quote: Mike Blakesley

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I like the Peavey subs fine and we've never had problems with them but if I had it to do over again, would probably go with JBL.

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quote: Richard Hamilton

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because?????

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Because when we first bought the system, we got three different quotes. The top-end quote had all JBL speakers and QSC amps. The middle system had Peavey speakers and Peavey amps. (This was in '92.) The lowest-priced system had similar Peavey equipment but was a center-surround system. The middle-range system seemed a good compromise. Last winter we replaced the Peavey amps (because a couple of them had started to give us trouble) with QSCs, replaced the DTS with a CP650, and plan to upgrade the speakers eventually.

If I had it to do over, I'd have saved-up a little longer and started with the top system, but that's just because I am kind of a sound nut... at the time I had to balance my economic situation with my huge desire to get us into the 20th century, soundwise.
 

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Posted by Oliver Pasch (Member # 1335) on 05-15-2006, 02:42 PM:
 
My recommendation:
KRIX KX 4610 from "down under" plus a powerful amp!
KRIX Homepage
Better than anything i've heard or felt before.

Oliver
 

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Posted by System Notices (Member # 2357) on 03-08-2008, 05:07 AM:
 

It has been 662 days since the last post.

 

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Posted by Catalin Balaceanu (Member # 3712) on 03-08-2008, 05:07 AM:
 
I hope this is the right topic to ask my question:
I've noticed that, in some movie theaters (especially those THX certified), have an incredibly powerful sub bass, that you can actually feel the floor and the chair beneath you, shaking like hell. Does anyone know any subwoofer model(s) that can achieve this kind of effect?
The auditorium I have is 70 feet long, 45 feet wide, 25 feet high and has 400 seats.
Thanks
 

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Posted by Marco Giustini (Member # 4544) on 03-08-2008, 08:06 AM:
 
Which is the correct SPL I must take in consideration whith analog sound? 113dBc is for Digital, and for analog?

Thanks

Marco
 

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Posted by Steve Guttag (Member # 268) on 03-08-2008, 08:17 AM:
 
There are many that can do that. It is a matter of chosing a subwoofer that has a low frequency response (goes down to 20Hz or lower) and having enough subwoofer and the power to drive them to the proper level.

A JBL 4645C is such a subwoofer (but there are others). If B-6 alignment is employed, its response goes down to about 20Hz. It can handle 800-watts continious and has a sensitivity of 97dB at 1-watt/1-meter.

So with just one unit (it is a single 18"), you would need over 8000-watts to achieve proper level...well that won't work.

So you add another identical unit. With two subs your power requirements drop to just over 4000-watts but you only have 1600-watts of power handling capability.

So you add another sub and your power requirements drop to about 2700-watts but you only have 2400-watts of handling so finally you add a 4th sub and you come to 2024-watts needed and you have 3200-watts of power handling.

Now it is a matter of getting enough amplifier power to deliver the 2024-watts across the four subs. One way to do this is with a QSC DCA-3422 amplifier...it has 1100-watts per channel into 4-ohms so wire the subs such that one pair is fed to each channel of the amplifier. Use the QSC SF-3 subwoofer filter to get the B-6 alignment that will extend the 4645C's response down to 20Hz and whola, you too will have a theatre shaking subwoofer system that won't blow up on any film running at fader setting "7"

The keys here are that the subwoofers must be mounted together to achieve mutual coupling (that is why the power NEEDED kept decreasing as I added subwoofers) and you MUST use the continious PINK NOISE spec of a speaker...not "program" or "Peak". The subwoofer track resembles a continious signal and it can last for a protracted period of time...time how long the subwoofers were used when the rocket took off in Apollo 13...that scene took out MANY improperly designed subwoofer systems.

The next key is that you have enough amplifier. You MUST use the 20-20KHz specification for the power handling. Many amplifier companies will use a 1KHz power rating spec to make them look more powerful....but ask yourself...self....how much single tone 1KHz singals are there in the subwoofer channel (or any other channel for that matter)? The answer is that the 1KHz power rating for amps is bogus and merely a marketing ploy that they all have to use in order to compete with those that only put that number out. QSC does list both 1KHz and 20-20KHz. In the case of the above mentioned DCA-3422...the 1KHz power is 1250-watts/channel into 4-Ohms but only 1100-watts/channel into 4-Ohms from 20-20KHz.

When in doubt, over-speaker and over-amp...a system that is too small will fail...a system that is too large will not mind playing things below its maximum just fine!

In the cinema industry...things are pretty well defined as to maximum levels so it is much easier to design a proper system...I'm amazed at how many people just guess or merely base a new system on how a system performed in a different theatre of different size.

