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XM15 build happening right now - advice appreciate

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Mark'n'Greg View Drop Down
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    Posted: 30 May 2007 at 1:46pm
We're building one or two XM15 monitor boxes and we're considering loading with the following, which apart from the horn type is the exact spec of some Martin-style boxes that I use regularly

B&C 15PK40 15"
http://www.bcspeakers.com/download/prodotti/PDF/more/122.pdf

B&C DE25 1" comp
http://www.bcspeakers.com/download/prodotti/PDF/more/133.pdf

B&C XO-3 1.8kHz crossover
http://www.bluearan.co.uk/menu/index.php?id=BACXO3&browsemode=manufacturer

B&C ME45 horn http://www.bcspeakers.com/index.php?sez=1&categoria=5&id_descrizione=47&prodotto=89

As well as being monitor boxes, we're hoping to put pole-mounts in for use as mains. How do we work out where exactly to put the pole-mounts for most even weight distribution? Are these horns suitable? Is the whole thing doomed to disaster? Please leave your comments or just stay tuned for the unfolding drama...

mark
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ceharden View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ceharden Quote  Post ReplyReply Direct Link To This Post Posted: 30 May 2007 at 9:36pm
Looks good.  I would possibly consider going for a constant directivity horn rather than the B&C which is a pure exponential.  Especially for wedges, it matters less about an absolutely flat response (you're going to EQ it anyway) and more about it being the same over the coverage area.  The 18Sound XT1086 is good.  The P-Audio PH220 as recommended on the plan is an RCF copy and also a good choice.  Within reason a larger flare, especially with a 15" on the low end will be better.

The B&C drivers you mention are no longer in production so I assume you have them available to you already.  DE250 is the modern version of the compression driver which is even more nails than the DE25!

The crossover is dedicated to the 12CX32 so maybe not the best choice.  I've taken to building my own because I couldn't find any suitable ready-made ones.  You need one around the 2kHz mark.  Ideally with a 15" driver you want the crossover a bit lower but a DE25 won't really like going below 2kHz.  A DE250 will go down to 1.6kHz however.

Sorry, that turned into a long ramble but I've been building quite a few of this type of cab recently.

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Mark James View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mark James Quote  Post ReplyReply Direct Link To This Post Posted: 31 May 2007 at 5:49pm
sound like hed apreciate the advisinng rant
and you are pretty much the right person to reply
Silly sentence!
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Mark'n'Greg View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mark'n'Greg Quote  Post ReplyReply Direct Link To This Post Posted: 31 May 2007 at 9:44pm
Thanks for taking the time, ceharden.

It's an interesting point about the exponential horn thing, but I've seen and used a lot of monitor boxes with them, and I couldn't say for sure that I've ever used non-exponential horns (I don't get the time to rip the boxes apart in every venue that I visit). Also, these boxes are going to double as front speakers. I'm still thinking of going for exponential but could be persuaded otherwise.

Which B&C driver should we substitute for the 15PK40? There are a few of the old B&C 15"s and 1"s still on sale, although I'm also considering the P-Audios, as in the original XM15 spec. The one thing I can't find any reference to on t'net is the "PAP VXM 2K3 crossover" -  if someone would be so kind as to point to a vendor or a circuit diagram, I'd be very happy.

Well, the basic boxes have now been cut, screwed and glued. It was a  hectic mission to find some wood. B&Q and Wickes (in north Sheffield) were both utterly useless so we headed down Arnold Laver at the south end of the city and picked up two 1220x2440 sheets of 11-ply 18mm for 27 each including 4 cuts. Tomorrow if we get time we'll fill the holes and discontinuities in with resin!

Also, i'll see if i can find a camera at some point.

mark
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Andrew View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Andrew Quote  Post ReplyReply Direct Link To This Post Posted: 31 May 2007 at 11:42pm
Fill the holes?
 
I got my 90 degree cuts done at the timber yard and got a friend to make the mitre cuts for the back. Everything was glued and screwed from the inside.
 
