I agree that twin 8" ported can be a very satisfying.
Used repeatedly by Curt Campbell and @jholtz in designs such as the Statements, Statements II
and Anthology , Anthology II:
You can build them with down firing ports, as I did. Works well in a 6x9x3.2m room:
Reference: https://www.htguide.com/forum/forum...ts-ii-a-musical-evolution?p=785180#post785180
Used repeatedly by Curt Campbell and @jholtz in designs such as the Statements, Statements II
and Anthology , Anthology II:
You can build them with down firing ports, as I did. Works well in a 6x9x3.2m room:
Reference: https://www.htguide.com/forum/forum...ts-ii-a-musical-evolution?p=785180#post785180
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All of the four woofer options will require a similar level of boost at 30 Hz, but I was interested in what the gain and EQ would be like over the whole range.
Here is the response of each of the four woofers, adjusted to 4-pi anechoic. All four woofer options are modelled in a 800 mm x 340 mm baffle, which is approximately what this project will use. In all four cases, two woofers are wired in parallel, in a 50 liter closed box.
Next I show an example of applying baffle step compensation, LT bass Eq, and low pass 2nd order filtering at 500 Hz. I also adjusted the gain to match the 95 dB sensitivity of the Bliesma M-74A driver. All of this EQ is notional and approximate, the actual EQ will be based on measured driver performance of course. But the point here is that this process was repeated for all four woofers.
Comparing the net results of all four fully EQ'd drivers, they are all the same.
And now we get to the interesting part of this analysis. Here we have the filter gain which must be applied to each woofer to achieve the desired response.
At 30 Hz, there is not much difference in gain. The lowest is the 26W/8867T revelator, and the highest gain is the 10RS430, and the difference from highest to lowest is 1.6 dB in gain.
The RSS265 and 10RS430 have very similar gain requirements up to 50 Hz, and the two Scan Speak woofers are also similar to each other with the Discovery needing about 1 dB less gain.
By 100 Hz, there are differences. The RSS265 requires the most gain, while the Scan Speak 26W/8534G Discovery requires the least gain. The Revelator and the Faital Pro are similar to each other. By 200 Hz, all the drivers are similar at near zero gain, except the Dayton RSS265, which requires about 5 dB.
I am still thinking about what this all means. The RSS265 is definitely a voltage and current hog, and it needs some power. However, the pair of RSS265s in this analysis are actually very close my current SB34NRX75-6 12" woofer in terms of sensitivity and efficiency. The SB34 has about a 1 dB sensitivity advantage over the pair of RSS265's. So although the Dayton RSS265's seem like the oddball when compared to the other three 10" woofers, I do not foresee any real problem with using it in this application.
J.
Here is the response of each of the four woofers, adjusted to 4-pi anechoic. All four woofer options are modelled in a 800 mm x 340 mm baffle, which is approximately what this project will use. In all four cases, two woofers are wired in parallel, in a 50 liter closed box.
Next I show an example of applying baffle step compensation, LT bass Eq, and low pass 2nd order filtering at 500 Hz. I also adjusted the gain to match the 95 dB sensitivity of the Bliesma M-74A driver. All of this EQ is notional and approximate, the actual EQ will be based on measured driver performance of course. But the point here is that this process was repeated for all four woofers.
Comparing the net results of all four fully EQ'd drivers, they are all the same.
And now we get to the interesting part of this analysis. Here we have the filter gain which must be applied to each woofer to achieve the desired response.
At 30 Hz, there is not much difference in gain. The lowest is the 26W/8867T revelator, and the highest gain is the 10RS430, and the difference from highest to lowest is 1.6 dB in gain.
The RSS265 and 10RS430 have very similar gain requirements up to 50 Hz, and the two Scan Speak woofers are also similar to each other with the Discovery needing about 1 dB less gain.
By 100 Hz, there are differences. The RSS265 requires the most gain, while the Scan Speak 26W/8534G Discovery requires the least gain. The Revelator and the Faital Pro are similar to each other. By 200 Hz, all the drivers are similar at near zero gain, except the Dayton RSS265, which requires about 5 dB.
I am still thinking about what this all means. The RSS265 is definitely a voltage and current hog, and it needs some power. However, the pair of RSS265s in this analysis are actually very close my current SB34NRX75-6 12" woofer in terms of sensitivity and efficiency. The SB34 has about a 1 dB sensitivity advantage over the pair of RSS265's. So although the Dayton RSS265's seem like the oddball when compared to the other three 10" woofers, I do not foresee any real problem with using it in this application.
