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

Hemp FR8 MLTL
Hemp FR8 MLTL
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 8th February 2006, 05:23 PM   #11
Dumbass is offline Dumbass  British Antarctic Territory
diyAudio Member
 
Join Date: Mar 2003
Location: British Antarctic Territory
Quote:
Originally posted by VadimB
Why do you think higher Q is not good for the horn? What goes wrong?
I'm no expert on horn theory, but I believe you can think of it this way:

High Qts drivers have relatively low motor (i.e. magnet) strength. That is why they resonate more at their Fs (that is one definition of Q).

Low Qts drivers have relatively high motor strength. That is why they resonate less at their Fs, because the electromagnetic force on the cone predominates.

A horn converts a high energy, low magnitude signal (at the driver) to a low energy, high magnitude signal (in free air). A large magnet, low Qts is therefore much better suited to horn-loading.
  Reply With Quote
Old 1st March 2006, 10:26 AM   #12
Scottmoose is offline Scottmoose  United Kingdom
diyAudio Member
 
Scottmoose's Avatar
 
Join Date: Mar 2005
Location: UK
Aha. A BIB for the hempsters. Sorry I've been away from the board for a while -I've hand my MA thesis to finish, which took priority over audio.

OK, so, a nice hemp-coned mid Q 8" driver. And a matching BIB cabinet for its specs. Well, I'd build something like this: 10" wide, 17" deep, 70" tall (external measurements -I won't go taller than 70" now though). Driver 39" from the base. Terminate internal baffle 7 6/16" from the floor and front and rear internal walls. Assumes 3/4" build material. That's first pass dimensions though. I can probably get something better out of it with a little more time, but I only just found the thread.

Hey, Dan -you know I built an enlarged pair of BIB's for the FF225K a while back for some friends? Well, yesterday evening I was round at their house for a beverage or two to celebrate handing my thesis in, and we decided to try a little experiment. It's funny you shoud mention the B200s... because that's what we screwed into them. OK, they shouldn't work. And in some ways they didn't -Q's too high, so there was a big peak, as you'd expect. But, and I'm not joking, the bass shook ornaments off a granite window-ledge. These things couple to the room like nothing else I know, bar big horn loaded Tannoy DCs. With some DSP applied to kill the peaks (yes, shoot me for crimes against purity) they could really be very good indeed. Good for stadium rock, and you can't say that about many single drivers. That natural rising response might've helped flatten things out too.
__________________
"'That'll do", comes the cry of the perfectionist down the ages.' James May -The Reassembler
www.wodendesign.com Community sites www.frugal-horn.com http://frugal-phile.com/
  Reply With Quote
Old 1st March 2006, 01:41 PM   #13
dmason is offline dmason  United States
diyAudio Member
 
Join Date: May 2004
Location: Republik of Kalifonia
Scott

Somehow I am not surprised to hear this about the B200. There is magic in that thing, and this is the first time I have heard about its use in anything other than either an aperiodic load, www.omegaloudspeakers.com (A8) or of course, the open baffle. The DarkStars. for example, are some of the very best speakers I had ever heard, when I completed them, truth being stranger than fiction. For myself, I find the larger baffles just abit much for condo life, and the rear loaded tractrix B.I.B. is a perfect compromise. A very spacious sound, overall.

I figure DSP is okay as long as any doctoring of the sound is done in The Digital Domain. So, you have broken no laws. I would be interested in knowing what they were powering it with.

I recommend laying your hands on a pair of Hemp drivers. These SuperHemps of Louis' in my living room are in fact 2.5 ft^3 cabinets, nice wide baffle does wonders for the high calorie wave launch. In a BIB, all the better. A KILLER Project!!
__________________
"Pilau Buggah, Big Islan Mo Betta!!"
  Reply With Quote
Old 1st March 2006, 02:13 PM   #14
Scottmoose is offline Scottmoose  United Kingdom
diyAudio Member
 
Scottmoose's Avatar
 
Join Date: Mar 2005
Location: UK
Hi Dan, sorry it's been a while! Amp was a Pass DIY Zen V5 (the PP one). We also tried it with Simon's Audiolab pre/power, which also worked pretty well, once we'd added some series resistance -5ohms did the trick.

The major peak was around 55Hz (I'm going by bass guitar notes here), F3 circa 40Hz. Rolled off pretty quickly below that, 30Hz was just about audable, but only just. Ripple wasn't bad -oddly, it worked better with most of the stuffing ripped out, just a layer on the base and a touch in the point above the driver. We reverted to the FF225K after a couple of hours as it was more refined, but it worked. If you're interested, the external dims were 10" x 19" x 70". Not small then. But not impossibly large either. I'm tempted to run some numbers on the B200 and try to optimise things as far as possible. I suspect just a fractional widening should do the trick.

Cheers
Scott
__________________
"'That'll do", comes the cry of the perfectionist down the ages.' James May -The Reassembler
www.wodendesign.com Community sites www.frugal-horn.com http://frugal-phile.com/
  Reply With Quote
Old 1st March 2006, 02:33 PM   #15
lovechild is offline lovechild  Europe
diyAudio Member
 
Join Date: Oct 2005
Default BIB ?

