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post #1 of 37 Old 07-31-2015, 09:48 AM - Thread Starter
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Measuring and EQ'ing the BSC out of DIY Speakers

So i built these little speakers called the Heliums and they sounded great away from the wall. Once i mounted them ON the wall the baffle step compensation that they have built into their crossover along with boundary gain boosted everything below 200hz by a bunch. So now i'm wondering what is the best way to EQ them? Do i measure at the MLP and add filters below 200hz to flatten out the speaker or do i take near field measurements (ie. mic 6" in front of them while mounted on the wall) of the speaker(s) and EQ it/them that way?

Toole says you shouldn't EQ anything above 200hz. source: youtu.be/zrpUDuUtxPM

Since I like to defy logic and authority I have tried both approaches. I used REW to measure and Equalizer APO on my laptop to eq the signal.

At the MLP (which is off axis by 15 degrees as they are mounted up high next to the TV due to WAF):
I eq'ed from 10hz to 10khz at the MLP and that sounded TERRIBLE. Bad idea. Then, I eq'ed below 200hz and it sounded MUCH better.

Nearfield:
I set up the Mic between the tweeter and the woofer, on axis, about 6" away. Since this approach "removes the room" I think it has to have value. I eq'ed below 200hz and it sounded about the same at the MLP as when i measured and eq'ed below 200hz a at the MLP. Then i eq'ed from 10hz to 10khz and it seemed this was the best sound at the MLP that i got. Should it be the best sound? If i flattened the speaker's on axis response out this way, doesn't hat mean the reflected sound in the room is also going to be better?

DropBox link to my REW file: https://www.dropbox.com/s/2rfg1f4k01...ereo.mdat?dl=0

Last edited by corradizo; 07-31-2015 at 10:37 AM.
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post #2 of 37 Old 07-31-2015, 11:13 AM
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Ideally you'd reconfigure the crossovers to remove the BSC.
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post #3 of 37 Old 07-31-2015, 11:16 AM - Thread Starter
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Quote:
Originally Posted by Bill Fitzmaurice View Post
Ideally you'd reconfigure the crossovers to remove the BSC.
Thanks Bill. I wish i knew how to do that. When I talked to Scott, the designer, he told me that doing so would require a redesign of the crossover. He didn't say no but he didn't say yes..
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post #4 of 37 Old 07-31-2015, 11:18 AM
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there are obviously various ways to go about it. toole was probably suggesting that the *room effects* not be eq'd above 200hz. eq'ing the speaker itself at any frequency is fine as would applying some broad filters to emphasize/de-emphasize the overall tone (bass/treble type thing).


bsc that is designed into a speaker cannot be eq'd out. as with all passive networks, the only way to "bring up the bass" is to reduce the sensitivity of the mids and highs. once that is done with the passive network, it can't be undone with eq--the shape of the response can obviously be changed to anything, but the efficiency, once brought down, can't be restored with eq.
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post #5 of 37 Old 07-31-2015, 11:26 AM
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In a speaker that small, BSC is well into the midrange and 200hz.
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post #6 of 37 Old 07-31-2015, 11:47 AM - Thread Starter
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I'm glad to know that eq'ing the speaker based on the near field measurement throughout the frequency range is fine. That is great news. It definitely sounded best that way at the MLP to my ears. I set REW to only cut as the bass was bloated, so it brought the bass down to match the mids and highs. Since it's a bedroom system and not needing to get anywhere near reference, I can live with the change in sensitivity. Now i need to get nuts and set rew to eq the nearfield response to +/- 1db w/out smoothing.
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post #7 of 37 Old 07-31-2015, 12:10 PM
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You can probably use some EQ to cut, but ideally you might want DSP that can do a shelf filter or something.

How wide are the speakers? What size drivers?

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post #8 of 37 Old 07-31-2015, 01:21 PM - Thread Starter
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Quote:
Originally Posted by Mfusick View Post
You can probably use some EQ to cut, but ideally you might want DSP that can do a shelf filter or something.

How wide are the speakers? What size drivers?
I set REW to only be able to do cuts, so I'm glad I got that right. It looks like EQ-APO can do shelf filters: http://sourceforge.net/p/equalizerap...n%20reference/ which is nice.

