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Old 21st December 2011, 08:10 PM   #31
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Originally Posted by weltersys View Post
At about 95 dB sensitivity the Eminence Alpha 6A beats those by a good margin, but does not go quite as low.

It is a very good sounding speaker, and goes high and smooth enough that tweeter choice and crossover is easy. I have used them outdoors and could get a surprising amount of thump from them.

The box below is about the same size as your suitcase, putting a pair in the same size will still have about the same F3 (85 Hz), but will raise the upper sensitivity to 98 dB. 10 watts to each speaker should get you around 111 dB at one meter.

Art
That reminds me; I have a modified Alpha-6C that I need to send in to DIYMA to have tested.
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Old 21st December 2011, 08:38 PM   #32
Veloxy is offline Veloxy  Sweden
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Quote:
Originally Posted by weltersys View Post
At about 95 dB sensitivity the Eminence Alpha 6A beats those by a good margin, but does not go quite as low.

It is a very good sounding speaker, and goes high and smooth enough that tweeter choice and crossover is easy. I have used them outdoors and could get a surprising amount of thump from them.

The box below is about the same size as your suitcase, putting a pair in the same size will still have about the same F3 (85 Hz), but will raise the upper sensitivity to 98 dB. 10 watts to each speaker should get you around 111 dB at one meter.

Art
Actually, the truth is usually exposed when placing them into simulations!

After simulating the Eminence Alpha A6 with winISD I get a F3 of about 138Hz... Way to high for my taste compared to ScanSpeaks that has a F3 of 86Hz. And as it being so much louder, not really sure about that... Simulations tell me it is only 2db louder than the ScanSpeak due to it being a 8 ohm speaker. After taking a look at the frequenzy/db graph... It dosnt even reach 95dB in reality!! The eminence tops 94dB at 200hz and as low as 91.5dB between 700-900Hz... Considering the unsmoothness I just described, I would say they are about as loud. Fine, 1dB louder at 200hz but heck 1.5dB more quiet at 700-800hz? I am curious if the Eminence is the dealbreaker here

Last edited by Veloxy; 21st December 2011 at 08:57 PM.
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Old 21st December 2011, 09:47 PM   #33
mdocod is offline mdocod  United States
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I've never seen an amp that is expected to deliver more than double it's rated output at 4ohm, than into 8ohm. I'm guessing the unit is voltage limited somehow and therefor optimized for the lower resistance load where it can make best use of available voltage and current carrying capacity. Either way, the ratings sound very unusual to me. Other TA2020 based amps don't seem to scale this way from my recollection. Just something to keep in mind.

-----

That said... For your battery pack, I'm a big fan of LiFeP04 for it's safety and service life. However, I would personally go LiCo for the better energy density. You don't really need the high current capabilities of LiFeP04 here. Modern big-name LiCo cells have come a long way in recent years for safety. Just make sure they are configured with proper global PCB and balance taps for charging.

----

Assuming a LiFeP04 4200mAH pack, 12.8V nominal, ~50WH:

Estimated Runtime @ 20WPC: About an hour.
Estimated Runtime @ 10WPC: About 2 hours.

3dB sensitivity is the difference needed to achieve twice the runtime at the same listening levels. Dropping the load from 8 to 4ohm to get a higher USPL rating does not improve battery life at equal listening levels. 4Ohm>91db@2.83V is no better for your runtime than any 8 Ohm speaker rated 88dB efficiency.

----

I just tried a google search and came up with 2x25WPC@10%THD into 4Ohm for an amp6, making those drive levels pretty unacceptable if you want to be able to listen for 5 minutes without wanting to tear your eyes out of your skill. At 15WPC, it's rated 0.1%THD, which is probably going to be the more realistic drive level to expect and use as a comparison. (just pointing this out as something to keep in mind).

Eric

Last edited by mdocod; 21st December 2011 at 09:52 PM.
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Old 21st December 2011, 10:14 PM   #34
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Quote:
Originally Posted by mdocod View Post
Hello 454,

I'm under the impression that this is a portable unit here where actual power efficiency may very well come into play as being important. The suitcase style units I have seen usually have a built in rechargeable power supply, and even if that's not the case here, improving efficiency means the design can get away with a smaller power supply for the amp anyways.
Yes, good point.
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Old 21st December 2011, 11:29 PM   #35
Veloxy is offline Veloxy  Sweden
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Quote:
Originally Posted by mdocod View Post
I've never seen an amp that is expected to deliver more than double it's rated output at 4ohm, than into 8ohm. I'm guessing the unit is voltage limited somehow and therefor optimized for the lower resistance load where it can make best use of available voltage and current carrying capacity. Either way, the ratings sound very unusual to me. Other TA2020 based amps don't seem to scale this way from my recollection. Just something to keep in mind.

-----

That said... For your battery pack, I'm a big fan of LiFeP04 for it's safety and service life. However, I would personally go LiCo for the better energy density. You don't really need the high current capabilities of LiFeP04 here. Modern big-name LiCo cells have come a long way in recent years for safety. Just make sure they are configured with proper global PCB and balance taps for charging.

----

Assuming a LiFeP04 4200mAH pack, 12.8V nominal, ~50WH:

Estimated Runtime @ 20WPC: About an hour.
Estimated Runtime @ 10WPC: About 2 hours.

