A7 Port advice

[Tax]

Hi A7 Owners/Tweakers,

Greetings from Sydney, Australia!

I have recently bought a pair of Altec A7's consisting of 825 cabinets with 515B woofers and 802D CD's in 511B horns. The xo's are original N800-D units.

The previous owner had the 511B mounted inside the A7 cabinet ala "Magnificents" with the bass flare on the ground. I have played around with the speakers in my room and prefer the speakers with the 511B mounted on top of the box and the bass horn sitting directly underneath it (what I call theatre or original style).

I would appreciate your kind advice in relation to the dimensions of a baseline port I could start off with to fill the void of where the 511B used to be inside the box?

My preference initially is for a rectangular vent. I read somewhere on the hostboard that GPA had recommended a 26" x 3.25" vent.

Could I have the slot closer to the bottom of the cabinet (as in closer to the floor) or stick to the conventional middle of board placement?

Any advice you can offer is appreciated.

Thanks!

[Elitopus1]

Mine is 10"x7.5". I read somewhere that 75" is a good number for the port. My cabs also had the horns stuffed in the bottom when I got them. I had to cut a piece of plywood for the port area because that piece was missing.
The current port sounds much better than A7's I have heard with factory ports. Mine are tuned much lower. I would try other sizes and experiment but I like this setup too much

[LowOhms]

Hi A7 Owners/Tweakers,

Greetings from Sydney, Australia!

I have recently bought a pair of Altec A7's consisting of 825 cabinets with 515B woofers and 802D CD's in 511B horns. The xo's are original N800-D units.

The previous owner had the 511B mounted inside the A7 cabinet ala "Magnificents" with the bass flare on the ground. I have played around with the speakers in my room and prefer the speakers with the 511B mounted on top of the box and the bass horn sitting directly underneath it (what I call theatre or original style).

I would appreciate your kind advice in relation to the dimensions of a baseline port I could start off with to fill the void of where the 511B used to be inside the box?

My preference initially is for a rectangular vent. I read somewhere on the hostboard that GPA had recommended a 26" x 3.25" vent.

Could I have the slot closer to the bottom of the cabinet (as in closer to the floor) or stick to the conventional middle of board placement?

Any advice you can offer is appreciated.

Thanks!

Hello,

I run 825s, 515Bs, and 802Ds like you. Got my 825s for free, last December. The drivers I got for free, two years ago, from audiophiles in Kansas City I had audio and triode amp- mentored in previous years.

Find a port suggestion, many here will give you good input, use it, and proceed in this order :

The first thing I suggest is to stabilize the stock 5/8ths thick 825 box,

I suggest you do as I did, and put NO BRACING inside. The cheapest, easiest way to stabilize the 825 box, AND KEEP IT STOCK, is to add mass loading.

We have a large hardware chain in the USA named Lowes, and in their Garden Center, they have " concrete patio tiles ", which are about 11 1/2 inch square and roughly 1 3/4s inch thick. Each weighs about 17 pounds, cost about $1.48 a tile. I added about 300 pounds of these tiles to each enclosure, on top, mostly at the rear, and the AMOUNT of weight was selected by MY ear, till I was satisfied. Total cost, maybe $75, and it is REVERSIBLE. Do this first. Tiles come red and gray, I chose reddish ones.

The second thing I would do is optimally wire the amp to crossover, the crossover itself, and the crossover to the drivers with FAR better ( heavier in most cases ) wiring, to improve your system's transfer efficiency. See details of what I did, wiring wise, in my post in this thread :

URL :

See my post #8, regarding decent wiring, in this URL : ..Proposed Parts List for Model 19 Crossover

The 800HZ 12 dB crossover is what I prefer ( A7-800 ) over the 500 HZ frequency. But the third thing "I" would like to suggest is you re-do the crossover with FAR better caps, better wiring, and maybe better inductors. One cap that NEEDED to be in " my " crossover for the VOTTs to display magic pleasing to me, was a DynamiCap 4.0 uF E series, in all four positions, as part of a "bypass" to an other special high-current, uber low ESR cap I used to get the 8.62 uF Butterworth / 16 Ohm crossover cap value. I will be happy to share the cap specifics privately.

After you do all three suggestions FIRST, you can play with port size. NO rush. The correct size YOU and YOU ALONE select by ear. Its a function of many factors, but YOU alone can decide that by listening.

If you have any questions, or need help, email me as I check that often [email protected]

What sotra nice amp you going to use on them.??

Since April, I have been working on a SET DC coupled Type 45 amp, 1.5 Watts or so, and whatever I did in the amp-build, was heard, LOUD AND CLEAR - on the speakers. Suggest a two stage 2A3 amp, DC coupled, as a good design. I can help you, if you DIY, with that.

Consider these three suggestions, then YOU need to choose the port size for your system, by your ear !!!

Have fun, I am.

Jeff Medwin Low Ohms

[Elitopus1]

Jeff:
I'm curious how you have your horns mounted. With all the pavers on top it seems like there would be very little room. You mentioned before you run some EH500 clones.

