B&W 805S - Where is the bass?

[Vladimir]

lol.... Just trust me.

Think about that theory for a second. Before any bass frequencies have exited the port the sound/air would have bounced back and forth inside the speaker box/enclosure how many times?

I mean just because the speakers are round does not mean the sound waves are round.

You know how sound travels, I mean why do you think bungs are supplied with ported speakers?

Answer A: Provide people with a crude tuning method that reduces the travel of the cone by increasing the cabinet compression, turning it into acoustic suspension system, resulting in less bass, but also less distortion. Similar but not exactly the same effect can be produced with tone controls.

Answer B: Manufacturer manipulation. Produce an appealing, loudish speaker for the showroom, supply foam bangs in the box to prevent the customer from returning the speakers once it hears the rubbish produced in his room. If persistent sell him different cables, amp, cartridge, room treatment.

 

[davedotco]

Thompson,

Your lack of even the most basic comprehension of how sound is generated and propogated makes any attempt at an explanation extremely difficult.

For example, directivity is primarily a function of radiating area against frequency, small horns like trumpets or cupped hands have no effect at low frequencies, bass frequencies do not 'bounce around' inside enclosures, it is simply a change in air pressure, ports do not 'pump out' bass they are a way of loading the bass driver so that it behaves in a different manner.

I recommend some basic school texts on sound propagation, reflection, diffraction etc, followed by a book on basic acoustics, you don't need the detail at this stage, just some fundamental principles will help.

 

[davedotco]

lol.... Just trust me.

Think about that theory for a second. Before any bass frequencies have exited the port the sound/air would have bounced back and forth inside the speaker box/enclosure how many times?

I mean just because the speakers are round does not mean the sound waves are round.

You know how sound travels, I mean why do you think bungs are supplied with ported speakers?

Answer A: Provide people with a crude tuning method that reduces the travel of the cone by increasing the cabinet compression, turning it into acoustic suspension system, resulting in less bass, but also less distortion. Similar but not exactly the same effect can be produced with tone controls.

Answer B: Manufacturer manipulation. Produce an appealing, loudish speaker for the showroom, supply foam bangs in the box to prevent the customer from returning the speakers once it hears the rubbish produced in his room. If persistent sell him different cables, amp, cartridge, room treatment.

Cheeky, and not a million miles from the truth.

In reality a ported design that is used to give only modest augmentation in the bass can have excellent transient response and minimal time smear whilst given performance a gentle overall boost.

The modern trend towards bassier speakers tends to designers using the port to generate as much bass as possible resulting in various issues including a less good transient response and notable time smear (bass overhang) mentioned earlier.

Using bungs will alter the loading on the bass driver, the 'Q' will now be too high and the performance compromised still further, most modern OEM drivers are optimised for port loading, they have the 'wrong' parameters for sealed boxes, one reason why manufacturers who rely on OEM drivers rarely make anything but ported enclosures.

 

[Thompsonuxb]

Provide what?

The difference between a ported design and a sealed design of the same volume, power, driver size and driver travel per watt.

The difference the ported design appears to have 'more' bass. Why?

The basics - the sealed design uses the driver and the box.

The ported design pushes frequencies with the air existing the port from within the enclosure added to the driver and the resonance of the box..

Sound travels through air that's it's medium that's why no one can hear you screaming in space.....

The bung controls the air flow from the box and with it the low frequencies with it.

Speakers are designed to spec i.e 1watt to 2mm travel, adjustments to a port will not change that. Outside of that spec is distortion.

lol.... Just trust me.

Think about that theory for a second. Before any bass frequencies have exited the port the sound/air would have bounced back and forth inside the speaker box/enclosure how many times?

I mean just because the speakers are round does not mean the sound waves are round.

You know how sound travels, I mean why do you think bungs are supplied with ported speakers?

Answer A: Provide people with a crude tuning method that reduces the travel of the cone by increasing the cabinet compression, turning it into acoustic suspension system, resulting in less bass, but also less distortion. Similar but not exactly the same effect can be produced with tone controls.

Answer B: Manufacturer manipulation. Produce an appealing, loudish speaker for the showroom, supply foam bangs in the box to prevent the customer from returning the speakers once it hears the rubbish produced in his room. If persistent sell him different cables, amp, cartridge, room treatment.

 

[Thompsonuxb]

Dave, all that is smoke and you know it, just read your the last update...... I''ll be back!

Thompson,

Your lack of even the most basic comprehension of how sound is generated and propogated makes any attempt at an explanation extremely difficult.

