dbx driverack pa+ help

servox

Hi all

This is my first post and would like some help with my dbx driverack pa+

I have used the setup wizard and selected custom amp option

I have setup crossover for full range, setup feedback filters and balanced the system and set the output limits.

The problem is that the quality of the sound is worst than going straight from the mixer.

If I auto eq the system then it sounds ok.

Is this normal that the sound quality is worst without using the auto eq? Than going straight from the mixer to my amp.

I'm just worried that the dbx driverack pa+ has a fault or I have done something wrong with setting up the system.

Your comments with be helpful

Dave

Gadget

If you want real help you'll need to give real information, what you have written tells us nothing...we don't know what speakers you have, what amps or mixer.

It would help to know what you did use for parameters when you set up.

Perhaps if you had used a preset to begin with, and compared that to what you did in the wizard?

From your post it sounds like you perhaps have a single pair of fullrange speakers...and it troubles me when you say "and balanced the system"... with a stereo fullrange you have nothing to balance...perhaps then, try the stereo fullrange preset and see if there is any difference.

If you set it up properly without any modifications, and the filter truly IS set for fullrange there should theoretically not be much of any difference till you start setting up the modules.

Please include your limiter setup and parameters because this could be the culprit as well.

Gadget

Dra

You mentioned setting up the feedback filters. How did you do this? Did you then let an open mic be the feedback source, or did you play music and let the music be the source?

DRA

servox

Hello Gadget and Dra

I have the following for karaoke setup

Yamaha EMX5000-12
studiomaster 1200d
JBL MR925

Sorry getting my words mixed up. I meant to say Gain Structure not balanced the system.

The Feedback filters were set by slowly increasing the mic gain. No music playing or noise in the room.

Since reading the first post i have tried Full Range preset and things are a lot better. Must of done something wrong first time

i have attached some pictures of the limiters, x-over and eq using a Samson MM01 mic.

they sound good a low/medium volume but get very high pitched at higher levers. (makes your ear hurt on some songs)
could the PEQ's help with this problem.

could you recommend any tweaks

cheers dave

Gadget

well...
Hmmm. those speakers are 10dB down @ 60hz.. so hi passing them @ 40 hz with an BW6 slope is... well useless. Are you trying to drag more low end sound out of those things? They were an early JBL box that really needs a sub in order to produce full range into the sub region. If your playing loud you really should set the hipass @ the 3dB down point for even a modicum of protection.

What amp are you using?

From what I'm seeing your auto EQ pass shows that the speakers fall off quickly below 100 hz...

What procedure did you use for the Auto Eq?

Have you seen the FAQ section? and taken advantage of it's information?
viewforum.php?f=60

Do you get a lot of feedback?

Gadget

servox

Hi Gadget

i set the 40hz cut because the speakers spec say 40-17hz response, BW6 is the default setting. what should this be set to??

dont understand your advise about "set the hipass @ the 3dB down point for even a modicum of protection". could you explain

my amp is a studiomaster 1200d 375w @ 8ohms

i think i used either flat or dj for the auto eq. im not sure.

there was alot of feedback during the process of AFS

i do have a set of bass bins, but i was trying to set the jbl speakers up first, as i do alot of smaller venues for karaoke and take the bins for dj setup
powered with a JBL MPX1200 amp, 800w @ 8ohms, 1200w @ 4ohms, 2400w @ 8ohms bridge, 3200w @ 4ohms bridge

bass bin are wharfedale Force 10SB, twin 15", but i havent found any information about the best crossover point for them.

should i always use the bins with the JBL MR925? even in small venues

thanks dave

Dra

Gadget is right. They are spec'd 60-17K (-10db). For a 15" that is really poor. Not even a -3db spec listed. Odd.
Some times you can eq some low end into the cab, but that requires more power and these aren't built for power, so damage could result. If you only need moderate volume levels (or low) you could get them to sound fuller with eq, but self control is need. You mentioned the louder they got the worst they sounded, that is typically the opposite of what you get (to a point).

