Low bass horns: Volvotreter v Keele, driver A v B . .

[rick57]

I intended to do horns from 75 – 400 & 400 Hz up.
Below 75 Hz an active Peerless sealed XLS.

Then I read Edgar saying if you switch from midbass horn to a box at 75 Hz, the difference was pronounced. So I started looking into an extra bass horn with flare maybe 40 Hz, using Volvotreter’s spreadsheet.

Could it be small enough it to fit the SAF?
I spent hours finding & typing dozens of Fs, Qes & VAS into Volvotreter’s spreadsheet til 2 am. I found a guitar speaker (the Jensen C12R), that due to having very high Qes (2.06), needed the smallest horn. And only USD 45! Perfect! ~

But hang on, Fs of that driver is a high 74 Hz, it’s output on a baffle is down about 15 dB by the time you reach 40 Hz – below Fs: what happens to output in a (correctly sized) horn ??

Then, I plugged some driver parameters into this formula from Keele’s “Low Frequency Horn Design Using TS Parameters”:

The bounds of resistance controlled operation of a horn = (QTS)(fS)

For the Jensen C12R = 1.88 * 74
= 139 Hz ~ way too high

So Keele’s logic appears to say - very bad choice.

What is resistance controlled operation??
Btw, Keele says a LOW Qts is desirable, both for extended high frequency operation AND for extended low frequency operation.
The greater the bandwidth that the horn must cover, the higher Fs must be and the lower Qts must be.

I have the drivers for the 75 Hz midbass horn - JBL 2202Hs, which have a very low Qts (0.17), and according to Keele will function from 8 – 313 Hz! While their Fmh (often considered conservative) is a much higher 588 Hz. I’m not too worried about the
top end of the range.

Who is right?

** What combination of driver parameters and correct formula most reliably predict a driver will work at a specified low frequency?

Thanks

[rick57]

To put it another simpler way, what is the most reliable software or spreadsheet on the web for modelling horns?

Thanks

[mwmkravchenko]

I'd download Hornresponse.

It is probably the best free horn design program available.

There is a good tutorial in the Wiki section of the forum.

In short the low Qts is what you are looking for. And if you have the drivers I would go with them. A driver can be driven below it resonance in a horn. The chamber that you will have to make to load the back of the driver will when sized correctly help it to behave.

http://www.users.bigpond.com/dmcbean/

Mark

[rick57]

I've just had a small play with Hornresp.

> It is probably the best free horn design program available.

I guess it produces FR graphs??

I would have used before it if I had been able to . . I know there is a new “Entry guide” glossary in the Wiki.

> low Qts is what you are looking for

You’re probably right, but Volvotreter’s well known spreadsheet suggests the opposite . . ?

As well as getting good results by plugging numbers into a program, I want to understand the science:
ok, a driver can be driven below it resonance in a horn, but what happens to it’s output level (in an appropriately sized horn) ??

> The chamber that you will have to make to load the back of the driver will when sized correctly help it to behave.

I have some prefab horns, presumably Hornresp can model chamber sizes.

Thanks