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Old 5th October 2008, 01:00 PM   #1
mikee55 is offline mikee55  United Kingdom
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Default Where to crossover, don't want audible bass

I have an IB and my crossover was at 40hz. I found this to be too annoying. Although the low frequencies come through how I want them to, upper bass seems dominant. I have floorstanders to do bass duty, so how can I keep the bass outta my ceiling IB?

I use pre out off of my main amp, followed by a Linkwitz 24db low pass, yesterday I changed the values to give me 18.04hz, I figured this would smooth over the upper bass and allow some lo stuff still to get through, and a variable gain block to lift the output being as low frequencies are usually quiet in the recording. Now I don't hear nothing??

Whats up with that???

Cheers Mike
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Old 5th October 2008, 01:21 PM   #2
Eva is offline Eva  Spain
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Suppressing audible upper bass in subwoofers is a misconception, you can't do that with conventional analog filters and you shouldn't do it anyway. Improve the system to handle it properly instead.
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Old 5th October 2008, 01:49 PM   #3
mikee55 is offline mikee55  United Kingdom
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Default Hi Eva

Quote:
Suppressing audible upper bass in subwoofers is a misconception, you can't do that with conventional analog filters and you shouldn't do it anyway.
Please could you go into more detail, I know its a Sunday, but I'm curious.

Thanks, Mike
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Old 5th October 2008, 08:47 PM   #4
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If your IB has no EQ connected to it then it probably is outputting more dB at 80Hz than at 20Hz, meaning your 24dB/oct xo is not working properly.

I'd suggest buying a digital EQ like the behringer feedback destroyer and using it to EQ your IB flat from 120HZ down. Then apply your xo.

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Old 5th October 2008, 10:28 PM   #5
mikee55 is offline mikee55  United Kingdom
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Default Hi RobWells

I had no EQ, just a input mixer, 24db Linkwitz low pass and some gain. I used Rod Elliott's circuits. I wish I could afford a Digital EQ, that ain't gonna happen for a while, hence the traditional analogue circuits.

I'm just using a single 12" car driver in the corner of my ceiling. In the opposite corner, on the floor I have my sofa, here the output is most potent, the bedroom upstairs gets vibrated and things begin buzzing. I play a fair bit of Drum n Bass of late and the IB plays all the bass lines as well as the low stuff. I don't mind, but her indoors doesn't give it much WAF. I thought I could just lower the crossover frequency, but its not working out that way. I've upped the gain and the cone flaps a bit, and I hear deep bass, but I gotta turn up the overall volume, guess I need EQ? Should I try Rod's http://sound.westhost.com/project28.htm ???

Cheers Mike
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Old 5th October 2008, 11:09 PM   #6
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The problem with EQ is that if you cant measure the sound then what are you going to set the EQ to ?

I think in your situation I'd try the driver in a conventional vented box tuned low. - search for EBS subs.

What driver is it and do you have the TS parameters ?


Rob.
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Old 6th October 2008, 12:18 AM   #7
mikee55 is offline mikee55  United Kingdom
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Default Hi RobWells

Quote:
The problem with EQ is that if you cant measure the sound then what are you going to set the EQ to ?
I didn't understand what you wrote. Would not adding boost at a low frequency help? In Wavelab, I can turn up the gain at any frequency, as my Avatar shows, in winamp, I have a plugin that lets me draw an EQ shape
Click the image to open in full size.Click the image to open in full size.
Its an SPLX car sub, I have the T/S 's somewhere. I did have it in a Linkwitz Transform system, which richie00boy helped me design.

It sounds better without a box

Mike
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Old 6th October 2008, 05:58 AM   #8
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What I meant was how do you know whether to boost at 20Hz or 35Hz(as examples) unless you measure what the sub is doing in room? and how much boost is needed?.

Rob.

Car drivers tend to start rolling off higher, hence the suggested LT circuit. Only prob is a single 12" won't do much at 30Hz.

You could try the LT on the IB but I'd suggest putting a steep high pass on it to protect the driver.

Another option would be to try a 6th order BP.
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Old 6th October 2008, 09:11 AM   #9
mikee55 is offline mikee55  United Kingdom
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Default Hi RobWells

Thanks for replying. When it comes to it, do you have to have more drivers and watts to equal the spl of the mains? I know proper IB's have several drivers on a manifold with several hundred watts pushed into them, but surely you don't have to have all that? My mains probably only use a couple of watts, the amp I'm using for my IB is a car unit, bridged to maybe 70 watts. Maybe I'm missing the whole thing about Loudness, but I expect several hundred watts in my house, and I'm gonna need an Artexer/Plasterer to regularly patch up my walls and ceilings

Cheers Mike
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Old 6th October 2008, 09:37 AM   #10
Eva is offline Eva  Spain
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An infinite baffle system (or a dipole) does ovbiously not exhibit a flat frequency response without some compensation, but there is another problem with audible bass and (sub)woofers:

Frequencies in the 80HZ to 400Hz are so much more audible than the ones in the 20Hz to 80Hz range that no analog filter of reasonable order allows to attenuate them below perception. 12dB/oct leaves them barely at the same perception level. 24dB/oct provides some attenuation. Analog filters above 24dB/oct are not recommended due to the increasing group delay.

My advice is to ensure that there are no peaks or nasty out of band resonances in the low frequency system and to place the midbass system near.
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