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Old 5th November 2011, 12:29 PM   #11
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Quote:
Originally Posted by chris661 View Post
The usual one people quote is that the cones are much lighter, so the bass sounds "fast". This is rubbish.

A 50Hz wave can neither be fast nor slow. The thing that makes people think the bass is "fast" and "tight" is a lack of low frequency extension, usually associated with sealed cabinets.

Chris
I think what most people call "fast" is really that they mean more articulated or defined bass. Getting caught up with the word fast isnt worth debating. When people say it sounds slow, is it possible they mean muddy, or less defined? I think we can agree that a poor box design can cause one-note-bass. Too high a port tuning frequency can cause this and that has less bass extension.

While it can be argued back and forth that all sub bass is slow, there is most certainly a difference in articulation. I will buy that a heavier 15" cone can move faster than a 12 if it has a bigger motor that the 12, but in general, if youre saying that all subs move at the same speed, I disagree. Anything that weighs more will have an issue starting and stopping and there is most certainly a sound difference if you have the same motor pushing two different masses. A poorly designed driver with insufficient motor vs cone mass, will ovrshoot where the cone is supposed to be in reference to the next note.....slow. A too high of a port tuning frequency has the port ringing at a frequency longer than it should in reference to the drive signal....slow. Even a ported design from the start has a phase difference/time difference from the port referenced to the forward going cone sound....slow.

Regardless of what you want to call it, there are better or worse sounding subs and filtering out the low end with a high pass filter to reduce extension doesnt make a bad 15 sound like a great 12 in regard to what people call speed. There is more to it than that. In most cases a bad box design, sealed or ported, affects articulation/definition. I wont call it speed from now on when trying to describe subjective sound quality as so many get all worked up about terminology. While subjective tastes most certainly preclude there ever being a truly optimum box for all tastes, I think we can all agree that a sealed box Qtc of 2.0 sounds bad to everyone in terms of articulation and it also has the most limited bass extension. So yes, a 50hz wave through a sub can sound defined or muddy, or what people tend to call speed if the cone is not where its supposed to be referenced to the drive signal. I guess its distortion one way or another.

Last edited by SpinMonster; 5th November 2011 at 12:40 PM.
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Old 5th November 2011, 12:48 PM   #12
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I think what people think of as "speed" is really about control (and to some extent power) ... stop and start of the cone motion ... at somewhat higher sub or low-bass frequencies; say, around 50~80 Hz. Lower frequencies are as much felt as heard.

I don't think it's fundamentally about very low bass, although I might agree it's about perceived bass rather than true very LF reproduction.

If you can stand in front of the woofer and your pant legs are blown back with a "puff of air" with each hit of the kick drum, you've got an idea of what I mean.

I don't use "fast bass" as a term myself, nor it's corollary "slow" as I agree they have no meaning to me in relation to LF reproduction.
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Last edited by Johnny2Bad; 5th November 2011 at 12:59 PM.
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Old 5th November 2011, 01:50 PM   #13
Boscoe is offline Boscoe  United Kingdom
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How would you make a good sub? I have been thinking about this a lot lately, there's a lot of people who swear by sealed over ported saying ported systems boom and aren't controlled but I think this is more small cheap subs with high cone mass in small boxes tuned incorrectly, am I right? I can't imagine a large ported 300l box with a light coned 15" will sound 'muddy' unless cheap components are used and incorrectly implemented? Am I right?

What thinks should I look for in ported systems?
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Old 5th November 2011, 04:14 PM   #14
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Do you think that you can hear nuances and detail in the start and stop of transients at 30Hz? How about 60Hz? 90Hz? How long do you think it takes the human ear register the pressure change at these bass frequencies? How about to register the tone or pitch?

Certainly there can be issues with ringing and "muddy" or undefined bass. IMHO these have way more to do with frequency response, distortion characteristics, signal decay, enclosure resonances, inductance, dynamic compression and probably more important than all of the rest is the effect of the room that the bass system is placed in. All of these variables would completely swamp minor differences in acceleration and deceleration of a cone and usually are what impacts someones subjective opinion of "fast" bass. IMO.

Flat and extended deep bass response usually sounds muddy or slow compared to a rolled off bass response. Try taking a deeply extended vented sub and then EQ it to have the roll off of a sealed design it will suddenly sound much more "tight" and "tuneful" The fastest bass response subjectively is usually one where there is no real bass at all. The most accurate and clean sounding bass drivers that I have used have all been 15" or larger. That's been my experience YMMV.
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Old 5th November 2011, 04:42 PM   #15
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SpinMonster, while you've raised a couple of points I agree with, I ask this of you: how fast do you think these cones actually have to move?

Assuming 12mm p/p travel at 50Hz, it would move 12mm in 0.01s. This translates to 1.2m/s. Not particularly fast - even a very basic motor would keep that in check.
For a given frequency and a given amount of excursion, the cone will move at exactly the same speed. Because these speeds are so low for <80Hz, the cone won't overshoot.

It's only when you're talking about midbass duties (where the cone moves much faster due to the higher frequencies involved) that you get problems: 500Hz at the same 12mm p/p travel needs the cone to move much faster: 12m/s. This will almost certainly cause the cone to overshoot, unless, as you rightly say, a suitably powerful motor can keep the cone under control. That sort of frequency would be the harmonics of a bass drum: the overshoot wouldn't do the sound any favours, that's for sure.

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Old 5th November 2011, 05:49 PM   #16
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Originally Posted by Boscoe View Post
How would you make a good sub? I have been thinking about this a lot lately, there's a lot of people who swear by sealed over ported saying ported systems boom and aren't controlled but I think this is more small cheap subs with high cone mass in small boxes tuned incorrectly, am I right? I can't imagine a large ported 300l box with a light coned 15" will sound 'muddy' unless cheap components are used and incorrectly implemented? Am I right?

