Moonshine? And here was me growing up wishing I was one of the Duke boys! the car, Jessie, jessie and moonshine.
I digress - at one point we turned the speakers around to assess the bass with a little less of the 10KHZ sparkle, it was surprising how much of the HF came out of the upper port, you would have been forgiven for not believing that the speaker was rear facing.
Do you think that a front facing port, from the lower chamber would run the risk of canceling out LF response due to phase, or add a little? The rooms we were in were damped acoustically so that rear facing ports were throwing the signal into absorbing material. This was still an improvement on my lounge and its bass hungry floor, but perhaps front facing would help even out the rsponse a little?
Any thoughts most welcome.
I digress - at one point we turned the speakers around to assess the bass with a little less of the 10KHZ sparkle, it was surprising how much of the HF came out of the upper port, you would have been forgiven for not believing that the speaker was rear facing.
Do you think that a front facing port, from the lower chamber would run the risk of canceling out LF response due to phase, or add a little? The rooms we were in were damped acoustically so that rear facing ports were throwing the signal into absorbing material. This was still an improvement on my lounge and its bass hungry floor, but perhaps front facing would help even out the rsponse a little?
Any thoughts most welcome.
Scottmoose,
Thanks for taking the time to respond to my post in detail - I understand the nuances if your design much better now. You are right - I have been running dual Vifa drivers for sometime now and like them very much. Apart from a little sensitivity to standing up and sitting down impacting how the sound varies they are great. I run them in parallel to get the boost in efficiency so accept the limitations that come with it. Seeing how your design is in series and with a cap got me curious so I ask from a standpoint of wanting to learn more - not from standpoint of pouring water on your design. If it came across like that - I am sorry. No offense intended. I am running some sims of my dual Vifa's in series with and without the cap to see the effect and it is interesting how the lower cone and upper cone diverge. Above 2 kHz the cap essentially shorts to ground and the speaker sort of reverts back a single driver as freq goes higher. An interesting cross over.
Cheers,
X
Thanks for taking the time to respond to my post in detail - I understand the nuances if your design much better now. You are right - I have been running dual Vifa drivers for sometime now and like them very much. Apart from a little sensitivity to standing up and sitting down impacting how the sound varies they are great. I run them in parallel to get the boost in efficiency so accept the limitations that come with it. Seeing how your design is in series and with a cap got me curious so I ask from a standpoint of wanting to learn more - not from standpoint of pouring water on your design. If it came across like that - I am sorry. No offense intended. I am running some sims of my dual Vifa's in series with and without the cap to see the effect and it is interesting how the lower cone and upper cone diverge. Above 2 kHz the cap essentially shorts to ground and the speaker sort of reverts back a single driver as freq goes higher. An interesting cross over.
Cheers,
X
Comment post #17: Think it is natural member xrk971 asked deeper questions.
Because of suddenly it was not only a good diy home speaker, but a speaker to do the art in studio and beat others (ultimate winner against Genelec, ATC and the dynaudio). This done with setup of two drivers box and a cap. I am only diy but think it needs further correction to be a reference producer, oposit use at home do as you like. This is friendly meant, and read i use Alpair dayly (10.2M) and very satisfied.
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Because of suddenly it was not only a good diy home speaker, but a speaker to do the art in studio and beat others (ultimate winner against Genelec, ATC and the dynaudio). This done with setup of two drivers box and a cap. I am only diy but think it needs further correction to be a reference producer, oposit use at home do as you like. This is friendly meant, and read i use Alpair dayly (10.2M) and very satisfied.
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Not at all. Please accept my apologies if my original post seemed a little 'strong' -re-reading it, it didn't come over as very polite at all. Not intended that way; I'm shooting about between different things so much at the moment I don't get as much time as I'd like to write & edit. Which is no excuse for rudeness.
Anyway, right, the main changes are of course on the vertical axis (assuming they're disposed vertically of course!); extent varies with the driver, partly diameter but also innate dispersion characteristics. The 7.3 is as large as I'd go for twin drivers.
