PX and JBL PRX518S Subs
hosehead
Posts: 10
Hello,
I´m new in this forum and new to the audio scene. My setup is:
-EON15G2 (tops)
-PRX518S (subs)
-Driverack PX
Two things:
1) just how accurate is the PX in terms of crossover settings? Can I trust that it is doing what it says it´s doing or is there big room for error? will it be more accurate than the built-in crossovers on my PRX subs?
2) I have noticed that if I turn off all other speakers, I can still hear the human voice comming from the subs along with a mixture of other instruments, and I don´t think this should be the case since these subs are only supposed to deal with lower frequencies, is this a normal thing?
Any help on this matter will be greatly appreciated, thanks guys.
I´m new in this forum and new to the audio scene. My setup is:
-EON15G2 (tops)
-PRX518S (subs)
-Driverack PX
Two things:
1) just how accurate is the PX in terms of crossover settings? Can I trust that it is doing what it says it´s doing or is there big room for error? will it be more accurate than the built-in crossovers on my PRX subs?
2) I have noticed that if I turn off all other speakers, I can still hear the human voice comming from the subs along with a mixture of other instruments, and I don´t think this should be the case since these subs are only supposed to deal with lower frequencies, is this a normal thing?
Any help on this matter will be greatly appreciated, thanks guys.
0
Comments
ie...Lows - 40hz BW18 -- 150hz LR24
Highs - 120hz LR12
DRA
If I am using the PRX518S on their own I cannot be sure of what the settings are because the JBL website shows two different sets of specs in two different documents: the spec sheet shows one thing and then the user manual shows another one.
If I am using the driverack, I can pretty much choose whatever I want but I would like to know what works better. Normally, I will use the folowing:
-tops: hi-passed at 125hz
-subs: lo-passed at 118hz
-the filter will be a LR24 in both instances
These settings sound good to me but I wonder if there is a better setting and, most importantly, I wonder if there is anything wrong with my subwoofers, since I can actually hear the human voice when they are being used on their own (no driverack, all other speakers off).
To complicate things even more, the electric xo point of either your sub or the DRPX is probably different than the actual acoustic xo point...Your sub is suppose to be crossed at a specific frequency, but when you raise or lower the gain of the sub, you also raise or lower the xo point and it's the same with the DRPX.
Dennis
The voiced speech of a typical adult male will have a fundamental frequency from 85 to 180 Hz, and that of a typical adult female from 165 to 255 Hz
That doesn't even take into consideration any of the harmonics of the fundamental...
So, yes, there is a significant amount of the human voice in the subs when crossed @ 125hz....
NOTE: even though the subs are hipassed @ 125 hz and even IF they were crossed using a BW24 filter...significant information past that 125 hz will be present... the information will be more and more dB down the higher the frequency goes... but it's still there.
Now, if you had LABsubs, EAW 949, or Cerwin Vega earthquakes (horn loaded subs) then yes I could maybe understand your concern, but front loaded subs....no.
As for better crossover points...maybe something closer to 100hz... maybe even lower...AND the cool thing is... it's really easy to experiment, and costs virtually nothing...
Gadget
1) JBL is posting two different sets of specs for the PRX518S. The spec sheet says that the crossover mode is dsp controlled with a 48db filter slope and the crossover point is 110hz; the user manual says that the crossover mode is dsp controlled with a 24db filter slope and the crossover point is 120hz. Should I trust the spec sheet or should I trust the user manual. I have tried to contact jbl without success.
2) When I use the PRX on their own (with their internal crossovers) I can hear more than just low frequency content from the subs, but when I hook-up the DriveRack and start lowering the crossover point (low-pass) from infinity down to 120hz (LR24) I can hear how the upper range content starts to fade away from the sub.
