Selenium D250-X Midrange Driver

[BEC]

I decided to try a pair of these inexpensive drivers. Sort of surprised me how good they sound on a K-401 horn in my Cornscalas. Guess I will move on to some spectrum analyzer testing on these. Has anyone else tried them. Price is $75.00 per pair at Parts Express.

http://www.partsexpress.com/pe/pshowdetl.cfm?&DID=7&Partnumber=264-202

Bob Crites

[jwc]

Bob. You are scaring me. I have been pondering over buying these for a long time. I thought I would get laughed at for trying. I swear, by reading the specs, you would think they were an 8 ohm version of the K55.

jc

[BEC]

jc,

I had these in mind for use from 700 hz or so up to 4500 in a "small" sealed cabinet with a CT125 and a 12 inch woofer. I really did not expect to like them on a K-401 horn. I think they need to be cut back about 3db to match a K-55V better. I will do some more elaborate testing in the next few days to see if the test equipment likes them. So far, I don't hear anything bad out of them. Just a bit too loud on a crossover set up for a K-55.

Bob

[Daddy Dee]

Bob,

Very cool. Looking forward to hearing more as you do more testing.

[Guest " "]

I was looking at these as well....the specs look respectable...and the price is very attractive.

[Al Klappenberger]

Guys,

I remember looking at those. They look good, BUT--> they go up to 9000 Hz according to the specs I see on the PartSexPress listing. This means they can NOT be used with any of the "stock" Klipsch networks or there will be an overlap of the tweeter between 6000 to 9000 Hz . This is NOT a problem for my networks though. Mine roll the squawker off above 6000 Hz. The Klipsch networks let it go up assuming the K55 will poop out at 6000 Hz. where the tweeter cuts in through the tweeter filter.

Al K.

[Deang]

Yeah, well -- I think that stated upper limit response is a bit of a stretch. Mass roll off looks a lot like the K-55. I'd be more inclined to worry about what's happening at the lower end, where at 400Hz you're sitting right on top of resonance. OTOH, it's pretty much the same situation I'm in with my 2470's, and I sure don't hear anything going on that makes me feel compelled to pull the drivers.

Remember too that Bob is certainly in the mind of using his tweeters and utilizing the lower transition point.

[Al Klappenberger]

Dean,

I think your's right about the 400 Hz resonance. I think that is ok if the horn is loading it there. The K400 probably will, but I don't know about the K500 horn of the Belle. My Trachorn is good below 400, so it sould work with that driver.

Al K.

[Deang]

It's hard for me to get all worked up over the borderline stuff anymore. All of these drivers are designed for high power use in order to fill large venues. I've come to believe the suggested crossover points and slopes are specifically given with that in mind. IOWs, to offer the proper level of protection for the maximum power handling specification (at maximum power). I don't think anyone around here is going to be able to pump 150 watts through this or any driver without melting down the autoformer first. So, we cross over a little lower, and if we happen to prefer a first order filter we turn our 150w driver into a 30w one. It's enough.

[Guest " "]

well put

[DrWho]

So, we cross over a little lower, and if we happen to prefer a first order filter we turn our 150w driver into a 30w one....

...yielding an increase in FMD and THD - so not quite a free lunch.

Btw, that resonance was measured on a 600Hz horn...so there is already some loading in the measurement (at least half of what a 400Hz horn would yield). So you're looking at reducing that peak by at most one half and it's already off the chart.

[tigerwoodKhorns]

It's hard for me to get all worked up over the borderline stuff anymore. All of these drivers are designed for high power use in order to fill large venues. I've come to believe the suggested crossover points and slopes are specifically given with that in mind. IOWs, to offer the proper level of protection for the maximum power handling specification (at maximum power). I don't think anyone around here is going to be able to pump 150 watts through this or any driver without melting down the autoformer first. So, we cross over a little lower, and if we happen to prefer a first order filter we turn our 150w driver into a 30w one. It's enough.

My money is on Deaf Jeff.

[jorjen]

Dean,

What do you do to use the 117db efficient 2470 in your Khorns?

[djk]

" I think they need to be cut back about 3db to match a K-55V better"

They're 8 ohms, if you bump them down a tap they will be closer to the same level and have the same crossover point as the K-55V.

"I remember looking at those. They look good, BUT--> they go up to 9000 Hz according to the specs I see on the PartSexPress listing. This means they can NOT be used with any of the "stock" Klipsch networks or there will be an overlap of the tweeter between 6000 to 9000 Hz ."

They're 10dB down at 5Khz on a horn, there will be a hole with a Klipsch crossover, no overlap.

" Mass roll off looks a lot like the K-55"

The plane-wave (terminated tube) on an Atlas PD5-VH is +/- 2.5dB from 200hz~3Khz, the Selenium is 10dB down at 200hz, and on the top end is over 5dB down at 2.5Khz, turns the corner and is gone (22dB down at 6Khz).

(JBL) 117dB is the 1mW plane-wave measurement.

at 1W/1M on a horn with a Q=7 it will be about 108dB.

[Deang]

Dean,

What do you do to use the 117db efficient 2470 in your Khorns?

"The 117dB spec is for 0.001W on a terminated tube, not a horn. It will be about 107dB for 2.83V on a 511B horn." -- djk

[BEC]

OK,

Did some looking at the D250-X driver tonight with test equipment. On a K-400 horn, it is loaded pretty good at 300 hz. Worst second harmonic I saw was when running it at 400 hz and that harmonic (800 hz.) was about 40 db down.

Frequency response is pretty good from 300 hz to somewhere between 4 and 5 khz then it goes pretty much right on down from there.

Someone with Khorns needs to give these drivers a try. Since the output is good down to 300 hz, might just work well in a Khorn as long as you use a tweeter that can be crossed at 4500 or so.

More testing later.

Bob Crites

[Guest " "]

excellent report....it would also be intresting to get a report from someone who has AL's wooden trachorn

[jwc]

Hey Bob. Any chance you can post a picture of the plot?

jc

[BEC]

jc,

I did not do a hard copy plot last night. Just looked at it on the specturm analyzer CRT and looked at harmonics at certain frequencies. I will get around to doing some plots on various horns sometime soon, time permitting. Mostly impressed so far by the fact the driver works well as low as 300 hz, at least on the K-400 horn.

I need to test a K-55 and a D250-X and put the plots on the same paper to look at sensitivitity differences.

Bob Crites

[Deang]

"...yielding an increase in FMD and THD - so not quite a free lunch."

All things being equal, there is no free lunch. But things are not equal here, since one thing is being traded for another. If sacrifice is made to gain the thing you want -- you get a free meal.

With a first order filter, power to the driver is reduced by 75% one octave below the crossover frequency. With a second order filter the reduction is 94%. We have a driver that will take 150 watts using a 12dB/octave filter, but putting it in a speaker where it will rarely if ever see more than 30 watts. This is an 80% reduction in power to the driver across its entire frequency band. You might be right, but you could just as easily be wrong. I was actually thinking it might be a wash.

I had said, " Mass roll off looks a lot like the K-55"

djk said, "The plane-wave (terminated tube) on an Atlas PD5-VH is +/- 2.5dB from 200hz~3Khz, the Selenium is 10dB down at 200hz, and on the top end is over 5dB down at 2.5Khz, turns the corner and is gone (22dB down at 6Khz)."

O.K., yeah, I should have said it looks a little like it. I was primarily looking at the response with the horn they used, and in my mind overlaying the bass bin responses, as well as the 4500Hz tweeter section Bob is using for his tweeter (APT-50).