Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Multi-Way Conventional loudspeakers with crossovers

Artichoke Horn
Artichoke Horn
Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 13th December 2016, 08:10 AM   #21
hollowboy is offline hollowboy  Australia
diyAudio Member
 
Join Date: Jul 2007
Location: 'straya
Quote:
Originally Posted by AllenB View Post
The container on its own weighs a couple of tonnes, filled with concrete it's around 80t. They are rated for 30t.
I like the way you think - but I don't intend to fill the whole thing with concrete. Building horn framework that can take multiple tons of pressure and doing a pour to fill the entire container = too much cash and effort. Also I don't fancy the stress of needing everything to be right on the pour day.

I was considering plastering a thin layer of cement onto a light frame for most of the horn, and only getting hefty at the throat.

I must be relatively lazy & cost conscious about this, or it will never happen. That is:

For $X I can get a 20' container for storage and general use
OR
For $X+Y I can get a 40' container, split between general use and a silly HiFi.

To 'sell' the idea to myself, I'm trying to keep Y (cash and effort) reasonable. The cash component might be <$1000 since I already have most of the gear I'll need.
__________________
This edit signature thingy is seriously hard to find
  Reply With Quote
Old 13th December 2016, 09:20 AM   #22
AllenB is offline AllenB  Australia
diyAudio Member
 
Join Date: Oct 2008
Quote:
Originally Posted by hollowboy View Post
I don't intend to fill the whole thing with concrete.
Well, yeah . I guess it strikes me that 33 cubic metres is quite a space, and convenient that 20 feet is nicely a third of a wavelength at 20Hz. I can't see the point in the 40' option unless you'll build an office in there too
  Reply With Quote
Old 13th December 2016, 11:22 AM   #23
hollowboy is offline hollowboy  Australia
diyAudio Member
 
Join Date: Jul 2007
Location: 'straya
Quote:
Originally Posted by AllenB View Post
Well, yeah . I guess it strikes me that 33 cubic metres is quite a space, and convenient that 20 feet is nicely a third of a wavelength at 20Hz.
With the constrained mouth area, I think 30Hz is about the limit - there would be a bit of ripple if I aimed for 20' & 20Hz.

Quote:
Originally Posted by AllenB View Post
I can't see the point in the 40' option unless you'll build an office in there too
In general, the 40' containers only cost a little more, so I figure why not?

One place has

$1500 - 20'
$1850 - 40' high cube (nearly triple the volume)

In practice, my decision might come down to what's available locally, since transport adds a big chunk to the price.
__________________
This edit signature thingy is seriously hard to find
  Reply With Quote
Old 10th January 2017, 02:41 AM   #24
hollowboy is offline hollowboy  Australia
diyAudio Member
 
Join Date: Jul 2007
Location: 'straya
Quote:
Originally Posted by hollowboy View Post
To 'sell' the idea to myself, I'm trying to keep Y (cash and effort) reasonable. The cash component might be <$1000 since I already have most of the gear I'll need.
Ugh, the red tape. Stultifying and costly. A shipping container becomes a "shed" when permanently sited, so requires permits. The following is one of the 15 requirements for a building permit (which costs $500).
Provide three (3) copies of plans and elevations to a scale not less than 1:100, specifications and methods to be used in the construction.
...but that is not enough. Yesterday I got this: "We have assessed your Building Permit application and have found that we require a Planning Permit.
Please complete attached forms and return."

This 2nd permit ALSO has a fee. They didn't say how much this one is. I find this obnoxious.

...so now I'm thinking of ways to circumvent the bureaucracy:

1) My first thought was to put the shipping container on wheels, so it magically transforms from "farm shed" to "vehicle".

The problem: 5,000kg castor wheels are very expensive, at $2,500-$3,000 for a set. I'd rather spend the money on wheels than on permits (and support a manufacturer rather than a bureaucracy), but $3,000 is a lot to pay for something I only want symbolically.

2) Forget the shipping container, and do a stealth build.

I could make a quick start by turning a couple of IBCs into PPSL* boxes, since they'd be full ninja and easy to weather proof ...and then I'd work on a bigger version.

