Two-way PA speaker for a band...

turk 182

Member
2012-10-26 3:03 pm
not asking for much for free are you.
any make and model on the ribbon tweeter your planning on using?
do you have any response measurements of the drivers in the cabinets?
is any baffle step correction planned?


as this is intended for PA use are you mic'ing drums?
 
The BEST thing you can do for a P.A. system is BI-AMP it:
BiAmp (Bi-Amplification - Not Quite Magic, But Close) - Part 1
This will lower the distortion heard by your audience NOTICEABLY.

Altough i'm a huge fan of analog and passive crossovers, for P.A. a DSP (speaker managment) and seperate amp for top and bass is indeed the best. Passive crossovers on this powerlevel is very hard to do and extremely expesnive (becasuse the parts need to be able to handle a lot of power).

Get a good dsp (like the DBX Driverrack) and seperate amps, and this will be much better than any passive crossover. If you want to stay analog, you can also have an analog active crossover, but those are rare, especially to use on big high power systems. DBX makes a decent basic one, and there is probally more also.
 

Sven R

Member
2011-04-16 6:48 am
not asking for much for free are you.
any make and model on the ribbon tweeter your planning on using?
do you have any response measurements of the drivers in the cabinets?
is any baffle step correction planned?


as this is intended for PA use are you mic'ing drums?

Well, if you are not inclined to be of assistance, that is fine... I have done much in my life for free, but that is my own attitude... well, having in mind the way things are happening, if one is to look at the cost of design, paying for a design is not excluded in my case...

The ribbon I am looking at is SA8535 by a company I know of for three past decades... ever since I worked in the USA as Sound Engineer, I used ribbon H.F. in studio monitoring, so one rare company that had ribbons powerful enough for PA, is exactly the one that made the above mentioned H.F. unit. It is 60 Watt RMS constant, with peaks up to 1000 Watt (duration is whopping 200 ms!).

This PA is to be used for clubs that have 100 to 400 people in the audience, no heavy rock, no ¨head-banging¨ music and such, just excellent sound for an excellent trio (guitar-bass-drums)!

If I decide to mike all the drum kit (not needed in most clubs here, except that a kick drum could use a mike, a bit of compression and some gating...), so I am pleased with low end not going below 65 Hz or so (bass guitar is NOT run through this PA!).

I am 100% for ALL ANALOG signal chain... whole my life I respected and liked only such sound (although digital has its superiorities galore... but, that's the way us old folks are, sometimes...).

Well, hope this helps...
 
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turk 182

Member
2012-10-26 3:03 pm
analog active crossovers rare!?

since dsp is displacing so much analog tech there's buttloads of of BSS fds 360's, Rane AC22's Ashly XR2001's but that's all product intended for PA use, if your trying to find active analog x-over's that where intended for home stereo then yes they are rarer then hen's teeth!
 

Sven R

Member
2011-04-16 6:48 am
The BEST thing you can do for a P.A. system is BI-AMP it:
BiAmp (Bi-Amplification - Not Quite Magic, But Close) - Part 1
This will lower the distortion heard by your audience NOTICEABLY.

Thanks for your good advice... however, this is for small clubs (100 to 400 people max.!) and dragging around extra amplifiers and additional subs would be too cumbersome... For larger audiences, for more power and such, your advice would indeed be implemented. But this is for local clubs and rock music that is not loud... Once again, thanks for consideration and advice ...
 
analog active crossovers rare!?

since dsp is displacing so much analog tech there's buttloads of of BSS fds 360's, Rane AC22's Ashly XR2001's but that's all product intended for PA use, if your trying to find active analog x-over's that where intended for home stereo then yes they are rarer then hen's teeth!

The hen has an implant at least, however it's selbstbau;)

Rant off (topic)
 

AllenB

Moderator
Paid Member
2008-10-18 11:31 am
Here are links to the drivers.

Sven, your crossover at 1k4Hz is close to the first breakup peak at 2150Hz, just over half an octave. You might need a filter of high order to deal with it. So two questions come to mind in allowing such a filter, what is the driver offset (depth distance between woofer and tweeter), and what filter does it take to protect the tweeter at the levels you want?

pdf.gif
RCF SPECSHEET-ENG-MB12N301.pdf
pdf.gif
SA8535_techdoc.pdf
 
Greetings,

I am making two PA speakers for a medium club, for my music band. They are to be 2-way speakers, with low end handled by one RCF MB12N301 – 8 Ohm, a 12¨ bass/mid-bass woofer, with Neodymium magnet. High end is to be handled by a PA ribbon speaker attached to a cast metal horn (70x30 degrees -- horizontal x vertical distribution).

