Another post to AVS.

 OOOH

I once visited a home with a tiny, heavily-furnished home where I could clearly hear a person playing the piano in the next room. I was completely mistaken about the piano. A pair of Quad ESL57s had been inserted somehow at random into an even tinier room, stuffed with furniture and sounded utterly convincing. The limited number of other electrostatics I have heard since then have not made convincing music. All draw attention to themselves in one way or another. Boom tizz-tizz. Boom tizz-tizz.

Claiming that only small subwoofer cones work is to ignore both physics and economics. They are horribly uneconomical to make their cone area larger by using a greater quantity. You can make no useful sound with a postcard until you stick lots of them on a large board. Only then can you move enough air to become convincing at lower frequencies. A postcard needs an excursion of several yards to produce low notes. Even if it were remotely possible the sound would be horrendous and it would take literally ages to move that far! We just don't have that much time for that much excursion every time we need to hear something h_a_a_a_p_p_p_e_n.... wooof.

A large set of 15" or 18" cones can reproduce convincing bass without any visible movement. So they need no time [AT ALL] to get nowhere fast. Dynamics and VLF to die for! Hit a large sheet of metal with a hammer and it shows no excursion either. Hit a shipping container with a even larger hammer and it shows no excursion. Yet both sound strangely LOUD and convincing all by themselves. Don't they? I wonder why? Ear defenders may be considered important for this thought experiment. Though closed back headphones will do at a pinch.

The problem with audio reproduction is the desperate [almost completely futile] attempt to match reality at all frequencies. And, to do so in a realistic manner where the dynamics are also reproduced accurately. Nobody suggests anyone sits and "enjoys" a steady 120dB. Pardon? But surely it is a useful momentary target if accurate [real to life] reproduction is the goal? I'd love to see your 10" subwoofer cone matching the little waif beating on the girl's marching band, bass drum! Now that would be something else and would probably require excessive intoxicants or narcotics to become remotely convincing. 

Back to the OP: Learn to adjust your subwoofer down in volume to match your speakers. Hopefully there will not be a huge frequency gap or overlap between them. Move the subwoofer around the room to minimize those nasty unnatural booms made by the room. Well away from the walls and corners [and you] is often best but not usually the loudest. LOUD is only for teenage parties because they have absolutely nothing useful to say to each other.

Learn to differentiate between miserably poor upper bass humps and better quality bass from a better subwoofer. Then just keep adding to the quantity and quality of your subwoofers until you grow old and opinionated. Like me. Keep turning them all down until you can no longer hear the subwoofers but only the [more realistic] music. At some point on your very long journey you will learn to grow very afraid of that little girl walloping that big bass drum. She was your terrifying first step and your final goal on your exhausting journey towards musical realism. Your constant reality check, if you like.

BTW: Some really big, ugly blokes can pound on the bass drum too. But you'll have to wait for completely new technology to get even close to that "alternative" reality. But above all: Remember that 10" woofers are only for 10" drums.

WOOOO-HOOOO?

An ode to real bass:

OOOO-OOOO

When I first discovered subwoofers I could not believe my ears.
The authority they brought to all music was stunning.

Each improvement in subwoofer quality should be clearly heard as moving closer to reality.
Those who cling to bookshelf speakers without using a subwoofer obviously haven't listened to real music.
I am not talking about film bass here but the bass which supports music as a solid foundation.
Bass provides the scaffolding from which the higher notes are hung,
And delicately arranged and endlessly re-arranged.
Without the foundation and scaffolding it all collapses into a mere jangle-jingle.  

The subwoofer must be well integrated with the speakers and the room.
Ideally this requires something like REW to at least find a nice balance.
The ears are easily fooled and highly susceptible to suggestion.
How many of us have listened to a whole piece without realizing something wasn't even turned on?

As subwoofer quality and cone area increase so the cone excursion falls.
You can pump bass artificially hard.
Or you can waft it effortlessly into terrifying being.
I prefer the latter.
There is no substitute for sheer cone area moving a couple of thou' at 120dB!

There are no small elephants which can bellow over 7 miles from the herd. 
Nor small double basses. Nor 10" fog horns.
No bijou whale which can circle the entire globe with his gigantic acoustic power.
A contra-bass anything does not come in a shiny, veneered, shoe box.

A large drum or instrument sounding board produces infrasonics. [Sub 20Hz]
Which small subwoofers have never felt let alone tried to reproduce with authority.
You may never have heard the great organ pipes inter-playing at the very limits of human perception.
The composers obviously felt it necessary to achieve that precise effect by writing down all the pedal notes.
They could only have understood them from listening to real cathedral organs with 32' ranks.
You certainly won't hear anything like this very strange reality [at home] until you have acres of bass cone area.

