How important is bass management?

[sergeauckland]

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.

Rolling of the mains doesn't need DSP, a simple even first order filter is better than nothing (i.e. a capacitor in series). When I built a 2 1/2 way system for my son at University, I made a simple active filter with two cheap opamps, and it made a huge difference to the power handling and distortion of the mains which were small Mission 'speakers suitable for a college bedroom.....although the sub was wardrobe sized....

S.

 

[Ron Texas]

Rolling of the mains doesn't need DSP, a simple even first order filter is better than nothing (i.e. a capacitor in series). When I built a 2 1/2 way system for my son at University, I made a simple active filter with two cheap opamps, and it made a huge difference to the power handling and distortion of the mains which were small Mission 'speakers suitable for a college bedroom.....although the sub was wardrobe sized....

S.

Do you have a formula for a first order high pass filter? Parts express sells second order filters for under $20 each. They have iron core inductors and I have no idea of how good they are.

https://www.parts-express.com/80-hz-high-pass-8-ohm-crossover--266-458

Here is a line level gadget, 2nd order:
https://www.parts-express.com/harrison-labs-fmod-inline-crossover-pair-70-hz-high-pass-rca--266-272

What do you think? Hard to go wrong at those prices.

 

[sergeauckland]

Do you have a formula for a first order high pass filter? Parts express sells second order filters for under $20 each. They have iron core inductors and I have no idea of how good they are.

https://www.parts-express.com/80-hz-high-pass-8-ohm-crossover--266-458

Here is a line level gadget, 2nd order:
https://www.parts-express.com/harrison-labs-fmod-inline-crossover-pair-70-hz-high-pass-rca--266-272

What do you think? Hard to go wrong at those prices.

For a first order, i.e. 6dB/octave filter, it's effectively a series capacitor. The formula is F=1/6.3CR where F is the 3dB frequency, C is the capacitance in Farads and R is the shunt resistance in ohms, which could simply be the input impedance of the following amplifier.

As an example, if the amp has an input impedance of 10kohms, and F is 80Hz, C works out to near enough 200nF. The 6.3 term is 2Pi near enough.

As to the Parts Express filters, I wouldn't bother with the passive one, as that's just putting more stuff in series with the loudspeaker, but the in-line ones seem good value. What I don't see is what is their input impedance or attenuation, but as you say, at that price worth a punt.

S.

 

[Ron Texas]

As to the Parts Express filters, I wouldn't bother with the passive one, as that's just putting more stuff in series with the loudspeaker, but the in-line ones seem good value. What I don't see is what is their input impedance or attenuation, but as you say, at that price worth a punt.

S.

http://www.hlabs.com/

More info on their site. No attenuation spec is given for the FMOD, but an old quote from The Absolute Sound claims a fraction of a db.

http://www.hlabs.com/products/crossovers/index_files/Page1771.htm

Going passive is a whole new way of looking at the problem.

 

[Juhazi]

IMO only reasonable solution is to purchase a Minidsp 2x4HD and some measurement system, to set matching acoustic slopes. The biggest problem is to get adequate measurements, semi-nearfield groundplane seems to be best. Other challenge is that you need separate pre- and power amp for main speakers too.

Acoustic slopes are what really counts, datasheets information is far from reality. Being able to get delays right is almost as important, and this is not often possible without setting some delay to main speakers.

One nice feature of dsp is that you can easily try different configurations and save them. I've been doing this for many years and several systems. My favourite is acoustical LR2 around 100Hz. Double subs near mains is really nice! I haven't tried multisub systems.

 

[sergeauckland]

http://www.hlabs.com/

More info on their site. No attenuation spec is given for the FMOD, but an old quote from The Absolute Sound claims a fraction of a db.

http://www.hlabs.com/products/crossovers/index_files/Page1771.htm

Going passive is a whole new way of looking at the problem.

Yes indeed.

If 24dB/octave is enough, and you don't need to make changes, I think it would be fine for a subwoofer, then these represent very good value.

Driven from the typically low output impedance of a pre-amp into the 22k or above input of a power amp, they should be fine.

The actual performance will depend on the details of the specific output and input impedance, and their non-adjustable nature will limit application for those who must tune to 1dB, but for 'normal' people, very useful. If I'd known about these twenty years ago, I wouldn't have bothered to make my own crossover for my son's system.

S.

 

[Ron Texas]

When the need arises I would probably roll off the mains at 12 db/octave and use the sub's built in low pass.

 

[invaderzim]

Do you have a formula for a first order high pass filter? Parts express sells second order filters for under $20 each. They have iron core inductors and I have no idea of how good they are.

https://www.parts-express.com/80-hz-high-pass-8-ohm-crossover--266-458

Here is a line level gadget, 2nd order:
https://www.parts-express.com/harrison-labs-fmod-inline-crossover-pair-70-hz-high-pass-rca--266-272

What do you think? Hard to go wrong at those prices.

I got a pair of those high pass filters. They seem very well made. Since my speakers are powered by a SE tube amp which doesn't have its strength in bass and they are smaller speakers (B&W CM5 S2) I figured letting them not bother with trying to do the lower frequencies would be a good thing. On my setup the sound seemed to be (no blind testing) more detailed with them in place.
My listening room is also the living room leaving things like speaker and subwoofer placement are limited so, for me, having the sub do more of the bass wasn't the best solution. With better sub placement I think it would be a really good improvement. But with the current placement there were places in the room where the bass was too strong.