3dB sensitivity is the difference needed to achieve twice the runtime at the same listening levels. Dropping the load from 8 to 4ohm to get a higher USPL rating does not improve battery life at equal listening levels. 4Ohm>91db@2.83V is no better for your runtime than any 8 Ohm speaker rated 88dB efficiency.

----

I just tried a google search and came up with 2x25WPC@10%THD into 4Ohm for an amp6, making those drive levels pretty unacceptable if you want to be able to listen for 5 minutes without wanting to tear your eyes out of your skill. At 15WPC, it's rated 0.1%THD, which is probably going to be the more realistic drive level to expect and use as a comparison. (just pointing this out as something to keep in mind).

Eric
Well, to be more accurate it is actually 9.8W in 8 Ohm & 19.1W in 4 ohm. at 10%THD ofcourse... This calculated with a 13.2V battery considering the amp6 has a effeciency at 90%.

(13.2 * 13.2 / 8 + 8 ) * ~0.9 = 9.8W
(13.2 * 13.2 / 4 + 4 ) * ~0.88 = 19.1W

Amp6 drains ~220mhA at 8ohm loads & 350mhA at 4ohm load. Very efficient!

Lico battery's? I cant seem to find any info on them...
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Old 22nd December 2011, 02:08 AM   #36
mdocod is offline mdocod  United States
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Hello Veloxy,

LiCo is short of Lithium Cobalt. It is the most common li-ion chemistry in production. Cobalt is the most common cathode material in high density li-ion cells. Most of the time, you will simply see them refereed to as "Li-Ion" cells. The problem with using the designation "Li-Ion" is that it is not specific. LiFeP04, LiMn, and basically any lithium chemistry rechargeable cell, is a "lithium ion" cell.

With all the new variations on lithium chemistry cells that have come into the mainstream in the last decade, it's important to know what you are getting. Always check the data sheets.

The Panasonic NCR18650 is probably one of the safest, highest density late generation LiCo cells that would be commonly available. Just be careful of where you source them as there are counterfeits and salvaged cells out there being sold. Also, you would have to have them assembled into a pack properly. That last part can often be the tricky part that may give you enough reason to go with a pre-assembled "hobby" style pack designed for RC cars (which will generally be either LiFeP04, LiPo (which is actually cobalt based), or LiMn). Alternatively, 18650 cell holders are becoming more common: http://www.batteryspace.com/li-ion-1...installed.aspx

You could use a pair of these wired in parallel loaded with NCR18650s,or other high capacity Japanese/Korean/USA made cells like Samsung, LG, Sony, Panasonic, etc (avoid Chinese cells unless you can confirm their safety):
http://www.batteryspace.com/Battery-...ong-20AWG.aspx

That would be about an ~80WH+ pack (cells are available ~2600-3100mAH these days pretty commonly), with a peak voltage of 16.8V (Looks like the regular amp6 can take this, but perhaps the "basic" unit can't? might want to figure out if this sort of thing would work in your application).

Eric

Last edited by mdocod; 22nd December 2011 at 02:15 AM.
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Old 22nd December 2011, 02:55 AM   #37
mdocod is offline mdocod  United States
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I just had another driver idea:
Galaxy Audio S5N-8 5" Neodymium Full Range Driver 8 Ohm 290-020

Not sure if they are available worldwide or not. Not much bass there, but man, you could count on some incredibly clean, loud listening levels. These are commonly refered to as "hot spot" type drivers as they are normally used as full range units, however, they can be used as a mid-bass very well also, crossing them over in the 3-5k range would work fine. These really would be the ultimate high efficiency portable workhorse drivers IMO. I would happily sacrifice the bottom end to have that efficiency and light weight design in a portable battery operated unit.
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Old 14th November 2012, 05:10 AM   #38
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Quote:
Originally Posted by Veloxy View Post
Actually, the truth is usually exposed when placing them into simulations!

After simulating the Eminence Alpha A6 with winISD I get a F3 of about 138Hz... Way to high for my taste compared to ScanSpeaks that has a F3 of 86Hz. And as it being so much louder, not really sure about that... Simulations tell me it is only 2db louder than the ScanSpeak due to it being a 8 ohm speaker. After taking a look at the frequenzy/db graph... It dosnt even reach 95dB in reality!! The eminence tops 94dB at 200hz and as low as 91.5dB between 700-900Hz... Considering the unsmoothness I just described, I would say they are about as loud. Fine, 1dB louder at 200hz but heck 1.5dB more quiet at 700-800hz? I am curious if the Eminence is the dealbreaker here
You also have to add room gain.
Simulations vs real world trial aren't always the same.
Personally was never that impressed with that Scan Speak driver-the fiberglass cone material IMHO sounded unnatural, and lacked some detail.
The Alpha is a very clean driver, a poor mans Audax PR170 (that IMHO outperform most drivers in it's class when used right (but is NOT a mid woofer by any means). If you want bass below 100hz, you have to port it.
The Aura Sound NS6-255A from P.E. is another option, and gives excellent low distortion midbass, and clean midrange that will rival many high buck speakers. It has better midbass output even sealed, but it to0 improves with a port.

Last edited by automaticmojo; 14th November 2012 at 05:17 AM.
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