Possible Weird setup?

DJ Jim Kelly

Guys, I'm really new to this site and a rookie at setting up a PA. I just bought a DRPA off some guy on Ebay. I have a few ?'s

1) Are there any differences in the \"presets\" that came with older model DRPA's from the newer ones? I know it kinda obvious, but I have like maybe a 1/3 of the presets(amps & speakers) listed than the online manual. Also, how would I know if my DRPA is functioning correctly? Are there any \"known\" issues I should know about regarding the oldest model?

2) I'm running a 2-way setup for \"music\" playback. I have 1 QSC RMX 2450 powering 2 JBL TR225's. I have 1 QSC RMX 4050HD Bridged, powering a Wharfedale Pro MX-218B sub. Does anyone know the correct settings to be entered on the DRPA? Im guessing my DRPA is OLD, because it basically only goes up to the old Crown CE series amps?

Thanks,
Jim

Gadget

In my opinion the presets are less than useless anyway unless you are using Bi-amp tops... which you are not... the Gain structure will set your amp input levels anyway so no need to worry about that, and if you did \"need\" to use that method amp manufacturers provide input sensitivity specifications you can implement manually...

The cable that runs to the meter works it's way loose and needs re-seating from time to time .. the display starts acting up

There has been some trouble with the displays themselves.. I have no % info.

There is a nasty \"THUMP\" if power is cut or the unit is turned off prior to the amps, The solution is to bypass the power switch(pervents inadvertent turn off), and get an inexpensive UPS (un-interruptible power supply) that can run the DRPA for a few seconds while the amps shut down...(under $50)

There are NO correct settings, but if you read the FAQ's you will get a leg up on the tuning process...The limiting factors here are
1. Speaker size and frequency response @ -0- b down
2. the amount of power available for the tops

The specs show the TR225 10 db down at 50hz...(ridiculous...) I have had some experience with these (and I'm sorry for my words here but... I am so disgusted with JBL I could just scream!!!!) horrible little monsters.. and I don't mean monsters in a good way...These speakers suffer the ignominy of being THE shortest lived product in JBL history! I don't think they lasted a YEAR in the production line! I bet those nasty little buggers don't go much below 100hz...You have plenty of power to do harm to those \"things\" so I guess 108.1 hz... give or take( maybe 120 hz would be better here since these things are so.. oh well I won't say any more...)...LR 24 Subs... The sub woofers on the other hand would seem to be good ones...The 3db down point is 45 hz so I guess I'd set an HPF of 45 hz BW 18, 50 hz outdoors, cross the sub slightly below the tops.. say a 5-15 hz spread.

Now, as for the combination.. those tops will be crushed by that sub... NO way they will be able to keep up... I would get the RTA mic and see if the tops can be tamed any with the limited abilities of the DRPA...Sorry.. don't mean to belittle your setup but those things... I won't say any more...

Good luck, you'll need it...

Gadget

DJ Jim Kelly

Thanks for the info Gadget! I know the tops are gross (didn't realize it until I hooked them up...NO BASS AT ALL) but I have a limited budget. What tops should I be running based upon my gear?

Jim

Gadget

The lowest I'd even consider are the Peavey SP 2's ... the newest version... they are about $500 each... but I saw some 'B' stocks somewhere in the $300 area...They are at least pro Quality..I just can't stand the new JBL stuff.. it's like they are riding on their reputation and just don't care... the Yorkville stuff is good, Community, and some others, but not the lower line stuff...by anyone...
Gadget

DJ Jim Kelly

Gadget,
I got rid of the TR225's and replaced them with Whafedale Pro LX-215e tops. I also got another QSC RMX 4050HD bridged that is powering another Wharfedale Pro MX-218 sub. My question is how low do I run the crossover to the tops? Here is a recap of my setup:

1 QSC RMX 2450 powering the LX-215e's
2 QSC RMX 4050hd's powering TWO MX-218 subs.

Thanks,
Jim

Dra

Going to turn this around on you. What do you think, based on looking at the responses and speaker size, the filters should be set at?
SUB:
HPF______hz ______filter type and slope
LPF______hz ______fitler type and slope
TOPS:
HPF______hz ______filter type and slope

DRA

DJ Jim Kelly

DRA, thanks for the riddle! But, if you read, I got new tops and wanted the settings to optimize their performance. As Gadget pointed out about the TR225's, the speaker specs can't be trusted! That's why I want people with experience to chime in. Ofcourse I could play around with the settings until I get one that sounds right, but I don't have the time. That is why I posted the question. :roll:

Fanman20

Dra is just asking for your thoughts.

Give it a go, what do you think would be the right settings :?: :?:
I know he will be willing to help if you are not exactly right.

Being \"not exactly right\" is OK. 8)
That's a part of the learning process that we are trying to do here.

