Novice questions re: 1st DIY full range project - existing cabinets

[planet10]

Originally posted by rbclark
Funny - I thought maybe... just maybe... I would submerge into the DIY custom speaker building world just long enough to restore good sound to these old cabinets at a one-time expense as opposed to becoming a tweaking perfectionist with a regular speaker budget. Yet, here I am with 2 projects lined up before I even get the 1st one under construction!

muhaha

Another addict in the making...

And you can bet that as soon as I stumble across the budget tube amp (easy kit? pre-built?) that gets the diyAudio seal of approval that'll be project #3!

Kit (aimed squarely at the beginner)

<http://www.bottlehead.com/et/adobesp...paramourII.htm>

this is one that a lot of people do as a starter because the entry is so low. There are at least 4 variations

http://www.tubedepot.com/diy-k12m.html
http://www.tubeaudio.com/page23.html
(the monobloks) http://www.tubedepot.com/diy-k11m.html

and some user builds
http://diyaudioprojects.com/Tubes/K-...-Kit/index.htm
http://diyaudioprojects.com/Tubes/K-12M/K-12M.htm

a little more ambitious

http://www.diyhifisupply.com/diyhs_joplin.htm

and if you want a pre-built amp, this one is probably the pinnacle of SE EL84s.

http://www.vaughnaudio.com/carina.html

These guys supply someof the better "pre-built kits"
http://www.divertech.com/antiquesl.html

and here is a laundry list (showing the bewildering choices available)
http://www.worldtubeaudio.com/direct...ategorie_8.htm

and for every kit there are probably 10 fairly well documented diy builds.

As far as the break-in suggestion, are you saying that sometimes the driver terminals come improperly marked?

Not often on a product like Fostex (i've never found a set mislabeled). You will find that not all manufactures use the convention that positive to red pushes the cone out thou.

dave

[seventenths]

RBC,
Funny isn't it? I started along this path with similar goals. To this date, I have built a CMOY headphone amp (It didn't LOOK like bait ), then a gainclone, then a Bottlehead S.E.X amp (excellent kit) then a set of BiBs and now I'm in the middle of a scratch-built tube preamp. A Nelson Pass amp and a set of Hemp fr8 SpawnOFH cabinets are on the short list of coming projects but the list seems to grow as if it were alive...

I get an insane level of gratification from this new hobby


Good luck with your decision...


7/10

[rbclark]

Originally posted by gychang


Bob, this is not good. Typical symptom of CUIDIY syndrome. (caught up in DIY). I have the same disease, be careful.

gychang

I'm predisposed to getting CUI. Should be no surprise that I now get CUIDIY. Thanks for the diagnosis.

[rbclark]

Originally posted by planet10


muhaha

Another addict in the making...



dave

Dave,

I thank you for your tube amp suggestions.... and my wife thanks you!

Bob

[rbclark]

Uh oh....

Got the drivers today. Got one installed and it sounds terrible. Any bass causes a very bad distortion. Anything else is ok - but I'm not sure how ok at this point. This couldn't be a break-in thing... I don't think.

Here's what I did:

The driver is installed in the top hole of the existing cabinet. Turns out that it fit the hole w/out modification. (The hole is 5.75" and the driver's specified baffle hole diameter is 6" - go figure). Could this be a problem? The cone is not restricted in any way I don't think?

The original bottom driver is out so right now there's a 5.75" diameter hole in the front baffle. I tried re-installing the original driver (to cover up the hole - probably not the most rigid speaker structure!) but it didn't make any difference.

I've not installed the port tube yet. So there's also a 2" hole in the back.

Could my problem be due to the open cabinet? I'm doubting it. If this driver could not distort in an open baffle design, seems it wouldn't distort here. I'll close up the cabinet tomorrow night to see if that makes a difference. I fully intended to - I just thought I'd give it a quick listen before I finished.

I'd appreciate any thoughts on where I've gone wrong.

Thanks for your help!
Bob

[planet10]

Originally posted by rbclark
so right now there's a 5.75" diameter hole in the front baffle ... a 2" hole in the back.

No bass -- and easily overloaded in that region -- is to be expected. And you do need to quickly get at least 100 hrs on them (face-to-face out of phase with interstaion FM (muting off) is a good way to get them going.

dave

[rbclark]

Originally posted by planet10


No bass -- and easily overloaded in that region -- is to be expected. And you do need to quickly get at least 100 hrs on them (face-to-face out of phase with interstaion FM (muting off) is a good way to get them going.

dave

I guess I was expecting some "missing bass" - but not "overloaded". In hindsight, I don't know why I should expect lower frequencies to just disappear - I guess it makes sense that they sound bad. I'm surprised though that anyone would be happy with this as a full range solution.

What I've got is pretty un-listenable. Is there something I can do to prevent the overloading? Or, are you suggesting that this could be a break-in thing? I'd love to think this will go away with some time.

Thanks for the help!
Bob

[planet10]

Originally posted by rbclark
Is there something I can do to prevent the overloading?

Cover/seal the other driver opening and install your port in the back (i'm guessing 2.25-2.75" long)

dave

[loninappleton]

Originally posted by planet10


Cover/seal the other driver opening and install your port in the back (i'm guessing 2.25-2.75" long)

dave

Dave, others, I have a question here. If he just puts the speaker
back in the hole as a cover is that other driver acting as a passive radiator? It's my understanding that a passive radiator is a speaker frame with no magnet structure.


Rb,

Also for the Fostex driver, start with no internal stuffing. I have the
MLTL design for Fostex 127e with practically nothing inside and I ran it with zilch for quite a while. Give yourself a baseline to start from.

[3-LockBox]

Originally posted by loninappleton



Dave, others, I have a question here. If he just puts the speaker
back in the hole as a cover is that other driver acting as a passive radiator? It's my understanding that a passive radiator is a speaker frame with no magnet structure.

It is, but not just any 6" driver is going to make for a decent PR, especially an old driver. The cone will be too thin, it will act more like an aperiodic port, and not a good one at that. But I wouldn't recommend a 6" radiator either. I would recommend an 8" PR, except I don't know the specs on the driver in question.

Hey rbclark,

I made a fullrange/PR combo and it turned out pretty good, but I used two 5.25" drivers in a .8 3^ft cab (22 liters), in a bipolar mounting, with a forward firing 8" PR (Dayton). If I could do it over again, I'd use a slightly smaller cab. Your's is a good size, I think, for that.

FWIW: some drivers do seem to need break-in (though many disagree, like Bob Brines). I don't know of any driver that will sound good in the senario you just described. The cabinet you're using right now, as is, is neither a bass reflex, or proper open baffle, and a driver would sound better laying in a pillow. You're hearing all kinds of anomilies at once, so don't listen to them that way any more.

If it were me I'd make the botton hole a tad bigger to accomodate an 8" PR, and I'd use the Dayton PR, or any reputable manufacturor PR, but don't think you're going to lop off the magnet of any old speaker and call it good. No. And do not use flat panel PR as they suck (there's a good explanation for why they suck, but for now...). You could maybe use a blown subwoofer, as they usually have nice thick surrounds and treated cones, but unless you can find two exactly the same, I'd just buy the PRs. Daytons can be purchased through Parts Express for a reasonable price.

Keep the tweeter hole in case you feel the need to add a super tweeter (many do), but cover it well. Cover all holes well and make sure the cab is sealed. A PR will not work properly in a leaky cab. Yes, there are pros and cons to using a PR, but sometimes its a matter of taste. I happen to like their sound compared to ports.