Sound diffusion below 80 Hz

[Lee Batchelor]

Thanks Verdinut. I wondered that too. I have the Fronts set to small and have tried setting them to Large. The word on the street is to leave them set to Small but I'll re-visit your suggestion.

Excellent point about the sound pressure. I think sound pressure would be proportional to volume. I run my theater lively but not bone crushing. The room diagram I attached in Post #14, shows the positioning of all my speakers. The Altecs are far from any corners. The 15" Eminence sub is in the left corner and I am getting some corner loading from it but I have tried numerous other placements of that beast and can't seem to find anywhere else that works better. The one thing I haven't tried is moving both subs. I've always left the Lab 12 in it's current position to the right of the TV, amps, and speakers array. That should be my next move. Please take a look at my diagram and if you have any better suggestion for positioning both subs, I'll try it.

I enjoy hunting for the best sound but it would be nice to find that Eureka position. Thanks for chiming in!

 

[MrBoat]

Is that all that's in the room besides the equipment is a sofa and chair? A friend of mine got displaced from his home temporarily from hurricane Ian. He moved into his brother's. He had to store his living room furniture and other salvageable goods in his brother's music/theater room, which amounted to two additional sofas, upholstered chairs and a recliner. Also some mattresses stacked against the back wall, half dozen cardboard boxes full of bed clothes, and books. Brother noticed immediate improvement with his sound system and thought he was just having good listening days until his bro got his house back and took all the stuff back out.

Now he's refurnishing the room to look more like a living room. I know that's not fitting with today's sterile living spaces, but the cluttered living spaces of the '70s were much better listening environments, and this when speakers were large, and rooms much smaller.

 

[Lee Batchelor]

Excellent point, MrBoat. The perimeter walls have additional objects like variable height wall cabinets, wooden chairs, small book shelves, etc...nothing like additional soft furniture that would absorb sound. The flooring is carpet and the ceiling is Sonaflex suspended ceiling tiles. The room is actually quite dampened but the walls are drywall and the cause of the issues. The floor diagram is very simplified, designed to show dimensions and the placement of the audio/video gear.

I need to explore ways to build my own panels that will absorb 110Hz and lower. I've been listening to Dennis Foley a lot and he's of the opinion that nothing works better than his products. Of course, he's going to say that but to propose those kinds of prices for a home theater is ludicrous. He doesn't believe in bass traps either. There must be a way to build my own absorption panels. I have the tools and skill set. I just need the design .

Thanks for chiming in.

 

[fmw]

Wow, that's a lot of coin for passive treatments. I think I would lean more toward a properly calibrated multiple sub array than the necessarily huge and outrageously priced bass traps route. Good grief, $30k for activated charcoal traps? Incredible.

Ah high end audio. I sure don't miss it.

 

[Lee Batchelor]

Good one, fmw! An AM clock radio is starting to sound good about now!!!!

 

[MrBoat]

Good one, fmw! An AM clock radio is starting to sound good about now!!!!

My mains have Eminence Delta Pro 12-A woofers. I am a fan of their drivers. Ridiculously powerful and very low distortion.

 

[Lee Batchelor]

Agreed. Some people don't like Eminence drivers but I like them. I think Eminence de-rates their drivers by at least 25%. I've driven my 15" KappaLite3015LF pretty hard with a bass guitar and it was fine. They also provide box designs for free, along with the HP filter recommendations, but you know all this .

 

[fmw]

Good one, fmw! An AM clock radio is starting to sound good about now!!!!

As we all know, it is possible to get great sound without believing that a digital cable can alter the data it carries in a way that alters the sound one hears after it is decoded. It isn't necessary to value the high distortion in tube amps because one feels it is "warmer." While vinyl records represent true hi fi performance, it isn't necessary to believe that it sounds better than digital media. Nor is there a reason to believe that a $30,000 bass trap will outperform another that costs a fraction of that. No, I don't miss it at all.

 

[Lee Batchelor]

Good points, fmw .

 

[oltos]

The system sounds very good but I know I'm missing some definition in the 80 Hz and below range.

my three front loudspeakers contain a 15" Dayton sub, which replaced Altec 416-8A woofers.

Please advise if possible. I sent my pair of GPA Altec 416-8B to Troy Crowe for testing.
https://josephcrowe.com/blogs/news/altec-416-8b-in-100l-sealed

As you can see, due to the sealed box size at around 70Hz they probably won't play at much above 80db, if that much, at 11 feet away.

I thought of using a pair of these subs. https://www.rythmikaudio.com/F12SE.html

But until Troy Crowe builds the rest of the system-probably using this horn https://josephcrowe.com/products/3d-cad-files-horn-no-1994-es450-biradial-for-jbl-2446-2-throat -I will have no idea how well the Altec midwoofers and the Rythmik subs will sound together.

Would it be a mistake pairing the Altecs with these Rythmik subs?

 

[Verdinut]

Please advise if possible. I sent my pair of GPA Altec 416-8B to Troy Crowe for testing.
https://josephcrowe.com/blogs/news/altec-416-8b-in-100l-sealed

As you can see, due to the sealed box size at around 70Hz they probably won't play at much above 80db, if that much, at 11 feet away.

I thought of using a pair of these subs. https://www.rythmikaudio.com/F12SE.html

But until Troy Crowe builds the rest of the system-probably using this horn https://josephcrowe.com/products/3d-cad-files-horn-no-1994-es450-biradial-for-jbl-2446-2-throat -I will have no idea how well the Altec midwoofers and the Rythmik subs will sound together.

Would it be a mistake pairing the Altecs with these Rythmik subs?

