How important is bass management?

[Ron Texas]

"For this comparison I used my Bowers & Wilkins 705 S2s ($2500/pair) run full-range, and reinforced below 50Hz by two SVS SB-4000 subwoofers ($1499.99 each) -- total price $5499.98. "
Diego Estan in a review of the KEF R11 at SoundStage HiFi

Is this guy on to something, or is he missing out by not high passing his B&W's? I ask this because unless one has a built in bass management solution (A/V receiver, Crown XLS, etc) another piece of hardware is required, and the good stuff can be costly.

I am doing this right now with my LSR 305 Mk II's. The sub is set to roll off very low and the JBL's are set for -3db shelf. The system is equalized using REW, Rephase and the Foobar2000 Convolver, nothing exotic.

 

[Kal Rubinson]

If we are talking about stereo (where there is no LFE), the answer is yes, you need BM unless you are very lucky or very insensitive. Admittedly, we are all relatively insensitive at those frequencies. The user needs tools, as you have, to assure there is no excess or cancellations in the range where the mains overlap with the subs.

 

[watchnerd]

"For this comparison I used my Bowers & Wilkins 705 S2s ($2500/pair) run full-range, and reinforced below 50Hz by two SVS SB-4000 subwoofers ($1499.99 each) -- total price $5499.98. "
Diego Estan in a review of the KEF R11 at SoundStage HiFi

Is this guy on to something, or is he missing out by not high passing his B&W's? I ask this because unless one has a built in bass management solution (A/V receiver, Crown XLS, etc) another piece of hardware is required, and the good stuff can be costly.

I am doing this right now with my LSR 305 Mk II's. The sub is set to roll off very low and the JBL's are set for -3db shelf. The system is equalized using REW, Rephase and the Foobar2000 Convolver, nothing exotic.

REL advocates doing exactly what he's doing (run the mains full range, add sub).

So the "high pass the mains" school of thought doesn't seem to be universal.

 

[watchnerd]

If we are talking about stereo (where there is no LFE), the answer is yes, you need BM unless you are very lucky or very insensitive. Admittedly, we are all relatively insensitive at those frequencies. The user needs tools, as you have, to assure there is no excess or cancellations in the range where the mains overlap with the subs.

I'm not following their recommendation, but here is what Martin Logan recommends in the documentation that came with the two Dynamo 1100X subs I got about a 6 weeks ago:

"As a general rule, the Low-Pass Filter should be set at a value approximately equal to (or below) 70% of your main speaker’s lowest frequency response. For example, your speaker’s frequency response goes down to 43Hz. 70% of 43Hz equals 30.1, so you should set the subwoofer’s low pass filter to 30Hz. We advise that once you try the recommended setting using the formula above, you should try the surrounding settings as well. If you are uncertain of your main speaker low-frequency response, start with a setting of 35Hz. You will not harm anything by experimenting with different settings."


So, basically, run the mains full range, add subwoofer.

 

[LTig]

REL advocates doing exactly what he's doing (run the mains full range, add sub).

So the "high pass the mains" school of thought doesn't seem to be universal.

Unfortunately it seems. There was a thread here not long ago dealing with this subject, and there may be few situations where not high passing the mains may have an advantage. Not in your case I fear since a speaker with a small woofer should always be high passed.

Actually adding a sub with mains high pass not only improves the bass but also the mids since the woofer of the mains has much lower distortion (HD and IMD).

 

[watchnerd]

Unfortunately it seems. There was a thread here not long ago dealing with this subject, and there may be few situations where not high passing the mains may have an advantage. Not in your case I fear since a speaker with a small woofer should always be high passed.

Actually adding a sub with mains high pass not only improves the bass but also the mids since the woofer of the mains has much lower distortion (HD and IMD).

Oh, I'm high passing mine at 80 Hz.

What I *didn't do*, though was set the sub crossover to 70% of 80 Hz (we could be one interpretation of Martin Logan's instructions). I just set it to low pass at 80 Hz, as well.

 

[jhaider]

There are different approaching to bass management. I think there may be cases when not "managing" (i.e. high-passing) the mains is a good idea: if you have mains with large woofers and either a very low reflex tuning (at or around 20Hz) or excursion control from closed boxes, then it may be worthwhile to experiment with folding the subwoofers into the mains, starting with one subwoofer and adding the others sequentially. Here's a good write-up of the method: https://mehlau.net/audio/multisub_geddes/

As a counterpoint, Dr. Toole uses speakers that meet the above criteria (3x8" woofers tuned to around 20Hz) yet he employs bass management.

For LSR305s I think everyone would agree that you're throwing away most of the potential headroom gains from subwoofers if you don't manage them. A miniDSP 2x4 Balanced is an additional box, but a cheap and easy fix.

 

[watchnerd]

For LSR305s I think everyone would agree that you're throwing away most of the potential headroom gains from subwoofers if you don't manage them. A miniDSP 2x4 Balanced is an additional box, but a cheap and easy fix.

I could see not bothering with something as small as the LSR305 if the listening situation was extreme nearfield (like on a desktop, ears 18" away) and you're only using it to watch undemanding streaming TV shows or some such.

But otherwise, yeah, the woofers are little and the amps aren't very powerful.

 

[Jim777]

I remember B&W recommending the foam plugs in the bass ports if using a sub. It'll create a nice rolloff and the sub can be adjusted to complement that nicely. What's wrong with that?