For example, directivity is primarily a function of radiating area against frequency, small horns like trumpets or cupped hands have no effect at low frequencies, bass frequencies do not 'bounce around' inside enclosures, it is simply a change in air pressure, ports do not 'pump out' bass they are a way of loading the bass driver so that it behaves in a different manner.

I recommend some basic school texts on sound propagation, reflection, diffraction etc, followed by a book on basic acoustics, you don't need the detail at this stage, just some fundamental principles will help.

 

[lindsayt]

Here's a plot of the bass port, mid-bass driver and tweeter of a similar sized 2 way speaker (it's the B&W Matrix 805). This plot is typical of small 2 way ported speakers in that the reflex port takes over from the mid-bass unit below about 65 hz. Some tiny ported speakers have the port take over at a higher frequency than that.

As for directionality, anyone can do a simple test by running some test tones at various frequencies through one speaker then the other to give you an idea where the borderline is between directional and non-directional bass. If you can tell which speaker the tone is coming from, there's some directionality at that frequency in your room, with your system and your ears.

It's quite possible that you will find that 60 hz is at least partly directional. In which case this would indicate that port location has some importance for speakers like the 805 range.

 

[ID.]

Interesting discussion. Unfortunately much more interesting than solving the OP's problem which is probably impossible without getting hands on with the speakers ourselves. I'd personally decided that he has the jumper plates/cables remnoved and has the speaker cable attached only to the tweeters *unknw*

 

[Thompsonuxb]

ID... It was really quiet, honestly it was still, nothing was going on.

Already suggested the op should get these speakers checked.

Interesting discussion. Unfortunately much more interesting than solving the OP's problem which is probably impossible without getting hands on with the speakers ourselves. I'd personally decided that he has the jumper plates/cables remnoved and has the speaker cable attached only to the tweeters  *unknw*

 

[Thompsonuxb]

Thanks Lindsayt - me, I know they'd run their hands through an open flame rather than admit they're wrong.....lol

I try not to get technical so all can read and enjoy but thanks for that post.

Here's a plot of the bass port, mid-bass driver and tweeter of a similar sized 2 way speaker (it's the B&W Matrix 805). This plot is typical of small 2 way ported speakers in that the reflex port takes over from the mid-bass unit below about 65 hz. Some tiny ported speakers have the port take over at a higher frequency than that.

As for directionality, anyone can do a simple test by running some test tones at various frequencies through one speaker then the other to give you an idea where the borderline is between directional and non-directional bass. If you can tell which speaker the tone is coming from, there's some directionality at that frequency in your room, with your system and your ears.

It's quite possible that you will find that 60 hz is at least partly directional. In which case this would indicate that port location has some importance for speakers like the 805 range.

 

[davedotco]

Here's a plot of the bass port, mid-bass driver and tweeter of a similar sized 2 way speaker (it's the B&W Matrix 805). This plot is typical of small 2 way ported speakers in that the reflex port takes over from the mid-bass unit below about 65 hz. Some tiny ported speakers have the port take over at a higher frequency than that.

As for directionality, anyone can do a simple test by running some test tones at various frequencies through one speaker then the other to give you an idea where the borderline is between directional and non-directional bass. If you can tell which speaker the tone is coming from, there's some directionality at that frequency in your room, with your system and your ears.

It's quite possible that you will find that 60 hz is at least partly directional. In which case this would indicate that port location has some importance for speakers like the 805 range.

Excellent plot, very instructive.

In this particular design the contribution of the port is quite substantial, the trick of the designer is to get enough from the port to be useful without compromising other factors, factors that usually result in bass boom. This is done by using drivers with slightly different resonant characteristics (Q) and varying the port.

In essence, at resonance tha critical mass of air in the port tube works to 'load' the bass driver, limiting excursion and lowering distortion. The lowering of output is offsett by the contribution of the port. This kind of allignment extends the bass response below the normal resonance of the driver giving greater bass extension followed by a steeper roll off one octave below that point.

In a well designed system this can be made to work very well, extending the bass response with minimal adverse effects, the problems tend to arise when the designer oversteps the mark and tries to maximise bass output.

Look at the plot and shift the trace for the port to the right, such that the peak is now around 90-100hz rather than the 40-50hz that it is in the plot. Add the plots, bass driver and port, together and you get the mid bass hump that is so commonplace in modern loudspeakers.

 

[lindsayt]

ID, if that was the case, with 2 ways like the 805s you know instantly as you'd have no midrange and well as no bass. You'd only have treble. That would sound really awful.

