Help - Taming the HF on GPA's 604-III

**Todd W. White** · November 1st, 2010, 06:17 PM

Hello again.

What I mean by wiggling the box is this:

If those large pieces, particularly the front baffle, aren't adequately braced, the LF energy coming off of the back of the cone will set them to vibrating. Damping the internal surfaces can get out of hand - you don't want to overdo or underdo it, but trying to stop the box from resonating by using damping material isn't going to help - it really needs that front-to-back brace for structural and acoustic reasons.

The client's ears are probably prejudiced against natural sound reproduction - he's SO used to hearing it the WRONG way that, when he hears it the way it REALLY sounds, he thinks there's something wrong with the 604. This is a common problem with people who've become acclimated to bad sound. Have him get a LIVE recording of something natural, like a symphony, a pipe organ, a choir, etc., turn ALL of his EQ's and tone controls to FLAT, and listen to it through the 604 - if the recording hasn't been processed and, therefore, is natural sounding, he'll be amazed at how real the 604's sound...especially if he then goes back and listens to the nasty Tannoy's...

**LICORNE** · November 1st, 2010, 07:39 PM

Todd is 100% right. Last night on CBC TV live from Abbey Road. George Martin said that he made a recording to sound exactly the way he heard it on the 605 . The name of that Album is The Hollies greatest hits.

Enjoy

**atilsley** · November 2nd, 2010, 04:38 AM

OK...bracing it is.

Then play with amps.

Thanks guys.

**Altec Best** · November 2nd, 2010, 05:32 AM

Originally Posted by Panomaniac

And maybe a tube amp for lower damping factor - fuller bass.

Hey Pano I always thought that if there was one problem with tube amps was that they don't sound as strong in the bass region (Shy-Weak bass output)

Is this wrong ? Is my understanding of it flawed ? Thanks !

**Panomaniac** · November 2nd, 2010, 11:29 AM

Like everything else in life - "It Depends".

Vintage style woofers like Altec with a low Qts can sound dry and thin in the bass dept if driven with modern solid state amps. Those amps are too highly damped for the already highly damped (low Q) vintage systems. A tube amp with its much higher output impedance lets the woofer "run loose" a little, providing more bass. Most of the vintage drivers and boxes were designed with this in mind.
Put a high damping factor SS amp on them and they will sound bass shy.

Our own GM has been telling folks this for years, but mostly he gets ignored.

More modern speaker designs do better with modern style solid state amps.