Tag Archives: Altec 604

Asheville, Walnut Cove, Biltmore Forrest and Western North Carolina Audio and Home Theater specialists present Cane Creek Audio and Paul McGowan of PS Audio, Intl.

I have diffusion on the back end of my listening room and a mixture of absorption and diffusion on the front wall, in back of my Altec 604 based loudspeakers and this works great. However, my room is large enough so I have the speakers six feet out into the room and my listening chair is about four feet from the wall in the rear of the room, so this works great, with no localization of the loudspeakers in the room, while great tonality and clarity. The side walls are all absorption and that’s been the one constant thing for me in all three of my listening rooms over the years.

Total absorption

One of my YouTube viewers writes:

“Paul, love almost all your videos. but. I think TOTAL ABSORTION behind the speakers is crucial. Reflection behind the speakers is just noise. PERIOD. WORST CASE. A glass window in the imaging space. PERIOD. Sorry.”

This is part of the old live-end vs. dead-end debate in rooms (the actual debate more centers on which end of the room to place absorptive materials). And from the way he is phrasing the question, it makes logical sense. Who wants noise?

The problems with the notion are many but chief among them is this notion that reflections are nothing but noise. In my experience, it is those reflections that are essential to achieving a live sound in the room. Properly managed with a bit of diffusion, it is those very reflections that can help bring a bit of magic to the soundstage.

That said, as with any rule of thumb, it isn’t a universal truth.

There are cases where the dead-end absorption method (or a variation of it) just might be the ticket to better sound. Imagine a smaller room where the main loudspeakers have no room behind them and cannot be pulled out from the front wall. An argument might easily be made that a bit of absorption on the front wall might sound preferable.

My preferred method of diffusion on the front wall (behind the speakers) is really only effective if there’s enough space between the rear of the speaker and the wall.

A bit of experimentation with both methods won’t ta

Asheville, Walnut Cove, Biltmore Forrest and Western North Carolina’s Audio and Home Theater specialists present Cane Creek AV and Paul McGowan – PS Audio, Intl.

I agree about this, although not many truly bad sounding loudspeakers out there in the Audiophile world these days. I have got a pair of Daedalus Ulysses and double BOW subwoofers, as well as a pair of homeade, but beautiful, loudspeakers based on the GPA Altec 604 and both sound great on theor own, but both are also in great listeneing rooms.

Room or speaker?

There seems a persistent notion that rooms need to be of a certain quality in order to take full advantage of what a speaker has to offer.

If your room isn’t good enough then investing in a wonderful pair of speakers is a waste of resources. Kind of like the idea that if you’re not a gourmet you cannot appreciate fine food.


Of course it is true our rooms play a huge role in helping and hurting our HiFi system’s performance. There can be no disputing that. Where I draw the line is in supporting the belief a room has to live up to certain standards in order to take full advantage of every nuance available.

Speakers always outperform the rooms they play in.

A notable exception might be with dipoles. Indeed, not every room can take full advantage of all that a dipole has to offer. Dipoles need space and the front wall impacts how they sound.

That said, I would still argue that even in the unfriendliest of rooms the qualities of your speaker will be appreciated way before any room difficulties stymie their performance.

When it comes to rooms vs. speakers, ignore the room and focus on the speaker.

You can always help a bad room sound good but it’s not possible to put enough lipstick on a pig of a speaker.

Asheville, Walnut Cove, Biltmore Forrest and Western North Carolina’s Audio and Home Theater specialists present Cane Creek Audio and Paul McGowan – PS Audio, Intl.

For my truly great sounding homemade Altec GPA 604 speakers, I use a small amount of EQ to tame a little rise at 2k and that’s another way to voice a loudspeaker!

The icing on the cake

Look at the frequency response curve of any loudspeaker and you’ll immediately see it is not flat. Not even close. Deviations in loudness at specific frequencies are denoted in terms like +/- 3dB (on a good day). Some active speakers boast +/- 1dB, but even that’s hardly flat.

And those measurements have little to do with the actual in-room response at one’s listening position.

When a speaker designer is faced with the reality of inevitable loudness swings of this magnitude, they can either shrug their shoulders and say that’s as good as it gets, or they can use those deviations to their advantage.

When they decide to go with the latter decision, the process they use is called voicing.

If +/- 3dB is the accepted limitation, designers who understand the art of voicing decide where those deviations are best put to use. Instead of a dip at one frequency, the overall sonic presentation might benefit from a bump in loudness instead.

The deviation range remains the same. The sound does not.

Not all designers choose the art of voicing.

For those that do, it’s the icing on the cake.

