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

Why is floor bounce considered only a bass issue?
Why is floor bounce considered only a bass issue?
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 5th August 2019, 08:36 PM   #11
Defo is offline Defo  Norway
diyAudio Member
 
Join Date: Nov 2008
Quote:
Originally Posted by Juhazi View Post
Gradient 1.4 by late Jorma Salmi. Downfire bass and a coaxial.
Finnish Gradient 1.4 loudspeaker
Gradient 1.4 loudspeaker, Jorma Salmi | Inner Magazines

Click the image to open in full size.
Interesting construction. But I can't see how it can mitigate floor bounce seeing the woofer would need to be crossed at 350-400 Hz to cover the floor bounce from the midrange unit.

Last edited by Defo; 5th August 2019 at 08:49 PM.
  Reply With Quote
Old 5th August 2019, 08:53 PM   #12
CharlieLaub is offline CharlieLaub  United States
diyAudio Member
 
Join Date: Mar 2007
Location: Michigan
Quote:
Originally Posted by Defo View Post
Why is floor bounce considered only a bass issue?

Shouldn't this kind of cancellation affect all frequencies with adequate vertical dispersion?

And also, why is the floor bounce frequency always referenced as singular and not plural? I would imagine more than one narrow band of frequencies being potentially affected.
"Floor bounce" is the term used to refer to the interaction of the direct sound and the first reflection off of the floor. I think this became a "popular thing" when people started measuring loudspeakers and found this huge dip in the lower midbass and then thought "Holy cow, this is a seriously BAD response!". But, as many people have pointed out, the sound undergoes many reflections and many returns from the room reach the listener. This tends to even out the floor bounce when you consider the hearing process and what is perceived by the brain. A microphone measurement is not the same thing as the ear-brain hearing process and this is a great example of when the "mic" is not a good indicator of what you hear. So don't worry about it too much. IMHO room modes are more of a problem.

You are correct in that this phenomenon can effect all drivers. But it depends on how far above the floor they are, and what their passband is. Take a madrange - if this is located high above the floor and the midrange is also crossed high, the dip frequency is below the lower edge of the passband and the midrange response would be completely unaffected. Another way to think about is that it is affected, but below the driver's rolloff, and therefore doesn't impact the passband.

Roy Allison (I think it was him) once outlined a design principle in which you put the woofer at the floor, and the midrange as high as possible, e.g. 40" above the floor or more, and cross over between W and M at 350Hz or above. Just as the floor bounce would be below the midrange's passband, the woofer's floor bounce will be too high in frequency and out of it's passband as well. The frequency of the bounce is inversely proportional to the distance above the floor, and also the woofer's diameter spans from the floor up to 10" or 12" above the floor and this vertical "length" helps to smear out the floor bounce making any dip shallow to non-existent. This is also the case I believe when multiple woofers are stacked vertically and adjacent to one another. The only downside to the Allison design is that the W and M are acoustically far apart at the crossover point, so instead of floor bounce you now have lobing in the crossover region to worry about.
__________________
Visit my Audio Web Page <<--CLICK TO LEARN MORE-->> Get my LADSPA plugins
  Reply With Quote
Old 6th August 2019, 05:15 PM   #13
graaf is offline graaf  Poland
diyAudio Member
 
graaf's Avatar
 
Join Date: Jun 2007
Quote:
Originally Posted by Defo View Post
Why is floor bounce considered only a bass issue?
well...

Mr Lyngdorf's opinion on the issue of the floor reflection
__________________
"high phooey and hystereo" - Yascha Heifetz

Last edited by graaf; 6th August 2019 at 05:17 PM.
  Reply With Quote
Old 6th August 2019, 05:41 PM   #14
Juhazi is offline Juhazi  Finland
diyAudio Member
 
Juhazi's Avatar
 
Join Date: Mar 2007
Location: Jyväskylä, Finland
Quote:
Originally Posted by Defo View Post
Interesting construction. But I can't see how it can mitigate floor bounce seeing the woofer would need to be crossed at 350-400 Hz to cover the floor bounce from the midrange unit.
Remember the effect of listening distance too!

I did just that in my clone, LR2 xo at 300Hz. Room measurements with long gating always show mutiple reflections and modes...

SEAS MR18 3-way

Click the image to open in full size.
__________________
Radikal aktivist AINOgradient speaker project

Last edited by Juhazi; 6th August 2019 at 05:45 PM.
  Reply With Quote
Old 6th August 2019, 06:16 PM   #15
system7 is online now system7  United Kingdom
diyAudio Member
 
system7's Avatar
 
Join Date: Aug 2008
Location: Portsmouth UK
Only rarely does a topic here interest me these days, but floor bounce is a goodie.

Amidst all the trade-offs of speaker performance, getting the big concert-hall sound in a smallish room is highly interesting, IMO.

A historical note about floor bounce comes from Roy Allison who gave it some thought. TBH, not knowing about Roy Allison and Edgar Villchur in speakers is like not knowing about Beethoven in music.