J.
Looking at the gain chart I think the difference between a sub-woofer, a pro mid-woofer and a woofer is vey clear. Above 100Hz the sub-woofer needs more power to move the heavy cone and at 200hz it struggles even more. That is why I had asked if the sub-woofer would be the best option for crossing to a 3 inch dome at 500hz. By the way, I use pair RSS265HF-4 drivers in 25 liter sealed boxes for subs, they are nice subs but I cross at 80hz.
Same with single 8 ohm version in 33l sealed but no problem crossing at 200~250Hz LR4. Full rich high bass/low mid even at high SPL.
Yes, it needs more power, but the power required is relative. And power is readily available.
Let's say I used a single 10PR430 and a subwoofer. The single 10PR130 would need about 6 dB of gain to match up with the midrange driver, and the subwoofer would likely need another 6 dB of gain to match up with the 10PR130.
When a high output compression driver with a large horn is matched up to a woofer, the woofer is going to need a lot of gain... Typical CD sensitivity is 104 - 110 dB, while large PA cone drivers are 95 - 100 dB... and considering the woofer/midrange cone will need some kind of low frequency EQ, well, it is not that much different than the situation I am contemplating.
Am I missing something ?
j.
That is not decided yet... I showed a simulation in Post # 45 where I ran (1) both woofers full range, and (2) the lower woofer rolling off early (passive inductor) to make this a 3.5 way system.
One idea is to install a switch to bypass the lower woofer inductor, and have one preset for "with inductor" and one preset for "without inductor".
The RSS265HF is a very clean driver, pistonic up to 2k, very low distortion. The only thing I fear is its need for power...
Some nice M74A implementation of small manufacturer Ari Acustics: https://www.ari-acoustics.de/p/nabucco
Some nice M74A implementation of small manufacturer Ari Acustics: https://www.ari-acoustics.de/p/nabucco
@Kwesi
If that price is right...
Goodness, Jim, just order a pair woofers of whatever models you want to try, route a hole to surface mount all available options, install, measure and listen away (and measure again with FSAF) ... I'll donate to your scientific study if you need...
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I am in no hurry to select the woofer. I am currently building a prototype of the trapezoid mid-tweeter baffle.... This will be used to collect polar response data from the M74A, which in turn will be used to select the appropriate tweeter.
The next step would be to test both mid and tweeter in the prototype trapezoid, refine the design, and if necessary, make a version 2 of the trapezoid prototype. My current plan is that after I am happy with the design of the trapezoidal enclosure, I will build and finish a pair of them. Only after the trapezoidal cabinet is complete will I start to build the two woofer boxes... so the choice of woofer is a long way off...
But I find the simulation and planning aspect rewarding and valuable.
So a sligthy wider standalone 12" is given up? (SB34RNXL)
Do wonder how it had performed in your good power response study VS others.
I believe you should cope to aluminium woofers because the Bliesma... Hard paper à la Norex maybe an option but the Faital I am not sure, you risk a tone mismatch perhaps.
The choice migth be simple : choose the one(s) that has the lowest odd harmonics between 100 hz and the Bliesma.
A naive question, how are performing woofers driver below their Fs (if for the illustration FS is >30 Hz) in a sealed system?
Do wonder how it had performed in your good power response study VS others.
I believe you should cope to aluminium woofers because the Bliesma... Hard paper à la Norex maybe an option but the Faital I am not sure, you risk a tone mismatch perhaps.
The choice migth be simple : choose the one(s) that has the lowest odd harmonics between 100 hz and the Bliesma.
A naive question, how are performing woofers driver below their Fs (if for the illustration FS is >30 Hz) in a sealed system?
Of course. I think it saves a lot of wasted time with building/designing/measurements.
Comparing to what you have previously built/heard can be instructive.
I only learned to do this later:
The difference at
50Hz: 9dB
40Hz: 8-9dB
30Hz: 6dB
20Hz: 3dB
The room.
Here is the 1m measurement of my Statement II, in my room (2015), miniDSP Umik-1 mic with supplied calibration file, Dirac Live 1.0 software for PC.
Rear of speakers 2 ft from wall.
Here is the measurement of both speakers at the LP (~10ft IIRC).
That response below ~400Hz (Schroeder) is just wild! Swings and peaks everywhere.
But clearly gets down to 20Hz in-room.
And, the top octave rolls off a little. All it in, it sounds REALLY good. I only sold it because of a house move.
4pi anechoic is not a good estimate in this case. 2pi is probably closer.
I know one designer who doesn't model for bass in 4pi, perhaps now I can see his point...
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I think most of us are aware of it. And quite some of us wish we could look the other way 😆
With the amount of bafflestep correction, there is tonality/neutrality tradeoff between direct and indirect sound. For small 2-way speakers, I do almost full correction (leaving a dB or so), because of the small baffle the step starts in the midrange. No correction would lead to very thin direct sound coloration. (Nearly) full correction then appears more neutral in direct sound, but overall "darker/fuller" then from the indirect sound; but more right in sum for my taste.
My eye on larger floorstander baffle sizing is to keep the 2pi -> 4pi transition in a range a) below typical room Schroeder Frequency, e.g 300Hz b) below xover frequency to midrange, e.g. 300Hz:
So all sound above schroder frequency from the lower mids on has less tonality difference between indirect and direct sound. Below schoeder frequency, I can voice to the room and speaker placing by focusing on the woofer channel (or even woofer placing on the baffel vs. room placing). Further, midrange works just in 2pi and must give less duty. I also would keep the "small" separate baffle for the mid wide enough to avoid large difference in bafflestep within the mid's operating range. Wide radius/facets yes, too narrow no...
My eye on larger floorstander baffle sizing is to keep the 2pi -> 4pi transition in a range a) below typical room Schroeder Frequency, e.g 300Hz b) below xover frequency to midrange, e.g. 300Hz:
So all sound above schroder frequency from the lower mids on has less tonality difference between indirect and direct sound. Below schoeder frequency, I can voice to the room and speaker placing by focusing on the woofer channel (or even woofer placing on the baffel vs. room placing). Further, midrange works just in 2pi and must give less duty. I also would keep the "small" separate baffle for the mid wide enough to avoid large difference in bafflestep within the mid's operating range. Wide radius/facets yes, too narrow no...
I personnally would size the smaller baffle for the mid and tweeter 24cm wide with large radius and the mid placed 18cm from the upper edge:
The midrange will operate then completely in 2pi, so it has less burden and jump in the directivity to the woofer section (has wider baffle) gets avoided.
Overall baffle directivity influence above follows then the "inverted Zwicker Curve" (dotted yellow line) as a compromise to tradeoff between direct and indirect sound perception. I once summarized it here (klick + scroll down):
P.P.S:
The midrange will operate then completely in 2pi, so it has less burden and jump in the directivity to the woofer section (has wider baffle) gets avoided.
Overall baffle directivity influence above follows then the "inverted Zwicker Curve" (dotted yellow line) as a compromise to tradeoff between direct and indirect sound perception. I once summarized it here (klick + scroll down):
P.P.S:
It's the kit price, i think. You must build the enclosures then yourself...
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Nice project Jim!……IMO and IME dome midranges offer the most detail and have the capacity to image better than any cone can ever achieve…..this was MORE than self evident after working primarily with ATC monitors as an engineer for years.
A significant word of caution……poor to bad recordings through domes will sound REALLY BAD as all of the poor microphone placements and phasing issues captured in the recording will now take front and center stage. IMO this is the main reason why the very popular 2 way midwoofer/tweeter 2 way bookshelf speaker is so popular…..everything sounds good as the midwoofer cone damps the bad and the 2-3k crossover mixes all the phase issues in. As hard as I tried, and try I did…..I could NEVER live with a pair of ATCs for recreational use. The only use I have found for dome mids either very selective in the playback content ( who does this?….sometime Led Zeppelin 1-4 is what’s needed!) or used in a 3way center channel speaker which is the only use I currently have one in…..for vocal intelligence and wide horizontal response, they have no equal.
Moving on…..you have them already along with a POC, so I’ll assume there’s no going back now.
On to the baffle…..when I returned to NYC back in 2004 I was unsure of my career viability as the recording and live sound industry was taking a beating from the emergence of streaming. I decided the best thing was to keep my life in storage and took a furnished sublet in the LES which at the time was affordable and close to best underground music in the city. Besides my clothes, the only thing I brought with me were my work from home Pro Arc monitors and integrated and a pair of ADATs. I promptly set them up and completely ignored the in house speakers as if they didn’t exist. Here’s a sample image of those very stylish and sleek things you’d find in a pretentious NYC apartment with concrete and steel interior.
