Room: Maybe slightly larger than the average Long Island, NY living room with triangular ceiling that peaks at 11 ft.
Listening distance and level: Main speakers 11 ft from chair and ~ 30 to 40 phons. (??) https://en.wikipedia.org/wiki/Phon
If the above listening distance/level is sensible and safe, then if I can get robust LOW distortion bass down to 30Hz @ ~ 75db to 80db then presumably I’d be quite happy. And I do plan to measure and treat the room acoustically prior to finishing with room/system EQ via Windows software.
But here’s my big worry: I’m working with a custom designer to finish a speaker build that I was forced to postpone years ago. Below the horn and driver will be an Altec 416-8B in a 3 cu ft sealed box.
https://greatplainsaudio.com/wp-content/uploads/2016/06/Classic-Series-416-8B-Spec-Sheet.pdf
The boxes were well braced and built by Jim Salk before he retired. Among other things, this 416-8B is famous for its underhung voice coil which the helps to minimize distortion. In a further effort to minimize IM distortion, the original designer also chose the 3 cu ft sealed box size and the amount of this insulation. https://www.bondedlogic.com/ultratouch-denim-insulation/
The intended result was that the Altecs only play down to 70Hz. For below them he chose 15” drivers and passive radiators in the appropriately sized boxes. He completed this system circa 2017, and AFAIK was very happy with this system for years.
Then I learned this year that he only uses the subs for home theater use, apparently not for music. How could his hearing and/or source material have changed that much to want to give up response from below 70Hz to at least 30Hz? I emailed him about this but have yet to receive replies.
My question is how far up can Rythmik F12 sealed subs play before they would color the sound of these beautiful Altec midwoofers? https://www.rythmikaudio.com/F12.html
OTOH, the last thing I’d want to do is to risk porting these cabinets. Instead, might removing some of the insulation extend the Altecs’ bass response down to perhaps ??Hz without adding much, if any, audible distortion?
In any case, at what ~ ??Hz would crossing with a pair of Rythmik F12 subs ruin the sound stage of my main speakers?
Listening distance and level: Main speakers 11 ft from chair and ~ 30 to 40 phons. (??) https://en.wikipedia.org/wiki/Phon
If the above listening distance/level is sensible and safe, then if I can get robust LOW distortion bass down to 30Hz @ ~ 75db to 80db then presumably I’d be quite happy. And I do plan to measure and treat the room acoustically prior to finishing with room/system EQ via Windows software.
But here’s my big worry: I’m working with a custom designer to finish a speaker build that I was forced to postpone years ago. Below the horn and driver will be an Altec 416-8B in a 3 cu ft sealed box.
https://greatplainsaudio.com/wp-content/uploads/2016/06/Classic-Series-416-8B-Spec-Sheet.pdf
The boxes were well braced and built by Jim Salk before he retired. Among other things, this 416-8B is famous for its underhung voice coil which the helps to minimize distortion. In a further effort to minimize IM distortion, the original designer also chose the 3 cu ft sealed box size and the amount of this insulation. https://www.bondedlogic.com/ultratouch-denim-insulation/
The intended result was that the Altecs only play down to 70Hz. For below them he chose 15” drivers and passive radiators in the appropriately sized boxes. He completed this system circa 2017, and AFAIK was very happy with this system for years.
Then I learned this year that he only uses the subs for home theater use, apparently not for music. How could his hearing and/or source material have changed that much to want to give up response from below 70Hz to at least 30Hz? I emailed him about this but have yet to receive replies.
My question is how far up can Rythmik F12 sealed subs play before they would color the sound of these beautiful Altec midwoofers? https://www.rythmikaudio.com/F12.html
OTOH, the last thing I’d want to do is to risk porting these cabinets. Instead, might removing some of the insulation extend the Altecs’ bass response down to perhaps ??Hz without adding much, if any, audible distortion?
In any case, at what ~ ??Hz would crossing with a pair of Rythmik F12 subs ruin the sound stage of my main speakers?
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The 416-8B has 4mm Xmax, so in a sealed cabinet is capable of relatively low distortion at 97dB @30Hz in half space. In room response could be higher depending on placement. The response would need to be equalized if you want it "flat" or to conform to an equal loudness contour.
30 to 40 phons is well below conversational level between people seated 3-6 feet apart.
97 dB 30Hz would sound about 4 times more "robust" (louder) than 80dB.
The "color" of the Altecs is what it is. The Rythmic F-12 high pass filter only goes up to 100Hz, it has a 0-180 degree continuously variable phase adjustment, so you should be able to integrate it with the Altecs.
Removing some of the insulation would reduce the apparent volume of the sealed box, requiring a bit more power to achieve the same low frequency output.
Properly integrated subs should not degrade the sound stage of your main speakers.
Crossing above 100Hz could make the location of the subs more apparent, which could degrade imaging if the subs are not locaded near the mains.
Main problem is that apparently the F12 is low efficiency with no spec for the amp's gain either, so assume it won't keep up good enough with the 416, a common problem with consumer 'sub' systems.
As already mentioned, if a cross-over from sub to main was a "Disaster",
I would first look into phase orientation/relationship.
Even if a sub has inadequate output level/power, some degree of sound improvement
should be an easy thing to achieve > not difficult.
I would first look into phase orientation/relationship.
Even if a sub has inadequate output level/power, some degree of sound improvement
should be an easy thing to achieve > not difficult.
If the mains can handle being run full range, then don't cross them. Just add the subs.
