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Old 17th August 2010, 11:37 PM   #1
sreten is offline sreten  United Kingdom
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Default 3 Way 100dB/W PA type speakers

Hi all,

I've gotten involved in a friends project of the type I usually avoid,
PA speakers are not my bag, but if your going to do it, do it .......

Bass end is a 4 ohm 15" or 18" in a rearbass scoop bin with the driver on the baffle.
The major issue is cabinet width, its limited to around 23". (to get through a door)
In will be crossed over actively around 200 to 240Hz to what I reckon
will be a MTM mid/treble array 8 ohm each mid and 8 ohm treble.
(The array is placed vertically beside the bass driver).
(The two mids should get near 100dB/2.83V I reckon.)
I reckon 5" mids and a horn loaded treble unit.
(I recommended a 15" + the classic big mid /treble horn, but .....)

Amplifier will be a 4-channel car jobby driven by a big battery. 2 channels
bridged for the bass, and a channel each for the mid and treble. Bass/mid
c/o is using the amplifier facilities, but the mid/treble needs some thought.

Suggestions for good high value drivers for each part would be welcome,
and links to any plans for front bass scoop bins would help, and any good
ideas regarding the endeavour would be most appreciated.

Also note parts will be sourced in the UK, so the best suppliers appreciated.

Comments on decent high value 4-channel amp car amps would help, the
silly power specs are not an issue, real specs over 100W bridged 4ohm and
over 50w per channel into 4 ohms. Tweeter power I expect not to be an
issue. This should help with the 70AmpereHour battery life.

rgds, sreten.

Last edited by sreten; 18th August 2010 at 12:03 AM.
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Old 18th August 2010, 05:43 AM   #2
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I've also been interested in what the best of autoClassD can deliver but have been concerned about cold cranking amps. How much can they deliver on an instantaneous basis to a reactive 4ohm load.

Having used Hypex UcD's in a similar mains powered system I can vouch for their quality. But you'd need expensive 12-48V SMPS. Any experience on autoClassD off Pb cell bank vs ClassD w/ mains line input SMPS??

Both need rail generating SMPS but any comments on step down vs step up?


All I can say is I've had good success with step down to 60V (although here it's effectively 1:1) but suspect the 12V - 60V could be problematic.

P.S. agree on your driver choices.
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Old 18th August 2010, 09:51 AM   #3
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41Hz Audio:AMP9 kit. 14.5V max, low profile

These guys make some really good amps. I built the amp6-b, and it's fantastic...

Anyway, Your Search Results | CPC - good supplier, I use them to get hold of some Visaton stuff. They also do some Eminence, Celestion, B&C and PD gear.
I'd also have a look on ebay for older gear - we've got some McKenzie PA speakers (12"+tweeter), and the efficiency is circa 98dB. Sound nice, but no low bass.
Newer PA gear tends to be less efficient because power is so cheap. That said, I seem to remember the Eminence Alpha 6 to be 99dB@1w.

You can buy 230v power adaptors for car use (I've seen them rated at 300w), so you could use a "proper" amp, with more volts.

Just seen this: HKM|XF-130-534PLUG|LOUDSPEAKER, CAR SPEAKER, 130MM | CPC could be used as a mid, but more info is needed.

What's the budget of the project?
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Old 18th August 2010, 12:22 PM   #4
sreten is offline sreten  United Kingdom
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Hi,

Cabinet design is going to be based on

http://www.dancetech.com/file-librar...p_12_15_18.pdf

or

Speakerplans.com

Currently considered
PDN.18SB40 18" bass unit (200)
APT 80 treble unit + c/o unit (50)
mid unit(s) up in the air (they insist on 4 ohm) up to 100 ?

Amplifier will be a 4 channel car unit driven by a battery.

Chris :
Thanks for the driver link, but I simply do not believe the sensistivity.

rgds, sreten.
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Old 19th August 2010, 12:07 AM   #5
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Quote:
Originally Posted by sreten View Post
...
Chris :
Thanks for the driver link, but I simply do not believe the sensistivity.

rgds, sreten.
It's possible, sometimes manufacturers address peak dB, not flat amplitude curves. The same with lower frequencies and subs. Just not high fidelity.
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Old 19th August 2010, 12:48 PM   #6
Pano is offline Pano  United States
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Can you get RCF drivers there at a reasonable price? Made for PA work and usually good value for money and durability.

Or look at the P.Audio or Selenium lines.
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Old 19th August 2010, 01:20 PM   #7
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by sreten View Post

Comments on decent high value 4-channel amp car amps would help, the
silly power specs are not an issue, real specs over 100W bridged 4ohm and
over 50w per channel into 4 ohms. Tweeter power I expect not to be an
issue. This should help with the 70AmpereHour battery life.
to get your 100W into 4ohm from a bridged pair you need a spec that is 50W into 2ohm speaker load. That might be equivalent to car audio specification of 100W into 1r0.

50W into 4ohm should deliver that 50W into your paralleled 5inch Mid drivers and 30W into the 8ohm treble horns. Total drawn maximum power ~150W from an smps that should be rated to about 200W continuous for 4channels of 50W continuous and 100W transient.

What about replacing the dual 5inch with a single high efficiency 8inch to 12inch mid driver?
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Old 19th August 2010, 01:25 PM   #8
sreten is offline sreten  United Kingdom
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Quote:
Originally Posted by AndrewT View Post
What about replacing the dual 5inch with a single high efficiency 8inch to 12inch mid driver?
Hi,

For this type of speaker baffle size is very constrained, and as mentioned
before a door way fixes the maximum width. An 8" would fit but most
are 8 ohms, they insist on the bass and mids both being 4 ohm.

rgds, sreten.
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Old 19th August 2010, 02:05 PM   #9
wg_ski is online now wg_ski  United States
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Quote:
Originally Posted by Iain McNeill View Post
I've also been interested in what the best of autoClassD can deliver but have been concerned about cold cranking amps. How much can they deliver on an instantaneous basis to a reactive 4ohm load.

Having used Hypex UcD's in a similar mains powered system I can vouch for their quality. But you'd need expensive 12-48V SMPS. Any experience on autoClassD off Pb cell bank vs ClassD w/ mains line input SMPS??

Both need rail generating SMPS but any comments on step down vs step up?


All I can say is I've had good success with step down to 60V (although here it's effectively 1:1) but suspect the 12V - 60V could be problematic.

P.S. agree on your driver choices.
As far as instantaneous current capacity, Pb's are pretty good. Add 20-100kuF of ordinary soup-can cap (expensive car audio caps are overkill and a waste of money) close to the amp and you're good to go.

Stepping up from 12V is easier than an offline SMPS. You can get away with an awful amount of slop in the design and layout compared to offline and not blow things to kingdom come. What they put in low-end "2000 watt" car amps is pretty pathetic - and for the most part work reliably. High core losses, high switching losses. They use toroids in push-pull, which you can't even get away with in an offline SMPS. To get the efficiency into the 95% range you've got to be more careful. But if you've built safe/reliable mains operated SMPS's you should have no trouble with a 12V step-up.

@sreten:

Are the B&C mid drivers too rich for your blood? You could probably live with the 6.5".
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Old 19th August 2010, 02:38 PM   #10
Pano is offline Pano  United States
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I would use 2 Eminence Beta-8 drivers for the mid section. Put a horn between them.
It's a surprisingly good driver and 2 will give you 4 ohms and lots of SPL.

Get a good woofer, that is what will take the most abuse.
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