OB Bass Excursion

[Silent Screamer]

Originally Posted by Pallas

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!

I don't need super low bass out of them as I plan to buy a pair of these for some sub cabinets.

LMS-Ultra 5400 18″ Driver | TC Sounds

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18" doing 20Hz sine wave:

Eminence SigmaPro18 doing 20Hz.AVI - YouTube

No other numbers. Not much power input, and absolutely not much SPL output. It's doing that very quietly, really.


On OB, it doesn't need much power (and motor) to make the woofer run out of Xmax.

http://www.linkwitzlab.com/faq.htm#Q6

[Silent Screamer]

Here is a picture of the current xover...

Clearly you can see from the pictures the driver sitting on the floor isn't going to produce optimal bass. So not overly worried about bass output, was just curious about the excursion.

I am still trying to work out how to use the software, so what you see here is probably far from what the software is capable of, it just needs me to catch up.

Just sort of worked out how to use the notch filters. Still have lots to work out.

[Silent Screamer]

Also found this website which suggests I am on the right track... Designing Loudspeakers - Part 15 Open Baffles and Bass

[Silent Screamer]

Originally Posted by CLS

On OB, it doesn't need much power (and motor) to make the woofer run out of Xmax.

Frequently Asked Questions

See this is what I am trying to work out what moves the cone like that. I have that 18" hooked up to a 1000w (4ohm) per side Rotel digital amp and it is bearly moving.

So clearly it's not a lack of available power. So either I am currently not playing music in that frequency range to move the driver sufficiently, or the lack of any baffle whatsoever s making it roll off too serverly.

Time to put a test tone disk in and see what that tells me.

[SirByrd]

This might sound like a dumb question, but if you are using both coils, are the wired in proper phase?

[Silent Screamer]

Yep the booklet shows two different configurations serial and parrallel have them hooked up 2 + 2 for a 4ohm output, serial produces 1ohm (which I think my amp might just protest slightly)

Just threw in the test tone disk to see what it had to tell me...

Quite suprising really:
31Hz just hear the slightest noise
40hz jumped up in SPL a fair bit but still not over the top loud
50hz very similar to 40
63hz again fairly flat
80hz, 100hz fairly even
125hz slight dip
160hz back to previous level
200hz getting louder
250hz slighly louder again
315hz loudest of all
400hz rolling off and quietening down
500hz lower still
630hz faded right out down near 40hz level

This tells me two things... firstly the level of bass I am getting out of the driver is not low compared to the dual 6.5 Revelators. Without hooking the Cremonas up I would say they are very roughly on par, and probably expains why the bass while not over the top, is still half decent.

Second thing it tells me is that Robert from Ground Sound knows how to make a crossover that works

[studiotech]

Thx for the picts. So, once you get some baffles worked up and some measurements in hand, then we throw some low shelving EQ at it and you'll see some movement. You need to start collection some good bass tracks in the mean time. Find some nice upright bass to test for tonality and pitch definition and then some ridiculous electronica for some brown note stuff.

Also, find Maxwell's Embrya. There is some good, baby makin' bass on that disc. Very clean and well recorded and very dynamic for modern R&B/Soul.

Greg

[Silent Screamer]

Hey Greg I have Ghetto of my Mind by Ricki Lee Jones which is supposed to be a bass buster.

Well to be semi scientific I just mapped the frequency response using something other than my ear...

Must say it doesn't look too shabby at all. Going to remove the notch filter and try it again with just a straight up crossover (will also tell me if my playing / testing actually did anything).

[Silent Screamer]

And here is one with just a basic crossover.

Note that from 50hz to 200hz it kept coming up with a message saying turn down the mike gain (which was already all the way down) I did it at the same volume as before, for a back to back comparison, I dont know if the software auto limited the results at all.

Kind of drifted off topic from my original question but it would seem you can still produce the numbers to a large degree with the cone barely moving.