Best crossover for Altec 604-8G in 620 enclosure?

[amandarae]

Abe, did you try moving the 620 cabs around to maybe reduce the boominess? What about the impletation of any bass traps in yoru room? Thanks!

Hello,

You know, now that you mentioned it, I did not try getting aftermarket bass traps. I only use the bass traps copied from Chris Brady's (Teres Audio) website. I built 4 of them plus a 4'x 6' x3" fiberglass covered frame for the front wall. These were from my planar days longtime ago.

Yes, I tried to move the cabs around. My room is 22 feet by 24 feet, speakers located on the 22 feet side and have no option to use the 24 feet side as the front wall. The best location I got was about 10 feet away from the front wall, about 7' apart (checking my notes as i type) which was almost in the middle of the room. I cannot accept the compromise to have the speakers in the middle of the room as it looks so awful!

FYI, my 612C cabs are lifted ~5 inches using CLD type platform (Baltic Birch) from the floor, 10 feet apart center-to-center and about 3 feet from the sidewalls and ~3 feet from the front wall. I got the suggestion from a guy here in this forum(was that you?) to lift it up, and to me, the sound improve a lot. Never touch placement after that.

abe

[KBergsson]

Hello,

You know, now that you mentioned it, I did not try getting aftermarket bass traps. I only use the bass traps copied from Chris Brady's (Teres Audio) website. I built 4 of them plus a 4'x 6' x3" fiberglass covered frame for the front wall. These were from my planar days longtime ago.

Yes, I tried to move the cabs around. My room is 22 feet by 24 feet, speakers located on the 22 feet side and have no option to use the 24 feet side as the front wall. The best location I got was about 10 feet away from the front wall, about 7' apart (checking my notes as i type) which was almost in the middle of the room. I cannot accept the compromise to have the speakers in the middle of the room as it looks so awful!

FYI, my 612C cabs are lifted ~5 inches using CLD type platform (Baltic Birch) from the floor, 10 feet apart center-to-center and about 3 feet from the sidewalls and ~3 feet from the front wall. I got the suggestion from a guy here in this forum(was that you?) to lift it up, and to me, the sound improve a lot. Never touch placement after that.

abe

Interesting, my 604-8Gs in 620 cabinet copies are not boomy at all. I have them quite close to back and sidewall, use only damping material on one of each opposing sides inside the cabinets.
I had some muddyness in the bass with my old Quicksilver kt88 monoblocks, but midbass and bass are clean and detailed both wih my hypex ncore monoblocks (200w in 8ohms) and my diyhifisupply ld91 300b monoblocks (approx 7w).

Kjartan

[joce64]

Interesting, my 604-8Gs in 620 cabinet copies are not boomy at all. I have them quite close to back and sidewall, use only damping material on one of each opposing sides inside the cabinets.
I had some muddyness in the bass with my old Quicksilver kt88 monoblocks, but midbass and bass are clean and detailed both wih my hypex ncore monoblocks (200w in 8ohms) and my diyhifisupply ld91 300b monoblocks (approx 7w).

Kjartan

Hi to all,

I want again to thank you for your precious advices...

Kjartan, it's funny because someone is actually making me a little box to put a JBL bullet tweeter (crossed at 15000hz and up) to add on top of my Cabinets :-)

I am happy that the issue of damping for the 620 arise, because I was thinking of redoing the damping on the 620's (it is actually house yellow insulant on all faces except on the front facing (nothing).

I have no idea of what faces to damp or not. I have been advised with the following: put some elveshair on the back facing the 15 inches woofer (the size of the woofer)

https://www.solen.ca/pub/index.php?c...2&s2=2&s3=&s4=

I was also thinking of putting some deflex claissic pannels at least on the rear pannel...:

http://www.partsconnexion.com/product8815.html

My question is:

what faces should I damp and with the best possible material to improve sounding?

By the way my 620's, even with hous insulant, are not boomy at all. I just learned that mid-range could be well aimproved by better damping, but I dont know how to do it...

My cabinets are actually beeing painted with white lacquer (kitchen counter type...hi!hi!).

Another one for you Kjartan:

I will first try better caps and changed pots on actual original crossover by a wonderful reconing and experienced tech here in Montreal (he is the same one who told me about JBL bullet and actually doing the job).

Still, I recontacted Mast_Mutter to buy his crossovers, as the pair he was selling on ebay is not there anymore.

I want to thanks you for the picture posted which hlep me a lot to understand how these crossovers are working...

So I gue I will be able, like you, to connect my JBL bullet to it?

Do you think if would be relatively easy to put Mast-Mutter's crossover in a closed box, with the level pot outside? See, I have young kids and cannot let a crossover on a plank outside the 620s.

Thanks again to all and talk to you!

Jocelyn

[amandarae]

Interesting, my 604-8Gs in 620 cabinet copies are not boomy at all. I have them quite close to back and sidewall, use only damping material on one of each opposing sides inside the cabinets.
I had some muddyness in the bass with my old Quicksilver kt88 monoblocks, but midbass and bass are clean and detailed both wih my hypex ncore monoblocks (200w in 8ohms) and my diyhifisupply ld91 300b monoblocks (approx 7w).

