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Author Topic: where to find/how to make a REAL SUBwoofer?  (Read 30218 times)

Antone Atmarama Bajor

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Re: where to find/how to make a REAL SUBwoofer?
« Reply #20 on: September 22, 2006, 05:37:27 PM »

     And you can prepare cancelation energy for room modes with cancelation subs too.

    Depending on how crazy you want to get.

Antone-
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Ivan Beaver

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Re: where to find/how to make a REAL SUBwoofer?
« Reply #21 on: September 22, 2006, 08:57:01 PM »

So if you do not like the way a flat response sounds as measured with an RTA (the wrong tool BTW), then why are you interested in his measurement, at least as taken with a RTA.

There are much better-more accurate ways to measure response.  But indoors it gets to be a whole different problem of what is "right".
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For every complicated question-there is a simple- easy to understand WRONG answer.

Can I have some more talent in the monitors--PLEASE?

Ivan Beaver
dB Audio & Video Inc.
Danley Sound Labs

Michael_Elliston¶

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Re: where to find/how to make a REAL SUBwoofer?
« Reply #22 on: September 23, 2006, 09:11:46 PM »

Mark "Bass Pig" Weiss wrote on Fri, 22 September 2006 11:17

Most, if not all of the harmonic noise was caused by building structure re-radiation (more like distress noise). The ZR18s are extremely linear and were being driven to a fraction of their rated power. There wasn't much audible sound, except a very painful pressure on the ears (despite plugs) akin to what one unaccustomed to deep water feels when diving into the deep end of a swimming pool, and difficulty breathing while the subsonic signal was at high amplitudes.
I'm certain that an RTA would show only information present in the 16Hz band, and very little else, unless the microphone were near the ceiling or wall, in which case rattling would be picked up.
I don't know of any Meyer subs that get down to 7Hz or are even spec'd to those ranges. The only sub I know that is spec'd to 10 Hz is the Wilson XS, which uses Aura drivers which have exactly half the excursion capability of the ZR18s.


Hi mark-that was the problem. Meyersound simply used their regular double 18"s with ports plugged to get some <10hz output at only 108dB.24 double 18"s I think,outdoors.

Why not use a small concrete chamber(with test subject inside),with a flow modulator,If one is actually going to test something!

Google video has the mythbusters brown note video.

Cheers
Mike.e
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Mark "Bass Pig" Weiss

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Re: where to find/how to make a REAL SUBwoofer?
« Reply #23 on: September 24, 2006, 03:20:39 AM »

And that's a problem--conventional 18" drivers are useless at producing anything but harmonic distortion below 30Hz. Same problem with every commercial driver that I have applied to the task over the years. Only the new long-throw drivers with specially built suspensions produce any meaningful output in my tests. That's why the ZR18s broke new ground in my quest for subsonic bass. I just wanted to get clean organ pedal tones at very high volume, but ended up getting a demolition machine in the process.

It's more fun to achieve "brown notes" with technology, rather than by using non-audio methods, as you described. I am motivated by those types of challenges. Anyone can build a valve and a concrete chamber, but build a subwoofer that can also play music and that's heaven!

I had a BBQ party last Sunday and some very wealthy audiophiles were in attendance. None of them were anxious to see this system go over "club levels" and as such, I never got beyond illuminating "signal present" LEDs on my QSC PL amplifiers. But later on, one of the audiophile guys, a gentleman responsible for 'poisioning' me into becoming this Bass Pig some 30 years ago with an exposure to his big system, informed me that the demo today had a very effective laxative effect. Smile

Now I have a new sonic demonstration weapon in my arsenal: A hand-restored Telarc "1812 Overture" digital recording, in which I restored all the badly-clipped cannon shots to their full amplitude. Then I have the audacity to run that through the dbx 4bx Expander with Impact Restoration, for just a tad more impact than the original. Smile I won't play that for people without signing and indemnity waiver.

