[matevana]

Good Morning,

I recently completed a small, room friendly dipole project that I am very pleased with. I tried to incorporate many design and system philosophies that I have worked with over the years, and am always interested in making improvements. The project was also designed with a reasonable budget in mind. Some design goals included:

Identifying inexpensive 10" automotive subs as "helper woofers" that have both high excursion and high Qts
Use of the new Peerless 830987 3" wide range driver
Constructing a damped, multilayer beechwood baffle with IKEA wood stock
Using sorbothane materials for baffle isolation
Biamping with two Dayton DTA-100 Tripath Amps
Biwiring with Spakon NL4 connectors
Using F-mod low level active xo's
Using the Clarion EQS746 for EQ (case 1)
Using the Behringer DEQ2496 for EQ (case 2)
Time aligning the full range drivers

I have started to document my project at:

http://home.comcast.net/~cunundrum

To date I have spent many hours testing and modifying and would be glad to provide input. As mentioned, I am also eager to improve upon the design, so suggestions are always welcome.

Thanks!

[mcgsxr]

Any ability/interest in extending short wings off the back around the woofer, to form a U?

Should dramatically increase bass, with no larger frontage required.

[matevana]

Any ability/interest in extending short wings off the back around the woofer, to form a U?

I actually built them initially with 1/2" MDF wings, extending back about 8 inches to form a U. I quickly realized I preferred the sound w/o them. While it did add to the quantity of bass, they are not exactly lacking in that department once EQ'd actively. Also the wings seemed to detract from the full range driver, sounding somewhat tubby and constrained.

The Alpine woofer is a bit of a rare combination and seems well suited for dipole use. With a QTS of .62 (mine measured close to .70) and almost 13mm of xmax, it produces good sounding bass solo, perhaps equal in quantity to that of an 8" studio monitor in a sealed configuration, with all the benefits of dipole bass. When using the auto EQ feature of the DEQ2496, the bass is only boosted about 3dB under 100Hz and cuts around -3dB in the 125Hz to 250Hz range. I meausre in room flat response from around 70Hz up through the woofers rolloff using the RTA in the Behringer along with the measurement mic.   

[Russell Dawkins]

Thanks for posting this and the link to the details of your project.

I find the fresh approach to be very useful. Congratulations!

[planet10]

Using F-mod low level active xo's

Thanx for showing us your project... i'm a fan of FASTs.

The F-mods are not acive filters. They are PLLXOs (Passive Line Level XO). Rolling your own, with components that would never fit into those extended RCA plugs, should yield further improvement.

dave

[JohnR]

Very cool. Do you have them sitting on the floor? (They could almost be used as a desk system!)

[matevana]

Very cool. Do you have them sitting on the floor? (They could almost be used as a desk system!)

They are sitting on the floor currently. The xo frequencies make constructive use of floor bounce. I supose a desktop might offer some bounce, but the crossover points might need to be modified somewhat.

[matevana]

Thanx for showing us your project... i'm a fan of FASTs.

The F-mods are not acive filters. They are PLLXOs (Passive Line Level XO). Rolling your own, with components that would never fit into those extended RCA plugs, should yield further improvement.

dave

Good point!  I read a thread on another site about "rolling" your own inline passives. Better quality caps (often larger) might be a reasonable upgrade for me to try. I'm also experimenting with a small 2 way active xo made by Kicker (KX2) for the automotive market. It's signal to noise ratio is rated at over 110dB and uses 18dB slopes and allows you to boost the output signal quite a bit. I picked one up on eBay for 40 bucks and am currently playing with it. So far it seems pretty good.

[mcgsxr]

Cool!  How do you power the car audio Xover?  Battery?

[matevana]

Cool!  How do you power the car audio Xover?  Battery?

Hi Mark,

I use a small switching power supply (wall wart). It puts out 13.8VDC at 800ma and has more than enough clean power for the XO. It's funny but 5 years ago I would not consider using automotive components for home hi-fi. The quality seems to be getting better and better, and with the mass production capabilities of that segment (as opposed to the DIY home audio market) the prices are quite low by comparison. The Kicker KX2 crossover has impressive specs (by hi-fi standards) and I can detect no audible noise when I A/B it. The signal boost also helps attain a more proper input level for the power amps.

It's interesting to consider that a small two-way active system can consist of the KX2 crossover and the Clarion 7 band EQ for about a hundred bucks new. Add two Dayton DTA-100 tripath amps and for a total of $300 you have an impressive basic active biamp system for less than the cost of most off-the-shelf mid-fi receivers.

Ed

[Teflon]

Nice work ! - looks very nice.

Now that you've had a month or more have your listening impressions changed at all ?

[ga foo 88]

I have bought the lag an countertop to make an audio rack build.  I got a couple of questions about working with the beech counter top... Did you put an oil or other finish one the beech?  Also, do you see any problems with being able to use a round over bit on the outside edge of the baffle?