Altec

[adityapm]

Thanks for such a detailed write up Aditya. Wealth of info there. Let me wrap my head around it slowly.

With regards to RCA MI 9584, Victor of Japan branded equivalent is what I have. It's bloody fantastic. Never a harsh note and its like honey. Very easy on the ears. But as pointed out it must be used with a tweeter up top as it goes upto 8000hz (movie soundtracks at the time only went that high up). Most small jazz trio music, vocal focused music and the like, sounds great 2 way. The phenolic diaphragms used are very rounded and just beautiful sounding. I would like to retain them for that.

My 288c have an aftermarket titanium diaphragm which is very detailed can sound a tad sharp and fatiguing at higher volumes only. I must change it to an aluminium diaphragm soon. But my observation within this brief period of using them is that the 288c even with the titanium diaphragm are very exciting and have a large sound. Very enjoyable. The scale of them and the large sound the 288s throw is very nice.

GPA wrote and said 288 diaphragms will be available on their website in January but it hasn't happened. They have the smaller format diaphragms listed on their website.
Now coming to the cabinet. It is narrowed down to an 815 and a concept A9 in my use case.
I am leaning more towards the A9 but would like to reduce the height to 4ft like you have mentioned can be done. But so will other allied measurements i am guessing.
I have a 2ft x1 ft concrete beam hanging down from the ceiling just about 3 to 4 ft away from where my speakers are placed. You think suspect qts and out of spec issues with my drivers will be better overlooked by a sealed A9 cabinet? Plus it helps that they are easier to build.
Another question that comes to my mind is should I worry about internal bracing or partitions etc or just build a bigger box as per the A9 concept spec?

The RCA MI95854 will sound balanced as long as the lower 3db tunning of the (bass) enclosure stays above 62 Hz. One will not miss anything. For a 12KHz top-end, the bottom end has to be at 40 Hz to make the sound sound normal/balanced. For a 15KHz top-end the bottom has to be at 33 Hz. Unless this is maintained, it will sound either thin-ish (bass lacking) or dull (HF lacking). Phenolic diaphragms are very good in the lower-mid area. After all they are closer to paper. Aluminum is closer to phenolics than titanium, and titanium is closer to aluminum. Cascading the drivers in this way gives the best transition from one stage to the other. As long as the music does not have anything below 70/80 Hz the RCA MI95854 will sound ok. Say The Beatles, they don't have anything below 100 Hz. Their recordings while mastering used to pass through a Hi-Pass filter wiping everything below 100Hz.

About GPA, nothing is working. Nobody is there now. They are replying like this to everybody as if to keep things afloat. Nearly 250 diaphragm orders (US local) are waiting since past 11 months.

The box construction has to be very rigid with lots of bracing of course. But these are a lot simpler than building a horn enclosure. Once finalized, I will give you the plans to do it. It will be quite heavy.

The parameter deviations will not be an issue here, as it will be a larger than required size, and we will fill it up by manipulating the parameters. Of course we will lose cone excursion for full wattage drive. But that will be a welcome feature also, meaning the system will also become more sensitive. I am using such an enclosure since 2016 November. It is like a big studio monitor sound. I never use tone controls. What ever the studio (where the programme was scored) has done, I listen to that. I have never needed tone controls. The studios use much costlier equipment.

The concrete beam issue may or may not affect. We will see to it later.

Bye

 

[Sushant Sharma]

The RCA MI95854 will sound balanced as long as the lower 3db tunning of the (bass) enclosure stays above 62 Hz. One will not miss anything. For a 12KHz top-end, the bottom end has to be at 40 Hz to make the sound sound normal/balanced. For a 15KHz top-end the bottom has to be at 33 Hz. Unless this is maintained, it will sound either thin-ish (bass lacking) or dull (HF lacking). Phenolic diaphragms are very good in the lower-mid area. After all they are closer to paper. Aluminum is closer to phenolics than titanium, and titanium is closer to aluminum. Cascading the drivers in this way gives the best transition from one stage to the other. As long as the music does not have anything below 70/80 Hz the RCA MI95854 will sound ok. Say The Beatles, they don't have anything below 100 Hz. Their recordings while mastering used to pass through a Hi-Pass filter wiping everything below 100Hz.

About GPA, nothing is working. Nobody is there now. They are replying like this to everybody as if to keep things afloat. Nearly 250 diaphragm orders (US local) are waiting since past 11 months.

The box construction has to be very rigid with lots of bracing of course. But these are a lot simpler than building a horn enclosure. Once finalized, I will give you the plans to do it. It will be quite heavy.

The parameter deviations will not be an issue here, as it will be a larger than required size, and we will fill it up by manipulating the parameters. Of course we will lose cone excursion for full wattage drive. But that will be a welcome feature also, meaning the system will also become more sensitive. I am using such an enclosure since 2016 November. It is like a big studio monitor sound. I never use tone controls. What ever the studio (where the programme was scored) has done, I listen to that. I have never needed tone controls. The studios use much costlier equipment.

