Home Theater Shack Forums
Epik Subwoofers manufactures world-leading high performance subwoofers for die-hard home theater and music enthusiasts who won't settle for anything less than the best.
PacParts, Inc.: Since 1969, PacParts has been supplying quality replacement parts & accessories from the most recognized manufacturers in the Consumer Electronics Industry.
GIK Acoustics: Home audio acoustics at its best... especially when you have help from the owners right here at the Shack!  Check out their very affordable acoustic panels!
Discount Merchant:  If you need a replacement bulb for your video device... look no further... save big!
ReliableHardware.com: A Reliable Source for Case, Cabinet and Acoustical Hardware!
Fi Audio: Infinitely amazing balanced high end musicality designed drivers!
SVSound: The Sound Authority in speaker and subwoofers as well as the astounding AS EQ1 Subwoofer Equalizer!
Elite Screens offers the finest in affordable projection screens.
Creative Sound Solutions: Loudspeaker kits and components for subwoofers, midwoofers, woofers and full range speakers!
Emotiva is your Home Theater Component Source for Audiophile Quality Home Theater Equipment at Factory Direct Prices
RAM Electronics: Audio, Video, Home Theater and Computer Cables.
Ultimate Home Entertainment: Providing home theater seating and accessories such as popcorn machines and signage... at very affordable prices!
Go Back   Home Theater Systems - Electronics and Forum - HomeTheaterShack > Equalization | Calibration > BFD | Electronic Equalization Devices
Room EQ WizardBFD Guide
Forgot Password?
Favorites Home Theater Links Donations Image Gallery

BFD | Electronic Equalization Devices

DSP1124p EQ Boost?

Discuss DSP1124p EQ Boost? in the Equalization | Calibration forum; DSP1124p EQ Boost? I played with REW and used it's peak detect feature to automatically calculate the filters for a DSP1124p. I noticed ...


 Reply     Post New Thread
Views: 563 - Replies: 12  
Thread Tools
Old 01-19-09, 06:00 PM   #1
Shackster
Alias: Anthony
Loc: Michigan
User: #23938
Since: Aug 2008
Posts: 36
  MichiganMan is offline  
DSP1124p EQ Boost?


I played with REW and used it's peak detect feature to automatically calculate the filters for a DSP1124p.

I noticed when applied the filters created some dips/valleys.

Would it be Ok to add filters with boost/gain to smooth out the dips as long as the boost does not exceed the original signal db?


Forum Rules Reply With Quote
Alt Advertisement
Old 01-19-09, 10:15 PM   #2
Shack Administrator
Platinum Supporter
Alias: brucek
User: #6
Since: Apr 2006
Posts: 7,188
  brucek is online now    
Re: DSP1124p EQ Boost?


Quote:
Would it be Ok to add filters with boost/gain to smooth out the dips as long as the boost does not exceed the original signal db?
Generally boosting is not advised, as dips are caused by phase cancellations, where the sound reaching the measurement point is a combination of an original direct soundwave and a reflected sound that is 180 degrees out of phase at the dip (one half wavelength). When you add a gain filter at that dip frequency, not only does the direct sound increase by the number of dB of the filter, but unfortunately the 180 degree out of phase signal also applies an equal and opposite signal to counteract. The result is that your dip is still there and you have wasted the gain you've thrown at it.

Sometimes you can add a small amount of gain and remove a dip, but if you find the dip isn't responding, don't bother.

brucek


Forum Rules Reply With Quote
Old 01-20-09, 12:46 PM   #3
Shack Administrator
Platinum Supporter
Alias: Wayne
Wayne A. Pflughaupt's Avatar
Loc: Katy, Texas
User: #8
Since: Apr 2006
Posts: 3,682
  Wayne A. Pflughaupt is offline    
Re: DSP1124p EQ Boost?


Quote:
MichiganMan wrote: View Post
I played with REW and used it's peak detect feature to automatically calculate the filters for a DSP1124p.

