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.
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.
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?)
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.
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.
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.
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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