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In need of a builder...
- Thread starter BKr0n
- Start date
Nope. Bass horns need long lines. They are inherently big.
- Thread Starter
- #103
Well then I'm out of ideas... maybe @kemmler3D is right and just go 2-way. Honestly, pretty disappointed
I wasn't trying to make something novel, just something that worked. But you can only fight physics so much, and I think I lost this one.
Why? Did you even model the two subs in the enclosure already? Let’s see it’s maxSPL curve in a closed enclosure. It should still manage about 105 dB per speaker at 30 Hz. The question is just how much power it will need.
- Thread Starter
- #105
I could just sacrifice 3db and go isobaric. I haven't modeled anything yet because, despite being able to teach myself CAD, I find vituixcad not so intuitive, so I struggle a bit to use it.
Edit: Also, why simulate yet when I don't even have the math done?
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The simulation will do the math for you. Use WinISD, it’s simple and will work well enough. It’s a 5 min job.
Maybe look for a more suitable woofer? Car audio has many low VAS woofers. Or Dayton UM10 or MX10.
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- Thread Starter
- #107
...the print is very tiny. Before the time of UI scaling eh?
Main reason I went with the L22ROY2 because of the super flat response under 200hz (which is where I was crossing over).
https://www.daytonaudio.com/images/resources/295-458-dayton-audio-rss210ho-4-specifications.pdf this guy doesn't look half bad
Why does everyone dunk on dayton? Functionally speaking, they make pretty good stuff.
Who does?
- Thread Starter
- #109
People who apparently don't know how to read a spec sheet
From time to time over on DIYaudio I see someone complain about dayton. Again, don't know why.Edit: The Seas sub also has an Xmax of 46mm which is kinda bonkers.
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No, it was 23mm of Xmax, two ways, do really 11.5mm. It does have 46 mm p-p Xmech (or 23mm one way), which is respectable, but not exceptional for such a woofer. But anything beyond the 11 mm will distort heavy. The major advantage of the high Xmech is that it can withstand a beating.
terryforsythe
Major Contributor
The below post may shed some light - open the attachment in post #56 comparing the published specs to the measured specs:People who apparently don't know how to read a spec sheet
Introducing Denotiva DIY speakers!
Oh, that's definitely too high for my desired use. Is that after filtering? I was under the impression most woofers lose about 6db when tossed on a typical bookshelf baffle but apparently not? I think I'm missing something here. It depends on how much BSC you implement into the...
audiosciencereview.com
terryforsythe
Major Contributor
I think you have some good ideas. Two 8" woofers may be a little large for a stand-mount speaker, though.Honestly, pretty disappointed
For what it may or may not be worth, here is how I would approach the project, and why:
A. If you can get your hands on a pair of KEF Meta concentric drivers from the Reference series (preferable) or the R series, use those for your midranges and tweeters.
Why:
A1. KEF concentric drivers offer good dispersion both horizontally and vertically.
A2. The midrange acts as a waveguide for the tweeter, providing a good directivity index, and thus good in-room response characteristics.
A3. I have looked into many different concentric drivers that are commercially available. KEF concentric drivers seem to do a better job at mitigating diffraction at the tweeter/midrange interface and the midrange surround.
A4. The KEF Reference series drivers have exemplary harmonic distortion and compression characteristics.
B. Determine the maximum air volume that you have available for the woofers, and select woofers better optimized for that air volume.
Why:
B1. Putting too large of woofers in a small air volume results in poor bass response. You can compensate for this to an extent using DSP so long as you have adequate power and woofers that can handle that power, but the overall level of your DAC output signal is reduced to avoid clipping. Essentially, the more gain you add with EQ, the more the overall gain needs to be reduced. You could add a pre-amplifier stage between your DAC and amplifier, but that will introduce additional noise and distortion. For those reasons, I try to keep the maximum gain of any PEQ filters to be no greater than about 6 dB and I use balanced outputs.
Side note: I handle my large 18" subwoofer differently. It has its own plate amplifier and so much output capability that I am able to set the overall gain for it to -10 dB, giving me 10 dB of range for EQ without running into clipping.
C. If you cannot get the SPL and bass extension you want from woofers that fit into the air volume you have available, consider using a separate subwoofer. If you use a separate subwoofer, consider keeping your speakers as sealed enclosures.
Why:
C1. Using a port or passive radiator adds additional group delay to the lower end of the woofer's frequency range. For me, this resulted in challenges getting good phase alignment, and thus a smooth frequency response, in the woofer/subwoofer crossover frequency range. I plugged my speaker's ports and was able to get better phase alignment. I did crossover a little higher in frequency than my attempts when using the ports, but achieved a better frequency response and tighter bass.
a4eaudio
Addicted to Fun and Learning
Yes, but that is just one example and it was shown that the driver with actual measured TS parameters modeled very closely to the same as with mfg specs.
Historically Dayton and SB Acoustics have a reputation of providing more accurate data sheets than some of the premium brands.
terryforsythe
Major Contributor
It was two samples. Here is the table listing the manufacturer's specifications and the actual measurements:
Can you post a link to the measurements?
a4eaudio
Addicted to Fun and Learning
Ha, I didn't go back and look at post #56...I recognize the color coding... #56 is my post linking to my data at MAC. Look at post #64 in the Denotiva thread to see what little difference it made in practice. Note, I'm not making excuses for Dayton... the new Signature Series is off from the data sheet more than normal and they have had a few other examples where things have been off, but in general they offer a lot of speaker for the money. The RS225 is one of the best value drivers available. But even there, if you are willing to pay 2 to 3 times the money there are better drivers.
terryforsythe
Major Contributor
Thanks for the info. Those are the model predictions, but you are correct, they are not that far off.
- Thread Starter
- #117
There's a few reasons I don't think going with the KEF would be the better choice:
1) Pound for pound, the drivers, even the SP1815, just aren't as performant as the MTM choice. While yes it has the advantage of point source, the mid doesn't perform as well as the purifi driver, and the tweeter doesn't perform as well as the bliesma.
2) While I do realize DSP can compensate for a lot, it still can't compensate for the physical properties of the material. There's no getting around the fact beryllium has higher transient response, and there's no getting around purifi's technological advantages.
3) Frankly (and I hate that I'm saying this), I've heard both in person, and there is a clear audible difference. I've heard the Blade 1 and 2 meta. I've heard quite a few speakers with beryllium tweeters. There is an audible difference between them.
4) Going with the T34B, I have the luxury of a low crossover point for the MTM, which means that, from a design perspective, the main problem with an MTM is mitigated. Additionally, that would also mean those essential bands (500-5k) will be mostly a super quick beryllium speaker.
I went with two because of the benefit of force cancellation, but from the looks of it, that isn't going to happen. Like I've been saying, you really can only fight physics so much. As for the drivers themselves, I went for a 3-way design mainly for the benefit of separating he bands to reduce the chance of IMD.
Zooming out though, and looking at a lot of top shelf designs, there are quite a few that are just 2-way. But this is DIY, so I figure have your cake and eat it too
There's a good chance I may be a bit more mobile in the coming months, so I want to make something at least somewhat portable. Otherwise I would have just made these floor standers with a full D'Appolito WMTMW.
Have you tried any of their reference stuff?
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Um, unless I'm looking at it incorrectly, the configuration in that image is not isobaric.
- Thread Starter
- #120
I widened the clam shell in order to create a place for the volume of air to exit the speaker. The top and bottom would be ported. In an isobaric configuration, that would(should) be enough to balance the equation for Vas. Since I will probably use the daytons instead, I can narrow the clam shell in order to cut down on enclosure size.
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