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 Post subject: Re: Soffit mounting?
PostPosted: Sun Dec 09, 2012 2:53 am 
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Buying or making an extra box for just the bass roll-off is probably not gonna be on my priority-list
You can get a basic crossover for under a hundred dollars new, and probably much cheaper than that on e-bay. It would one option, but if you plan on upgrading your speakers soon, then you could live without it initially, and probably just compensate in your DAW.

You mentioned building one: that's an option too, if you are electronically minded. Barefoot once published a circuit here on the forum for a simple one. Not sure if it is still around...


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 Post subject: Re: Soffit mounting?
PostPosted: Sun Dec 09, 2012 5:31 am 
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Soundman2020 wrote:
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Buying or making an extra box for just the bass roll-off is probably not gonna be on my priority-list
You can get a basic crossover for under a hundred dollars new, and probably much cheaper than that on e-bay. It would one option, but if you plan on upgrading your speakers soon, then you could live without it initially, and probably just compensate in your DAW.

You mentioned building one: that's an option too, if you are electronically minded. Barefoot once published a circuit here on the forum for a simple one. Not sure if it is still around...

Yes, I saw Barfoots circuit here somewhere. I'm into DIY on everything :) but it often takes time and money.

Must be handy with some sort of eq-control for the monitors.
Crossover? Isn't it suppose to be a low-shelf or something?
(Don't worry, I'll find the info there :) )

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 Post subject: Re: Soffit mounting?
PostPosted: Sun Dec 09, 2012 9:01 am 
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Crossover? Isn't it suppose to be a low-shelf or something?
Exactly. And that is what crossover's do. Theoretically it should be shelving, but in practice for small speakers you can just implement it as a high pass (low cut) with 6db/octave roll off, since the speaker response itself rolls off anyway, just a bit lower down.

If you use the output for the mid-range speaker, set the high end to flat response and shelving or high pass on the low end, to correct the power imbalance caused by the soffit.

Or rather, to "un-correct" the speaker's own built-in power balance correction, since it is no longer needed with the soffit. The only reason the speaker has that power balance correction circuit (also known as baffle step compensation) is because the speaker cabinet does not have a large enough front surface. Since you are fixing that with the soffit, you no longer need the baffle stop compensation that the manufacturer built in. So that's what you do with the crossover: the manufacturer increased the bass response by 6 dB below the baffle step, and now you need to undo that by decreasing it again by 6 dB. The concept is simple. Any good crossover will allow you to adjust the frequency and slope to get a close match in reversing the baffle step compensation.

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 Post subject: Re: Soffit mounting?
PostPosted: Sun Dec 09, 2012 6:35 pm 
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Soundman2020 wrote:
Quote:
Crossover? Isn't it suppose to be a low-shelf or something?
Exactly. And that is what crossover's do. Theoretically it should be shelving, but in practice for small speakers you can just implement it as a high pass (low cut) with 6db/octave roll off, since the speaker response itself rolls off anyway, just a bit lower down.

If you use the output for the mid-range speaker, set the high end to flat response and shelving or high pass on the low end, to correct the power imbalance caused by the soffit.

Or rather, to "un-correct" the speaker's own built-in power balance correction, since it is no longer needed with the soffit. The only reason the speaker has that power balance correction circuit (also known as baffle step compensation) is because the speaker cabinet does not have a large enough front surface. Since you are fixing that with the soffit, you no longer need the baffle stop compensation that the manufacturer built in. So that's what you do with the crossover: the manufacturer increased the bass response by 6 dB below the baffle step, and now you need to undo that by decreasing it again by 6 dB. The concept is simple. Any good crossover will allow you to adjust the frequency and slope to get a close match in reversing the baffle step compensation.

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Thanks!

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 Post subject: Re: Soffit mounting?
PostPosted: Tue Dec 11, 2012 5:44 pm 
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Is it right that a reason why active monitors have been so popular the last 10-20years, is the possibility to tune the bass right for free-standing placement?
And if I go soffit-mounting with passive speakers, the bass-fix is not so needed in the first place?

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 Post subject: Re: Soffit mounting?
PostPosted: Wed Dec 12, 2012 3:33 am 
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Not really, no. Active monitors are popular (I think) because they are "all in one". You don't need a separate amplifier, equalizer, crossover, delay, etc. Everything has been designed together to work as an integrated unit. You just plug it in and it plays, unlike a passive speaker where you need to add other things, cable them together, then calibrate and tweak to get the same result. IMHO.

