novice open baffle line array question

[Chris8sirhC]

Recently i bought 42 of the parts express 4'' full range drivers they have on sale for .80 cents or something like that.
Since that driver has a nasty spike at 7khz, would doing something like this at least partially cancel out that peak?
http://f2.pg.photos.yahoo.com/ph/chr...&.dnm=3c54.jpg
where a=4.9 cm (equivalent to 7khz) and x is some undetermined length.
maby im completely off base here, its just a thought.

[leadbelly]

The peak is 9 dB....that's HUGE. Playing around with the baffle won't even get you close. You need to look at things like coating the driver with Damar or Puzzlecoat, adding a passive notch filter, etc.

[captpeterchan]

Hello. I am so glad to see that I wasn't the only one lured in by those 4 inch Pioneer drivers.
This is my first speaker construction in 25 years. I am designing an open baffle line of 16 speakers each side. Add a pair of Fountek JP3 ribbons for the highs and an old Janis subwoofer for the bottom end.
The Pioneers are damped by sticking 2 sided tape inside the metal frames. The cones are lightly doped with Dammar. This smoothes the upper midrange and treble. Luckily, the 7k spike seems to disappear a little off axis so I am positioning the speaker faces parallel to the rear wall. More difficult to fix is the 6 db wavelength-equals-cone-circumference trough at 1400 hz. Does anyone have more clever idea than notch filing?
Unless you build a curved array, you will likely find combing above 3400 hz objectionable. It's not just the drooping highs, I find it de-focuses the imaging unless you filter out the top end of the array.
I hope this helpful. If you haven't already discovered James Griffin's Practical Guide to Line Arrays, I recommend reading it.

Thanks, captpeterchan

[Svante]

You might want to experiment with the (open) baffle placement using the Edge. Remember large arrays are sensitive to listening distance. If there is a single peak at 7kHz I'd notch it with a passive parallel LCR-circuit.

[sreten]

Originally posted by Chris8sirhC
[Bwhere a=4.9 cm (equivalent to 7khz) and x is some undetermined length.
maby im completely off base here, its just a thought. [/B]

Using a = 5cm will give you a very high (siily high) baffle roll-off.

sreten.

[Svante]

Originally posted by sreten


Using a = 5cm will give you a very high (siily high) baffle roll-off.

sreten.

Really? When I try to simulate this, the distance to the edge does *not* seem to be terribly important to the roll-off frequency. Then again I wrote the simulation software myself, but I think it is OK. It appears to me that the baffle width is the most important.

...or am I missing something here?

The green curve has the driver array centered on the baffle, the red has it 5 cm from the edge.

[chipco3434]

I built a couple of open baffle line arrays last month. http://www.diyaudio.com/forums/showt...688#post337688 In fact, I'm on to building another set as we speak. The second set will use a couple of Dayton ribbon tweeters per cabinet. I will confess to being a new array fan (until I build my first horn).

I guess the reason I jumped in on this thread is to say that you should just go ahead and build 'em. From a risk/reward standpoint, you are wagering a sheet of 3/4" mdf. Low side is 30 bucks, high side (veneer) is a C-note. Let's face it, the drivers were below scrapyard prices when we bought them. Maybe you even have some caps 'n coils to play with the x-over. On my first set I capped the tweeters and haven't looked back yet. On the second set, I will invest in some coils and tune them up a little.

I am no audiophile, but I like to listen to music, and sometimes I like to listen to loud music. These things are like getting kicked in the chest. So, my own impression is that they sound great. I have had the opportunity to A-B-C them with the Klipsch and JBL's in the picture. The arrays clearly need some bass but they are my clear preference.

Step away from the PC and pick up a router.

[captpeterchan]

I've already tossed in my two cents of ideas for this particular thread. I just wanted to thank svante for introducing The Edge. In a couple of hours, I had some baffle dimensions for the open baffle line array that I'm working on. Slim trapazoids --- of course??!!! Got some good graphs for the ribbon tweeter and for the 16 Pioneer woofers. Will build and listen before I start playing with compensation. Will be very happy to be no more than 6 db down at 100 hz. Couldn't find a way to just drop 7k hz. Again, thank you svante. This is why I joined up yesterday.

captpeterchan

[Chris8sirhC]

I actually built them 2 weeks or so ago, i was planning on putting them in a box, then i realized i didnt have enough mdf on hand, so i saw this sheet of 1/4'' hdf lying there... so in about 3 hours i had the left speaker finished. I used what mdf i had for a rear brace to keep the thing from faling over or bending. I must admit, for $30 they sure sound great.

[Svante]

Originally posted by captpeterchan
I just wanted to thank svante for introducing The Edge.

Thx