If the F12 gain is not keeping up with the 416's, the 416's amp inputs could be attenuated to match.
Maybe things don't look as bad as I thought?? But first, what would be the apparent loudness level from the above curves of 60 phons with me seated at 11 ft? How much lower or higher than the sound of a small jazz combo at that distance? In any case, following that 60 phon curve shows that 30Hz would have to be ~ 95db SPL to be as loud as 60 phons at ~ 1kHz, yes?
If so, then please evaluation the distortion measurements in this report-the only such review I've ever found that actually did such tests on the F12.
https://www.erinsaudiocorner.com/loudspeakers/rythmik-f12g-direct-servo-subwoofer/
From those curves is the F12's distortion computable as an approximate percentage at 95db SPL?
As for the high efficiency of the 416-8B, Troy Crowe will likely be using autoformers for attenuators (only). Thus, could I thereby balance the levels of the Altecs with the Rythmik subs?
And therefore would there be no need to remove any insulation as the attenuators allow the Altec's level to be reduced to balance with the subs, and because the subs only have to cross at
??Hz to blend well with the Altec box's 70Hz cutoff?
Placement-wise, my plan is to have the main speakers on the long wall with one sub ~ 2 feet to the left of the left main; same for the right. I also have another pair of F12 subs which I purchased as per the Geddes and Toole findings that mulitple subs typically yeild smoother bass-and allow each to play at lower levels, thereby minimizing distortion.
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The equal loudness curves show what SPL in dB or phons is required for average early adult hearing persons to perceive levels at the same "loudness". At louder levels, the response of hearing tends to "flatten out".
As age advances, high frequency hearing response typically drops considerably, the average 60 year old male hears 8kHz -30dB below an 18 year old, and 8dB less than a female 60year old. -10dB at 1kHz sounds about "half as loud", at low frequency the difference drops to half that.
A dynamic acoustic "small jazz combo" could hit levels of over 110 dB (C weighting, slow) and peaks upwards of 120dB at 11 feet.
During the "dinner set", they might be 20dB lower 😎
Autoformers would likely be used to attenuate the high frequency horn driver passive crossover output to match the 416 level.
Don't quite follow. Are you implying that the proper or better way to achieve optimal subwoofer placement is-following some degree of correcting the room acoustically with absorbers and diffusers-to then use room/system EQ via REW, Audiolense or such (Windows) software and MCH DACs like
https://www.oktoresearch.com/dac8pro.htm
or https://www.merging.com/products/interfaces/hapi ??
Okay, but the curves you show say nothing about changes below 250Hz. So, assuming there is little reduction in hearing acuity with age below this, then at least nothing much above 95db would be needed years from now for me to perceive the same level at 30Hz.
Also, while it's true that "LIVE" small jazz combos can indeed hit levels > 110db + peaks at 11 ft, virtually all of my recordings-CDs and even higher res sources https://www.hdtracks.com/#/album/5df1427d0bee25c09bc163fd-were hit with substantial compression during the final mastering. The dynamic range of these and most recordings is far below that of live performances.
Therefore, "working backwards" from 95db @ 30Hz, what would the apparent loudness level of 1kHz in phons for a male 55 years at 11 ft? And in db SPL? Don't forget that it would have to way less than 95db, because the ear's sensitivity drops quite rapidly below ~ 200Hz. Am I making sense here?
Otherwise, how then to balance the Altecs and subwoofers levels?
As the Wikipedea article explained, the phon is matched to a reference frequency of 1 kHz.
95dB SPL @1kHz=95phon.
95dB SPL @ 35 Hz would sound equally loud as around 42 dB SPL at 1kHz, or the 42 phon level.
As far as reproduction of music, you may want to increase low frequency level when you play it back at levels lower than it was mastered at- what the "loudness" contour switch on many pre-amps or receivers does.
If the F12 gain/volume control does not keep up or surpass the level of the 416's, the 416's amp inputs could be attenuated/reduced to match.
If the 416's amp has no gain/volume/attenuation controls, you can add fixed or stepped resistor attenuation or potentiometer.
If I'm understanding what you're getting at, I'm going to say no.
You seem to be overthinking things for where you are in the process and adding unnecessary complexity with the equal loudness curves. Essentially (ignoring the way a lot of recording is actually done) 95 dB of 30 Hz at the recording session should be reproduced at 95 dB at the listening seat by your playback system. Same goes for whatever other frequency you want to pick. You shouldn't be derating that based on phons.
I can't tell if you're intending to try to use equal loudness curves for in-room equalization/targets also, but that's not normally done either. Due to directivity, absorption, and measurement issues, most people prefer an in-room response with a gentle downward slope with increasing frequency, but that has nothing to do with equal loudness curves, hearing loss, etc.
My take on the original post's home-theater-specific subwoofer question is that a great deal of music really doesn't benefit from a subwoofer, even with mains that don't play all the way down. Purists often don't use subs because they add complexity. That doesn't mean they're a huge detriment to sound quality though. Home theater, on the other hand, makes extensive use of and more demands on subwoofers. It's kind of like car audio - lots of audiophiles enjoy much more bass in a car than they would ever think about using for their main home music system. They might also enjoy gigantic explosions in movies at levels they would never ask for when listening to music.
You haven't actually heard your main speakers in your room. Start with that. If their natural response is a little light in the bass for your tastes, try EQ as suggested earlier. If that's not enough, add subs. If you don't like the Rhythmik's sound, switch to a sub that includes room correction. That will likely improve sub sound quality more than the other things you've talked about.
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