Sounds like you're volunteering to bring these up to standard for this fellow. I'm sure he will appreciate your gesture.
I'm still running with a pair of Polk 5 JR from the monitor series and have no complaints. I think about upgrading from time to time, then just save my money for a rainy day (or records or other upgrades, etc)....
The components alone are worth three times this price. I wouldn't dismiss their "stock" sound. It is likely to be way better than what you might be led to believe. This is not just a bunch of junk that has randomly been pieced meal together.
They sound like a project. They also sound like for a $200 investment, I might end up with a nice pair of speakers as I learn about horns and how to upgrade and tweak everything. I'm not in a hurry for a pair of speakers so maybe this is a good winter project and if they don't turn out to be for me, I guess I could get my $200 back somewhere! Think I'll roll the dice and pick them up this week.
From the picture, I would count that at least the woofers will need to be re-coned, so I would figure that in.
deals like this are very rare these days…last great deal for me was my set of ADS 980’s about 7 years ago…$250…since then I’ve seen 1 other set, a trashed pair for a grand… I would grab these, clean them up, find a good out of the way spot for them and just take your time…
Its a 15" coaxial Altec 604. If I remember right the frame dimension was closer to 16" A good driver that was the standard for recording studios back in the day until JBL took over with a more versatile and compact product. The 604 is still a valued driver. It's quite efficient, but does need work to get the best sound out of it. A better crossover and close attention to box and port size is an advantage. Even then, several powered subs would be recommended. Some will add a supertweeter, but for an old fart like me, I am happy with the treble extension- as long as it's smoothed with quality capacitors in the design. When it's all dialed in with the right design, amp and source, the 604 can be very good within it's limitations- just like anything else.
I agree with what you are saying about the cabinets and capacitors but I would be much more enthusiastic about describing the results. I’ll not gush as to avoid sounding like a man that brags on his own equipment but the cost of 6o4’s in the used market should be solid evidence they are well liked. I really wouldn’t compare them to JBL monitors in any way. also, there is a range of 604’s, Alnicos are a very nice option.
Nice! I was just curious for I think I have a pair of those in 12" and I'm not sure if its a good model. I didn't pay attention because I was chasing a different kind of speakers...
I have heard the A7 numerous times, in both a mid sized room and a VERY large room. You are correct in that the bass pretty much rolls off below 50 Hz or so. It has the typical nice bass in relation to efficiency that most large speakers like this have. The bass rolloff is intentional as a very low Fs driver would need a larger X-max and therefore would lose sensitivity. They have nice sound, loud sound, and decent dispersion of that sound, but deep bass is simply not their strong suit.
This is a typical frequency response of an A7-500 in a 6000 cu-ft room, taken at the listening position 11 1/2' away. It's pretty much signed-off by 40Hz.
48” H 19” W 17” D Drivers are 605b’s. Building my own crossover…like I said killed my back this summer and these aren’t easy to move around…so this is a next spring project now…
The 828 bass cabinet kicks in at 500-Hz. (With the 500-Hz. Crossover). The horn takes the bass from 500-Hz. down to around 130-Hz., which is limited by the horn mouth. This is a very small bass horn in itself. From 130-Hz. the bass reflex part of the cabinet takes over and allows the low frequencies to go down to about 47-Hz., which is the -3 dB. cabinet limit. There are those who reduce the size of the bass port itself, to lower the -3 dB. point. That becomes a trade off and there is a reason that the Altec engineers did not take this "obvious" route. Without any modifications, the relaxed tuning of the bass port allows the F6 point to be down around 40-42 Hz. (approximately). For reference, the open lower "E" string of an electric bass guitar is 41.5 Hz. But, because the port is not more precisely tuned higher, the bass frequency roll-off is more gradual and does dip down into the 30-Hz. range, abit with more attenuation. When you use a tightly tuned bass reflex port, you have the advantage of a lower -3 dB. point. The trade-off is that beyond that point, the bass roll off becomes very sharp, with the F6 point only a few cycles lower and the bass quickly drops off. Absolutely it does! Very much so! Besides being much more efficient, the transient response is greatly improved due to having a large cone surface area but a very small amount of cone excursion. You can't even see the woofer cone on a A7 vibrate. You can play bass from an electric bass guitar at very high SPL's, and you can barely even feel the cone vibrate, while touching it with your hand. The sound of the bass is not constrained or forced. It is open, relaxed and natural.
True, but physical principles limit what a horn loaded speaker can do. There is so much and so much only you can do with a speaker the size of an A7. It does exactly what it is designed to do. That is to deliver sound with a limited response range and to deliver it as most realistically as possible. A7's and Altec theater speakers in general, are designed with emphasis of voice reproduction sounding natural. The design carries this down to the physical limits of the cabinet. The engineering emphasis is on quality bass reproduction, not sacrificing quality natural bass for deep bass. The A7 design is a very practical all around design. It does what it is designed for exceedingly well.
One of the principles of the VOTT cabinets, which I got from information provided by one of the original designers, was to have a high enough cutoff that 60Hz hum from the optical sound chains (and magnetic ones too) of the day could not become obtrusive. The port size is well chosen to have almost exactly the same output as the horn at the port tuning frequency. I've played around with smaller port sizes, but these greatly reduce the efficiency of the port. All in all, the original engineers really nailed the design for its intended purpose, and there is little to be gained aside from stiffening the walls of the cabinet. The 5/8" plywood thickness was chosen to keep shipping and installation weight reasonable. Thickening this helps quite a bit, especially in the area of the LF horn. Here is a near field response plot of the relative outputs of the LF horn and the port - they are well matched.
Which is a good thing because the voice coil of the woofer is barely overhung in the magnetic gap, and is almost underhung. If the cone travels very far at all, part of the voice coil will exit the gap and distortion will increase. On the flip side, having almost all of the voice coil always within the magnetic gap yields extreme efficiency and transient response.
