Balancing between dynamics and bass depth in moderate SPL levels - diyAudio
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Old 8th September 2011, 07:07 AM   #1
alspe is offline alspe  Finland
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Default Balancing between dynamics and bass depth in moderate SPL levels

I've been thinking about how to balance speakers between their dynamics (efficiency) and depth / quality of bass if enclosure's size is locked.

There has been discussion how closed box sound is more natural in room than many reflex designs. You can have deep bass from closed box but you have to sacrifice efficiency because driver cannot be too large for Vbox AND drivers Qts must be highish that it can resonate low. So weak motor and low efficiency usually. You can have lower bass by putting reflex tube in a box but in many cases it is not so natural than closed. (do not go to closed vs. reflex in this thread)

Here is about to begin discussion that dynamic capability is far more important than frequency response or purity of sound. Compression of weak drivers make sound irritating because of rising amount of distortion but also lack bass depth in more efficient drivers makes sound "imperfect" and lacking air and ease. Maybe hollow and dry if too bass is lacking.

Somehow I see piece of truth in both worlds. I think it is matter of sound pressure levels used and good speaker has nice balance between them. HOW important is efficiency if one listens at home at levels around 70-90 dB + peaks? Is loudspeaker of efficiency 85 dB/W with quite deep bass loudspeaker at all? Can it indicate dynamics of music like 95 dB/W speaker IF they are used at moderate levels at home?

Has music genre something to do with this matter? I have thought about "hifi music" that has good dynamics left and soft passages between notes, they play well at almost all setups. RMS power to voice coild of speaker is low so it can cool and produce dynamics. But what if music is very intensive hard rock which SPL level is high because music itself has no passages. Should loudspeaker have more efficiency (cooling capacity) for natural production of dynamics (what is left in that kind of music).

Last edited by alspe; 8th September 2011 at 07:10 AM.
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Old 8th September 2011, 07:24 AM   #2
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Your assumptions about a speaker for a closed box design are not all correct. Choosing a lower sensitivity driver will be a good trade-off for better depth, but not when the driver's Qts is rather high.

Often this situation occurs but what you need for a good closed box design is a woofer with strong drive and low Qts, together with a soft suspension and very low Fs. Then put it in a box with a volume of about half or less than Vas to gain a Qtc of 0.5 - 0.7. In this situation, the compliance of the box dominates over driver compliance, better reaching the theoretical maximum out of a given box.

Putting a high Qts driver in a box > Vas is definitely not the way to go...

By the way, if you speak German this is a nice page on the subject: http://www.hifi-selbstbau.de/index.p...=116&Itemid=35

About efficiency, I think 85 dB is good enough, since a decent bass driver will be able to handle 100 Watts. When driven continuous it would lead to power compression, but most people would reach 100 dB+ levels only on peaks...

Last edited by a_tewinkel; 8th September 2011 at 07:29 AM.
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Old 8th September 2011, 08:03 AM   #3
alspe is offline alspe  Finland
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Quote:
Originally Posted by a_tewinkel View Post
About efficiency, I think 85 dB is good enough, since a decent bass driver will be able to handle 100 Watts. When driven continuous it would lead to power compression, but most people would reach 100 dB+ levels only on peaks...
Yes, they can "handle" (without burning or mechanical damage (in some enclosures)). But how it is heard in sound when you compare it to 95 dB/W driver (that can handle 400-500W) driven at 10 watts to achieve same SPL?
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Old 8th September 2011, 08:21 AM   #4
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Like I mentioned above, a decent woofer will probably only suffer from mild power compression on peaks, which tends to be far less audible.

If there is no significant power compression in the lower efficiency system, then there is no audible difference between the two.

One thing must be considered though. The higher efficiency system must have a much larger driver and box (if it is supposed to go just as low) en will therefore suffer less from distortion from air compression in the box, suspension non-linearity and changes in voice coil inductance because of lower excursion for a given SPL compared to the smaller, lower efficiency system.

Whether this leads to audible differences depends on how much you push the system of course.
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Old 8th September 2011, 06:27 PM   #5
alspe is offline alspe  Finland
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So there is nothing much to discuss about this subject? I thought that there would be...
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Old 9th September 2011, 10:09 AM   #6
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There's not much to say , or the opposite ,because the guidelines that lead someone to put 2 x 15" instead of a little 6.5" in a room are dictated by the room itself , the listening levels and which kind of music you listen abitually .
You have just described my passage from a ( still to finish... ) BIG 3 way at about 94 dB efficiency to a small two way that is 85 dB .
The problem is really thermal !! After 1 hour of BUM Bum Bum the basket was hot !Also the coil for lowpass ( 1mm diameter ). But that was not for what they were intended for . Indeed they play nice piano and everything at low-mid listening levels .
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Old 9th September 2011, 01:53 PM   #7
alspe is offline alspe  Finland
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I think there is lot to discuss about. If we keep enclosure size locked we lose bass depth as we gain efficiency. Where is good compromise in different listening environments and habits? Do we achieve "reality" to sound if headroom is gained by losing bass depth?
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Old 9th September 2011, 02:34 PM   #8
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Correct bass reproduction is the most difficult thing before enclosure... We must talk about room, size and damping of the room ?

I have made a small closed box 20L with a 8" inside F3=50Hz. In small room <30m, no bass ! But in a big room (>60m) with acoustic treatments, this speaker made big bass !

Can we talk about bass without talking about rooms ?
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Old 9th September 2011, 05:17 PM   #9
erjee is offline erjee  Netherlands
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Quote:
Originally Posted by jerome69 View Post

Can we talk about bass without talking about rooms ?
No, low frequency reproduction is dominated by the room.
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