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Author Topic: Which subs to buy? Paralysis by analysis  (Read 19032 times)

Mark Monson

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Which subs to buy? Paralysis by analysis
« on: October 05, 2014, 01:25:08 am »

My classic rock band has been in the market for subs for the past 6 months, but every time we think we know what we want we find out about another sub that may work better for us.  We have Peavey QW4 for mains.  One of the main problems is that we can't find anywhere to listen to most of the subs, let alone A/B them.  We have looked at Peavey QW218, then VR 218, JBL SRX 728, STX 828, EV Qrx 218, Yorkville LS 1208, LS 2104 (which seems to be a real good sub on paper, but we can't find much information about it) Danley TH 118 and JTR Orbit Shifter.  My impression from reading comments on the internet is that the Danley may be a cut above the rest.  The sensitivity is listed at 108db 1w 1m.  Does this mean that it would take only 25% of the power to produce the same spl as a sub with 102db sensitivity? (or am I not understanding the 3db=2x the power rule).  Saving on power amps would certainly be a plus.  Right now we are leaning towards new VR 218 or used TH118.  We would appreciate some help from any of you who have heard these subs.

thank you
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David Sturzenbecher

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Re: Which subs to buy? Paralysis by analysis
« Reply #1 on: October 05, 2014, 07:30:09 am »

Danley doesn't rate their subs with 1W 1M. They use 2.83V.  Which for an 8 ohm cabinet is essentially 1W/1M.  But for a 4ohm cabinet it's more like 2W/1M.  So a TH-118 would have to be derated by 3dB to compare "spec for spec" to other 4 ohm subs.... Which isn't the best practice anyway. Your best bet is to do exactly what you did, and listen for yourself.


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Ivan Beaver

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Re: Which subs to buy? Paralysis by analysis
« Reply #2 on: October 05, 2014, 10:10:49 am »

Danley doesn't rate their subs with 1W 1M. They use 2.83V.  Which for an 8 ohm cabinet is essentially 1W/1M.  But for a 4ohm cabinet it's more like 2W/1M.  So a TH-118 would have to be derated by 3dB to compare "spec for spec" to other 4 ohm subs.... Which isn't the best practice anyway. Your best bet is to do exactly what you did, and listen for yourself.


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The reason we use 2.83 volt for everything-is very simple.  People who say they are "applying 1 watt" are lying.

They are apply A VOLTAGE- and the resultant wattage depends on the impedance.

HOWEVER the impedance is not what the specs say-it may be at some freq-but could be higher or lower at other freq.

So for an 8 ohm speaker (at the freq that the actual impedance IS 8 ohms)-2.83V is 1 watt.  At other freq for that same freq the power could be more, but in many cases is less.  It just depends.

The spec numbers choosen by manufacturers come down to the nearest "standard" value-2-4-8-26 ohms.

People get REAL confused if you say a speaker has an average impedance of 6 ohms.  Even though that statement may be correct-they simply cannot figure out what amp to use-since they don't see ratings for 6 ohms.

Call that same speaker 4 ohms and everybody is happy.

Take our Th115 4 ohm for example.  It is not 4 ohms, but closer to 5 ohms-if you look at the IMPEDANCE CURVE.  But 4 is the closest standard value so that is the rating.

This is yet another example of trying to use a "simple answer" to a complex question.

Agreed the best thing is to LISTEN-because there are many things that show up sonically that do not show up on a spec sheet.

And listen at both low and loud levels.  What happens at a lower level does not always translate to what happens at higher levels.

And when looking at max SPL-yes those are calculated numbers that the speaker can produce.  But that DOES NOT mean you actually want to listen to the speaker at that level.  Some sound fine at higher levels and other not so fine.  But you don't find that on the spec sheet-ONLY by listening.
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Ivan Beaver
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Ivan Beaver

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Re: Which subs to buy? Paralysis by analysis
« Reply #3 on: October 05, 2014, 11:05:09 am »

Something else you HAVE to consider.

Where does the sensitivity number ACTUALLY come from?  It would be nice if all subs had a flat response-but they don't.

Is it some peak in the response-or an average within the intended operating range of the loudspeaker?  Those can be QUITE different.  And the peak number is not lying-but it certainly is not "telling the truth".

Without a measured freq response curve-it could be at freq COMPLETELY out of the operating band of the sub.

A very famous manufacturer used to have rating for their subs that were "20-20Khz".

That's what we want-right?  full freq measurement?"

NO

In one case a 2x 18" had a VERY high sensitivity rating-but it was for a peak at 1800Hz.

COMPLETELY out of the range of intended usage.  They did not lie-they just did not "answer the  question" the way people want it answered.

With subs-most can get pretty loud above 100hz.  So if the "specs" were taken at say 150Hz, then how well can you translate into how loud it will be below 80Hz.

You can't, without a measured response curve..

THAT is why it is SO important to see the response curve-and see how loud it is at particular freq-NOT just take the "simple data" from the spec sheet.

I have seen quite a number of subs that state low freq points of say -3dB, but when you look at THEIR OWN measured data, the actual level is more like 9dB down.  I have actually seen some products that are 20dB down at the "stated -3dB" point.

You HAVE to look closer to get the real answer.

Of course listening will often separate the products quickly with things that don't show up on spec sheets.
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A complex question is easily answered by a simple-easy to understand WRONG answer!

