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Old 14th June 2012, 12:44 PM   #61
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Originally Posted by Swifty View Post
Hi Bob, did the alpair play full range? And playing louder than that caused, what? Audible distortion?
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.

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Old 14th June 2012, 01:11 PM   #62
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Originally Posted by Bob Brines View Post
OK. A7.3 and two RS225-4's it is.

Obviously, one 8" would be enough, but I want two for the transient response. It is my theory that the larger the Sd and therefore smaller excursion, the sharper the leading edge of the sound wave. IMO this is what produces "slam". I cannot understand a 4-6" "subwoofer" with huge Xmax. The leading edge of the sound wave has to be mushy. Again, this based on my experiments with am 18" H-frame. At 100dB and 30Hz, I had to put my finger on the cone to detect come motion.

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?

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Chris
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Old 14th June 2012, 01:13 PM   #63
Swifty is offline Swifty  Netherlands
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Originally Posted by fastbike1 View Post
I agree that this seems to be the critical question. Bob's scenario pretty much matches my typical listening w/ classical or jazz and I wouldn't consider it very demanding or unusual.

If the 7.3s can't handle this type of music/listening, what exactly is their expected "mission"?
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.

Last edited by Swifty; 14th June 2012 at 01:37 PM.
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Old 14th June 2012, 02:57 PM   #64
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Originally Posted by Bob Brines View Post
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
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?
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Old 14th June 2012, 03:12 PM   #65
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For me, its about adding body to the music. I feel like this is accomplished in this area in my experiments. Stays away from voices, but adds weight to instruments.
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Old 14th June 2012, 03:13 PM   #66
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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.
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Old 14th June 2012, 03:56 PM   #67
Swifty is offline Swifty  Netherlands
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Originally Posted by Rullknufs View Post
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.
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Old 14th June 2012, 04:02 PM   #68
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Originally Posted by Rullknufs View Post
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.
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.

Last edited by Monte Verdi; 14th June 2012 at 04:06 PM.
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Old 14th June 2012, 04:13 PM   #69
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Originally Posted by chris661 View Post
....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 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
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Old 14th June 2012, 04:18 PM   #70
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Originally Posted by Monte Verdi View Post
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?
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
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