yet ANOTHER PE 269-570 line array thread

[MEXXX]

Well, I know this is like 500th thread of this kind, but I have my own questions that need answers ( please <3 ).

I bought a case of the PE 269-570 drivers and plan on building either a 12 or 16 driver OB line array.

The only question I have as far as the baffle design goes is, should I go with a flat baffle or semi-concave using a 3 piece baffle with a slightly forward angled top and bottom. I know they both have their pros and cons, but which has the lesser con ?

I plan on using two PE 270-102 bullet horn tweeters in series to get 8ohms and a combined efficiency of 96db 1w/1m, which is very close to the arrays combined efficiency of 96.51db for 12 and 97.76db for 16 . Will this work ok, and where should they be mounted on the baffle?

My biggest hang-up is the crossover. I would like to cross at around 5khz and I'm confused about the crossover design for this. Should I design the XO with the drivers impedance rise at that frequency in mind, use a zobel, or not worry about either and use the actual resistance of the whole line? Also, If I use just 12 drivers will combining the 5.62 ohm impedance of the array with the 8 ohms of the tweeters pose any problems, and if so would a resistor of appropriate value in series fix this?

I'm not too familiar with the pros and cons of all the XO topologies out there, so any suggestions are greatly appreciated.

Sorry if my questions sound newbish but, I am...


TIA,

MEXXX

[Sherman]

I think I can answer a couple of your questions based on my experience with these drivers. But the one about the concave shape I can't help with as I've haven't done one like that (yet ).

First let me try to answer the crossover question (again this is based on my own experience and others will have different ideas). I have tried a few different crossovers with these drivers and a couple of different tweeters. No matter which tweeter I chose it seemed I got the best sound from a simple high-pass filter consisting of one capacitor. Depending on the tweeter the value of the cap can vary a bit but I've gotten good results with a 1uF. XO with that is between 10K and 11K Hz (IIRC). The PE drivers are operated full range (no low pass in this setup).

Next, combining the impedences shouldn't be a problem even with a simple high-pass filter. The impedance of the PE drivers goes up rather dramatically above 6 or 7K Hz based on memory. If you XO at that freq or above the combined impedances when signal is being passed to the tweeters should still be OK.

I'm using a six driver setup with my tube amp (and testing a new two-way I just finished yesterday) and haven't had any amp stability issues. I've also used the same speakers with my gainclone again without any stability issues.

If you do a "real" XO with low-pass and high-pass you should still be OK if you design each section for 8 ohms (both the array and the XO).

Keep us posted on your progress. I'd really like to hear the results of your concave baffle design.

[MEXXX]

Thanks for the response Sherman. Running full range with a tweeter to take over were the 4's leave off would be great. My biggest concern is the "nasty 7khz peak" that everyone talks about for these drivers.

Since you have some hands on experience with these drivers, whats your opinion about this "nasty peak" ?

[robertwb70]

I've been thinking of ordering some of these to play with-how do they sound? is anyone using power tapering?

I was thinking 20 per side-only thing is shipping cost more than the drivers...but that's not so bad

[MEXXX]

My drivers are in the mail and I think it was well worth the $15.01 shipping, even though a whole case of drivers only came to $15.68 .

I don't plan on doing power tapering because of the limited power handling of these drivers.

[Sherman]

Originally posted by MEXXX
... My biggest concern is the "nasty 7khz peak" that everyone talks about for these drivers.

Since you have some hands on experience with these drivers, whats your opinion about this "nasty peak" ?

I'm no expert speaker designer but I think that spike has been a little overstated. I'm not saying that it isn't there, it clearly is in the response charts it just doesn't loom as large when the drivers are used in a speaker system.

My main advice would be to build the speakers and just use a high-pass cap for the tweeter(s) and listen to it. If the peak is noticeable to you (or you just want to tame it for philosophical reasons) after listening then go for it. All you will be out is the couple bucks for the high-pass caps which you can probably still use somewhere.

