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Quick help: 15" Brahma vs. AV-15


D-Rex

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On 11/4/2004 12:44:24 AM Jay481985 wrote:

brahmas are for cars.....

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I have been cruising the net and that is the only application I have found for the Brahmas as well...

I will stick to my AV-15 plans then...

Thanks,

Dallas

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The biggest difference between a "car audio" driver and a home one are the compromises the designer feels are most important to it's potential customers. The drivers will technically work in either situation, but give you different trade-offs based on the chosen T/S parameters. Will you be building a vented enclosure or a sealed one?

As a generalised (but not mandatory) rule:

Car audio: enclosure size is of utmost importance... so bass extension and efficiency are often compromised

Home Audio: size is less at a premium so different compromises can be considered. Drivers like a Tempest use a large enclosure for good bass extension and pretty good efficiency. Some customers still want a small enclosure... so drivers like the Tumult trade efficiency for enclosure size.

The Brahma is an odd car-audio driver as it seems to have higher than average (for car audio) efficiency... but will also require a larger than average vented enclosure.

With 1000W the AV15 will be excursion limited if you build a vented enclosure.

My advice is to model both drivers in a program like WinISD and see what's most important to you.

Rob

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On 11/4/2004 1:53:40 AM formica wrote:

The biggest difference between a "car audio" driver and a home one are the compromises the designer feels are most important to it's potential customers. The drivers will technically work in either situation, but give you different trade-offs based on the chosen T/S parameters. Will you be building a vented enclosure or a sealed one?

As a generalised (but not mandatory) rule:

Car audio: enclosure size is of utmost importance... so bass extension and efficiency are often compromised

Home Audio: size is less at a premium so different compromises can be considered. Drivers like a Tempest use a large enclosure for good bass extension and pretty good efficiency. Some customers still want a small enclosure... so drivers like the Tumult trade efficiency for enclosure size.

The Brahma is an odd car-audio driver as it seems to have higher than average (for car audio) efficiency... but will also require a larger than average vented enclosure.

With 1000W the AV15 will be excursion limited if you build a vented enclosure.

My advice is to model both drivers in a program like WinISD and see what's most important to you.

Rob

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I am wanting a vented enclosure. I am wanting tuning capabilities down to 18 hz with a modest sized box. It sounds like the AV-15 would be better for my purposes EXCEPT, are you saying the 1000W amp will be too much for the AV-15? Will it bottom out?

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Rob,

I have seen your sub that you built with the AV-15. How well do you like it? How much power are you providing to it? Do you think a sealed sub would be better with a 1000W amp? Might you be available to discuss the dimensions needed for the AV-15 sub?

Thanks,

Dallas

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I've run a couple of box designs in WinISD and have found that you can pretty much run the AV12/AV15 full power all the way down to 10Hz without exceeding Xmax. Granted, this was a sealed box. I opted for the Blueprint 1503, which is probably more similar fo the Brahma than the AV15 or Tempest line... it needs a big box, but works quite well. It has more throw than the AV15 and also cannot really bottom out... ever. It can travel about 2.9" or something like that before it hits its mechanical limit. The AV15 is a little less than this, but nonetheless, "bottomless". Under extreme HT usage, it still won't see all its potential, probably.

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On 11/4/2004 10:57:25 AM D-Rex wrote:

It sounds like the AV-15 would be better for my purposes EXCEPT, are you saying the 1000W amp will be too much for the AV-15? Will it bottom out?

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With a 1000W in a vented enclosure, it can bottom out at a frequency slighty higher than your port tuning. I don't think there is such a thing as "too much"... as I rather call it "headroom" You will have to use discretion and setting the volume and may not squeeze every last watt out of your amp... but you will be operating the amp within it's optimal range.

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On 11/4/2004 10:27:31 PM Rdmarsiii wrote:

The AV-15 cannot physically bottom out. It will run out of surround before it can.

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ummm... with 46mm of maximum travel... I can assure that it CAN bottom out.

I'm running mine with 750W, in a 6ft3 enclosure tuned to 19.5Hz (measured). I have bottomed it out with test tones around 25Hz but over 120db in room. With music sources, the amp will just begin clipping as the driver approaches its excursion limits.

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On 11/4/2004 4:57:01 PM D-Rex wrote:

Do you think a sealed sub would be better with a 1000W amp? Might you be available to discuss the dimensions needed for the AV-15 sub?

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I prefer the ported sub. My AV15 replaced a sealed sub... and it has significantly better bass extension and more SPL capabilities. Port noise has been a non-issue for me... although my home's structural noise has.

My next sub will be an Infinite Baffle... and I just ordered 4 15" drivers for it. I'm hoping it'll be enough... but I guess I can always expand it. 1.gif

Post any enclosure questions... I can tell you what I'd do differently. You probably already seen my AV15 sub is ready... thread.

Later...

Rob

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On 11/5/2004 12:19:18 AM tpg wrote:

I've run a couple of box designs in WinISD and have found that you can pretty much run the AV12/AV15 full power all the way down to 10Hz without exceeding Xmax. Granted, this was a sealed box.

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It becomes thermally limited in a sealed enclosure... but is excursion limited in a vented enclosure.

Also note that the T/S published will vary a little from driver to driver... so the modeling isn't the precise. If you look up some of my older threads, I was surprised by how far off the measured port length was from the calculated one to achieve my tuning.

Rob

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This is true... GAH! I never remember everything that is important when I am typing something. 14.gif

I agree with the ported sub replacing the sealed sub as you said earlier. I did the same thing and am very surprised with the results... I like the ported better.

Surely you'll never give the driver 1000W anyway... I thought mine needed 1000W because its power handling is that. I measured it the other day and it was putting out 50W peaks or so during loud music...

You bottomed out the AV15?! The Xmax is 46mm total, yes... but Xmech is something like 60mm. You must have been running it pretty hard... The only problems I ever run into are clipping my sub amp... but it is a PA amp, and very much not intended for sub use, as I've figured out. Its clipping light comes on when it is putting out 100 or so watts into 8-ohms in peaks... and it is rated for 300+ watts at 8-ohms.

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On 11/5/2004 12:43:44 PM tpg wrote:

You bottomed out the AV15?! The Xmax is 46mm total, yes... but Xmech is something like 60mm. You must have been running it pretty hard... The only problems I ever run into are clipping my sub amp... but it is a PA amp, and very much not intended for sub use, as I've figured out.

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I'm not proud to say it, but it happened twice. Test tones can be torture, and I accidentally repeated it with some subsonic music (Breakbeat Era). I'm not sure what the Xmech was on the second batch of TC sound drivers (what i have), but I doubt the cone traveled much more than the 46mm.

BTW, the woofer still tests the same, so I'm pretty sure it didn't sustain any damage... but it does make one jump for the "mute" button. I do admit that I enjoy it loud... but amp clip light didn't flash "on" either time.

I'm also using a Pro amp (JBL MPC200 which is a rebranded QSC CX4). I have only seen the clip light blink "on" once in a blue moon, but ironically it didn't bottom the woofer.

Rob

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