Max distance woofer and midrange

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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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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?
 
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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.
 
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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. :D It looks wrong, though there are some commercial speakers with the woofer at the rear for this reason.
 
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frugal-phile™
Joined 2001
Paid Member
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
 
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."
 
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frugal-phile™
Joined 2001
Paid Member
True, but I asked about audibility, are there any tests you know of?

All depends on the genetic hearing acuity, care of hearng and how well trained you are. Many people will not even notice but it will drive more than a few away (ie a segment of those are going to have choosen FR drivers because the whole question becomes a non-issue).

dave
 
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