Steve
 

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Posted by Marco Giustini (Member # 4544) on 03-08-2008, 08:38 AM:
 
Great informations.

And what about the maximum SPL for analog systems?

Thanks

Marco G.
 

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Posted by Catalin Balaceanu (Member # 3712) on 03-10-2008, 05:53 AM:
 
Steve, thank you so much for the detailed info. This is indeed very useful information. I can see you really like the 4645C sub Why is that?
Marco, I think the sub level for the analog is the one stated in most of the analog processor manuals, which is 85db. Still, I hear that some keep their subs level to around 90 db.
 

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Posted by Steve Guttag (Member # 268) on 03-10-2008, 06:20 AM:
 
For analog, you have the 85dB reference at 50% modulation...so for 100% modulation you come to 91dB...but for Dolby A there is a 3dB boost (over mono) and for Dolby SR you have a 6 dB boost (over mono or a 3dB boost over Dolby A) so you need to ensure that your sub can play a 97dB level...that is 13dB less than for digital.

So, believe it or not...you are down to about 200-225 watts for a single 4645C subwoofer. Digital places HUGE demands on a system that analog does not. Again, this is presumming fader setting of 7.

As for the JBL 4645C...yes I like that subwoofer. The driver is phenoninal (2242) and is one of the few that can take 800-watts pink noise...all day long (the way that driver cools its voice coil is better than most others). Also the 2242 in that cabinet with B-6 alignment is pretty darn flat, right out of the box so minimal EQing is ever needed. They can move a ton of air and down to 20Hz too. It seems to have delivered on every installation I've used it. So yeah, I like it quite a bit.

Steve
 

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Posted by Tim Reed (Member # 137) on 03-10-2008, 07:42 AM:
 

quote: Steve Guttag

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So with just one unit (it is a single 18"), you would need over 8000-watts to achieve proper level...well that won't work.

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quote: Tim Reed

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I was wondering how do you arrive at this figure?

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I just made it up and it sounded impressive

No, actually I do the math. If you download (or you may have a copy) of the Dolby Technical Guidlines, you can use their nomograph...just beware, they are too low by 3dB on the Subwoofer graph. I think I heard the reason was something to the effect that the demands on the subwoofer would seem impossible to typical exhibitor and thus they didn't want to scare them away from doing it at least close to properly. 3dB is a doubling of power, as you know but about the difference between 7 and 8 on the Dolby fader scale.

If you do use the 1994 version of the Technical guidelines...there is a formula on page 18 that will get you started...for subwoofers, power desired is 113dB, the distance is 2/3rds the length of the room (in meters).

While I'm not a speaker designer, there are various design parameters or alignments one can design to and B-6 is one of them. Think of it as slit loss...if you design a speaker system to a standard alignment, apply the complimentary compensation in electronics, you will get a very flat response with a sharp fall-off...this is the case with B-6. A 4645C will play almost ruler flat down to 20Hz and then drop like a rock. This is good because with that cabinet, the driver will unload below 20Hz (actually it is 22Hz, I think)...thus you don't want to try and play below that frequency. A proper B-6 filter will high pass there.

If you work with QSC products, their SF-3, SF-1 and all of their booth monitors will provide B-6 alignment. One can recreate a B-6 filter with appropriate parametrics...I believe it is a Q of 2 at 30 Hz. Note, Radio Design Labs also makes a suitable device called the C1XS.

Steve
 

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Posted by Mark Gulbrandsen (Member # 72) on 03-10-2008, 09:17 AM:
 
Steve... I think DOlby need to revamp those guidelines based on then uncompressed levels found in D-Cinema. 113 db is simply not enough...
Mark
 

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Posted by Steve Guttag (Member # 268) on 03-10-2008, 10:23 AM:
 
What are you sniffing? Compression and levels? DCinema uses -20dBFS reference...so yes, the subwoofer now needs to be able to make it to 115dB and the stage channels need to hit 105dBc but that is it...this has NOTHING to do with compression.

But what the hay...so with a 115dB needed subwoofer here are the numbers for the 4645C..

For one unit, you need: 12,766-watts (see how 2 meezly dB affects things at that end of the power spectrum!).

With 4 units you only need 3207-watts which is just about what the 4645C can handle 3200-watts for 4 units, continious pink noise. Add a 5th unit and you are down to about 2550 watts and enough driver to handle it. Again, this is true if you are running at fader 7 in a properly calibrated system.

Note, however, I believe SDDS and DTS already had 115dB max rather than Dolby's 113.

