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Home-built bass reflex towers!


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Inspired by mdeneen's home built speakers, I also picked up some vintage Altec components: 515C woofers, 511B horns, and 802D drivers, and an N500E crossover thrown in for good measure.

We have done some preliminary calculations as to the volume of the bass reflex boxes necessary. In order to ever fit these anywhere in the house, I may have to experiment with some unconventional design configurations.

What it is looking like at the moment is a taller box of 7 to 8 feet high and 20" wide and 22" deep. (may have to tie to wall for stability). Obviously this will necessitate the horns being mounted vertically within the cabinet -although on the outside of the face plate. I heard something mentioned about vertical horn installations and it sounded like this might actually have positive effects. What is this "mirror imaging" factor I heard mentioned, please explain.

btw, the plan will include connects for both use of this internally installed crossover, but also with option for biAmping. Also there has been some discussion of a convenient method for changing the port length as a possible variable factor for experimentation and ongoing customizing of the bass response.

-Lanced and Singing

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Cornwalls

currently upgrading

to all tube components

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Don't your doors to the outside have the normal 36" opening?

24" x 36" x 46" will equal the volume you described (about 40,000 cu. in.). That will go through a 30" door and is about the size of the original VOTT bass cabinet (imagine that!). Put your 511Bs on top. I believe I'd build a front baffle with sides for the HF horn to hide the crossover.

John

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Clipped---Sorry buddy but 515s just ain't good vented-box speakers (as is evidenced by the huge boxes needed), they were designed to drive horns. You'd probably be better off with 416s or use the 515s in horns. With 416s you'd get nice sized boxes, around that of a Cornwall, very solid bass and you could mount the horns horizontally as is proper (I don't think 90 degrees vert and 40 horz is gonna sound too cool). Or maybe the 515s would work with an EQed vented alingment in a smaller box. IME with 825 (A7) cabinets 416s make much better bass than 515Bs.

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Clipped and Shorn

Man I thought you fell off the earth. Between MDeneen being so busy and you disapeering and MH hitting the road this place has been real boring.

Glad to see you back !!!

On the horn placement issue. I was at a Chicago Horn Club meeting a week ago and Afredo has a Altec bass and horn setup and at the end of the day we started messing with the horn placement in his acoustically challenged room and ended up with the horns Vertical and the difference in detail and stereo separation was amazing.

I'm thinking about building some new enclosures for my heresy's and I think I'll make the front removeable and replaceable because vertical mount will have to be at least tried to see what it sound like. I've heard of people saying heresy's sound better on there side. I guess I should try that also.

Craig

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I just found this:

http://www.wmeckle.com/INTRO/LARGE/Altec.htm

and it states:

515C 1978-1982 16 Ohms 75 Watts Same as above 16" frame version of 515B. has regular constant impedance voice coil, lacks mids in horn enclosures. Great vented box woofer. Same remedies apply as 515B, last Alnico magnet 515.

what grabs me is:

"LACKS MIDS IN HORN ENCLOSURES.GREAT VENTED BOX WOOFER"

Is not the cabinet with the speaker mounted up front and with a port called a "vented box". Maybe there is hope for this 515C in this context afterall.

Sounds to me the 515C is more like the perfect speaker to use in a bass reflex cabinet

I guess it would be best to build a more conventional dimensioned box and mount the HF horn in the horizontal orientation because of dispersion issues. I am still curious to know exactly why the 511B horns mounted vertically would be a disaster but I guess it has to do with the Q factor dealiebobthingy that I was starting to read about that referred to those same numbers you mentioned eg. 90 degrees and 40 degrees, but I confess this is over my head at the moment.

I think I will just try to get them in there horizontally.

÷?<=çµ???ed and ´<caron>Á¨Ø?ed

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Cornwalls

currently upgrading

to all tube components

This message has been edited by Clipped and Shorn on 05-15-2002 at 02:34 AM

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As usual, I jumped into the deep water without knowing what I was doing. So if you had these components I mentioned , how would you best utilize them?

On a quick calculation we came up with something in the neighborhood of 37,000 cubic inches. I think something in the area of 37,000 to 40,000 cubic inches is about right.

The 511B horns are themselves about 24" across so it would be a tight squeeze to fit them horizontally into the same box if I wanted to keep the width of the box in the 24" range , but I guess I could just about do it.

