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Small 2-way speakers with linear on-axis and power response characteristics (Scan Speak and SB Acoustics drivers). H&V off-axis measurements included
- Thread starter XMechanik
- Start date
How does the width of the speaker sound? It appears to have fairly narrow dispersion, although very even. I've found some more narrow speakers can often sound a little constrained but I don't have anything quite this narrow in this top to confirm what I feel I may hear.
Also I love your wall of bookshelf speakers I saw on diyaudio.
Also I love your wall of bookshelf speakers I saw on diyaudio.
wineds
Active Member
Can the port be 3d printed? Maybe out of abs or asa?
I don't doubt they can, but I ordered two Monacor MBR-35s from Germany for $26.20 USD, including shipping. Seems pretty reasonable.
wineds
Active Member
That's true but shipping is likely to be a killer for me.
You absolutely don't need that specific port. Any port with an internal diameter of around 4-5cm will do if you adjust the length.
The original build used a very low tuning frequency which necessitated a relatively long port - probably the reason why @XMechanik went with a smaller diameter vent (larger diameter = longer port for same tuning frequency). But this may be contributing to some of the distortion at higher volumes and also results in a depressed response in the 70-150Hz range compared to what you could obtain with a higher tuning frequency.
Either way, just find a port that is easily available for you in that diameter range; it doesn't need to be adjustable if its long enough. Then enter the speaker details (driver model, enclosure volume, tuning frequency and port diameter) into something like WinISD and check what the required vent length is.
Here's an example with a tuning frequency of 57Hz and the original enclosure:
WinISD is limited in that it doesn't automatically account for the enclosure volume taken up by the port - so you'll need to do that yourself by going back and subtracting it, and then checking what the recommended port length is now (it will be longer).
Attachments
I like to use PVC that I flush mount to the cabinet then trim with a round over bit to make a little flare. Not sure how much the thickness of the tube plays into the ports performance but it certainly feels more robust than the marketed speaker ports out there.
- Thread Starter
- #169
Narrowing tweeter dispersion has also some positive effects, it translates into higher DI, which allows to match it with DI of the woofer.
What is DI? Does it have units of measurement?
From the CTA-2034 standard...
Sound Power Directivity Index (SPDI) is normally defined as the difference between the on-axis curve and the sound-power curve, expressed in dB. It is a measure of the degree of forward bias (directivity) in the sound radiated by the loudspeaker. The SPDI is defined slightly differently in this standard because, due to the symmetry in the layout of transducers on baffles, the on-axis frequency response often contains acoustical interference artifacts, caused by diffraction, that do not appear in any other (off-axis) measurement. In such cases the directivity index exhibits irregularities that can have no significant effects on real listening. In this standard the SPDI is defined as the difference between the listening window curve and the sound power curve. For the majority of conventional cone and dome loudspeakers this difference is negligible. However, in highly-directional (e.g., large panel and horn) systems the listening window curve can be significantly different from the on-axis curve so some interpretation may be required. An SPDI of 0 dB indicates omnidirectional radiation. The larger the SPDI, the more directional the loudspeaker in the direction of the reference axis.
Relating this back to Amir's Klippel measurements...
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Thank you. So only a Klippel would be capable of creating this information I guess.
My pleasure. A Klippel is an automated machine for collecting the needed data without an anechoic chamber. Can also be done in an anechoic chamber but they are expensive to build. Finally, as more serious hobbyist do, you can DIY (just with less accuracy and precision than a properly calibrated automated machine).
a4eaudio
Active Member
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@Rick Sykora correct me if I am wrong. The Klippel machine does more than just the acoustic measurements, much of which is pretty hard for a DIYer. (i.e., laser measurement of cabinet vibrations, etc.) HOWEVER, the specific measures in post 172 - Listening window, Early reflections, Directivity Index are all pretty easy to get with a DIY setup. (The Klippel will be slightly more accurate, but a 1/4-1/2 db difference in a few spots between a Klippel measurement and DIY isn't going to matter in a real room at 2 meters.)
Yes, a Klippel potentially has more features but was giving concise response around what Amir has and keeping the content relevant to the context. As for accuracy, a Klippel NFS is notably more capable of measuring bass response considerably easier and more accurately by far than DIY gear. DIY gear can be pretty good but is often limited by the room, and lesser reference and analysis tools than are available with pro gear (like a Klippel).
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There is more than one Klippel machine. The laser isn't normally part of the NFS package and there doesn't seem to be a module for cabinet resonance scanning with the laser.
https://www.klippel.de/products/rd-system/product-brochure-price-lists.html
kimmosto
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- Sep 12, 2019
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Price tag of ca. 100k is the hardest for DIYers. That system should not have too much (or any focus) especially on DIY area where quasi anechoic method is de facto standard due to almost zero cost.
In terms of audible results, MDF will be every bit as good as plywood, assuming you don't cheap out on the MDF.
But please be warned: MDF is nasty stuff. The fine, toxic dust gets everywhere if you aren't set up to control it aggressively. When I do cut it, I wear a serious respirator the whole time and also run a giant ceiling-suspended dust collecting filter for 8+ hours in my shop. The dust still gets everywhere. I've been moving more and more to baltic birch plywood.
My build of these is using plywood, for what it is worth.