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Old 4th September 2007, 11:47 AM   #1
OzMikeH is offline OzMikeH  Australia
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Default Active XO Bi-amping with Trends TA10.1

My first limitation is while under warranty I can't mess with the insides of my amps... yet. Once I'm sure there are no defects I'll start tinkering with their insides.

The speakers: Modded Fostex Fe207E (95dB/w) with FT17H super tweeters (98.5dB/w) Crossover frequency is 10.3kHz, chosen both due to driver specs and because hearing is less sensitive than at 8kHz.

Shopping list:
2x Trends TA10.1, 2x ESP Project 09 active 24dB/oct line level crossover boards, 1x ESP Project 05B power supply with muting.
1RU rack case, toroidal 15-0-15 trafo, assorted bits.

The game plan:
Single fused IEC power connector via switch, feeds 15-0-15 trafo and both stock Trends power supplies inside the box. the two T-amps sit on top connected to cables running through grommets in the lid. Each amp feeds one speaker Hi and low for increased channel separation and plenty of power supply headroom. Volume controls bypassed.

Crossovers: separate ESP P09 boards on either side of the chassis, Stereo 2-way is possible on one board but I may run a 50Hz XO to subs later on. Op-amps are OPA2134 all running unity gain. Deleted 1uF capacitors on the output of the XO because the trends amps have input caps.

Output: Bass&mid effectively straight out. Treble fed via 30uF motor start capacitor in the rack case bypassed with 1uf metal-poly cap. This is purely for DC protection, phase offset above 10k into 8 ohms should be close to zero. To idiot-proof it I'm using 4 pole speakon connectors for the speaker cables. The wires on the speaker terminals on the amps will be routed through the rack case to the connector on the back

XO power supply and muting: Power supply for opamps is linear regulated +/- 15 with power up & loss of AC muting relay drive. 4 separate miniature spdt muting relays connect the XO outputs (and t-amp inputs) to ground via 1uF.

I ordered a bunch of 1000uF low ESR caps as well, Would it be advisable to put these across the Trends power supplies close to the amps?
If so how many uF worth of inrush current would the stock power supply handle?
I have ordered enough caps for 10,000 uF per channel. I may replace the standard Trends supplies with dual linear supplies later on. Batteries aren't an option for me.

Any suggestions?
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Old 5th September 2007, 05:24 AM   #2
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I predict that you will find the ESP 4th order XOs subtract too much to be useable.

dave
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Old 5th September 2007, 08:31 AM   #3
Vix is offline Vix  Yugoslavia
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Hi,

Introducing all those opamps (ESP project 09) in a signal path will surely degrade the sound quality. The best solution is to buy a single Trends TA 10.1 amp.

With a fullrange speaker and a tweeter crossed high, there is little benefit in biamping.

Pour your money for a single 12 v 7-11 Ah gel battery, and buy a charger.

Build a switch so the charger gets disconnected when TA amp is connected and vice versa.

Also, use Dave's single-strand cat-5 based speaker cables.

You'll spend less, get more.

Regards,

Vix
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Old 5th September 2007, 12:02 PM   #4
Pano is offline Pano  United States
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Going rabbit hunting with a Bazooka, are you Mike?

I have to agree with Dave and Vix. An active crossover you do not need, at least not for this. The whole setup sounds like way overkill. And your likely to kill the music and enjoyment along with it.

The beauty of your Fostex "almost full range" driver is that it will be easy to crossover to the tweeter. You probably only need a single cap on the tweeter. Maybe a cap and a resistor. Keep it Simple.

If you want an active sub later on, that's no big deal. But for a Fostex Fe207E and high crossed tweeter? Easy - passive.

As for the other stuff, 1000uF is no big deal at 12V. I routinely use 2x2200 or more. And yes, you can add them across the stock power supply. I sometimes add 1 or 2x 10,000uF.

The stock PSU with for Trends is OK, but you can do better. The stock unit tends to sound a bit "sour" as my wife said. It's OK, until you hear a better one.

Don't discount a good regulated linear supply, as you planned to build one for your unneeded crossover. A nice 13V regulated will work well. Or find a nice SMPS. I've had good luck with DVE brand "line lumps" and both XP Power and Skynet open frame supplies.
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Old 5th September 2007, 12:08 PM   #5
OzMikeH is offline OzMikeH  Australia
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Thanks guys. Most helpful.
But I really like blowing things up.

I've already bought the amps so I'll just use a single channel of each amp for each channel with my existing XOs.
Anyone want to buy a T-amp?
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Old 5th September 2007, 06:14 PM   #6
rajacat is online now rajacat  United States
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Pano,

Do you think that there is any benefit to biamping single driver speakers that have two drivers per side in a dipole arrangement which are provided with separate connectors for each driver. Each driver has it's own enclosed box contained within a single cabinet. Omega Hemp Bi/dipoles are the speakers I'm referring to. It seems to me that I'm getting better channel separation but I've been implementing so many changes to my system recently, that I'm losing track of their effects.

Raj
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Old 5th September 2007, 07:02 PM   #7
rajacat is online now rajacat  United States
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Quote:
Originally posted by rajacat
Pano,

Do you think that there is any benefit to biamping single driver speakers that have two drivers per side in a dipole arrangement which are provided with separate connectors for each driver. Each driver has it's own enclosed box contained within a single cabinet. Omega Hemp Bi/dipoles are the speakers I'm referring to. It seems to me that I'm getting better channel separation but I've been implementing so many changes to my system recently, that I'm losing track of their effects.

Raj



p.s. I'm not just interested in Pano's opinion. Other views will also be appreciated.

Raj
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Old 5th September 2007, 08:08 PM   #8
Pano is offline Pano  United States
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rajacat - yes, I think it would be a good idea.
Same for Mike. One amp per side.
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Old 10th September 2007, 09:38 AM   #9
OzMikeH is offline OzMikeH  Australia
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One thing I should mention, One of my aims was for a phase coherent crossover to the super tweeter.
It sounds good with just a cap and resistor, I want to see if I can make it sound better. My new cabinets will have the super tweeter very carefully positioned.
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Old 11th September 2007, 09:47 AM   #10
OzMikeH is offline OzMikeH  Australia
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Does anyone have any other suggestions for an active XO? I really want to try to keep the phase alignment right and I want steep slopes. Unfortunately I have freakishly sensitive high frequency hearing.

Amps arrived yesterday, had some minor issues, resolved already, COEM Audio's customer service is damn good.
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