Attenuate compression driver output. |
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rezsbc
Registered User Joined: 21 November 2006 Location: Ireland Status: Offline Points: 352 |
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Posted: 20 September 2007 at 1:24pm |
Hey people....
Just a question. We've got some JBL SRX series 15" boxes and double 12" boxes. These can sound really nice bi-amped however when run through the passive crossover inside them they spew out way to much high end from the compression driver/horn.
I've been dealing with it by eq'ing the sh*te out of the boxes, pulling everything after the 1.2Khz crossover point back by 6-12db most times.
With the EQ applied they sound really nice again.
I did start thinking about better solutions and was wondering if there was something I could put in series with the compression driver inside the box that would lower the signal going to it? A resistor or something? I'm no expert about things like this but would be interested if anyone had suggestions.
I can deal with it as is with the EQ but would be nice not to have to think about it.
rez.
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matt andrews
Registered User Joined: 15 September 2004 Status: Offline Points: 501 |
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An lpad will do what you require, look here.
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rezsbc
Registered User Joined: 21 November 2006 Location: Ireland Status: Offline Points: 352 |
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thanks man exactly what I need!!!!
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tb_mike
Old Croc Joined: 01 October 2004 Location: New Zealand Status: Offline Points: 2744 |
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Bear in mind that the jbl will have an Lpad,or a version of it,already so youl have to modify the one thats there.Perhaps stuff a sock in the horn flare LOL
- Many say that JBLs sound bright.
Im not sure if this is due to the program material,or an edgy titchy compression driver with strange resonances on it. DJK might have some input.
I dont think JBL would purposely emphasise anything - HIFI speakers do this enough.
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_djk_
Old Croc Joined: 23 November 2004 Location: United States Status: Offline Points: 6002 |
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A specific model number is needed, then I will look at the JBL crossover design and comment.
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djk
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rezsbc
Registered User Joined: 21 November 2006 Location: Ireland Status: Offline Points: 352 |
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SRX715 and SRX722.
I'm sure JBL are doing everything ok... this is probably a matter of my personal taste I don't know but for me the highs are too loud.
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HansA
Registered User Joined: 07 March 2007 Location: Norway Status: Offline Points: 595 |
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rezsbc: your hearing is to good. Go get some eardamage as the rest of us.
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�*�o�O�o�*�*: HansA, The FUBAR sound technician :*�*�o�O�o�*�
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_djk_
Old Croc Joined: 23 November 2004 Location: United States Status: Offline Points: 6002 |
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I looked at the network designs. They are very complex and NOT compatible with adding an L-pad. I would bi-amp them. The passive crossovers look like they will not work correctly with a resistor or an L-pad added to the highs. Loudspeaker enclosure 'diffraction loss' occurs in the low frequency range of loudspeakers in enclosures that are located in the open, away from walls or other surfaces. The essence of it is this: a speaker radiating into half space plays 6 dB louder than the same speaker radiating into full space. A full range speaker finds itself radiating into half space that the upper frequencies but radiating into full space at lower frequencies. This results in a gradual shift of -6dB from the highs to the lows. This is called the '6 dB baffle step' or the enclosure's 'diffraction loss'. The center frequency of the transition is dependent on the dimensions of the baffle. The smaller the baffle the higher the transition frequency.
All enclosure shapes exhibit a basic 6 dB transition or step in the response with the bass ending up 6 dB below the treble. The -3dB point for the 722 is about 300hz, you will need about 3dB of boost there and about 6dB of boost in the 80hz region, and about 1dB of boost around 600hz. The step points for the 715 will be roughly 250hz, 63hz, and 500hz.
The JBLs are flat to very high frequencies. Close mic techniques sound un-naturally bright on flat systems. Sound at a distance does not have as much HF content as sound up close does. It is recommended you follow a 'house' curve and do a 3dB/oct roll-off starting about 3Khz.
These two combined will give a shift of almost 12dB between 100hz and 10Khz and will probably sound close to what your ear thinks is 'right'.
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djk
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HansA
Registered User Joined: 07 March 2007 Location: Norway Status: Offline Points: 595 |
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There shouldnt be a problem adding a serial and parallel resistor right before the tweeter, conserving the correct impedance.. ??
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�*�o�O�o�*�*: HansA, The FUBAR sound technician :*�*�o�O�o�*�
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rezsbc
Registered User Joined: 21 November 2006 Location: Ireland Status: Offline Points: 352 |
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Thanks DJK... very detailed!!!
I'll give what you suggest a try... although the purpose of this was to run them without any EQ but hey.
Thanks again!!!
rez.
and p.s. jokes aside HansA it's not just my hearing trust me stand in front of these bad boys you'll be reaching for that EQ in no time!!!
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HansA
Registered User Joined: 07 March 2007 Location: Norway Status: Offline Points: 595 |
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I know. I to feel most untuned JBL systems are to bright.
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�*�o�O�o�*�*: HansA, The FUBAR sound technician :*�*�o�O�o�*�
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csg
Old Croc Joined: 17 September 2007 Location: bedford Status: Offline Points: 6086 |
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if you want to lower the output of the comp driver rather than applying loads of eq all the time ( in my book to much eq always leaves other problems) then you will be able to using a correctly designed L pad network directly before the comp driver and after the passive network in the speaker. Dont go down the simple route using one resistor in series as you will alter the impedence of the comp driver that the passive network sees, hence altering the crossover fequency. An l pad will ensure that the crossover point remains unaffected.
Look in the eminence book for l pad resistor values.
hope that helps
chris
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