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PostPosted: August 30th, 2021, 7:58 am 
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Thank you for the Altec 15 cabinets (and to Joe Roberts, who gave them to you). They've languished for awhile, but finally are in use as my new subs.

The cabinets were a bit flimsy and resonant for my tastes, so I laminated the bottoms with three sheets of 3/4" plywood, as a base, the front &rear with 3/4" MDF, and added bracing top-to-bottom, side to side and front to braces. All braces tied together internally. The cabinet is still just shy of 4 cubic feet internally. The new driver is a Dayton RSS390HF-4 https://www.parts-express.com/Dayton-Audio-RSS390HF-4-15-Reference-HF-Subwoofer-4-Ohm-295-468 15" woofer.

Sanded, then sealed the cabinets with shellac. Finally, rolled-on some fresh house paint.

I'm tickled with the way they turned out and how they sound. They are cut off at 120Hz, 8th order right now, a number that may lower as a result of experimenting. Also need to play with the DSP to smooth out the room a bit. But I'm very happy right now!

Thanks again!

Stuart

PS, they are so heavy now, it takes two people to move them!


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PostPosted: August 30th, 2021, 10:04 am 
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Thank you! Glad to see that worked out so well.
And - heavy (cabinets) is where its at!


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PostPosted: August 30th, 2021, 10:16 am 
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Stuart Polansky wrote:
Thank you for the Altec 15 cabinets (and to Joe Roberts, who gave them to you). They've languished for awhile, but finally are in use as my new subs.

The cabinets were a bit flimsy and resonant for my tastes, so I laminated the bottoms with three sheets of 3/4" plywood, as a base, the front &rear with 3/4" MDF, and added bracing top-to-bottom, side to side and front to braces. All braces tied together internally. The cabinet is still just shy of 4 cubic


Stuart,

Just FYI:

Vintage Altec cabinets are flimsy by design. They are not used in sub bass region. Those flimsy cabinets produced glorious systems. You should look at One of the most revered vintage system, Altec A7.

Those were the days of high efficiency, high compliance and low Xmas drivers. Now, the drivers are low efficiency, low compliance and high-Xmas which require rigid enclosures.


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PostPosted: August 30th, 2021, 11:17 am 
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The thing that helps with the common for today smaller boxes is that with smaller dimensions, the bending moment of the panels is less. Also, depending on the crossover point, the wall resonances can sometimes be above the reproduced frequencies. Like everything else it depends.

Tom


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PostPosted: August 30th, 2021, 12:40 pm 
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Cogito wrote:

Stuart,

Just FYI:

Vintage Altec cabinets are flimsy by design. They are not used in sub bass region. Those flimsy cabinets produced glorious systems. You should look at One of the most revered vintage system, Altec A7.

Those were the days of high efficiency, high compliance and low Xmas drivers. Now, the drivers are low efficiency, low compliance and high-Xmas which require rigid enclosures.

I disagree with the word "flimsy" applied to the Altec speakers. My pair were constructed with 3/4" plywood with even thicker construction on the top and bottom along with a nice hard-wood veneer. The speakers were also reinforced inside with hard-wood bracing between the horns and woofers.

Before I got my sub-woofer (after substantial time screwing with the Altecs) they went down to 31-Hz. (as measured). However, having limited excursion range and low-mass cones (they had to meet the horns at 800-Hz.) they dropped off steeply beyond 31-Hz. So with serious low-bass content they got there but were wimpy about it. Adding the sub at around 40-Hz. provided the room-shaking power that I expected from big-ass organ pipes and concert bass drums. The sub also provided some kick-ass rock bass that the Altec got somewhat but the power into the room wasn't there. And yes -- to improve the overall sound I added constrained-layer damping in the form of two layers of ceramic pavers on the back and one layer on the bottom. Plus a decorative slab of marble on the top. So yes -- they needed help -- but flimsy? No way.

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PostPosted: September 1st, 2021, 9:09 am 
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Cogito wrote:
Vintage Altec cabinets are flimsy by design. They are not used in sub bass region. Those flimsy cabinets produced glorious systems. You should look at One of the most revered vintage system, Altec A7.

Those were the days of high efficiency, high compliance and low Xmas drivers. Now, the drivers are low efficiency, low compliance and high-Xmas which require rigid enclosures.


Shashi,

No real argument here. Although the drivers I'm using I wouldn't characterize as "low" efficiency at 90+dB/W/M, but certainly lower than the Altecs and other drivers from the 50s-60s.

Since the plan wasn't to build a vintage-type system with low XMAX drivers, using an enclosure "gloriously" vibrating due to the back wave of the driver, was not in the plans. The path chosen here might not be right for anyone else, but my preference is to have as little box wall contribution to the sound in the room as practical.

In my advanced years I've had several opportunities to sit and listen to a few Altec systems, including the VOT (A7, right?). Not my cup of tea.

Tom P pointed out to me the rigors of getting a ported enclosure right, and after having tried a few times, I'm agreeing with his approach of building a sealed enclosure and using digital equalization to extend the low end. Bass watts are cheap, unlike in years gone by (where equalization was a lot more difficult also).