A box 24" by 24" might work if it was around 65" tall

Probably a bit taller than that if I take into consideration the thickness of the plywood, the volume occupied by the bracing inside the box, the volume occupied by the cossover units inside the box, and the volume that the 511B will displace by being inside the box. Probably end up closer to 72" or 6 feet, I could live with that. Somewhere I had a calculation for the exact amount of volume displaced by the 511B horn when it is inside the box, but alas I have misplaced it, anyone remember it? I will search my HD and see if I remembered to save it somewhere.

Here is someone who has a 515C:

http://www.vt52.com/diy/myprojects/speakers/bass/bass.htm

He seems to think the 515C needs 150-200 liters of volume in a bass reflex box, what does that translate to in cubic inches? I get about 12,205 cubic inches, that doesn't seem right, so he must be talking about a horn box. I am not using the 515C in a horn box because I do not want to loose the mid range. I don't mind the extra volume needed. mdeneens cabinets are real and they are spectacular.

"Or maybe the 515s would work with an EQed vented alingment in a smaller box."

How do I go about finding out what you are talking about here? What is a "EQed vented alingment"?

IME with 825 (A7) cabinets 416s make much better bass than 515Bs.

I have 515C, not 515B, if that makes a difference.

mdeneen, designed his own ported cabinets, that was my inspiration. I have seen the designs for the A7 cabinets, but that looks more complicated to build. mdeneen also had some other reasons he didn't go with that A7 type design. I will have to ask him again about that.

We were able to look up the parameters from some calculators that mdeneen downloaded, and that is how we arrived at the volume<~ 37,000 cubic inches> and the (6"diameter) port length of around 9 inches or so. I will double check those estimates before doing anything.

¡£¢?§¶ªº!=ed and ?بÁ<caron>´d

------------------------------------------------------------------------

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Cornwalls

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This message has been edited by Clipped and Shorn on 05-15-2002 at 02:46 AM

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John,

"Don't your doors to the outside have the normal 36" opening?"

It is not the doors, I just want them narrower in the front room.

"24" x 36" x 46" will equal the volume you described (about 40,000 cu. in.). "

Are you talking about a VOTT style box, or just a large bass reflex box with the woofer mounted on the front plate.

"... is about the size of the original VOTT bass cabinet (imagine that!). Put your 511Bs on top."

I might consider putting them on top, althought that puts them up kind of high. by putting them inside the whole system will not appear to be so tall. I imagine there is an optimum distance between woofer and HF horn.

"I believe I'd build a front baffle with sides for the HF horn to hide the crossover. "

I am not sure I get the picture here. You mean, with the HF horns sitting on top, still build a front baffle just to hide the crossover. Why not put the crossover in the bass box?

I think I am still inclined to put the HF horn inside the box and figure out a way to place the HF horn in a horizontal orientation.

åß?©???¬æd and ÅÍÎÏ´´ÓÔ?ÒÚÆd

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Cornwalls

currently upgrading

to all tube components

This message has been edited by Clipped and Shorn on 05-15-2002 at 02:08 AM

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I have been studying up at

http://nleinternet.net/alteclansingunofficial/prouseinfo.html

You can get quite an education there.

I am seeing the true complexity of all that needs to be considered.

I do also have the diagrams for the A-7 and A-7 -500 cabinets, and I see they specifiy 416s. So what do Altec fans do with this 515C?

Another option is not to use the Altec system in the house, but rather in another studio where space is more abundant, in which case I will not need to go so tall.

The reason for considering the tall box was to give me the option of trying them out in the house where space is more limited. 2 feet by 2 feet by 6 feet might not be so weird afterall. It will be a bit tricky to mount the 511 horns horizontally, but I think I can do it by custom notching into the corner bracing on the inside of the box.

÷>=<=µ??ç??ed and <sum>´®®¥¨ø<pi><pi>ed

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Cornwalls

currently upgrading

to all tube components

This message has been edited by Clipped and Shorn on 05-15-2002 at 02:13 AM

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I just thought of a funny scenario in which I go back to my original post and edit it so drastically that it doesn't say at all what it originally said. Then I could respond to what people replied by saying that I didn't know what they were talking about....and that they must be dreaming. Like shredding documents. Nah...I wouldn't do something like that.

