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Help me understand about "frequency response" aspects please?

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Help me understand about "frequency response" aspects please?

Postby mikehende » Tue Dec 22, 2020 5:53 pm

Hey Sam and you other guys here, how are you all? Hope all is great.

So I have another topic here which I can certainly use help with as this will be me going deeper into trying to understand about frequency response aspects and tuning.

To dig right in, let's use "tweeters" as an example using 3 extremes.

So I am seeing 3 super tweeters with specs 35k-18k, 4k-27k and 5k-40k.

My initial questions are:

What do those specs mean in terms of the Highs you will hear, does it mean that the higher specs of 40k will give more highs than the one with 27k?

If yes to the above then let's say for example you would want to hear 40k frequency, how would you be able to achieve that on an EQ please? Thx guys.
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Re: Help me understand about "frequency response" aspects please?

Postby MOF » Tue Dec 22, 2020 6:13 pm

So I am seeing 3 super tweeters with specs 35k-18k, 4k-27k and 5k-40k.

My initial questions are:

What do those specs mean in terms of the Highs you will hear, does it mean that the higher specs of 40k will give more highs than the one with 27k?

40k will give you a higher frequency than 27k. What are you trying to achieve?

If yes to the above then let's say for example you would want to hear 40k frequency, how would you be able to achieve that on an EQ please?
Unless you are a bat you won’t be able to hear 40khz
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Re: Help me understand about "frequency response" aspects please?

Postby Hugh Robjohns » Tue Dec 22, 2020 6:18 pm

The 'standard' human hearing range is nominally 20Hz to 20,000Hz (or 20kHz).

However, only the young can actually hear the 20kHz end of things. The high-frequency roll-off reduces with age and with exposure to loud sounds (not as loud as you'd like to think, too!)

So a standard loudspeaker tweeter typically covers the range from about 2kHz up to about 25kHz. Some start higher or lower in the mid range, and some go higher or lower at the high end, but that's a fairly typical kind of spec.

Some people believe it worthwhile to reproduce 'ultrasonic' frequencies which are technically those above 20kHz, and to do that they have 'supertweeters' which are normally in addition to the standard tweeter (although some just use ultra-wideband tweeters).

Because almost all electro-acoustic drivers have a limited bandwidth, (especially if you want any appreciable power from them), super-tweeters typically cover the range from about 10kHz up to about 40kHz.

From your examples, two are actually ultra-wideband types (4k-27k, and 5k-40kHz), while the other is a traditional supertweeter (18-35k).

But while your dog or pet bat might appreciate the noises these things make -- assuming you have source material that contains any musical content at those frequencies), I am pretty confident that you wont be able to tell whats going on above 20kHz...
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Re: Help me understand about "frequency response" aspects please?

Postby mikehende » Tue Dec 22, 2020 6:26 pm

Great thanks guys.

I am simply trying to understand how frequency response works so I can apply the knowledge to my highs setup.

Ok so from the above answers I gather that it would make no sense to get a Super tweeter which lists over 20k if this is the max a human ear will be able to hear [SInce I'm not a bat :)], is this correct?

Next, would tuning. If I wanted to hear the max highs which "I would be able to hear" coming from a super tweeter, does this mean I should zero in on 20k frequency on the EQ or Digital processor first?
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Re: Help me understand about "frequency response" aspects please?

Postby Mike Stranks » Tue Dec 22, 2020 6:54 pm

Don't get too hung-up on the 20K...

As Hugh has said, one looses high-frequency perception as the years advance.

Over 20 years ago I did a simple experiment with my children... using a decent sound system I played a sweep tone and told everyone to put their hand up when they couldn't hear sound any more. (We had a dummy run so they knew what to expect.)

Hands went up linearly in reverse age order - there was even a difference between the 8 Gaer old and the 5 year old.

I'm now 70 and I don't really have anything above 11-12K... Haven't tested recently though so it could be lower!

These may help...

Image

Image

... although they do date from a time before digital recording in any form had arrived! :lol:
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Re: Help me understand about "frequency response" aspects please?

Postby mikehende » Tue Dec 22, 2020 7:31 pm

Hmnn, what a diagram thanks! From that diagram I am taking that "useable" frequency max would be around 14k? If yes then why should one purchase any super tweeter or driver with max response range over 14k?

Also those 2 sliders 16k and 20k, when I slide those upwards they increase the highs so I am confused why they should not be used unless I am not properly understanding your last post?

https://i.postimg.cc/bwqFpXqc/IMG-2244.jpg
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Re: Help me understand about "frequency response" aspects please?

Postby James Perrett » Tue Dec 22, 2020 7:31 pm

What are you playing through your system? If you are playing mp3's or similar files or streaming from the internet then there's no point in going for anything higher than 16kHz. If you are listening to the radio then the limit is 15kHz. For CD's and most other digital sources the limit is 22kHz.