Hey, these things are 49 cents, keep your expectations in line with the expense and you'll end up being a happy camper!

[Sherman]

Originally posted by robertwb70
...how do they sound? is anyone using power tapering?

...shipping cost more than the drivers...but that's not so bad

Honestly the are a very sweet sounding little driver. Used in multiple driver systems they can be both detailed and loud. Bass response is a little limited if you stick to operating them only above their Fs.

I've designed two systems that operate them below their resonate frequency and they are capable of delivering deeper bass with a properly designed enclosure. I don't think it could be called "detailed" but then again they are only 4" drivers.

[johninCR]

I can only address 2 things, the tweeters and the baffle shape.

Those tweeters aren't going to keep up with your array because you'll have a line array for the mids and a point source for the highs. The array gets quieter at a rate of 3db per doubling distance vs a point source at 6db. If you cross over that low you need an array of tweets as well. I use only a single super tweeter with a 103db efficiency, but the mids I use are pretty flat up to over 10khz, so a single point source tweeter with an Lpad to adjust and the 4"ers running full range works fine for me.

Regarding concave vs flat baffle- The decision should depend on how you listen. If you want to have a focused array that only sound good in the sweet spot which is small both in distance as well as vertically and horizontally AND optimum imaging is your goal, then go with concave. For a big tall soundstage, like you are front row of a concert (I've never heard great imaging at a concert), then a flat baffle is the way to go and you aren't chained to a single fixed listening position.

For a concave array, I wouldn't go with more than 3 drivers per flat section unless your listening position is outside of 12 ft or so. The idea of a concave baffle is to get equal distances from each driver to your ears. My friend Dmitri tried both a smooth curve and a 3 driver per section concave and said that with the smooth curve it was too precise and "you had to lock your head in a vice" to get the perfect image.

My next project will an adjustable baffle dipole array, so I can adjust the baffle to suit listening position and go all the way flat for parties, etc. The best of both worlds.

[MEXXX]

Thanks for your input johninCR.

So if I decide to XO at around 5khz, your suggesting that I use an array of less sensitive tweeters with a combined efficiency that is equal to, or greater than the array of 4's ?

I hope to experiment with coating the drivers and damping the baskets to see it I can make them acceptable for full range. If I can, I will probably do as you have and use one super tweeter crossed over fairly high.

I really can't decide how I want the baffle. I don't want to be limited to a small sweet spot, but I don't want the array to be totally void of imaging either.

Do you think slightly curving the baffle but not going overboard would be better than a totally flat one?

I know I probably can't "have my cake and eat it too" in this situation, but I would really like to try .

[johninCR]

Originally posted by MEXXX
Thanks for your input johninCR.

So if I decide to XO at around 5khz, your suggesting that I use an array of less sensitive tweeters with a combined efficiency that is equal to, or greater than the array of 4's ?

According to the PE FR plot that driver goes well above 10khz, so I'd try to get rid of the peak at 7khz another way and let them go full range. That will be easier, cheaper and less problematic in the long run.

I hope to experiment with coating the drivers and damping the baskets to see it I can make them acceptable for full range. If I can, I will probably do as you have and use one super tweeter crossed over fairly high.

Any coating will cost you in HF response

I really can't decide how I want the baffle. I don't want to be limited to a small sweet spot, but I don't want the array to be totally void of imaging either.

Do you think slightly curving the baffle but not going overboard would be better than a totally flat one?

That might work. You can always experiment with it on cardboard first. Keep in mind that imaging isn't totally lost with a flat baffle. It's just not as precise as a single driver can be and is distorted in terms of size. The most extreme example I've noticed is that a flat array makes the image Barry White's head to be 3-4ft in diameter.

I know I probably can't "have my cake and eat it too" in this situation, but I would really like to try .

If you can figure out a way to use the driver's full range, you are pretty much guaranteed success and whatever you can do to take the SQ to a higher level will just make it better. One of my favorite things about OB is that you can tweak and test as you go without taking everything apart.