Based on my observations, as described above, I can conclude that regardless of the crossover point or filter slope that the PRX518S is using internally, it is entirely different from anything that I can do with the DriveRack PX, and so either the internal crossover of the PRX or the crossover on the DriveRack PX could be at fault. I am more inclined to believe that the DriveRack PX is more accurate, but can anyone please shed some light on this matter please? or better yet does anyone know for shure what the real specs are for the PRX518S?
Thank you for your involvement, everybody.
The 260 wizard suggest 100hz BW24 for the G2 and running the 518s with it's internal x-over engage. and running the PX lo filter flat. Are those cabs in the PX wizard?
DRA
DRA
Yes, the EON15G2 is included in the wizard of the DRPX and the recommended setting is 118hz LR24 with a flat filter for the PRX subs. The x-over of the PRX subs is always on, you cannot deactivate it. It is interesting that the 260 and the DRPX suggest different settings for the EON, but I agree that with the 15� driver I should be able to get away with lowering the x-over point to 100hz.
I was able to talk to a JBL tech rep this morning about the difference in specs and he said he would ask the engineering department. I´ll call him a little later today and let you all know in case anyone else is interested in knowing the actual specs for the PRX518S.
Regarding whether there’s something wrong with my subs, I think Dennis and Gadget have already cleared that up for me (thanks guys!). I now understand that if the crossover point is high enough or if the filter slope is long enough, the human voice can be present in the sub output.
One question still remains for me, though, regarding the accuracy of the DRPX: If it turns out that the crossover point of the PRX518S is at 120hz LR12 (for example), can I set the crossover on the DRPX at 118hz LR24 without problems? or is there a chance that one
x-over might sum up with the other? Is there an easy way to tell if this is happening?
Check the upper left of the control panel.
PRX500 Amplifier Input Configuration for
PRX518S and PRX718S Subwoofer Models:
Features
1 - XOVER IN / OUT: Pressing this button engages a high-pass filter at 120 Hz. This 4th order active filter allows a smooth transition between the subwoofer and a full range speaker connected to
the output connector.
DRA
I believe that button lets you toggle between a hi-passed and a full range signal for the tops only. I have tried it already but it has no effect on the subwoofer sound.
Right this second, I just finished talking to the JBL tech rep and he told me that the filters for the PRX518S (low and hi pass) are the same: 120hz BW24. So that clears that part of the mistery.
The other part of the mistery is why when using the subs´ internal crossover (120hz BW24) I still hear the human voice but when I set my DRPX to 125hz LR24 or 118hz LR24 I do not hear the human voice or any other high frequency content. Can it be that the two x-overs are summing up?
The JBL tech rep seemed very surprissed that I was asking for the crossover information for the PRX518S, and he even asked me why I needed it and told me that no one else has asked for it. Is it really such an unusual request? He was actually very helpful and he did get me the information, though, so I´m happy. Now, can you guys (DRA?) help me with the question in the paragraph above?
I don't think the crossover settings (one or the other) are gonna make a world of difference even though you have conflicting specs. What really matters is if they are phased aligned at the acoustic crossover point and there is no way of knowing that unless you use an FFT program like Smaart. 100Hz seems to be the standard starting position. What is more important for you to do is get the system outside and go thru the flattening session described all over this forum. You can find it in the FAQ section.
I totally undertand what you are saying and it is a good reality check. Actually, I do want to thank everyone´s input.
While I don´t have any complaints about the sound quality of my setup (I know there´s better, more expensive stuff out there) I still think that I should strive to learn more about it.
Can anyone please suggest any reading material for me (I´ve read the obvious...lenard audio, rane notes, peavey, etc). I´ve been reading the postings in this forum but I wonder if there is a forum dedicated to subwoofers or crossovers.
If you want to delve into crossover theory there are a number of books on this but beware, this is an incredibly deep, and complicated subject.
http://www.mfr-eng.com/ldc.htm
http://www.linkwitzlab.com/
http://www.diyaudio.com/forums/multi-wa ... esign.html
http://www.amazon.com/Crossover-Design/dp/0956045308
You would do well to get SMAART and learn to tune your system with something that can really show you what you have done with your crossovers and filter selections...