¡£¢®©??µ<=ed and ?ç©??ºø¶´?¥¬±Øed

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Cornwalls

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to all tube components

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Craig,

You mentioned something rather interesting:

"Afredo has a Altec bass and horn setup and at the end of the day we started messing with the horn placement in his acoustically challenged room and ended up with the horns Vertical and the difference in detail and stereo separation was amazing. "

This does sound intriguing to me. Maybe the vertically mounted Altec horn might not be a disaster? I am curious. Any other feedback on this possibility ???

?´´Ó?Ô?ÔÒÚÆd and ?Ç´´ÓÔ?ÒÚØÓ<caron>Á´´<caron>ÁÏed

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Cornwalls

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lynnm,

Its good to be back. I like thinking about this stuff and working on these projects. btw, As I remember you were one of the first people who welcomed and encouraged me here when I first got into those extravagant Cornwalls a year or so ago. Now they are all tubed up and sounding just fine.

¡£¢?§¶ªºª¶§?ed and ŸÍ?´ÎÇÏ?fi<caron>´´??ed

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Cornwalls

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dougdrake,

{C & S - Don't forget the icemaker!

- Crushed and Cracked}

If I install one inside the bass enclosure I will have yet more volume to compensate for, maybe the icemaker should sit on top.

With all my signature making, I never came up with Crushed and Cracked, good one.

Now I am onto a lazy solution.....

÷>=<=µ?<caron>Á¨·°flfiÏ´´ÓÔed and ±Æ¿<breve>ÒØed

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Cornwalls

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TBrennan,

mdeneen mentioned you knew a lot about these Altec speakers. Do you happen to know how much volume the 511B displaces when installed inside the box? I came across this info once and don't remember now.

What do you make of Craig's positive experience hearing the Altec horn vertically?

Now that I think of it, mdeneen was the first one to mention this possibility when I told him of the space constraints. He would probably say to run it by you to see what you think. Now I am getting curious about it. Guess I could run a little experiment here in the house and hook up those critters and check this out myself.

??©¥µ©???ed and `/fiflfl¨ÓÔ?ed

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Cornwalls

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The only version of the Altec 515 that works worth a hoot in a vented enclosure is the 515-8G. The 515-8G will work the best in a (surprise) Cornwall sized enclosure tuned about the same as (surprise) a Cornwall. The second best 515 for a vented enclosure is the 515-8LFE (low frequency extension), it works best in a Chorus sized box. The group delay, a parameter associated with transient response, looks better on the G than the LFE. The Qts on all the other versions of the 515 is just too low for a ported box. The 515-8GHP (high power) is the best in a horn enclosure, it will have 3dB more midrange above 280hz than the 8G.

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So then what is the best way to construct a DIY enclosure for the 515C?

What is with the info I found on the Altec site about the 515c? eg.:

16" frame version of 515B. has regular constant impedance voice coil, lacks mids in horn enclosures. Great vented box woofer. Same remedies apply as 515B, last Alnico magnet 515."

Seems like some kind of contradiction here. The 515c must be good for something. What is it?

I'll bet if I put the 515Cs up for sale, someone will want them, the question is why do they want them and what would they be doing with them? What did Altec have in mind when they bothered to make them in the first place? How bad could they be in a vented box?

©??´® and ªø¨??µ<=

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Cornwalls

currently upgrading

to all tube components

This message has been edited by Clipped and Shorn on 05-15-2002 at 10:57 AM

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Clicked and Dragged-That Altec Bass Alfredo sounds yummy. Should go great over your noodling.

fini

P.S. I see you're staying up late, lately. Are you now creating your signatures by falling asleep at the keyboard, and letting your forehead do the typing? What's the name of that technique (on the piano)?

This message has been edited by fini on 05-15-2002 at 09:18 AM

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P.S. I see you're staying up late, lately. Are you now creating your signatures by falling asleep at the keyboard, and letting your forehead do the typing? What's the name of that technique (on the piano)?

In Jazz, we just call that a "head" arrangement, but the technique I am using here is like a glissando, just sweeping my hand over the keys while holding down the right pedals.

¸/?Ç??¯<breve>¿ed and fifl°·ÅÍÎÏ´´ÓÔ?ÒÒ¸?Ç??¯ed

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Cornwalls

currently upgrading

to all tube components

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C&S,

The reason to put the 511B on top of the box and build a 3 sided "fence" around it is to make it look like it's in the box, but it's not so the calculations for the box are easier. If the box is short, you could even put a top on it, ala La Scala.

I AM talking about a bass reflex box.

The optimum distance between the woofer and tweeter would be that smaller than the wavelength at the crossover point.

John

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