WMT vs WTM??

[terry j]

most systems are woofer, mid and tweeter.

is that simply because of 'convenience', or is there a sonic reason to do so??

Am gonna help a mate soon with the setup he's built, but due to the woofers he's using (2 15's above each other) with a ten inch mid, my concern was that maybe his tweeter would be too high.

He has suggested going with the mid above the tweeter.

So, first off, is it important in any way IF the tweeter is 'too high'? and secondly, does it matter at all if we put the mid above the tweeter?

Won't know till we get there, but right now I envisage crossing the woofers to the mid at or below 200 hz, and probably cross that mid to the tweeter maybe even as low as 1200 hz or so.

Only mention that as it could very well have a bearing on the question.

[Moondog55]

Hi Terry, the top of my head answer is "put the tweeter at ear height" as thats what all the big books say to do.

I must confess that I do so, normally;;;;;;; usually.
But try this ;; take a small bookshelf; put it on a stand; listen:

Then turn it over; can you hear a difference?/
I could when I made a bookshelf for my son, the explanation is in a book somewhere.
I've got a thing about making my boxes from standard size sheets so I have plans in my head for a 3-way made WW TM to get the tweeter at 900mm and made designing the box easy just one 45 panel for the mid-range box.
Does this help??

[HK26147]

or is there a sonic reason to do so??

As frequencies get higher they projected more line of sight, with reduced output off axis. So most tweeter placement is usually on the same plane as the ears.

[simon dart]

There's a good psycoacoustic reason for doing so. HiFi is about creating an illusion. Anything your brain finds contradictory to experience or expectation helps destroy the illusion and fatigue will set in. The brain uses HF primarily in the localisation of sound.

Your hearing is very good at localising laterally (thats the way the world is, and why your ears are on the sides of your head, not on your chin and in your hair!) but you still have vertical sensitivity thanks to the shape of your outer ear. You expect a vocalist to be standing/sitting not lying on the floor. Placing the tweeter at or slightly above ear height will detract less from that illusion.

[pedroskova]

In regards to the mid being placed above the tweeter, there shouldn't be any problems- given that the mid's lowpass falls at a low enough frequency. Mission, and a few other mfg's, claim that it can be an advantage, but I don't have a link. IIRC, it has something to do with vertical lobing at the crossover point.

[sreten]

Hi, why not go WMTW ? /sreten.

[terry j]

Originally posted by Moondog55
Hi Terry, the top of my head answer is "put the tweeter at ear height" as thats what all the big books say to do.

Originally posted by HK26147

As frequencies get higher they projected more line of sight, with reduced output off axis. So most tweeter placement is usually on the same plane as the ears.

Originally posted by simon dart
Placing the tweeter at or slightly above ear height will detract less from that illusion.

yeah, that is exactly my train of thought. I forgot to mention that he has already gone ahead and built the boxes, but as I can gather in seperates. IOW the two 15's are already in a box above each other.

it was when I saw the pics that I became 'concerned' that the tweeter may be too high if placed above those 15's AND a ten inch mid.

It was as a result of my 'concern' (which I don't really know is a valid one, hence the question) that he suggested the mid above the tweeter (again,doable because of the seperate boxes) so the tweeter would be at or near the ear height.

that of course made me wonder if we would be trading one set of compromises for another.

Originally posted by pedroskova
In regards to the mid being placed above the tweeter, there shouldn't be any problems- given that the mid's lowpass falls at a low enough frequency. Mission, and a few other mfg's, claim that it can be an advantage, but I don't have a link. IIRC, it has something to do with vertical lobing at the crossover point.

I too thought x-over point may be of importance, hence my stating it above. the tweeter he has is the beyma AMT, and I see that it is suggested that it can operate as low as 1200 hz. that seems to give plenty of play room, esp when we take into account we will be using a deqx to do the x-over duties. We can use far steeper slopes than conventional, so if it is fine to run from 1200 at (say) 24 db, we are really making life easier for it with (say) 80 db slopes.

Originally posted by sreten
Hi, why not go WMTW ? /sreten.

Cause he has already gone ahead and built the boxes!

You gotta be careful of who and what you take as 'gospel'. Someone who's opinion I valued once mentioned that it was fraught with problems if you placed a mid above the tweeter. Back then let me tell you I knew way less than I do now even, so I felt it prudent to at least do a quick check and see if there were in fact any rule of thumbs that I should be aware of.

So to summarise, it seems that it is more important to keep the tweeter at ear height (my first thoughts) and any 'problems' with a mid above the tweeter can be ameliorated by having as low a x-over point as practical. If we have a x-over point of anything under 1800 then the mid should still be 'coupled' to the bass drivers even if there is a tweeter in between them?

The other alternative I suggested was to lay the box with the two 15's on it's side. That way the tweeter could still be at ear level with the mid under it, and maybe we could even get more assistance from the floor proximity to the woofers.

I think he ruled that out due to aesthetics

In any case, I don't think we need that assistance cause they are AE 15's, should be pretty capable by themselves!

cheers.

[Moondog55]

Most important "rule of thumbs"
Don't get them caught in the blade of the power saw!

[terry j]

now that I think about it, most of the three way horn type systems I've seen seem to have the tweeter below the mid horn.

I would imagine in those cases that is very much dictated by where the tweeter would be if it was above the mid!

On the flip side, I canna imagine that the tweeters would be crossed all that low, so maybe my initial concerns that having the mid above the tweeter being a problem is way off base.

[rabbitz]

Usually the mid above the tweeter is done with 1st and 3rd order crossovers to compensate for the downward tilt caused by the crossover. Vance Dickason has some good info about it and ZDP in the LDC.