Speakers optimized for sub blending

[adam2434]

I’ve been playing with a secondary 2.1 music system in the unfinished part of my basement and have made some observations that have got me thinking about speaker designs that are more optimized for subwoofer integration and efficiency.

 

A sealed speaker that is -3 dB at 80Hz is ideal for sub blending with an 80 Hz crossover in the AVR/processor.  This is due to the fact that the sealed speaker’s natural 12 dB/octave sums with the processor’s 12 dB/octave electronic high pass filter, which matches the processor’s 24 dB/octave electronic low pass filter.  The result is flatter response in the crossover region, thus more seamless blending.  These parameters are actually in the THX specifications.

 

I would love to see speakers in the market that are optimized for this.  For example, a largish high-output, low-distortion 2-way bookshelf speaker that is tuned for -3 dB at 80Hz, which would improve sensitivity vs. a lower tuning.

 

With Klipsch’s long history of efficient, horn-loaded designs, I bet they could do this in their sleep, incorporating their newest driver and horn advancements.  These would be speakers that would be truly designed and optimized for subwoofer integration, with higher than typical output/sensitivity, and with lower than typical distortion. 

 

PSA’s speakers appear to be designed around these principles.  I wonder what Klipsch could do at similar or lower price points.

 

Just food for thought…

[Peter P.]

As an alternative, you could make and install a 80Hz 2nd order high pass filter where your speaker wires meet the speaker terminals. There a web sites that will calculate the values for you. You could then use a pair of Heresy's in the manner you describe. This isn't that complicated to build, and look professional.

[pzannucci]

15 hours ago, adam2434 said:

I’ve been playing with a secondary 2.1 music system in the unfinished part of my basement and have made some observations that have got me thinking about speaker designs that are more optimized for subwoofer integration and efficiency.

 

A sealed speaker that is -3 dB at 80Hz is ideal for sub blending with an 80 Hz crossover in the AVR/processor.  This is due to the fact that the sealed speaker’s natural 12 dB/octave sums with the processor’s 12 dB/octave electronic high pass filter, which matches the processor’s 24 dB/octave electronic low pass filter.  The result is flatter response in the crossover region, thus more seamless blending.  These parameters are actually in the THX specifications.

 

I would love to see speakers in the market that are optimized for this.  For example, a largish high-output, low-distortion 2-way bookshelf speaker that is tuned for -3 dB at 80Hz, which would improve sensitivity vs. a lower tuning.

 

With Klipsch’s long history of efficient, horn-loaded designs, I bet they could do this in their sleep, incorporating their newest driver and horn advancements.  These would be speakers that would be truly designed and optimized for subwoofer integration, with higher than typical output/sensitivity, and with lower than typical distortion. 

 

PSA’s speakers appear to be designed around these principles.  I wonder what Klipsch could do at similar or lower price points.

 

Just food for thought…

The problem is really the fact that you need to keep those lower frequencies out of the mid/bass driver.  You really want that done with electronics and not necessarily theoretical speaker roll off.  If not, most of the time, particularly in bass reflex loads, it will just lead to distortion.

Always keep low frequencies managed electronically if possible, high frequencies don't matter as much since most times the diaphragm materials will make a roll off that will minimize distortion unless there is ringing.

[JohnA]

It took me a couple of days to decide how to respond to your post.  First, there is nothing special about an 80 Hz crossover point.  I would want my mains to go as low as possible, at least 40 Hz, low E on a double bass or bass guitar, if possible.  Then, bass instruments will not change timbre from moving from sub to mains.  Second, the crossover point should be controlled by the Pre/pro and set according to the actual performance of the sub and speakers.  Finally, if speakers are to be designed only to play to 80 Hz, they will have to be part of a sub/sat system designed together.  AKA Blose or Gallo (not nearly an good sounding as they pretend). 

[wvu80]

19 hours ago, adam2434 said:

I would love to see speakers in the market that are optimized for this.  For example, a largish high-output, low-distortion 2-way bookshelf speaker that is tuned for -3 dB at 80Hz, which would improve sensitivity vs. a lower tuning.

