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Old 7th April 2010, 12:02 PM   #1
ksporry is offline ksporry  China
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Thumbs down 2 or 3 way speaker for bi-amping

Ok, here's the deal:

I would like to build a set of high sensitivity speakers that would be bi-amp'ed. So effectively each speaker will have it's own amp that will drive both driver units (2-way).

The amps are Meng X1 tube amps with a quoted max power of 24W per channel. With a pinch of chinese salt I'd stick to 20W per channel.

I was considering a 2-way speaker set because this makes it very simple to leave out the crossovers from the speakers and only use a crossover for low, and for mid/high.

The crossovers would be passive 1st order crossovers, and mounted between pre-amp and power amp (actually, the Meng X1 is an integrated amp, but the pre-amp is a Yaqin MS-12B, and it's output is at line level, so that should work fine).

The method I considered for calculating the passive crossover would be deducted from this simple calculator: Guitar Pedals: R-C Filter Calculator

I realise this may not be the best method, but its simple/easy/fast/cheap, and considering this will be the first time I bi-amp a setup, as well as build a speaker set, I prefer simple. Less can go wrong, and troubleshooting/improvements will be easier.

My question is: Can anyone advice me of a suitable design that's simple and cheap (budget is around 200-300GBP for the whole speaker set). Also, for a given design, could someone advice me of the recommended crossover frequency cutoff for low and for mid/high for the suggested speaker design?

Cheers,
K
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Old 7th April 2010, 01:25 PM   #2
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The calculator you linked to does not include the input impedance.
"This calculator assumes a low source impedance, which usually is small enough that it does not change the corner frequency. " This is not an assumption that I would want to make. Here's a formula that includes the input impedance. PLLXO

As far as a cheap effecient two way that could work with a 1st order crossover? That certainly narrows down the field. I would maybe consider a "fullrange" driver crossed over to a prosound 12"-15" somewhere in the 200-600Hz range depending on the size of the fullrange driver. Also considering if the prosound driver has any nasty breakups in the 1-2kHz region, which would certainly be a problem with a 6db/oct crossover.
Joe
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Old 7th April 2010, 02:18 PM   #3
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Hi K,
I'm not very much into active, others can help better, but you have to start in somewhere looking for your complete set, or for the drivers only, for a start. So, I would suggest a very sensitive and lovely 2-way that you can later in time upgrade with a sub-woofer for more punch (I just donīt know how the low impedance tweeter works with a tube amp).

Woofer, FANE SOVEREIGN 12-200, SPL=98, Fs=45Hz
Fane sovereign 15-400 12-300 10-275 15-250
Fane International, loudspeakers and high frequency drivers designed for the professional user
http://www.fane-international.com/do...n%20Series.pdf

Tweeter, Vifa DX25TG-09-04, SPL=96.5, Fs=680Hz
The SEAS tweeters are very lovely too, Seas T25C003, SPL=91, Fs=600Hz
SEAS PRESTIGE TWEETERS
SEAS EXCEL TWEETERS

Last edited by Inductor; 7th April 2010 at 02:45 PM.
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Old 7th April 2010, 04:34 PM   #4
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Other tweeter candidates are,
Fostex FT48D Dome Tweeter
Sica Z009160 - LP 90.28/N92 TW 8 Ω 1.1"- 80W Dome Tweeter
Seas 29TFF/W 1" Dome Prestige Tweeter - H1318
GR-T6 Dome Tweeter (Not bad idea to have selected matched pairs)
The Seas T29CF001 - E0038 Dome Excel Tweeter Beast, SPL=93, Fs=550Hz. Cost no Object by Troels Gravesen.
Also the interesting SEAS Prestige 27TDFNC/GW (H1462)

Last edited by Inductor; 7th April 2010 at 04:50 PM.
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Old 7th April 2010, 05:10 PM   #5
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Quote:
Originally Posted by Inductor View Post
Tweeter, Vifa DX25TG-09-04, SPL=96.5, Fs=680Hz
Sensitivity 2.83V/1m 96.53 dB
DC Resistance Re 2.75 ohm

So for 1W, you'll get a little under 92dB.
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Old 7th April 2010, 06:19 PM   #6
ksporry is offline ksporry  China
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I can find drivers that have a high efficiency, but of course they need to go together with a cabinet that supports those drivers, and at the same time take into consideration that no crossover is fitted in the speaker.
Usually the behaviour of a speaker driver without a crossover is quite different from that of a speaker set that utilises a passive crossover.

As for input impedance of the amp, how do I determine that? Just put a multimeter on the input when it is on?
I also understand from Josephjcole's link that the low pass filter does not need to know the amp's impedance, only for the high pass?
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Old 7th April 2010, 07:35 PM   #7
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Quote:
Originally Posted by Brett View Post
Sensitivity 2.83V/1m 96.53 dB
DC Resistance Re 2.75 ohm

So for 1W, you'll get a little under 92dB.
Yes, yes, yes. Check the Audax TW025A28 Gold Dome Tweeter, measured at 0.5m (how much at 1m?)
http://www.madisound.com/catalog/PDF/TW025A28.pdf
and the hyper high sensitivity of the BEYMA T2030 - 95 dB, good option but for a 1.order I would chose less than 1KFs

K, you don't know yet if you can do it (unless you do it in active), as for BSC on the woofer you need some kind of passive components/inductor (no?) and for the tweeter you need a LF protection or cap. Also you are going to match both final sensitivities unless you do it with the amps/preamps.
Quote:
Originally Posted by ksporry View Post
Usually the behaviour of a speaker driver without a crossover is quite different from that of a speaker set that utilises a passive crossover.
All these drivers have very good behavior (if you pay attention).

Last edited by Inductor; 7th April 2010 at 07:52 PM.
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Old 7th April 2010, 10:56 PM   #8
form109 is offline form109  United States
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whats the Point of Bi-Amping a Speaker?....on Cheap mini systems the woofer is just Full Range.
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Old 8th April 2010, 04:26 AM   #9
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a better method of doing PLLXO:
Passive Line-Level Crossover
(edit: I see JJcole beat me to it)
for what you're proposing, I'd suggest using a full range driver such as the Fostex FF85K, crossed over at ~ 200Hz (or baffle step freq) to woofers of your choice will give max benefit of biamping
__________________
Impedance varies with frequency, use impedance plots of your drivers and make crossover calculations using the actual impedance of the driver at the crossover frequency

Last edited by PeteMcK; 8th April 2010 at 04:40 AM.
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Old 8th April 2010, 11:43 AM   #10
ksporry is offline ksporry  China
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Thanks Pete, I will consider that. Out of curiosity, to what extend does it matter what shape and size cabinet I use for the foster and low end driver? I would imagine I have to match the recommended volume of the manufacturer of the driver?
Usually (looking at Troels Gravensen's website) when making hi-end speakers, the drivers, cabinet and crossovers work together, so I'd imagine for optimisation the story becomes more complex. I guess I could start off with a basic shape that contains the recommended volume for the relevant driver, and chuck in a crossover between pre and power for teh 200Hz (if I go for the fostex).

Question:
1) How do I determine the input impedance of my amp?
2) How do I determine which frequency to use for the crossover? (Pete's sugegstion gives me a start, but if I were to use different drivers, the crossover frequency can change too...). Is there a rule of thumb for this?
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