I can site it in a well screened spot, almost 300m from any road, so anything vaguely low profile should be OK.

*Intermediate Bulk Containers --> Push Pull Slot Loaded
Attached Images
File Type: jpg ibc.jpg (40.1 KB, 362 views)
File Type: png PPSL.png (29.5 KB, 348 views)
__________________
This edit signature thingy is seriously hard to find
  Reply With Quote
Old 2nd February 2017, 03:03 AM   #25
hollowboy is offline hollowboy  Australia
diyAudio Member
 
Join Date: Jul 2007
Location: 'straya
Another layer of red tape was added - the cost of the permits required blew out to >$1500. Sod that*

However: there's plenty of stuff in my zone does not require a permit. Earthworks and retaining walls up to 1m are OK ...so I think I'll be doing some earthworks in my spare time, that just happen to form the shape of a bass horn. Keeping this bit <1m won't be too bad.

I'm now planning a 'normal' horn system for midbass and above (meaning: fairly big, but not a permanent / fixed structure). The bass can come later... probably much later.

Pictured are my midbass and bass horns, under construction. The bass section obviously has a way to go yet.

The midbass horn is 150cm long. I'm hoping to cover 75Hz-400Hz with this, and >400Hz with compression drivers.

*old Australian joke:
A swagman (roving labourer) is walking down a scorchingly hot road through a vast open plain. The monotony is relieved only by the occasional dead tree and a gate every few kilometres. A grazier pulls up beside him in a large, comfortable car. He offers the swagman a ride.

"You can open your own b|o0dy gates!" says the swaggie, and he keeps on trudging through the dust.
Attached Images
File Type: jpg Construction.jpg (503.5 KB, 332 views)
__________________
This edit signature thingy is seriously hard to find
  Reply With Quote
Old 24th February 2017, 04:22 AM   #26
hollowboy is offline hollowboy  Australia
diyAudio Member
 
Join Date: Jul 2007
Location: 'straya
Quote:
Originally Posted by weltersys View Post
If the horn is to be used up to 800 Hz or so, the throat should be narrowed to around 6 inches wide for better dispersion and phase response, or better yet, use a phase plug as shown in the photos below. When building/testing the Kangaroo Horn in the parking lot of a big-box lumber store with a parking lot adjacent to the St.Paul motel I lived at, I asked an interested shopper to participate in an A/B test with or without the phase plug, the better clarity the phase plug provided was obvious to him. This type of phase plug is similar to the ones Dave Gunness designed for the 10" mids in the EV MT systems from the mid 1980s.
Building midbass horns. I've made up my mind on most things, but still have one question:

My rough prototype gives enough bandwidth.

If I don't need to improve bandwidth, is there any point in using a phase plug? That is: would a square(ish) throat + a phase plug be clearer / have better sound quality, or should I just do another slot throat?

+++

The drivers = Faital 12FH520
Prototype horn was 150cm long, 70x120mouth (it had to fit through a door)
Final horn shall be 230cm long, 120x120mouth (to be built on site)

For the final horn, I decided to make the biggest horn I could, with the least work. The outside will be a simple butt joined ply coffin, using uncut (full sheets) ply.

In the picture, the pink lines are the outer box:
FOUR full sheets of 15mm ply.

The blue lines will be the horn curve:
FOUR full sheets of 7mm ply.

...so the horn shape will use a total of 8 ply sheets, but I'll only have to cut two of them - a triumph for laziness.

Pictures:

rough prototype under construction
'sketch' for final horn
what I'm planning to use >500Hz (JBL 2445 in a modified no-name horn off ebay)
Attached Images
File Type: jpg IMAG0246[1].jpg (751.1 KB, 299 views)
File Type: jpg lazy horn.jpg (19.5 KB, 272 views)
File Type: jpg 2445 DIY.jpg (629.0 KB, 137 views)
__________________
This edit signature thingy is seriously hard to find
  Reply With Quote
Old 24th February 2017, 06:20 PM   #27
POOH is offline POOH  United States
diyAudio Member
 
POOH's Avatar
 
Join Date: Oct 2010
Location: Ohio
Do you have a copy your horn you can post modeled in Horn Response with that driver?
__________________
I'm into real life dynamics and tone. Recipes for fully horn loaded horns systems are for me, direct radiator speakers bore me. Why have a fax when you can have vivid 3d technicolor? I love the sound of live instruments. This is my goal with my playback.
  Reply With Quote
Old 24th February 2017, 11:17 PM   #28
hollowboy is offline hollowboy  Australia
diyAudio Member
 
Join Date: Jul 2007
Location: 'straya
Quote:
Originally Posted by POOH View Post
Do you have a copy your horn you can post modeled in Horn Response with that driver?
The big picture shows the values for an open-backed build: 9999 litre rear chamber and 200cm throat.
The SPL plot shows how it should compare to the smaller prototype: exactly the same, with but with 20Hz more extension.

Small picture = how I'll actually build it: 50 litre rear chamber and 150cm throat. Again this is compared to the prototype: exactly the same, with but with 20Hz more extension.

Note that it doesn't seem very sensitive to variation. This seems to become true for any horn that's full-sized, e.g. if I make other changes like doubling the front chamber or model a different expansion type, the plot stays about the same.
Attached Images
File Type: jpg Faital 200 throat 9999 chamber.jpg (97.8 KB, 110 views)
File Type: jpg Faital 150 throat 50 chamber.jpg (35.5 KB, 45 views)
__________________
This edit signature thingy is seriously hard to find
  Reply With Quote
Old 24th February 2017, 11:43 PM   #29
hollowboy is offline hollowboy  Australia
diyAudio Member
 
Join Date: Jul 2007
Location: 'straya
The black line is an in-room measure of the prototype. No eq.
Boundary effects (mostly) make this much rougher than the model, but it is indeed strong 80-500Hz as predicted.
The grey line is with a JBL 2445 (single cap crossover) to show relative levels... the JBL should be 111dB, so the Faital appears to be ~as loud as predicted.

I applied subtractive eq based on this grey line, to get flat output 60Hz - 6kHz. It was good.

In the short term, that's what I want to get outdoors. Once I have the midrange sorted out, I will add more parts to make it a 4-way.
Attached Images
File Type: jpg Prototype for outdoors.jpg (86.8 KB, 53 views)
__________________
This edit signature thingy is seriously hard to find
  Reply With Quote
Old 25th February 2017, 12:16 AM   #30
hollowboy is offline hollowboy  Australia
diyAudio Member
 
Join Date: Jul 2007
Location: 'straya
Quote:
Originally Posted by hollowboy View Post
Note that it doesn't seem very sensitive to variation. This seems to become true for any horn that's full-sized, e.g. if I make other changes like doubling the front chamber or model a different expansion type, the plot stays about the same.
Oops - I realised I had copied a couple of values from the wrong place / some other driver (e.g. moving mass was too low). But after pasting in the right numbers, I still get the same plot. Not very sensitive to variation

usspeaker.com link for values

A Dayton woofer tester (using 1.25kg added mass and 11" effective diameter to calculate VAS) gives some values as very close to the spec:

VAS (spec) 64.2 litres - measured 62.8 litres
mms (spec) 56g - measured 53g
SPL (spec) 98dB - measured 97.5dB

Other values measure too high, but may drop with use, e.g.

Fs (spec) 50Hz - measured 63Hz
__________________
This edit signature thingy is seriously hard to find
  Reply With Quote

Reply


Artichoke HornHide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Horn experts - Please help to determine optimal throat size for low-mid horn pk Multi-Way 9 19th August 2012 06:29 PM
Folded horn - volume between subwoofer cone ane th start of the horn benpalmer Subwoofers 8 9th April 2012 01:10 PM
Ron's Austin II, old T-Horn, Lab12 Tapped horn, CNC Photo Background layertone Full Range 2 23rd December 2009 12:51 AM
looking for 6.5inch woofers suitable for a 30 - 35Hz horn... and a small horn too :P SkinnyBoy Multi-Way 24 13th February 2004 05:06 AM


New To Site? Need Help?

All times are GMT. The time now is 07:26 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki