SP-1.7 Crossover Frequency

jethro · « **on:** 22 Jul 2003, 11:49 pm »

jamestanner,

In our previous discussions, there was some talk that a software change was in the works on the SP-1.7 to provide a lower crossover frequency - 25 Hz I believe. Did this software change take place ?

Thanks.

James Tanner · « **Reply #1 on:** 23 Jul 2003, 04:53 pm »

Quote from: jethro

jamestanner,

In our previous discussions, there was some talk that a software change was in the works on the SP-1.7 to provide a lower crossover frequency - 25 Hz I believe. Did this software change take place ?

Thanks.

Hi,

Yes the new oftware offers 25- 220 Hz.

james

ec · « **Reply #2 on:** 25 Jul 2003, 01:45 am »

Quote from: James Tanner

Quote from: jethro
jamestanner,

In our previous discussions, there was some talk that a software change was in the works on the SP-1.7 to provide a lower crossover frequency - 25 Hz I believe. Did this software change take place ?

Thanks.

Hi,

Yes the new oftware offers 25- 220 Hz.

james

Is this S/W user installable or does the SP 1.7 have to go back to Bryston?

James Tanner · « **Reply #3 on:** 25 Jul 2003, 10:57 am »

The sofware is an eprome which the customer or dealer can install.

james

Quote from: ec

Quote from: James Tanner
Quote from: jethro
jamestanner,

In our previous discussions, there was some talk that a software change was in the works on the SP-1.7 to provide a lower crossover frequency - 25 Hz I believe. Did this software change take place ?

Thanks.

Hi,

Yes the new oftware offers 25- 220 Hz.

james

Is this S/W user installable or does the SP 1.7 have to go back to Bryston?

ec · « **Reply #4 on:** 25 Jul 2003, 01:31 pm »

James,

Thanks for the speedy response. I will call Bryston support in the next few weeks to make the appropriate arrangements.

Quote from: James Tanner

The sofware is an eprome which the customer or dealer can install.

james

Quote from: ec
Quote from: James Tanner
Quote from: jethro
jamestanner,

In our previous discussions, there was some talk that a software change was in the works on the SP-1.7 to provide a lower crossover frequency - 25 Hz I believe. Did this software change take place ?

Thanks.

Hi,

Yes the new oftware offers 25- 220 Hz.

james

Is this S/W user installable or does the SP 1.7 have to go back to Bryston?

theborg · « **Reply #5 on:** 25 Jul 2003, 01:36 pm »

Guys, there is a "Post Reply" link at the bottom of the page. It really isn't necessary to quote all four previous posts...

ec · « **Reply #6 on:** 26 Jul 2003, 01:20 am »

Found it! Most appreciated. Thanks

Thunder · « **Reply #7 on:** 28 Jul 2003, 01:11 am »

[/quote]Hi

Yes the new oftware offers 25- 220 Hz.

james[/quote]

James & EC,
When is it beneficial to use such a low crossover? It is my understanding that you are supposed to crossover at double the frequency response of what your mains can in your room, at -3db? In my case, with my PMC IB1's, I have the crossover set at 60hz. I would appreciate your thoughts, as I am still ramping up my knowledge in this area.

Scott

ec · « **Reply #8 on:** 28 Jul 2003, 02:51 am »

I was never a really big advocate of the THX 80 hz x-over. My TB2's can only go down to 40 hz (not sure at what db as PMC doesn't publish this). I find that crossing them over at 60 hz (the lowest setting currently) gives me "fuller" bass and this may sound stupid or impossible but more directional bass. I seem to pickup the location of the mid to high bass cues better. I had started a thread at the AVS forum where I wanted to go full range (down to 20 hz or close to it) and skip the sub. I was looking at the FB1's at that time. I ended up with the TB2-and kept the Mirage BPS-400 sub. At least with the x-over going down to 25 hz it will give me more flexibility to experiment.

James Tanner · « **Reply #9 on:** 28 Jul 2003, 02:53 am »

If you want to crossover at the point the studios use for the .1 channel then it is 120 Hz. The recommended setting if all speakers are large.
If L/R speakers are small then recommended is 80Hz.
The ability to crossover lower has an advantage in terms of integrating the mains with the sub and some peole like to run their L/R speakers as low as possible before the sub cuts in.

james

nicolasb · « **Reply #10 on:** 28 Jul 2003, 10:34 am »

Is it the same with the SP1.7 as it is with many other processors, that if you set the cross-over frequency to (say) 60Hz and watch something in 5.1 or 6.1, that you lose everything above 60Hz in the LFE channel?

James Tanner · « **Reply #11 on:** 28 Jul 2003, 12:27 pm »

Hi nicolasb,

Yes - true because you are limiting the .1 channel frequency response. That is why if you can you should use the Full settings on your left and right speakers because then the .1 channel will be identical to the studio mix.

nicolasb · « **Reply #12 on:** 28 Jul 2003, 01:09 pm »

I've never quite figured this one out. I know that what happens is basically this:

1) Mix sound from all "small" channels plus the LFE channel together.
2) Apply a low-pass filter at the cross-over frequency.
3) Send result to subwoofer.

But of course that means that everything in the LFE channel above the cross-over frequency is lost. I've never really understood why you can't do it in a different order, i.e.

1) Mix all the "small" channels.
2) Apply low-pass filter.
3) NOW mix in the full-range LFE channel.
4) Send the mix to the subwoofer.

If you did it this way round then you would end up with exactly the same redirected bass, but the full range LFE signal. Why isn't this possible?

James Tanner · « **Reply #13 on:** 28 Jul 2003, 03:59 pm »

The coding you are asking for would be done at the chip manufacturing end rather than the software end.

james

nicolasb · « **Reply #14 on:** 28 Jul 2003, 04:26 pm »

Are DSPs really as hard-wired as that? Hm.

Well, okay, but why isn't anyone bugging the chip manufacturers to do it differently?

I guess that's a more or less rhetorical question, and I'm sure there is a terribly good reason why it's done the way it's done, but I'd still like to know what it is.....

nicolasb · « **Reply #15 on:** 28 Jul 2003, 04:30 pm »

Oh, and:

Quote

That is why if you can you should use the Full settings on your left and right speakers because then the .1 channel will be identical to the studio mix.

I wasn't sure what you meant by "left and right". Presumably it's the case that you chop the top off the LFE channel if there are any "small" speakers and cross-over is <120Hz, it isn't just the fronts?

James Tanner · « **Reply #16 on:** 28 Jul 2003, 04:37 pm »

Hi nicolash,

In the recording studio the LCR's are always full range and usually the rears as well - so the .1 channel is used only for effect and up to 120Hz.
Bass management as we know and love it was offered because most consumers do not have speakers powerful enough to handle the dynamic range of a studio recording.

james