Indiana Line speakers - help understanding some graphs

[smania]

Hi,

I'm very new to this whole "speaker business" and it's very hard for me to understand it... I need to set up a very simple 5.1 for a small 16x10 feet "cinema" room.
Here in Italy Indiana Line is a very known brand of speakers. Their line "Tesi" is usually recommended for its quality/price ratio.
I've found some measurements for their towers and "big" bookshelf speakers:

towers: https://www.indianaline.it/wp-content/uploads/2017/08/Test-Tesi-561-Audio-Review.pdf (usually € 580, I think I've found them at € 520)
speakers: https://www.indianaline.it/wp-content/uploads/2018/01/Test-Tesi-261-AudioReview-IT.pdf (usually € 300)
(their big towers: https://www.indianaline.it/wp-content/uploads/2019/09/Test-Tesi-661-Audio-Review.pdf)

I'm trying to make sense of what I think is called SPL graph (reported here):
Towers:

bookshelf:

There is no information at all in the test description about that dip (almost 10 dB?) close to 1Khz. I have no idea what I'm talking about, but reading here in the forum I understand that graph should be as flat as possible? Isn't that dip very deep?

 

[dfuller]

There is no information at all in the test description about that dip (almost 10 dB?) close to 1Khz.

Yeah - that's without a doubt a port cancellation - does this speaker have a front firing port? It probably isn't audible, but who knows.

I'm trying to make sense of what I think is called SPL graph (reported here):

So you've got here an on-axis (red) and an off axis at 45 degrees horizontal (blue) measurement. With that information, you can sorta-kinda gauge its behavior. Ideally, the off-axis should mirror the on-axis, but gradually sloping down as frequency increases. Instead what we see here is that the off axis actually peaks above the on-axis between 2-3KHz. That implies that the beam width is very wide around there, and I'd bet that's where the tweeter takes over from the woofer. That peak above on-axis implies directivity error.

Compare these measurements that Amir did of the Focal Alpha 65 Evo:

See how the sound power and early reflection graphs mirrors the on-axis? That's indicative of good directivity behavior.

 

[smania]

Yeah - that's without a doubt a port cancellation - does this speaker have a front firing port?

Yes this is the speaker:

It probably isn't audible, but who knows.

Ok, so not all dips/peaks are equal? I thought a -10 dB was going to be audible; is it because it only happens on a very short range of frequencies?

 

[dfuller]

Ok, so not all dips/peaks are equal? I thought a -10 dB was going to be audible; is it because it only happens on a very short range of frequencies?

Correct - this has to do with something called "critical bands". Generally speaking, the higher the frequency, the wider a response has to be in terms of absolute frequency to be audible at a given +/-dB value.