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Old 28th May 2005, 03:42 AM   #1
jac2003 is offline jac2003  South Africa
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Question Need help with PA crossover please!!

I'm opening a bar/cafe in Shanghai and due to the very
high price of PA equipment here, I decided to build
some 2 way PA speakers myself.

We will basically need this for some solo and small
band acoustical music.

I have constructed my cabinets and have the following
componentsi include web address where you can find
all the specs and plots)

1) P Audio SN-15MB woofers (freq range: 35-3000)
http://www.p-audio.co.uk/products/db...2_sn-15_mb.htm

2)P Audio BMD-750 2" hf drivers (freq range:
500-18000)
http://www.p-audio.co.uk/products/db..._6_bm-d750.htm

I was thinking of getting Peavey ECS 1000x crossovers.
Would this work well or should I
crossover at a higher frequency?

Thanks so much!
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Old 28th May 2005, 05:48 PM   #2
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Hello!

If the crossovers are 6 db per octave units, I recommend the crossover point for the high freq. driver to be at least two octaves
above its FS, or free air resonance. I would suggest going with 12 db per octave crossovers. I was not able to connect to the website that you supplied in your text.

If you can find a frequency responce graph from the manufacturer,
take a look at where the woofer begins to roll off. You want to cross it over well before that point, especially if you are using a 6 db per octave crossover.

I have recently returned from a 5 month visit in China. In a huge city like Shanghai, you should be able to find some places that have plenty of loudspeakers and components. I know that there are MANY companies in Guangzhou that make raw components.

I am not familiar with the crossover that you mention. Is the high
frequency driver a mid range compression driver? If so, you may be able to cross it over around 1500 HZ using a 12 db per octave
crossover, if it has a free air resonance around 600 or 700 HZ.
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Old 29th May 2005, 01:33 AM   #3
jac2003 is offline jac2003  South Africa
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Default thanks!-more specs

thanks barth,

the peavey crossover is a 1k 12db crossover .
you can view it here http://www.partsexpress.com/pe/showd...number=294-325

Alternative links to view the drivers' specs:

http://www.loudspeakersplus.com/html/sn-15b-specs.html
and
www.usspeaker.com/homepage.htm

I also attach the plots here below.
The driver's Fs is 595Hz.

Hope this helps

Thanks so much
Attached Images
File Type: gif grafico_bm-d750.gif (78.3 KB, 162 views)
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Old 29th May 2005, 01:33 AM   #4
jac2003 is offline jac2003  South Africa
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Default and here is the other plot

the plot for the low freq driver
Attached Images
File Type: gif grafico_sn-15_mb.gif (93.0 KB, 158 views)
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Old 30th May 2005, 04:12 AM   #5
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After looking at the freq. graphs, and if it were me with this project, I would set the crossover point between 1,500 HZ and 2,000 HZ. And I would use a 12 db per octave setup. You can risk going with the Yamaha crossover at 1,000 HZ, but I think that it is too close to the free air resonance of the high freq. driver. If you cross it over below 1,200 HZ then I would suggest having 18 db per octave, to protect the high freq. driver.

How much power will you be using with this set up ? And will you also be using it to play regular music from a stereo as well as a small P.A. system ?

If you can look around at more crossovers I would suggest this.
Also, if you have internet access, go to google.com and search for the MCM Electronics website as they also may have some decent high power crossovers available.

You may also want to consider to actually build your own crossovers, if you have the time and desire to learn about how to do it. I can suggest some websites that freely supply charts and information about which components to use.
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Old 30th May 2005, 04:34 AM   #6
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Quote:
Originally posted by barth2102
Also, if you have internet access . . .
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Old 30th May 2005, 05:40 PM   #7
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Hi

Jac if the price is of importance , there is a cloned JBL cross - over available , it is intended for the P-Audios , I think it has been made by Nasa but am bot sure

A lot of P- Audios are used here , and the Cross - over I am talking of come from - Thailand or China I am sure if it is easily available here it might be there too

The clone has 5 Large resistors across the board - and the PCB is not a direct copy - though the entire circuit is more or less JBL

It has been made for P - Audio and Jbl has been the target as P - Audio has a 2226 model ,

If you need more help with this cross - over i will find out the price and the manufacturer though I am sure of the source is quite close to Thailand or China - and you will find it available there - only at first look it will not look much attractive due to the finish but actually it is clonish of a very expensive & good cross over

Suranjan Das Gupta
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Old 31st May 2005, 05:00 AM   #8
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Yeah, sorry about the bobble regarding the internet access. But I seem to remember that MCM Electronics had some decent high power crossovers. There was one unit that I remember seeing that was 12 db per octave and the crossover point was 1,600 HZ.

Go to google.com and type in MCM Electronics website, and you should find some results there.

How much power will you be using with the speakers? And what type of design will you use for the speaker cabinets ? Bass reflex? Front loading horn ? Perhaps the speaker manufacturer
can suggest a proper internal cabinet size and configuration.

This is important because, if the woofer is mounted in a box that is too large or too small, and the bass reflex port is too big or too small, it can have a serious impact on power handling capacity and overall performance.

Where in Shanghai is your new club?
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Old 31st May 2005, 10:05 PM   #9
djdan is offline djdan  Romania
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This crossover schematic is a special design for this speakers . It was designed by me , few years ago and is used for my pro- loudspeakers .

It work very well and it have a to step driver protection
( non-intreruptive ) .
Attached Images
File Type: jpg schema filtru sn-15 si bm-d750.jpg (81.0 KB, 157 views)
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Old 1st June 2005, 03:15 AM   #10
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Jac, I received the MCM Electronics catalog today in the mail. On page 118 there is a crossover that I think will work for you. It is 18 db per octave and the crossover point is 1200 HZ. It is for use with 8 ohm drivers. I think that you will probably have decent protection using 18 db per octave units at two times the resonance frequency of the high end compression driver, as its
FS is 595 HZ. The part number is :

50-5411

Cost is $49.50 USA money per unit. The toll free number for MCM Electronics is :

800 - 543 - 4330

Their website address is:

www.mcminone.com
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