I need someone who would design a passive crossover for this speaker (schematics and layout) – with top notch components (no need to save money here, it would be stupid). That is number one, while an option number two would also include building those two devices, to be installed in two speaker enclosures that I am making (each a vented enclosure with almost 40 liters of internal volume, tuned to 65 Hz, with one rectangular port).

Crossover frequency is to be 1,4 kHz. Minimum crossover slope should be 12dB/octave. It would be better if it would be 18dB/octave if no major losses are incured (12 or 18 dB per octave - debatable?).

Peak power that both those drivers can handle, short term (perhaps 100 msec?) is 1000 Watts RMS, but I shall never drive them that hard, rather, they are to have peak power at about 500 Watt RMS (AES standard, let us say), but that is tops, while they are actually going to be driven by an excellent Crown stereo power amplifier that delivers two times 350 Watt into 8 Ohm. The 2-way speaker should be 8 Ohm, as seen by an amplifier. The woofer is nominal 8 Ohm, while H.F. ribbon driver is nominal 13 Ohm, but when together in an enclosure and finished, wired, they should be 8 Ohm speaker. Crossover should have protection bulb and other nice features, but it does not have to be ¨studio Hi-Fi perfection¨. It is a speaker for club, for a rock band (not too loud, not heavy rock band... just beautiful sounding band).

For people who know how to do it, it should not be difficult. Learning curve is big for these free softwares and I do not plan to do any more crossovers, so it would be best if someone helps. Could anyone help? Thanks for reading this, give it a consideration. Sincerely, Sven R.

Some thoughts and concerns, from someone that's been doing PA systems for a while:

- Ribbons don't like to be driven low or loud. The 1000w 200ms peak is something that the driver might (might) survive once. Or twice. The 60w continuous rating should be respected.
- You're going to need more than a pair of 12" midbass drivers to do the kick drum any justice, especially for the audience size you're talking about.
- The Crown amp you've chosen will leave performance on the table. If it was mine, I'd be looking for something that'd do >600w into 8ohm.


It's difficult for me to understand how you can confidently come up with all these specifications for your crossover, while being unable to design a crossover.

It seems to me like you need a consultant. Where are you located?
I have some ideas on what would make your speakers work well, but they are contrary to some of your ideas.

This is a job that'd take a few days to pull off well. First day would be spent with a measurement mic (and the cabinets built, with the drivers installed), and then perhaps half a day designing the crossover, and then order parts, and then build, test, and EQ the thing.

Studio-perfect sound can be achieved from a PA system. Mine usually do a pretty good job.

Chris

PS - On a different note, the best PA system in the world will sound pretty mediocre if your microphones etc aren't up to scratch.
 
I agree with the post above, but still made some fast (10min) modelling with the curves from the spec sheets (traced in virtualcad, modelled in xsim). This is a very basic 2 way 2nd order crossover that could work in your setup. But to find the inductors that can handle the powerhandling you need, will be hard. You need coils that can handle 1000w at 4.7mH for this. One i know of good quality is a Mundorf L300 4.7mH air coil, and in that spec it cost 220€ a piece (you need 2 of them, and that is only one part of it). Other parts will still be expensive, and i guess your CR may cost more than 500€ per side... It will also ad a lot of weight. I also added the project and the frd and zma traces i made (the software xsim is free downloadeble).

Disclaimer: This is not a finished cr, this is a rough prestudy. Use at own risk.
 

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Sven R

Member
2011-04-16 6:48 am
I agree with the post above, but still made some fast (10min) modelling with the curves from the spec sheets (traced in virtualcad, modelled in xsim). This is a very basic 2 way 2nd order crossover that could work in your setup. But to find the inductors that can handle the powerhandling you need, will be hard. You need coils that can handle 1000w at 4.7mH for this. One i know of good quality is a Mundorf L300 4.7mH air coil, and in that spec it cost 220€ a piece (you need 2 of them, and that is only one part of it). Other parts will still be expensive, and i guess your CR may cost more than 500€ per side... It will also ad a lot of weight. I also added the project and the frd and zma traces i made (the software xsim is free downloadeble).