The only time you will encounter more than 22kHz is when you have a digital source sampled at 96kHz or more through the whole recording chain or if you are playing high speed analogue reel to reel tapes. While vinyl can theoretically contain frequencies higher than 20kHz, it is very unlikely to have much in that range after more than a few plays - and high frequencies may have been filtered out at the mastering stage. Cassettes struggle to go beyond about 15kHz and you'll only get that level of performance with top quality tape in a well adjusted machine with extremely good heads.
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Re: Help me understand about "frequency response" aspects please?

Postby mikehende » Tue Dec 22, 2020 7:40 pm

Sorry James, seems we both posted at the same time, please see my previous post and yes I listen to mp3's.
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Re: Help me understand about "frequency response" aspects please?

Postby James Perrett » Tue Dec 22, 2020 7:53 pm

mikehende wrote:Also those 2 sliders 16k and 20k, when I slide those upwards they increase the highs so I am confused why they should not be used unless I am not properly understanding your last post?

Graphic equalisers aren't perfect and the controls have some effect on the frequencies either side of the centre frequency - especially with large boosts or cuts. The effects you are hearing at different settings of the 20k slider are probably down to the effects it is having on lower frequencies rather than there being any useful audio at 20kHz.

When the bandwidth isn't limited certain sources like cymbals and analogue synths can generate frequencies up to 30kHz or more
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Re: Help me understand about "frequency response" aspects please?

Postby mikehende » Tue Dec 22, 2020 8:10 pm

James Perrett wrote:Graphic equalisers aren't perfect and the controls have some effect on the frequencies either side of the centre frequency - especially with large boosts or cuts. The effects you are hearing at different settings of the 20k slider are probably down to the effects it is having on lower frequencies rather than there being any useful audio at 20kHz.

The above I will need to try to grasp.

Meantime, why should one purchase any super tweeter or driver with max response range over 14k?
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Re: Help me understand about "frequency response" aspects please?

Postby Hugh Robjohns » Tue Dec 22, 2020 8:22 pm

There are only two reasons.

Either the standard tweeter doesn't cover an adequate bandwidth...

...or because you're easily conned... ;)
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Re: Help me understand about "frequency response" aspects please?

Postby mikehende » Tue Dec 22, 2020 9:52 pm

Thanks. Now here's the twist. I just did an experiment with a super tweeter:

https://jblpro.com/en/products/st304

and one of my Peavey MF1-X horns with a D220Ti driver with specs:

https://www.zxpc.us/product-p/252027433908.htm

I called my 21 year old son, I told him I want him to tell me which of the large Peavey horn is giving the most and best highs when I switch between the two. After playing a few tunes he said without a doubt the "left" is more powerful and sounds much better.

Thing is, he did not know it was the tweeter playing on the left channel which I placed right next to the peavey horn and he did not notice it.

So I have to ask myself now guys is why is that one little 5" tweeter out-performing that large 3' W x 14" H horn by that much, any ideas please?
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Re: Help me understand about "frequency response" aspects please?

Postby CS70 » Tue Dec 22, 2020 9:57 pm

mikehende wrote:Meantime, why should one purchase any super tweeter or driver with max response range over 14k?

There's always the possibility that they want to build an ultrasonic weapon :lol:
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Re: Help me understand about "frequency response" aspects please?

Postby James Perrett » Wed Dec 23, 2020 2:41 am

mikehende wrote:Thanks. Now here's the twist. I just did an experiment with a super tweeter:

https://jblpro.com/en/products/st304

and one of my Peavey MF1-X horns with a D220Ti driver with specs:

https://www.zxpc.us/product-p/252027433908.htm

The Peavey horn possibly isn't well matched to the driver. A large horn like that is really better at midrange and the specs show a peak in the frequency response at 2kHz with a gradually falling response that is -5dB from the peak at 10kHz and then dropping rapidly after that. So you need to treat that as a midrange horn and add a proper high frequency horn to the system.

I used quite a bit of Peavey gear in my younger days and the HDH series were the only Peavey speakers with a vaguely decent high frequency response. The MFX sounded horrible to my ears.
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Re: Help me understand about "frequency response" aspects please?

Postby zenguitar » Wed Dec 23, 2020 4:00 am

A speaker is just a transducer, just like a microphone or guitar pick-up. It's frequency response tells you no more, and no less, what it is capable of reproducing.

Twenty plus years ago I had a motorbike capable of 150+ MPH, with brakes and handling to match. I live in the UK with a national speed limit of 60 or 70 MPH so, on paper at least, the top speed is meaningless.

But in the real world it is a very good indicator. If my motorbike can brake, accelerate, and handle at 150MPH (and trust me, from experience it could); it had plenty in hand to deal with 60-70MPH use.

You are looking at the extreme limits of a loudspeaker's performance and focusing on a number without putting that number in context.

When systems are at their lower or higher limits they don't perform very well. So in the real world you take that into account and specify components to use well within their paper specs. You don't choose the 40k speaker because it can reproduce 40k frequencies, you choose it because it can handle 20k frequencies with ease.

It's all about maintaining sensible margins and staying within the comfort zone.

Andy :beamup:
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