About directivity, it is measured in a large anechoic chamber, so accuracy below 500Hz is way better than amateurs can do.
Most 6" coaxials have more directivity. Sica 5.5 might be very good, as well KEF Q100/150 drivers.
Here another (merged) measurement of similar G2 https://www.audiosciencereview.com/forum/index.php?threads/genelec-g2-8020-measurements.18076/
Most 6" coaxials have more directivity. Sica 5.5 might be very good, as well KEF Q100/150 drivers.
Here another (merged) measurement of similar G2 https://www.audiosciencereview.com/forum/index.php?threads/genelec-g2-8020-measurements.18076/
Curiosity got the better of me so I simmed 2x SB12NRX25 + the Peerless CD and cheap horn. I made a traced response from the datasheet, merged it with my hornresp sim and applied the floorstanding speaker baffle to each woofer. I used the test measurements for the horn in post 19. This is my first attempt at a 2.5 way sim.
A second order crossover at 2k-ish. The directivity isn't as awful as I'd thought but there is 'waistbanding' at 1000hz.
A second order crossover at 2k-ish. The directivity isn't as awful as I'd thought but there is 'waistbanding' at 1000hz.
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Thanks for this, I think I need to some of my own tests on the 4020 and see what happens in normalisation. I suspect that the results won't be too dissimilar to directivity simulation above.
You could increase width at the rear side (trapezoid shape). This keeps visual appearence narrow, but adds volume.
With your room geometry and from your measurements of the Genelecs, your Schroeder cutoff is 250hz…..no way around that and in lies the beauty of DIY which allows you to design for your space.
What you do above 250 is inconsequential at this stage of the project….what happens below IMO is paramount and the limiting factor of what your final performance value can be.
…….so what woofer you choose, placement within a cab along with LF tuning and extension are your primary criteria……clearly your Genelecs or any well designed 2 way above Schroeder….even repurposed KEF Q150 coax’s would get that done.
Floor bounce is very evident in your measures…..keeping whatever woofer you choose close to the ground is going to be essential. As Schroeder is kinda dictating your Xo point, you’ve got around 26” of center to center distance from your yet chosen woofer to your yet chosen coax or midrange driver to stay within half a wavelength and avoid any lobing.
……so if you were going for maximum performance potential in that room, a forward firing woofer would be required. Everything is a compromise so the rest is up to you. How I would approach this is similar to what you outlined for the MT…..a narrow tower…..will image quite nicely and as close to the TV bump out as shown in your pic?…….you going to get some boundary gain there from the midwoofer to offset BSC a few db for sure. This is following your protocol for the pokey finger factor……take that away?……I build a WTMW 3.5 way using 2 SB racetrack woofer no question
With that, an active bass section below with side firing sub(woofers)…..sealed with a target F6 of 35hz or so…….your going to get PLENTY OF ROOM GAIN here to follow the acoustic 2nd order slope. Going active with something like a 2x4 mini DSP is going to allow you to clean up everything from 150hz on down individually…..and you’ll need 2 seperate channels because of that left side corner and how it will load the room…. Very different from the right side. Where you high pass the MT is going to require some subjective listening along with some objective observations.
What you do above 250 is inconsequential at this stage of the project….what happens below IMO is paramount and the limiting factor of what your final performance value can be.
…….so what woofer you choose, placement within a cab along with LF tuning and extension are your primary criteria……clearly your Genelecs or any well designed 2 way above Schroeder….even repurposed KEF Q150 coax’s would get that done.
Floor bounce is very evident in your measures…..keeping whatever woofer you choose close to the ground is going to be essential. As Schroeder is kinda dictating your Xo point, you’ve got around 26” of center to center distance from your yet chosen woofer to your yet chosen coax or midrange driver to stay within half a wavelength and avoid any lobing.
……so if you were going for maximum performance potential in that room, a forward firing woofer would be required. Everything is a compromise so the rest is up to you. How I would approach this is similar to what you outlined for the MT…..a narrow tower…..will image quite nicely and as close to the TV bump out as shown in your pic?…….you going to get some boundary gain there from the midwoofer to offset BSC a few db for sure. This is following your protocol for the pokey finger factor……take that away?……I build a WTMW 3.5 way using 2 SB racetrack woofer no question
With that, an active bass section below with side firing sub(woofers)…..sealed with a target F6 of 35hz or so…….your going to get PLENTY OF ROOM GAIN here to follow the acoustic 2nd order slope. Going active with something like a 2x4 mini DSP is going to allow you to clean up everything from 150hz on down individually…..and you’ll need 2 seperate channels because of that left side corner and how it will load the room…. Very different from the right side. Where you high pass the MT is going to require some subjective listening along with some objective observations.
A tower that is 160x180mm and say 900mm high is a pole... You must construct some kind of legs to keep it standing!
You will be in trouble trying to find driver units that can be used in such a narrow baffle, remember that it has walls with some thickness
Are you sure about dimensions?
You will be in trouble trying to find driver units that can be used in such a narrow baffle, remember that it has walls with some thickness
Are you sure about dimensions?
