Read the post I linked.
Does that mean this project is for an active system?
It is the intention for most configurations to have a passive crossover. All configurations could have an active crossover but there may be little interest in an active crossover for some configurations. It will depend on who wants to do what.
Ok, so the project will need a passive xover (which may be ditched in favor of an active filter by some builders).
What's the target for low-frequency cut-off (-3 dB frequency) and max. box volume?
What's the target for low-frequency cut-off (-3 dB frequency) and max. box volume?
The maths is correct but it has to be remembered that the figure of 91dB should be in box in free air, if you want it to represent a speaker at 3 -4m in a room big enough to sit at 3 - 4m.
That is a 97dB woofer on a half space spec sheet or 750w if your woofer is actually 85dB in box after accounting for full baffle step.
Getting that efficiency up enough to not need a lot of power for the woofer at very high costs something. Size or extension.
Unless you are happy to quote half space loudness like many manufacturers do.
Good point. RMS and peak power requirements for typical locations should be added to the list of tasks. Although 1+ kW class D amps are fairly cheap these days I don't think we want to go there for woofers in main speakers.
90 degrees can work with the geometry of a room and it is a popular choice for that reason. It is not practical to hold it all the way down so a frequency limit is usually set.
That depends on who gets involved. I have little interest in passive crossovers and so it would require others with an interest in passive crossovers to get involved with the project.
The target for low frequency extension is sufficient for most music genres for a pair of mains without subs. I estimated that at 30-40 Hz but this, like most specs, is subject to what is revealed by study.
There is a target volume of 75 litres +/- 25 litres. If 110 litres provided many benefits it would be considered but I think this unlikely. I also think 50 litres is unlikely but we will see.
I don't know of any that I would call cheap (but that is a relative term) that would produce a true 1K at very low distortion levels, not the 1% they are ususally rated at. The impedance makes a big difference, most woofers come in 4 Ohm versions which does help with Class D in active setups, but there are a lot of people that love their lower powered amplifiers that could be turned off if the power requirements are significant. Something to consider when chossing the trade offs later.
What home loudspeaker comes near to 1% when driven that 1kW? There’s not much on that on the net. I remember KEF had a white paper on the KM1. Just to give a hunch, that had 4 12” bass drivers.
So you're looking at an affordable DIY loudspeaker that depends on serious money for amps and active xovers?
What I'm looking at is an affordable(ish) DIY loudspeaker and hopefully no costs for amps and signal processing by using what I have already. Doesn't always work out that way and buying new hardware is a temptation I am likely to give in to. What others are looking at will depend on what they value and how they go about their hobby. Active setups are flexible. Of course if one wants to pay DIY prices for hypex modules then things can get expensive but that is a choice.
So is this goup project about designing a speaker for you, or a larger group of (potential) builders?
There are several ways to respond to posts like this but I think it wisest if we let people work things out for themselves.
The person building the first set will (and rightfully should) have a significant voice in what the speaker looks like, how much it will cost, and the difficulty of construction. Getting the first pair built and tested is the most significant hurdle (I think I have said this before). This project has to appeal to Andy first and foremost. Sure it is great if other people want to build a set for themselves.
Honestly, most of us enjoy contributing to the design/test/development/construction process, even if we don't actually build a pair of speakers for our own use. So even if Andy is the only one who builds a set of these, it is still a group project.
Honestly, most of us enjoy contributing to the design/test/development/construction process, even if we don't actually build a pair of speakers for our own use. So even if Andy is the only one who builds a set of these, it is still a group project.
... But I suspect that if there are two different mid-tweeter options, and there is a passive and active version, this project will be built by multiple people...
It seems the basic idea was to use the active filter transfer functions as a baseline to develop a passive equivalent.
Not really it has to appeal to a significant group of people and the design we are working towards should hopefully do this. Not everybody obviously but hopefully enough to reach critical mass for a group project. I will perform some admin, some of the vibration analysis of the cabinet and some of the detailed acoustics in order that what the project is about becomes clear but if after that others are not wanting to get actively involved in the design process I will drop out. A fair few group projects don't work out and it can be wise to know when this has happened.
If it was a project solely for me today it would be an on-wall cardioid design with multiple sub support. Possibly another nice project but not one with as wide an appeal for a group project as a modestly priced domestic midfield monitor with monkey coffin aesthetics.
@andy19191 what is your expected use case for SPL at your seating position? You talk about 80-85db averages in post 1 and 393, with the caveat of listening at 4m, and with 20db headroom for dynamic range. This means peaks at 105db in your seat. That’s loud enough for hearing damage in short amounts of time.
Do you listen that loud in a domestic environment? Or are these intended to be monitors of some sort? Merely curious, and I am not trying to argue that design parameter/goal.
Do you listen that loud in a domestic environment? Or are these intended to be monitors of some sort? Merely curious, and I am not trying to argue that design parameter/goal.
Sorry if my post #413 came across as a rant -- I didn't mean it this way. I am simply trying to understand the scope of the project in this thread started by @andy19191.
I asked a few basic questions about what type of speaker the project is aiming at, and the responses sounded like "my own interests are X and Y, but other people may have different needs and will build a different speaker".
I might be motivated to contribute if this project is about designing something not just for one guy, but for a group of potential builders. This would require a clear(er) view on who might build this speaker, and why, and what their needs/constraints might be.
I will say it one more time: we need a clear set of design targets that will tell us what to (not) do.
I asked a few basic questions about what type of speaker the project is aiming at, and the responses sounded like "my own interests are X and Y, but other people may have different needs and will build a different speaker".
I might be motivated to contribute if this project is about designing something not just for one guy, but for a group of potential builders. This would require a clear(er) view on who might build this speaker, and why, and what their needs/constraints might be.
I will say it one more time: we need a clear set of design targets that will tell us what to (not) do.