Our world abounds in natural infrasonics.
They can be felt and heard in any large space:
Supermarket, concert hall, factory or train station.
Try standing in a corner of one of these great spaces.
If you can stand the crushing acoustic pressure!
Bass instruments have inspired man to march to war, or to dance wildly.
They have moved and terrified him with large drums and bigger horns for countless millennia!
We have a species memory for bass written into our genes.

When did you last stand in dumbstruck awe as a mere slip of girl beats the hell out of the bass drum as the band passes in step?
Did you not flinch at that raw power in your chest and stomach and paralyzed mind?
And you still think you can listen to realistic music through a 10" speaker?

OOOO-OOOO

4 x 15" OB part 2.

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After some trial positioning of the spare half of the original IB manifold, behind the Right Main speaker, I took the electric jigsaw to the box again. This reduced it's size to the minimum of 42cm x 51cm x 85cm. Used in the 'tall' vertical format this will house the four 15" drivers safely with some meat still left around the driver holes. The OB baffle 'box' ended up as an open U-shape of still very heavy, laminated 36mm Baltic birch plywood throughout. Having no top allowed easy access for fitting the drivers and wiring them in series-parallel for 8 Ohms.

For testing I just placed a piece of ply on top of the box to close it off and pushed the open back against the sloping ceiling. This left two, large triangular vents to allow very free air flow at the rear. I re-fitted one length of the 10mm bracing studding with large load spreading washers to stop the U-channel from flexing to driver reaction loads. There was no need to seal the bottom as it rests on the carpeted floor of the stage.

Wiring the four x 15" OB to the EP2500 with the channel 2 control at 12 o'clock was completely underwhelming. I had to increase the setting on the Behringer's control knob considerably to make the output suitably audible above the IB. I will have to pull the cable off again to double check that I have all the drivers moving outwards with a 9V battery. I remembered to do it on the IB but completely forgot about checking the OB. [It proved to be correctly wired as expected.] On Netflix films there was a very subtle increase in bass impact. Muting the OB proved that the IB was still doing most of the heavy bass lifting.

Further increasing the EP2500 control to '2pm' and then '3pm' brought the OB bass up for an organ music trial. Suddenly I could hear very natural organ bass. I muted the IB repeatedly to better hear what the OB was contributing. This was more like it! The big pipes sounded suitably "breathy" and very deep. Still no BFD filters at all. This would require I fire up REW to get some idea of the raw frequency response. From long experience with them working in an IB I know the older AEIB15s don't do serious infrasonic bass. At least, not without heavy boost. That doesn't mean they can't easily reach 30Hz with plenty of "welly" to help the IB along and hopefully provide a bit more impact on drums and bass.

Playing a variety of  music I gradually brought down the levels of both OB and IB to avoid a rather detached, "heavy-footed" effect. While Netflix benefited from rather more bass for more impact. The OB box lid was given a seating of strips of foam to kill vibration and to provide a better seal. I shall provide a second layer to bring the lid up to 36mm as soon as I source some more Baltic plywood. It is important to trap one layer of 18mm plywood between the sides to reduce flexure in the manifold sides. REW testing proved a central shelf to be well worthwhile in a manifold even when a solid 36mm top and bottom were already in place.

The only way to get more impact is probably going to need a higher roll off point on the the OB. Since the Onkyo TX-NR818 cheats and connects both subwoofer sockets internally nothing can be done about a separate roll off point for only one sub. So it will require raising the roll off point on the Main speakers to push [both] subwoofers higher in frequency. With the faster roll-off of the newer drivers in the IB this will not affect it much. The question is whether I really want a higher cut off point on the 40Hz[-3dB] floor-standing, Mission 753F Main speakers. Having revisited the speaker setting menus on the Onkyo it seems there is very little individual adjustment available. LFE cut-off can only be set as high as 120Hz. This will have no effect on "ordinary" bass signals. Only on LFE.

Raising the "crossover" frequencies of the speakers just made the sound rather thin. So I reset the Mains and Centre to 80Hz with surrounds still at 120hz. Listening to Celtic Circle 2 I noticed a considerable increase in impact on the large drum on one track. It took me quite by surprise after probably 100s of hearings.

Overall I think this four x 15" [manifold] OB more worthwhile than any previous attempt to use the older, plastic coned drivers. I am still muddling over how the OB might be allowed to play much higher frequencies as well. I can't use the right Main signal because that is rolled of below 80hz. Subwoofer-out from the Onkyo Rx can't be independently adjusted and [I assume] will depend entirely on the crossover setting of the Main speakers.

Still having made no further adjustments I am noticing slightly greater impact from the OB on bass drums and bass effects. The effect is usually quite subtle.

Click on any image for an enlargement.

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