There are DIY speakers that are designed in exactly that way.  See the SEOS (Semi Elliptical Oblate Spheroid) speakers.

http://www.diysoundgroup.com/

 

I have the Fusion 10 Pure.  These are pro audio style high efficiency low distortion 2-way speakers with 10" woofers and a 10" horn (SEOS).  They have an efficiency of 98 db and can handle 300 watts.

 

They sound a little thin when played as a 2-way but when paired with a sub which is how it was designed it delivers a wonderful accurate full range sound with the efficiency of Klipsch horn driven speakers.

 

The problem is our concept of what speakers are, we think in terms of stand alone speakers and we don't tend to think in terms of speaker systems.  Even though my Fusion 10's are technically a two-way, because of the design w/sub they are actually a three-way

 

[adam2434]

Let me clarify the scenario.

 

I am talking about typical bookshelf-sized speakers (2-way with 5.5” to 10” woofer) blending with subs in a 2.1 or multichannel context, using the digital bass management in an AVR or processor, with speakers set to small.

 

AVRs and processors typically apply an electronic 12 dB/octave high pass slope (on speakers set to small) and an electronic 24 dB/octave low pass slope for the sub channel.  Regardless of crossover frequency selected in the AVR/processor, the ideal situation for flat response in the crossover region would be a sealed speaker that starts its natural 12 dB/octave roll-off at the crossover frequency.  This scenario yields a 4^th order 24 dB/octave slope on both sides for the crossover point.

 

80 Hz is a typical crossover frequency for bass management with typical bookshelf speakers.  So, if one had a sealed bookshelf speaker that started it’s acoustic 2^nd order roll-off at 80 Hz (actually -3 dB at 80 Hz would be ideal), the symmetrical 4^th order slope would be in effect, and Hoffman’s Iron Law could enable optimization for sensitivity vs. low frequency extension (that is not needed anyway). 

 

Most bookshelf speakers are ported (which can cause phase issues with sub blending) and are optimized for low frequency extension over sensitivity. 

 

Does this makes sense to folks?

[Ski Bum]

It makes sense.  I'm pretty sure diysoundgroup has some sealed types that would conform.  It's also the approach of the old M&K brand.  Well, at least the sealed alignment, with careful attention that the actual acoustic roll off @80hz was smooth and a genuine 12db/oct per THX specifications.  They were anything but sensitive, but capable of getting quite loud without complaint.  The MPS 150 used three tweets and two 5" mids in order to achieve it's dynamic capabilities.  They had some well earned popularity on the pro side in production and mastering facilities back in their day.

[Paducah Home Theater]

27 minutes ago, adam2434 said:

Let me clarify the scenario.

 

I am talking about typical bookshelf-sized speakers (2-way with 5.5” to 10” woofer) blending with subs in a 2.1 or multichannel context, using the digital bass management in an AVR or processor, with speakers set to small.

 

AVRs and processors typically apply an electronic 12 dB/octave high pass slope (on speakers set to small) and an electronic 24 dB/octave low pass slope for the sub channel.  Regardless of crossover frequency selected in the AVR/processor, the ideal situation for flat response in the crossover region would be a sealed speaker that starts its natural 12 dB/octave roll-off at the crossover frequency.  This scenario yields a 4^th order 24 dB/octave slope on both sides for the crossover point.

 

80 Hz is a typical crossover frequency for bass management with typical bookshelf speakers.  So, if one had a sealed bookshelf speaker that started it’s acoustic 2^nd order roll-off at 80 Hz (actually -3 dB at 80 Hz would be ideal), the symmetrical 4^th order slope would be in effect, and Hoffman’s Iron Law could enable optimization for sensitivity vs. low frequency extension (that is not needed anyway). 

 

Most bookshelf speakers are ported (which can cause phase issues with sub blending) and are optimized for low frequency extension over sensitivity. 

 

Does this makes sense to folks?

 

No not really.    If you wanted a steep slope then just use a DSP.  

 

Basically what you're saying is that the Klipsch PRO-7800-L-THX is as good as you can get if you're going to use a sub.  I can't agree with that.  

