Keith aka Amfibius System

[trek737]

Keith,

Sorry to hear about your amp misfortune.

I enjoyed reading your thread this morning, your system is awe inspiring! Great Job!

[Amfibius]

Originally Posted by chessman

Keith, I just re-read this thread with pleasure. I still marvel that a "non-engineer" would or could take apart and successfully modify a $60,000 speaker. Nice job!

Thanks chessman, but the reality is - I had plenty of help! As always in audio, if you ask 10 audiophiles for an opinion, you get 10 different suggestions. The only thing I did was decide who to listen to and who to politely ignore.

[Myles B. Astor]

Originally Posted by chessman

Keith, awesome story and pics. It takes balls to open, much less modify, a $60,000 speaker. I am impressed that you could look at the components and know what to do. Congrats!!

Ditto! +1

[Freestone]

What is incredible - besides the persistence and talent here - is that the manufacturer would put such a cheap driver in.

[GaryProtein]

Keith, you put a lot of impressive work into customizing your speakers. I like the lead and sand.

I'm sure your subwoofer integration is very good having an active crossover to control frequencies going to the main woofers and subwoofers.

[Amfibius]

Originally Posted by GaryProtein

I'm sure your subwoofer integration is very good having an active crossover to control frequencies going to the main woofers and subwoofers.

Uhh, well not really. It is as good as I can get it. Since that picture was taken, I have moved the subwoofers into the corners of the room. Normally this would be a recipe for disaster as it would excite room modes and produce a lumpy bass response. For me this was easy to deal with - I have bass traps and the DEQX takes care of the lumpy response. The measured frequency response is excellent - nice and flat. So is the phase response.

The problem is that I have no way of reducing group delay. For those who do not know - minimum group delay means that each wavefront launched by each driver arrives at your ears at the same time. Nobody argues that group delay is inaudible - in the most extreme setting, if your woofer is delayed by 1sec with respect to your tweeter, you will definitely hear it. The controversy is over the minimum audible group delay.

In my case, the subs are 1.5m behind the main speakers. Given the speed of sound is 343m/s, the subs are delayed by 4.4ms with respect to the main speaker. In reality, the overhead imposed by the sub crossover, amplifier, and DEQX gives me a measured group delay of 5ms.

Many people think that a 5ms delay, particularly with respect to bass frequencies, is inaudible - but I am not so sure. The DEQX allows me to adjust group delay, but it can not introduce negative group delay. I can only increase it. If I double the GD to 10ms, the difference is subtle, but audible. If I wind it up to 20ms and beyond, it is easily audible.

As GD goes up, the bass seems to be more ill-defined and boomy, which is exactly what you would expect. Imagine the sound of a drum-strike reaching your ears without the upper frequencies to give it definition. This is what excessive GD sounds like.

To give you an idea of what scale we are talking about here, the time difference between your first and second heart sound (the lub-dub) is about 200ms.

If my situation were reversed, with the main system delayed with respect to the subwoofer, I could correct it. But unfortunately my sub is delayed with respect to the main system. Granted, it is only 5ms ... but given we are all perfectionists, the 5ms does bother me a little bit Perhaps I am harping on it a bit too much, after all most audiophiles don't even bother measuring it, let alone trying to correct it.

[Jerome W]

Keith,
Your system is incredible and its history is even
more.
Wonderful !

Sent from my iPhone using A.Aficionado

Hi Keith, I just discovered your system thread which was a great read! I really admire your persistence getting your amps & Acapella's to sound the way you want. It's obviously been a fun & challenging journey. You have a fabulous looking & sounding system. I'm one of the lucky ones to have heard an earlier iteration of your system & enjoyed your company and fine eats & drinks Thanks for sharing your story with us

Kind regards,

[Amfibius]

By the way, since this thread was last updated, I have not bought any new equipment All I have done is refine the speaker positioning, refine crossover settings, refine the settings on the DEQX, and so on. The system more or less sounds as good as I can possibly make it so no more upgrades for now.

[JohnA]

Originally Posted by Amfibius

By the way, since this thread was last updated, I have not bought any new equipment All I have done is refine the speaker positioning, refine crossover settings, refine the settings on the DEQX, and so on. The system more or less sounds as good as I can possibly make it so no more upgrades for now.

MADNESS

but i do see the for now included in the end of your post, so there is hope for you yet