One day while walking the LES, I came across a 180g Japanese vinyl pressing of Fleetwood Mac….and remembering the house system had a turntable I went with the impulse. Later than day after trying to plug the house TT into my integrated, where I discovered the phono stage was broken……never tried it before so who knows. Well….at this point I had the vinyl in hand so WTF, let’s give the house thing a try. Without embellishing the whole thing too much and yet discovering a life changing moment all in one sentence…….i had NEVER experienced soundstage imaging before like I had in that moment. While there were other issues in these slim towers, all was wildly outshined by the spatial separation and depth like never before. Quickly wrapped up, subsequent experiments and conclusions arrived at where that it was the slim baffle, or absence of a baffle that were responsible for that……and i could never go back to anything less than this level of soundstage performance again. Since you have the domes, and they don’t require an enclosure, I would only suggest that you take this opportunity to do some voicing and listen to them on their own in your space…..both on a mock up of your intended baffled design and with a minimal baffle only needed to support the driver itself and your intended tweeter. But be prepared……..this will change your perspective forever.
A significant word of caution……poor to bad recordings through domes will sound REALLY BAD as all of the poor microphone placements and phasing issues captured in the recording will now take front and center stage. IMO this is the main reason why the very popular 2 way midwoofer/tweeter 2 way bookshelf speaker is so popular…..everything sounds good as the midwoofer cone damps the bad and the 2-3k crossover mixes all the phase issues in. As hard as I tried, and try I did…..I could NEVER live with a pair of ATCs for recreational use. The only use I have found for dome mids either very selective in the playback content ( who does this?….sometime Led Zeppelin 1-4 is what’s needed!) or used in a 3way center channel speaker which is the only use I currently have one in…..for vocal intelligence and wide horizontal response, they have no equal.
Moving on…..you have them already along with a POC, so I’ll assume there’s no going back now.
On to the baffle…..when I returned to NYC back in 2004 I was unsure of my career viability as the recording and live sound industry was taking a beating from the emergence of streaming. I decided the best thing was to keep my life in storage and took a furnished sublet in the LES which at the time was affordable and close to best underground music in the city. Besides my clothes, the only thing I brought with me were my work from home Pro Arc monitors and integrated and a pair of ADATs. I promptly set them up and completely ignored the in house speakers as if they didn’t exist. Here’s a sample image of those very stylish and sleek things you’d find in a pretentious NYC apartment with concrete and steel interior.
One day while walking the LES, I came across a 180g Japanese vinyl pressing of Fleetwood Mac….and remembering the house system had a turntable I went with the impulse. Later than day after trying to plug the house TT into my integrated, where I discovered the phono stage was broken……never tried it before so who knows. Well….at this point I had the vinyl in hand so WTF, let’s give the house thing a try. Without embellishing the whole thing too much and yet discovering a life changing moment all in one sentence…….i had NEVER experienced soundstage imaging before like I had in that moment. While there were other issues in these slim towers, all was wildly outshined by the spatial separation and depth like never before. Quickly wrapped up, subsequent experiments and conclusions arrived at where that it was the slim baffle, or absence of a baffle that were responsible for that……and i could never go back to anything less than this level of soundstage performance again. Since you have the domes, and they don’t require an enclosure, I would only suggest that you take this opportunity to do some voicing and listen to them on their own in your space…..both on a mock up of your intended baffled design and with a minimal baffle only needed to support the driver itself and your intended tweeter. But be prepared……..this will change your perspective forever.
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I have experienced a minimal baffle speaker system. @HeadShake experimented with this a couple of years ago, and I was able to audition several of his prototypes. In one case he suspended a tweeter in open air with no baffle at all. This was a tweeter with no flange, so the outer diameter of this tweeter was about ~40 mm. It was basically a tweeter on a stick. The sense of 3-dimensional space was very impressive, about the best I have ever heard. That system may have had other flaws, but it did this one thing really well. Normally a particular design favors spaciousness over image precision (small baffle - wide directivity), or more precise localization with less spaciousness (narrow directivity - waveguide). But that little Audax tweeter on a stick could do it all. It was simultaneously very spacious and had excellent localization and depth.
j.
j.