Looks like we have an Altec convert.....

**analog addict** · October 19th, 2013, 08:37 PM

I suppose it would help if we could bolt the damm thing on straight....

Nothing like paying homage to the Mighty Duplex!

I'll let Pano post his impressions if he feels like it. Otherwise, we left late and Dennis was still sitting there listening to them.....

**mah** · October 20th, 2013, 01:05 AM

It looks top-heavy. Consider the possibility of a child pulling it over, upon himself. This was a problem with some large screen TVs.

I wish you well in this venture.

**analog addict** · October 20th, 2013, 01:14 AM

Appreciate the advice. This was just something we threw together yesterday afternoon for testing. Any finished version would have a substantial plinth designed for stabilization. But it's definitely heaver up top than the other speaker type....

**Panomaniac** · October 20th, 2013, 04:51 PM

Here is the listening position graph of the Open Baffles. The MTM Inspire and the prototype crossover on the 604 open baffle. I think that the peak at the bottom is a room mode.
Inspire OBess

**Alien_Shore** · October 21st, 2013, 04:22 PM

Good Gosh Pano....welcome back!

That was a lengthy sabbatical you took.

**Panomaniac** · October 22nd, 2013, 04:15 PM

Hey thanks! Rest assured that I spent much of that sabbatical listening to my mighty, wonderful Altecs.

**Altec Best** · October 23rd, 2013, 11:33 AM

Originally Posted by Panomaniac

Hey thanks! Rest assured that I spent much of that sabbatical listening to my mighty, wonderful Altecs.

As we all have !

Pano has there been any updates to that HolmImpulse ? Haven't used it in awhile. That's a nice looking graph.. Very flat response.

**kipduff** · January 4th, 2017, 03:53 PM

Analog Adict or others:

My 604-8Ks and GPA XOs are arriving today Fedex! They have been re-coned by GPA for previous owner. Though I plan to eventually build a proper box (thinking 606)- for now, I want to get them up and running quick and dirty in my small room. I like the idea of off the floor and vertical- did this work out? Dimensions? Can anyone give me dimensions of known decent OB setup for the 604s?

Also, where can I find a frequency response testing and graphing program like the one shown on your laptop? I want to measure parameters to see how my 604s compare to parameters listed at GPA.

Thanks so much, Kip.........

**kipduff** · January 4th, 2017, 08:03 PM

Been researching OB for 604- perhaps not such a hot idea (although I'm still interested). Considering 620, 612, 606, or MLTL- would have smaller footprint anyway. Trouble finding specs for MLTL- did find "drummerwill's" older post with these specs: 44"X24"X19". I'm assuming Baltic Birch 3/4"/19mm- which I have found good source for. But there is no indication of size and placement of port or other details.

Would appreciate any more info if possible on MLTL or any new thoughts on 604 box.

Thanks, Kip.......

**analog addict** · January 5th, 2017, 10:46 AM

The OB 604's sound great, although much of the credit must be given to Dennis Had's custom crossover. I don't think there's anything magical about the dimensions either. Wide enough to fit and at listening level should be good enough for something temporary. As for the software, as mentioned in the thread it's holmimpluse freeware.

HOLM Acoustics

However, all the software in the world isn't going to do you any good if you don't have a mic capable of covering the frequency range of interest in a neutral manner....