I have been watching the forum for years and recently unloaded all of my audio equipment in hopes of doing something more interesting in the DIY space.
I am most interested to build the following first:
1. Near field monitors from a single full-range driver for my computer, est. distance from my ear would be 30" and positioned on top of my monitor. I have no desk space for them so they will be mounted pointed slightly downward towards me.
2. Limited volumes due to it being for use during my workday and in a small room, about 9x9'. Thus, I want to have the 'loudness' effect at low volumes whereby bass is present without increasing the power input.
3. Thus far focusing the efforts on using a MarkAudio 7ms.
4. The box cannot be any bigger than about 5L due to the mounting requirements about the monitor which is about 12(w)x4(h)x8-10"(d). I am expecting them to be longer horizontally and rectangular.
I have run through some simulations but have limited experience. Thus far they seem to be telling me its going to be hard to get a low bass frequency in that size. The best seems to work out with a tune around 70-80hz.
I have been considering a transmission line design and would be very interesting to hear the difference they may make vs a standard port.
I would appreciate any opinions on the possibilities of the objectives and perhaps some help on design options that fit or someone to tell me that there is a better driver fit or that I am out of my mind, at which point I will want to try even harder to be creative with this need.
I am most interested to build the following first:
1. Near field monitors from a single full-range driver for my computer, est. distance from my ear would be 30" and positioned on top of my monitor. I have no desk space for them so they will be mounted pointed slightly downward towards me.
2. Limited volumes due to it being for use during my workday and in a small room, about 9x9'. Thus, I want to have the 'loudness' effect at low volumes whereby bass is present without increasing the power input.
3. Thus far focusing the efforts on using a MarkAudio 7ms.
4. The box cannot be any bigger than about 5L due to the mounting requirements about the monitor which is about 12(w)x4(h)x8-10"(d). I am expecting them to be longer horizontally and rectangular.
I have run through some simulations but have limited experience. Thus far they seem to be telling me its going to be hard to get a low bass frequency in that size. The best seems to work out with a tune around 70-80hz.
I have been considering a transmission line design and would be very interesting to hear the difference they may make vs a standard port.
I would appreciate any opinions on the possibilities of the objectives and perhaps some help on design options that fit or someone to tell me that there is a better driver fit or that I am out of my mind, at which point I will want to try even harder to be creative with this need.
I use Fountek FR88Ex drivers in a small sealed enclosures of around 1L with a DSP based Linkwitz Transform to get down to 40 Hz at moderate volumes in my small room. It depends on what you like to listen to, I guess, maybe not so good for reggae or drum ‘n bass. The beauty is that if you run out of displacement on the driver its easy to adjust the DSP to trade SPL for bass extension.
Andrew
Andrew
IMO, for desktop use sealed + EQ is the way to go. You don't need much SPL, but you do want LF extension from a small box.
I'm using a pair of Kef eggs (HTS3001SE, ports blocked) and am currently flat to 35Hz. It's easy to push them too far if I crank up some dubstep, but they make me happy so far.
You can use Equaliser APO to EQ the signals leaving your computer.
Chris
I'm using a pair of Kef eggs (HTS3001SE, ports blocked) and am currently flat to 35Hz. It's easy to push them too far if I crank up some dubstep, but they make me happy so far.
You can use Equaliser APO to EQ the signals leaving your computer.
Chris
Check out my plans - something similar planned with small drivers for desktop use:
Nothing built yet but plans looking pretty solid:
Using DSP with full range
Building just started so hopefully they will be ready in 2-3 weeks for listening & measurements. Final amp with EQ will arrive later but I will manage with a simple inductor crossover and 1.5 way setup until then.
Nothing built yet but plans looking pretty solid:
Using DSP with full range
Building just started so hopefully they will be ready in 2-3 weeks for listening & measurements. Final amp with EQ will arrive later but I will manage with a simple inductor crossover and 1.5 way setup until then.
Thanks for the input thus far. I am trying to determine if the Alpair 7.3MS or 10's are what I should be using but they seem to all require a large amount of volume.
How much can DSP/eq software account for a lack of box volume? Is it just about boosting frequencies and does it have a negative effect on quality?
How much can DSP/eq software account for a lack of box volume? Is it just about boosting frequencies and does it have a negative effect on quality?
They'll tend to ask for a fairly large ported volume. Sealed should be considerably smaller.
With regards to EQing sealed boxes, it goes like this:
As you make a sealed box smaller, you lose efficiency at low frequencies (by "low frequencies, I mean below the system resonance). This is because the air spring inside ends up stiffer, restricting cone movement.
If you put more power in there (by using EQ to tell the amplifier to push more power at those frequencies), you can overcome this lack of efficiency.
That can only go so far, though. If you were to literally just cover the back of the cone (and make a closed-back midrange), you'd have an incredibly small sealed box with very very low efficiency. It would need a LOT of power to get the cone moving.
When dropping a lot of power into a speaker, there are two effects:
- Heat build-up
- Motor-borne distortion
The former is a function of the average power level being delivered. Remember, +3dB of EQ means 2x the power delivery at that frequency. If you're using a tiny sealed box and playing some dubstep with constant full-scale sine waves, your driver is likely to get hot, which can lead to failures.
The latter is down to individual motor design. The fact is that any current flow introduces some distortion, but it's a matter of how much we're prepared to accept.
As a rule of thumb, if your simulations suggest you'll be exceeding the driver's long-term thermal power handling in order to get to Xmax, I'd make the box bigger.
The smallest box recommended by that rule would be where Xmax and Pmax are reached simultaneously.
If in doubt, larger cones mean less excursion is required for the same output, so that's where I'd go.
Chris
With regards to EQing sealed boxes, it goes like this:
As you make a sealed box smaller, you lose efficiency at low frequencies (by "low frequencies, I mean below the system resonance). This is because the air spring inside ends up stiffer, restricting cone movement.
If you put more power in there (by using EQ to tell the amplifier to push more power at those frequencies), you can overcome this lack of efficiency.
That can only go so far, though. If you were to literally just cover the back of the cone (and make a closed-back midrange), you'd have an incredibly small sealed box with very very low efficiency. It would need a LOT of power to get the cone moving.
When dropping a lot of power into a speaker, there are two effects:
- Heat build-up
- Motor-borne distortion
The former is a function of the average power level being delivered. Remember, +3dB of EQ means 2x the power delivery at that frequency. If you're using a tiny sealed box and playing some dubstep with constant full-scale sine waves, your driver is likely to get hot, which can lead to failures.
The latter is down to individual motor design. The fact is that any current flow introduces some distortion, but it's a matter of how much we're prepared to accept.
As a rule of thumb, if your simulations suggest you'll be exceeding the driver's long-term thermal power handling in order to get to Xmax, I'd make the box bigger.
The smallest box recommended by that rule would be where Xmax and Pmax are reached simultaneously.
If in doubt, larger cones mean less excursion is required for the same output, so that's where I'd go.
Chris
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