The cabs are:
300-7060 PARTS EXPRESS KNOCK-DOWN MDF 0.04 CU. FT. MICRO BOOKSHELF which are 6.5" H x 4.5" W x 5" D external.

Drivers are:
275-025 DAYTON AUDIO ND16FA-6 5/8" NEODYMIUM DOME TWEETER
290-224 DAYTON AUDIO ND91-4 3-1/2" ALUMINUM CONE FULL-RANGE DRIVER
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post #9 of 37 Old 07-31-2015, 02:05 PM
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The easiest solution might just be EQ to taste. A little midbass cut shouldn't hurt much. But a flat midrange from 200hz-2khz is a critical component of sound quality.

I am on my phone so I can't see your measurment charts.
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post #10 of 37 Old 07-31-2015, 03:11 PM
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I'd eq below 3 or 400 hz from the LP. Simple, fixes your problem, and works. Ya, the sens will be lower than required, but oh well.


In the future, pick a speaker for this application
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post #11 of 37 Old 07-31-2015, 05:02 PM - Thread Starter
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Quote:
Originally Posted by tuxedocivic View Post
I'd eq below 3 or 400 hz from the LP. Simple, fixes your problem, and works. Ya, the sens will be lower than required, but oh well.


In the future, pick a speaker for this application
Thanks Tux. Other than your in-walls (are you still rockin those BTW?), not much is available in diy/aiy that is small and on-wall. I wish their was a diysq version of the fusion4 quad4 that was just a little TM that was as shallow as can be, built for on wall. That would be superb!
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post #12 of 37 Old 07-31-2015, 05:29 PM
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Yup, still using them. I love them.

To, some designs should be done. There was chatter about mine, but honestly the interest has been very little. Not many people wanna cut holes in their walls.
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post #13 of 37 Old 07-31-2015, 05:33 PM
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Pete did you put the sub behind the couch in the room with the heliums wondering how it would sound with it.

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post #14 of 37 Old 07-31-2015, 06:42 PM
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I'm curious if the OP measured a large dip in the midrange?
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post #15 of 37 Old 08-01-2015, 10:43 AM - Thread Starter
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Quote:
Originally Posted by eng-399 View Post
Pete did you put the sub behind the couch in the room with the heliums wondering how it would sound with it.
Not yet, still need to get a new/used avr for try the bedroom or a new one for the media area and graduate one up to the bedroom. No sub out on my current pioneer all in one Stereo.
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post #16 of 37 Old 08-01-2015, 10:46 AM - Thread Starter
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Quote:
Originally Posted by augerpro View Post
I'm curious if the OP measured a large dip in the midrange?
It was pretty flat from 250hz to 10khz. The only major issue is the bloat from 200hz and below.
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post #17 of 37 Old 08-01-2015, 11:07 AM - Thread Starter
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Originally Posted by tuxedocivic View Post
Yup, still using them. I love them.

To, some designs should be done. There was chatter about mine, but honestly the interest has been very little. Not many people wanna cut holes in their walls.
I hear ya. I will need to start a campaign for shallow diy in-wall/in-wall kits! How many signatures do I need @Erich H ?
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post #18 of 37 Old 08-01-2015, 01:30 PM
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Quote:
Originally Posted by corradizo View Post
I hear ya. I will need to start a campaign for shallow diy in-wall/in-wall kits! How many signatures do I need @Erich H ?
The various Volt models are too deep for you?
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post #19 of 37 Old 08-01-2015, 02:22 PM
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in the dolby module thread , NWCgrad, wrt to volt 6's Erich also made a case for a co-ax unit a bit shallower than the volt 6.
what happened to that?

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post #20 of 37 Old 08-01-2015, 03:38 PM
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Originally Posted by Stereodude View Post
The various Volt models are too deep for you?
Where wall mounting is concerned you have to be very careful of the potential for Allison Effect cancellations. The only way to eliminate them is either flush mounting or having the cab depth less than 1/4 the baffle width, so that the baffle step frequency is lower than the Allison Effect frequency. The entire point of BSC is that it gives flat response when the speaker is far enough away from the rear wall that Allison Effect doesn't occur. If you're not placing them that far out, at least 4 feet with an 80Hz crossover, then BSC can do more harm than good.

