How much power to compression drivers?

[Balderdash1]

I'm putting together a system with EV HR9040 horns and Altec 291-16k.
I believe the drivers are rated for 40 watts per, but in surveying available
amps here at the house, I was thinking of trying an Ashly FTX-1501 on the horns.I wanted to use this amp in conjunction with another higher power FTX amp crossed over at 500hz to E-145. Both amps have XR-1 plug in crossover module that provides 500hz crossover and CD compensation for horns.

My primary concern is overpowering the Altec drivers. The FTX-1501
is rated at 185 watts per ch. into 8 ohms. Would this harm the Altec's?
Should I provide some type of driver protection?

[Allanvh5150]

Hi,
High frequency drivers being what they are wont allow you, or your ears wont allow you, to use you maximum amplifier power. because they have a higher sensitivity to the rest of your system, sometimes 20db or so, you will need to turn down you active crossover to get the correct level. In this way you will never get to see the full power of your amplifier at the driver. You can usually supply twice the recomended program power to a speaker without any problems. If your driver is rated at 40w rms the program power will be 80 watts so your amp could be 160 watts. Clean amplifier power is far more important. An overdriven smaller amplifier will kill a driver quicker in my opinion.

[Robh3606]

If you are running the compression drivers with no networks be a good idea to drop a protection cap in there. Protect them from turn on thumps and DC if the amp decides to kick the bucket. Look up the 5253/5234 network manuals they explain the whole thing. You certainly don't need that kind of power with them but as long as it's clean it should be fine.


http://www.jblproservice.com/pdf/Vin...5%20manual.pdf

Rob

[Balderdash1]

Thank you both for your responses...Rob I see you have a system that includes the E-145. I hope to build cabinets with E-145/2245 combo. Should be nice!

[david yost]

Those EV9040's are wonderful horns -- I'm sure you will like them, but you must eq them for the CD hf roll-off if you are going to use them above about 3000 Hz or so. What are you going to use for tweeters?

BTW, I have used mine with 288H drivers and 2A3 amps and have probably never demanded more than .1W during very loud crescendos. This horn/driver combo is so sensitive that in a quiet home environment you will probably hear any crossover distortion in your amp as well as hum and noise unless very lucky/careful. I strongly suggest a refined and ultra quiet SE amp -- tube or ss.

**Should have read your post more carefully -- my brain saw 299 instead of 291 and I entirely missed the CD eq feature in your crossover. If you still have the aluminum diaphragms in your 291's, you may not need tweeters.

[Balderdash1]

Thanks David. I'm really excited about using the EV's. From what I understand, I can switch out the 291 diaphragms for 288's. An improvement perhaps?

Yeah, the hardest part for me with this whole thing is crossover selection.
I want to triamp, and finding CD compensation plus slope flexibility is proving to be a challenge. I would really like to use third order slope between midbass/horn but all I can find is 24 db/oct.

For tweeter, if needed, I have 2404 from 4628b cab.....

[david yost]

BDash,

I wouldn't be in a hurry to swap diaphragms just yet. The ones you have should be Al with the pascalite surrounds that can handle a lot of power and go low. The 288 diaphragms have Al surrounds and are a little more fragile.

You could try the inexpensive stereo 3-way Behringer DCX 2496 crossover which can do 6dB - 48dB/octave crossovers as well as cd and parametric eq. 2 in - 6 out. About $250.

[jcrobso]

If you are running the compression drivers with no networks be a good idea to drop a protection cap in there. Protect them from turn on thumps and DC if the amp decides to kick the bucket. Look up the 5253/5234 network manuals they explain the whole thing. You certainly don't need that kind of power with them but as long as it's clean it should be fine.


http://www.jblproservice.com/pdf/Vin...5%20manual.pdf

Rob

About 40 years ago I blew out two 375 drivers because of dc transients when using an electronic X over. George Agusbeger called me personally and asked me what how I did this. After I explained what happened he suggested putting the caps in, I told him I would(and did). He was very nice about the whole thing, JBL fixed one for free but charged for the other one. Soon after this George wrote letters to Audio and other magazines recommending the use of DC blocking caps on the high frequency drivers when using electronic X overs. John

[readswift]

i just read they dont recommend it anymore...

http://www.hostboard.com/cgi-bin/ult...&f=3729&t=2892

"

posted May 21, 2007 10:51 PM

quote:Originally posted by bowtie427ss:
Also a capacitor in series in the HF driver path (post amplifier) with a value that begins roll off 1 octave below the intended XO frequency is an inexpensive safety device that can save much expense and headache when something goes wrong with the HF amplifier or it's incoming signal.

In Pro sound this practice is fast disappearing. Most modern amps have protection. Using a series cap will wipe out the amplifier's damping ability. This can actually in some cases cause more driver failures than not having the cap would.
With an old amp, I might still use the cap. I just wanted everyone to be aware, there are changing opinions on this, it used to be standard recommended practice.
EAW and JBL recommend no cap."

id prefer to leave it out (with digital active xo) , most i might do is a 6.8 uf MKP on the output of the digital source. Also , since my source is computer, Im going to use an automute with treshold, that runs on startup somehow,
-Please share your opinion.

[johnaec]

All your pictures just show up as red X's - you have to register at your site to see them. Much better if you just upload them directly to here.

John

[JBL 4645]

Oddly enough I was looking at the Crown power SPL calculator.

Amplifier Power Required
http://www.crownaudio.com/apps_htm/d...ct-pwr-req.htm

[Zilch]

185W is gross overkill for driving a compression driver with no passive attenuation. You're going to have to crank its gain down to virtually nothing, and then fight the noise floor. As David said above, it'll run on milliwatts.

i just read they dont recommend it anymore...

http://www.hostboard.com/cgi-bin/ult...&f=3729&t=2892

-Please share your opinion.

Opinion?

Here it is: Gratuitous threadcrap.

You cite a remark from June, 2007, which, when challenged, is substantiated with, "I'm tired tonight...."

And is then followed by an incomprehensible discussion of HF comp evidencing a fundamental lack of understanding of the concept on the part of the participants?

This, you punctuate with a bunch of broken images?

Let's have some facts to consider, please, telling us why we shouldn't opt for protecting the driver -- sum of square steradians or something. :dont-know

Rob says use a cap, Bowtie says use a cap, John says use a cap, Zilch says use a cap....

[Why am I reading this? ]

Edit: The images are header icons from the quoted Altec Forum post. They lit up here once I signed into that site and they were stored in my cache: Profile, eMail, PM, Delete, Reply with Quote.

Anybody have some more suggestions for appropriate amps to run compression drivers in an active system? T-Amp?

[Hoerninger]

"I'm tired tonight...."

Looking for facts this statement was the first one (in my humble memory).

... more suggestions for appropriate amps to run compression drivers in an active system?

Class A amp, no heat problems, no problem with noise floor and a decent sound.

I would use a capacitor anyway. CC or - thinking about Mr.Timbers last post - single rail amp. Back to the roots? Though the topology may be symmetrical if mandatory.
____________
Peter

[Rolf]

"You stupid woman!" (A farce here in Europe) It plays as you want. boing.

[Kwikas]

I know this is really, really old but I have a question around the amp power required for my 2432H CD's that are going in to my HT.......so it's very relevant to this thread.

I asked Crown for their recommendation and they said either at CTs600 or XLS1500 would be OK. That seems to me to be an awful lot of power for these drivers!!! But maybe I'm wrong.

Can I take it that a much lower power class A amp would be your recommendation? The 2432's are sitting atop dual 2226H drivers (in custom 4648A cabinets).

Thanks guys