Dual subs below 80Hz- what should I be hearing?

[darkmoebius]

What does it sound like when running strictly a subwoofer or two below 80Hz?

And what should I listen for when adjusting phase?

I finally got a decent amp for my pair of passive subs, a Samson Servo 550 (275wpc). It's a pro/live amp used in clubs/bars/etc. See My System here - it's strictly 2 channel music-only.

Anyway, I feed my subs via a Paradigm X-30 active subwoofer crossover with line-level inputs.

I am currently feeding the X-30 directly from my cd players "fixed" outputs and my monoblock tube amps from it's "variable" outs while rebuilding my passive transformer volume control.

Anyway, last night while playing asorted jazz, classical, and rock I would intermittently turn the volume down on my main speakers to listen strictly to the subs output.

I expected to hear distinct, clear-cut, drum strikes or the clean resonance of standup bass strings, but that isn't what I got. Everything was rather muted in a undefined way. It certainly fleshed things out when mixed in with the mains speakers, but I expected more attack, I guess.

The best description would be a line that an audio reviewer once used - the subs recreate the trailing edge of a note rather than the leading edge. More resonsce and decay than strike.

I've tried varying the x-o frequency from ~60Hz-120Hz.

Does this seem right?

[johninCR]

It sounds right to me. What's missing is the higher harmonics that are part of each note and other higher frequency content of the bass notes. The higher frequency stuff is needed to sound right. I don't think even very low organ notes will sound right with only the sub.

How does it sound going the other way? Mains with sub to mains alone. What you should pick up is only a richer fuller sound with the subs playing and never be able to localize their position.

[GM]

Greets!

His description is as good as any. Mostly you hear room modes and any very audible group delay below the XO roll off. Since the lower the frequency, the wider its BW, it's the HF portion of the system that defines how much 'attack' the LF has, assuming it's not clipping the leading transients, a more common problem than most folks realize.

GM

[CBFryman]

as already said, even low organ notes (which can be mid 20's ) contain harmonics well above what you would think. Acoustic Bass Guitar, even kick drums. the only thing that shoudl sound right is 808 bass notes (electornically generated "boom" notes in rap and R&B)

[darkmoebius]

Wow, what a relief!

Everything sounds right when they are integrated, it's just that I am used to seeing midfi subwoofer drivers that are flapping like the wind. These low-excursion Seas 10" aluminum sub drivers barely move at all, it is almost impercetible.

I don't think even very low organ notes will sound right with only the sub

Funny that you should mention that, I ran upstairs to throw on Bach's "Fantasia in G major, BMV 572" with Simon Preston at the wheel of organ at The Monestary Churc of Kreuzberg, Bonn. Track 5 in Fantasia - Lentement takes a slow walk down the lower registers of the massive organ. There asre some sustained notes that dig fairly deep.

It's amazing the current it takes on the part of an amplifier to handle sustained notes like that. The Servo 550 had it's clipping lights fickering during those notes and the volume output was not all that loud. In fact, it was surprisingly low, yet more than enough to charge the room.

How does it sound going the other way? Mains with sub to mains alone.

Anemic and shrill in comparison(that's an exaggeration). Oddly, I've always thought the 6 ft. tall Bens(36kHz-40z) provide clean, rich, bass - but, with the subs running now, there's no comparison. They flesh to the low and mid-bass. Everything seems much more "right" now and it doesn't take much output for that.

One thing I've noticed, is that I listen to the mains at a much lower volume now. I used to run them at full-tilt or -6dB, now it is in the -13 to -20dB range on my volume control. Granted, I'm using a 7 wpc SET amp, but on 98+dB speakers that's fairly loud. I always felt that level was necessary to get a good tactile sense of the body of instruments. Not anymore, it just seems like unnecessary excess.

Anyway, I feel a lot better now knowing that things are working as they should. Now, I just have to tackle the room modes that get excited.

Thanks guys

[CBFryman]

well we are trying to reproduce these sounds with a box 14"x 14" by 5" conected to another box that is maybe 4-5cuft tops in most situations (execpt for extreme home audio setups where the enitre floor of a 15x20 room is the enclosure) though EMF with only a few hundred watts in most cases.

and then you look at not only at the pipe length and diameter of the organ which is playing this not but also they take huge blowers that store pressure and valves that release on key. Back in the old days there where whole rooms dedicated to guys operating big foot pumps like what comes with thoes cheap rafts (only bigger) just to store up the air. so it is expected that an amp may be stressing to flow maybe 15a of current 30-40v...

todays "electronic" organs dont even come near to the impression of a TRUE pipe organ. unless it is a pipe organ like the local prespeterian chirch has....in a room that is probably 50'X150' completely empty the first 20-30' are all speakers and amp enclosures 10' off the ground and 10' wide in both corners with the stage/pool pit/organ keys in the middle (im not prespeterian but ive been in the church many a times and even gone up stairs into the enclsore/amp room)

each side consists of dual 20" paper coned drives in massive ported enclosures but they are only capeable of 5mm or so oneway movement. however when you have that much cone area in a large ported enclosre you dont need a whole lot of movement. each is driven by a 50w amp. then you have dual 10" paper coned drivers, same deal with the excursion only they are sealed, then each has a large horn driver, these are driven off of a dual chanel 40w amp (20w per chanel)

then in the rear (because bass cannot be localized but midbass and trebble can, and if youve ever heard a real pipr organ though you can tell where it comes from the sound isnt generalized all too much) you have the dual 10" drivers and hornes up on the ceiling.

now it is by no means loud, however it playes thoes digitally recorded pipe organ tones very clearly and with deep responce. a VERY flat responce and its is quite hard to tell the differnce.

then there is another church (forget what dinomnation, luthren maybe) which has a REAL pipe organ...if i remember correctly (fro ma 6th grade feild trip) its largest pipe is 20' long and 6' in diameter and its lowest note possible is a C (?) in the first octave.


ok that was way of topic...lol

[johninCR]

Earth to CB, I'll crank up the homing beacon so you can land safely.

[CBFryman]

[sam9]

And with drums you have the "attack" when the stick first hits the membrane. If you close your eyes and just listen for to each impact you might be able to notice that there is a sharp initial sound that is brief and certainly nor a deep bass sound.


Try something with a lot of electronic music. Vengelis, Tomita etc. I bet you find the bandwidth of some sounds is much narrower. I think . . .