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Author Topic: Higher dampening factor for folded horn subs?  (Read 10536 times)

Kevin Graf

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Re: Higher dampening factor for folded horn subs?
« Reply #10 on: January 12, 2016, 08:30:03 am »

The debate over damping factor is hardly a recent one. For example, the following letter appears in the August 1947 issue of Wireless World:

That's from:

Damping Factor: Effects On System Response
Dick Pierce
Professional Audio Development

http://www.cartchunk.org/audiotopics/
http://www.cartchunk.org/audiotopics/DampingFactor.pdf
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John Roberts {JR}

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Re: Higher dampening factor for folded horn subs?
« Reply #11 on: January 12, 2016, 08:40:16 am »

The debate over damping factor is hardly a recent one. For example, the following letter appears in the August 1947 issue of Wireless World:

That's from:

Damping Factor: Effects On System Response
Dick Pierce
Professional Audio Development

http://www.cartchunk.org/audiotopics/
http://www.cartchunk.org/audiotopics/DampingFactor.pdf
Allow me to rephrase,,, "Damping factor is a very old concern"... In 1947, audio power amps used vacuum tubes which were inherently higher output impedance than modern solid state amps.  Back then (before even I was born) Damping factor was a valid specification to pay attention to when selecting between amplifiers.

Today the amplifier DF can be ignored and system DF considered only in the context of specifying the speaker wire.

JR
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David Sturzenbecher

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Re: Higher dampening factor for folded horn subs?
« Reply #12 on: January 12, 2016, 09:22:41 am »

Because when you drive the loudspeaker bridged you have two amplifier output impedance's in series, instead of one so DF is roughly halved all else equal.

This falls under the category of true but irrelevant... Wire losses will still dominate DF in use with modern solid state amplifiers.
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A larger lesson here is that internet threads generally end up full of numerous true facts but not all are significant. Learn to separate the wheat from the chaff.

JR

If you bridge the amp from the NL4 jack vs bridge an amp from the terminals there will be no practical difference as they are the same connection.
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Tim McCulloch

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Re: Higher dampening factor for folded horn subs?
« Reply #13 on: January 12, 2016, 09:36:12 am »

Because when you drive the loudspeaker bridged you have two amplifier output impedance's in series, instead of one so DF is roughly halved all else equal.

This falls under the category of true but irrelevant... Wire losses will still dominate DF in use with modern solid state amplifiers.
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A larger lesson here is that internet threads generally end up full of numerous true facts but not all are significant. Learn to separate the wheat from the chaff.

JR

You need to take another look at the post David is replying to.  It's about physical termination.
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John Roberts {JR}

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Re: Higher dampening factor for folded horn subs?
« Reply #14 on: January 12, 2016, 09:58:47 am »

If you bridge the amp from the NL4 jack vs bridge an amp from the terminals there will be no practical difference as they are the same connection.
Sorry I was referring to bridged vs non-bridged having a 0.5x DF difference.

There can be numerical differences between amplifier DF specifications related to the physical interface. This will be most noticeable, the higher the max numerical DF of the amplifier alone***, since even a few mOhm of connector resistance will matter to a 1000x DF. Again this is all moot once you add some speaker wire resistance.

 JR

*** I recall one high DF amp model that Peavey sold last century. The DF could be  >2000x but we could only guarantee that high number for one of the several output connector configurations. A few mOhms here and there from inches of wire, or different contact resistance dropped that headline number measurably.

Silly high DF numbers are purely a marketing exercise, Peavey did it for exactly one model and then moved on. Some still think it is important. 
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Jamin Lynch

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Re: Higher dampening factor for folded horn subs?
« Reply #15 on: January 12, 2016, 10:43:48 am »

Sorry I was referring to bridged vs non-bridged having a 0.5x DF difference.

There can be numerical differences between amplifier DF specifications related to the physical interface. This will be most noticeable, the higher the max numerical DF of the amplifier alone***, since even a few mOhm of connector resistance will matter to a 1000x DF. Again this is all moot once you add some speaker wire resistance.

 JR

*** I recall one high DF amp model that Peavey sold last century. The DF could be  >2000x but we could only guarantee that high number for one of the several output connector configurations. A few mOhms here and there from inches of wire, or different contact resistance dropped that headline number measurably.

Silly high DF numbers are purely a marketing exercise, Peavey did it for exactly one model and then moved on. Some still think it is important.

Does it cost more to manufacture an amplifier with a higher DF than an amp that has a lower DF?
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John Roberts {JR}

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Re: Higher dampening factor for folded horn subs?
« Reply #16 on: January 12, 2016, 11:38:55 am »

Does it cost more to manufacture an amplifier with a higher DF than an amp that has a lower DF?

It doesn't cost more to deliver decent acceptable DF, while it does require attention to detail with short internal output wires, low impedance output filters, and smart negative feedback connection placement. For class D amps the output filter can have some cost impact if going for silly high DF.

When marketing gets hold of turning the DF spec into a selling point it can result in dollars added to the BOM, but if it results in taking more sales from competitors it was arguably not completely wasted.

The Peavey approach probably added a couple dollars to the BOM, as I recall there was a patented circuit that involved a floating transformer (for an additional feedback loop) to support bridged operation. While the patented circuit could compensate completely for the amp's source impedance and even deliver a negative output impedance, the Peavey customers didn't embrace 1k+ DF and I couldn't market it to them with a straight face (I wouldn't even try to explain negative output impedance).

While it was nice to beat the expensive competition at their own game with that meaningless spec for at least one model.  8)

JR 

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Jamin Lynch

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Re: Higher dampening factor for folded horn subs?
« Reply #17 on: January 12, 2016, 12:28:44 pm »

Not doubting what anybody is saying.

I'm wondering why a manufacture would add to the cost of a product for a feature which has no real benefit. I would think the bean counters would shut that down.

It does seem that the "higher quality" "more expensive" amplifiers tend to have a higher DF than lesser quality lower priced amps. And the higher quality higher DF amps tend to be "pro" users who would know (or should know) the difference.
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Tom Bourke

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Re: Higher dampening factor for folded horn subs?
« Reply #18 on: January 12, 2016, 12:35:52 pm »

I'm wondering why a manufacture would add to the cost of a product for a feature which has no real benefit. I would think the bean counters would shut that down.
Marketing department has as much power as the decorating comity in a church.
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John Roberts {JR}

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Re: Higher dampening factor for folded horn subs?
« Reply #19 on: January 12, 2016, 12:42:52 pm »

Not doubting what anybody is saying.

I'm wondering why a manufacture would add to the cost of a product for a feature which has no real benefit. I would think the bean counters would shut that down.
Seriously? As amplifiers become even more mature with differences between brands even smaller, the marketing department has to work that much harder to differentiate between brands. The fraction of customers who truly understand DF is small, while most approach it as a "more is always better" specification. Even pros who should know it doesn't make a difference will favor the data sheet with better numbers on paper.
Quote
It does seem that the "higher quality" "more expensive" amplifiers tend to have a higher DF than lesser quality lower priced amps. And the higher quality higher DF amps tend to be "pro" users who would know (or should know) the difference.
"More expensive" means higher expectations. Customers do not appreciate or reward being told that a lesser DF doesn't matter, even when it doesn't.

Faster Horses (cars).
Younger women.
Older whisky.
More money.
Higher DF....... ::)

JR
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Re: Higher dampening factor for folded horn subs?
« Reply #19 on: January 12, 2016, 12:42:52 pm »


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