Tweeter amp around $100?

[Frosteh]

I'm going to be bi-amping my mains and I'd like suggestions on the best amp I can buy for about $100. The tweeters are the SB Acoustics SC25STC-C000-4 and are rated to 120W, though I doubt I'll ever run them that loud. Any suggestions? Rack mount would be preferable, as I already have an A500 and will be putting everything in a rack in the end.

[Frosteh]

I was thinking of using the Sure 2x100 TK2050. Do you think this is powerful enough? http://www.parts-express.com/pe/show...number=320-300

Tweeter Datasheet
http://meniscusaudio.com/images/SB25STC-4.pdf

[picowallspeaker]

What is the signal path before the amplifier ?
Are you going to use passive crossovers after them ?
Or some semi-active way ,where the amplifier is limited in its bandwidth by some RC-CR
net at its input ?
The easiest choice would be an LM 1876 ( or 2 X LM 1875 ) amplifier ,with 20 W or the classic LM 3875 for 50 W ( LM 4780 is stereo ).
Any low power discrete amplifier , also an Op-amp driving two darlingtons would do the job .
Also ,for being sure that no harming DC would go thru that tweeter , a single supply amplifier with a lowish value output capacitor
(470 uF ? )

[Frosteh]

Originally Posted by picowallspeaker

What is the signal path before the amplifier ?
Are you going to use passive crossovers after them ?
Or some semi-active way ,where the amplifier is limited in its bandwidth by some RC-CR
net at its input ?
The easiest choice would be an LM 1876 ( or 2 X LM 1875 ) amplifier ,with 20 W or the classic LM 3875 for 50 W ( LM 4780 is stereo ).
Any low power discrete amplifier , also an Op-amp driving two darlingtons would do the job .
Also ,for being sure that no harming DC would go thru that tweeter , a single supply amplifier with a lowish value output capacitor
(470 uF ? )

I'll be using a DCX2496 as an active xo before it. 2kHz LR4 highpass. Given that the tweeter is rated to 120W and will be paired with an SB17NRX do you think 50W will be enough?

[col]

The Sure TK2050 boards are good but the HifiMediy ones are better, also they have speaker protection.

col.

[weltersys]

Originally Posted by Frosteh

I'll be using a DCX2496 as an active xo before it. 2kHz LR4 highpass. Given that the tweeter is rated to 120W and will be paired with an SB17NRX do you think 50W will be enough?

You have a bit of an “upside down” woofer / tweeter balance, the tweeter is less efficient, but handles twice the power of the woofer.

The tweeters are 1 dB less efficient (91 dB at 4 ohm is 88 dB 1 watt one meter equivalent) than the woofers, so will need another dB of power level to balance.

With 100 watts, the tweeter will be at 108 dB , while the woofer would be 109 dB at 100 watts, though it is only rated for 60 watts.

Since the A500 is rated at 160 watts into 8 ohms, looking for a tweeter amp of similar power at 4 ohms would not be unreasonable if you want to have no clipping on HF transients.

Art Welter

[picowallspeaker]

yes Art , but the treble portion of a 109 dB music signal would be around 30 % of total power , usually is like that when calculating amp ratios for multi-way .

[Frosteh]

Originally Posted by weltersys

You have a bit of an “upside down” woofer / tweeter balance, the tweeter is less efficient, but handles twice the power of the woofer.

The tweeters are 1 dB less efficient (91 dB at 4 ohm is 88 dB 1 watt one meter equivalent) than the woofers, so will need another dB of power level to balance.

With 100 watts, the tweeter will be at 108 dB , while the woofer would be 109 dB at 100 watts, though it is only rated for 60 watts.

Since the A500 is rated at 160 watts into 8 ohms, looking for a tweeter amp of similar power at 4 ohms would not be unreasonable if you want to have no clipping on HF transients.

Art Welter

This I understand, however both drivers are rated at 4ohms, giving the A500 230W of power. Would it be better to switch the A500 to the tweeters and build a new amp for the woofers? I have a 12V toroid laying around and I could probably throw together a pretty nice amp using stuff from ebay. About $80 not including a case. Only problem is I'd have to wait for parts to ship from China. The amps have been highly regarded, though.

[weltersys]

Originally Posted by picowallspeaker

yes Art , but the treble portion of a 109 dB music signal would be around 30 % of total power , usually is like that when calculating amp ratios for multi-way .

I would not disagree with that ratio (it depends on the xover frequency of course) for a power average, but peak power requires the same power for both high and low if they are of the same sensitivity.

[weltersys]

Originally Posted by Frosteh

This I understand, however both drivers are rated at 4ohms, giving the A500 230W of power. Would it be better to switch the A500 to the tweeters and build a new amp for the woofers? I have a 12V toroid laying around and I could probably throw together a pretty nice amp using stuff from ebay. About $80 not including a case. Only problem is I'd have to wait for parts to ship from China. The amps have been highly regarded, though.

If your woofers are 4 ohms, same advice, only higher power, look for another amp similar in power at 4 ohms to the A500.

That said, if the SB17NRX35-4 is rated at only 60 watts, it will probably be suffering from around 3 dB power compression if you hit it with many 230 watt peaks, so 115 watts or so of power for the tweeters should be adequate, as with less average power they will not have much thermal compression .