. Further reinforcing the effect at even greater distances.  

Meanwhile, back at the ranch:

A few more films later and I am still very happy that I added the mixer to get "real" 5.1. I still haven't tried setting the Fronts to Small but I have the 80Hz active crossover which probably amounts to the same thing. I'm still puzzling over this one. While more bass may be sent to the subwoofer channels the bass is already in the Front Main channels. Which are then split at 80Hz. Probably a "swings and roundabouts" situation. I may have a play if I have a boring few hours to kill.

BTW: Film music is also much improved with new bounce and drive. Maiden Heist has a catchy number at the beginning of the credits. It sounded great wound well up. Though not the sort of music I would ever sit down and listen to seriously.

Well, we have just watched "Jonah Hex" at spirited levels. A total bass orgy! I only put the SPL meter on towards the end and immediately hit 117.5dB(C) on Max hold! Absolutely amazing! The baffle wall was shaking like a wall really shouldn't. The shocks through the floor were downright nasty. My CD storage was threatening to throw the entire contents onto the floor. It will have to be moved. And the wall clock too! :-)

Later, I checked the speaker/subwoofer level calibration using The Calibrator DVD. I discovered that the IB was running about 5dB "hot" on the pink noise test tracks. I have reduced this now to avoid hitting red lights too often on the BFD!


Here's a great YT video about an audio/HT system with an IB containing four 18" Fi IB318 drivers built into a solid block wall: Try not to drool on your keyboard at the sight of four 18"s arranged vertically. ;-)

Click on any image for an enlargement. Back click to return to the text.