What thinks should I look for in ported systems?
I don't have a hard preference sealed/ported; you can make a good sub either way. The choice of which is more a reflection of what you have to start with (say, you have a woofer sitting on the bench ... it will have certain suspension compliance and parameters ... is it more suited for sealed or ported loading?) and your goals (is it going into a car? You will have fairly significant cabin gain to use or consider).

All taken along with your goals ... compact size? Flat response or impressive sound effects? Your own preferences ... what is more important ... high SPLs? And so on.

Sit down and list your criteria. Think about acceptible size of enclosure, power availability, the location, the source (music, movie), the associated components, whether you can actually play loud without breaking the lease or having visits from the local constabulary, etc.

The more criteria you can come up with, the better. Then order them in importance, have a few mandatory ones and the rest you can compromise a bit on. ("No compromise" is a difficult road to travel and will cost you money, even if inexpensive drivers are involved).

What are you "stuck with" and can't or don't want to change (what will power it, do you have drivers already, or what are available to you at your budget, etc)? Those are mandatory criteria.

Don't ignore the rest of the system ... a decent sub should match well with the characteristics of the LF~HF response it's supposed to mate with. The "wrong" sub that blends smoothly probably will sound better than the "perfect" sub that clashes with the rest of the system.

If you've heard systems with the bass you like, find out what construction was used. Try to improve on that system if you can (the fun of DIY).

If you find it overwhelming, start with a specific driver and try to model the ideal configuration. Or, decide on a budget and see what drivers are available, and model a few of those. Limiting your choices makes it simpler.
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Last edited by Johnny2Bad; 5th November 2011 at 05:56 PM.
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Old 5th November 2011, 06:06 PM   #17
Boscoe is offline Boscoe  United Kingdom
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Quote:
Originally Posted by Johnny2Bad View Post
I don't have a hard preference sealed/ported; you can make a good sub either way. The choice of which is more a reflection of what you have to start with (say, you have a woofer sitting on the bench ... it will have certain suspension compliance and parameters ... is it more suited for sealed or ported loading?) and your goals (is it going into a car? You will have fairly significant cabin gain to use or consider).

All taken along with your goals ... compact size? Flat response or impressive sound effects? Your own preferences ... what is more important ... high SPLs? And so on.

Sit down and list your criteria. Think about acceptible size of enclosure, power availability, the location, the source (music, movie), the associated components, whether you can actually play loud without breaking the lease or having visits from the local constabulary, etc.

The more criteria you can come up with, the better. Then order them in importance, have a few mandatory ones and the rest you can compromise a bit on. ("No compromise" is a difficult road to travel and will cost you money, even if inexpensive drivers are involved).

What are you "stuck with" and can't or don't want to change (what will power it, do you have drivers already, or what are available to you at your budget, etc)? Those are mandatory criteria.

Don't ignore the rest of the system ... a decent sub should match well with the characteristics of the LF~HF response it's supposed to mate with. The "wrong" sub that blends smoothly probably will sound better than the "perfect" sub that clashes with the rest of the system.

If you've heard systems with the bass you like, find out what construction was used. Try to improve on that system if you can (the fun of DIY).

If you find it overwhelming, start with a specific driver and try to model the ideal configuration. Or, decide on a budget and see what drivers are available, and model a few of those. Limiting your choices makes it simpler.
Thanks for the help. I used to be quite happy with my thoughts on sound quality of different alignments but lately that has been questioned due to another forum/ manufacturer.

The reason is I want true hifi I want ultimate sound quality with extension.

My list (top is highest priority),

Sound quality
Extension to at the very least 30Hz (but this isn't much improvement on my current subs so I don't really want to do that) I want 20Hz.
Size absolute max is 150l
SPL ~ 110dB max, I'm not after room shaking but I want a reasonable overhead.
Amp power isn't a problem.

The thing is I realise I'm asking too much and it's frustrating me, the LAB 12s come closest thought but I question the sound quality of ported systems. I will get my proposed design together see what you think.
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Old 5th November 2011, 06:09 PM   #18
Boscoe is offline Boscoe  United Kingdom
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I've come to conclusion it's not much to do with parameters but the quality of the driver that magics smaller box sizes!
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Old 5th November 2011, 06:38 PM   #19
Djim is offline Djim  Netherlands
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Do you think that you can hear nuances and detail in the start and stop of transients at 30Hz? How about 60Hz? 90Hz? How long do you think it takes the human ear register the pressure change at these bass frequencies? How about to register the tone or pitch?
Transients in Low Frequency are relative long because of the wavelength and are very good detectable by the ear! For instance one full wave at 30Hz takes 33ms to develop while at 1Khz it’s only 1ms and both could be a transient.
The reason we don't hear it that easy from our loudspeakers is because of the limitations of the system and acoustic circumstances (release times, impulse behaviour, ring effects, echo's and so on) .

In practice a good recording engineer should be able to detect low frequency transients to be able to set his attack times (in milliseconds) for compressor values. Also he can influence the "feel" between the drum section and the bass track by changing the bass in time by just a few milliseconds.

Detecting pitch, based on one wavelength, is not possible at any frequency. The total of wavelengths needed to detect pitch depends on natural talent and training.

Small note: You can hear the difference from your TH of the direct signal from the driver (half amplitude) and the amplified signal from the tube/horn (full amplitude) which gives the TH a 'typical character'.

Last edited by Djim; 5th November 2011 at 06:40 PM.
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Old 5th November 2011, 06:39 PM   #20
tb46 is offline tb46  United States
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Hi Boscoe,

Can you share some information as to the room and the rest of the system?

Regards,
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