The concrete beam issue may or may not affect. We will see to it later.

Bye

I didn't know the bottom and top end were interconnected like that. It only makes sense that they are. You learn something néw everyday.

My current cabs for the altecs were made for an 8 inch full ranger so I am expecting huge gains moving to a dedicated and proper speaker cabinet. Looking forward. Thank you.

 

[adityapm]

I didn't know the bottom and top end were interconnected like that. It only makes sense that they are. You learn something néw everyday.

My current cabs for the altecs were made for an 8 inch full ranger so I am expecting huge gains moving to a dedicated and proper speaker cabinet. Looking forward. Thank you.

You mean they are now with the 416-8cs ?, enlarging the holes to accommodate them ?
Send me the box size.

Thanks

 

[Sushant Sharma]

You mean they are now with the 416-8cs ?, enlarging the holes to accommodate them ?
Send me the box size.

Thanks

Post in thread 'Lii (song) audio silver 8.' https://www.hifivision.com/threads/lii-song-audio-silver-8.92298/post-1030359

These cabinets. Approximately 18 inches wide and 34 inches tall and 22 inches deep. Yes, I enlarged the hole to accommodate the 416 8c. I knew I was going to receive the 8a in the future and didn't commit to a new cabinet.
The 416 8a I just received this week and haven't yet heard inside a cabinet.

 

[adityapm]

Post in thread 'Lii (song) audio silver 8.' https://www.hifivision.com/threads/lii-song-audio-silver-8.92298/post-1030359

These cabinets. Approximately 18 inches wide and 34 inches tall and 22 inches deep. Yes, I enlarged the hole to accommodate the 416 8c. I knew I was going to receive the 8a in the future and didn't commit to a new cabinet.
The 416 8a I just received this week and haven't yet heard inside a cabinet.

This box (around 9 cu.ft) is perfect for a 416 as a standard BR design. But what about the Silver-8 project for which you had got these boxes built just a year back ? I think you should just use the 416-8c pair for some time now as it is, and also play with the other Altec/RCA units for some time in diff. prmutations & combinations and get the picture in the head first. This will result in a good decision/design choice. Let me know what you decide/want to do.

 

[analogadikt]

Yes, just a typo. These phenolic drivers are in the circuit only for the nostalgia sake.

The same also for old alnico drivers. I prefer the ferrites. They are a bit harsh when driven hard, but never lack punch or bite. After all they are rocks. But alnicos are metal. They are very permeable, and the hysteresis curve changes as the current varies. This is the reason why the measured parameters when used do not give the desired results. Parameter measurements are normaly done with very little signal strength, as little as 1 milliwatt. But real use happens always at higher currents.and at that level the parameters have changed. Thats what happens.The trick here is to use a higher current for the TSP measurements, and then it will work when they are plugged in. But driven hard they will not give that bite that one expects. They will somehow prevent clipping, and sound roundish. It is like triodes and pentodes. When driven hard triodes will still keep it smooth but wiill lose the bite, whereas pentodes will show their true nature, a pure current source, and will go on driving hard with bite and punch. Ferrite drivers' TSPs always work alright.
After all we have graduated from alnicos to ferrites, from phenolic to metallic. Once the production techniques were at hand, all became metal diaphragms and higher bandwidths arrived.

Thanks

Ha Ha Ha
That is going to make some guys here a bit unhappy.

Regards,

 

[srinisundar]

Ha Ha Ha
That is going to make some guys here a bit unhappy.

Regards,

Nothing going to make unhappy. Just for arguments they can,

Music is always a listeners choice and all the measurements is nothing once you liked the sound output. All the human ears are tuned for different hearing but the speakers are tuned perfectly with fixed crossover.

So we have to tune only the ears not the speakers which have fixed values. So stay tuned and take full measurement of your ears first.

Have fun guys. All the forum is for healthy discussions without biting too much about the ears.

 

[keith_correa]

So we have to tune only the ears not the speakers which have fixed values. So stay tuned and take full measurement of your ears first.

What organs does one need to press/poke for the tuning of one's ears?

 

[srinisundar]

What organs does one need to press/poke for the tuning of one's ears?

Listener's choice, what they think they have heard properly and know those frequencies and sounding best or natural or neutral or ??

 

[Hari Iyer]

And I thought room was important

 

[grindstone]

Hey @Sushant Sharma do these dimensions look close to your 8-cell?

Just wondering what the horn angles are

 

[Sushant Sharma]

Hey @Sushant Sharma do these dimensions look close to your 8-cell? View attachment 84149

Just wondering what the horn angles are

The RCA MI 6438 in the photo has bigger dimensions. My 2x4 cell horn is smaller at 27W X 28LX 15H (inches). Length is inclusive of throat. I will have to figure how to measure horn angles.

 

[grindstone]

Thanks--no need to measure anything on my account. The dimensions you gave are perfect and I appreciate you taking the time to get numbers and post!