The Altec 416-8B driver is not designed to operate in a sealed box. That's why you are unable to get adequate low frequency performance. It needs a ported box of at least 5 cubic feet. To get good results with it, the box should be tuned according to its Thiele/Small parameters. Speaker building is not that easy if you don't have proper knowledge of the functioning of loudspeaker drivers and proper testing equipment.

The 416 driver is not a mid-woofer but a real pro audio woofer with limited efficient LF response below 35 Hertz. If you want to use it with a Rythmik sub, then you would need to use bi-amplification with an electronic crossover and a low filter frequency below 100 Hz.

With regard to Crowe's newly designed horn, we have no info whatsoever. It's impossible to know if it would make a good match with the sensitive Altec driver. As I already mentioned, for DIY speaker building you need a certain knowledge.

 

[oltos]

The Altec 416-8B driver is not designed to operate in a sealed box. That's why you are unable to get adequate low frequency performance. It needs a ported box of at least 5 cubic feet. To get good results with it, the box should be tuned according to its Thiele/Small parameters.

I was well aware that the 416 was designed to work in ported cabinets, though as I recall from an Altec datasheet that bass down to ~ 35Hz was said to be attainable in a 7 cu ft sealed cabinet. But despite my limited knowledge and DIY skills, when these were built in 2016 I was following the lead of fellow diyaudio.com member Gary Dahl, who in pursuit of reducing distortion to very low levels (as shown in Crowe's test report) put the 416s in those sealed 3 cu ft boxes to limit their low end response, but then extend system response using Acoustic Elegance subs/passive radiators. His system as of 2018. https://galibierdesign.com/wp-content/uploads/wa-trip_gary-d.jpg

Gary shared his cabinet sketches and numerous photos of cabinet bracing and other details so Jim Salk could clone them. Jim also built my Rythmik subs.

Salk Sound

www.salksound.com

I recently heard that Gary only uses the subs for home theater. For music, he claims to get ample bass response from room gain due to fortuitous speaker placement. I doubt if I will get that lucky in my room, hence my questions about using the Rythmik subs.

My main concern is if there will be any big tonality differences between the 416s and these subs if I'd have to cross at around 80Hz. I suppose the only way I could cross lower would be if I was satisfied with SPLs from the Altecs at ~ 70Hz in my 2660 cu ft room, however likely that would be.

Equal-loudness contour - Wikipedia

en.wikipedia.org

 

[Verdinut]

I was well aware that the 416 was designed to work in ported cabinets, though as I recall from an Altec datasheet that bass down to ~ 35Hz was said to be attainable in a 7 cu ft sealed cabinet. But despite my limited knowledge and DIY skills, when these were built in 2016 I was following the lead of fellow diyaudio.com member Gary Dahl, who in pursuit of reducing distortion to very low levels (as shown in Crowe's test report) put the 416s in those sealed 3 cu ft boxes to limit their low end response, but then extend system response using Acoustic Elegance subs/passive radiators. His system as of 2018. https://galibierdesign.com/wp-content/uploads/wa-trip_gary-d.jpg
Gary shared his cabinet sketches and numerous photos of cabinet bracing and other details so Jim Salk could clone them. Jim also built my Rythmik subs.

Salk Sound

www.salksound.com

I recently heard that Gary only uses the subs for home theater. For music, he claims to get ample bass response from room gain due to fortuitous speaker placement. I doubt if I will get that lucky in my room, hence my questions about using the Rythmik subs.

My main concern is if there will be any big tonality differences between the 416s and these subs if I'd have to cross at around 80Hz. I suppose the only way I could cross lower would be if I was satisfied with SPLs from the Altecs at ~ 70Hz in my 2660 cu ft room, however likely that would be.

Equal-loudness contour - Wikipedia

en.wikipedia.org

Let me say that the Altec 416 has a sensitivity of about 98 dB for a 2.83 volt input (1 watt for this 8 ohm driver). You shouldn't have to worry as it requires 10 times less amp power than most home speakers for same SPL. That's also why you would need bi-amplification should you use it with a sub
.
With regard to the tonality of this Altec woofer and that of subs, IMO any difference at the frequencies of such LF drivers would be inaudible.

 

[highfigh]

Still at it, I see.

First, you're not trying to diffuse sound, you're trying to absorb it- if you want to diffuse it, add irregularly-shaped items and move them around the room so the sound impacts them early in the path.

I would start by using the RTA with each speaker separately. One is likely to be different from another in its response and as the other is added gradually (using the balance control), the dip around 72Hz will show up, indicating that it's a cancellation caused by speaker placement. While it's not reasonable to expect drastic changes in placement, small ones can make a big difference. I would mark the speaker location with painter's tape at the corners, then adjust the toe-in. LISTEN before making any other changes but measure it again.

I had a big cancellation in my room closer to 80Hz and it was so bad I hated listening because the furniture can't really be moved and I didn't want to rotate the room/system. I ran Room EQ Wizard and saw the problem, so I rotated the speakers as I mentioned. It helped, but more for the overall image/separation than the problem. Then, because I had them left over from a home theater demo, I started placing the acoustic panels I had made- began at the left side first reflection area and saw that it helped, but not much. Then, I added panels to the front corners and saw a strong change for the better. Next, I put a panel in the left rear corner and continued by stacking another on that one. The right rear corner is a doorway, so it can't have a panel, nor does it need one. I used 4" thick at the front corners and 2" at the rear, all are 2' x 4'. The problem is gone and I didn't spend much on these, which are 1" thick Owens-Corning 703 fiberglass, fastened to pegboard with contact cement, covered with muslin. The muslin was used because it's inexpensive and it blends in with the paint color. Any fabric that you can see through easily will work- you're not going to find something that's demonstrably better, even from Guilford of Maine (I have their catalog- it's nothing special).