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. ;-)

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