Todd smith

Am I doing my FR charts correctly with my pb2-ultra?

I am using the autosound test cd #101. Tracks 10-98 are 1hz increment bass tracks that play for 30 sec a peice. I have all mains set to small, sub crossed at 80 and am using a B&K ref 50 as my pre/pro. When I run the freq sweep I am doing so in dolby pro logic music 7 mode which is what the pre pro defaults to when I put this disc in. I have a 7.1 system. I then take readings starting at 16hz then 20 then 25 then 30 and so on up until 90. I then use the compensation chart to compensate for the radio shack spl meter which is set to c-weighting and slow. Is this the right way to do a FR chart??

The reason I ask is if this is correct my chart is pretty bad where I would ideally like to keep this sub which is in the front corner of the room. The spot that is flattest is in the rear of the room, but the sub does not sound as impresive there and I hate having the sub in the rear of the room. I know it should not matter but it just does not feel right to me when it is in the rear of the room. Am I doing my FR charts right?

Brian Fellmeth

Yes with one reservation. If you are trying to optimize for 2 channel music, and you listen to music in stereo only, they you should be working with that mode rather than prologic 7. In other words, look at your FR with the receiver set up the way you use the receiver.





Its the room peaks in the bad location that make it sound more impressive. The room is helping the sub by amplifyinmg like a megaphone. The only problem is that the help is selective- some frequencies amplified and some attenuated. Superficially, a boomy setup seems more "impressive" but it is not musical- some deep bass jumps out of the material, other frequencies receed. What is truely impressive is a flat response where your ears get exactly what the engineer and/or musician put on the source.





It almost always is. Hence, a large volume of posts on the BFD. Do a search.

Todd smith

I have read a little bit about the BFD. Is this a cut device only?? Or can you perform some boost?

Brian Fellmeth

You can do either, but cuts are more effective. The problem with boosts is that you are just throwing more energy into the black hole that is the room null.

Todd smith

So in order to get the response completely flat I guess in my case I should put the sub in the back corner because I am not getting any nulls with the sub in that postion, just one peak which I can tame with the peq on the ultra. I was hoping to keep the sub in the front corner, but my FR chart looks like a roler coaster in that spot with a HUGE peak and a pretty big null as well. It sounds like nulls are much harder to deal with and the only real option is to move the sub to the rear since I cant move my seating postion. This is probably the best bet in my situation, dont you think? I have tried bass trapping and did not get any different results as far as my FR charts. The null and peak were still huge. Thanks for all the info.

Ryan Tsang

put it where it is the flattest (before EQ). check out a recent thread titled "I don't think my svs broke in" and see how many people prefer clean bass.

The BFD can be used both for cut and boost. Not every dip is a null, so it is ok to boost up to 7-8db. If the dip is big and boosting it doesn't reflect in the new measurements, then that's a null and you should try another spot.

As for modes on your prepro, I would do it stereo, only because I don't know what DPL or DSP modes do to BM.