# A3 bookshelf problem



## mattsipes (Feb 24, 2011)

I'm building a small, ported bookshelf speaker with Audience A3s and need some help. They sound pretty good except around the 5K and 8K levels where the sound gets a little harsh and crowded. Any advice would be greatly appreciated, thanks!


----------



## 1Michael (Nov 2, 2006)

More info needed...
Like maybe maybe a Xover schematic, picture of the xover, etc etc etc.


----------



## mattsipes (Feb 24, 2011)

1Michael- There is no crossover, just a single A3. the cabinet is 9" X 3.5" X 5.5" internal dim. and has 1 port 1" X 3.88" and 1/2" foam behind the driver. any ideas?


----------



## 1Michael (Nov 2, 2006)

Small speakers suck:huh:


----------



## fbov (Aug 28, 2008)

I'm going to guess you built these without looking at the spec sheet, so you didn't know about the 8KHz peak, and the general rising trend in response at high freq until you started listening. It's not unusual for a single driver speaker to require some degree of filtering, even if it never crosses over. 

The peak needs a notch filter, plus a very gentle downward slope on the filter to tame the highs. The component values will depend on driver impedence, so I can't suggest anything specific unless you have measurement gear and some facility with electronic simulators. 

HAve fun,
Frank


----------



## mattsipes (Feb 24, 2011)

Frank- thanks, you're second person to suggest a notch so i'm going to give it a try. i do have REW and an SPL but am still shopping for an interface. this is all brand new to me. what would i be testing for to design the notch? finding the frequency and db of the peak? thanks again-

-Matt


----------



## fbov (Aug 28, 2008)

I'm going to point you here as it taught me what I needed to do this:
http://www.pvconsultants.com/audio/frdgroup.htm

Not all the tool links work, so you may need to search, but the tutorials are excellent. Follow the "Using FRD Tools" link and follow the tutorials showing how different designers use them. 

REW will plug directly into a Radio Shack SPL meter, and you can do some reasonably good work on bass frequencies. A little research will show that RatShack meter variability above the bass range makes it unsuitable for your needs. The calilbration curves vary too much, unit to unit. If you have a different SPL meter, research it to see how it does. 

Many DIYers use a Behringer ECM-8000 or Dayton EMM-6 with a Behringer Xenyx 802 mixer (this mic needs phantom power) as input to PC-based measurements. About $100 for both mic and mixer. 

However, to do the electrical side of the work, you also need impedence data. DC resistance measures impedence at 0Hz, not where you need your notch filter. You need to know impedence vs. frequency to predict how caps and coils will shape the frequency response. The impedence curve is shown on the spec sheet, and I'd urge you to try one of the SPLTrace tools from FRD to capture this data rather than measure it. Measurement is another $100 tool (WT3 from PE) or a simple measurement bridge fixture and some SW. 

You've actually got a very nice starting project. If you get to the point of designing circuits, there's a lot of support for Jeff Bagby's Passive Crossover Designer (PCD). Import full FR and ZMA files and you'll be able to design a circuit that both notches out any peaks and shelves the highs to flatten the response. 

Have fun,
Frank


----------

