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I have a general idea of how I want them put together. My goal is to remove, as much as possible - any cabinet induced resonances.I'm interested in mounting the drivers in an acoustic suspension configuration versus the ported design they are in now. I am certainly interested in hearing opinions on this - especially since my secondary goal is to maximize the speed and attack of the woofer.
Though the bass on acoustic suspension designs sound better to me - I am curious what this will do to distortion levels in the midrange.
Would this be screwing around with whole of the midrange's sonic signature - or would it be miniscule?
I also don't know...
...how big the internal size of the cabinet needs to be. I have a sub and so - they do not need to go that low.
What do I need to know about the woofer in my RB5's?
How will this effect the sensitivity of the speaker?
Love to show my ignorance...
anyone up to continuing my education?
thanks
Dean,
Just a word of caution. If you build your own speakers, be advised that you will never look at speakers the same way. Also, most of the threads at the Speaker Asylum will begin to appear uninformed, irrelevant, or just downright silly.
!
In general a woofer who's T/S parameters are set up for reflex, will require a smaller enclosure than if reflex. The cost of this is less extention and efficiency.So for grins you can do these reverseable things.
First, plug the port/slot with foam/cloth/socks. Try it out. It will more likely be a bit more boomy/chesty vocals than before.
If this seems like the direction you wanted to go, then remove the driver, this will give you access to the box. Add some "stuff" to the inside to reduce volume. Things like wood blocks, bricks work nicely for testing purposes. Keep the volume removed to less than 25%, plus keep port/slot sealed with those foam/cloth/socks. Listen again and see if this is where you want to go.
Bottom line is this will not be optimal since the driver is set up for reflex, but just in case it was a borderline reflex/sealed driver, you may find some success. You may find that the unit will sound thin and more bright than before.
Anything else than attempts above will require measurement equipment to determine if you have a hope of getting what you want out of the driver you have.
ignore the second one at the bottom of the post. I inadvertantly copied it to the new spot instead of moving it.Should have finished my coffee first before posting.
> > Bottom line is this will not be optimal since the driver is set up for reflex, but just in case it was a borderline reflex/sealed driver, you may find some success. You may find that the unit will sound thin and more bright than before. < <This statement says alot about my level of ignorance. I never knew the driver was optimized for a certain box design. I was hoping to utilize the same driver because its so darn quick. I thought if I acoustically suspended it - the driver would be under better control. However - it turns out that I might be wrong to assume that this is even what would happen.
Last night I was even thinking that a acoustic suspension design might even be more prone to resonances because the air is somewhat 'trapped' in the box - and the increase and decrease in internal pressure would 'rap' against the cabinet - as where in a bass reflex design the air escapes - which might minimize cabinet induced artifacts.
At any rate - your suggestion that plugging the port would probably increase 'boominess' seems to bear out my suspicions about this - or does it? What causes the increase in 'boominess' or 'chestiness' in the vocals? The increase of cabinet induced artifacts? Or the effect the 'plugging' of the hole has on the driver?
The circumferance of the port on the RB5 is huge. While thinking about these things last night I put on a aggressive CD and put some juice to them. I was surprised to find that the cabinets were not vibrating as much as I thought they should be. The most vibration was actually felt at the binding posts where the speaker cables attach (I had actually discovered this fact a couple of weeks ago when moving my cable arounds my rack).
At any rate - your suggestion that plugging the port would probably increase 'boominess' seems to bear out my suspicions about this - or does it? What causes the increase in 'boominess' or 'chestiness' in the vocals? The increase of cabinet induced artifacts? Or the effect the 'plugging' of the hole has on the driver?
Since what you suggest would not be optimal - I will probably just leave them alone. I'm a bit of a perfectionist - and it would seem the best thing to do is learn a thing or two and start from scratch.
Thanks for your valuable input Edp
Dean,
I'll help all I can -- I have a pretty good knowledge of the basics of loudspeaker design. I also know where to go when the questions get hard! :)Actually this has been my hobby for years but I've been out of electronics and don't have access to a woodshop myself, so I'm just now getting back into it. I'd love to help, if only for the real-world education.
sharve@acxiom.com
!
K:Where do I begin? Acoustic suspension woofers can offer what is termed "tight" or "fast" bass. The tradeoff is that acoustic suspension designs tend not to go as low as bass reflex speakers, certainly not as low as a bass reflex speaker the same size. HOWEVER, acoustic suspension can be boomy. The key is the total Q of the driver in the enclosure. Acoustic suspension speakers can be tuned to be transient perfect (0.5Q) all the way to boomy (just about anything over 1.0Q). The problem you fact is that the required size of the enclosure for your woofers will depend on both its Thiel/Small parameter and the desired Q. If you stick with the box you have, you will be VERY limited in your choice of drivers. You will have to find a driver which works for the desired Q in your existing enclosure. This has nothing to do with the drivers presently in the box.
As for the box, there are materials which can break up the back sound wave to some degree. For damping there are compounds like Black Hole 5. But you will be limited by the box which probably isn't terribly well made.
If you are serious about this, do it right. First, you need to know a lot more about speaker design than you do now. Get Dickason's Loudspeaker Cookbook which is the DIYer bible. All the equations you need are in this book.
Next you have to decide to build your own cabinet or have someone build it for you. Acoustic suspension speakers are some of the easiest cabinets to design. This way you can build the cabinet for the woofer you select, not the other way around.
Hope this helps.
are you reffering to infinite baffle/closed box or more something like Naim's NBL (nested box loudspeaker)..
If you are serious about this, do it right. First, you need to know a lot more about speaker design than you do
now. Get Dickason's Loudspeaker Cookbook which is the DIYer bible. All the equations you need are in this
book. -I have too agree on this..
And keep in mind that is prefectly possible to do everything right (equation wise) and still end up with something mediocre..some things seem to defy measurements (well we are just not measuring the correct parameter probably)
I have heard some designs using all top of the line Scanspeak and X-over parts which sounded pretty awfull nonetheless.and the other way around too, for instance the Wilson Audio's use very common drivers but sound good.
Or try www.partsexpress.com
Joost,the Wilsons use in the Maxx/Watt5/6 also Scanspeak units- thatīs why some people donīt like them-stiff material means resonances.
What is hardly talked about in these speakerbuildingbooks, how do resonances affect the sound, and should I not really use membranes which have no resonances at all.say you damp a resonancd 6dB or something; it will still be a resonance, only 6dB less loud.
Ciao
Philipp
P.S.: What we had in university(theory- a short tune is noticable only as sound; gets it longer the exact tune starts to be recognized, and gets even a bit more intensive with a little more time, psychoacoustically, while being of the same objective loudness. We did not talk about quantities..
In a way, that means any resonance will change the music in principles of human understanding.BTW the Seas river you can order from Zalytron, Joost, like in the Watt2, has little critical resonances, while the Scan Speak8545 has a resonance (at2600Hz) Itīs not really a matter of regular or not- in a way (e.g.bass)the scan speak is special, too. But as Thorsten says, quality is no matter of price;-)
I ordered two seas drivers ($40 shipping gulp,..).. I like paper cones.. (thanx for the link)seas exels (metal cones...ever wonder why they build bells out of metal and not paper????jeez do they ever learn?) are really bad in that respect and give me a headache..
Joost,the Wilsons use in the Maxx/Watt5/6 also Scanspeak units- thatīs why some people donīt like them-stiff material means resonances.
What is hardly talked about in these speakerbuildingbooks, how do resonances affect the sound, and should I not really use membranes which have no resonances at all.say you damp a resonancd 6dB or something; it will still be a resonance, only 6dB less loud.
Ciao
Philipp
P.S.: What we had in university(theory- a short tune is noticable only as sound; gets it longer the exact tune starts to be recognized, and gets even a bit more intensive with a little more time, psychoacoustically, while being of the same objective loudness. We did not talk about quantities..
In a way, that means any resonance will change the music in principles of human understanding.BTW the Seas river you can order from Zalytron, Joost, like in the Watt2, has little critical resonances, while the Scan Speak8545 has a resonance (at2600Hz) Itīs not really a matter of regular or not- in a way (e.g.bass)the scan speak is special, too. But as Thorsten says, quality is no matter of price;-)
By acoustic suspension I mean sealed. Sealed enclosures have a number of advantages for the first time speaker builder: 1) there are fairly forgiving of minor errors; 2) construction is relatively easy; and 3) the equations are so straightforward that you really don't need any speaker modelling software.But you do have to do some study(John Murphy has some excellent discussions at his website www.trueaudio.com). Excellent parts like top of the line drivers will not overcome a poor design.
!
Old Colony Sound lab (http://www.audioxpress.com)or
Amazon.com
Loudspeakers The Why and How of Good Reproduction
by G.A Briggs - available from Old Colony.
It was written in 1948. All the basics are there.
The book was a good intro to speaker building for me.
I find the math in "The Cookbook" overwhelming.
Not a reflection on the book, but of me.
I should have spent less time smoking dope in school...Fred Griffith
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