Re slim tower. My wildest fantasties dictate a stick, basically. A stick that sounds like a beast. If I can come close to that I'll be happy and so will the rest of the family.
Yes, I have some ideas re stability which I won't share now as to not dilute the flow 🙂
Yes, I have some ideas re stability which I won't share now as to not dilute the flow 🙂
@mayhem13 I think you are right, there is an issue and I have the oppourtunity to address it: the floor bounce.
So, lets run a hypothetical up the flagpole...
What say we start with:
2 x Tang Band W5-1138SMF at the front bottom of the cabinet. One above the other. Sealed, Linkwitz Transform.
Crossing over at 250hz to
1 x 5" midrange of choice at top of cabinet.
These would be within 600mm of each other.
We are ignoring high frequencies for the time being.
We could double midrange drivers here, I suppose.
So, lets run a hypothetical up the flagpole...
What say we start with:
2 x Tang Band W5-1138SMF at the front bottom of the cabinet. One above the other. Sealed, Linkwitz Transform.
Crossing over at 250hz to
1 x 5" midrange of choice at top of cabinet.
These would be within 600mm of each other.
We are ignoring high frequencies for the time being.
We could double midrange drivers here, I suppose.
I wouldn't run the 1138 up that high.....it's a true sub woofer and the thick surround throws a shock wave through the response right at 200-300hz area.
I like the idea of the SB racetrack drivers instead......the 8 ohm variant wired in parallel with a coil on the lower woofer creating a 2nd order rolloff at say 100hz......this offsets baffle step and stops the lobing that might happen from the lower woofer to the midrange.......keeps efficiency too and with a sealed system, target an f6 instead of f3.....CLEARLY you have 6db of room gain centered at 40hz......you'll be just fine.
@mayhem13 cheers!
I like the race track drivers too but whichever way you wangle it the cabinets come out quite large. I know you can shrink a sealed cabinet when using an LT but probs not to the size I want to.
Something to mull on and I'm going to develop this idea of yours. Your input is very welcome, thanks.
I like the race track drivers too but whichever way you wangle it the cabinets come out quite large. I know you can shrink a sealed cabinet when using an LT but probs not to the size I want to.
Something to mull on and I'm going to develop this idea of yours. Your input is very welcome, thanks.
Those woofers will be fine if you can get the internal volume for the woofer section to 1cuft for one( the bottom) and a higher Q at .5cuft for the other.....the response hump will fill in the null at 80hz while still getting you down to 35hz in room. I'm assuming an enclosure 40" tall, 6.5" wide and 18" deep. The bottom woofer is gonna get an extra 2b or so of boundary gain from the floor. Or use the PR's they make for em on the rear of the enclosure......you won't be able to perceive the less than ideal impulse response from the listening position....and that's what matters
could you not build two subs to sit under your current speakers . they look so cool it would be a shame to put them away and not use them . a rear firing high xmax sub would solve both the inquisitive baby fingers and the bass problem for likely less money and work than starting a new project from scratch. you could always design some brackets to fix the horns to the mid enclosure if you are worried about it toppling on top of the little one . what midrange driver are you using ? it looks like a 10inch 18sound ?
kind regards James
kind regards James
I wouldn't worry taking the 1138 to 250 at all, as I've used the 1139 to 600 before, and most recently to 400Hz. It should be fine.
However, don't limit it with a sealed box. I know EQ and DSP are the rage, but a vented of PR box will allow the extension required. The 1139 does well vented in 14 ltrs tuned to about 45, and the 1138 should be able to do 40Hz in 7 ltrs with a pair of 5.25" PRs. It needs to breathe for bass.
However, don't limit it with a sealed box. I know EQ and DSP are the rage, but a vented of PR box will allow the extension required. The 1139 does well vented in 14 ltrs tuned to about 45, and the 1138 should be able to do 40Hz in 7 ltrs with a pair of 5.25" PRs. It needs to breathe for bass.
@jccart Thanks! I just fancy a change and they are a little bit big. Once I've grieved I can sell or pass them on.
@wolf_teeth well, I just remembered I have one. I can do some tests, not quite sure how to measure distortion at 250 without room interference but ill get it in a box and see.
My thoughts were to double up on drivers instead of venting one. I'm a bit short of time these days so it would make the bass tuning quite quick. I know at some point during the tuning I would curse having not spent another £100 just to go sealed.
@wolf_teeth well, I just remembered I have one. I can do some tests, not quite sure how to measure distortion at 250 without room interference but ill get it in a box and see.
My thoughts were to double up on drivers instead of venting one. I'm a bit short of time these days so it would make the bass tuning quite quick. I know at some point during the tuning I would curse having not spent another £100 just to go sealed.
Attachments
Here's some W5-1138 measurements, including distortion (YMMV): https://www.dibirama.it/home-page/s...rs-w5-1138smf-sub-woofer-5-4-ohm-80-wmax.html
You should compare measurements to others by same tester https://www.dibirama.it/archivio-altoparlanti.html
ScanSpeak 30W runs at 1,5%, so that must be masking with noise floor
ScanSpeak 30W runs at 1,5%, so that must be masking with noise floor
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