I put some extra bracing in mine and have considered adding some more support to the flares. Mine are the newer MDF 828 cabs. I think if I added weight on top it would crush them

[Phil-G]

Jeff I don't see any reason to keep an 828 cabinet "STOCK". unless it's in near factory condition with original drivers.
you can add / change the portboard to modify the port area without modifying the cabinet. and changing the port is by far the most effective way of getting more out of an 828 cab. the next would be putting effective bracing inside the cab. along with foaming or packing the horn flares with sand to keep the
hornflare buzzing to a minimum. (the latter adding "mass loading")

[mah]

Tax, An old thread:

That old saw: A7 port size

[wweigle]

I modified my ports to 10" x 6". Can't remember exactly what my rational was for choosing this size. At the time I was running some JBL D130s. Currently using a set of 604Es as woofers. Sound pretty good to me.

[Tax]

Hello,

I run 825s, 515Bs, and 802Ds like you. Got my 825s for free, last December. The drivers I got for free, two years ago, from audiophiles in Kansas City I had audio and triode amp- mentored in previous years.

Find a port suggestion, many here will give you good input, use it, and proceed in this order :

The first thing I suggest is to stabilize the stock 5/8ths thick 825 box,

I suggest you do as I did, and put NO BRACING inside. The cheapest, easiest way to stabilize the 825 box, AND KEEP IT STOCK, is to add mass loading.

We have a large hardware chain in the USA named Lowes, and in their Garden Center, they have " concrete patio tiles ", which are about 11 1/2 inch square and roughly 1 3/4s inch thick. Each weighs about 17 pounds, cost about $1.48 a tile. I added about 300 pounds of these tiles to each enclosure, on top, mostly at the rear, and the AMOUNT of weight was selected by MY ear, till I was satisfied. Total cost, maybe $75, and it is REVERSIBLE. Do this first. Tiles come red and gray, I chose reddish ones.

The second thing I would do is optimally wire the amp to crossover, the crossover itself, and the crossover to the drivers with FAR better ( heavier in most cases ) wiring, to improve your system's transfer efficiency. See details of what I did, wiring wise, in my post in this thread :

URL :

See my post #8, regarding decent wiring, in this URL : ..Proposed Parts List for Model 19 Crossover

The 800HZ 12 dB crossover is what I prefer ( A7-800 ) over the 500 HZ frequency. But the third thing "I" would like to suggest is you re-do the crossover with FAR better caps, better wiring, and maybe better inductors. One cap that NEEDED to be in " my " crossover for the VOTTs to display magic pleasing to me, was a DynamiCap 4.0 uF E series, in all four positions, as part of a "bypass" to an other special high-current, uber low ESR cap I used to get the 8.62 uF Butterworth / 16 Ohm crossover cap value. I will be happy to share the cap specifics privately.

After you do all three suggestions FIRST, you can play with port size. NO rush. The correct size YOU and YOU ALONE select by ear. Its a function of many factors, but YOU alone can decide that by listening.

If you have any questions, or need help, email me as I check that often [email protected]

What sotra nice amp you going to use on them.??

Since April, I have been working on a SET DC coupled Type 45 amp, 1.5 Watts or so, and whatever I did in the amp-build, was heard, LOUD AND CLEAR - on the speakers. Suggest a two stage 2A3 amp, DC coupled, as a good design. I can help you, if you DIY, with that.

Consider these three suggestions, then YOU need to choose the port size for your system, by your ear !!!

Have fun, I am.

Jeff Medwin Low Ohms

Thank you Low Ohms!

I will email for advice. I am travelling for the next 3 weeks.

My cabinets could actually be 828's. They were built around 1970. They are 3/4 MDF with a veneer on the outside.

I am starting off with a 28" x 5" port and will experiment from there.

Will look into mass loading.

Kind regards
Tax

- - - Updated - - -

Mine is 10"x7.5". I read somewhere that 75" is a good number for the port. My cabs also had the horns stuffed in the bottom when I got them. I had to cut a piece of plywood for the port area because that piece was missing.
The current port sounds much better than A7's I have heard with factory ports. Mine are tuned much lower. I would try other sizes and experiment but I like this setup too much

Thank you!

Could you share your experience with the Emilar EH-800 horns? Mine came with Emilar hirns but I changed them to 511B's to keep them traditional.

Kind regards
Tax

[Elitopus1]

Could you share your experience with the Emilar EH-800 horns? Mine came with Emilar hirns but I changed them to 511B's to keep them traditional.

I prefer the bowtie horns over the 511b. You should experiment with both and I bet the Emilar will win. I prefer the EH500 even more but I am waiting to get a second one. They are hardish to find with the Emilar 2"-1" adaptor.

Good luck with your Altec project!

[Tax]

I prefer the bowtie horns over the 511b. You should experiment with both and I bet the Emilar will win. I prefer the EH500 even more but I am waiting to get a second one. They are hardish to find with the Emilar 2"-1" adaptor.

Good luck with your Altec project!

Thanks!

That is good to know. I will experiment with the Emilar.