Too flat? - 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 21st September 2003, 03:13 AM   #1
diyAudio Member
 
Join Date: Jul 2003
Location: Silicon Valley
Default Too flat?

Is there such a thing as too flat?

I've been playing with Martin King's Mathcad transmission line programs, and I've come up with a box for a certain (rather pricy) 5 1/4 inch mid/bass. The design shows a response curve that's razor flat down to about 40Hz and not off too much at 30Hz. I wonder if it would sound boomy in a typical small to medium size room, due to room gain.

But then again, I may be fooling myself. The amount of stuffing material called for is well over 1 lb per cubic foot in the middle part of the line. The worksheet has a comment in it suggesting the density should be in the range 0 to 1. Martin, if you are listening, do the calculations break down at relatively high stuffing densities?
__________________
Davy Jones
  Reply With Quote
Old 21st September 2003, 03:17 PM   #2
MJK is offline MJK  United States
Account disabled at member's request
 
Join Date: Feb 2002
Location: Clifton Park, NY
Quote:
Martin, if you are listening, do the calculations break down at relatively high stuffing densities?
Yes! The curve fit I use for stuffing is smooth up to 1 lb/ft^3 and then oscillates all over the place. I my opinion, using stuffing densities well above 0.75 lb/ft^3 indicates that stuffing is being used to correct a bad geometry design. I believe a good TL design should use stuffing densities between 0.25 and 0.5 lb/ft^3.
  Reply With Quote
Old 23rd September 2003, 08:05 PM   #3
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Default Boomy gain

You probably listen to room gain. Anechoically flat curves sound boomy inroom.
  Reply With Quote
Old 24th September 2003, 06:06 AM   #4
advance is offline advance  Switzerland
diyAudio Member
 
Join Date: Aug 2003
Location: Schwyz
Quote:
You probably listen to room gain. Anechoically flat curves sound boomy inroom.
I agree fully.

Click the image to open in full size.

Brown dashed line = Combined response of room gain and baffle diffraction loss for a baffle between 25 to 30 cm
Blue dashed line = Example of an adapted 2 Pi loudspeaker frequency response
Red line = Resulting in room sound response

While this adjusts the substantial room-gain and baffle diffraction loss, the room modes and resonances have not been eliminated! Nevertheless, you will be surprised to which degree the so-far boomy bass has been eliminated too. The ear seems to be tolerant to room modes as long as the overall balance is guaranted.

http://www.arsenal.net/speakers/allison/royart.zip (look out - file size approx. 3meg)

advance
  Reply With Quote
Old 27th September 2003, 12:30 PM   #5
diyAudio Member
 
mikee12345's Avatar
 
Join Date: Nov 2002
Location: NZ
i have a jBL 2226 in 33hz 175L heres its response=

it sounds very nice!.
in my 2.2mx4m room with low ceiling,the walls vibrate noticably with 20watts.

im interested in measuring my SPLs at various positions

should i just use sinewaves,note each SPL at measured positions and then compare?


the subs in a corner position

when i get SPL meter i will do this and post results perhaps.

cheers
Attached Images
File Type: jpg jblresp.jpg (41.0 KB, 288 views)
  Reply With Quote
Old 3rd October 2003, 06:06 PM   #6
advance is offline advance  Switzerland
diyAudio Member
 
Join Date: Aug 2003
Location: Schwyz
Default Room Frequency Response Measurements

Quote:
should i just use sinewaves,note each SPL at measured positions...
In my opinion, room frequency response measurements are generally speaking somewhat delicate. Pink noise and RTA measurements are often unreliable. Our ears tend to ignore late reflections in the treble region while adding some weight in the mid-range and even more weight in the bass region. So, theoretically an adaptiv room frequency response measurement should be used, which excludes most room reflections at high frequencies (except approx. the first 10 ms), includes more reflections in the midrange and includes nearly all room reflections in the bass region (up to approx. 200 ms at a frequency resolution of 1/3 octave).

So, your proposed measurement setup may be all right as long as it is limited to the bass region (up to approx. 150Hz) and you smooth out room modes manually.

advance
  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
Coral Flat 5 t/s ballsingtripp Full Range 17 15th November 2009 08:46 AM
flat sub for flat TV Artmaster Subwoofers 0 17th December 2008 11:15 AM
How Flat is "Flat"? (XT18WO + 27TBFC-G = MTM) zenon Multi-Way 3 21st January 2007 03:15 PM
Coral Flat 10 albertli Full Range 16 3rd August 2006 03:07 PM
How flat is a gainclone Adam M. Chip Amps 3 29th May 2004 03:16 PM


New To Site? Need Help?

All times are GMT. The time now is 06:04 AM.


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