Basic rules for speaker building

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#21
The basic rules........????

as dave said, READ the Loudspeaker Design Cookbook.

of particular note in this case is (from 5th edition) page 86 section 6.30: re driver separation.

" the further apart you place the drivers, the more complex the interference patterns become......."

sort of a quote "for practical purposes the maximum distance apart should be equal to the wave length of the cross-over frequency"

ie:.......... with the P17 and D25, you really should have the drivers as close together as you can !!
This is in fact a VERY GOOD RULE for any tweeter/mid combination. !!!
 
#22
Bricolo said:


1/1.618 is also the best position for your tweeter (internal position) to avoid standing waves
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I think I should correct your understanding on this also if that's ok..

yes the ratio 1/1.618 is possibly a good position for the tweeter in the horizontal, but this is to do with spreading out irregularities caused by edge diffraction, and nothing to do with internal standing waves. The baffle simulator by Paul V at the FRD consortium will help determine the best position for the tweeter relative the the edges, and this best position may or may not be in the ratio mentioned above.

The internal ratio of the cabinet dimensions is what spreads out the internal standing waves, the wadding inside the cabinet helps subdue any internal waves. non-parallel sides also helps spread out any standing wave effects.

Hope that helps....
 
#24
" ie:.......... with the P17 and D25, you really should have the drivers as close together as you can !!
This is in fact a VERY GOOD RULE for any tweeter/mid combination. !!! "

I believed this to be the case when I was initially designing my towers. After looking through the simulations it appeared that the diffraction due to the baffle became far more significant than interference. I moved the drivers all around in simulation software and finally got a bearable and what I think is fairly attractive layout.
 
#27
Hi all...this seems like as good a place as any to post my question.

But first...let me say that I had just found this site a couple weeks ago...wish I would have found it a year or two ago 😉


My question is...how do you properly damp a sealed bass enclosure? What materials are ideal? There is bracing directly behind the woofer...should I do anything with this?

What I had planned to do (so far) is to line all sides, except the front, with either r-19 or a dacron material.

I have searched the archives...and found that most of the questions and answers dealt with a vented box. The cabinet is a 6cuft sealed enclosure braced well. It will hold a 15" woofer. The midrange/tweeter cabinet is totally separate from the woofer enclosure.

thanks for your help...take care>>>>>
 
#28
sealed subs.....

IMO it is best to glue some damping material to the insides of the cabinet. Carpet underlay is sort of ok, but there are of course more expensive and better substitutes. This helps damp cabinet resonance.
Then fill the whole cabinet , leaving room for the driver, with either dacron or fibreglass or similar.

Question about the brace, is it just a cross brace, in which case shouldn't be a problem
 
#30
Some of these things are just too context sensitive to have a rote answer, but i will stab at/generalize on some of em

-magical numbers, those L/D/H ratios that give best results (are thos internal dimantions ratios, or external ones?)
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For the inside irrational numbers. Like the golden number or sqareroots of prime numbers -- there are an infinite number of them. And since this question is usually related to rectangular boxes -- avoid rectangular boxes.[/QUOTE]

-distance between a tweeter and a midrange (or midbass)
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In general the closer the better ignoring diffraction effects.

-time alignment/accoustical centers alignment
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a huge can of worms. From a purely easthetic view it would be nice to have them aligned, but once the drivers are mounted on a baffle physically offset from each other, even if they are "time-aligned" this is really only the case for only a small subset of the space you might listen in -- move your head and poof (one of the reasons i like "mostly-full-range systems)

-optimal height for tweeters/midranges/woofers
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In general, tweeters, midranges at ear level at your listening position, woofers near the floor (depends on XO here)

-bafle step compensation
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This one is covered in some detail in the Wiki

-standing waves
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The worst ones are usually in your room. See item 1.

-edge rounding
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Unless very large their prime purpose is to keep you from hurting yourself on a sharp edge.

dave
 
#31
Re: Re: Basic rules for speaker building

thanks Dave 😉

"avoid rectangular boxes"
Will be difficult, and I think it's the same for many people. That's why golden numbers exist :nod:

"tweeters & midbass at ear level woofer on the floor"
and for a 2 way? both at ear level? (tweeter on the top, midbass on the top, does this have an influence?)

are rounded edges so unusefull, in terms of sound quality, diffraction... ?
 
#32
Re: Re: Re: Basic rules for speaker building

Bricolo said:
"avoid rectangular boxes"
Will be difficult, and I think it's the same for many people. That's why golden numbers exist :nod:
Click to expand...

Keep in mind that a tapered TL may be a rectangle on the outside but isn't on the inside.

"tweeters & midbass at ear level woofer on the floor"
and for a 2 way? both at ear level? (tweeter on the top, midbass on the top, does this have an influence?)
Click to expand...

It influences the way that the XO tilts the vertical lobe -- again i like to have the XOs out far enuff that the ear tends to be insensitive to them.

are rounded edges so unusefull, in terms of sound quality, diffraction... ?
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You need to be talking inches -- like 2-6 inch radius -- to start having significant effect.

dave
 
#33
Re: Re: Re: Re: Basic rules for speaker building

planet10 said:


Keep in mind that a tapered TL may be a rectangle on the outside but isn't on the inside.



It influences the way that the XO tilts the vertical lobe -- again i like to have the XOs out far enuff that the ear tends to be insensitive to them.



You need to be talking inches -- like 2-6 inch radius -- to start having significant effect.

dave
Click to expand...
OK for the TL, but it won't avoid standing waves parallel to the bafle, the others will be avoided

where can I fond more information about this lobe "concept", and also vertical/horizontal response, polar pattern... ?
 
#36
Re: Re: Re: Re: Re: Re: Re: Basic rules for speaker building

Bricolo said:

... and for my 2nd question, on my previous post?
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Give me a couple of months, and I will have a website up that is on exactly this topic. I am just learning Flash, for interactive simulations and Dreamweaver, along with everything else in my life, so it will be coming, just don't hold your breath!
 
#37
Re: Re: Re: Re: Re: Re: Re: Re: Basic rules for speaker building

pinkmouse said:


Give me a couple of months, and I will have a website up that is on exactly this topic. I am just learning Flash, for interactive simulations and Dreamweaver, along with everything else in my life, so it will be coming, just don't hold your breath!
Click to expand...


but I want my speakers to be finished in 2 months 🙁
 
#38
Hi Dave....

there was a recent discussion on MAD about edge rounding. many guys who one would say were "reliable" have noted a change in depth of imaging with even 3/4" round edges.

I myself have done direct comparisons with 2 pairs of speakers exactly the same except for the 3/4" round over.
A mate of mine (who i would say had the closest thing to 'golden ears' I know of,) nlistened to them AB without any idea what to expect.
He almost immediately commented on the different, deeper and more precise, sound stage.
 
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