Disclaimer: This is not a finished cr, this is a rough prestudy. Use at own risk.

First of all, THANK YOU for taking time to make a ¨test run¨ and some serious suggestions! Wow, you made me think, hard... this is cost prohibitive, that is for sure... On the other hand, I have seen a B&C company suggest the following X-over for just about the same 2-way speaker... with much less difficulties with the parts... look at the attached file, one of those pages has a schematics of their crossover, passive one, of course... What do you think of B&C X-over on page 5 of this attachment, for a very similar speaker?!
 

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First of all, THANK YOU for taking time to make a ¨test run¨ and some serious suggestions! Wow, you made me think, hard... this is cost prohibitive, that is for sure... On the other hand, I have seen a B&C company suggest the following X-over for just about the same 2-way speaker... with much less difficulties with the parts... look at the attached file, one of those pages has a schematics of their crossover, passive one, of course... What do you think of B&C X-over on page 5 of this attachment, for a very similar speaker?!

It's hard to tell without the measurements of the speakers (other than you use, but similar layout) build into the cabinet. But they use a similar layout, and added 2 filters to filter out some peaks i think. The Lpad i put in (to attenuate the ribbon) is replaced by some lamps in this circuit.

What you need to do when you are serious about this, is build the speakers, measure them right in their cabs, and then use those measurements to design it like i did with traces of the graph of the drivers from the spec sheet. That is the only way to get an accurate crossover. But remember, the parts, especially the coils, will be very expensive because they need to be able to handle a lot of watts (here you need to take the peak power as guide). You can use that Xsim software i mentioned, that is a very goood package and it's free. Others are Virtual Cad (also free, but harder to work with). You could crossover higher than i did (wich means smaller coils), but they parts will still be very expensive...

It's just easier to go with a good DSP on this level, and with high power systems, the sound is not as detailed so you won't really hear it. But i know what you mean, i also love analog crossovers more than dsp, but only on low power systems.
 
Couple more thoughts:

- DSP is really useful - you can apply limiters etc. If you don't want to lug a load of amps around, the cheap solution is a Behringer NX4-6000 and a DCX2496. [email protected], plus lots of processing. A bit more up-market would be a Powersoft T304, which gets you FIR processing, way more power, and lots of clever limiting.
- The crossover frequency really needs to be in the 1.5-2kHz range.

Chris
 

Sven R

Member
2011-04-16 6:48 am
Here are links to the drivers.

Sven, your crossover at 1k4Hz is close to the first breakup peak at 2150Hz, just over half an octave. You might need a filter of high order to deal with it. So two questions come to mind in allowing such a filter, what is the driver offset (depth distance between woofer and tweeter), and what filter does it take to protect the tweeter at the levels you want?

pdf.gif
RCF SPECSHEET-ENG-MB12N301.pdf
pdf.gif
SA8535_techdoc.pdf

How precise the measurement of the depth has to be? If it is not extremely precise, than one could take that the depth of the center of the woofer cone on L.F. and the the depth of the ribbon inside the horn on the H.F., is just about equal. As for a breakup frequency being too close (half an octave), well, I see a justified concern... the H.F. unit can theoretically go down a little lower, but I really think that 1,4 kHz is a good frequency from the musical point of view, which is my view (of course, people can have their opinions, but I always liked to make a dip in live PA at about 1,4 kHz region and also it is a range of harmonics that should not be ¨smeared¨ with lower cross-over frequency, while going higher is not desirable, as you clearly have stated it!). So, what slope are we looking at? 18dB/octave? Well, going a little bit lower, such as 1,35 kHz (favorite very old school JBL X-over frequency) or 1,30 kHz, would not make much difference anyway, so pretty much, it is 1,40 kHz (an X-over freq. recommended by H.F. unit makers!).

One other point, tied to a Chriss 661 suggestion of ¨air coils¨ that are very expensive, I wander if some ¨iron core¨ coils could be used, less expensive and such? Pardon my errors of judgement, since here I am walking on a thin ice... :confused:
 
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