Depending on your experience (and Gadget might also give a recommendation here), you could set a really steep cutoff at a guessed 3 db. I checked the a few JRX series and the difference from "Range" (-10) to "Response" (-3) is about 10hz, so let's say the -3dg point is actually 70hz.
Set the hi-pass filter at 70hz BW 24 (or steeper if available). Then with the PEQ, add a bell somewhere in the 75hz range. I'd say about +5db for added gain. Play with different "Q's", starting about 1, moving the center frequency up and down, maybe 70 to 80hz. Run a pass and see what the graph does
Remember, this is only a concept of what you are trying to do, which is to, as smoothly as possible, eliminate damaging low freqs (below 60) while boosting the 60-100hz range and not hyping the 125hz- 160hz area that is already hot.
Oh. It is important that you know which curve you choose, to interpret the results. For this process, and for karaoke, I recommend Flat.

Gadget, any thoughts?

DRA

servox

thanks Dra, i will try those settings and report back.

might be time for a new set of speakers. had these about 8 years

any reconmendations??

Gadget

Who me? Thoughts? opinions? YA right

Ok I concur with Dra.. 70 hz BW 18 od 24 (thats the steepest slope available on the PX DRPA.

This is likely the reason the sound deteriorates the louder you get... BTW those speakers go back to the 90's when the components available, and the cabinet technologies were.. well 15 + years behind what is available today.

That said, those speakers make decent midrange cabs, and for Karaoke use where there isn't a need for huge bass as in DJ work, they should work ok. But with the frequency limitations in mind... The big problem with JBL (especially in the day) is a distinctly harsh HF (a well known JBL trait BTW). That lends itself to the feedback issues...

So, what can you do? Try this auto EQ method:

Place the speaker on it's side, and tilt it so that the speaker front face is / tilting downward somewhat...place the mic out so that it's in the full field of the horn. You can use either a hard floor, and the PZM technique as above or, the one pictured below

(except have the speaker on it's side...)
cover any hard surfaces in the path of the mid/hf with blankets

Run the Auto Eq pass flat, and use hi precision , get it about as loud or louder than you play... there is good practice in setting up a few different volumes and storing them because the louder you get the more difference in frequency response there will be...

For the sub/top config use the limited power you have as a key...
Sub: HPF 40hzBW18, to 118hzLR24
Top: HPF118hz LR24

One other factor here could be the limited amp power available...make sure your not clipping the amps, and don't depend on the limiters to protect your speakers.

Make sure you read the FAQ sections on Auto EQ and the "start here" thread.

Gadget

Gadget

any reconmendations??

Whats your budget?

bang for the buck in unpowered speakers is this:
http://www.dasaudio.com/index.asp?pagin ... =1&lang=en
Last I saw they were under $800 each @ NSL

But perhaps the QSC K12's would be a better way to go...about the same money, but really nice!

Gadget

servox

Thanks for settings and photos gadget

i will try them over the next few days and let you know how i get on.

ive been using the Samson MM01 mic from a friend. Would the dbx rta-m mic be any better for eq results???
will buy one if their better.

those speakers look great, i've always used passive speakers though. Might try some active one.

thanks again for your help Gadget and Dra

dave

Gadget

Ya then you'd have power AND speakers that are matched...Those DAS speakers are GREAT bang for the buck though... but a more professional grade...
2" exit horns, and 4" voice coil woofers... but you'd need a LOT more power to run them!

gadget

servox

just an update......guys

things are much better with the sound, but im still not happy with the harsh sound from the jbl mr925.

so im looking into getting some others.

thanks for your help and input with the settings etc....


cheer dave

Dra

Maybe you're doing something "wrong"?
Can you post a pic of the GEQ curve that the AUTOEQ gave you (pre- PEQ adjustments) you ended up with? An also the PEQ settings you used to fix it? Also the auto EQ GEQ results (post- PEQ adjustments).

We hate to have you buy new speakers until we know that they are really a problem (I know, I know...JBL :? )

DRA

Dennis

Dra wrote:

Maybe you're doing something "wrong"?

servox may not be getting the most out of the PA+ but the assessment of the MR925s is correct and any amount of EQing falls under the heading of "lipstick on a pig".

Dennis

Gadget

and there you have it! thanks Dennis!

Dra

You got something against pigs and their dating habits?

Dennis

Dra wrote:

You got something against pigs and their dating habits?

I take it, from that reply, that you have the same low opinion of MR925s as I do.

Dennis

Gadget

I know I do... :roll: but the real ugly betty was the TRX line