 

[adam2434]

4 hours ago, MetropolisLakeOutfitters said:

 

No not really.    If you wanted a steep slope then just use a DSP.  

 

Basically what you're saying is that the Klipsch PRO-7800-L-THX is as good as you can get if you're going to use a sub.  I can't agree with that.  

 

 

Sure, if you have a DSP with that capability.  

 

I believe most AVRs and processors have a fixed 12 dB/octave high pass, at least the ones I’ve owned.

 

I did not say that the that the PRO-7800-L-THX is as good as it gets with a sub, or that any specific speaker would be best.

 

I don't think the point I'm trying to make is coming across.

 

Here’s the typical scenario I’m thinking.

 

One is setting up a 2.1 system based on bookshelf speakers and will be using an AVR with bass management.  An 80 Hz high pass will filter will be chosen because of the balance of low frequency offloading for the bookshelf speakers (increase in amp headroom and reduction in woofer distortion) and minimal sub localization.

 

Say one is looking at two 6.5” woofer bookshelf speaker models of similar quality, cost, and size.

 

Speaker A is ported, -3 dB at 50 Hz, and has a sensitivity of 86 dB @ 1 watt/1 meter.

 

Speaker B is sealed, -3 dB at 80 Hz and has a sensitivity of 90 dB @ 1 watt/1 meter.  Take the 4 dB sensitivity increase with a grain of salt, but let’s assume that there will be a sensitivity increase because the system is designed to roll-off at 80 Hz.

 

All other performance criteria being equal, speaker B should provide a more seamless blend with the sub and would require less power at the same output.  It would be more optimized for sub integration vs. the ported speaker, which is more optimized for stand-alone bass performance.

 

That’s the only point I’m trying to make.

 

I’m not a speaker designer, so I don’t claim to know all the ins-and outs, but I believe the physics support the point.  If they do not, I am all ears to learn.  Any speaker designers on this forum?  

[adam2434]

wvu80, sounds like you like the Fusion 10 Pure.  Did you build them?

 

I've been on the DIY site several times to look at their designs.  I have not found a sealed smaller 2-way on the site though.  I kind of wonder why they port speakers that were designed to be used with subs.  I've even read comments from Jeff Bagby where he indicates that sealed speakers are easier to integrate with subs.

 

 

[pzannucci]

If you add the slope of an 80hz electronic crossover to an 80hz acoustic rolloff  on a speaker, you get a much higher crossover slope.  You always need extension below or above the frequency to achieve proper slopes.  It isn't the electronic or natural roll off, it's the combo, the true acoustic roll off in room that you are after so things are not black and white.  Speaker design wouldn't be an art meshed with science if it were that easy.  Just provide a solid speaker and subwoofer and electronically manipulate them.  Another thing that isn't being looked at is many speaker's distortion goes up after you get out of their passband.

 

Too bad no ideal... that's too easy

[pzannucci]

11 hours ago, adam2434 said:

wvu80, sounds like you like the Fusion 10 Pure.  Did you build them?

 

I've been on the DIY site several times to look at their designs.  I have not found a sealed smaller 2-way on the site though.  I kind of wonder why they port speakers that were designed to be used with subs.  I've even read comments from Jeff Bagby where he indicates that sealed speakers are easier to integrate with subs.

 

 

The likely reason for Jeff Bagby's comments about integration is due to many designers trying to boost low end with ports.  That becomes counter with the smooth roll off typical sealed cabinets.   The theoretical 12db rolloff of sealed speakers is easier to work with and matches more to the electronics than the steeper roll off of a bass reflex cabinet (24db).  This is not counting the bump many put in the low end output of bass reflex to pretend they have extended bass.

[adam2434]

2 hours ago, pzannucci said:

The likely reason for Jeff Bagby's comments about integration is due to many designers trying to boost low end with ports.  That becomes counter with the smooth roll off typical sealed cabinets.   The theoretical 12db rolloff of sealed speakers is easier to work with and matches more to the electronics than the steeper roll off of a bass reflex cabinet (24db).  This is not counting the bump many put in the low end output of bass reflex to pretend they have extended bass.

