At those low frequencies and long wavelengths, phase is not a concern. The wavelength of the 440-Hz. "A" is just under 3' and time alignment is important in this area of frequencies. Physics 101 A 40 Hz. wave is how long? A 40 Hz. wavelength can be found by dividing the speed of sound in feet which is 1,130 feet / second by the frequency we need to find the length of. Dividing 1,130 by 40 produces a quotient of around 28 feet. Therefore, a 40 Hz. wave is 28 feet long. When we get down to 40-Hz. and below, time alignment no longer becomes an issue, that is why we cannot localize these frequencies. This is also why you can place a sub just about anywhere in the listdning room.
Yes at those frequencies sub placement becomes more about the interaction with the room than speaker phase issues. The other thing- and what I had noticed is the OP's current setup is quite clean and tidy. It may be to enable the two subs will require some thought for running IC's and/or power cables. I know what I originally wanted to do and what I ended up doing were two different things based on the logistics of maintaining a clean installation plus room dynamics placement issues.
The bigger issue is that there is a fairly large difference between a compact cabinet, high power home sub and a large commercial bass horn design. The commercial sub is like the bass cabinet on the A7's. The sub-bass is natural and effortless. The cones in the sub, like the cone in the A7, move only a tiny amount. Where some larger home subs have a 4" travel. Compared to the horn sub, the bass takes on a more forced "pistonic" quality, like in a club playing EDM. But, a home sub matches better than I thought it might. I was playing around with a Decware 3.9-Watt 6V6GT that I acquired. I wanted to see how the A7's played with amp by itself. While it was not going to blow any doors off, it played with a surprising amount of bass / sub-bass. I was so impressed, it was not to loud jazz, but it sounded better than it had a right to be. Now, I understood, with the 100-dB. sensitivity of the A7's, how the main notes could play so nice, but there is no way around needing power for deep strong bass. After a few days, it suddenly hit me! I had a second Polk wireless sub in the back corner of the room and it was still playing. After I turned it off, the deep bass went away. Things made sense again. I did end up turning it back on. I was pleased that this home sub was playing so well with the Altec’s. While it had been there all along, it was not noticeable with the larger amps driving the A7's, along with the commercial sub.
Indeed. High efficiency mains require more (home) subs. Its really a trade off. ‘So I have these huge speakers and still need Subs’. Whaa? I have four subs and it works. Less motion from more cones is way better than trying to get it all from one 12” ( or like that)
I had added two 18 inch Scaena subwoofers at 45 hz lowpass crossover using Crown XLS 2502. It add slightly more rumble and tighter bass. But the difference is rather small. That means Altec A7 can do well without any subwoofers at my listening room.
It all depends on the source material. Try this... Suggest setting the Crown to crossover at 40-Hz., with a 24-dB. slope. I use the bass managent of the HT processor to do this on my system. Then the sub-bass is routed to the rack mounted Crown XTi-2000 through the LFE output of the processor. The Crown is delivering up to 1,600-Watts in the bridged mono mode. The Crown is used only for the sub-bass and doesn't power the 828 bass bins of the A7's. Also, check to insure that the synth sub-bass feature of the Crown is disabled. When it is enabled, in addition to the regular sub-bass, it will synthesize additional sub-bass down one octave from the regular sub-bass. This is annoying and unnatural.
I see much of your listening is female vocalist and vintage recordings. I suspect 98% of the time you wouldn’t see much need for the sub. If you were going to integrate the sub with the type of music you listen to it may be interesting try a bit higher crossover point maybe even up to 50hz. Your room is larger and maybe it would be compatible.
Despite the source music, I fail to discern why it would be beneficial to cross the subs over in the frequency range that the A7's are already covering? The A7's 828 bass cabinet does bass. It does good strong bass. It doesn't hit its -3 dB. point until below 60-Hz., and its -6 dB. point is around 40-Hz. It will play the 41.5 Hz. open "E" string on an electric bass, very strong, without any difficulty.
I agree on all those points. OP stated a lack of much difference he noticed sonically using a crossover at 45 hz. Personally I thought his impression of a bit more rumble and tighter bass was a win. But the song Billie Jean may not have much content below 40hz, even tho it seems bass heavy. It seems reasonable to give a shot at both higher/ lower crossover points to see if one prefers over the other rather than 45hz. Room interaction, source and material, and personal preference should play a roll in final setup for sure. Cheers, RW
I got one for you @SandAndGlass -- after the Shearer horn, using JBLs, the first commercial Altec was....an A2? It's a little big. As for bass, I think modern bass sounds different than horn loaded bass. I'd like the latter, but "Dear Diary: do I have to buy a new property or build a separate building?" I'm not asking for a friend.