I have a another pair of enclosures, 5 cubic feet each, whose resonant point is allegedly out of the driver's operating range. That may be, but the bass from those boxes is so muddy that this project was undertaken.

So, for me, a rigid enclosure is needed.

Thanks for the input, you should drop by sometime!

Stuart


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PostPosted: September 1st, 2021, 9:15 am 
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SoundMods wrote:
Cogito wrote:

Stuart,

Just FYI:

Vintage Altec cabinets are flimsy by design. They are not used in sub bass region. Those flimsy cabinets produced glorious systems. You should look at One of the most revered vintage system, Altec A7.

Those were the days of high efficiency, high compliance and low Xmas drivers. Now, the drivers are low efficiency, low compliance and high-Xmas which require rigid enclosures.

I disagree with the word "flimsy" applied to the Altec speakers. My pair were constructed with 3/4" plywood with even thicker construction on the top and bottom along with a nice hard-wood veneer. The speakers were also reinforced inside with hard-wood bracing between the horns and woofers.

Before I got my sub-woofer (after substantial time screwing with the Altecs) they went down to 31-Hz. (as measured). However, having limited excursion range and low-mass cones (they had to meet the horns at 800-Hz.) they dropped off steeply beyond 31-Hz. So with serious low-bass content they got there but were wimpy about it. Adding the sub at around 40-Hz. provided the room-shaking power that I expected from big-ass organ pipes and concert bass drums. The sub also provided some kick-ass rock bass that the Altec got somewhat but the power into the room wasn't there. And yes -- to improve the overall sound I added constrained-layer damping in the form of two layers of ceramic pavers on the back and one layer on the bottom. Plus a decorative slab of marble on the top. So yes -- they needed help -- but flimsy? No way.


Walt,

"Flimsy" was perhaps not the right word to use. Adjectives are a matter of perspective. Some people think their 13 second cars are "fast" or "quick". The guy with the 6 second twin-turbo 2400# car would disagree with that assessment.

But the cabinets, while the right size and appealing to me, were not nearly rigid enough to be used in the manner chosen.

Stuart


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PostPosted: September 1st, 2021, 9:38 am 
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Stuart Polansky wrote:
SoundMods wrote:
Cogito wrote:

"Flimsy" was perhaps not the right word to use. Adjectives are a matter of perspective. Some people think their 13 second cars are "fast" or "quick". The guy with the 6 second twin-turbo 2400# car would disagree with that assessment.

But the cabinets, while the right size and appealing to me, were not nearly rigid enough to be used in the manner chosen.

Stuart

I get what you were doing and agree whole heartily. Sub-woofer mechanics need a "bank-vault" of a speaker enclosure. My corner-mounted sub weighs 230-pounds -- one Altec weighs 110 pounds. Both have 15-inch drivers.

Of course the 15-inch driver in my sub looks like and behaves like it was made on another planet. :lol:


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PostPosted: September 1st, 2021, 10:09 am 
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Stuart Polansky wrote:
Cogito wrote:
Vintage Altec cabinets are flimsy by design. They are not used in sub bass region. Those flimsy cabinets produced glorious systems. You should look at One of the most revered vintage system, Altec A7.

Those were the days of high efficiency, high compliance and low Xmas drivers. Now, the drivers are low efficiency, low compliance and high-Xmas which require rigid enclosures.


Shashi,

No real argument here. Although the drivers I'm using I wouldn't characterize as "low" efficiency at 90+dB/W/M, but certainly lower than the Altecs and other drivers from the 50s-60s.

Since the plan wasn't to build a vintage-type system with low XMAX drivers, using an enclosure "gloriously" vibrating due to the back wave of the driver, was not in the plans. The path chosen here might not be right for anyone else, but my preference is to have as little box wall contribution to the sound in the room as practical.

In my advanced years I've had several opportunities to sit and listen to a few Altec systems, including the VOT (A7, right?). Not my cup of tea.

Tom P pointed out to me the rigors of getting a ported enclosure right, and after having tried a few times, I'm agreeing with his approach of building a sealed enclosure and using digital equalization to extend the low end. Bass watts are cheap, unlike in years gone by (where equalization was a lot more difficult also).

And with a port or passive radiator your transient response will suffer. It is inherent in the design because the first half cycle does not produce any output from the port because the energy has to build up in the port before you get output. Also, when the movement of the driver decreases, the stored energy in the port or radiator continues to put energy into the room.

I have a another pair of enclosures, 5 cubic feet each, whose resonant point is allegedly out of the driver's operating range. That may be, but the bass from those boxes is so muddy that this project was undertaken.

So, for me, a rigid enclosure is needed.

Thanks for the input, you should drop by sometime!

Stuart


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PostPosted: November 24th, 2021, 11:19 am 
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Joined: December 22nd, 2017, 9:25 pm
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VERY cool to see the boxes have value, and are so useable (albit well-modded).
I've got a pair of a/d/s SW300 subs (working fine) that came as part of a speaker purchase that I can't find a buyer for,
tho I offered them at $100/ea.
Like the Altec cabs, I'm hesitant to curb them, but I'm really trying to reclaim room before the holidays!

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