I noticed when applied the filters created some dips/valleys.

Would it be Ok to add filters with boost/gain to smooth out the dips as long as the boost does not exceed the original signal db?
Valleys from phase cancellations are one thing; valleys created by EQ filters are another. Basically, response shouldn't be worse after using REW's recommended filters. If so, something's wrong. I suggest posting some before and after graphs for us to look at.

Regards,
Wayne


Forum Rules Reply With Quote
Old 01-20-09, 10:58 PM   #4
Shackster
Alias: Anthony
Loc: Michigan
User: #23938
Since: Aug 2008
Posts: 36
  MichiganMan is offline  
Re: DSP1124p EQ Boost?


Gentlemen,

I played with the EQ filters offline and this is what I've come up with.

I placed two filter with boost at 20 and 74hz. The 20hz filter prevents early roll-off, and the 74 was to correct a dip.

In neither case am I boosting the corrected signal above the original sweep. I'm using one filter to correct or smooth out the effect of another filter.

I haven't actually hooked up my DSP1124p so I don't know the real world results yet. Is there anything wrong with the way I'm applying the filters in this case?



Forum Rules Reply With Quote
Old 01-21-09, 06:21 AM   #5
Shack Administrator
Platinum Supporter
Alias: brucek
User: #6
Since: Apr 2006
Posts: 7,188
  brucek is online now    
Re: DSP1124p EQ Boost?


Quote:
Is there anything wrong with the way I'm applying the filters in this case?
Filters 1 and 2 are unnecessary - one will suffice.

But that's not the bigger issue. If this is a measure of sub + mains, then you can't apply filters to the sub alone and expect the results to affect the mains signal that doesn't run through the BFD. You must first equalize the sub, paying close attention to the signal below the crossover, as the signal above the crossover will become increasingly overwhelmed by the mains signal as the frequency increases.

Once the sub is equalized, then add the mains and remeasure. Then use the subs phase control to smooth the crossover transition.

brucek


Forum Rules Reply With Quote
Old 01-21-09, 02:07 PM   #6
Shack Administrator
Platinum Supporter
Alias: Wayne
Wayne A. Pflughaupt's Avatar
Loc: Katy, Texas
User: #8
Since: Apr 2006
Posts: 3,682
  Wayne A. Pflughaupt is offline    
Re: DSP1124p EQ Boost?


Quote:
MichiganMan wrote: View Post
Is there anything wrong with the way I'm applying the filters in this case?
Actually, yes. You’re starting with your level way above the Target curve, so you’re using the EQ as a de facto gain control. Is this the level you got after calibrating for 75 dB? Either reduce the sub level, or move the Target up to ~83-84 dB before you start equalizing. You’ll see then that you won’t need more than a few filters. You might want to take a look at the first post of my minimal EQ article – you’ll find a link to it in my signature.

Regards,
Wayne


Forum Rules Reply With Quote
Old 01-21-09, 08:30 PM   #7
Shackster
Alias: Anthony
Loc: Michigan
User: #23938
Since: Aug 2008
Posts: 36
  MichiganMan is offline  
Re: DSP1124p EQ Boost?


Quote:
Wayne A. Pflughaupt wrote: View Post

Is this the level you got after calibrating for 75 dB?
Wayne,

Yes but I'm using the "main speakers" to calibrate the levels. I used a RS meter to equalize the levels for my 5.1 speakers including the sub. I think the processor broadcasts pink noise.

I then calibrated REW levels using the "main speakers" and RS meter setting to 75db C weighted.

What I notice is that I get a high level at the sub frequencies and occasionally a clipping notice. If I calibrate using the "subwoofer" I get low main levels on a full sweep and the warning/notice to increase processor levels.


Forum Rules Reply With Quote
Old 01-22-09, 01:59 AM   #8
Shack Administrator
Platinum Supporter
Alias: Wayne
Wayne A. Pflughaupt's Avatar
Loc: Katy, Texas
User: #8
Since: Apr 2006
Posts: 3,682
  Wayne A. Pflughaupt is offline    
Re: DSP1124p EQ Boost?



