FAST /WAW subs under MA drivers

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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!
 
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. .
 
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 :cool: 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.
 
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).
 
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I'm enjoying the 7.3's in a 10 liter bass reflex for a few months now, but all this FAST talk has made me sort of hungry..;-)


Few questions:

-The peerless 10 & 8 inch look great, and the price is good. What would be the differences soundwise between the two?
Somehow my gutfeeling tells me the 10 inch will go lower, but the 8 inch might sound a bit faster.

-I'm not able to use a minidsp (or i would need to build a new amp..), so a first order XO would need to do the trick.
What i get is a 5.09 mH inductor, and a 117 uF cap if i cross at 250hz, does this sound correct? I took the nominal impedances form the specsheets, however since one crosses at a certain point, doesn't that change the effective impedance?

-Are there some budget tricks to experiment with different crossovers? What i mean is for instance testing with electrolytics before plunging out big cash for audiophile grade xo caps? It is going to cost a few bucks this crossover as far as i can tell now..

And thanks all for the info in this topic, learned a lot!
 
I have not tried the 8" but the 10" works pretty well. There is a bit of efficiency difference between the two, but not much difference in deep response given the same size cabinet. The 10" is a really nice driver that can be crossed pretty high if needed (makes 1st order easy). The 10" will also provide more headroom than the 8".

A single 10" should work pretty well with an Alpair 7. For a 1st order at 250hz, 5mH on the woofer would be OK and you might just get a single 100uF (Solen makes one) for the Alpair 7. If I were building another system, I might use a 90 litre sealed box with a generous amount of that recycled denim insulation loosely packed.

YMMV.
 
Thanks Silverhairbp!
In your experience could the 10" work in a fully stuffed enclosure a bit under 40 liters? If i put that in a calculator i get a bump around 100 herz.

I probably might end up using the 8" although i like the idea of surface instead of excursion for bass a lot better.
 
IMO, the 7.3 is better matched with the Peerless 10" 830668 because of baffle step loss. The 10" will work in 40 litres sealed but will have a steeper rolloff down deep. F3 of around 43hz F10 in the upper 20s. Haven't tried a small box with the Peerless but modeling makes it look like there is less dynamic restriction with a larger box. Not a particularly good idea for deep bass unless the intent is to restrict driver excursion.

And I agree. My personal preference is for shorter excursion with larger speaker area.
 
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