Gadget
Hosehead -- About two years ago I was were you are at now. I bought my first Driverack and jumped on the forum here. I knew NOTHING about sound. I only knew that it should sound better than what I was hearing out in the clubs. As a musician I feel somewhat validated in saying that. Gig after gig and not really liking what I hear out of the main house system. My guitar tone (out front) NEVER sounded like what I hear coming out of my cabinet. I got sick of it & started buying a PA. Here I am two years later and feel like the improvements I have made are nothing short of astounding!
For me to not know anything was a blessing because I go to learn from the Pros right here on the forum. Stay here and learn. Read all you can. Don't listen to OLD School sound guys that insist on changing the crossover 15 times during a show and constantly fiddle with the graphic EQ. That is a rut! I have always been told that a RUT is a coffin with the ends kicked out of it & that is the truth.
You mentioned that you want to read all you can on crossovers. I did that too BUT it really isn't anything that will really make a significant difference in your sound. I mean it CAN but no matter what you read it is gonna come down to BW 18 on the subs & the LR 24 on everything else. Gadget stresses it here, you will read about it everywhere else & Bob McCarthy's book on Sound System Optimization (2nd edition) is going to say the same thing.
I read everything I could on this forum for the first year and that was awesome stuff BUT what really blew it out of the water for me was the FFT Program Smaart. It tied it all together. So at that point everything fell into place and now the only thing I have to get good at is understanding or interpreting the data coming in. That will takes years if not a lifetime to master.
Like Gadget stated: With Smaart you will see on a computer screen what turning a knob actually does & what adjusting an eq does. All in real time. When you select a specific crossover filter -- you will see & hear what that does. You will clearly see the areas of your systems audio spectrum (frequency response) & all the flaws present. Your job will be to set your crossover points, set your amplitude levels by the amps themselves or the crossover outputs or both, then align it & finally EQ it with Parametrics for a nice smooth response. In one day -- you WILL learn what weeks if not months of reading will do using Smaart. The is nothing like it & will never leave home without it.
I get asked ALOT about our sound system and how I got it to sound so good BUT when I start to explain it people shut off because I don't use any graphic EQ's and I don't fiddle with settings a whole lot so they just aren't ready for it. It is complicated in a way BUT not really. If you want to learn more about it -- shoot me PM and I can take you thru it. I am still a novice with Smaart but once I get you in shape and you want to know more...... Dennis is the guy to ask. He taught me.
So if you wanna read something that will get you to the goal -- read about FREQUENCY RESPONSE and what it is suppose to look like.
Sorry I couldn’t reply any earlier; I have been doing a bit of travelling and could not find the time.
The question about how accurate the DRPX is stems only from the fact that its crossover does something that is entirely different from what the built-in crossover of the PRX does. Frankly, though, I´ve always thought that it´s the PRX518S that´s at fault and not the DRPX.
In any case, below are my observations—for what they´re worth—and I would like to know if other PRX518S owners are seeing the same things I´m seeing (or should I say hearing):
1) JBL says that the built-in crossover on the PRX518S sub is a 24db BW filter at 120 Hz (their website has the wrong spec). With this filter I hear lots of high frequency content coming from the sub (tops turned off) when playing back music.
2) If I hook up my DRPX and choose the same filter type as in the PRX518S and lower the filter from infinity down to 800 Hz the high frequently content is considerably reduced. If I keep sweeping the filter down, I can clearly hear the high frequency content start to disappear entirely until it is all completely gone at about 150 Hz.
3) If I configure the DRPX to use a low pass 24db BW filter at 118 Hz I get nicer, punchier sound than if I just use the PRX on its own.
What the above says to me is that the crossover on the PRX518S is really crappy, and if the sub is left on its own, it will not perform nearly as well as it will with the DRPX. I will keep experimenting and post my findings here in case they can be of any help to anyone.