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post #21 of 37 Old 08-01-2015, 07:33 PM - Thread Starter
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Originally Posted by Stereodude View Post
The various Volt models are too deep for you?
I've been looking into them. It seems that the volt6, 8 or even10 could work. The beta-10cx is 4" deep. Not sure how far out the CD will stick out from there though.
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post #22 of 37 Old 08-02-2015, 02:11 PM - Thread Starter
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Looks like the volt6 might work the best, I need to find out how deep it is with the CD installed.

Bill, I'm going to start googling the Allison effect. Thank you.
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post #23 of 37 Old 08-02-2015, 02:20 PM
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Allison effect is a suck out due to distance/placement boundaries. You can also Google SBIR or speaker boundary interference response. Generally farther from walls of closer to them is best. It moves the problem area.
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post #24 of 37 Old 08-02-2015, 02:28 PM
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Quote:
Originally Posted by corradizo View Post
I hear ya. I will need to start a campaign for shallow diy in-wall/in-wall kits! How many signatures do I need @Erich H ?
I recently spoke with him also TUX about a baffle
Wall kit. I'm going to do one in my theater. Perhaps not a kit but I'll design a diy made for the application.

There is a lot of acoustical advantages to in wall speakers and speakers mounted in baffle walls.

SBIR, diffraction, Allison effect, need for BSC.... Much more.

Making a big ass baffle the size of the wall changes stuff though, so most normal speakers are not designed for this niche application. There is a lack of affordable high performance options for this. I'm basically stuck DIY with my budget and desired performance level.

Some companies make in wall and application specific speakers (Procella, Triad etc) that sound great and work great. But it's rare generally speaking and almost never inexpensive.

I like inexpensive.

I'm not at all surprised @tuxedocivic has never bothers changing his speakers out, even that he's designed and has around some awesome kits, speakers and options.

The dedicated forum guys are always looking for baffle wall options and there is never really a proper solution. I'm going to do one for myself. I wouldn't mind making it a kit.
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post #25 of 37 Old 08-02-2015, 04:12 PM
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does that look about right for a full baffle step?


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post #26 of 37 Old 08-02-2015, 04:44 PM
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Depends on woofer size and baffle size
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post #27 of 37 Old 08-02-2015, 04:46 PM - Thread Starter
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It's the other way around, I'm 10db hot from 60-200hz. I'm not at my computer but my REW file is posted in the first post. It shows two measurements, one at the mlp in Stereo with the speakers on the wall and the other as a single speaker, on the wall with the mic on axis about 6" away.
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post #28 of 37 Old 08-02-2015, 05:07 PM
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Quote:
Originally Posted by Mfusick View Post
Depends on woofer size and baffle size

ah, that's right. the image would correspond to a baffle width of about 19 inches or the width of a typical 15" cab (though it gets a little tricky with imperfect point source cabs).


f3 = 380 / WB (where WB is the baffle width in feet)
http://sound.westhost.com/bafflestep.htm


Quote:
Originally Posted by corradizo View Post
It's the other way around

yeah...the baffle step is the natural dropoff. baffle step correction brings down the top end so that overall response is more or less flat away from the wall. taking a bsc speaker and putting it on the wall will increase the low end by the conjugate (inverse) of the dropoff.


eq'ing it back down a little with a shelf filter would seem to be the simplest way to fix things.

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post #29 of 37 Old 08-02-2015, 09:09 PM
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Originally Posted by corradizo View Post
I hear ya. I will need to start a campaign for shallow diy in-wall/in-wall kits! How many signatures do I need @Erich H ?
I've never been 100% certain what people are wanting for in-wall speakers. Are people looking for shallow enclosures to mount in their wall, or no enclosure other than between the studs? 100" flush mounted, or is the 3/4" or 1" thick baffle sticking out okay?

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post #30 of 37 Old 08-02-2015, 09:24 PM
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Originally Posted by Erich H View Post
I've never been 100% certain what people are wanting for in-wall speakers. Are people looking for shallow enclosures to mount in their wall, or no enclosure other than between the studs? 100" flush mounted, or is the 3/4" or 1" thick baffle sticking out okay?

seems like many of the designs are fine, but just with rejiggering the crossovers to remove bsc and perhaps offering some of the precut baffles sans ports. I'm not sure if bsc is an integral part of passive crossovers or a "sub-component" that can be removed without having other effects. @mtg90 @tuxedocivic should be able to answer that...

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