As for RTAs, relatively limited value, in my experience. This room has a big problem with bass absorbtion and cancellation, which is why the system grew so big over the years. The place is a black hole for bass. An ordinary set of stereo speakers in here sound really bad, with no bottom end. The room doesn't get excited and hence it seems like it's playing in a vacuum.

robwells

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Re: where to find/how to make a REAL SUBwoofer?
« Reply #24 on: September 25, 2006, 02:58:50 PM »

Ivan Beaver wrote on Sat, 23 September 2006 01:57

So if you do not like the way a flat response sounds as measured with an RTA (the wrong tool BTW), then why are you interested in his measurement, at least as taken with a RTA.

There are much better-more accurate ways to measure response.  But indoors it gets to be a whole different problem of what is "right".


Hi Ivan,

As I understand it a system has to measure fairly flat anechoic. When you put it in a room (esp a small home setup) the response changes dramatically. I have the master handbook of acoustics, and a couple other books which all reference the need for a room curve to lower the highs compared to the lows. Something to do with an imbalance between the reflected levels of bass vs treble. I've tried the recommended curves and they don't sound too great - usually make the sound too bass heavy / and muddy in the mids.

Thats why I'd have liked to have seen a 'real world' rta curve of the big system - to see if the highs were much lower than the bass.

If you have the time I'd love for you to pm me the much better / more accurate way to set up my system. I have ETF and the 24dB/oct version of trueRTA.

Thanks,

Rob.




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Ivan Beaver

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Re: where to find/how to make a REAL SUBwoofer?
« Reply #25 on: September 25, 2006, 08:59:43 PM »

Depending on what curves you are looking at, they often assume a particular room size and relative RT60 and acoustical treatment.  As in a theatre.
When those variables change, the curve is not good.  You also have to take into account the mic position (both from the source and elevation), for example.  Is it ground plane or up on a stand?
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For every complicated question-there is a simple- easy to understand WRONG answer.

Can I have some more talent in the monitors--PLEASE?

Ivan Beaver
dB Audio & Video Inc.
Danley Sound Labs

robwells

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Re: where to find/how to make a REAL SUBwoofer?
« Reply #26 on: September 26, 2006, 02:01:34 AM »

Hi Ivan,

I'm about to leave for work, so if you don't mind I'll pm you later as this seems to be going off topic - Unless everyone thinks it's useful to keep on this thread.

Thanks,

Rob.

ps . The mic is on a stand, at listening position. Room treatments are planned but not built yet.
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Kerry Stansbury

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Re: where to find/how to make a REAL SUBwoofer?
« Reply #27 on: October 06, 2006, 10:13:47 PM »

I don't know where you came up with the Aura having half the excursion capabilities of the Bassmaxx ZR18! The ZR18 has an Xmax of 17mm, The Aura NRT18-8 has an Xmax of 18mm. Please check your facts before posting them.
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Rolling Thunder

Mark "Bass Pig" Weiss

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Re: where to find/how to make a REAL SUBwoofer?
« Reply #28 on: October 08, 2006, 10:13:20 PM »

Kerry Stansbury wrote on Fri, 06 October 2006 22:13

I don't know where you came up with the Aura having half the excursion capabilities of the Bassmaxx ZR18! The ZR18 has an Xmax of 17mm, The Aura NRT18-8 has an Xmax of 18mm. Please check your facts before posting them.



I was referencing the maximum peak to peak excursion.

(1.5" for the Aura, 3" for the Bassmaxx)

The units I have here have certain improvements done to the design. You may have an old spec from a year ago.

Video clip of the ZR18 being driven to 3" excursion at 20Hz in free air, near the end of this video (mistitled "CGN-1808"):
http://www.youtube.com/watch?v=2BiF0ljPzvw


The driver design has undergone many changes in the past year. One of them was the extention of the overhang and design changes to the motor and suspension. Since this driver is in almost constant revision, the specs have been a moving target.

Kerry Stansbury

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Re: where to find/how to make a REAL SUBwoofer?
« Reply #29 on: October 09, 2006, 09:55:44 PM »

Just for your info, The Aura's peak to peak maximum is 2". I wonder how much of an advantage the extra inch is since it's so far past xmax. I will have to save my pennies so I can buy one to compare to my Aura.
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Rolling Thunder
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