Backloaded horns, do we want delayed bass, and how do we want it? - Page 3 - diyAudio
Go Back   Home > Forums > Loudspeakers > Multi-Way

Multi-Way Conventional loudspeakers with crossovers

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 24th January 2014, 07:46 PM   #21
diyAudio Member
 
Phenoholic Anonymus's Avatar
 
Join Date: Dec 2013
Short recap of the Visaton thread. A low Qes driver does not lead to much more efficiency compared with a high Qes driver. -Sofar so good - the low Qes does have a slightly less peaky output / more control. Interesting point made on the forum there: not Fs x 2 / Qes is responsible for the high cut off but the hornthroath dimension. Not so much the volume of the backchamber but it's throathdimensions. Good to see the Germans take this stuff so serious , complete with measurements in Visaton's own 7x7x7 meter anechoic messraum. And a seven plus page long discusion without any trolls.

This remark made me grinn, in essence a backloaded horn is a bassreflex enclosure with very, very good port to air adaptation.

Last edited by Phenoholic Anonymus; 24th January 2014 at 07:51 PM.
  Reply With Quote
Old 26th January 2014, 08:47 PM   #22
diyAudio Member
 
Join Date: Jan 2008
Quote:
Originally Posted by Phenoholic Anonymus View Post
From a recent link in a HM art thread i found these numbers for the summation effect. Two sources need to be under 1.5 ms from each other to sum correctly. There is little information (links welcome!) about this effect in regards to Spl and frequency.
Two equidistant sources can be virtually any distance away from the listener and sum properly.

1.5 ms describes a distance sound will travel in time, and proper summation requires the arrival times to be within a quarter wavelength or so.
You can figure the wavelength by dividing 1130 feet or 347.7 meters (the speed sound travels per second at average room temperature) by the frequency.

A 1.5ms time offset is not problematic at around 180 Hz and below, but can be very problematic in the mid frequencies.

If the horn path of the BLH is around a wavelength behind the front output it can reinforce, sum, be in phase with the front output, even though it lags behind in time.

The problem with the BLH is if the upper frequency portion of the "horn" is not reduced enough in level by the folds or damping, the arrival time difference creates a ragged mid/high frequency response, "comb filtering".

Last edited by weltersys; 26th January 2014 at 08:56 PM.
  Reply With Quote
Old 26th January 2014, 08:58 PM   #23
diyAudio Member
 
Phenoholic Anonymus's Avatar
 
Join Date: Dec 2013
Thanks! Very clear, the more mid out of the "port" or horn the more problems.
  Reply With Quote
Old 26th January 2014, 09:01 PM   #24
diyAudio Member
 
Join Date: Jan 2008
Yup, no free lunch, as damping the port upper response also reduces LF output, leaving one on the "horn" of a dilemma.
  Reply With Quote
Old 26th January 2014, 09:19 PM   #25
diyAudio Member
 
Phenoholic Anonymus's Avatar
 
Join Date: Dec 2013
I think in this respect, the bend is my friend, to damp some of the mid out of the horn.
  Reply With Quote
Old 26th January 2014, 09:41 PM   #26
diyAudio Member
 
Join Date: Jan 2008
Quote:
Originally Posted by Phenoholic Anonymus View Post
I think in this respect, the bend is my friend, to damp some of the mid out of the horn.
The back chamber volume can be used as an acoustical low pass filter, but don't count on much mid reduction from bends, just ragged response .

Check out the response of this four fold horn, I tried it with the speaker open also (like a BLH) response was little different.
LHC was a 4" speaker, LHD used an EVDH1A compression driver, LHGM used a sealed back 4".

LHC was the same speaker as LHD, with a couple 1/2" holes cut in the sealed back.
Attached Images
File Type: jpg Four fold Long Horn.jpg (236.6 KB, 144 views)
  Reply With Quote
Old 26th January 2014, 09:52 PM   #27
diyAudio Member
 
Phenoholic Anonymus's Avatar
 
Join Date: Dec 2013
Thanks, very insightfull Graph, same effect as with the Jericho horn 1 page ago, the response seems to fall due to the mass roll off > valley > peaks, peaks, far into the midband. "Mass roll off" get's stranger by the minute. In a straight horn i understand midrange coming out of the horn "i can see", but in a folded horn with a backchamber (Jericho not the graphs above), where mass roll off should prevent or at least damp signal above 500 Hz, weird.

Last edited by Phenoholic Anonymus; 26th January 2014 at 10:06 PM.
  Reply With Quote
Old 26th January 2014, 10:28 PM   #28
diyAudio Member
 
Phenoholic Anonymus's Avatar
 
Join Date: Dec 2013
Theoretically these speakers should be unlistenable. Long horn (large amount of delay), smooth (no loss of midrange), no backchamber and almost no bends. This would be the posterchild for midrange content out of a backloaded horn ->

Click the image to open in full size.

Last edited by Phenoholic Anonymus; 26th January 2014 at 10:38 PM.
  Reply With Quote
Old 27th January 2014, 08:05 PM   #29
diyAudio Member
 
Phenoholic Anonymus's Avatar
 
Join Date: Dec 2013
And another example of a backloaded horn with lots of mid output out of the horn. I have come to the conclusion there is no way to stop the midrange coming out of the horn. Mass roll off, small volume behind the driver, damping, nothing will prevent mid coming out of the horn...

Click the image to open in full size.

Nelson Pass on the Kleinhorn stuffing (pic above):

I ended up taking out all the stuffing except in the chamber before the throat. The sonic result was considerably improved over that of Part 1. The sound was more dynamic and lively, and I found that my approach of removing delayed higher frequencies from the horn did not improve the tonal
balance, coherence, or even the imaging”

Click the image to open in full size.
http://www.firstwatt.com/pdf/art_kleinhorn1.pdf
http://www.firstwatt.com/pdf/art_kleinhorn2.pdf

I will stop worrying and learn how to love the backwave

Last edited by Phenoholic Anonymus; 27th January 2014 at 08:08 PM.
  Reply With Quote
Old 27th January 2014, 09:12 PM   #30
GM is offline GM  United States
diyAudio Member
 
GM's Avatar
 
Join Date: Jun 2003
Location: Chamblee, Ga.
Study up on human hearing perception and you'll find that below ~250-500 Hz [and much higher for a relative few] depending on the person and room conditions that our hearing acuity rapidly falls off, otherwise we wouldn't be able to tolerate the BW below this point in a typical room.

The 'name of the game' then is to use a low acoustic XO point same as the pioneers did, first by using low Qt motors coupled to a very high output impedance to maximize efficiency due to having little power available, then raising the driver's Qt as the amp's output impedance fell and its power increased over time until horn drivers wound up with anywhere from a ~0.5-1.0 Qts depending on the app with high power amps with tiny fractions of an ohm output impedance.

GM
__________________
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
  Reply With Quote

Reply


Hide 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
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Smaller Fostex Backloaded Horns Persona Full Range 29 27th November 2012 11:03 AM
Best Firstwatt amp for backloaded horns? blue lander Pass Labs 55 24th May 2012 01:25 AM
WTB: Fostex backloaded horns, complete or just cabs jim_vt Swap Meet 0 13th July 2005 01:49 PM
Fostex Backloaded horns dreaded 42 Multi-Way 5 25th March 2004 03:27 PM
Bass Horns? Chris_SWE Multi-Way 7 7th January 2002 03:58 AM


New To Site? Need Help?

All times are GMT. The time now is 10:16 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2