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tony359
02-08-2006, 11:50 AM
HI everyone

I'm carrying a question on JBL subs equipped with the 2242H driver since many years.

The JBL 4645B or C is an example. On 4645B/C pdf is clearly shown (more clear on 4645B!) two frequency response: "with" o "without" EQ. They say that without equalization the f3 of the system is limited to about 35Hz (the fs of the 2242) while with "equalization" the system can go down to about 22Hz.

Now, on a cinema forum, a very competent tech told me that this kind of subwoofer, like other brands as EV, are intended to be used with B6 filter that adds a 6dB boost at about 30Hz and apply a high pass filter under the same frequency.

I had the chance to make a quick test between triple chamber 4688 (rated 28Hz without equalization) and 4645B and I realize that without equalization (was a quick test!) the 4688 outperform greatly the 4645B. And this explain to me why most of the technician says that the 4688 is the top even if it can handle only 600W in 150Kg! :)

Ok, so where is the problem? I'd like to know more of this "EQ" 'cause it's not so easy to put 6dB at 30Hz on a subwoofer is the system is not designed for that signal, isn't it?

My search of knowledge is not only for home use where I can identify immediately any kind of problem if the driver is overdriven. I'd like to know what consideration should be done installing an array of subs with this filter in a theater for example (I'm not an installer but sometimes I make something... it's an hobby! :) ). If 4x4645B are enough, just an example, for a theater 20 meters long, what parameters I have to take in consideration if I put a B6 filter on the line?


A friend of mine simulated the 4645B driver and box and told me that the system is NOT B6 aligned. So I asked JBL (just to have confirmation of the type of equalization needed!) but they told me that they can't help me and that I should ask an installer... :( I was just asking for system specs! EV and QSC write them on pdf!

On the Market I can find two filters (made by RDL and QSC) made specifically for subwoofers that needs equalization "like 4645B"

http://www.fullcompass.com/Products/PrinterFriendlyPage.aspx?pid=SKU--28502

RDL apply the boost at 32Hz, QSC at 25Hz... I'm a bit confused!!

Can someone help me better understanding this argument? :)

Thanks and bye!

Antonio

4313B
02-08-2006, 12:02 PM
Hello :)
Now, on a cinema forum, a very competent tech told me that this kind of subwoofer, like other brands as EV, are intended to be used with B6 filter that adds a 6dB boost at about 30Hz and apply a high pass filter under the same frequency.True, the boost part at least. B6 is close enough. B5, B6.
I had the chance to make a quick test between triple chamber 4688 (rated 28Hz without equalization) and 4645B and I realize that without equalization (was a quick test!) the 4688 outperform greatly the 4645B.

Ok, so where is the problem? I'd like to know more of this "EQ" 'cause it's not so easy to put 6dB at 30Hz on a subwoofer is the system is not designed for that signal, isn't it?The 4645 with the 2242H can handle the juice. Note that some of the early 4645's came with 2245H's and they weren't nearly as robust in this application.
My search of knowledge is not only for home use where I can identify immediately any kind of problem if the driver is overdriven. I'd like to know what consideration should be done installing an array of subs with this filter in a theater for example (I'm not an installer but sometimes I make something... it's an hobby! :) ). If 4x4645B are enough, just an example, for a theater 20 meters long, what parameters I have to take in consideration if I put a B6 filter on the line?Read

http://www.jblpro.com/pub/manuals/pssdm_1.pdf

http://www.jblpro.com/pub/manuals/pssdm_2.pdf

Depending on boundary reinforcement you may not need full boost.
Maybe some of these other publications look interesting as well:

http://www.jblpro.com/pages/tech_lib.htm


A friend of mine simulated the 4645B driver and box and told me that the system is NOT B6 aligned.Approximately quasi-third order becoming approximately 5th order with EQ.
So I asked JBL (just to have confirmation of the type of equalization needed!) but they told me that they can't help me and that I should ask an installer... :(They're right.
I was just asking for system specs! EV and QSC write them on pdf!Yeah, alot of people are irritated that JBL doesn't have more extensive PDF's.
On the Market I can find two filters (made by RDL and QSC) made specifically for subwoofers that needs equalization "like 4645B"

http://www.fullcompass.com/Products/PrinterFriendlyPage.aspx?pid=SKU--28502

RDL apply the boost at 32Hz, QSC at 25Hz... I'm a bit confused!!

Can someone help me better understanding this argument? :)

Thanks and bye!

AntonioThe 4645 was originally tuned to 30 Hz for use with the 2245H. It was retuned to 25 Hz for use with the 2242H. Where is a link to the QSC model? I don't feel like looking for it.

4313B
02-08-2006, 12:27 PM
BTW - I could be wrong but it seems to me some of those early 4645B boxes were loaded with 2245H's. I think they ended up with 2242H's and the 2245H's landed in the Tent Sale.

spkrman57
02-08-2006, 12:28 PM
I'm not sure what dictates needing the LF EQ, but I know in a small sized listening room I have found my 2242 (9cu ft tuned to 28hz) sounds much better without the boost.

Maybe those with larger rooms would like to add the boost.

My room dimensions: 13' x 16' x 8' ceiling with some open areas to the kitchen and hallway.

And with such a small room, it takes so little wattage to rattle your bones that I would be scared to approach even 25% of the power handling(800 watt).

Hope this helps!

Ron

4313B
02-08-2006, 12:29 PM
I'm not sure what dictates needing the LF EQThe environment.

I have found my 2242 (9cu ft tuned to 28hz) sounds much better without the boost.Me too (8 cu ft, 25 Hz), I ended up not needing any boost. But I was cutting them off at 40 Hz too.

BTW - I preferred those boxes you now have. ;)

tony359
02-08-2006, 12:34 PM
Hello http://audioheritage.org/vbulletin/images/smilies/smile.gifTrue, the boost part at least. B6 is close enough. B5, B6.
Hi!

What do you mean?



The 4645 with the 2242H can handle the juice. Note that some of the early 4645's came with 2245H's and they weren't nearly as robust in this application. Read

http://www.jblpro.com/pub/manuals/pssdm_1.pdf

http://www.jblpro.com/pub/manuals/pssdm_2.pdf

Sure, I was referring of 4645B and C, not the original 4645.
About the juice: let's suppose I'm designing a sound system and that the power requirements says that I need 4 subwoofer: I need the same 4 subwoofers even with the EQ?

I'll read the pdf, I've already read where it says that coupling effects boost the bass frequencies.



Depending on boundary reinforcement you may not need full boost.
Maybe some of these other publications look interesting as well:

http://www.jblpro.com/pages/tech_lib.htm

Thanks


They're right.
Why? I didn't ask to analyze my setup, just to know the parameters.
Example: ElectroVoice says on their pdf how to properly setup the TL880D with or without equalization. QSC Subwoofers list the B6 parameters in the data sheet http://www.qscaudio.com/products/speakers/dcs/dcs_sb5218_sb7218.htm

LF boost Freq. = 25 Hz
Q = 2.0
Gain = +6 dB
provided by QSC, SF-3 or DCM

I was asking for data like this! :(


The 4645 was originally tuned to 30 Hz for use with the 2245H. It was retuned to 25 Hz for use with the 2242H. Where is a link to the QSC model? I don't feel like looking for it.
But both device are listing the 4645B and not the 4645. I was told that the 4645 can not handle the EQ...

Here is the link http://www.qscaudio.com/support/library/manuals/accessories/sf-1.pdf

Thanks for your help!

Bye
A

4313B
02-08-2006, 12:42 PM
What do you mean?I mean that it isn't uncommon for people to refer to any system built to utilize the 6 dB bump filter at resonance as a B6 alignment. No biggie. I've done it too. The JBL B460 for example, was a quasi-third order without boost and a fifth order with boost. Stick it in a 4th order box and it becomes 6th order with boost.
Sure, I was referring of 4645B and C, not the original 4645.
About the juice: let's suppose I'm designing a sound system and that the power requirements says that I need 4 subwoofer: I need the same 4 subwoofers even with the EQ?Depends on your environment. That's why JBL publishes it both ways in the brochure.
Why? I didn't ask to analyze my setup, just to know the parameters.
Example: ElectroVoice says on their pdf how to properly setup the TL880D with or without equalization. QSC Subwoofers list the B6 parameters in the data sheet http://www.qscaudio.com/products/speakers/dcs/dcs_sb5218_sb7218.htm

LF boost Freq. = 25 Hz
Q = 2.0
Gain = +6 dB
provided by QSC, SF-3 or DCM

I was asking for data like this! :( We all feel your pain. I think it would be nice if JBL gave us more data.
But both device are listing the 4645B and not the 4645. I was told that the 4645 can not handle the EQ...Yeah, it's probably best not to use a boosted 4645 in a Pro application these days. That's why the B and C exist. Like I said, I think there were B's around that were tuned higher. I could be wrong. It's best to check the Fb of a 4645B, I'm pretty certain all 4645C's are 25 Hz.
Here is the link http://www.qscaudio.com/support/library/manuals/accessories/sf-1.pdf
Ok. Ill look at it. Thanks.

4313B
02-08-2006, 12:47 PM
The QSC looks nice enough. It's obviously targeted at the 4645B and 4645C loaded with the 2242H and tuned to 25 Hz.

tony359
02-08-2006, 12:56 PM
I mean that it isn't uncommon for people to refer to any system built to utilize the 6 dB bump filter at resonance as a B6 alignment. No biggie. I've done it too. The JBL B460 for example, was a quasi-third order without boost and a fifth order with boost. Stick it in a 4th order box and it becomes 6th order with boost.
Ok!


Depends on your environment. That's why JBL publishes it both ways in the brochure.We all feel your pain. I think it would be nice if JBL gave us more data.
I see it as very negative behaviour... If I was an installer, how can I properly design a sound system if the factory does not help me this way??


Yeah, it's probably best not to use a boosted 4645 in a Pro application these days. That's why the B and C exist. Like I said, I think there were B's around that were tuned higher. I could be wrong.

Really? Same models with 2242H (I'm sure of this) tuned at different frequencies? :blink:

But can you explain me why some driver can handle the boost and others not? What changes in the speaker design?

I'll measure the boxs for the fs... :(

Bye
A

4313B
02-08-2006, 01:06 PM
I see it as very negative behaviour... If I was an installer, how can I properly design a sound system if the factory does not help me this way??Installers have networked and "know people".
But can you explain me why some driver can handle the boost and others not? What changes in the speaker design?

http://www.jblpro.com/pub/technote/tn_v1n18.pdf

http://www.jblpro.com/pub/technote/tn_v1n22.pdf

Maybe this too:

http://www.lansingheritage.org/html/jbl/reference/notes/tech1-3a.htm


I'll measure the boxs for the fs... :( Fb. Why the frown? I'd be excited about it. :)

tony359
02-08-2006, 01:14 PM
Installers have networked and "know people".

:crying:



(http://www.jblpro.com/pub/technote/tn_v1n18.pdf)http://www.jblpro.com/pub/technote/tn_v1n18.pdf

(http://www.jblpro.com/pub/technote/tn_v1n18.pdf)http://www.jblpro.com/pub/technote/tn_v1n22.pdf

Maybe this too:

(http://www.jblpro.com/pub/technote/tn_v1n18.pdf)http://www.lansingheritage.org/html/jbl/reference/notes/tech1-3a.htm
(http://www.jblpro.com/pub/technote/tn_v1n18.pdf)
:) Thanks!




Fb. Why the frown? I'd be excited about it. :)

Yes, Fb.

Frown because I would not believe that I can find two JBL 4645B with different tuning... :( They should call them "B1" and "B2" :)

Oh, I forgot the main question! :) If the Fb of my 4645B is 25Hz the boost should be applied to 25Hz, isnt'it? And at the same frequency the HPF?

Bye
A

4313B
02-08-2006, 01:23 PM
Frown because I would not believe that I can find two JBL 4645B with different tuning... :( They should call them "B1" and "B2" :)Well, like I said, I could be wrong. I'd check it on a 4645B though. It's just not a problem.

Installers have networked and "know people".We'll wait and see who comes along and answers this thread.

tony359
02-08-2006, 01:26 PM
We was replying together!

Sure, it is not a problem. I'll check soon. I edited my previous message at the end... :)

Thanks for your help!

Bye
A

4313B
02-08-2006, 01:32 PM
Oh, I forgot the main question! :) If the Fb of my 4645B is 25Hz the boost should be applied to 25Hz, isnt'it? And at the same frequency the HPF?Yep.

The bump filter, or boost filter, is a HPF with a Q of 2 hence the "bump". +6 dB for Q = 2 (1.93 actually).

Bye

tony359
02-08-2006, 01:56 PM
Yep.

The bump filter, or boost filter, is a HPF with a Q of 2 hence the "bump". +6 dB for Q = 2 (1.93 actually).

Bye
Uhm... How many db/octave is a Q=2?

So a HPF Q=2 at the Fb of the sub. Then a +6dB at the same frequency, Q=2.

Question: I analyzed the output of the RDL ST-CX1S with my RTA and I found that to have the same response using my Behringer DEQ2496 I have to set the gain of parametrics equalizers at +10dB on the Fb frequency since the HPF interfere with the boost. The +6dB are what has to be set or I should see a +6dB boost at, say, 30Hz regardless of the equalizer setting? I'm considering the electric domain, no the subwoofer response.

If I'm not clear, just tell me! :)

4313B
02-08-2006, 03:39 PM
I read that the 2241 might be a better choice as a sub.I read that blondes had more fun than brunettes.

4313B
02-08-2006, 03:44 PM
Uhm... How many db/octave is a Q=2?

So a HPF Q=2 at the Fb of the sub. Then a +6dB at the same frequency, Q=2.

Question: I analyzed the output of the RDL ST-CX1S with my RTA and I found that to have the same response using my Behringer DEQ2496 I have to set the gain of parametrics equalizers at +10dB on the Fb frequency since the HPF interfere with the boost. The +6dB are what has to be set or I should see a +6dB boost at, say, 30Hz regardless of the equalizer setting? I'm considering the electric domain, no the subwoofer response.

If I'm not clear, just tell me! :)12 dB/octave.

What HPF? Your subsonic HPF? If that's so then I see why your parametric has to be set higher.

tony359
02-09-2006, 06:30 AM
12 dB/octave.

What HPF? Your subsonic HPF? If that's so then I see why your parametric has to be set higher.

I understand that the B6 filters I linked has a HPF at 30Hz and a boost at the same frequency.

So I adjusted a HPF on the DEQ2496 and the boost.

Is it wrong?

Bye
A

JuniorJBL
02-09-2006, 07:41 AM
I read that the 2241 might be a better choice as a sub.

:wtf: :no:

JBL 4645
11-20-2009, 12:26 AM
Stuffing up but (one or two ports) on the sub will greatly increase the frequency response lower down the frequency spectrum.

Iíve managed to get mine to display on spectrumlab well below 20Hz but not at high SPL db level that will decrease somewhat for single sub. Add on another sub of the same the very lowest part as we know will notch up a few db and so and so on....

...Hence you want have enough room to swing a cat, around by the time you filled your, room up with 18Ē JBL subs and Iím sure the wife will want to devoice you as well.:D