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B Mo View Drop Down
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    Posted: 20 May 2005 at 10:03pm
Does anyone know what happens when you eliminate the baffle and front load the driver in the space currently reserved for the access panel in the HD 15 horn ? 

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Disco Stu Quote  Post ReplyReply Direct Link To This Post Posted: 21 May 2005 at 2:32pm

er im not sure I understand what you mean do u mean mount the driver in the baffle from the other side making the access panel on the back wall?

 

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Post Options Post Options   Thanks (0) Thanks(0)   Quote B Mo Quote  Post ReplyReply Direct Link To This Post Posted: 21 May 2005 at 2:49pm

I was thinking of eliminating the baffle altogether and mounting the speaker where the access panel is now... facing outward.  I would aim the front of the speaker at the audience and use the horn-assist segment as a 4th order band pass filter... I think... I'm afraid I'm just not enough of a designer and mathematician to figure this one all the way out !

My original thought was that there are several affordable 15" coax units available that would reach awesome SPL's (with somewhat predictable pattern control) for very little investment - if the advantages of the 'short horn' could be assimilated into the design ?

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Disco Stu Quote  Post ReplyReply Direct Link To This Post Posted: 22 May 2005 at 10:36am

Is this what you mean ?

If so where is the rear of the driver going except into the ground?

Youd either have to extend the cabinet downwards to create some weird scoop thing which has been done before or i suppose if the cabinet was placed on the floor and raised up on some short 6 inch or so legs, the floor would help with boundary loading to increase the perceived mouth size and lower the cutoff

Are you thinking of this for Hi fi or PA use?

Stu

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Disco Stu Quote  Post ReplyReply Direct Link To This Post Posted: 22 May 2005 at 10:40am

here is what i mean about the scoop

Stu

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Post Options Post Options   Thanks (0) Thanks(0)   Quote B Mo Quote  Post ReplyReply Direct Link To This Post Posted: 22 May 2005 at 1:06pm

Yes !  That's it !  You are a mighty and patient person for dealing with this beginner... thank you, DS ! 

I was thinking of simply flipping the whole box on its side in order to avoid the weird scoop thing.  Since bass is supposed to be omnidirectional, I didn't think it would matter if the horn fired at a ninety degree angle to the speaker... ?

I was hoping to use one or two pair of HD 15's per side for a small band PA.  I read 'horm vs. reflex' in the FAQ section and I'm very familiar with the standard 218 bottom/215H top box config.  However,  in terms of SPL delivered in return for for size, weight and power requirements, the HD 15 seems to be unequaled.



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Post Options Post Options   Thanks (0) Thanks(0)   Quote Disco Stu Quote  Post ReplyReply Direct Link To This Post Posted: 22 May 2005 at 4:55pm

Mighty and patient i think not!

Anyway

I havnt a clue what the output of that thing would end up being but my concerns would be these:

  • Horn output starts to get directional quite soon above 100Hz and therefore the mid bass notes would be being directed all which ways.
  • 2ndly I would be quite worried about getting feedback because of this - if it was for Dj use it wouldnt be a problem but seeing as its band PA....
  • Scoops of any sort even this sort of design will have an uneven response and could well create some nasty peaks or honkyness in the bass end. A horn is designed the way it is for good reason. It will definitely DO something..what i dont know is what. The only way to find out would be to build it.
  • I would definitely say though that having the horn mouth facing downwards would help it do whatever it will do because it acts as a sort of horn mouth extender so i would keep the idea as the first pic i posted if you do end up actually building it.

Alternatively other cabs of similar size that have had pretty good responses are:

Bill fitzmaurices tuba subs www.billfitzmaurice.com

Staipers ES18BPH http://groups.msn.com/SpeakerBuildingpics/shoebox.msnw?actio n=ShowPhoto&PhotoID=19

They are very different beasts the tubas cost a small amount to download but i would go for a tuba 30 over a tuba 24 if you do as the recommended drivers are easier to get hold of if you live in the UK and of course you can get a higher maximum output. The tubas are a bit more fiddly to build than staipers plan but staipers plan is a bigger version of the HD15 essentially and as such has a bit more extension and a bit more grunt

Stu

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Timber_MG Quote  Post ReplyReply Direct Link To This Post Posted: 22 May 2005 at 5:01pm
To be fair he wanted to use co-ax drivers. To realize beneits of horn-loading you need a large mouth and a stack of co-axes won't exactly integrate nicely. Methinks it might be wiser to go multi-way or if you are really keen just go bass-reflex (if you're lookign for that small a cab)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote freddyi Quote  Post ReplyReply Direct Link To This Post Posted: 24 May 2005 at 11:42am
sounds like resulting scoop would be close to JBL C34 - might help to use slower flare - more like hyperbolic

C34 http://www.lansingheritage.org/html/jbl/plans/C34.htm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote B Mo Quote  Post ReplyReply Direct Link To This Post Posted: 24 May 2005 at 12:03pm

Actually... I don't have the acumen or the computer resources to accurately determine the response of the resulting horn/band pass device.  I would lose the bent wood altogether in favor of a piece of treadplate - simply bent to the spec required and routered into the sides of the plywood - to maximize the bass response of a specific speaker in the available enclosure.  If I could lay hands on the math.

With this in mind, how about a 12" coax in the same enclosure ?

It's just that I love the 'horn sound' and the efficiency is irresistable to a guy who often has a single, 20 or 30 amp circuit to run the whole show on !  I think I'll take Stu's advice and build one for the sake of experimentation.  If nothinkg else, I can just make the initial horn entrance larger and smaller by way of changing the mouth ratios and see what happens !

You guys are great.  Thanks !

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Disco Stu Quote  Post ReplyReply Direct Link To This Post Posted: 28 May 2005 at 6:32am

Lol it always amazes me how people come up with new ideas from existing things.

If you are gonna build it coax drivers might be too deep for the cabinet so be careful.

I dont really understand why you dont just go for an existing design which works but anyway.

Btw you can run a whole band PA including backline off of 1 13amp socket no sweat. Just take the lights off a different circuit. Some say its playing with fire running guitar, bass, keys and PA off of one socket but sometimes one socket is all thats available.

Stu

All you need to know is:
Sensitivity + Power Handling - Power Compression = Max Output

My acts:
www.myspace.com/thebowiexperience
www.myspace.com/scheisseelektronisches
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tb_mike Quote  Post ReplyReply Direct Link To This Post Posted: 02 June 2005 at 5:12am
Originally posted by Disco Stu Disco Stu wrote:

Lol it always amazes me how people come up with new ideas from existing things.

If you are gonna build it coax drivers might be too deep for the cabinet so be careful.

I dont really understand why you dont just go for an existing design which works but anyway.

Btw you can run a whole band PA including backline off of 1 13amp socket no sweat. Just take the lights off a different circuit. Some say its playing with fire running guitar, bass, keys and PA off of one socket but sometimes one socket is all thats available.

Stu

I think part of the luck is,that the peaky nature of music prevents the fuses/breakers from tripping rather than constant load systems like 2.4kw heaters.

 

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