Thank you Dr. J, Smaart does ring a bell, and although it sounds a bit intimidating I´m going to look into it. Gadget, DRA, Dennis, and Dr. J, I truly appreciate your input. I can honestly say that what little I know, I have learned primarily here by reading your posts and your links to other sources of knowledge. You guys are certainly getting lots of respect from me, for sure. All of you are pros with the practical experience and knowledge.
And if anyone can provide me with any links to any sources of audio knowledge (mainly articles) I´ll be very thankful to you; it doesn´t have to be all about crossovers only, just anything that you think might be interesting or useful to know. Gadget, thank you for the links, you are a pal. I´m not particularly interested in the math of crossovers, I just want to know what choosing one filter over another can achieve--or ruin--for example.
We live in an incredible time where knowledge is literally a keystroke away...With a search engine like GOOGLE you can find out about just about anything you want to... medicine, physics, plumbing, and audio theory...I just typed in "A history of crossover filters" in a GOOGLE search field...and found this:
http://en.wikipedia.org/wiki/Audio_crossover
Then I typed in "Different types of crossover filters and their characteristics" and found this:
http://www.audioholics.com/education/lo ... udspeakers
Perhaps you can see that with various syntax, and a lot of patience you can find just about anything you want including how to create an atom bomb and even this:
http://www.crownaudio.com/pdf/legacy/be ... asheet.pdf
So, it's all there for the taking... and all it costs is a computer, the internet, and your time!
enjoy!
Gary
With this more detailed post explaining the problem you are having with your PRX sub, I would say the internal crossover is not functioning correctly and the sub needs to be sent in for service.
Dennis
Where does one go to get a "downloadable" FFT Program SMAART?
I'm one of those technically challenged "Old" guys. I've been reading a number of posts regarding crossover and still don't have a grasp on it myself. I own a DRPA. Gadget has attempted on many occasions to help me. I'm still in need of hands-on and visual guidance. Perhaps this program (smaart) may help. :oops:
By the way, you guys are still pumping out the knowledge to anyone who asks and does a bit of review on their own. Thanks.
I think you get a 30 day free trial
I have never listened to other PRX518S subs other than my own, and so I would like to know if others are experiencing the same thing. If others are experiencing the same thing then it may just be poor design, but the DRPX is a good solution to the problem.
Regarding my quest for reading material, I have done some googling but I keep getting very old content plus some content about super-tweeters, super-cables, and other voodoo. There have got to be more serious and up-to-date sources somewhere.
Being the novice that I am, I imagined that there would be some kind of a central repository, somewhere in the webb, with access to purest audio wisdom that everyone but I knew about. Every now and then, though, I´ll go back to the START HERE section and browse through the links Gadget posted for a review--very helpfull information there.
You said earlier that you thought the engage button on the back was for the tops that would be connected, but have you actually toggled the button while the subs (only) were playing and listened for a change? Worth a shot. You may be right, but you never know. It is JBL, after all.
DRA
What I'm hesitating... no procrastinating..no, reticent? to say... is that the science... the theory, goes back to the early industrial revolution. The bulk of the information then was mathematics and "Probability". There were no high tech drivers and systems to reproduce the sound back then so it was all theory. Theories that still hold up today.
I think your way to "sensitive" to the age of the information. Some of the concepts have never been touched and are still pretty much in tact. Why not wrap yourself around the concept...rather than the ergonomics of the subject.
I've looked at the subject and seen tenfold advances have to the driver, and cabinet optimization, without which the refinements would not be possible. But the fact is the older technologies are still at the heart of the subject.
Your not going to get it without some effort on your part. Perhaps you should not approach this with too many preconceived notions. The one most telling truth is that " the more you learn... the less you know... So don't dismiss the "old" information.. it just might be the "jewel" of the collection.
You'll get better at sensing the importance of a piece and it will get easier. For now just browse the different posts and glean what you can from all the different information.
Better hit the sack.. did sound for a killer band tonight... went well, new space, new owners...kicked butt.
Nite
G