Use the best speaker for the job at hand - size versus bass

[heeman]

Now, there are still situation where this advice doesn't make sense. For instance, a solid and simple stereo setup with a really good pair of two-way bookshelf speakers can sound amazing for stereo listening, even at high SPLs. This can be due to the simplicity of the setup, the lack of issues with properly configuring a more complex setup, the use of a poorly performing sub (for whatever reason) and dumb mistakes like cranking the hell out of the subwoofer because you want to always hear it no matter what. Another good example is in a room where most of the bass acoustics issues have been remedied and the SPLs being demanded are not all that terribly high.

For instance, in Heeman's theater the bass issues common in pretty much every HT out there have been addressed with extremely massive amounts of bass trapping in the corners, a drop ceiling for more bass trapping, and non-parallel walls. His room is very good for great bass from a pair of main speakers regardless of their placement, so getting full on stereo sub-bass from the mains is possible. However, his little Dynaudio C1 speakers with their amazing 6" woofers simply could not generate the output he wanted and still do well overall. So, set them to "small" and put a sub on the bass. Even better, because his room acoustics are so amazing, build some bass bins to take over from 225Hz downward and really free up those little 6" woofers to kick ass in the critical midrange where they shine the most. Now his system is killer. AND... even with stunningly state of the art bass bins which can operate to well below 30hz without any stress, we discovered that crossing them over at 40Hz to his massive subwoofers which can blow the doors off at 20hz. The result is a system where stereo music can be heard without any limitation on frequency response, dynamics, or balance. Can it be improved? Sure, but it is so much better than most HTs because it is designed to make the most of each speaker.

Is it worth to mention that the ports are also plugged on my C1’s?

I have also mentioned this in the past however it is worth mentioning again.

My home theater would not be what it is today without your recommendations/design as well as support from Chris with Dynaudio and JVC.

What a great thread and a great group of friends here!! Thanks to Danny for starting this and PaulyT for sustaining this forum!!

 

[TitaniumTroy]

Flint, could you elaborate on why you like PSA over SVS, I was just curious? Thanks

 

[Flint]

Flint, could you elaborate on why you like PSA over SVS, I was just curious? Thanks

There are many reasons, but none are so powerful that I refuse to buy SVS. Really, it is only a preference.

Based on what we've learned about founders of SVS, I determined that the smartest mind in terms of design and audio reality was Tom who left to form PSA. Since Tom left, SVS has changed their image and vastly broadened their product lines to include stuff I really am not a fan of. At one time, I could tell anyone to buy virtually anything they could afford from SVS and I knew it was a good product and deal. Today I am not confident my novice friends would know the difference between the good products and the sell-out stuff I'd never recommend. However, the good stuff at SVS is still very good and a great value.

With PSA the focus is really on performance and nothing else and basically you get what you pay for. As such, I can send people to the PSA website and be certain just about anything they buy will be a great product and a good value.

That said, the only commercial subwoofer I have purchased in well over a decade and which is still in use every day in my home is an SVS sub.

 

[TitaniumTroy]

Flint, can you go over again please, the value of having wider bass cabinets like Rammis and yours VS today's narrow tower speaker cabinet? What frequencies does the cancellation effect happen at, when they wrap around the narrow tower speakers? Also how does this effect the sound we hear at the listening position?

 

[Flint]

Flint, can you go over again please, the value of having wider bass cabinets like Rammis and yours VS today's narrow tower speaker cabinet? What frequencies does the cancellation effect happen at, when they wrap around the narrow tower speakers? Also how does this effect the sound we hear at the listening position?

The width and height of the baffle determines which frequencies are projected forward in a hemispherical dispersion pattern and which frequencies will be projected in a fully spherical patter. The math is simple, the speed of sound divided by the width (or height if the speaker is wider than high) to determine the exact frequency where the baffle is 100% forward radiating. For example, if a baffle is 12 inches wide and any amount taller, the sound from the speakers above 1,128Hz will be 100% forward radiating. If the baffle is 18 inches wide, the sound above 752Hz will be 100% forward radiating.

The effect will slowly roll off to 1/4 wavelength, or 1/4 the frequency of the fully forward radiating. So, for the 12" wide baffle the sound will have an appreciable forward radiation pattern down to 282Hz. For the 18" wide baffle it'll radiate forward to about 188Hz. This is why many popular narrow tower speakers are 2.5 way speakers where the lower woofer has a crossover tuned to the width of the speaker, or for the 12" wide baffle it would be 282Hz.

This isn't an issue of the speaker is pushed up against the wall behind it because the wall would reflect the sound forward. But if the speaker is put out in the room, which almost always improves the imaging and soundstage, the forward reinforcement of the baffle width will improve the bass and lower the baffle step drop off, or reduce the baffle step null.

So, with sexy narrow speakers the designers have to engineer the crossovers and drivers to compensate for the reinforcement of the baffle. Straight up, that's a 6dB drop off in output below the 1/4 wave frequency. So, for a 12" speaker placed out in the room away from the front wall, the output below 282Hz will be 6dB SPL lower than the output above 282Hz, and there will be a slope that starts at about the half-wave frequency, or 762Hz, that rolls off down to the cutoff at 282Hz.

Man, I hope that made any since at all.

With my new super high end speakers, I made the baffles 19.5 inches wide, making the start of the bass roll off to start around 350Hz, which happens to be the frequency I tuned the crossover to the bass speakers from the midrange speakers. That way all I need to do is turn up the woofers by about 6dB SPL relative to the midrange speakers to compensate for that difference.

Crazy stuff, eh?

 

[TitaniumTroy]

Hey thanks, that was pretty cool. To compensate for my terrible math skills, where would my speakers at 22" wide come in at? Also, how about the Altec A7 VOTT which comes in at a really wide 30"?

 

[Flint]

Hey thanks, that was pretty cool. To compensate for my terrible math skills, where would my speakers at 22" wide come in at? Also, how about the Altec A7 VOTT which comes in at a really wide 30"?

So, doing the math...

22" is the wavelength of 615Hz. So, the forward radiation will slowly start rolling off at about 307Hz and be 6dB down at 154Hz.

30" is the wavelength of 451Hz. So, the forward radiation will slowly start rolling off at about 225Hz and be 6dB down at 113Hz.

Back in the day, Altec sold "wings" for the A7 which tripled the width of the enclosure for when they were installed outdoors at concert events. With those installed, the bass was pretty solid down to 37.5Hz. Widening the baffle space is critical for outdoor speakers. In a house, however, the room's walls, floor, and ceiling also reinforce the bass. So, even with the roll off, some rooms will start reinforcing the bass. For instance, my speakers' acoustic centers are about 36 inches from the side walls, so below 94Hz the side walls increase the output in the room by 6dB. The woofers' acoustic center is also about 14 inches from the floor, so from 242Hz down the floor in reinforcing the bass by 6dB.

This is a messy thing, getting the bass right in a room.

It is also why I love active crossovers. I can change the output characteristics to fit the room and baffles.

 

[Flint]

By the way, the math is really simple...

Speed of sound = 1128 ft/sec

So, to determine the frequency of a distance, divide the speed of sound by the distance in feet. So the frequency at 2 feet (or 24 inches) is:

1,128 / 2 = 564Hz​

The critical values off that frequency are:

1/2 wavelength (cancellation null when in a reflection), or 282Hz (1/2 of 564Hz)
1/4 wavelength (reinforcement limit for walls or the width of a baffle), or 141Hz (1/4 of 564Hz)​

 

[TitaniumTroy]

So you can compensate for the baffle step in the frequency response domain, by increasing the output of the woofers. But what happens with the soundstage? Is that also compensated for or does the bass become just become omnidirectional in a tower, vs the forward firing bass of a speaker with a wider baffle?

Hope I am making some of sense, not just babbling like some audiophool.

 

[Flint]

So you can compensate for the baffle step in the frequency response domain, by increasing the output of the woofers. But what happens with the soundstage? Is that also compensated for or does the bass become just become omnidirectional in a tower, vs the forward firing bass of a speaker with a wider baffle?

Hope I am making some of sense, not just babbling like some audiophool.

Are we talking home speakers, large hall speakers, or outdoor speakers?

In homes, the distance between a speaker and at least three major reinforcing reflective surface planes, such as the floor, ceiling, and front wall, is usually no more than 8 feet - often less than 4 feet away. As such, the frequencies below about 80Hz and up to 160Hz will be mostly omnidirectional regardless. As such the baffle will have little impact on any frequency range we would refer to as "bass". I generally consider bass to be frequencies as high as 250Hz, sometimes a little higher depending on the instrument or sound. So, a baffle large enough to impact the "bass" as I define it in a home would have to be at least 13.5 inches wide/tall. For real reinforcement into the true bass range, like as low as 100Hz, it would need to be more than 34 inches wide/tall.

However, outdoors if the woofer cabinets are on the ground, you have one reinforcing reflective surface plane being the ground. Sound will radiate omnidirectionally below the frequency which the baffle size cannot direct forward. Above that frequency the sound will radiate in a forward and upward direction from the baffle and nowhere else.

 

[TitaniumTroy]

Flint, how are speakers like mine and the Altec A7's able to do great bass and still sound very good in the midrange? Without a dedicated midrange and without our big 15" woofers getting in the way of the midrange sound? FYI, my woofers plays up to 700, before crossing over to the horn section.

 

[Flint]

Flint, how are speakers like mine and the Altec A7's able to do great bass and still sound very good in the midrange? Without a dedicated midrange and without our big 15" woofers getting in the way of the midrange sound? FYI, my woofers plays up to 700, before crossing over to the horn section.

With the Altec A7 Voice of the Theater speakers, the woofers are not operating in the midrange. It is the horn drivers which do most of what we call "midrange." Horns are stunningly efficient and incredibly dynamic with a very controlled dispersion pattern which reduces many of the early reflections serious rooms have acoustic panels to absorb. On top of that, the upper range of the woofer has a wave guide which also improves the forward directivity as a horn would (but without the acoustic pressure compression).

The JBL speakers like yours have extensive use of very advanced crossover technologies and amazing horn midrange drivers to balance the output. Yours are tailored so the horizontal dispersion pattern of the woofer and the midrange horn are matched at the crossover frequency so that between EQ and room power response, the overall blending of the two speakers is so spot on that you get amazing performance.

That said, I don't think either speaker offers the absolute best midrange in the industry for the money. Horns have some inherent issues which cannot be fixed with crossovers, but their benefits often mask their issues. Like trading one issue for another to get a different set of benefits.

I struggle with what to call the frequency range between 300Hz and 700Hz - is that midrange, bass, upper bass, lower midrange, or what? It is often a range which is ignored because we don't rely on that range for identifying or locating sounds. We also don't get impressed when that range is unnaturally louder than the rest of the audible spectrum like we do when the low bass or high treble is boosted. It is just, well, "there" and we rarely notice it except when it is lacking or too strong. After the true midrange, or what I consider to be about 800Hz to 5,000Hz, getting that lower midrange right often makes all the difference in the realism of a speaker's performance. And since we don't immediately comprehend the quality of a speaker in that range, we often forget about it and not realize it when it is done right. We just know a good speaker when we hear it, and that range is critical to making a speaker great.

 

[TitaniumTroy]

Cool, thanks for that explanation. I knew there had to be some kind of trade off, in a big two way design.

 

[Flint]

Something to consider is that it is very difficult for a single transducer to handle the entire frequency spectrum ideally. So, we use woofers and tweeters, a woofer to handle the bass range up to the midrange then a tweeter to handle the treble down to the midrange, and a crossover filter is put in place to try to blend the two together at the crossover point. Building a two-way speaker solves the problem of having one driver attempt to handle everything, which is impossible to do well with today's technology, but it introduces new problems in blending the two together with a crossover, the dispersion difference between the two drivers, and the distortion differences in phase, frequency, ringing, and harmonic distortion. A metal dome diaphragm has a completely different tonal characteristic and acoustic propagation than a paper pulp diaphragm. As such, getting a perfect match so the listener cannot tell any difference throughout the frequency range between the two drivers is challenging, but when done well is typically costly and often less than gorgeous to an interior designer.

But we if take this further, two-way may not be enough - after all, producing a solid 20Hz with current tech requites very different drivers, placements, amps, and enclosures than producing a clean and stereophonically ideal 200Hz. The same can be said for getting a very clear, clean, and natural sounding 15kHz from a speaker also producing 1.5kHz. This makes a three-way speaker a potentially better than a two-way, but then you've introduced more crossover issues which creates troubles with phase/delay, ringing, distortion, power/heat variations, and so on. So, getting it right is hard, but when it is done well you could get much better quality across more of the audible spectrum.

Some companies choose to make the midrange as perfect as possible and as the output gets higher and lower in frequency they are willing to sacrifice perfection to reduce the number of drivers. A good example are the plethora of good single-driver full-range solutions out there which often have very impressive midrange in the 500Hz to 5,000Hz range, which is by far the most important range in terms of how our brains process acoustic data and interpret it as musical information. However, a "full-range" speaker which can do well in the midrange has to choose to either be decent in the bass or decent in the treble range. So, a smaller driver is typically better sounding above 5,000Hz with decent dispersion, flatter frequency response, and higher clarity at the upper frequencies , yet it will suffer below 500Hz by having limited power capacity (output), lack any impact, and exhibit high THD. The alternative, a larger fill-range driver may do better below 500Hz, but it will then suffer above 5,000Hz.

So, to get great sound you have to find a balance between all these benefits and issues, all of which are equally important to the performance you hear:

• Divergence from assumptions on amplifier(s) to be used
  
• The drivers
• Crossovers
• How sound propagates from the speaker system
• How the room reflects, reinforces, and cuts the propagated sound
• Where the listener positions himself in relation to the speakers and the room's reflective surfaces

A speaker manufacturer can only control the first three aspects of a speaker system. Unless the speakers are self-amplified, the first issue with amps much assume the amp has an output impedance of essentially zero, which tube amps do not. So, if a speaker is designed for tube amps the crossover might be designed very differently. The drivers, crossover, and propagation pattern from the speaker system are aspects of design and performance completely in the control of the speaker designer. The way the room impacts the sound and how the user places everything is out of the control of the speaker designer, so assumptions have to be made and advice and guidelines have to be provided to explain what assumptions are made.

 

[Flint]

So, to expound on my philosophy on getting the best from a speaker design, I want to evenly divide up the audible spectrum evenly between however many speakers I happen to have in my multiway system.

For example, with a two way design I like to assume the woofer will operate down to about 50Hz without significant limits (as in a good 6.5" woofer or any 8" woofer). We all expect tweeters to operate to 20,000Hz, but anything above 17,000Hz is good enough, in my opinion. So, with a range of 50Hz to 15,000Hz you have approximately 8.5 octaves of range. So an ideal splitting point would be at about 4.25 octaves, or about 1,250Hz - which requires a killer tweeter, such as many of the cool new 32mm to 36mm dome tweeters which have been recently been showing up on the high end market. But even the best 1" dome tweeters would be poor at 1,250Hz.

If you assume a subwoofer will be used (which is extremely common), then the effective high quality bass output range should reach down to 100Hz. With that, the effective range you can use a minimum of a good 6" mid-woofer (though a 5" woofer with limited peak SPL), for the system becomes more like 7.5 octave range. Then the ideal crossover point would be more like 1,600Hz. If you insist on a high quality output to a higher frequency, such as a full 20,000Hz, then the range is more like 8 octaves and you need a smaller tweeter for the higher frequencies, so a 1,800Hz crossover is impossible. But you have a range of 8 octaves from 100Hz to just over 20,000Hz. 2,000Hz, which many good 1.1inch tweeters could handle with a 3rd or 4th order crossover.

