Peerless 3" computer speakers

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Hi All

I bought a pair of Peerless 830987 drivers on a whim when i spotted them on ebay.

Spec here:

https://www.tymphany.com/wp-content/themes/pathfinders/cache/pdfs/PLS-P830987.pdf

I quite fancy making some little speakers for my PC at the office.

Ive plugged the numbers into WinISD (i used this when i fiddled with speakers years ago) and i get a strange response whatever i do.

Since these arnt going to create any sort of reasonable bass anyway, how much of an impact will the box design make?

the biggest i would want them physically, works out about 2 litres (0.07 cu ft) If i halved that, would it really make much difference?

Usage is just regular PC usage, youtube videos, bit of music etc.

Any thoughts?

Cheers
 
Hi Mike

Thanks for that, ive been on that page but hadn't spotted that.

Optimum Cabinet Size (determined using BassBox 6 Pro High Fidelity suggestion)
Sealed Volume 0.1 ft.³ Sealed F3 98 Hz
Vented Volume 0.22 ft.³Vented F3 59 Hz

the sealed option comes out at about the right sort of size. 0.22ft3 will be a bit bigger than i'm looking for.

I may play around with the dimensions though and see if i can make the ported design work, if you think its worth trying?

Thanks
 
I would try it if it looks like it will work for you. Those dimensions are only optimum, so smaller might work for what you want, especially if you plan on adding a subwoofer. If you wanted to go with something tall that you could set on each side of your desk, you could look at the Cyburg Needle or the TABAQ.

There is quite an involved thread on this forum concerning the TABAQ.

(Turbo) Electronics: Cyburg's Needle

http://coolcat.dk/bjoern/TABAQ_TL_for_TB.pdf

Mike
 
Thanks

Playing around with the dimensions, 2.5 liters (just under 0.1 cuft) is about the largest i could go for this project.

Those links look like cool projects, but its not what i'm looking for right now.

So looking at WinISD below, the blue trace is sealed, the red is tuned to 60Hz, and the green to 75Hz.

Ive chosen 22mm for port diameter, which should fit in the box ok for both examples.

jCpAzPj.png


Unibox gives me a similar shape:

l9NNl90.png


would i notice this lumpy response? is it worth it to have a lower bass extension?

These will be used either side of a PC monitor at TV volume largely... perhaps a bit more when i'm in the office on my own.

Thanks
 
I'm thinking the lumpy response might not be very noticeable since it's only slightly more than 3dB max. If these will be close to a wall, that might help. If they are going to be more than a few inches from the wall, you might want to look into a baffle step correction (BSC) filter. That might also help smooth the lump.

Loudspeaker Diffraction Loss and Baffle Step Compensation Circuits

Mike
 
Considering it's a pretty small driver, I'd probably be happy with sealed f3<100Hz, which is achieved here.

Such a high-Qt driver in a vented box will always be somewhat lumpy in low-frequency transfer function. In your case, the 150Hz hump is a sign that the enclosure is simply too small. The lower kneepoint is the vent's contribution, which can be smoothed out to a certain extent if you play with the various damping and leakage parameters (Ql, Qa, Qp), but it's then often a trial and error process to reproduce the exact effect in a real enclosure.
 
I'm thinking the lumpy response might not be very noticeable since it's only slightly more than 3dB max. If these will be close to a wall, that might help. If they are going to be more than a few inches from the wall, you might want to look into a baffle step correction (BSC) filter. That might also help smooth the lump.

Loudspeaker Diffraction Loss and Baffle Step Compensation Circuits

Mike

I think it'll be the other way around. The lumpy response will mitigate the baffle-step to a certain extent if away from walls, but likely sound boomier the closer it is to other room boundaries.
 
Considering it's a pretty small driver, I'd probably be happy with sealed f3<100Hz, which is achieved here.

In your case, the 150Hz hump is a sign that the enclosure is simply too small...

Yes, the enclosure is too small really, but its a compromise (perhaps too much) because thats the max size i want to box to be.

the advantage of going sealed, is that i can drop the size of the enclosure even further, to say 1.8 litres, without a huge effect on the response... want to avoid a subwoofer though.

I have some rough boxes from an earlier project that i could make some new front panels for, i'll dig them out and see what volume they are...
 
frugal-phile™
Joined 2001
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This driver has a high Q so you will get a bump in the bass even in an infinite baffle. The way to deal with that is usually an OB, where the leakage around the sides counters the rise (but the large size needed is impractical) or an aperiodic enclosure where an attempt is made to damp the peak.

Certainly a vented box is not a good idea.

Start with the largest sealed box you can live with. You might like the bump, but if you find the underdamped response not to your liking you can start drilling some holes in the back and damp those holes. This is very much a cut and try process so go slowly. You can use GMs clik test or measure for maximally flat impedance curve. Or just listen.

EQ is the other option, but i dont think as effectove as an acoustic fix.

This is a picture of one of the most well developed aperiodic speakers i know of. It gives some indication of the approach.

103932d1205046585-aperiodic-vents-perkinspr-2-sm-gif


dave
 
So i did some listening last night. i found some cardboard boxes (i know) that were similar in size to what i was looking at, a bit deeper though and due to the fact that its cardboard, the volume is bigger, about 3.8 litres ish.

They sounded pretty nice. not a lot of low end, as expected, but plenty of detail, and nice to listen to at low levels. worth persisting with.

The TABAQ looks like a floor standing design? unless there is another version? I'll do some research...

thanks
 
I did a simulation of the speaker in a 0.1Cft (2.8L) box with baffle step and diffraction. If you are close to a wall then it will fill the bass back in a bit. The baffles step more than compensates for the peak in the response in a 2.8L box. but it means the mid will be elevated reference the bass by approx. 5dB.


I will see if I can work out a simple correction filter.
 

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This is a fully compensated design if place close to a wall the bass might be a bit much.


I have taken the box and baffle simulation merged them with the responses from the data sheet to provide simulated in box measurements and then applied a correction network made up of a bass shelf with a resistive component to level if out followed by a capacitive resistive element to lift the response back up after the baffle diffraction hump.


Below are the uncorrected merged data, the filtered corrected response and the filter components.
 

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