As has already been mentioned, it's difficult to know whether the OP has some technical fault with his speakers, or some installation fault, or if they're working properly and not delivering the bass that he desires.

It could be that he's listening at relatively modest volumes and at these volumes the 805s are similar to the KEF LS50's where the bass goes missing at lower volumes. Or it could be something else. It could even be a combination of factors.

 

[davedotco]

ID, if that was the case, with 2 ways like the 805s you know instantly as you'd have no midrange and well as no bass. You'd only have treble. That would sound really awful.

As has already been mentioned, it's difficult to know whether the OP has some technical fault with his speakers, or some installation fault, or if they're working properly and not delivering the bass that he desires.

It could be that he's listening at relatively modest volumes and at these volumes the 805s are similar to the KEF LS50's where the bass goes missing at lower volumes. Or it could be something else. It could even be a combination of factors.

Spot on.

However the OP was referencing to a pair of 686s, speakers that can get decidedly 'humpy' in my experience.

 

[chebby]

B&W Nautilus 805 individual plots of port, mid/bass driver and tweeter ..

... and their cumulative result ...

(The one I posted earlier.)

 

[lindsayt]

With designs like the Matrix 805s, it's depends what you mean by minimal adverse effects from the ports.

When it comes to the frequency response with input sine waves at 2.83 volts input (which is loud to very loud depending on speaker efficiency) you get a not too bad frequency response.

When it comes to transient response at the frequencies covered by the bass port, things aren't so good.

Also there may well be issues with the port not waking up until you get to more generous volumes. It'd be interesting to see frequency response plots for nominal 0.01 watts input.

 

[davedotco]

With designs like the Matrix 805s, it's depends what you mean by minimal adverse effects from the ports.

When it comes to the frequency response with input sine waves at 2.83 volts input (which is loud to very loud depending on speaker efficiency) you get a not too bad frequency response.

When it comes to transient response at the frequencies covered by the bass port, things aren't so good.

Also there may well be issues with the port not waking up until you get to more generous volumes. It'd be interesting to see frequency response plots for nominal 0.01 watts input.

Yes it is a trade off, no arguments there. Good drivers make a difference and as I said earlier keeping the allignment well clear of the extremes help too. With moden amplifiers I doubt that porting is really necessary but for budget designs in particular I guess it helps in the showroom, where the most impressive speaker with the most bass is the one that sells

The power issue is interesting too, it may help to explain why speakers such as the 800 series and the Harbeths (see elsewhere) need rather more power than their sensitivity would suggest to really come to life and control the bass.

 

[ID.]

ID, if that was the case, with 2 ways like the 805s you know instantly as you'd have no midrange and well as no bass. You'd only have treble. That would sound really awful.

As has already been mentioned, it's difficult to know whether the OP has some technical fault with his speakers, or some installation fault, or if they're working properly and not delivering the bass that he desires.

It could be that he's listening at relatively modest volumes and at these volumes the 805s are similar to the KEF LS50's where the bass goes missing at lower volumes. Or it could be something else. It could even be a combination of factors.

Of course, how stupid of me. Anyway, I wasn't being facetious when I said the discussion in this thread has been interesting. Certainly enlightening.

 

[Thompsonuxb]

Wait - have some accepted frequencies from the port adds its own flavour to the sound of a ported design and it's not just 'air' compressed or other wise.

Wow - not even an apology or acknowledgement....

And there I was ready with a 'the speed of sound in a 30cm enclosure' thing and why drivers even bass drivers face forward in most cases analogy....

Some people, I swear.

 

[chebby]

And there I was ready with a 'the speed of sound in a 30cm enclosure' thing and why drivers even bass drivers face forward in most cases analogy....

What most people call 'bass drivers' usually cover an awful lot of the mid-range frequencies too. It is important that they face forward.

Bass (only) drivers tend to work wherever you stick 'em within reason. (Side facing on my speakers, downward facing in some others. I have even seen rear facing bass drivers.)

 

[Vladimir]

Wait - have some accepted frequencies from the port adds its own flavour to the sound of a ported design and it's not just 'air' compressed or other wise.

Wow - not even an apology or acknowledgement....

And there I was ready with a 'the speed of sound in a 30cm enclosure' thing and why drivers even bass drivers face forward in most cases analogy....

Some people, I swear.

Now the big question. If back ported designs are rubbish, why manufacturers insist on having them?

