The A7's are crossed to H-frames @300Hz (the minimum usable frequency of the small OB's. (I have A7's in my HT that are in small TL's and crossed to a real sub @160Hz. Same results.)
80dB is about as loud as I can stand. Anything over that is uncomfortable. so, I really don't know how much harder I can push things as still get decent sound. Remember that OSHA requires earplugs above 85dB. I think that the A7's at this level are adequate for classical, jazz, girl-and-a-guitar. To my ears, they work for 70's-80's rock. They surely will blow up with the 90-100dB that heavy rockers seem to require, but I have never advertised my speakers a suitable for metal.
Bob
It's fairly simple physics: if the cone moves 10mm p/p at 50Hz, then its maximum instantaneous velocity is given by Aw (where w is omega, 2pi/t, or 2pi*f).
3.15 metres per second. Not particularly fast in the grand scheme of things: I'd expect the drivetrain to maintain decent control there, but I'm no expert on these - perhaps Mark can help here?
I'm shocked by your observations, too: for a single 18" driver to do 100dB@30Hz in a closed box, over 3mm of one-way travel is needed. When you bring in a lossy dipole system, I'd expect a lot of cone excursion to do 30Hz at that SPL. Could you give details of how you measured this output?
Cheers,
Chris
I am curious how Bob is testing because in the FAST setup I'm using the Alpair 7.3's in, I can easily play them uncomfortably loud without any audible distortion. This is when actively crossing them @250 hz lr4. So if Bob is testing them with a high pass already, 80db max on transiens to me sounds way too low. Hence my question if Bob is testing them full range or not. I do not have an SPL meter (one is on its way though), but I certainly am hitting 90db+ levels @2.5m...
EDIT: Thanks Bob for the clarificaton, you posted while I was typing. Indeed 80db is as loud as I would ever play as well (save for short transients), but I that's not the limitation of the Alpair at this crossover point. Not in my box anyway. @ 20VA it outputs mid 90db levels, at less than 1mm travel according to WinISD.
EDIT2: Have you listened to the Dave Brubeck Quartet at Carnegie Hall? Sounds brilliant on the Alpairs, even on realisticly loud levels
. This type of music really suits them, although I have not found a type of music that puts them off.
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Bob,
Yes it would seem were on same page trying too get A7 too do 90 db classical music swings 8-10 ft out, also you guys seem too be crossing over much higher than where I'm at (100Hz as opposed to 250-300Hz) which I find interesting. Can you share reason?
Got my digital Radioshack SPL-meter today. Set it to C-weighting and played some music "really loud", louder than I usually play. I hit 93dB maximum at listening position (about 2.5m away I think). Normal listening levels are 70-80dB apparently. Am I pushing them too far or can I push them further? I feel that I'd like a little more dynamic capacity, maybe handle peaks up to 105dB or something.
105db will not be possible without melting it I'm afraid. I'd say 95/96db would be about the limit at those distances, crossed over at 300hz or so.
Very cool, not sure how accurate Radio Shack meter is, likely in ballpark. If you should have a smart phone of sorts I highly recommend down loading Smart Tools app. My phone has a 1.2 GHZ dual core processor and I believe margin for error is pretty good in spite of it's mediocre Mic. Unfortunately I have searched a great deal and have not been able too find Mic specs. Regardless, it's exciting too get A picture of what's happening!
My tests have shown speaker break up @ 82-83 db at 7-10ft away in equilateral triangle, crossingover @ 100hz with 12 db slope.
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I shouldn't have said 30Hz. I meant to say C-weighted. The catch is that most of the energy is an octave or more above the bottom note, which in this case was an organ playing C1 (~32Hz). Reed organ pipes, like plucked double basses and pianos have very little energy in the fundamental. The majority of the energy is in the harmonic structure. At 60-100Hz, the 18" driver doesn't have to move that far to get loud.
Bob
My OB's are small enough that 300Hz is all they can do, ergo 300Hz XO. My HT is crossed at 160Hz because that happily fills in the floor bounce. The higher you go, the less FM distortion you get, but anywhere above 100Hz should mean that the A7's are power limited rather than excursion limited.
Bob
I know the EL70 that I have wont do any 105dB. But I'm planning a new project
Right now my Mar-Kel70eN are crossed over at about 90Hz.I found a compensation table here -> How accurate is the Radio Shack SPL meter - Agoraquest - Sony Forum, News, Reviews
I do have a HTC Desire, but I don't trust its mic. But maybe I shall try and compare it to the compensated values of the digital radioshack meter.
105dB? For home listening?
(/TFPIC mode on)
If you're looking for 105dB, my suggestion is to contact Bob Heil to get his suggestions on the right kind of sound reinforcement components you will need. He specializes in large sound systems for rock bands and medium to large stadiums. He might know a few tricks to help you get above 100dB.
It is possible to get that level with a pair of Alpair 7s mounted in some headphones. Make sure you have an adequate supply of blood to replace what you'll likely lose from your ears.
(In that old Memorex commercial, wasn't that crystal wine glass shattered at something like 90dB?)
(/TFPIC mode off)
(/TFPIC mode on)
If you're looking for 105dB, my suggestion is to contact Bob Heil to get his suggestions on the right kind of sound reinforcement components you will need. He specializes in large sound systems for rock bands and medium to large stadiums. He might know a few tricks to help you get above 100dB.
It is possible to get that level with a pair of Alpair 7s mounted in some headphones. Make sure you have an adequate supply of blood to replace what you'll likely lose from your ears.
(In that old Memorex commercial, wasn't that crystal wine glass shattered at something like 90dB?)
(/TFPIC mode off)
Every 3dB increase in SPL requires a doubling of the power input. Lets suppose that an A7 can sustain 95dB. Let's also suppose that the A7 is taking 10w to get there. To get 105dB will require TEN TIMESas much power. Imagine what will happen to that poor little driver trying to absorb 100w.
Bob
I wasn't saying I would use the A7.3. I'm thinking of something a little bigger maybe and something not full-range. But I'll take that discussion in my thread over here here to not go too off-topic in this thread.
When Bernie & i were excercising the limits of the EL70/WoofT (XO 2nd order at 100 Hz), the iPhone/AudioTools meter was giving 90 dB (LOUD) no problem, another 6 dB and the drivers were moving a lot. Normal levels were 70-80 @ ~4m, my room is large.
dave
Yes, depending upon your room size. After a point, there will be some "cabin gain" for low frequencies even in larger rooms that might help. Not that humans can even tolerate that level for long without permanent damage to their hearing.
Right now I'm listening to some Amy MacDonald at normal levels and my SPL-meter says 70-75 at 2.5-3m. I guess that's a pretty common average level?
The next time I go to Sundsvall (nearest big city) I'll bring my SPL meter with me and go to a hi-fi store and see how loud I want to play.
That's really the best way to determine what you really want. Even then, the level may end up being different than what you use during normal listening in your room.
I find my personal listening level is much lower that some of my friends' preferred levels. I think also the quality of the system has an impact of the listening level. Again, I find that the better systems can provide a wonderful experience at lower levels than lesser systems. But these are just my opinions and preferences for the music I enjoy. Your preferences and music may be different.
I find my personal listening level is much lower that some of my friends' preferred levels. I think also the quality of the system has an impact of the listening level. Again, I find that the better systems can provide a wonderful experience at lower levels than lesser systems. But these are just my opinions and preferences for the music I enjoy. Your preferences and music may be different.
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