Altec 604s "built" into a Bookshelf?

[Encyclopediabsh]

Hi everyone - first post here, but have recently become fascinated with vintage Altec drivers, namely the 604. Wondering if anyone ever built a cabinet for 604s that would be placed inside a bookshelf with any success? From research, I realize that is not practical for most due to the physical size of the cabinet needed. However, I have custom built bookshelves (20" wide x 24" deep x as high as needed) that are quite large and already holding my Audio Note AN-E/SPe HE speakers on slide-out 500lb shelves. See attached pictures.

Since the AN are rear ported and like corners, their capabilities are not being maximized - even so, they still sound quite nice. From the mastering studio pictures seen on this forum, the 604s appear to be built into the walls in some applications with a vent/port in the front, which gave me the idea. My amp is a 10W Shindo, and since Shindo also mfgs a 604-based speaker, there must be pretty good synergy.

My plan would be to utilize GPA 604-8H-III drivers, included crossover, and build a suitable sized cabinet according to GPA specs of 9 cu ft and 45.5 Hz tuning. To fit within my bookshelf, the cabinet size would be approx 19"W x 22"D x 48"H, approximately 9.5 cu ft to offset internal bracing. Cabinet material would be the best 3/4" plywood I can find.

The listening room doubles as a family room, with floor space being premium and WAF definitely a consideration. The room has 12 ft ceilings, is ~20 x 30 ft deep with speakers on the 20 ft wall. The rear of the listening room has a 15ft opening into another large 20 x 20 room.

Any thoughts as to whether or not this might work? Waste of time? Thanks in advance...



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[cradeldorf]

Anything is possible.

[Nipper]

Since the AN are rear ported and like corners, their capabilities are not being maximized - even so, they still sound quite nice.

If they sound good to you that is all that matters.

The Altecs will sound much better though. I have seen raw Altecs built in to shelves and I have also seen some where the entire speaker cabinet was set into the shelf and then the outside of the shelf was framed and covered with speaker grill cloth to make it look "built in" because the owner wanted the Altec sound but they did not fit the decor (gotta keep the significant other happy you know).

The Altecs still sounded much better than anything else we put in there.... by far.

They may not have sounded as good as they possibly could but they usually don't because the room has as much or more effect as the cabinet, so you could say that about any speaker. We cant all have a sound room.

Altecs are good enough that you can lose some performance and still be fine. If you have to lose some, start with the one that has the most to lose.

It is certainly NOT a waste of time. You may need to modify it a few times and do some tweaking to suit your ears but I am willing to bet you will find it a fun and highly rewarding project.

The help and advice you get here will be the best.

[Encyclopediabsh]

Thanks for the encouragement Nipper - have decided to give the project a try. This evening, I quickly constructed a cardboard "model" of the cabinet estimating 9 cu ft of volume. Unfortunately, it appears the cabinet will be too large for a comfortable fit in my bookcase - mostly due to not enough room to rotate for appropriate amount of toe-in angle. The max cabinet size I can build would be approx. 6-6.5 cu ft. GPA-604-III literature suggests 9 cu ft. The 604-II literature says either 6 or 9 cu ft. I would prefer to use the 604-III vs. 604-II if possible. Bass response would likely suffer somewhat due to cabinet size, but hopefully not too much.

For a 6-6.5 cu ft enclosure, would the GPA-604-III work just as well (or hopefully better) than the GPA-604-II?[/B][/B]

I can send a note to the GPA folks, but thought someone here may know as well.

Thanks -

[VolvoHeretic]

What are the exact dimensions of the bottom half of the bookcase? Just build and attach an angled front baffle to mount the speaker to and get rid of the drawer shelf. If you have to, raise the lower upper shelf or eliminate it intirely instead of sacraficing cabinet volume.

[GM]

Greets!

Not to get off on the wrong foot, so to speak, but how does one define cavity resonances? Speakers in oversize alcoves!

Of course if they sound good to you, then so be it, but no way I would ever recommend it without some serious damping, so WRT the 604, making the cab fit the space is desirable. Some folks just gasket seal a baffle to the opening and front mount the drivers.

I?m assuming here that with only 10 W, this is a high output impedance SET amp. If true, then I?m rather surprised that GPA would recommend a tuning other than Fs.
[edit: I see this is a SS amp recommendation.]

Anyway, assuming you sit [LP] far enough away to keep from having to toe in the speakers and use the right alignment to best blend to the room?s gain curve, then no reason why it can?t work just as good as a floor stander in front of a bookcase and maybe even better due to less acoustic offset to the sound wall through the mids. Anyway, down low, the room dominates, so the main thing is to not sit in a null or the bass will be very ?thin?.

With a 30 ft deep room, it won?t have any lowest octaves gain to speak of within the speaker?s gain BW [Fs ? up], so first, the amp?s output impedance [not tap rating] or damping factor [DF] must be known, otherwise best to probably make it too large, then either seal it up or reduce it by adding in scrap lumber, bricks, or similar to find an acceptable system tuning.

How much bass you have will depend on tuning and how much output impedance the system has, but on paper you?ll lose several dB in the 30-40 Hz range with the smaller cab. Where you get big gains in the LF is with cab sizes at and above the driver?s Vas rating or ~11.7 ft^3 and a ~matching output impedance or higher, though these tend to sound ?boomy? when positioned next to a wall or corner.

GM

[Encyclopediabsh]

GM - thanks so much for the details. Just to make sure I understand understand correctly, you are suggesting it might be best to simply build a baffle for the front of my bookshelf, seal the openings and mount the drivers vs. building a cabinet to put inside the bookshelf? If so, cabinet volume will certainly not be a problem. At 23" x 20" x 44" high, cabinet volume is 11.7 cu ft. I have some holes drilled in the bookshelves for speaker wire, but should be able to seal 'em without too much problem. BTW, the amplifier is a Shindo Cortese, 10wpc F2A with output impedance of 250K ohms.

Concerning toe in, my current AN speakers reallly need the toe in angle to sound correct. Does the 604 have fairly good dispersion pattern where drastic toe in might not be as necessary?

I also re-measured the room - was going off memory before and got it slightly wrong. Correct room dimensions are 19 x 26, with bookshelves being ~9 ft apart, centered on the 19' wall - with listening position ~20' away.

Again, thanks for the help and suggestions. I'd really like to try out the 604s, but dont want to make a mistake based on my room!

[Encyclopediabsh]

Also meant to say the Shindo Cortese is a tube amp, not SS...