ALTEC 604 E in small enclosure...

[Guglielmo]

Hello to everybody,

I am going to get a mint matched pair of Altec 604E so I am looking for a proper enclosure for this glorious driver. I read a lot about "original" boxes like 612 or 620 or DIY wonderful enclosures but in almost all cases the project requires a huge amount of internal volume.

I live in a small lodging so I can't afford a big speaker cabinet thus I need your skilled help to get the better performances even in a small volume enclosure.

First of all my available space would be in a "bookshelf-like" location namely on the upper shelf of a living room furniture. The possible maximum space is 34" length X 12" depth while the height is free even if less than the length.

I read also that this driver may accomplish some new trends like the Open Baffle design with a lot of natural fresh musical reproduction even if perhaps with some bass lacking... This Open Baffle theory could be a good approach for me because I could consider a frontal baffle with the 604 fitted to it and all around a frame less than 12" to allow rear flow of waves against the wall. Actually the enclosure would be an open baffle C shaped (front baffle with flour wings). By the way the cabinet location on the shelf is in front of the wall.
The other solution may be a classic bass-reflex but I guess that in this way I will have some problem with very limited bass response.
The allowed dimension are to be intended external so it must be considered for internal volume calculation the ?? wood thickness.
Please may you help me in suggesting the right design for these Altec?s.

I appreciate your contribution!

Guglielmo

[bowtie427ss]

Buying 604's with your space restrictions/limitations is much akin to buying a boat when you live in the middle of the desert.

Proper open baffles for a 604 will require as much or more physical space than a large bass reflex box.

There is no free lunch, there is no magic solution. If you insist on going the 604 route, you're going to make significant compromises dictated by the laws of physics. It's that simple.

[Guglielmo]

Yes, there is no magic solution... but, I would challenge these dimensional constraints looking for a discrete bass response. Take also in account that the listening room is small and the 604E will be powered by a bi-amp set-up with active Xover suitable for "playing" with frequency cross and output levels!

Consider that a whatever Vented System Calculator with 604E Thiele-Small parameters leads to reasonable dimensions with a reasonable low cut-off

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A 70 x 42 x 26 cm box with suitable port got this bass response with this Altec speaker

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Quite good isn't it?

[GM]

Too small to read, but it looks like your cab is ~2.5 ft^3 net using a 3" vent tuned to ~27 Hz will keep it within Xmax down to ~20 Hz @ 60 W peak before factoring in any room gain, which hopefully will allow a reasonably low in room LF corner frequency. Might could get up to ~piano bar avg. SPLs in stereo, which IME is about as loud as most folks will tolerate in a small room.

For Pipe organ symphonies or movies, it might be better overall to seal them up.

GM

[Alien_Shore]

Hello to everybody,

I am going to get a mint matched pair of Altec 604E so I am looking for a proper enclosure for this glorious driver.

Hello Guglielmo,
You will be disappointed with your glorious drivers in a small box. Consider:

I have a 604E that was recently reconed at GPA using 8 ohm parts. Here are the T/S params for my 604E:
Re = 6.76 ohms
Fs = 29.61 Hz
Qts = 0.394
Qes = 0.434
Qms = 4.247
Le = 1.301
Mms = 50g
Vas = 19.43

This just isn't a speaker that is going to perform well in a small enclosure. Mine didn't sound good in a sealed alignment even as large as 200 liters. Once I got up to about 250 liters in a vented alignment, the woofer really started to sound good. I agree with Bowtie on this, you should probably go with something smaller for your living space. The Super Duplex is a massive speaker, that needs a massive enclosure.

[GM]

Yeah, it really 'wants' at least 382 L net and preferably Vb = Vas assuming little/no room gain, either with a Fs tuning.

Gees, these Q specs are way off from OEM and previous GPA re-cones I have measured specs for [highest is a 0.33 Qts, most are 0.26-0.27], though the rest are well within the 10% accepted tolerance. Regardless, with bi-amping and EQ, as long as the cab is tuned to a bit below Fs, then one can trade efficiency for a flat BW to as low as required to blend to the room's gain curve. Will it sound as open, effortless as a large cab, of course not, but it shouldn't sound any worse than a typical high end 'monkey coffin' either.

GM

[sanhanul]

This just isn't a speaker that is going to perform well in a small enclosure. Mine didn't sound good in a sealed alignment even as large as 200 liters. Once I got up to about 250 liters in a vented alignment, the woofer really started to sound good.

Hmm,,It means I need 612 cabinets or 620 at least. (My 604s are in 614 cabinets- little bit over 100 liter- now)
I have to think about it again.