 

[Thompsonuxb]

Lol.....

Rear ported designs are not rubbish. The idea is a 'less in yah face' presentation.

Side firing woofers facing each other for example presents bass that's 'round'

Using the rear wall to defuse bass frequency will give a warmer more general presentation.

The whole point of ports is so smaller drivers, boxes can give bass the same representation of larger drivers.

Altot of R&D has gone into these designs.

It works.

Wait - have some accepted frequencies from the port adds its own flavour to the sound of a ported design and it's not just 'air' compressed or other wise.

Wow - not even an apology or acknowledgement....

And there I was ready with a 'the speed of sound in a 30cm enclosure' thing and why drivers even bass drivers face forward in most cases analogy....

Some people, I swear.

Now the big question. If back ported designs are rubbish, why manufacturers insist on having them? 

 

[Thompsonuxb]

Chebby, I was ready to go there too. Cover how all frequencies are utilised in modern designs.

Lol......

And there I was ready with a 'the speed of sound in a 30cm enclosure' thing and why drivers even bass drivers face forward in most cases analogy....

What most people call 'bass drivers' usually cover an awful lot of the mid-range frequencies too. It is important that they face forward.

Bass (only) drivers tend to work wherever you stick 'em within reason. (Side facing on my speakers, downward facing in some others. I have even seen rear facing bass drivers.)

 

 

[davedotco]

Wait - have some accepted frequencies from the port adds its own flavour to the sound of a ported design and it's not just 'air' compressed or other wise.

Wow - not even an apology or acknowledgement....

And there I was ready with a 'the speed of sound in a 30cm enclosure' thing and why drivers even bass drivers face forward in most cases analogy....

Some people, I swear.

No apologies necessary, your understanding remains way off the mark.

The port does not 'add flavour', predominately it is there to load the bass driver. Porting has an effect on the cone by limiting excursion and reducing distortion which is good, other effects less so, particularly in terms of transient response and 'time smear'.

The ouput from the port is quite modest and the range that it is in phase with the bass driver is just one octave. What really makes a difference is the way the port modifies the resonant frequency which extenda bass response at the expense of roll off.

 

[Thompsonuxb]

Again Dave your post is all smoke.

Seal the box and you'll hear the difference. Ports are used to tune the bass response in a box utilising the lower frequencies from your drivers rear.

Lindsayt is correct in his post.....the man even provided graphs.

Drivers are made to spec a few ounces of pressure will not change its performance.

You actually recognise this judging by your posts but appear to want to complicate things.....lol.....
resonate frequency, my eye.

Wait - have some accepted frequencies from the port adds its own flavour to the sound of a ported design and it's not just 'air' compressed or other wise.

Wow - not even an apology or acknowledgement....

And there I was ready with a 'the speed of sound in a 30cm enclosure' thing and why drivers even bass drivers face forward in most cases analogy....

Some people, I swear.

No apologies necessary, your understanding remains way off the mark.

The port does not 'add flavour', predominately it is there to load the bass driver. Porting has an effect on the cone by limiting excursion and reducing distortion which is good, other effects less so, particularly in terms of transient response and 'time smear'.

The ouput from the port is quite modest and the range that it is in phase with the bass driver is just one octave. What really makes a difference is the way the port modifies the resonant frequency which extenda bass response at the expense of roll off.

 

[Vladimir]

Bellow 80Hz-100Hz bass is no longer localized to our hearing due to the wideness of sound waves. They begin to arrive at our ears at almost the same time for our brain to triangulate their position. But you can't fool a microphone aimed at a duct port. Even at that advantage the mic will measure tiny influence of the bass port as a small artefact. The designer would prefer to have the cabinet loaded through a port without artefacts ideally.

Therefore, if bass artefacts come out of the bass ports under 80Hz, their location won't matter to our hearing. Only audible difference would be if they contribute to phase cancelations due to room reflections. Basically it all comes out like one sounding frequency, monobass, from somewhere.

In Macedonia an EE (Vladimir Filevski) invented a subwoofer amplifier that runs directly on AC and the sub only works with 60Hz or 50Hz since our hearing can't discern the difference.

 

[lindsayt]

Vladimir, try running some test tones through your system. Left channel only, right channel only, both channels together. At 100hz, 80 hz, 60 hz, 50 hz, 40 hz, 30 hz.

At what frequency can you no longer tell which speaker the sound is coming from?

Which frequencies, if any, sound identical? Do 50 and 60 hz sound different in your room with your system with your ears? Or do they sound the same?