Kjartan

You built the 620's yourself with reinforce panels and braces? I am talking about the original 620 cabs(at least that's what I used and heard). Yes, the Hypex @220wpc will help in the bass(because of the damping factor maybe?), but I do not use SS amp( I am very familiar with Hypex amps as I followed the discussions before at Audio Circle discussion threads). To me, no SS amp can bring out the real midrange sound of 604's compared to DHT's. Flea power DHT amp and Altecs is the recipe for me. My own opinion only of course.

- - - Updated - - -

Hi to all,


By the way my 620's, even with hous insulant, are not boomy at all. I just learned that mid-range could be well aimproved by better damping, but I dont know how to do it...

Jocelyn

If I were you, I will concentrate on the XO and amp to get the midrange better instead of damping the cabinet. When the midrange is at par with your expectations as you settle on the XO and amp to use for your Altecs, then worry about damping.

I said this because no amount of damping can make the midrange better than what you want it to be. The reason why it seems better at first as you increase damping is because when you damp the cabinet, you change its frequency( resonant freq of the cabinet) decreasing the effect to the midrange band of frequencies. In other words, the cabinet is resonating before damping, meaning, it booms ("boomy"). You can also experiment by changing amp with high damping factor to control the drivers better.
Just my opinion of course.

[KBergsson]

Hi for some reason I cannot reply with quote, probably memory constraints on my iPad.

Joce64, I use rockwool on insides top, back and one side. No other damping material. Sounds good to me. But I have also sorted out problems in the rest of my system, some of which I initially attributted to the loudspeakers. White will look good and make the cabs less imposing. I proposed to paint mine white, but my wife was happy with them as is, her only criteria was a close to the wall placement and therefore out of the way. My previous spekers had to be placed far from room boudaries. You can place the WJ crossover in a closed box. Once I found the optimal setting I leave the adjustement pot as-is. As you could see in the picture I connect my JBL075 tweeters to the WJ crossover, works fine for me.

Amandarae, yes the cabs are homebuilt (not by me, I bought the speakers and cabs with original crossovers). The cabinets are well built of finered mdf, but I also lift them off the floor, approx 5cm, by using rubber wheels. I also agree with you that even if the ncores are good amps, the LD91 set monoblocks are a far better match.

Regards
Kjartan

[joce64]

Hi for some reason I cannot reply with quote, probably memory constraints on my iPad.

Joce64, I use rockwool on insides top, back and one side. No other damping material. Sounds good to me. But I have also sorted out problems in the rest of my system, some of which I initially attributted to the loudspeakers. White will look good and make the cabs less imposing. I proposed to paint mine white, but my wife was happy with them as is, her only criteria was a close to the wall placement and therefore out of the way. My previous spekers had to be placed far from room boudaries. You can place the WJ crossover in a closed box. Once I found the optimal setting I leave the adjustement pot as-is. As you could see in the picture I connect my JBL075 tweeters to the WJ crossover, works fine for me.

Amandarae, yes the cabs are homebuilt (not by me, I bought the speakers and cabs with original crossovers). The cabinets are well built of finered mdf, but I also lift them off the floor, approx 5cm, by using rubber wheels. I also agree with you that even if the ncores are good amps, the LD91 set monoblocks are a far better match.

Regards
Kjartan

Hi Kjartan,

Thanks for the info.

One of my cousin, an engineer, just talked to me about rockwool yesterday! It's funny...

I was also told about thick industrial wool (French called it Thibaude de laine)

Since 10 minutes, I am now a proud owner of WJ crossover: I was lucky enought to pick a used pair on Audiogon!

I will report to all my impressions after this project completion in roughly two weeks...

I will be using them with Core Audio Technology Kratos Digital amplifier (this amp replaced a costy DIY tube equipment...)

I keep you posted,

Jocelyn

[amandarae]

Hi for some reason I cannot reply with quote, probably memory constraints on my iPad.

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Amandarae, yes the cabs are homebuilt (not by me, I bought the speakers and cabs with original crossovers). The cabinets are well built of finered mdf, but I also lift them off the floor, approx 5cm, by using rubber wheels. I also agree with you that even if the ncores are good amps, the LD91 set monoblocks are a far better match.

Regards
Kjartan

Hello Kjartan,

Nice cabs! Yes,the 300B is truly a great match for Altecs. I agree wholeheartedly!
I also tried 416 and 414Z (with 288 and 806) with a 300B AC and DC heated, it was very nice.

I have no experience with Ncores even though I am aware on how to source and build them. I only heard it once and not in my system. Again, I have to agree that to me from what I heard the Ncore was much better than other PWM(or digital in laymans term) amps that I had and tried(H2O monos using ICE Power and Class D Audio using Hypex modules). IMO, ruling out the Ncores, PWM amp sounds different. The ambience in the recording(using lp's) were lost or transformed to something different. Worst are those that all the processing is in the digital domain, again to me. It sounds like, errrr plastic!

Abe