 

[watchnerd]

I remember B&W recommending the foam plugs in the bass ports if using a sub. It'll create a nice rolloff and the sub can be adjusted to complement that nicely. What's wrong with that?

Dynaudio provides plugs that go with my Contour 20.

I tried plugging the ports and found it crushed the dynamics and did bad things to the imaging and soundstage.

I'm not that surprised, as the speaker was probably voiced / tuned / crossover-designed with the ports open.

 

[Ron Texas]

Thank you everyone. I might be lucky because when I played a track which used to cause large woofer excursions on LS50's without high passing the mains, the excursions were absent on the JBL's. It's possible the -3db shelf plus EQ for the sub is enough to eliminate the problem.

I agree with those who don't like the sound of plugged ports.

 

[DonH56]

I disagree with REL but what do I know. Oh, so do Toole and a bunch of other highly-regarded experts so maybe it's not just me (N.B. I am NOT a expert!) Running the mains full-range and using the main amplifier's output to drive the sub so the sub's sound is matched to the mains are both things I do not believe serve the best interests of the sound. IME, measurements and listening tests confirm my opinion.

 

[LTig]

Thank you everyone. I might be lucky because when I played a track which used to cause large woofer excursions on LS50's without high passing the mains, the excursions were absent on the JBL's. It's possible the -3db shelf plus EQ for the sub is enough to eliminate the problem.
.

I rather think that the JBLs have an internal high pass filter to keep away those frequencies the woofer chassis cannot handle in the first place. This allows those speakers to play louder than one would expect.

 

[sergeauckland]

I'm not following their recommendation, but here is what Martin Logan recommends in the documentation that came with the two Dynamo 1100X subs I got about a 6 weeks ago:

"As a general rule, the Low-Pass Filter should be set at a value approximately equal to (or below) 70% of your main speaker’s lowest frequency response. For example, your speaker’s frequency response goes down to 43Hz. 70% of 43Hz equals 30.1, so you should set the subwoofer’s low pass filter to 30Hz. We advise that once you try the recommended setting using the formula above, you should try the surrounding settings as well. If you are uncertain of your main speaker low-frequency response, start with a setting of 35Hz. You will not harm anything by experimenting with different settings."


So, basically, run the mains full range, add subwoofer.

To me, this is wrong. Removing the LF below the main's capabilities reduces distortion significantly by not asking the mains to try and reproduce something they're not capable of. I would roll off the mains somewhere above their -3dB point, and pass all the rest to the subs. With large mains, this may not be very important, but with smaller 'bookshelf' type mains, it can result in very much lower distortion and improved SPL.

Interestingly, Genelec do this in their small actives, like my 1029As, they have a high-pass filter on the bass that removes the extreme LF the 1029As are incapable of reproducing.

S.

 

[Ron Texas]

I rather think that the JBLs have an internal high pass filter to keep away those frequencies the woofer chassis cannot handle in the first place. This allows those speakers to play louder than one would expect.

That would explain what I am experiencing. It's a nice feature. I don't know how JBL puts all that stuff in a box for $130 a piece.

 

[30 Ounce]

I run my B&W Signature 805 full range and low pass my Velodyne HGS15 at about 60. The Velodyne is EQ’d with a parametric EQ to remove room modes at the listening position. All set up and measured with REW. Measuring is the only way to set up a subwoofer. I did try using a high pass on the main speakers but it always seemed to veil or lose something so I abandoned it.

 

[daftcombo]

Bass sounds so different when you move accross the room. Here there's too much, here not enough. Perhaps putting multiple subs can help, but with only EQ I gave up. I try to keep FR of the speakers (by a close-field measurement) flat down to 40 Hz (50 Hz can be enough on most music, 20Hz is nice on some electro and movies).

 

[Ron Texas]

I run my B&W Signature 805 full range and low pass my Velodyne HGS15 at about 60. The Velodyne is EQ’d with a parametric EQ to remove room modes at the listening position. All set up and measured with REW. Measuring is the only way to set up a subwoofer. I did try using a high pass on the main speakers but it always seemed to veil or lose something so I abandoned it.

Emphasis added. Before I had a microphone I spent months fiddling with the sub and got nowhere. An inexpensive calibrated microphone, free software and the effort to learn how to use it will take any system up a level and turns a seemingly hopeless subwoofer into a manageable task. That's the most important thing I learned here at ASR, measure.

 

[sergeauckland]

REL advocates doing exactly what he's doing (run the mains full range, add sub).

So the "high pass the mains" school of thought doesn't seem to be universal.

REL's recommended method has the benefit of simplicity, so has commercial value. I can't think of any other reason for recommending running the mains full-range and just adding a sub.

S.

 

[Ron Texas]

REL's recommended method has the benefit of simplicity, so has commercial value. I can't think of any other reason for recommending running the mains full-range and just adding a sub.

S.

How about the expense of adding a good DSP? True, the low end MiniDSP units are inexpensive, but they don't measure very well and process at 48k. As some have pointed out, a high pass filter may not be needed with mains which go down low to start with. I wonder what would happen if this was blind tested? When I get my LS50's back I am going to try it both ways as I can high pass them with my Crown XLS 1502. It's not an expensive unit, but it is also a 48k processor and middling in it's measurements. I don't have a cleaner amp to compare it to.