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Joined 2002
Just remember that adding a sharp bend in a port tube causes a lot of resistance. I am actually adding a central HVAC system to my house and the same principle applies to ducting. Small narrow ports lead to higher air velocity in the port resulting in chuffing and port noise, exaggerated by the added resistance.
Not trying to rain on anyone's parade, just thought you should be aware. You'd be better off taking the port out the back there.
Not trying to rain on anyone's parade, just thought you should be aware. You'd be better off taking the port out the back there.
MBK said:
Indeed, often the travel is much more interesting than a destination itself.
That said, on saturday I heard good ol' Oleg Caetani at his best mastrefully conducting MSO performing Stravinsky's (impossible) Rites of Spring.
Hearing something like that live is a timely reminder that domestic audio setups have absolutely no hope. None whatsoever.
But then, that is why live concerts exist. 😀
ShinOBIWAN said:
I've started to get jokes about preferring speakers to women
😀
Of the two, Who's speaking up loudest ??????
😀
A slightly controvercial view of women vs speakers:
You can listen to speakers whenever you want and (more importantly) choose not to.
You can own as many pairs of speakers as you like without one pair of speakers getting jealous of any other pair.
You can leave two pairs of speakers in a room and come back after a few hours and not find the room rearranged to how the speakers want it to look.
Speakers don't have mothers.
...and if you don't like the look of any speakers currently in your price range you can make your own pair that are a lot more attractive and sound better than those you can afford to buy.
Being the politically correct kind of guy that I am, I don't condone this kind of thing of course 🙄 , just some light-hearted banter.
You can listen to speakers whenever you want and (more importantly) choose not to.
You can own as many pairs of speakers as you like without one pair of speakers getting jealous of any other pair.
You can leave two pairs of speakers in a room and come back after a few hours and not find the room rearranged to how the speakers want it to look.
Speakers don't have mothers.
...and if you don't like the look of any speakers currently in your price range you can make your own pair that are a lot more attractive and sound better than those you can afford to buy.
Being the politically correct kind of guy that I am, I don't condone this kind of thing of course 🙄 , just some light-hearted banter.
Hi all
Sorry for the late reply.
I've revised the design somewhat and the port is 50cm x 3.6cm or equivalent to a 6" ID tube. The bends will be angled to help with guiding the flow of air.
There will also be a largish horn style flare at both ends.
Resistance will hopefully be minimal with a port of this size. But I agree that its still inferior to a straight run of equivalent cross-sectional area.
And likewise, Hifi does things that a live performance can't.
There are sounds that can only be created in the digital domain and these don't exist in nature. Only a hifi system allows admission, so its swings and roundabouts.
Sorry for the late reply.
JoshK said:
I've revised the design somewhat and the port is 50cm x 3.6cm or equivalent to a 6" ID tube. The bends will be angled to help with guiding the flow of air.
There will also be a largish horn style flare at both ends.
Resistance will hopefully be minimal with a port of this size. But I agree that its still inferior to a straight run of equivalent cross-sectional area.
Bratislav said:
And likewise, Hifi does things that a live performance can't.
There are sounds that can only be created in the digital domain and these don't exist in nature. Only a hifi system allows admission, so its swings and roundabouts.
ShinOBIWAN said:
So why need for high quality speakers then ? I mean if you don't know how is something supposed to sound like in the nature, how can you be sure it has 'fidelity' when you hear it on the 'system' ?
I'll take the live orchestra over computer any day, thanks
😀
Bratislav said:
Who said anything about listening to just electronic music? I merely pointed out that hifi can produce sounds which are both natural, unatural and supernatural. And because of that it has its own appeal.
Also, good performing speakers benefit ANY type of music, I thought that would be massively obvious. Its not about just being able to draw parallels to 'quality' present in live performances or nature itself. Its also about integrity of sound as a whole and this is apparent with whatever music you listen to.
MBK said:
Hi MBK
That's true. I love to listen to whatever I've built but the most fun I have is designing, building and then tuning,
I bore very quickly unless something is particularly exceptional to my own tastes. Which is the biggest reason why I go through more parts than usual. Its also possible that I haven't got the best out of something before I drop it and move onto something that appears more promising. Its not a case of minimum effort in and maximum enjoyment out though, I do spend unhealthy amounts of time tweaking and swapping idea's around. If something's good I'll chase it as was the case with the ATC mid and the whole Perceive design which went through loads of changes before I was fully happy, so I do evolve things, I just need to see enough initial promise first - and that's not just measurements.
Depth. manageable dimensions, low distortion... each of these moves against the other.
Factor in the goals, the limitations and some designs get thrown out straight away. In my room I can only sensibly consider vented and sealed alignments, The B&C won't do sealed, blocking the port up shows that its performance is just plain bad like this. What am I left with? Vented. I've tried a few port tuning points now, I could change the volume and/or build the second...
There's also the fact that sometimes what you think you want isn't that at all 🙂
Maybe I'm still surprised how quickly you got tired of the vented B&C box without much trying to, say, changer the alignment to a more conventional one (that would give you mor output per Xmax at the expense of some distortion), or building the second box (even as a simple test mule without the bells and whistles of the first one, just same volume same alignment, to try stereo). I thought it was a very interesting design approach, not often used, to get distortion down and keep some excursion benefits.
Anyway, sorry to sound like a therapist but that was the intent
Honestly, I'm not fed up with B&C at all 😀, its actually hard to fault but it doesn't go particularly loud at the more extreme depths. Looking at the predicted models and the realworld performance shows a big discrepancy, had I known this I might have tried something else. This is all just the interaction of basic physics and the limitations of the enclosure size I can accomodate.