A Glorious Time: AR's Edgar Villchur and Roy Allison Allison Part 1 | Stereophile.com

The accepted wisdom is you put the woofer near the floor and cross it around 300Hz. You then mount the mid and tweeter section much higher up, where it is clear of the floor bounce or "Allison Effect".

Now your midrange is purer and clearer. An additional trick is to use an MTTM dispersion for the projecting PA-type sound, which has less vertical dispersion, so more immune to refection off the floor and ceiling.

A lovely wall-mounted Allison IC20 speaker on theoretical grounds:

Click the image to open in full size.

Click the image to open in full size.

Much to like there.
__________________
Best Regards from Steve in Portsmouth, UK.
  Reply With Quote
Old 6th August 2019, 10:13 PM   #16
Defo is offline Defo  Norway
diyAudio Member
 
Join Date: Nov 2008
Quote:
Originally Posted by Juhazi View Post
Remember the effect of listening distance too!

I did just that in my clone, LR2 xo at 300Hz. Room measurements with long gating always show multiple reflections and modes...
Quote:
Originally Posted by system7 View Post
The accepted wisdom is you put the woofer near the floor and cross it around 300Hz. You then mount the mid and tweeter section much higher up, where it is clear of the floor bounce or "Allison Effect"
With a 1 meter listening height and midrange placed at that same height, floor bounce cancellation happens at between 250 Hz and 350 Hz with a typical listening distance of 2,5 to 3,5 meters.

This means the woofer should be crossed a bit above this point, probably around 500 Hz to cover it. Which is why I'm puzzled by Gradient's low crossover at 200 Hz.

Crossing over at ~500 Hz would also be right in the area where you would get baffle step loss with a typical sized baffle, so you could fix that as well.

Any input?

Quote:
Originally Posted by system7 View Post
An additional trick is to use an MTTM dispersion for the projecting PA-type sound, which has less vertical dispersion, so more immune to refection off the floor and ceiling.
Why MTTM and not MTM?
Won't the extra tweeter do more trouble than good? (lobing)
  Reply With Quote
Old 6th August 2019, 10:43 PM   #17
CharlieLaub is offline CharlieLaub  United States
diyAudio Member
 
Join Date: Mar 2007
Location: Michigan
Folks, floor bounce just is not that much of a problem unless your listening space is a huge, huge space and speaker are far, far away from walls and ceiling.

In a domestic listening space, the additional multiple reflections off the walls and ceiling "fills in" the dip that you get when you only consider the floor reflection.

Calling "floor bounce" a problem is mostly an academic argument that only applies to certain listening spaces that are not typical of a domestic listening environment.
__________________
Visit my Audio Web Page <<--CLICK TO LEARN MORE-->> Get my LADSPA plugins
  Reply With Quote
Old 6th August 2019, 10:53 PM   #18
CharlieLaub is offline CharlieLaub  United States
diyAudio Member
 
Join Date: Mar 2007
Location: Michigan
Quote:
Originally Posted by system7 View Post
A lovely wall-mounted Allison IC20 speaker on theoretical grounds:

Click the image to open in full size.
That speaker has many good design features, like using two woofer with one reversed. But the two-tweeter thing is really not good!

Also, I believe the general consensus is that speakers on/in walls have poor soundstaging and this stems from the lack of the same reflections from room boundaries that give rise to the various dreaded "bounces" and cancellations...

So, on balance, the design has got it's warts, too.
__________________
Visit my Audio Web Page <<--CLICK TO LEARN MORE-->> Get my LADSPA plugins
  Reply With Quote
Old 7th August 2019, 12:39 AM   #19
AllenB is offline AllenB  Australia
diyAudio Member
 
Join Date: Oct 2008
Quote:
Originally Posted by system7 View Post
use an MTTM dispersion for the projecting PA-type sound, which has less vertical dispersion,
This doesn't have less vertical dispersion.. not in the sense of narrowing it over the pass band. Instead it crosses from narrow to wide at a different discreet frequency, so it needs to be set according to a specific distance.
  Reply With Quote
Old 7th August 2019, 12:40 AM   #20
AllenB is offline AllenB  Australia
diyAudio Member
 
Join Date: Oct 2008
Quote:
Originally Posted by CharlieLaub View Post
Also, I believe the general consensus is that speakers on/in walls have poor soundstaging and this stems from the lack of the same reflections from room boundaries
Soundstage is definitely not dependent on these reflections, in fact it is its best without them.
  Reply With Quote

Reply


Why is floor bounce considered only a bass issue?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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Woofer placement and floor bounce sfdoddsy Multi-Way 1 9th October 2015 02:49 PM
Audibility of floor bounce? mlee Multi-Way 15 4th September 2014 03:48 PM
How to calculate floor bounce reflection(cancellation) jtsaudio Multi-Way 16 7th August 2014 08:47 PM
Floor coupling issue (I supose...) andruca Multi-Way 0 11th January 2007 06:58 AM
HOw close does driver need to be to floor to avoid floor bounce? Kanga Multi-Way 8 24th April 2003 06:09 AM


New To Site? Need Help?

All times are GMT. The time now is 06:20 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Copyright ©1999-2019 diyAudio
Wiki