Sorry, what does BIB stand for???

thanks, LC
  Reply With Quote
Old 1st March 2006, 02:39 PM   #16
dmason is offline dmason  United States
diyAudio Member
 
Join Date: May 2004
Location: Republik of Kalifonia
Bigger Is Better
__________________
"Pilau Buggah, Big Islan Mo Betta!!"
  Reply With Quote
Old 1st March 2006, 02:45 PM   #17
Scottmoose is offline Scottmoose  United Kingdom
diyAudio Member
 
Scottmoose's Avatar
 
Join Date: Mar 2005
Location: UK
BIB = Bigger Is Better. It's a giant TQWT / rear loaded folded tractrix horn based on one of Paul Voigts original ideas from the 1930s. Terry Cain is the man who brought it back into the public eye after spotting it in the Fostex Craft Handbooks I believe. Not to all tastes, but Dan and I are big fans. Well, when I say 'giant' I mean it's pretty slim, anywhere betwen 7 and about 12" wide depending on the driver, moderately deep -circa 12" - 20" depending, as before, on what driver you're using, and about 6ft tall, with a single fold, so a total of 12ft line-length. The cabinet is completely open at the top -that's the horn mouth, and is designed to be stuffed into corners. Loaded that way it couples to the room very nicely indeed. They measure much better than they simulate.

Best
Scott
__________________
"'That'll do", comes the cry of the perfectionist down the ages.' James May -The Reassembler
www.wodendesign.com Community sites www.frugal-horn.com http://frugal-phile.com/
  Reply With Quote
Old 1st March 2006, 03:01 PM   #18
jimmyd53 is offline jimmyd53  United States
diyAudio Member
 
jimmyd53's Avatar
 
Join Date: Jan 2006
Location: EUGENE, OREGON
Default FR8

The USA distributor of the Hemp Acoustic FR8 is e-speakers.com. The FR8 is currently out of stock according to their web site. E-speakers has not responded to my email as to when the FR8's will be available.
James
  Reply With Quote
Old 1st March 2006, 03:17 PM   #19
lovechild is offline lovechild  Europe
diyAudio Member
 
Join Date: Oct 2005
Thanks Scott, that sounds like a very interesting design to me, my room it's about 10.5 feet high - and really I like the name

Is there a place where I can find more information about BIBs, like what driver would suit and how to adjust the enclosure to the drivers etc.


thanks,
LC
  Reply With Quote
Old 1st March 2006, 03:51 PM   #20
Scottmoose is offline Scottmoose  United Kingdom
diyAudio Member
 
Scottmoose's Avatar
 
Join Date: Mar 2005
Location: UK
Well, Terry's originals are here: http://melhuish.org/audio/DIYTQ8.html

Apart from that, there isn't much, unless you can get the Fostex Craft Handbooks. I've tried, believe me! That said, both Dan Mason and I have spent a long time fooling around with these enclosures, and we can probably give you some tips / suggestions. If Greg is around (GM), I'm sure he'll be willing to help out too as he's forgotten more about horns and speakers in general than I'll ever know. I don't want to hijack the thread, so I'll keep this brief.

The line-length is basically set to 1/2 the wavelength of the tuning frequency. Drivers with an Fs of 50Hz or more are usually best tuned to their natural resonance freqency in these enclosures, or very fractionally less depending on various factors, not least of them being the driver excursion. 5Hz is about the practical limit, though there are exceptions, as you'd expect.
They're quite forgiving as enclosures go, about what drivers you use. Mid Q drivers of circa 0.3-0.4 are often the best bet, but low Q drivers can work very well too, if you know what you're doing: a low damping factor amplifier and high series resistance cables, or a small resistor in series with the driver are the key to getting them to work in that situation. High Q drivers are best not approached or you'll get a big hump in the bass. I was very surprised that the B200 worked as well as it did; call it the exception that proves the rule. It didn't have very low bass though -a direct consequence. 40Hz was about it in practical terms, but above that it thundered. The mouth area needs to be bwtween 3 to 4.5 times the surface area of the driver, and they really do need to go in corners as the rear boundary condition increases the mouth area and decreases reflections back down the line. The various Hemp drivers under discussion look like being an ideal match.

Best
Scott
__________________
"'That'll do", comes the cry of the perfectionist down the ages.' James May -The Reassembler
www.wodendesign.com Community sites www.frugal-horn.com http://frugal-phile.com/
  Reply With Quote

Reply


Hemp FR8 MLTLHide 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
Hemp FR8 vs Hemp FR8C - Which One? Estes Full Range 16 4th May 2009 07:42 AM
What to do with Hemp CO8Vs? spacies Full Range 48 19th September 2008 06:32 AM
Martins MLTL with Hemp drivers johnb Full Range 10 30th March 2007 04:55 AM
HEMP FR810hq one1speed Full Range 10 4th April 2006 07:11 PM
Hemp update pjanda1 Full Range 4 10th November 2005 08:21 AM


New To Site? Need Help?

All times are GMT. The time now is 08:25 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.79%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki