No one does that.
Well some do and it's not the worst idea. The point was to show the differences. Those will be somewhat similar for flush/non-flush mounting on a smaller baffle, but there will be additional diffraction effects and eventual other reflections. I clearly stated that those effects will probably be way stronger.
No, my point was to show what I have done and offer my results to you. Didn't want to bother you, sorry if I did.
Comparative measurements are usually best when you eliminate irrelevant distractions.. yes?
I don't believe you - that's a tweeter response on a flat baffle, with no other drivers nearby. No-one does that. Where's the midwoofer?
You know - the thing (even if flush mounted) that has a rubber surround that pokes up, and then a great big cavern of cone?
I don't dispute the result, but I feel its out of context - not least because we put the mid as close as we can to do our best to approximate a point source and avoid interference effects. (I've thought about a flush mounted system and its entertaining, but while finding the appropriate back volumes is hard, avoiding the whole wall resonating is tricky at best. Even so - midrange surround and cone - how is that not having an effect?)
My understanding is that we try to understand what is irrelevant?
Suppose you have a +10/0/-10 effect, and a +5/0/-5 effect, and a +2/0/-2 effect.
Overall you have a +17/0/-17 effect combo with a lot of in-betweens.
My concern is that we may have a +2/0/-2 effect, that is measured and graphed, on its own.
Its not invalid, and the measurement is good, but it may be a minor effect. Its not sensible to consider it without the +-10 and +-5 effects, especially if it is connected to them in some way.
Each of us get to decide (for ourselves) what to do with this kind of information. At least this one is measurable 😀.
I know. But you said that people do this. Who puts a tweeter on its own on such a large flat baffle, unless their only intent is to measure its response without interference?
In practice, we have other issues making actual loudspeakers. I'm not disputing that the data is valid or interesting.
The issue is what are the dominating (or even interfering) issues, for making loudspeakers.
Context changes from project to project. In fact, if I make changes today because of what I learn, then it is already out of context. Next project it does nothing but get in the way.
I shouldn't have to explain this.
Besides, if instead of two comparative plots I just handed you a single polar plot with everything on it.. what context would you have then?
On the general theme of 'what puts people off DIY', here's what deterred me. I've always built other peoples' designs, so driver selection, cabinet and XO measurement/voicing isn't an issue.
Geoff
- materials cost and availability: very few companies in Melbourne offer a precise enough cutting service for MDF or ply: I only found three; e.g Bunnings only offers plus or minus 5mm, hopeless;
- driver choice: only five brands of driver are readily available in Oz, which limits project choice
- making a good looking cabinet with all that involves, e.g. driver recessing, finishing, difficulty of construction;
- soldering and connecting the XO components and driver leads;
- related to point three, Spouse Approval Factor. This influences cabinet size, room placement and finish.
Geoff
dave
I recently read that this classic Olson chart is a sim...not from measurements. Do you know if that's correct?
If it is a sim, I don't really doubt its ballpark and smoothed out representations....
...but i do get dismayed how a set of sims like this can become accepted truth...
If it's from measurements, hooray !!
None, beyond a data point that is as good as the definition of the measurement context. Its a data point though.
Its easy to find a crapload of studies and they are all valuable.
But can you answer the original question?
Is it a big deal, compared with other issues - say:
- cabinet solidity and surface resonance
- cabinet dimensions and internal resonances
- cabinet edge roundover and driver placement relative to edges
- crossover component 'quality'
- crossover phase response re LR vs odd order and a narrower phase alignment
- crossover point vs no crossover and give up tweeter 'niceness'
- crossover at midbass high vs tweeter low - we have more choice these days
- cross high and retain more single driver and sacrifice power and directivity, or vice versa
- wideband vs mid/tweet with crossover (on the fence, finishing a B80/RS225 WAW)
There are more - I'm even assuming a reasonably smooth and flat response that doesn't ask for excessive notching.
We are better informed with computer models these days, but what sounds good?
I'm not asking whether these effects have an effect - they all do - but how to prioritise? Especially in my case as someone that is not a great woodworker. I'm hands up on this, but I bet I'm not the only one.
Having some understanding of which issues are dominant would be helpful, IMO.
Then we (I) can be guided as to how to address them: I do not believe that they are all equal.
That's right, they aren't all equal. If you could priotitise them then you could give every issue fair and reasonable consideration. That is the optimum approach.
Some of the things you list are a matter of degree. Some are complex and some are simple. Some have obvious disqualifying issues that we could use to dismiss them, and some don't. The conditions of diffraction audibility are complex.. however it is one of those things where if you pursue it wherever you can see it, you can get good results.
It's also something that is more of an issue at higher levels. Therefore, all diffraction will become an issue at some level. Sometimes it will add harshness that appears higher within the dynamic range of a level you set, thereby causing you not to want to turn up your speaker beyond a certain level. Do you ever feel that cringe?
Some of the things you list are a matter of degree. Some are complex and some are simple. Some have obvious disqualifying issues that we could use to dismiss them, and some don't. The conditions of diffraction audibility are complex.. however it is one of those things where if you pursue it wherever you can see it, you can get good results.
It's also something that is more of an issue at higher levels. Therefore, all diffraction will become an issue at some level. Sometimes it will add harshness that appears higher within the dynamic range of a level you set, thereby causing you not to want to turn up your speaker beyond a certain level. Do you ever feel that cringe?
I've read that it is, and it also looks that way. Perhaps not a sim as we might do with a computer, but a classic pencil and slide rule calculation.
It is measured. Tools were a bit cruder but he had a very nice anechoci chamber. The plots are analog (ie hand drawn).
He measured many many many things.
I can’t imagine doing the sims in the mid 40s with paper, pencil, and a slide rule.
dave
How soon we forget. Many procedures and practices have advanced since computer/technology have come into real use.
As was said above, we can discuss these ideas one at a time and conclude that most likely they are additive, though not in proportion.
As was said above, we can discuss these ideas one at a time and conclude that most likely they are additive, though not in proportion.
Like many others, I used to do crossover simulation in the '90s using pencil, paper, a hand calculator and tables of response and impedance magnitude and phase, which I later used as what we now call frd and zma files.
It used to take me a weekend to make a few adjustments which I could now do within minutes.
Felt on the baffle - (with clean cutouts for the drivers) can look nice and probably hide some sins which would occur without the felt for drivers just sitting in non-recessed holes.