 

[direstraitsfan98]

I believe the concept that REL touts of not high passing is an antiquated and relic of an age when it was not well understood how to manage bass. As someone mentioned earlier, people like Peter O'Toole have done a lot of research into it and published peer reviewed papers on the matter, and now you have companies applying all of the knowledge we learned to their subwoofers. My personal take on it is that you should absloutely cross the sub over to handle everything in the low end. I suppose it would be specific to each speaker but the best bet would probably be around 80hz, when the ear becomes less sensitive to directional of the sound.

 

[Ron Texas]

@direstraitsfan98 it's Floyd Toole. Peter O'Toole was an actor who played TE Lawrence in Lawrence of Arabia. I think it depends. On the 305's there is apparently a built in high pass filter to get rid of some woofer motion. I also have the sub set a bit high an are lowering it with EQ which applies to everything. Combined with the -3db shelf filter in the speakers I probably have a 6 db reduction across the band. It's not the ultimate, but appears to be enough. Based on experience and this discussion, I am pretty sure the LS50's (whenever they get back here) need to be high passed, somewhere around 70 hz.

 

[direstraitsfan98]

@direstraitsfan98 it's Floyd Toole. Peter O'Toole was an actor who played TE Lawrence in Lawrence of Arabia. I think it depends. On the 305's there is apparently a built in high pass filter to get rid of some woofer motion. I also have the sub set a bit high an are lowering it with EQ which applies to everything. Combined with the -3db shelf filter in the speakers I probably have a 6 db reduction across the band. It's not the ultimate, but appears to be enough. Based on experience and this discussion, I am pretty sure the LS50's (whenever they get back here) need to be high passed, somewhere around 70 hz.

damnit I feel silly now.
And yeah of course its gonna depend. I've always wanted to supplement the bass of my 4367's with some subwoofers, but I have no idea where I would cross the mover to. 30hz? 50? 80? 100?

 

[Thomas savage]

It might well of been Peter O'Toole that came up with the REL recommendations.

 

[Ron Texas]

It might well of been Peter O'Toole that came up with the REL recommendations.

Floyd and Peter are/were both high performers in their respective fields.

 

[direstraitsfan98]

Woooooooooo, I am the ghost of Peter O Toole! Stop confusing me with Floyd WooooOOO!

 

[jhaider]

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.

I think that's overthinking things. I used the basic balanced miniDSP 2x4, and later a 10x10HD, for bass management for years, and it never got in the way. The sound was always better with it in the chain than without it.

 

[Ron Texas]

I think that's overthinking things. I used the basic balanced miniDSP 2x4, and later a 10x10HD, for bass management for years, and it never got in the way. The sound was always better with it in the chain than without it.

After having the discussion about passive high-pass, I don't think it's such a big deal. Anyway, my Crown XLS 1502 can do it by pushing a few buttons. I haven't had the LS50's here since mid June. Since that time I have rearranged the room and the acoustics are very different and my understanding of REW and Rephase has improved.

 

[rhollan]

If you don't roll off the mains a lot of LFE power goes to them (assuming they don't have a low end impedance rise). They are inefficient at reproducing this so much is dissipated as heat. Heat = bad, yes?

 

[NiagaraPete]

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 universa

SVS does as well.

 

[LTig]

If you don't roll off the mains a lot of LFE power goes to them (assuming they don't have a low end impedance rise). They are inefficient at reproducing this so much is dissipated as heat. Heat = bad, yes?

Yes, and also they don't show lower IMD and higher SPL capability.

 

[rhollan]

I'll share my setup. It's a bit odd since I use an Oppo 205 as a 2 channel purist CD spinner AND an 8 channel DAC for a Dirac Live corrected Sony ES UBP-X1000ES 4k Bluray player, the latter audio signal going into the Oppo's HDMI input. Dirac live Room correction for the Sony is handled by a miniDSP DDRC-88D connected via HDMI to SDI and SDI to HDMI converters and an AJA SDI to AES audio embedder/deembedder. An HDFury Diva sorts out HDMI switching, audio over HDMI and eARC.

The analog side of things has the balanced stereo output of the Oppo 205 going into an Emotiva XSP-1 crossing over each channel high-passed at 120 Hz into a BG Radia 520i speaker and full-range into the line input of a colocated Rythmic Audio F-12 Subwoofer XLR3 amp. I run stereo subs as the 520i starts to roll off at 120 Hz and is 6dB down at 80 Hz.

LFE from the Oppo 205 goes into the LFE input of the Rythmic F-12 sub XLR3 amp and is combined there with the per-channel line input low‐passed by the sub at 120 Hz. XSP-1 crossover is 12 dB/octave for the high-pass.

The Oppo 205 crosses Surround and Center channels into LFE at 80 Hz and distance and level balances all channels. Crossover is 12 dB/octave.

Amps are a 3 channel Apollon Purifi amp for left, center, and Right, and Apollon Purifi 4 channel amp for surrounds. Surround speakers are BG Radia 420i and center Is a BG Radia 220i.

The DDRC-88D ALSO applies bass management to center and surround channels, at 80 Hz and 12 dB/octave prior to Dirac Live. Combined with the Oppo 205, this results in a 24 dB/octave center and surround crossover.

For those who care, analog interconnect cables are Mogami Gold with Neutrik

connectors.