 

Yes, and I also understand that ported speakers can also cause phase issues at the crossover frequency.

 

The filters portion of this article and the examples get into this subject.

http://www.rythmikaudio.com/phase1.html

 

I agree that the best way to deal with sub blending would be to use DSP to adjust filter slopes, phase, and frequency response.

 

However, if you don't have those DSP capabilities, choosing a sealed speaker with f3 at the crossover point is at least a way to get a 4th order slope on both sides of the crossover frequency, given that AVRs and processors typically apply a 2nd order electronic high pass filter.  Of course, you will still have the room effects in any scenario.

 

And yes, this is not a black or white thing, but "Is there a potentially better starting point?" is the question.

 

BTW, my interest in this subject came after playing with different sealed and ported bookshelf speakers in a secondary 2.1 system using an AVR with typical bass management.  After testing 2 ported and 2 sealed models, the 2 sealed models blend more seamlessly and sound more like a coherent "system".  With the ported speakers, I always felt like there was a discontinuity and the blend was less "believable".  This led me to the question of "Why am I hearing this difference?".

 

[pzannucci]

So your AVR is the DSP.  I'm not sure why you would want a speaker that rolled off at 80hz or are you now looking from a different direction.  

Again, if you get out of the passband, typically distortion goes up unless you filter that frequency range out with a dsp/electrically implemented crossover.

 

Maybe you are talking DSP for frequency shaping.  Well you can use the DSP on the small speakers to create a target roll off.

 

[adam2434]

I've been talking about 80 Hz crossover because that is pretty typical for bookshelf speakers.  The point I have been trying to make would apply to other crossover frequencies too.

 

With a book shelf speaker, much lower than an 80 Hz crossover and you aren't relieving the speaker and amplifier of much bass burden.  With a crossover above 80 Hz, you can start to have localization from the sub.

 

Let me again run through some basic assumptions and see where I may be off.

 

1) With speakers set to small, AVR and processors generally apply a 12 dB/octave high pass filter and a 24 dB/octave low pass filter at the chosen crossover point (I know my Outlaw processor does, for example).

 

2) These AVR and processor slopes are a legacy of the THX standard, which assumed a sealed speaker that started its acoustic 12 dB/octave roll off at the crossover frequency.  The goal was to achieve a perfect, symmetrical 24 dB/octave 4th order Linkwitz/Riley crossover free from phase shift at the crossover point.  THX speakers from companies like M&K were designed with this in mind, for example a sealed design that starts to roll off at 80 Hz to enable a 24 dB/octave slope when combined with the 12 dB/octave slope applied by the AVR or processor.

 

Here's a good article on this:

http://hometheaterhifi.com/volume_12_2/feature-article-slope-troubles-6-2005.html

 

So, let's stop here with a couple questions.

 

1) Does one agree that a symmetrical 24 dB/octave 4th order Linkwitz/Riley crossover free from phase shift is ideal for sub blending?  

 

If the answer is no, then let's discuss why.

 

2) Does one have the ability to implement a 24 dB/octave electronic high pass filter with their AVR, processor, or other DSP program?

 

If the answer is no, then how does one achieve a 24 dB/octave 4th order Linkwitz/Riley crossover free from phase shift?

 

The answer is a sealed speaker that starts to roll off at the chosen crossover frequency.

 

And back to my original question, why aren't more companies offering sealed speakers that are more optimized for sub blending with typical 12 dB/octave high pass filters in AVRs and processors, and trading bass extension for potentially higher sensitivity.  The trading bass extension for sensitivity thing is not an area where I can expound much, because it is pretty complicated math, involves driver parameters, and may be minimized because sealed speakers are less sensitive to begin with.

 

 

[Schu]

On 10/26/2017 at 7:11 AM, John Albright said:

It took me a couple of days to decide how to respond to your post.  First, there is nothing special about an 80 Hz crossover point.  I would want my mains to go as low as possible, at least 40 Hz, low E on a double bass or bass guitar, if possible.  Then, bass instruments will not change timbre from moving from sub to mains.  Second, the crossover point should be controlled by the Pre/pro and set according to the actual performance of the sub and speakers.  Finally, if speakers are to be designed only to play to 80 Hz, they will have to be part of a sub/sat system designed together.  AKA Blose or Gallo (not nearly an good sounding as they pretend). 

