Speaker Placement / Height Effect on Sound

[Witterings]

Sorry ... Long post but hard to give the "full impression" in a shortened version.

I've been testing some speaker recently doing "back to backs" with a switch so I can instantly go from one set to another to see which I prefer.

Whilst I've always appreciated how close ther are to a wall, both behin and to the side can have a great effect and placing on a speaker stand helps, to test them I've put one on top of the other (bookshelf speakers) and I've been shocked at the difference in sound depending on which one is underneath as opposed to on top as they're both in exactly the same position in relation to any walls.

Initially I thought it might be that the bottom one was sitting on a full foam speaker isolation pad and the other just placed on top so I changed this and put the small isolation pads under each the corners of each of the sets of speakers and I#m getting excatly the same result.

The one on the bottom sounds rich and warm and the one on the top sounds bright, lacking in depth and basically tinny, I've then swapped the speakers over (top to bottom) and it's reversed the results.

I'm testing them on a desktop which means my ears are then level with the woofer of the speaker on the top and me made me wonder if when they design them it's done on a speaker stand assuming that the listening position will generally be higher than the speaker so the sound is slightly projected upwards.

This also made me wonder about putting speakers on shelves at higher levels and again the effect on the sound.

If anyone can help me understand what's going on and wht it may be, maybe the lower one has a bigger overall area underneath reflecting more bass, but then again speakers on a stand don't.

Just for future I'm guessing if you're comparing speakers it's best to place them side by side as opposed to one on top of the other?

 

[nopiano]

Most speakers have a specific radiation pattern, and if you’re way above or below the intended axis - often midway between tweeter and woofer - then they will sound different. Also, a speaker placed much higher up loses the floor reflection which would usually boost the bass.

Those are the main two things you’re hearing I suspect. Stereophile speaker reviews show the effect of listening off axis.

 

[Tinman1952]

Well it may be that the 'mass loading' of the lower speaker by having another speaker on top is reducing/altering cabinet resonances. I've seen a number of people putting weights on their speakers too. Again depending on the speaker design, the 'vertical displacement' if not listening exactly at tweeter height can have a significant effect on the high frequency response perceived.
As for placing speakers side by side (I've done this...) many say the 'passive' speaker will sing along with the driven one. I am sure I read somewhere that Linn would not allow any other speaker in the same room when testing speakers. 🙂

 

[Gray]

I am sure I read somewhere that Linn would not allow any other speaker in the same room when testing speakers. 🙂

I think one extremist reviewer wouldn't have a telephone in the same room 📞

 

[Tinman1952]

I think one extremist reviewer wouldn't have a telephone in the same room 📞

😂

 

[nopiano]

I think one extremist reviewer wouldn't have a telephone in the same room 📞

That might have been Ivor Tiefenbrun himself. Iirc I read that he was ‘tested’ on this this by a dealer who found IT couldn’t tell any difference. Apocryphal perhaps.

 

[nopiano]

Ah, here it is. The test was with a digital watch not a phone…

Boston Audio Society - ABX Testing article

 

[plastic penguin]

All speakers are designed to play the optimum with the tweeter around ear level, regardless of whether they are floorstanders or standmounts. There are a few exceptions, those that are designed to be fixed in the ceiling.

The only other way is if you have chuffing big drivers in a tiny box room, the perfect example is these great big speakers you can buy for cars or vans.

 

[Gray]

Ah, here it is. The test was with a digital watch not a phone…

Boston Audio Society - ABX Testing article

Yes, 'undriven transducers'.
There's no doubt that an undriven speaker, at close range to some playing at realistic levels, would vibrate in sympathy, enough to generate some (very slight) power - or be used as a mic.
As for it colouring the main sound......some shops are effectively driving 10 pairs at once