And ALL speakers suffer from power imbalance, or "baffle step response", regardless of whether they are passive or active, or any other factor. This is related to the size of the cabinet and the frequency response of the speaker, nothing else. It is caused by the fact that wavelengths that are smaller than the dimensions of the cabinet tend to be projected forwards, into half space, while wavelengths that are larger than the dimensions of the cabinet tend to wrap around behind it, radiating into full space. The area around the transition frequency, where waves are roughly the same size as the dimensions of the speaker cabinet, is where the "baffle step" occurs on all speakers, active or passive. So high frequencies (shorter waves) are radiated into half space, and therefore are twice as loud as the lower frequencies (longer waves) that are radiated into full space. There is a difference of 6 dB between the two (twice the intensity = 6 dB).

The advantage of active speakers here is that the manufacturer can also build in controls that allow you to correct for this problem, if your speaker is located near a wall, or in a soffit. That is harder to do in a passive design. You can still compensate, of course, but you usually need an external crossover to do it.

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 Post subject: Re: Soffit mounting?
PostPosted: Wed Dec 12, 2012 5:31 am 
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Thanks a lot!

But when soffit-mounting, isn't the point that sound below the baffle-step is directed into half space?
Or does this just happen to some degree, so let's say I'd only need a 3db boost below the baffle step?

Great info for me, as I'll need a plan for speaker/amp-type, set-up and placement :)

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 Post subject: Re: Soffit mounting?
PostPosted: Wed Dec 12, 2012 5:40 am 
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But when soffit-mounting, isn't the point that sound below the baffle-step is directed into half space?
Exactly! And since you have now corrected the 6 dB power imbalance with the soffit, you no longer need the electronic correction. The manufacturer had to design that inside the speaker for people who don't soffit mount, and therefore do have their speakers radiating into full space.

Quote:
Or does this just happen to some degree, so let's say I'd only need a 3db boost below the baffle step?
You might need less, depending on how the rest of the room loads the speaker. There are also more complex things going on, such as impedance mismatch between the speaker cones and the room volume, that could affect the response. But you will very likely need more than 3 dB.

Soffits also correct other issues: they eliminate SBIR completely, for example, and also totally prevent first reflections off the front wall, edge diffraction, comb filtering, phasing, and a few other unpleasant things.

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 Post subject: Re: Soffit mounting?
PostPosted: Wed Dec 12, 2012 5:56 am 
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Thanks!

It seems like the bottom-line for me is aiming for some active speakers with bass-shelf, like the Adam A7.
Would be easier than eq, amp, speakers and advanced analysis.

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 Post subject: Re: Soffit mounting?
PostPosted: Wed Dec 12, 2012 11:40 am 
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like the Adam A7.
Ahh, yes!!!! No question about that. I'm 100% with you on that. Of course, I'm probably just a bit biased, since I own a pair of A7's... :)

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 Post subject: Re: Soffit mounting?
PostPosted: Wed Dec 12, 2012 5:38 pm 
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Soundman2020 wrote:
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like the Adam A7.
Ahh, yes!!!! No question about that. I'm 100% with you on that. Of course, I'm probably just a bit biased, since I own a pair of A7's... :)

Hehe :)

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 Post subject: Re: Soffit mounting?
PostPosted: Thu Dec 13, 2012 3:54 am 
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Adams A7 soffit mounted.

http://www.johnlsayers.com/Studio/Pages/Somewhere.htm

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 Post subject: Re: Soffit mounting?
PostPosted: Thu Dec 13, 2012 4:52 am 
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John Sayers wrote:

Thanks!
Very interesting to see.
Adams S25A it says..

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 Post subject: Re: Soffit mounting?
PostPosted: Mon Dec 17, 2012 8:33 am 
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Adams S25A it says..
Very similar design to the A7, A7X, A8X, etc. All from the same family, with similar characteristics. John's point was how you mount them so that the front panel of the speaker is flush with the soffit face.

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 Post subject: Re: Soffit mounting?
PostPosted: Tue Jan 07, 2014 10:23 pm 
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The thing that bugs me most with flush mounting is that on one hand such importance is placed on a hard, flush, uninterrupted baffle.. but then others recommend use of 3-6" of absorption which makes the front baffle neither flush nor hard.

Then there's the support of the monitors. The kind of framing I see so often implemented really contradicts the typical emphasis on heavy dense stands that are fully decoupled from the room. 5/8" plywood and soft framing lumber?

Lastly, it seems there should be a significant difference depending on whether you mount them in boxes with only a few mm of space rather than a space big enough for adjustable shelves etc.

I'm trying to process it all but it seems there are some contradictions with the matter?


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