For taking subwoofer measurements, you should use the subwoofer itself to calibrate the levels. The calibration test signal REW generates has primarily lower frequency content that will be mostly below the crossover frequency of the main speakers. IOW, its level will be fairly low in the main speakers, so you'll have to turn the receiver's volume up to get a 75 dB reading. Naturally, when you go to measure the sub, its level will be much higher, which is why you're getting the "clipping" indicator.

Regards,
Wayne


Forum Rules Reply With Quote
Old 02-27-09, 09:17 AM   #9
Shackster
Alias: bartc
Loc: Foster City, CA
User: #30725
Since: Dec 2008
Posts: 21
  bcharlow is offline  
Re: DSP1124p EQ Boost?


Brucek,

If you can't practically (or shouldn't) smooth out a serious dip using EQ, then what can you do for that dip?

I've got my BFD doing a terrific job with the peaks and the x-over set (24 db/oct published figure) at minimum of 40Hz. Yet I've got a serious dip at about 110 Hz for a few Hz around that point. I realize that level is probably room interaction with both mains and sub and is probably a null at listening positino.

Is there any hope for curing that one dip????


Forum Rules Reply With Quote
Old 02-27-09, 01:05 PM   #10
Shack Administrator
Platinum Supporter
Alias: Wayne
Wayne A. Pflughaupt's Avatar
Loc: Katy, Texas
User: #8
Since: Apr 2006
Posts: 3,682
  Wayne A. Pflughaupt is offline    
Re: DSP1124p EQ Boost?



Well, I assume 110 Hz is above the crossover point, and the BFD is only affecting frequencies below the crossover point. So the answer is "probably not." Your only option is a variable phase control on the sub or time alignment from the receiver. However, if I read your post right and your crossover frequency is 40 Hz, even that won't help. Typically phase/time alignemt issues have the greatest detrimental effect in the octave above or below the crossover point.

Regards,
Wayne


Forum Rules Reply With Quote
Old 02-27-09, 01:07 PM   #11
Shack Administrator
Platinum Supporter
Alias: brucek
User: #6
Since: Apr 2006
Posts: 7,188
  brucek is online now    
Re: DSP1124p EQ Boost?


Quote:
then what can you do for that dip?
Move the sub, or live with the dip.... Often dips at a shared frequency are easy to remove with phasing.

brucek


Forum Rules Reply With Quote
Old 02-28-09, 09:15 AM   #12
Shackster
Alias: bartc
Loc: Foster City, CA
User: #30725
Since: Dec 2008
Posts: 21
  bcharlow is offline  
Re: DSP1124p EQ Boost?


Brucek & Wayne,

I have played with placement as far as WAF allows (my 20' ICs are more flexible than my spouse on this issue!) Unfortunately, I seem to be stuck with that dip. In fact, I think it's there in the mains too, so that's definitely a room issue.

FYI, I'm the odd man out here, as I'm not HT, but stereo for music only. So I don't need, can't afford a receiver with all the timing DSP that a modern HT receiver has. I'm using a NAD C740 receiver, strictly a 2 channel deal. My only DSP is in the BFD unit, and it will probably stay that way for a long time. My speakers are Von Schweikert VR1 monitors, which go deeper and better that way than their specs: down to 40 Hz. The sub is a cheap KLH 120W 10" model designed for entry level HT, which goes from about 28 - 120 Hz usably. I turn that down to x-over at 40 Hz (minimum allowed), and that's its best setting by test; with it's 24db/oct slope it should be delivering no more than 25db at the 110 point (by crude estimate). That's certainly below audible levels one way or the other. So the issue must be with my mains interacting with the room and those mains are not movable under the circumstances.

I cannot tell you what a sharp dip at 110Hz actually sounds like. Since I know that's in the range of many instruments and even the female voice, it could contribute to less than accurate sounding vocals for example. But that's just a surmise, not a measured fact. I'm guessing that I'm missing something I'd like if I had it....

