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-   -   OB Bass Excursion (http://www.diyaudio.com/forums/multi-way/220595-ob-bass-excursion.html)

Silent Screamer 28th September 2012 03:19 PM

OB Bass Excursion
 
Just trying to get some sort of an idea how far a larger OB bass driver should move in regular music use.

The reason I ask is that I have my new 18" Tc Sounds Pro 5100 (only the one) just sitting propped up on the floor.

It seems to put out a reasonable amount of sound (although currently crossed over a little high ~300Hz) but I notice the cone barely moves.

I keep reading that you need drivers with a big excursion and mine is capable of some fairly big numbers (several inches), but the cone would be lucky to be moving .5mm-1mm.

Just trying to work out what is normal for OB.

Rudolf 28th September 2012 04:01 PM

Quote:

Originally Posted by Silent Screamer (Post 3182483)
Just trying to work out what is normal for OB.

What's "normal" for one man is total boredom for the next and freakingly venturesome for yet another. There are easily 10 dB SPL difference between what people would consider nice loud bass under the same circumstances. And there is probably a full octave between what people would consider nice deep bass. Now compare 80 dB at 50 Hz to 90 dB at 25 Hz - excursion demand will increase more than tenfold between those two.

mondogenerator 28th September 2012 09:42 PM

Interesting thread. I have wondered the same myself, but also in ripole type baffles. Is there a way to calculate, even just spproximate, with a given BL, mms and CSA? I was considering a dual driver 18 ripole, and Xmax of 4mm. I had the same concerns.

Silent Screamer 28th September 2012 10:42 PM

I take your point that bass is extremely subjective and therefore hard to define, but my question is more based around the cone movement. What I am trying to work out is what is a normal or a typical amount of movement?

What I am trying to determine from the question is... Can you go too big with a bass driver? Or can it be too beefy? For example I can use an excavator to dig a hole to put in a pot plant, or I could use a spade or shovel (depending on what you call it in your respective countries).

In OB where there isn't a lot to load the driver, can a driver be too heavy duty?

Consider this for a moment... If the cone didn't have a surround it would move more freely and therefore further in and out, if the surround was super heavy duty would it become a limiting factor in developing "deep bass" (whatever our own personal definition may be)?

Beau 28th September 2012 11:19 PM

What happened to the other driver? Lost?

Silent Screamer 28th September 2012 11:25 PM

Still sitting in the shipping boxes unassembled, need to put together some kind of baffle or box to prevent damage.

The motor alone weighs 15kgs (33.6 lbs) so not the sort of thing you want rolling around.

studiotech 28th September 2012 11:57 PM

We don't believe any of it until we see picts! Newbies.... ;)

sreten 29th September 2012 12:52 AM

Quote:

Originally Posted by Silent Screamer (Post 3182976)

What I am trying to determine from the question is... Can
you go too big with a bass driver? Or can it be too beefy?

Hi,

Yes, of course you can. But .... the main parameter is volume displacement.

As long as you have enough power it determines how low you can go
versus how loud you can go. Only if the driver goes lower and louder
than you really need is it wrong, but given most need a given loudness
level how can anybody not like it being able to go lower (with EQ) for
their preferred (maximum) loudness level, unless they e.g. don't have
the right amplifier power to use the driver properly with the right EQ.

rgds, sreten.

Pallas 29th September 2012 12:57 AM

Quote:

Originally Posted by Silent Screamer (Post 3182483)
Just trying to get some sort of an idea how far a larger OB bass driver should move in regular music use.

The reason I ask is that I have my new 18" Tc Sounds Pro 5100 (only the one) just sitting propped up on the floor.

It seems to put out a reasonable amount of sound (although currently crossed over a little high ~300Hz) but I notice the cone barely moves.

You're going to need a lot of EQ to get deep bass out of that driver in an OB.

Put a 30Hz, 12dB/oct lowpass on it. And feed it decent power. Then you'll see it move a bit!

Silent Screamer 29th September 2012 01:30 AM

5 Attachment(s)
Quote:

Originally Posted by studiotech (Post 3183052)
We don't believe any of it until we see picts! Newbies.... ;)

Yea of little faith, here you go ;)

I'm not necessarily saying I am unhappy with the amount of bass, just that I expected the cone to move more, I do realise that because the sheer size of the cone it doesn't need to move much to move a lot of air.

If I rest my fingers on the cone it barely seems to be moving, so I was wonder why does everyone chase so much Xmax when it doesn't seem to use it.

Just wondering if a lighter weight driver might do a better job...


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