FAST subs under MA drivers

[murio]

Originally Posted by chrisb

Too many options, not enough time build 'em all, or post about all that we do complete

You might well get away with crossing the 7.3s even lower than 200Hz, but the question of how to go about the XO is always tricky - depending on the relative sensitivity of drivers, cost of passive components for such filter points can approach those of one of the drivers. Enter active bi-amping

Would this be for music only - and if so what sources/amplifier type - or for a multi-channel or PC based system? Those questions relate to the manner / ease with which the XO can be achieved and adjusted to suit driver / room situation.

I am using equipment for music only. I have king rex t20u T-amp. conected to pc. Now i am using 7.3 as a full range and the sound is great! 15w amp is excelent partner for this speakers! But now i am moving to bigger room so i decided to go FAST. Of course i woluld buy stronger amp. for this sistem. Excuse me for being amateurish but i dont know what thoes XO means! Can you explain me!

[chrisb]

Originally Posted by murio

I am using equipment for music only. I have king rex t20u T-amp. conected to pc. Now i am using 7.3 as a full range and the sound is great! 15w amp is excelent partner for this speakers! But now i am moving to bigger room so i decided to go FAST. Of course i woluld buy stronger amp. for this sistem. Excuse me for being amateurish but i dont know what thoes XO means! Can you explain me!

You might not necessarily need a much higher powered amp for the 7.3, particularly if you use a 2-way line level instead of passive XO, and drive the woofer portion of the FAST system is directly by separate amp.

The much lower XO frequencies typically implemented in a FAST system ( i.e. around or below 300Hz) require fairly high value passive components - for example a simple 1st order for both 8 ohm drivers at 300Hz requires 66mF cap and 4mH coil. For those of us who prefer film to EL caps in our passive networks, those types of values can get pricey, and the results might still not equal those of a well dialed-in simple active bi-amp set-up. .

[tuxedocivic]

Murio, I'd go with a minidsp. Extremely good bang for the buck and an excellent user interface. An absolute snap to set up.

I'm not sure I'd use a Wavecore 6". Seems like there would be better bass makers out there for less money Not that there is anything wrong with them, but they're meant to reach out to a typical dome tweeter around 2000hz. They give up bass and affordability to do this.

[planet10]

Originally Posted by murio

what does XO means!

XO = Cross-over

dave

[murio]

Thanks guys! I will studdy little bit more about minidsb. Maybe not bad idea!

[silverhairbp]

Finally got past CES / THE Show and the flu. Resumed some listening to the Peerless drivers.

Short version: The Peerless 830668 drivers used either singly or two per channel work very well in a sealed cabinet with a full range driver.

I've used two different woofer configurations with the CSS FR125SR. The cabinets are sealed, the dual woofer has both drivers in a single chamber within the cabinet even though they have different operating ranges.

Background notes: This driver operates very smoothly even over 2khz so there is no particularly critical crossover point to a full range driver. Find a crossover point that fits your taste and it will likely work fine. For example, in one set-up, the Peerless driver was crossed to the FR125 at around 2.5khz without any nasties working their way into the music but with some loss of detail. This extended response also allows the use of a first order passive crossover (cap and choke, with resistors on the FR to balance) which I personally favor over the alternatives.

The first configuration uses a single Peerless 10" driver in just under 3.75 cu ft (around 100 litres) loosely stuffed with denim insulation (30"h x 18"d x 13 1/2"w built from 3/4" MDF). The results are very good with the driver going comfortably down to a little below 30hz in room. Very nice with good punch and fairly deep response. Integration with the FR125 was easy and a simple first order crossover worked pretty well. I put a couple of ohms on the FR to help match the level. Ended up with a quite pleasing sound. Very musical. I played around with the crossover points from 180hz to 800hz with generally good results. My personal preference was at 240hz first order.

The second uses two 830668 drivers in about 7.5 cu ft (around 215 litres) loosely stuffed (48"h x 24"d x 12"w built from 3/4" Baltic Birch plywood. OK, I know the dimension ratios aren't too good, but this was just a prototype.). I used the same crossover on one of the woofers as in the single system (the one mounted higher in the cabinet) to at least give me a starting point. I then put a large choke on the second Peerless driver (started with 12mH and ended up with over 15mH). This gave more reinforcement to the deep bass. Interesting results. The system went much deeper, but had a predictable rise below 70hz. Fun to listen to, but seemed MUCH more sensitive to room placement. I could not measure the -3dB point since my equipment only goes down to 20hz. It was below that in room.

The dual woofer system is a monster and would make a very desirable woofer system for a HT with a full range driver such as an Alpair 10.2 (which might need 3dB of padding, maybe more to balance the FR with the woofer system). With careful room placement, it works well with classical music and acoustic jazz. My suggestion with a full range driver would be to select a bit higher first order crossover point (300hz - 800hz) to provide a little better headroom and safety margin for the fr driver if it's going to be used in higher output systems. YMMV.

These results using the 830668 woofers with a CSS FR125SR will probably only be a guideline for integrating with a Mark Audio driver. One of the nice things about this hobby is that everyone can develop their system to their own tastes.

(My equipment: Modified VPI TNT 2 turntable, Jelco SA-750D arm, Lyra Clavis da Capo cartridge, Herron VTSP-1a pre-amp, Herron VTPH-1mc phono stage, Herron M150 amps (6), Herron CD player (non-production), Herron interconnects, my own formula speaker cable).

[planet10]

Originally Posted by silverhairbp

My personal preference was at 240hz first order.

~ 0.707 times the nominal baffle step -3dB

dave

[silverhairbp]

Originally Posted by planet10

~ 0.707 times the nominal baffle step -3dB

dave

Hadn't considered that. Actually, didn't even realize there was a relationship.

[planet10]

Somehow, somewhen, i picked up the idea that when using the woof to mid XO to compensate for BS that the XO would fall somewhere between (root 2)/2 & 1 times the BS F3.

dave

[silverhairbp]

Sounds more reasonable than some of the 10 x BS related to cable design I heard at THE Show. I usually ended up with 1 x the available wine.