Holes in one of my 604 diaphragm covers?

**juniper** · March 7th, 2012, 09:13 AM

I recently put my 604's back in service after a trip to GPA with a set of their new crossovers. I was inspecting the metal diaphragm cover and noticed two slight indentations under a piece of paper backed tape. I removed the tape and it seems someone many moons ago, drilled 2 small holes in the cover for some reason. What is the best way to remedy this? epoxy, look for a new cover? Also how much would this affect the sound? Thanks in advance!!!

**Altec Best** · March 7th, 2012, 01:31 PM

Is there felt in the rear cover or does this 604 have loading caps ?

**juniper** · March 7th, 2012, 02:31 PM

Thanks Altecs best, very good point!!! If the loading caps are there, it probably wouldn't matter much.. I think GPA removed them and placed felt inside 2 service calls ago, but I will recheck, when I get my other x-overs back....... very soon...... Thanks. One thing if someone chooses to respond, my local tech says, the loading caps will make your ears bleed, my 604's dont do that at all. is this the case? and if so would the loading caps in a highly equalized system sound better than without and felt liners.

**Altec Best** · March 7th, 2012, 03:12 PM

Originally Posted by juniper

One thing if someone chooses to respond, my local tech says, the loading caps will make your ears bleed, my 604's dont do that at all. is this the case? and if so would the loading caps in a highly equalized system sound better than without and felt liners.

The loading caps were used for drivers crossed over below 1500 Hz at or near rated output. (High Volume Levels) to protect voice coils.In the home environment it really isn't needed and sounds better without them.Jeff Markwart gave me some great advice for my 604-8G's.Any of the older 604's would benefit from the EQ circuit employed in the 604-8H's Crossover. It utilizes a third order HF section, like the 8H & 8K, so it affords a steep rolloff below crossover to protect your voice coil if you decide to run without the loading caps.He measured with and without caps and there is definitely a difference in sound and for the better.If your drivers have the felt then just fill the holes with a epoxy or similar product.I personally prefer the sound of the felt liners myself.I recommend these links for the 604.

http://home.earthlink.net/~jmarkwart/id21.html

Jeff Markwart's Corner - Phase Corrected Crossovers

http://home.earthlink.net/~jmarkwart..._8Hpcwmfeq.pdf

**juniper** · March 7th, 2012, 05:08 PM

Thanks Altec Best. Great links. I truly appreciate your advice, knowledge and expertise, and you are a fine moderator to boot!

**kinomat** · March 7th, 2012, 05:49 PM

I agree with Altec Best My system is a pair of 605 8K & I did an A/B test: one with loading cap & other with felt pad. used pink noise as well as regular music sources
Vocals, Classical, Jazz,Instrumental. Also some Female listening ears...... The felt pads won!!

**RonSSS** · March 7th, 2012, 07:24 PM

It isn't clear to me exactly what item these holes are in? The rear cover is metal.
A loading cap (sometimes used as a rear cover) is plastic.
I guess I'm suprised you own these speakers, had GPA rework them and don't know if they have loading caps or not?

**Altec Best** · March 7th, 2012, 11:11 PM

Originally Posted by juniper

Thanks Altec Best. Great links. I truly appreciate your advice, knowledge and expertise, and you are a fine moderator to boot!

Your Welcome ! There are many great audio engineers here that are always willing to help you out.I have learned a lot from these guys,and I'm still learning.Especially when it comes to crossovers. Good People !!

Thank You Juniper !

**juniper** · March 7th, 2012, 11:18 PM

Originally Posted by RonSSS

It isn't clear to me exactly what item these holes are in? The rear cover is metal.
A loading cap (sometimes used as a rear cover) is plastic.
I guess I'm suprised you own these speakers, had GPA rework them and don't know if they have loading caps or not?

Ron sorry not my business, to ? the experts on matters such as this. When I speak with the boss at GPA I try to keep it very,very short. I know there are a thousand people that would like his time, energy and insight. I also know he will always do what is required and what makes sense. As far as loading caps or the removal there of, I didnt see it on any of the bills I have incured with GPA and didnt open them up to see. I thought it was fairly obvious what I was speaking about when I said "metal" diaphragm cover being like you said the internal cover is either bakelite or plastic. I think some members were able to understand......I guess I am suprised now!!!