I started this technique when I had to repair a classic 12" reflex box, you know, the ones with the slot along the bottom.  The box needed reinforcing, but was already covered in vynal.
 
Next time on a monitor build I will try doing the spliced mitres, so that none of the end grain is visible around the cabinet.
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Mark'n'Greg View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mark'n'Greg Quote  Post ReplyReply Direct Link To This Post Posted: 01 June 2007 at 1:55am
Spliced mitres? huh? That's technical jargon to us, we're doing it with a tiny workbench and a rough as hell circular saw, just for fun 'cos we're both off work for a couple of days. Although, that said, if they turn out OK we will use them for the odd small event here and there.




Edited by Mark'n'Greg - 01 June 2007 at 1:56am
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Mark'n'Greg View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mark'n'Greg Quote  Post ReplyReply Direct Link To This Post Posted: 09 July 2007 at 5:21pm
n00b time.

Could somebody please have a look at this page for us :http://www.proaudioparts.co.uk/hwpricelist.asp and tell us
(a) Which (if any) of the crossovers listed is the one we need (a "PAP VXM 2k3" according to the plan)?
(b) What's an L-pad? Do we need one for an XM15?

cheers!


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mucsavage View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mucsavage Quote  Post ReplyReply Direct Link To This Post Posted: 30 August 2007 at 12:08am
Mark'n'Greg!

Did you get this going?

I am planning to make some of these for a first time build and confused over the cross over like you were....
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Mark'n'Greg View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mark'n'Greg Quote  Post ReplyReply Direct Link To This Post Posted: 30 August 2007 at 1:45pm
Yes, we built the speakers, they just need some padding and rattle-hunting and they'll be done. Pictures to follow hopefully. When I've run out of things to do in the garden.

For the crossover, I just told the guy what I was building over the phone and hoped for the best. I got 'VXM crossover' at £38. Well, the speakers work, the frequency resp seems reasonable over mids and highs although there's a definite lack of bass response, maybe that'll improve when I get some padding in there and get the drivers properly run in.



Edited by Mark'n'Greg - 30 August 2007 at 1:54pm
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ceharden View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ceharden Quote  Post ReplyReply Direct Link To This Post Posted: 30 August 2007 at 9:07pm
Which drivers and horn did you end up with in the end?

The cabs are not designed to produce any real bass, they're monitors or mid-tops.  You can persuade them to give you a bit more with some EQ but be careful not to use too much otherwise the driver will over-excurt. If you can, use a high pass filter around 50Hz to remove any real low end that the box can't produce.


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Mark'n'Greg View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mark'n'Greg Quote  Post ReplyReply Direct Link To This Post Posted: 12 September 2007 at 10:37am
Originally posted by ceharden ceharden wrote:

Which drivers and horn did you end up with in the end?
The cabs are not designed to produce any real bass, they're monitors or mid-tops.  You can persuade them to give you a bit more with some EQ but be careful not to use too much otherwise the driver will over-excurt. If you can, use a high pass filter around 50Hz to remove any real low end that the box can't produce.


Oh aye, I don't expect to hear anything much below 60Hz, and I'm certainly not going to try feeding them sub-bass frequencies. I went with the original Mogale spec in the end, P-audio SN15MB etc. Interestingly I recently modelled the XM15 in WinISD and got very different results from Rog - an fs of something like 100Hz as opposed to the 60-something in the plan. As winter takes over I'll probably remodel them and post the results here so we can figure out where I'm going wrong.

They're being used for a small singer/songwriter acoustic gig this friday, one for FOH and one for stage monitor. Gotta get those rattles tracked down first. Hey, does anyone else use draught excluders to stop rattles and seal gaps in their speakers?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote kevin tyler Quote  Post ReplyReply Direct Link To This Post Posted: 13 September 2007 at 3:57pm
re your question about top hat placement, not sure if you know this but, to figure out where to put top hats, balance the  loaded box on a small tin of paint can of beans whatever, where ever you find the box is at its most stable, fix top hats there.
 
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