I am experimenting all the possible options. So far cutoff at 56hz does seems to work better. But my impression so far is that Altec A7 could sound fine without subwoofer at my listening room.
The Altecs sounded more accurate and natural. Especially the piano. I only listned to the first tune. The other speakers had an echo or reverb sound and the piano sounded processed.
Well, yes the A2 was a "little" big at 2,200 lbs! Least we also remember the size of the movie palaces wherein they resided. They also had to be gigantic, as they had little option of powerful amplifiers at that time and had to depend on physics. I think the A4's were more typical of what would be found in typical movie theaters of the 60's, when I was growing up. I don't at all think that typical modern speakers even begin to approach bass in the open natural way that the A7's do. The number one complaint that everyone in the audio community has with A7's (besides being big and ugly), is their obvious lack of bass. But, what do members of the audio community do when their speakers don't go low enough, they add in a sub or two. Fortunately, you can add a horn loaded commercial sub that is smaller than a house and it will do the trick. Still large, you might say? My Yorkville UCS-1, is smaller than the 828 bass cabinet of the A7's and I have only one of those cabinets for both A7's. Considering that we are talking A7's here, I don't think it is a big stretch, not to worry about a compact home sub. Go big or go home! @thomaskong, may I suggest an album that will showcase the A7's ability to do deep strong bass without a sub? Preforming as a trio, with Mel Schacher on bass, will give you an exemplary example of how a electric bass guitar sounds in a rock band. Start with the first track "Got This Feeling On The Move". Streaming audio or YouTube video will be fine.
How are they dialing in? Interesting you picked 56hz. I had to check, and found my two 12” subs are set right about that as well. The two other subs have dual 8”s and for some reason I have those set a little higher, looks like closer to 62hz or so. I used to love me some Grand Funk. They do one of the better covers of Feelin’ Alright. Great bass line as well.
Bass guitar on this album can't be beat. Crank up the A7's to true concert level and see how they preform hard rock bass, no sub needed. These babies will absolutely pound!
I think speaker cabinet shape is where it is at…ala the Sonus faber Lute shape. My Dad has a pair of Jennings Research speakers that look absolutely amazing in full walnut. Piece of art in itself…but if the crossovers and caps get replaced…the internal rectangular shape is still a hinderance not to mention the hardwood Shape is where it is at. Not sure if Sonus faber was the first at cabinet curve shape, but it seems all new speakers have taken it into consideration and a lot have followed the “Lute” shape. Could be completely off on thinking Sonus faber made it “popular”, but that's the first company I think of. Imaging Harbeth throwing in some “curves” Come on Brits…we all lov curves…even British women havencurves.mmmm…. Fat Bottom Girls make the world go round. Whole Lotta Mary.
@Bill Hart … here’s a link to the 1945 Altec catalog, which is the earliest I know of. I believe the A2 you mentioned was geared more toward a bedroom system; the A1 on the cover is really what you’re after You definitely see it done to that extreme, don’t you? I’m not sure it’s necessary, though. If your room size = 31’ x 14’, then you should be able to get true horn-loaded bass down into the 30s without egregious compromises. The question is how to get there. From ideal (i.e., straight horn whose length and mouth circumference are equal to the wavelength of the lowest frequency reproduced) you’re obviously going to have to scale down. Gentle fold(s), 1/2-size mouth, and 1/2 or even 1/4-size length can get you there. Or maybe a tapped horn?
Interesting... This is the first time I have seen a photo of the A1. Have only previously seen the A2 in photos. Haven't ever read anything about it. Have always been curious. If there is an A2, it stood to reason that there must have been an A1?
Jim Hodgson's bottom photo of a Western Electric setup is similar to a modern version using G.I.P. replica drivers I heard at Deja Vu Audio, a picture of which is shown on their website here: https://www.dejavuaudio.com/?pgid=k72rg5z6-41bcb8ed-5848-11ea-8c85-12879e2400f0 It utilizes the same 15A horn and 555 field coil compression drivers, twin 18" field coil woofers, and an upgraded version of the 597 field coil tweeter. These old school systems sound magnificent.
Deja Vu must be heaven on earth. Not sure how I can explain having never visited … other than that I would’ve never left! You’re fortunate to be so close—both geographically and conceptually.
I would love to hav RCA field coil speakers made in 1937. You can go to 29:30 of the video. The above video was taken at Audio Exp0 Seoul 2021 which was held on Dec 11 to 13th 2021.
Nice new horn system called Seawave Accoustics at 41:00 of the above video. I would have been there if I had been in Seoul on December 11th-13th. I was born in Seoul and had lived there for 40 years. There are many nice audio shops over there. Thus I could easily switch between Krell, Jeff Rowland, Jadis 200, 500 when I practiced as attorney in Seoul 20 years ago. But I am retired now and enjoy staying in Washington State.