Then again, if the recording engineer is setting levels that are safe for Dolby Digital, the DCinema levels are not going to rise another 2dB so once again 113dB is safe so long as Dolby Digital films are being made and it has NOTHING to do with compression.

Steve
 

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Posted by Tim Reed (Member # 137) on 03-10-2008, 03:39 PM:
 
Thanks again, Steve. Very informative and enlightening.
 

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Posted by Marco Giustini (Member # 4544) on 03-10-2008, 04:19 PM:
 
Thanks Steve. I was searching the SR SPL limit figure since a while.

I read older threads here about B6, you are always very clear. I'm just puzzled that there isn't many informations on JBL datasheets.

For example, if you check on DCM Manager 2007, B6 is enabled on 4632-T, while on JBL's datasheet there is nothing. 4645C is just referring "with EQ".
EV and QSC are much clearer.

Again, thanks

Regards

Marco
 

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Posted by Catalin Balaceanu (Member # 3712) on 03-10-2008, 05:45 PM:
 
Man, I love this forum!!!
Thanks for the very useful information, Steve.
 

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Posted by Catalin Balaceanu (Member # 3712) on 03-21-2008, 10:49 AM:
 
is there a big difference between the 2242h and 2242hpl drivers, except the rubber tire around the magnet on 2242h?
Thanks

Catalin
 

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Posted by Louis Bornwasser (Member # 3063) on 03-21-2008, 10:51 AM:
 
No: only the source: "pl" is private label. Same specs. Louis
 

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Posted by Catalin Balaceanu (Member # 3712) on 03-21-2008, 10:53 AM:
 
thanks for the fast reply, Louis!
 

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Posted by Steve Guttag (Member # 268) on 03-21-2008, 11:39 AM:
 
The "pl" at the end of the model denotes that the frame's outer ring is black rather than silver. A big plus for cinemas...in the 80s we were constantly painting the damn things!

As for the rubber boot...it is not normally included (and often the actual driver label isn't either) on pre-assembled speakers. When drivers are sold as components, they come with the boot and the label. In the case of the 2242, I believe the label is always included (it is just a sticker).

Steve
 

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Posted by Ron Funderburg (Member # 4561) on 03-21-2008, 01:54 PM:
 
Just curious about specific type of Sub that seems to have come and gone. Several years ago there were several Tech's that were pushing an aqueous (not sure about sp) sub it had water in a sealed plastic chamber or bladder in the top of the sub. The theory was that can't compress water so the sound waves would push up against the water and it would force it back down and out making and I quote “More bang for the buck”.

I went to several demonstrations where they had the aqueous in one theater and would play stuff and you would feel it. Then across the hall they had the regular sub and you wouldn't feel it as much but when I toured the booth the settings on the faders were different so it appeared to me that the aqueous auditorium was being played at 7 and the non was being played at 6. That is big difference and I thought to myself “Self that Aqueous is just a rip”

It was only highlighted for about 3 years then went away from what I can remember. It seems like it showed up in 1999 and was gone by 2001 or 2002.

Anyone have any unbiased information on them?

Steve you are well in to the know on things, what do you know on this?

I think the fact I don't seem the advertised anymore speaks volumes or maybe with great volume!
 

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Posted by Steve Guttag (Member # 268) on 03-21-2008, 06:06 PM:
 
Abingdon Cinemall uses them, as I recall. I have not given them a serious listening so I can not offer any real comments on them. As you know, sound is quite subjective and, as such, there are not definative speakers that are simply the best.

Those speakers that I am familiar with, I have voiced noted preferences and I generally can back them up with some not so subjective facts...like sensitivity, frequency response and power handling...which is not to say they necessarily sound good or better than others (except in my opinion) but they technically qualified for the job.

Steve
 

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Posted by Ron Funderburg (Member # 4561) on 03-21-2008, 08:04 PM:
 
Steve I did find a website with an article which reviews Hydrosonic HS-12S, which is a similar sub if not the one! It supposedly moves the sound though the concrete so you feel deeper according the article and they have all kinds of charts and graphs to support the claim but having only heard it once or twice I can't make an honest evaluation on it.

Like you I find sound is in the ear of the beholder! We can all agree on pure crap but when it comes to this is better no that is better people seem to be all over the place.

This is the web article I can't see upload date on it!

http://www.ultimateavmag.com/features/704way/index4.html

I saw the movie Rules of Engagement with Tommy Lee Jones and when the helicopters flew over the had part of the blades rotating around in the subs and you could feel air move over you. That impressed me but it could have been as much volume as the design of the sub.
 

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