Dipole sub parameters questions

[A3rd.Zero]

What parameters are important in the selection of a dipole subwoofer driver?

Thanks for the help.

Milo

[Drew Eckhardt]

Sd, Xmax, aerodynamic noise (which limits usable excursion), and distortion.

On any reasonable sized baffle you're going to need equalization - so a bit more to accomodate a different Q than desired isn't a huge incremental change.

Montey Kay probably has the best measurements here http://www.mfk-projects.com

[A3rd.Zero]

ok cool. I have also heard Low Fs <35 high Qts >.5

Most drivers I have looked at don't have Sd Listed. Also Aerodynamic noise is rated in what?

Thanks again for your help.

Milo

[Drew Eckhardt]

Originally posted by A3rd.Zero
ok cool. I have also heard Low Fs <35 high Qts >.5

Most drivers I have looked at don't have Sd Listed. Also Aerodynamic noise is rated in what?

Low Fs and high Qts reduce the amount of equalization you need at low frequencies although that's not always important because excursion limited output in a dipole decreases at 18dB/octave.

Using the Orions as an example, with amps delivering 200W into 8Ohms power stops limiting you arround 80Hz. At 20Hz your output maximum output is 36dB less than at 80Hz. In spite of 12dB of dipole equalization at 20Hz and loosing 14dB to the very low Q (.2) you still have 10dB of voltage beyond what it takes to reach Xmax.

A very high (IIRC the Carver amazing dipoles had a Qts of 3) might eliminate the need for line level equalization, although that's really going to limit your woofer choice.

Aerodynamic noise comes from the basket structure and pole vent. It's not rated except by dipole people as some practical limit to driver excursion (and therefore max SPL) substantially less than Xmax. SL and Monty Kay comment on this at their web sites.

[A3rd.Zero]

Ahh, thanks, I had a feeling it wasn't so black and white. Thank you for the info!

Milo

[chops]

Originally posted by Drew Eckhardt


Low Fs and high Qts reduce the amount of equalization you need at low frequencies although that's not always important because excursion limited output in a dipole decreases at 18dB/octave.

Using the Orions as an example, with amps delivering 200W into 8Ohms power stops limiting you arround 80Hz. At 20Hz your output maximum output is 36dB less than at 80Hz. In spite of 12dB of dipole equalization at 20Hz and loosing 14dB to the very low Q (.2) you still have 10dB of voltage beyond what it takes to reach Xmax.

A very high (IIRC the Carver amazing dipoles had a Qts of 3) might eliminate the need for line level equalization, although that's really going to limit your woofer choice.

Aerodynamic noise comes from the basket structure and pole vent. It's not rated except by dipole people as some practical limit to driver excursion (and therefore max SPL) substantially less than Xmax. SL and Monty Kay comment on this at their web sites.

I still do not understand how people are going around saying that dipole subs do not reproduce any bass below 80Hz!

That is just plain non-sence!! If people would use the proper drivers and proper baffle sizes, they wouldn't be saying that!

I have proved this time and time again in my super huge long thread... My first Dipole Subwoofer....

Dipole subwoofers are quite capable of playing all the way down to even 16Hz, like mine, with plenty of output to hear and feel thoughout the house. I have never heard any type of wind noise coming from the driver baskets OR the voice coil vent on the back of the magnets. However, I am using extremely efficient 15" drivers with an Xmax of only 6mm!

Down -36dB at 20Hz from 80Hz??!!! That's funny because my subs measure perfectly flat from 90Hz down to 20Hz, and only down -3dB at 16Hz!

Oh but wait, I know why. Because I'm not using small drivers with all the wrong T/S parameters and baffles the size of shoe boxes!

Here, just in case you missed it the first time, here's my thread again......

My first Dipole Subwoofer....

And if you still missed it, you can find the link in my sig below, and in my profile.

[A3rd.Zero]

Chops,

I read Drew's post like I imagine you did at first. However, on further investigation I realize that he is saying that power is not the limiting factor before 80hz. Not that it is impossible to go below that, it just that more power isnt going to help.

with amps delivering 200W into 8Ohms power stops limiting you arround 80Hz.

you still have 10dB of voltage beyond what it takes to reach Xmax.

So power doesnt limit you down there, Xmax, and I imagine baffle and driver size is the limiter. Also he is referencing the Orion speakers only not OB's in general.

Your "super huge long thread" has been very helpful for me in terms of understanding driver requirements. However I havn't been able to find a driver with the proper perameters in 10" (the limit due to space concerns) the 10" version of your Pyles however show some promise. Thank You for your thread.

Milo

edit: I can't spell worth a damn