Spot on. For some reason it's not seen all that often, presumably because series crossovers aren't as popular as parallel -essentially it's a variation thereof. By (very) general analogy, a distant relation is the cascaded 2.5 way parallel filter Jeff Bagby popularised, where you have the large baffle-step inductor after the low-pass for the top woofer. Where they score is that you've got a reasonable level of control over what the low-passed driver is doing, and the phase relationship remains good. And of course, in the case of the series wired drivers, if you're starting with a unit that already has a slightly low impedance, you don't end up with something that's a nightmare to drive. < 3ohms gets very awkward (see the Apogee Scintilla for the genuine 1ohm amplifier killer -Krells quaked at their name. The Linn Isobarik wasn't much better). A couple higher than normal? Not too much of a problem providing it's not over-reactive. This is relative of course -large increases & you'll run into the problems you mention, unless you've a specialist amp.
Cheers
Scott
Right. Wideband based speakers of various types are used in studios, especially smaller ones, more often than many realise & they can be a very good solution. But, as noted, it depends on what it is that's wanted & what they'll be used for. As with any speaker, it needs to be appropriate for the requirements.
Closer to 300 Hz.Making part of your later prose moot.
But it is a perfect match. And as things go, not all that expensive.
Blow 300 Hz. Typically half the amp distortion, and likely the case that the studio already has amps that even at half the power are big enuff for the A7. Ampsare more likely current limited, and the higher impedance helps.
dave
Good catch, octave I mean...
Maybe I should be more terse
And present my comments in verse?
When I modeled the dual A7.3 in a sealed cabinet wired in series with a 70uF cap across the lower driver, I get a response that falls off starting at 2 kHz. How did you get 300 Hz?
Attachments
Scottmoose will know but I suspect it is because the cap is in parallel to the driver rather than something wrong with the sim. It is a pretty straightforward addition of a cap across the driver nodes - one line of code. The RC time constant for 5 ohms x 70 uF is = 0.7*5*70E-6 = 0.245 ms or about 4kHz.
Given the wiring of the drivers, FR should be the same as a single driver (voltage amp assummed) If not something is wrong with the sim.
dave
Hi Scott
Robert and I have built a duel chamber test box or double bass reflex as he calls it to do some testing for a single A10 . I was wondering your thoughts on how this might perform compared to the double A7 . For now our test box is only ported in the secondary chamber and we haven’t cut out or installed any drivers yet.
Thanks Paul
Robert and I have built a duel chamber test box or double bass reflex as he calls it to do some testing for a single A10 . I was wondering your thoughts on how this might perform compared to the double A7 . For now our test box is only ported in the secondary chamber and we haven’t cut out or installed any drivers yet.
Thanks Paul
We are back to the drawing board actually. The HF gain of the A7's in this design make the monitor a rather unpredictable performer. With the right material it heavenly, mainly acoustic and voices, but step too far outside and it can become uncomfortably bright.
Phase 2 will employ a design more akin to a FAST build. I have an inkling we will wait to see what new drivers emerge from the MA camp.
Phase 2 will employ a design more akin to a FAST build. I have an inkling we will wait to see what new drivers emerge from the MA camp.
Hi Jimbro,
Good to see you at the forums after a while.
If you are running the Alp 7.3 with woofer assistance, probably there will not be much benefit going for a 2 x FR driver / cabinet... assuming the "heavy lifting" will be done by the woofers.
That being said if you are thinking about a 2.5 system - running the Alpair 7.3 in full range, second Alpair 7.3 as a bass-wide, and the woofer for LF assistance below a certain cut-off point - that should be possible. One "simple" idea that come to mind is get a powered sub, use the sub to set the XO with the FR boxes. Run both the sub and the FR box when you need deep bass, turn the sub off when you want to run wide band only.
Shorter cab with 2x Alpair 7.3 should be possible - just keep the volume for the cabinet sections and ports the same as in the original design. To run the lower Alpair 7.3 driver in 0.5 (basically a bass helper) you will need to use a cap. Dave might have some tips here.
Good to see you at the forums after a while.
If you are running the Alp 7.3 with woofer assistance, probably there will not be much benefit going for a 2 x FR driver / cabinet... assuming the "heavy lifting" will be done by the woofers.
That being said if you are thinking about a 2.5 system - running the Alpair 7.3 in full range, second Alpair 7.3 as a bass-wide, and the woofer for LF assistance below a certain cut-off point - that should be possible. One "simple" idea that come to mind is get a powered sub, use the sub to set the XO with the FR boxes. Run both the sub and the FR box when you need deep bass, turn the sub off when you want to run wide band only.
Shorter cab with 2x Alpair 7.3 should be possible - just keep the volume for the cabinet sections and ports the same as in the original design. To run the lower Alpair 7.3 driver in 0.5 (basically a bass helper) you will need to use a cap. Dave might have some tips here.
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