Both of those considerations are fraught with trade-offs and issues which put many of the core issues of what we hear in our most critical audio range at risk. Ideally, the midrange should be free from crossovers and attempts to match the different timber of completely different drivers. So, there are benefits to having a dedicated midrange which can operate throughout the critical midrange of 500Hz to 5,000Hz. There are great dome tweeters out there which can do this, as well as some good smaller midrange drivers that can do it. With horns there are a plethora of options because PA systems designers have known this critical aspect for decades.

So, assuming you have a larger woofer that can operate with great performance as low as 30Hz and a tweeter which can exceed 20,000Hz without issues, that gives you a bandwidth of about 10 octave, so each driver should get about a third of that range in an ideal setup. So, a good woofer operating to about 360Hz and a tweeter operating down to about 3,000Hz and a tweeter above that. That requires drivers which have similar performance characteristics at the crossover frequencies and which can create enough SPL for the listener. But more crossover points means more issues from crossovers which have to be accounted for.

When designing a crossover, finding drivers which can do the job in their range isn't difficult. But getting the crossover to perform in a way which makes it impossible to tell when one drivers is fading out and another is fading in can be very difficult. So, while more drivers can help with getting better wide-range performance, they add serious issues from the crossovers being used.

 

[TitaniumTroy]

Re: crossovers being a pain, how much of the problem do active crossovers and dedicated amps solve. Like 50%, or whatever?

 

[Flint]

Re: crossovers being a pain, how much of the problem do active crossovers and dedicated amps solve. Like 50%, or whatever?

I created a new thread in the Audio / Speakers section.

 

[TitaniumTroy]

Just curious how would you rate the 15" woofers in my JBL 4367 and their cabinet?
DIMENSIONS (H X W X D) 37-1/16" x 22-1/16" x 16-3/4" (941mm x 560mm x 425mm)
WEIGHT 135 lb (61.2 kg) Re: the weight I would think it should be pretty well braced, heavy as it is.

Also what does Dual Differential Drive mean, and what does it do for the bass?

 

[Flint]

Rate in what way? They are as close to ideal as you can get in terms of their goals, which are low distortion, decent bass extension, high SPL capability, and smooth power response. Those are the trademark characteristics for JBL true professional grade studio monitors, of which these are a consumer version.

The dual differential drive uses two fixed magnet arrays facing opposite one another and two voice coils facing opposite one another which reduces the distortions caused when the impedance characteristics of the voice coil moving inward behaves completely differently than when it is moving outward. By making two motor assemblies, both connected to the cone through a single voice coil former, the outward characteristics of one voice coil are cancelled out by the inward characteristics of the other motor. It is a complicated and over engineered solution to a very real problem which is relatively easy to manufacture, but it costs a goodly amount of money. If you notice, JBL isn't marketing their differential drive transducers as raw components like they do their older model drivers.

Here's the inductance of the voice coil from a very high end 12" pro woofer from an Italian manufacturer based on the position of the voice coil in the magnetic gap:

Notice that when the cone is moved inwards the inductance increases considerably. Meanwhile, when the cone is moved outwards the inductance deceases considerably. Also note that the shape of how the inductance changes is very different for inward motion versus outward motion. This leads to complex distortions which cannot be corrected for by any external process or filter. The JBL dual differential drive technology greatly reduces this inductance issue, as well as some of the other issues which are caused when the voice coil moves inwards versus outward.

 

[TitaniumTroy]

When rate, I meant as I am using them as stereo speakers, with High Fidelity aspersions. Also vs the high end speakers of the day, Magico, B&W, Wilson, YG Acoustics.