Nube questions tweeter selection and cabinet shapes

[late boomer]

Hi,
First post!
Q1: Some documents on tweeters have a recommended crossover frequency posted. Example 3k.
Can I crossover below this recommended frequency as long as I'm clear of fs?
The tweeter I'm considering is the TB 28-1177SB.
Crossover no lower than 2.5k.
Q2:Cabinet shapes referencing Loud Speaker Design Cookbook 7th.
Cabinets with beveled baffles in chapter 5.
Is the effect in question relating to interior shape and sound cancelations inside the box? ( box, cylinder, sphere, pyramid etc)
i.e. Can I install wedges and get the same result while maintaining a square exterior?

My first project is 7 X two way systems for 7.1 HT. Sealed.
The woofers should perform well up to 4K but I am aware of off axis roll off at the upper frequencies.

Thanks for your assistance.

[nickf]

1 besides keeping well clear of fs the manufacturers recommended crossover frequency may also take displacement limited output into account. Some tweeters simply don't have the linear excursion to produce much volume at lower frequencies. I personally try to stick to within the manufacturers recommendations.

2 Although it isn't that clear from the first few paragraphs of that chapter I am certain Vance D is referring to the outer shape of the speaker. Standing waves inside the box can be addressed with damping materials. "The edge" software can be used to indicate the effect of a baffle shape. My own experience is that rectangular is ok as long as the tweeter is a different distance from every edge of the baffle. and even if that mistake is made the speaker can be very enjoyable.

Enjoy your speaker building!
Nick

[late boomer]

Thanks Nick,

Here, https://www.madisound.com/store/prod...oducts_id=8799, they post F Response 775-25K Hz, Fs at 775 Hz and post recomended XO at 3Khz.
Some vendors post the lowest F of the response range as the lowest possible XO frequency.
I want to do this right.
If not the lowest F of the range and not Fs, then is there a rule of thumb or more scientific means of calculating the XO frequency?
A "recommended xo frequency" is not always posted.

I'll keep my tweeter mount at unequal distances from cabinet edges.

Thanks again,

Hugh

[kbgl]

Originally Posted by late boomer

Thanks Nick,

Here, https://www.madisound.com/store/prod...oducts_id=8799, they post F Response 775-25K Hz, Fs at 775 Hz and post recomended XO at 3Khz.
Some vendors post the lowest F of the response range as the lowest possible XO frequency.
I want to do this right.
If not the lowest F of the range and not Fs, then is there a rule of thumb or more scientific means of calculating the XO frequency?
A "recommended xo frequency" is not always posted.

I'll keep my tweeter mount at unequal distances from cabinet edges.

Thanks again,

Hugh

The higher the x-over frequency, the louder you can play it. If you never intend to play a speaker loud, then you can sometimes get away with a lower x-over point, or slope. It can be risky though. I had my thumb on the wrong button of my remote one time. I tried to turn the music down, but it kept going up instead. Stuff happens! Rounding the outside edges of the box will smooth the tweeters response. I like large roundovers, but I have yet to find a good way to make them.

[phivates]

Us late boomers have run out of time to do it right. We have to just do it, Phil Knight notwithstanding. This forum shows plainly there's no single right/best/One way to do it.

[late boomer]

Good,

This confirms my understanding that many rules of design can be deviated.
Or, just do it!

My prototype box happens to "just" fit the mid woofer on the narow face, typical of the "new" box , driver orientation.
There is little baffle to the immediate left or right of the driver its self.
Is this a bad thing?
ie: There is no room to do a roll over for the sake of the mid woofer its self.
I could roll over the top of the box for sake of the tweeter.

If there was a right way, all speakers would follow the same formula.
Judging by the wild variety of speaker designs, almost anything goes.

[late boomer]

BTW, what radius makes a "large" round over?
Exceeding the largest router bits I presume.

[Norris Wilson]

Hi Boomer,

There are several options here if you do not mind using MDF.

Look at the quarter rounds under millwork.

I have not used any of these corners rounds. But, would be interested trying them in the future.

Curved Plywood, Dieboards, Drumshells Aitwood Home

[Borus]

late-boomer
The rule of thumb would be Fs + 2 octaves if xover is 6Db/O w/o Ferroflud
that's 3100Hz for your tweet but you have Ferroflud so you can fuge the rule.
Two octaves is still a good idea but at 12Db you could get down to 2500Hz with out too much trouble. If the woofers are good to 4KHz why even worry about 2.5K. If for a 7.1 you will want constrained dispersion. No?

[late boomer]

Thanks Borus,

I like the numbers.
As for the 7.1 constrained dispersion...
I'll have to think it over.

I had bought a set of retail speakers prior to Christmas.
WTW config.
They had a nasty dead zone which has me cautious about dispersion although I think the real problem was phasing / interference and a poor tweeter match to boot. (low spl)
They were returned.

I'm open to hear the case for constrained dispersion.