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Re: Standing wave notch [message #19243 is a reply to message #19242] Mon, 14 May 2007 13:31 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18783
Registered: January 2001
Illuminati (33rd Degree)

Dipoles have a directional pattern that favors front and back, to be sure. But it is frequency sensitive and not 50/50 straight front to back. There is radiation at angles other than straight on-axis. I suspect that your notch is probably from a wall reflection. To find out, you can move the speakers and see if the notch frequency moves. Take 'em outside and see if the notch goes away. If it doesn't, then it's something in the speaker. If it does, then it's something in the room.


Re: Standing wave notch [message #19244 is a reply to message #19243] Mon, 14 May 2007 14:56 Go to previous messageGo to next message
DMoore is currently offline  DMoore
Messages: 58
Registered: May 2009
Location: Seattle
Baron
I think that LF drivers have a power-frequency bandwidth, that is, they are most efficient in certain topologies and that each combination of driver and loading topology is further bandwidth-limited or at least frequency-specific. Throw a crossover into the mix, and stir vigorously. Place in a room of unknown acoustic parameters...

I too have been on the search for the so-far-still-elusive low-frequency response combined with the appropriate ability to "punch".
Seems that if a particular driver is good at one end of the spectrum, it gives up the other. Getting a balance is a combination of the loading, the specifics of the driver and the crossover. The crossover is an important consideration in the mix, too.

Room suck-out could be a culprit, but if you had punch in the first place, it is unlikely that it would be removed completely. My opinion is that it is the particular driver/loading/crossover combination.

No clean answers to this one.

DM

slam is a subjective term [message #19245 is a reply to message #19221] Mon, 14 May 2007 19:38 Go to previous messageGo to next message
Me is currently offline  Me
Messages: 2
Registered: May 2009
Esquire
When someone says slam it could mean a lot of things.Stick with the terms that are standard.There are standards to the industy not every one knows them.sSo to say slam is not bass WELL LET'S ALL MAKE IT UP

Re: slam is a subjective term [message #19246 is a reply to message #19245] Mon, 14 May 2007 20:15 Go to previous messageGo to next message
SteveBrown is currently offline  SteveBrown
Messages: 330
Registered: May 2009
Grand Master
Some physical sensation of impact is what I mean by "slam", sorry my term was not precise. I meant the same thing when I used the term "punch". Is there a standard term for this? If so, can you enlighten me?

Re: Back from Dallas and depressed ... [message #19251 is a reply to message #19221] Fri, 18 May 2007 14:00 Go to previous messageGo to next message
hurdy_gurdyman is currently offline  hurdy_gurdyman
Messages: 416
Registered: May 2009
Illuminati (1st Degree)
Steve,

I assume you've already tried this, but, just in case, have you tried reversing the phase of your subwoofer? If the overlap region is near 80 Hz, and if the two are out of phase, there may be a cancelation in this region.

Dave

Re: slam is a subjective term [message #19259 is a reply to message #19246] Mon, 21 May 2007 19:50 Go to previous messageGo to next message
GM is currently offline  GM
Messages: 114
Registered: May 2009
Viscount
Greets!

These normally describe an emphasis in the upper-bass (~80-160 Hz) like you get with a Karlson K15 or pro-sound 'sub' or bass-horn.

GM

Re: Standing wave notch [message #19260 is a reply to message #19241] Mon, 21 May 2007 20:33 Go to previous messageGo to next message
GM is currently offline  GM
Messages: 114
Registered: May 2009
Viscount
Greets!

Hmm, 'floor bounce' historically has been used to describe the interference of this standing wave's reflection to the speaker's direct radiation at the listening position, so you normally have two notches from it, though when measuring on-axis at 1 m the two typically sum to a single deeper, broader one.

Standing waves are 1/2 WL issues, so ~1130/2/4 = ~141 Hz.

GM



Re: Standing wave notch [message #19261 is a reply to message #19260] Mon, 21 May 2007 21:12 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18783
Registered: January 2001
Illuminati (33rd Degree)

It's very apparent. I make measurements using an LMS system and when making ground plane measurements, there is no floor bounce. But when I place the same speakers on stands a few feet up, the floor bounce notch is most apparent.


Re: Standing wave notch [message #19262 is a reply to message #19261] Mon, 21 May 2007 21:38 Go to previous messageGo to next message
GM is currently offline  GM
Messages: 114
Registered: May 2009
Viscount
OK, your measurements proves my point that floor bounce isn't just about the driver/floor standing wave.

Re: Standing wave notch [message #19263 is a reply to message #19262] Mon, 21 May 2007 21:43 Go to previous message
Wayne Parham is currently offline  Wayne Parham
Messages: 18783
Registered: January 2001
Illuminati (33rd Degree)

I'm not sure I get your meaning. Floor bounce is caused by a reflection off the floor. It is an interaction between the direct wave and the reflected one. It's easy to calculate and measurements show it to be exactly at the frequency expected. What exactly is it you are trying to say?


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