Ivan Beaver
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Mac Kerr

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Re: Which subs to buy? Paralysis by analysis
« Reply #4 on: October 05, 2014, 11:05:45 am »

The reason we use 2.83 volt for everything-is very simple.  People who say they are "applying 1 watt" are lying.

They are apply A VOLTAGE- and the resultant wattage depends on the impedance.

HOWEVER the impedance is not what the specs say-it may be at some freq-but could be higher or lower at other freq.

So for an 8 ohm speaker (at the freq that the actual impedance IS 8 ohms)-2.83V is 1 watt.  At other freq for that same freq the power could be more, but in many cases is less.  It just depends.

The spec numbers choosen by manufacturers come down to the nearest "standard" value-2-4-8-26 ohms.

And by using those "standard values" their 4Ω speakers don't automatically seem 3dB louder because they are just as arbitrarily seeing 2.83V as opposed to the voltage that corresponds to 1W into 4Ω. Using a different standard of applied signal just means specs can't be directly compared between speakers, neither one is more correct or more accurate than the other, it is just a matter of symantics.

Yes, the language of 1W/1m is not as specific as 2.83V, but the value of 2.83V is either completely arbitrary, or it's based on the same assumption of 8Ω as a "standard" impedance.

Mac
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Scott Bolt

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Re: Which subs to buy? Paralysis by analysis
« Reply #5 on: October 05, 2014, 01:03:13 pm »

Ivan,

Nice comprehensive explanation!

The only thing I would add to your very comprehensive explanation is that there is no specification in existence that can tell you if the speaker sounds good.

The best way is to hear them ;)
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Mark McFarlane

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Re: Which subs to buy? Paralysis by analysis
« Reply #6 on: October 05, 2014, 01:29:52 pm »

...

I have seen quite a number of subs that state low freq points of say -3dB, but when you look at THEIR OWN measured data, the actual level is more like 9dB down....


Perhaps because they call the peak +6db? Or it's -3db from the average across some unknown freq range.  The fun of spec sheets.

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Ivan Beaver

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Re: Which subs to buy? Paralysis by analysis
« Reply #7 on: October 05, 2014, 02:16:05 pm »

And by using those "standard values" their 4Ω speakers don't automatically seem 3dB louder because they are just as arbitrarily seeing 2.83V as opposed to the voltage that corresponds to 1W into 4Ω. Using a different standard of applied signal just means specs can't be directly compared between speakers, neither one is more correct or more accurate than the other, it is just a matter of symantics.

Yes, the language of 1W/1m is not as specific as 2.83V, but the value of 2.83V is either completely arbitrary, or it's based on the same assumption of 8Ω as a "standard" impedance.

Mac
Except you can easily apply 2.83v and measure it and be consistent

You cannot apply 1 watt at least not consistently due to the varying impedance
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A complex question is easily answered by a simple-easy to understand WRONG answer!

Ivan Beaver
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Ivan Beaver

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Re: Which subs to buy? Paralysis by analysis
« Reply #8 on: October 05, 2014, 02:25:40 pm »

And by using those "standard values" their 4Ω speakers don't automatically seem 3dB louder because they are just as arbitrarily seeing 2.83V as opposed to the voltage that corresponds to 1W into 4Ω. Using a different standard of applied signal just means specs can't be directly compared between speakers, neither one is more correct or more accurate than the other, it is just a matter of symantics.

Yes, the language of 1W/1m is not as specific as 2.83V, but the value of 2.83V is either completely arbitrary, or it's based on the same assumption of 8Ω as a "standard" impedance.

Mac
I would also that many if not all 4 ohm subs are dissipating well under 1 watt at some freq

So using the 1 watt designation is as bad as using a sensitivity number that is high because it is outside of the operating band

Once you start talking average within the operating band everything starts to change-the powe the sensitivity, the impedance etc

At least with 2.83volts that does not change with freq so it is constant and continuous regardless of freq

That is the reason we use it. Even if it is different than the falsehood that some people think they understand-but are wrong
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A complex question is easily answered by a simple-easy to understand WRONG answer!

Ivan Beaver
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Keith Broughton

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Re: Which subs to buy? Paralysis by analysis
« Reply #9 on: October 05, 2014, 04:39:31 pm »

My classic rock band has been in the market for subs for the past 6 months, but every time we think we know what we want we find out about another sub that may work better for us.  We have Peavey QW4 for mains.  One of the main problems is that we can't find anywhere to listen to most of the subs, let alone A/B them.  We have looked at Peavey QW218, then VR 218, JBL SRX 728, STX 828, EV Qrx 218, Yorkville LS 1208, LS 2104 (which seems to be a real good sub on paper, but we can't find much information about it) Danley TH 118 and JTR Orbit Shifter.  My impression from reading comments on the internet is that the Danley may be a cut above the rest.  The sensitivity is listed at 108db 1w 1m.  Does this mean that it would take only 25% of the power to produce the same spl as a sub with 102db sensitivity? (or am I not understanding the 3db=2x the power rule).  Saving on power amps would certainly be a plus.  Right now we are leaning towards new VR 218 or used TH118.  We would appreciate some help from any of you who have heard these subs.

thank you
Grab some TH118s. you won't be dissapointed.
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Re: Which subs to buy? Paralysis by analysis
« Reply #9 on: October 05, 2014, 04:39:31 pm »


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