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Max distance woofer and midrange
Max distance woofer and midrange
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Old 14th March 2019, 03:15 PM   #1
Korppi is offline Korppi  Finland
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Default Max distance woofer and midrange

Hello, Lots of info here about distance between midrange and tweeter, recommending half wavelength for near field.

My question is that does this distance apply for distance between woofer and midrange as well?

I want to do a setup which allows tweeter&midrange to be ear level while sitting at the sofa, but that midrange&tweeter combo can be lifted up fastly to the ear level while listening standing up.

The 15" woofer bass box is on the floor in both circumstances.

Made a one minute drawing with Paint to the attachment.

Some info:

Listening distance: 3m up to 10m

Crossover Freq. 400Hz (Woofer/Mid)

Woofer 15" Phl 5011m (5010), Mid Phl 1130 6.5"

Thanks again!
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File Type: png distance.png (9.3 KB, 304 views)

Last edited by Korppi; 14th March 2019 at 04:03 PM.
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Old 14th March 2019, 04:59 PM   #2
rb132333 is offline rb132333  United States
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I am not sure if you have seen this site: SOUND FREQUENCY & WAVELENGTH CALCULATOR

Check it out. It provides the frequency wavelengths and has many options. 400 hz is about 34 inches. I believe the recommendation is not more than 1/4 or 1/2 wavelength. You might want to search on that.

Last edited by rb132333; 14th March 2019 at 05:03 PM. Reason: hit enter before I was ready.
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Old 14th March 2019, 07:03 PM   #3
Korppi is offline Korppi  Finland
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Been using this calculator: Wavelength


175 cm is ear level while standing, which is 20cm from center of the mid

I would need 155cm from center of the mid to the bottom

85cm height of the bass box at the moment

Half wavelength of the 400HZ is 43cm

Which equals (155cm-85cm-43cm) that i am lacking at least 27cm for keeping the rule

The only way is to break the rule or make the bassbox higher ( and lift the sofa

Cannot cross much lower , because of the mid driver, that would help a lot in this.


So lets say at the listening distance of 5 metres, will it be noticeable like it is between mid/tweeter in the higher frquencies?

Last edited by Korppi; 14th March 2019 at 07:07 PM.
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Old 14th March 2019, 07:33 PM   #4
eg92b16a is offline eg92b16a  Australia
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So if you keep the woofer to midrange centres less than 43cm you should be less than half wavelength of 400hz. Then determine what height the box needs to be to get your desired listening height. If you want quarter wavelength, then the driver spacings will need to be much closer, 21.5 cm, which won’t be possible with a 15” woofer and 6.5” midrange.

Last edited by eg92b16a; 14th March 2019 at 07:42 PM.
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Old 14th March 2019, 07:34 PM   #5
TBTL is offline TBTL  Germany
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A floor is a mirror in acoustics, so there are another woofer and midrange which appear to be below the floor. Ideally they should also be within 1/4 wavelength. Of course this is not possible in practice, so you have to choose between putting the woofer near the midrange, or putting it close to the floor near its reflected image, to avoid the floor bounce dip.

And then there is a wall behind the speaker which also acts as a mirror, so if you want to position the speakers close (~10 cm) to this wall, the woofer should be at the rear of the speaker in order to be close to its reflected image. It looks wrong, though there are some commercial speakers with the woofer at the rear for this reason.

Last edited by TBTL; 14th March 2019 at 07:42 PM.
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Old 14th March 2019, 11:05 PM   #6
Korppi is offline Korppi  Finland
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Funnily enough if crossing for example at 100Hz, half wavelength is already 172cm and there would be no problems. Same reason subwoofers can be placed on the ground i quess
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Old 15th March 2019, 01:26 AM   #7
planet10 is online now planet10  Canada
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Max distance woofer and midrange
Quote:
400 hz is about 34 inches. I believe the recommendation is not more than 1/4 or 1/2 wavelength
In an ideal world the maximum distance between drivers (C-C) should be less than a quarter wavelength at the XO frequency.

So if XO is 400 Hz you want the C-C to be less than 34/4=8.5”. Hard with a 15” woofer. But you see half and full wavelength tossed about because optimum C-C is very difficult to achieve especially once you get into tweeters.

dave
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Old 15th March 2019, 09:25 AM   #8
scottjoplin is offline scottjoplin  Wales
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Are there any audibility tests of the comb filtering due to driver spacing in the average room with stereo speakers?
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Old 15th March 2019, 03:13 PM   #9
rb132333 is offline rb132333  United States
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I found this comment from Jeff Bagby (highly respected designer) on the subject:

"The truth is, the more into the far-field we are when we listen (and most of us listen at 8-12 feet away, which is far-field) the less these rule of thumbs on driver spacing actually matter. Lobing is more of an issue when we listen at a closer distance. So, if you design the speaker to be listened to 10 feet away, then you can easily get by with wider driver spacing schemes without any real problems at all."

Last edited by rb132333; 15th March 2019 at 03:14 PM. Reason: spelling correction
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Old 15th March 2019, 05:53 PM   #10
planet10 is online now planet10  Canada
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Max distance woofer and midrange
What Jeff says is true but the real problems do not disappear they just get smaller (it is easy to do the trigonometry.

dave
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