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High Efficiency Speaker Asylum Need speakers that can rock with just one watt? You found da place. |
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High Efficiency Speaker Asylum Need speakers that can rock with just one watt? You found da place. |
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In Reply to: Re: Pi Speakers posted by Hermit on January 21, 2001 at 05:10:34:
Hi John!You wrote:
>> I would appreciate any further info via email
>> particularly relating to units that will match
>> the 110dB/1W of my 100Hz horns using Eminence
>> Delta/Gamma/Omega drivers which I can easily obtain.I can get you plenty of great designs for the Eminence Delta's and Omega's, but I can't get you to 110dB.
If I were to make a basshorn design that provided this kind of gain, it would be excessively "peaky" in the midbass. See the chart above.
All of my horns have a 7dB peak at cutoff - in fact, all conical basshorns do. After that, there's a couple of octaves of 3-5dB gain. So a person could get 110dB using a 103dB motor - but only at the octave surrounding horn cutoff. It would have to be done by designing for maximum horn gain to coincide with a region of maximum motor output.
I do it another way. Horn cutoff is placed in the woofer rolloff region. This emphasises bass where it needs the help. Then the couple of octaves of "non-peaky" gain assist the woofer in its normal bandpass. In this region, the horn's participation is much more linear.
This design is also improved by using woofers that have gradually rising slope of output (about 3dB) in their fourth octave up to motor cutoff. As you've probably noticed, many woofers do have this trait - certainly the ones most commonly used by horn builders.
After all, even multiply-folded horns like the Klipschorn and other "W" shaped designs are also conical horns. They are sectioned conical horns - the Klipschorn having 3 sections - and this makes their characteristic curve somewhat of a cross between a conical and an expotential, provided that the difference between section rates approximates an expotential expansion.
Such horns often have a slightly smaller peak at cutoff, but they also often have more of a secondary peak, and usually have a third as well. The secondary peak on a single section horn such as the Pi horn is less than 2dB, and is not offensive, as it sometimes is on other horns.
The fact is that no basshorn will provide significant gain for more than 3 octaves. You just gotta pick where you want your gain.
What you can expect from a loudspeaker you might build using my designs is that performance is great as long as you do two things:
1. Make certain the horn is big enough to provide cutoff in the motor rolloff region. That usually happens "automatically" as a virtue of the ratios involved in the design - larger motor chambers (determined by Vas * Qts) get larger horn dimensions because they are geometrically connected as a unit.
2. Make certain that woofer/horn efficiency is matched by tweeter horn efficiency. If you use one of the Eminence motors that provides 102dB@1W/1M, then you can expect system sensitivity to be about 105dB. That matches well with a 105dB HF horn. But if you're running a 110dB horn, it should be attenuated in this design.
Honestly, I've never liked the idea of running basshorns that put horn cutoff well above motor cutoff. I know that space restraints often dictate this, but I consider these kinds of space restraints to necessitate removal of the horn from a design. If the size must be too small for an adequate horn - don't put it on at all.
Smaller horns will increase efficiency of the system in their passband. But we've all heard basshorns that were too small and the result was a terrible, peaky midbass. So I avoid this practice entirely.
In my earlier post, I "blew" the link to the "PiAlign" program, but I did it right this time. Just click on it and you will get the program and "whitepaper" that will show you the layout of these simple designs.
You can run the program using the motor of your choice, and it will show you the dimensions of the box required. Eminence Delta's and Omega's are already included - the Gamma's aren't. I'm sure they are great drivers, but I've never used them.
And finally, I'd recommend the Eminence "1K6" crossovers with any of the Eminence woofers and the Eminence MD2001 HF unit on the H290 horn. Definantly put the HF compensation resistor/capacitor in series with the 1K6 crossover's tweeter output.
There are something like 10 designs for the Delta's and Omega's - when you consider that each is offered in bass reflex, cornerhorn and free-standing horn. If you want more information about a design for a specific woofer - write to me and I'll E-Mail it to you.
And again - Sorry that these don't use metric measurements. But at least they're "horny." [grin]
Wayne
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Follow Ups
- Eminence Horn Plans - Wayne_Parham 13:36:06 01/21/01 (0)
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