It's a learning experience. :idea:

Mark

PS

1 QSC RMX 2450 powering the LX-215e's
2 QSC RMX 4050hd's powering TWO MX-218 subs.

\"Sounds\" like a nice setup now

Plenty of bottom end. (That what I like to \"feel\")

Speakers
http://www.wharfedalepro.com/Default.as ... 7&IdLang=1
Amp
http://www.qscaudio.com/products/amps/rmx/rmx4050.htm

Lucky boy 8)

.

Gadget

See my reply this post...
http://www.dbxpro.com/forum/viewtopic.p ... highlight=
G

Fanman20

OK Dra
I will give it a go

Tops
LX-215E
Freq 40-20kHz

Subs
MX-218B
Freq 45-250Hz

Considering plenty of sub amp power, Cross 106 hz
Leaving say 3hz on either side of the cross over point for the slope

So

SUB:
HPF 50hz Butterworth filter 18dB/Oct
LPF 104hz Linkwitz-Riley filter 24dB/Oct

TOPS:
HPF 110hz Linkwitz-Riley filter 24dB/Oct

Or there abouts :roll: :?

My question back is
What is the number of hz to leave on either side of the cross over point to obtain a -6db “Bessel“ crossover point???

Formula
Linkwitz-Riley 24dB/octave (Q 0.5)
Therefore 24db divided by 6db = 4

Or a 1/4 of an octave

1/4 of an octave = ??hz


Quote from http://www.lenardaudio.com/education/06_x-over.html

Linkwitz-Riley. Professional electronic crossovers, referred to as Linkwitz-Riley, have fixed slopes, fourth order, 24dB/octave (Q 0.5) and -6dB at crossover point (Bessel)

The steep 24dB/octave slopes give maximum protection, control and power capability for the drivers.

Where is Kev???

Dra

1/4 of an octave = ??hz

I'll take a stab at it.
1 octive is a relative term (like aunt or uncle 8) ) and is the span from any given frequency (A) to the doubling of that frequency (B) or (2A).
Let's place the proposed x-over point close to the middle of the octive.
The octive will be from 70hz - 140hz, with a span of 70hz. So 1/4 octive in this octive is ... 70hz*.25=17.5hz. (or there abouts)

Am I correct?

You're showing a 6hz gap.

5 possibilities.
1) I'm right.
2) You're right.
3) We're both wrong
4) We're both right (within reason) because it is not that critical.
5) All of the above and Gadget will tell us why.

Now a question back. Do one-pot analog crossovers automatically adjust and compensate to achieve \"the gap\" whether at 60hz or 600hz?

DRA

DJ Jim Kelly

Thanks Gadget, Fanman, and DRA....I guess I jumped the gun when I read your reply...sorry bro! :oops:

Fanman20

That's OK DJ Jim Kelly
It's all in the learning.

Now for Dras question.

Do one-pot analog crossovers automatically adjust and compensate to achieve \"the gap\" whether at 60hz or 600hz?

I think that I am nealy positive that maybe it well could be an mostly true statement / question

unless you are wrong.

And in that case you are on your own


Gadget stated in another post

spread the xover point a few hz and use a hipass of LR 24 for the tops...

Information is hard to find in regards to what \"a few hz is\"

Still google'ing this point

Mark

Gadget

No, you didn't jump the gun, we just want people to think, and read. Knowledge is power. The axiom that applies here though is \"The more you learn the less you know\", but if we give everything out on a silver platter you don't learn anything right?

As for the other things, Xovers are a necessary evil. In a perfect world speakers would be able to produce 20-20k and with only one element. Audiophiles have known for some time that the most transparent speakers are the ones that do use one driver to reproduce all the sound, but they don't get very loud, and wouldn't be able to do live sound at all.

Digital crossovers and equalizers exhibit the same characteristics as their analog counterparts, and that means that they induce phase shifts, and frequency anomalies and that sort of thing, and the more complex the network the more problems are associated with it. In digital networks we also now know that propagation delay is also present and needs to be dealt with. The thing about the crossover spread is that it's different with every type and slope so sound being subjective, and digital xovers being so easy to manipulate, I recommend experimentation. Plain and simple, just try a few hertz , add or subtract and see what gives... Remember that the crossover region will probably be need some PEQ treatment, and again experimentation will yield the best results, so you math types can have at it... but hypothetical results will never beat real world tangible results garnered through good old fashioned knob turning and listening...

Thats my $.02

Oh and Kev is a busy man these days...but he's with us in spirit...

Gadget

DJ Jim Kelly

I gotcha. But since I'm using my sound reinforcement for music playback and quality varies with MP3s, am I screwed? Where do I get \"test CD's\"?

Dra

http://binkster.net/extras.shtml#cd

This link is listed 2 times in the section we have asked you to read.

DRA

DJ Jim Kelly

Thanks!