I just purchased an RTA program that allows analysis down to 10Hz. The previous RTA software I had had a lower limit of 20Hz. Since I could now see what exactly was going on in the region between 10Hz and 20Hz, I decided to see what improvements I could make to my four JBL 18" subs. I did modifications to the electronic crossover's extreme low end active EQ frequency and slope, lowering it from 20Hz to 10Hz and increasing the "Q" of the circuit so it would be more selective.

The result? Well, using pink noise and the spectrum analyzer, and measuring at the listening position, at 10Hz the in-room response is absolutely dead flat relative to the higher frequencies! Not 10db down, not 3db down, but dead flat. I don't know what the actual lower limit is since the RTA software only goes down to 10Hz, but I shudder to think

How does it sound? Well.... I played some organ music I recorded of an organ that has a genuine 32 foot rank of pipes which yields a 16Hz lowest pitch, with "beat" frequencies of even lower pitch. The difference was remarkable. I didn't expect that opening up the low end from just below 20Hz down to below 10Hz would make that much difference - I was wrong, it makes a huge difference.

This could get scary

[This message has been edited by soundhound (edited August 14, 2003).]

Wrong, Bass Breath, this is ALREADY scary!

I happened to go over to Hound's place about an hour after he finished tweaking his system and heard that same organ recording.

This wasn't bass. This was a Full Body Massage. You could literally feel the individual pulses of the soundwaves at that frequency. And I suuuure hope the contractors did a good job building Hound's studio because those subwoofers definitely were moving the foundations around.

The most surprising thing is that this wasn't obnoxious, overstated or pugnacious bass at all. It was just suddenly THERE when that bass-crazy organist opened up the 32-foot ranks.

I heard this system MANY times before today's tweak and I can say that this latest refinement has made a HUGE difference in the last time I heard these bass demos. And it sounded pretty damned great before.

Too bad Peter missed this latest innovation when he made the Outlaw field trip to Soundhound's studio.

Yipes.

I assume you're talking about an active high pass filter. Adjusting it lower and to a higher Q not only extended the low end response, but boosted it at the HP filter's corner.

My sealed subs are flat (in room) to 10 Hz. (also as low as I have tones to chart), but they can't take too much power at that point. It's too cool to feed a 10 Hz. tone into them and watch the cones move at 10 cycles per second while you only feel it and hear nothing.

I KNEW those dual 18 beasts could be flat to 10 Hz., corner loaded, in room!

Try DareDevil. I wasn't too fond of the flick, but in the first chapter at about 4:40 there is about 5 seconds of sub-sonic tone that actually moved my floor like the ocean.

Yeah...many times I've pictured the maniac Soundhound with 4-18s. It's a beautiful thing.

Yes, it is a beautiful thing! The filter was modified as you imagined. The problem before was that since my RTA software only went down to 20Hz, I had no reliable method to see what was actually going on down below that frequency. I did some speaker only, without crossover measurements, and modified the crossover to accommodate what the speakers needed. Seeing that flat line at 10Hz on the RTA and going strong to gawd knows how low is, FUN!. I think I would run into room structural limitations before I ran out of speaker SPL capabilities!

[This message has been edited by soundhound (edited August 14, 2003).]

I do not understand why the software has a lower frequency limit unless the software creator chose to place a limit on the low frequency limit so as to decrease the response/update time. I would have expected a user option to set a lower limit, if one is desired, at the expense of response/update time.

I have a set of speakers that have response down to DC. I put in a big DC voltage and the (woofer) speaker responed by moving outward and then giving off a lot of smoke for a while. After that, it (the woofer) responed by just ignoring the input signal.

Paul

The organ recording that I used in my original post is by far the most impressive bass-wise that I have ever encountered. It is what results when you combine 3 spaced omni-directional (pressure) micorphones, a huge stone church, and an organist who loves bass

I have made an edited version of this track and encoded it into mp3 at the highest bit rate of 320kb/sec from within ProTools using their excellent encoding algorhythm, and posted it here:

http://home.earthlink.net/~soundhound/Organ.mp3

The bass on this track goes well below 20Hz - well below. It will give your subs a workout, and if they do venture into the sub-20Hz regions, you're in for a real room rattling experience. Have fun


[This message has been edited by soundhound (edited August 16, 2003).]

Was the software you bought some fancy schmancy pro stuff? I've been pondering picking up a copy of TrueRTA from True Audio. Any of you have any experience with it?

[This message has been edited by Ellen (edited August 16, 2003).]

Ellen:

It is TrueRTA that Hound is using.

It was TrueRTA that I was using.....echo.....echo.....echo.....

It seems to be pretty darned good. For analysis with 1/24th octave resolution you need the $99.99 version, but I think it's money very well spent. My only wish list would be for it to have a comparison function where you could subtract one set of measurements from another, and also that you could save the screenshot as-is so you could look at the graph later. It does have an "export" function but this is a listing of numbers for each frequency and the level at that point. Not very easy to compare with other data, especially if the absolute level is lower or higher between the two charts

[This message has been edited by soundhound (edited August 16, 2003).]

hound...you are my idle..'nuff said

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Play it LoUd!!