My sub has only a 0 and 180 degree phase control. It's entirely possible that phase contributes, but if my above analysis is correct, the sub isn't the issue here really. In fact, I'm using the BFD to control, among other peaks, two large peaks from the sub at 100 and 120 Hz, so effectively I've really tuned the sub out of this equation when I think of it.


Forum Rules Reply With Quote
Old 02-28-09, 11:34 AM   #13
Shack Administrator
Platinum Supporter
Alias: Wayne
Wayne A. Pflughaupt's Avatar
Loc: Katy, Texas
User: #8
Since: Apr 2006
Posts: 3,682
  Wayne A. Pflughaupt is offline    
Re: DSP1124p EQ Boost?



Quote:
bcharlow wrote: View Post
The sub is a cheap KLH 120W 10" model designed for entry level HT, which goes from about 28 - 120 Hz usably. I turn that down to x-over at 40 Hz (minimum allowed),

I have played with placement as far as WAF allows (my 20' ICs are more flexible than my spouse on this issue!) Unfortunately, I seem to be stuck with that dip. In fact, I think it's there in the mains too, so that's definitely a room issue.
The issue is with the main speakers, not the sub, so there’s nothing you can do about it with the BFD. Of course, adjusting the mains’ placement can help (not sure from what you said if your WAF placement issues were only for the sub or beyond that); that’s your only option short of equalizing the main speakers themselves.

Quote:
I cannot tell you what a sharp dip at 110Hz actually sounds like. Since I know that's in the range of many instruments and even the female voice, it could contribute to less than accurate sounding vocals for example. But that's just a surmise, not a measured fact. I'm guessing that I'm missing something I'd like if I had it....
If it’s an ultra narrow dip, then it’s not worth worrying about. Those are typically barely audible, if at all. With program material there is plenty of other information from harmonics, overtones etc. that will essentially mask it.

Quote:
In fact, I'm using the BFD to control, among other peaks, two large peaks from the sub at 100 and 120 Hz, so effectively I've really tuned the sub out of this equation when I think of it.
Hmm. I have to wonder how well the crossover on this sub works. If it’s really 24 dB/octave, and was set for 40 Hz, a spike in response at 100 or 120 Hz would have to be something like 30-40 dB in order to be an audible or measurable issue. Regardless, 100 Hz and 120 Hz are close enough to 110 Hz. You might try letting one or the other of those peaks come back through enough to reduce the 110 Hz dip.

Regards,
Wayne


Forum Rules Reply With Quote
 Reply     Post New Thread

« Home Theater Shack > Equalization | Calibration > BFD | Electronic Equalization Devices »

« Previous Thread   Next Thread »

Bookmarks

Tags
boost?, dsp1124p
Thread Tools

Posting Rules
You may not post new threads... You may not post replies... You may not post attachments... You may not edit your posts

BB code is On... Smilies are On... [IMG] code is On... HTML is not allowed!




Parts Express: The #1 Internet source for all your DIY and electronics needs!

Ultimate Home Entertainment

This site is best viewed with a screen resolution of 1280 x 1024 or higher!

All times are GMT -5. The time now is 03:58 PM.



Powered by vBulletin
Copyright ©2000 - 2009, Jelsoft Enterprises Ltd.
Vendor Tools vBulletin Plugins by Drive Thru Online, Inc.

Copyright ©2006 - 2009, Home Theater Shack, LLC.
John Mulcahy and Sonnie Parker - ALL RIGHTS RESERVED!



Projector Screens   AV Carts   Lectern   WhiteBoards   Audio Video   HDMI Cables   Multimedia   AV Blog
Massage Chairs   Wall Fountains   Bath Vanities   Electric Fireplaces   Bunk Beds
Dish Network     Dish Network deals




Sponsor/Vendor Ad Rates

Search Engine Friendly URLs by vBSEO 3.3.0

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331