"BEST" Woofer 50Hz - 300Hz & Hi eff, maybe 15" ?? - Page 16 - diyAudio
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Old 24th November 2011, 11:48 PM   #151
CLS is offline CLS  Taiwan
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On OB, woofers hit Xlimit first and way earlier than in box, power rating is not important. In such situation, woofers never operate in high power range.

Xlimit of PD1550 is 22mm, not very large. If played naked (without any baffle at all), it's easily bottomed indeed.

I've also bottomed a 18" with 18mm Xlimit. It's not loud, really -- if only the frequency is low enough. You'd see the cone moving hard but no sound.
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Old 25th November 2011, 12:55 AM   #152
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Default open baffle as in with a baffle not "naked"

Hi CLS,

Agreed, if you run a driver naked you can easily hit its end stops at low spl's.

My baffles areVPL ( see photos on my old posts a year or 2 ago) with an effective average width of over 3 feet ( 95cm) so I was getting very good extension at high SPL's.

It is the Fs of the driver that limits F3 in my VPL baffles. Only as I get close to Fs do I need to add a little Eq to get down to 30Hz ish. But too much Eq is bad as it gobbles up XMax and forces up cone travel and that then mucks up the whole bandwidth the driver is covering for the sake of 5 or 10Hz.

Do you use a DEQX or similar DSP based crossover?

Thanks

Derek.
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Old 25th November 2011, 03:29 AM   #153
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Originally Posted by Overkill Audio View Post
..... But too much Eq is bad as it gobbles up XMax and forces up cone travel and that then mucks up the whole bandwidth the driver is covering for the sake of 5 or 10Hz.
....
Agreed.

I use amp(s) with high output impedance (20 Ohm) to boost the range near fs, and line level passive filter for additional shaping. I also use digital EQ but not for this purpose.

Er... we're drifting OT now. Better stop.
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Old 25th November 2011, 02:12 PM   #154
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But neither sensitivity nor efficiency, or a combination of the two really tells us much about how a given driver will sound.

The cone itself doesn't "know" much about the power used to make it wag... so whatever harmonics are present and dynamic range limitations and the combination of % and nature of harmonics WRT power level are really what is important.

Even then that tells us nothing much about the perceived and subjective sound...

In my case the only reason for high sensitivity is a pragmatic one, to avoid using another amplifier in the system. Which may turn out to be the wrong way to go in the end.

_-_-bear
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Old 25th November 2011, 02:20 PM   #155
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Quote:
Originally Posted by bear View Post
But neither sensitivity nor efficiency, or a combination of the two really tells us much about how a given driver will sound.

The cone itself doesn't "know" much about the power used to make it wag... so whatever harmonics are present and dynamic range limitations and the combination of % and nature of harmonics WRT power level are really what is important.

Even then that tells us nothing much about the perceived and subjective sound...

In my case the only reason for high sensitivity is a pragmatic one, to avoid using another amplifier in the system. Which may turn out to be the wrong way to go in the end.

_-_-bear
My preference for higher sensitivity drivers is my assumption that the lower the cone movement for a given SPL, the lower the distortion. I know this is not always the case, but it is a very general rule of thumb for me.
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Old 25th November 2011, 02:20 PM   #156
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Thinking more about Tom Danley's multiple looped recordings of his speakers... it seems to me that the primary thing that will occur will be the emphasis of frequency response aberrations (amplitude).

One of the big problems (speculating) is that the contribution of the environment can not really be factored out, and that alone will cause a "shift" in what his heard back on the recordings. Seems like the best shot at this would be in an anechoic environment. Even then, mic placement and distance will still play a significant role - as will mic selection!

I was thinking about this because what I am looking for is this pesky middle bass region only, and considering how to apply the Danley multiple recording loops/iterations to ONLY this range. Maybe compare it to an electronically bandpassed signal? That too presents obvious difficulties when one goes to compare...

The other issue is that the flatest speakers do not always subjectively sound the best. Although that is an area for discussion and investigation.

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Last edited by bear; 25th November 2011 at 02:25 PM.
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Old 25th November 2011, 02:22 PM   #157
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Quote:
Originally Posted by bear View Post
But neither sensitivity nor efficiency, or a combination of the two really tells us much about how a given driver will sound.

The cone itself doesn't "know" much about the power used to make it wag... so whatever harmonics are present and dynamic range limitations and the combination of % and nature of harmonics WRT power level are really what is important.

Even then that tells us nothing much about the perceived and subjective sound...

In my case the only reason for high sensitivity is a pragmatic one, to avoid using another amplifier in the system. Which may turn out to be the wrong way to go in the end.

_-_-bear
The cone itself doesn't "know" much about the power, but the voice coil. More power means more enhancement of voice coil's temperature and thus more enhancement of dc resistance. Thus a large BL product (strong magnet) and a highest possible efficiency means always better sonic quality, because the unwanted variations of temperature/DC-resistance while music reproduction is reduced.

Why use e. g. Precision Devices by some models very large magnet units?
And Supravox even an electromagnet assembly ?

Last edited by tiefbassuebertr; 25th November 2011 at 02:28 PM.
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Old 25th November 2011, 02:23 PM   #158
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Originally Posted by dirkwright View Post
My preference for higher sensitivity drivers is my assumption that the lower the cone movement for a given SPL, the lower the distortion. I know this is not always the case, but it is a very general rule of thumb for me.
Afaik, the cone movement does not change between equivalent cone structures based on a variance in motor construction, meaning the SPL is solely based on cone motion be it provided by a 1,000 watt signal or a 1 watt signal, the difference being in the conversion of energy in the motor.

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Old 25th November 2011, 02:35 PM   #159
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Quote:
Originally Posted by tiefbassuebertr View Post
The cone itself doesn't "know" much about the power, but the voice coil. More power means more enhancement of voice coil's temperature and thus more enhancement of dc resistance. Thus a large BL product (strong magnet) and a highest possible efficiency means always better sonic quality, because the unwanted variations of temperature/DC-resistance while music reproduction is reduced.

Why use e. g. Precision Devices by some models very large magnet units?
And Supravox even an electromagnet assembly ?
Tief, The heating of the VC is typically taken into account in terms of "dynamic compression" when it comes to pro drivers. That seems to only occur at higher power levels... If there have been any studies showing the effects of dynamic changes in Re WRT power input (heating) at lower power levels on the resulting sound, I haven't seen any yet. Doesn't mean it's not out there... got any?
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Old 25th November 2011, 05:50 PM   #160
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Hi Tom,

I see you are busy on other threads but it would be great to hear your thoughts on the attached doc.
I have huge respect for you and your loudspeaker designs...Your opinion counts to me and so many others on this forum and the doc raises some important issues that will really help DIY'ers choose the right drivers and how best to use them... it will for me anyway!!

I wrote the doc a few years ago and never had it " reviewed " by an independant expert...please, please have a read...Feel free to blow it out the water or disagree or whatever, I will not be offended!!

Thanks
Derek.
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