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A quite simple bookshelf speaker with the Markaudio Alpair 10.3
A quite simple bookshelf speaker with the Markaudio Alpair 10.3
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Old 5th March 2021, 09:13 AM   #1
h_a is offline h_a  Europe
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Default A quite simple bookshelf speaker with the Markaudio Alpair 10.3

After a long audio absence, I was curious to build a simple vented or closed bookshelf speaker with a fullranger for my office.

I was lucky to get a pair of Alpair 10.3 cheaply from ebay, so my starting point was this simple box which you can find on MarkAudio's website

http://wodendesign.com/downloads/sim...lan-100214.pdf

Now putting a fullranger into a small box without any sort of filter won't give a neutral frequency response as the baffle step is not compensated.

While I respect MarkAudio's attitude of avoiding filters, this simple speaker design is pretty much unlistenable as it is all treble, with little midrange and no bass output - which is exactly what happens when the baffle step is not compensated.

After tinkering, building and listening to 4-5 different filter designs, I settled for a very simple RL-filter which - IMHO - works very, very well giving a neutral, balanced sound. Of course with such a filter one can only burn away energy, so the resulting speaker does not excel in efficiency.

I like the resulting sound a lot and thought I would share it here, so that others can try it too.

A note on bass: this speaker has decent bass output and I'm personally not missing anything in this regard. I know that the measurement might convey a different picture and one might be tempted to further attenuate mid and high range in favor for more bass.

However, my personal opinion is that full rangers should not carry the load of hefty bass output anyway. The required excursion for low frequencies doubles with every octave going down, which means that the full ranger works at least twice as hard at 50 Hz than at 100 Hz. The result is a strong increase in distortion - which can reach 10% for some transducers. If more bass output is needed I would opt to add a subwoofer and cross it with the fullranger at 100 Hz or so.

As the linked, initial filter-less speaker design is called simple bookshelf design, I termed my variant a quite simple bookshelf design.

Enjoy this little fun speaker, Hannes

PS: attached is a periodic white noise on-axis measurement 10cm from the cone away, 50 averages taken. My measurement chain is not calibrated, so values might not be fully accurate but should give an impression.
Attached Images
File Type: png RLv5.png (75.7 KB, 260 views)
File Type: jpg quite_simple_bookshelf.jpg (139.6 KB, 261 views)
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Old 5th March 2021, 09:48 AM   #2
h_a is offline h_a  Europe
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Decrappified my hand-drawn schematic a bit.
Attached Images
File Type: jpg RLv5.jpg (140.3 KB, 260 views)
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Old 5th March 2021, 10:23 AM   #3
Scottmoose is offline Scottmoose  United Kingdom
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Measured 1m response of this design sans filtering below. This was taken a couple of years ago & I don't have any more data -I've lost a fair bit due to an HDD failure (Yes, I know: I should back up ); as I recall it was hard splice to the nearfield @200Hz, & something like a 4ms gate window but don't quote me on that.
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File Type: png Simplereflex.png (9.5 KB, 248 views)
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Old 5th March 2021, 11:03 AM   #4
h_a is offline h_a  Europe
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Hi there,

sorry if I was tipping on your toes here - that was not my intention! Great that you are also active in this forum!

Your measurements look nice - I didn't save my measurements without filter, but they certainly looked a lot different.
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Old 5th March 2021, 11:24 AM   #5
waxx is offline waxx  Belgium
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I suspect you did not run in the driver like is mentioned. It's very sharp when new but run it in for 100h and it becomes balanced.

I did also use it in a bookshelf, and it's a great speaker. I also use a small filter, but even without, when the driver is run in, it's great.

my design (including filter) is found in attachment.
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File Type: jpg 20200721-DSC_0115e.jpg (630.2 KB, 228 views)
Attached Files
File Type: pdf Mark-Audio-Alpair-10M-Slot-Ported-Official-CAD-drawings.pdf (121.0 KB, 38 views)
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Old 5th March 2021, 11:27 AM   #6
h_a is offline h_a  Europe
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I found an measurement of an early filter design where I tried a small bandwidth notch filter - it is not fully without filter, but the filter has only a limited impact in a narrow frequency range.

It can be seen quite clearly that midrange output steadily decreases from 400Hz or so downward. Also there is a strong almost 10dB peak at 10kHz.
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File Type: png oldnotch.PNG (65.7 KB, 120 views)
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Old 5th March 2021, 11:32 AM   #7
h_a is offline h_a  Europe
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@waxx: nice speakers! Interesting you added only a high frequency notch filter!

I have run-in the drivers for 8h or so. Without any run-in, of course, it really sounds scary.

Maybe my units are out of spec or something.
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Old 5th March 2021, 12:17 PM   #8
waxx is offline waxx  Belgium
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No, that is normal with Mark Audio drivers, they use rather special cone material (an airspace type of copper alloy) and a spider that need to loosen up. This is rather standard. Wait untill you're 100h far on the driver to judge like recommended by Mark Audio. They change a lot during that period, and after they do sound very balanced and detailed without being piercing sharp.

The filter i use is really fine tuning, without it it also sounds good after run in.
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Old 5th March 2021, 01:03 PM   #9
h_a is offline h_a  Europe
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Sure, all drivers need some time to settle, but 20h or so is usually more than enough and currently the drivers have certainly 20-30h on them.

100h is an extreme number which is a bit hard to believe, but I'll keep that in mind.
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Old 5th March 2021, 02:24 PM   #10
NOTADOG is offline NOTADOG  United States
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@waxx gorgeous boxes


@h_a I've been shocked before at how long speakers can take to break-in. Stay optimistic.
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