Asheville, Walnut Cove, Biltmore Forrest and Western North Carolina’s Audio and Home Theater specialists present Cane Creek AV and Paul McGowan – PS Audio, Intl.

I don’t use EQ the way Paul describes below, however I do use EQ on my home made Altec 604 GPA loudspeakers. Although I only use them in the band centered around 2k, it helps makes a great speaker sound even better. My EQ’s, which are UREI 539’s, only cut level, not add and this is actually the right way to do it!

Eq limitations

Equalization is the act of increasing or decreasing the amplitude (loudness) of specific ranges of frequencies.

The most common form of EQ was once the ubiquitous bass and treble controls found on consumer audio equipment. These knobs or sliders allowed one to reduce or increase the amounts of both frequency ranges. (in my experience they were almost always cranked up on high).

Today, a few brave souls are using EQ to help adjust low frequencies anomalies in the room—mostly with the addition of a low cost easy to use DSP product like the MiniDSP. For $100 this device can take the analog output from your preamplifier and be used to feed a separate bass amplifier in a bi-amped system. Once inserted between the preamplifier and woofer amplifier, a simple and intuitive user interface can be used to adjust the bass response of your woofer.

Any loudspeaker with separate binding posts for woofer and tweeter can enjoy the benefits of biamping and EQ control using this simple setup.

While I wouldn’t recommend trying this for anything other than a woofer, it can be helpful in smoothing out the peaks and bumps caused by room modes and standing waves.

While peaks and bumps are easy to eliminate fixing the dips and valleys caused by the room are almost always impossible to fix. That’s because the loss of bass frequencies in a room are caused by cancellation (just as peaks and bumps are caused by addition). And unfortunately, regardless of how much more loudness you pump into the system at those frequencies, the cancellations just keep doing their thing.

So, should you go down this EQ road, just be mindful the most valuable improvement you can hope for is the reduction of peak and boom, not the pickup of missing bass.

Asheville, Walnut Cove, Biltmore Forrest and Western North Carolina’s Audio and Home Theater specialists present Cane Creek AV and Paul McGowan – PS Audio, Intl.

This post is about speakers and subwoofer integration and Paul and I diverge just a bit here, although our conclusions are very similar. Just the details..

My GPA, Altec 604 based loudspeakers, use a 16″ coaxial driver and makes great bass, especially in the large 9 cu.ft cabinet it is mounted in. I also use two subwoofers in the room, each with two 12″ woofers driven by a Bryston SS amplifier, outputting about 500 watts into the Daedalus subs. Both, my main speakers and the subs are very easy to drive, so while they both play with relatively low distortion…. for a speaker…., they are both, sensitive and efficient, so they are as dynamic as a real concert.

I use my main speakers full range, and only use the DSP to set many of the subwoofer parameters, such as the low pass crossover frequency, volume, phase, crossover slopes, etc.

Unlike many, I set my sub crossover very low, at 37Hz, as opposed to the more common 50 Hz +/-.  I do this because I do not want to interfere with what my main speakers do well , which is just about everything, short  of pressurizing the listening room, which the subs do beautifully. We aren’t talking about boom boom bass, but rather exciting the room, so my pants flap and things shake, when it is in the recording. Imaging also improves this way, but if the gain on the subs is turned up too loudly, things don’t work as well. There is  a sweet spot for the subs in terms of placement and settings and it has taken a lot of experimentation on my part to get this right and I’m now pretty close.

Ménage à Trois

I got enough blowback from yesterday’s post about choosing floor standers vs. two-way stand-mounted speakers, that I think it’s important to take a slight detour in our small system building project.

A ménage à trois is a three-way between people in a romantic setting, but it fits today’s subject, the three-way.

Some are concerned about the visual clutter from floor standing boxes. Others are worried about big box colorations. But whatever drives us to prefer stands supporting tiny boxes with limited bass, there is hope: The addition of a third box, the subwoofer—forming a full range system known as a sub-sat. Sub-sats were the rage in the 70s and 80s.

If you’re set on stand mounted two-ways, yet unwilling to give up music’s foundation—bass, then sub-sats might be a good solution for you.

But there’s a problem.

The smaller the woofer in the two-way, the harder the subwoofer’s task to match it.

Subs disappear when their frequency doesn’t exceed 60Hz, and lower than that is even better. A small two-way with a 6.5″ woofer is hard pressed to move enough air to effectively deliver 60Hz into the room. To fill the gap, subs in this setup run higher frequencies and rarely match the two-way.

Here’s the rule with subs. They only work if they disappear. Whatever speaker they augment should suddenly seem to have bass.

If you can manage that and don’t mind three boxes, two stands, and the connecting cables that make it work, the sub-sat system might be just the ticket.