This...

[derrickdj1]

Most of this is a mute point if you are not using some type of measurement system to see what autocalibration did or is doing.  Due to room interaction there can be reinforcement or cancellation of certain frequency.  THX certifies speakers for an 80 Hz XO but, many speakers can't meet the criteria and using 80 Hz may not be the best.  The key of getting a good blend of the mains and subs is to avoid an audio hole with small speakers.

[pzannucci]

o, let's stop here with a couple questions.

 

1) Does one agree that a symmetrical 24 dB/octave 4th order Linkwitz/Riley crossover free from phase shift is ideal for sub blending?  

 

If the answer is no, then let's discuss why.

 

2) Does one have the ability to implement a 24 dB/octave electronic high pass filter with their AVR, processor, or other DSP program?

 

If the answer is no, then how does one achieve a 24 dB/octave 4th order Linkwitz/Riley crossover free from phase shift?

==================================================================================

 

 

Answer to #1 is it depends.  First of all when you talk Linkwitz/Riley are you talking electrical or acoustic?  If so, still depends

 

Answer to #2 is WHY?  The acoustic roll off is what you are really after.  Why continue to talk about electrical roll off?  

 

Phase shift will depend on the design, location of the drivers, and proximity to each other.  

 

Trying to achieve something that really doesn't exist unless you work on all parameters, electrical and the several above doesn't make sense.

 

 

[adam2434]

In the case of a sealed speaker with a selected crossover point where the speaker starts to roll off, the result would be a summed 24 dB high pass slope, when using bass management in an AVR or processor, so this would be a combination of acoustic and electric for the highpass (12 dB from the speaker and 12 dB from the AVR or processor).  The low pass would be an electronic 24 dB slope provided by the AVR or processor.   

 

From what I understand, ideally you would want a symmetrical slope on both sides of the sub/main crossover, and the above is a way to achieve that.  The article I linked above gets into this, if you are interested.

 

If AVRs, processors, or outboard DSP allowed one to apply a 24 dB high pass (and some do), then one would have more flexibility to achieve the symmetrical 24 db high and low pass filter for the sub/main crossover.

 

The erratic room-dependence of low frequencies may totally swamp any benefits of a symmetrical 24 dB slope anyway...bigger fish to fry type of thing when it come to bass frequencies.

 

Anyway, I feel I've beaten this dead horse enough.  I feel like I've been a bit misunderstood, but that's ok, no worries.  

 

 

 

 

 

 

[derrickdj1]

2 hours ago, adam2434 said:

In the case of a sealed speaker with a selected crossover point where the speaker starts to roll off, the result would be a summed 24 dB high pass slope, when using bass management in an AVR or processor, so this would be a combination of acoustic and electric for the highpass (12 dB from the speaker and 12 dB from the AVR or processor).  The low pass would be an electronic 24 dB slope provided by the AVR or processor.   

 

From what I understand, ideally you would want a symmetrical slope on both sides of the sub/main crossover, and the above is a way to achieve that.  The article I linked above gets into this, if you are interested.

 

If AVRs, processors, or outboard DSP allowed one to apply a 24 dB high pass (and some do), then one would have more flexibility to achieve the symmetrical 24 db high and low pass filter for the sub/main crossover.

 

The erratic room-dependence of low frequencies may totally swamp any benefits of a symmetrical 24 dB slope anyway...bigger fish to fry type of thing when it come to bass frequencies.

 

Anyway, I feel I've beaten this dead horse enough.  I feel like I've been a bit misunderstood, but that's ok, no worries.  

 

 

 

 

 

 

Adam, we are not rejecting your premise. There are benefits to a sealed system and the natural roll-off of 12 db.  The reality of things is that all this is highly dependent on the processor, room, room TX and phase correction of the system.  I have ported mains that don't follow that scenario but, the processor, setup and tweaking came correct any problems.  Note the graph below of what is going on at 80 Hz.  I have a very good blend of the subs with the mains.