We'll see what these XLS's can do and then I can make a more informed decision. I've decided to start out with a 14hz tune using 4x XLS10's in a vented enclosure. This looks to provide the basic qualities of the sealed design down 20hz and below this its then a case of lessening excusion for lower distortion.
It's just a matter of time...
............ bass array ............
😎
<Sith> I have forseen it
............ bass array ............
😎<Sith> I have forseen it
Well, I agree, design constraints mean you can't try it all... Good luck with the XLS's, many people swear by them anyway. No surprise that the B&C's wouldn't do the sealed box trick, if they have a nonlinear suspension designed for vented use.
The issue of modeled vs. real life performance is a bit irksome though, because unless you find out what went wrong with the simulations, you might find similar discrepancies in any other design. And that goes not just for bass extension - the whole alignment would possibly be off, and measuring deep bass output accurately, umm, difficult. I at least don't have any confidence in my data below 100 Hz.
I have to say that I find anything below 40 Hz very hard to hear at all, thanks to Fletcher-Munson, just about any harmonics will overshadow the fundamental. The slope of our hearing sensitivity is close to 24 dB/oct at that point! In other words a woofer playing 20 Hz:
- with an excellent 6% second-harmonic HD,
- or an even more outlandishly low 1.6% 3rd harmonic (corresponding to a 40 Hz harmonic 24 dB down, or a 56 Hz harmonic 36 dB down)
will appear to play the harmonic as loud as the fundamental.
What this means is this: it may well be that any low distortion woofer may just not sound very loud at 20 Hz. Even if it is loud! Apparently it takes 70 dB SPL to even hear pure 20 Hz.
Very true.
The issue of modeled vs. real life performance is a bit irksome though, because unless you find out what went wrong with the simulations, you might find similar discrepancies in any other design. And that goes not just for bass extension - the whole alignment would possibly be off, and measuring deep bass output accurately, umm, difficult. I at least don't have any confidence in my data below 100 Hz.
I have to say that I find anything below 40 Hz very hard to hear at all, thanks to Fletcher-Munson, just about any harmonics will overshadow the fundamental. The slope of our hearing sensitivity is close to 24 dB/oct at that point! In other words a woofer playing 20 Hz:
- with an excellent 6% second-harmonic HD,
- or an even more outlandishly low 1.6% 3rd harmonic (corresponding to a 40 Hz harmonic 24 dB down, or a 56 Hz harmonic 36 dB down)
will appear to play the harmonic as loud as the fundamental.
What this means is this: it may well be that any low distortion woofer may just not sound very loud at 20 Hz. Even if it is loud! Apparently it takes 70 dB SPL to even hear pure 20 Hz.
Very true.
Ant,
Can you post up or email me the following parameters for both the B&C and XLS that you have been using, and I will run some quick checks myself.
Driver Parameters
Fs
Qes
Qms
Vas
Re
Xmax (one way)
Pd or Sd
Power
Box Parameters
Vb
Fb
Can you post up or email me the following parameters for both the B&C and XLS that you have been using, and I will run some quick checks myself.
Driver Parameters
Fs
Qes
Qms
Vas
Re
Xmax (one way)
Pd or Sd
Power
Box Parameters
Vb
Fb
MBK said:
I agree, its not so much that you hear the stuff below 20hz but rather you feel it as a tactile sensation. And equal loudness curves show that we are much less sensitive to deep bass, which explains why a response that measures flat below 100hz sound so boring and also why people use house curves.
I can hear tones down to about 20hz and then 18hz and below is inaudible but you can feel the air pulsating.
richie00boy said:
Here's the data I posted earlier in this thread:
Box details are 58ltrs tuned to 19hz.
I don't have data on the XLS's yet as I haven't measured them yet. I'm using Vik' data for all modelling so far. His measurements are close to the manufacturers specs.
Not to distract you and perhaps this should be in an email but what methods do you use to measure the drivers?
alexcd said:
Usually Audio Tester because its quick and easy. I did used to use Speaker Workshop. Both work well once you've calibrated your soundcard correctly.
OK. I took Re as 5.1 as I found that on a website selling the drive unit. I took averages of your two measured drive units for the rest of the parameters. I also found on the same website that RMS power is 1000W not 2kW.
Excuse the pantsness of the presentation, but it's the details that matter 😀 My sim also shows misleading info pretty much inline with you what got from WinISD insofar as max SPL.
c.f. red line on yours:
However, mine shows that around 30-40 Hz you are running into over-excursion and can't apply the full 1kW the driver is rated to.
Excuse the pantsness of the presentation, but it's the details that matter 😀 My sim also shows misleading info pretty much inline with you what got from WinISD insofar as max SPL.
An externally hosted image should be here but it was not working when we last tested it.
c.f. red line on yours:
An externally hosted image should be here but it was not working when we last tested it.
However, mine shows that around 30-40 Hz you are running into over-excursion and can't apply the full 1kW the driver is rated to.
A single driver with a radiating area of 575cm2 and 11mm xmax producing a 20hz cycle at ~110dB anechoic. 
Even considering port and cabinet gain, its a bit far fetched.
I measured 102dB iin-room! using a calibrated ECM8000 mic and WinMLS Pro. I couldn't get the driver to bottom out but I also couldn't get it to go any louder - it still sounded clean at 102dB though, although I haven't done distortion measurements to back that up.
Even considering port and cabinet gain, its a bit far fetched.I measured 102dB iin-room! using a calibrated ECM8000 mic and WinMLS Pro. I couldn't get the driver to bottom out but I also couldn't get it to go any louder - it still sounded clean at 102dB though, although I haven't done distortion measurements to back that up.
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