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La Scala Bass Bin questions?


PerchPerkins

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Greetings all! 

 

 

I am in the works of designing a W-bin subwoofer that utilizes a Transmission line enclosure instead of a typical 12 or 15" sealed woofer. It would utilize a 10" professional woofer with a Fs of around 55-70Hz which would give me a tuning frequency for the T-Line at the particular FS, allowing the speaker to output bass down to 45-55 Hz with very flat response and minimal excursion. 

 

Because the T-Line is smaller than the "dog house" that the La Scala's have, I have more room for more horn so Instead of just one big horn, I have one, much longer horn folded inside which has the same footprint as a La-Scala. 

 

 

my question is.....

How do the La Scalas output down to 50Hz? in order to do that with a horn, you need a 4.2 meter long horn and the La Scalas aren't even half that length.

how are they able to do it? does the 15" woofer output so much low end that it still overpowers the horn dampening them  below 50 Hz?

 

From my understanding the horn acts as a coupler between the air and the speaker, effectively matching the impedance of the air to the impedance of the light weight cone allowing for much better transfer of speaker movement to acoustic energy and the La Scala horn won't effectively couple the impedance of the two mediums below 50Hz which has a "dampening effect" dampening effect" which reduces the efficiency as the frequency gets lower and lower below 50 Hz. 

 

 

So how do they achieve this feat?

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Below about 100-125Hz, the LS acts more like a direct radiator. It still has a very low excursion, though. Yes, the low end  certainly rolls off, but the horn loaded bass is clean and articulate.

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On 10/2/2019 at 5:21 PM, PerchPerkins said:

Greetings all! 

 

 

I am in the works of designing a W-bin subwoofer that utilizes a Transmission line enclosure instead of a typical 12 or 15" sealed woofer. It would utilize a 10" professional woofer with a Fs of around 55-70Hz which would give me a tuning frequency for the T-Line at the particular FS, allowing the speaker to output bass down to 45-55 Hz with very flat response and minimal excursion. 

 

Because the T-Line is smaller than the "dog house" that the La Scala's have, I have more room for more horn so Instead of just one big horn, I have one, much longer horn folded inside which has the same footprint as a La-Scala. 

 

 

my question is.....

How do the La Scalas output down to 50Hz? in order to do that with a horn, you need a 4.2 meter long horn and the La Scalas aren't even half that length.

how are they able to do it? does the 15" woofer output so much low end that it still overpowers the horn dampening them  below 50 Hz?

 

From my understanding the horn acts as a coupler between the air and the speaker, effectively matching the impedance of the air to the impedance of the light weight cone allowing for much better transfer of speaker movement to acoustic energy and the La Scala horn won't effectively couple the impedance of the two mediums below 50Hz which has a "dampening effect" dampening effect" which reduces the efficiency as the frequency gets lower and lower below 50 Hz. 

 

 

So how do they achieve this feat?

 

This sounds all monked-up.  A pro 10" with an Fs of 55+ will not make a subwoofer.  Floor monitor, sure.  Don't transmission lines need a Qts around .25 and an Fs also around 25?  Not that far from a Klipsch K-33-E.  Why would you want to mix 2 such disparate designs?  If you want a high efficiency horn subwoofer, there are many available designs with proven performance.  If you want La Scalas, buyt some. 

 

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im not trying to make a subwoofer im trying to make a woofer that will play reasonably low. I don't need it down to 25Hz. 

 

My Hersey III's play down to 57 hz and they sound fantastic. a little more low end would be nice. 

 

Transmission lines are known for having a low flat frequency response, however "low" in the engineering aspect of this build is all relative. 

 

since I want to make a horn loaded woofer, the horn will limit the low end end output, so its almost WORTHLESS to use a driver with an Fs of <45 Hz (transmission line boosts the output above and below this frequency) since the horn won't so anything to frequencies this low. 

 

So I want to use a 10" pro driver with a fs of around 55-70 Hz, giving me a boost above and below those frequencies, and the boost that it gives should be within the limits of the horn, allowing the horn to then improve the efficiency of the system. 

 

I say "low" is relative because from an engineering standpoint the "low" is achieved by the coupling that the transmission line does around the Fs, extending the low end. whether my Fs is 70Hz, or 32Hz, the transmission line will allow each driver to perform "lower" and flatter than it otherwise would be able to.

 

My goal is maximum efficiency. I want to squeeze the most out of every watt possible. Transmission liens have fantastic bass, and so to La Scalas, so. figure I may be able to combine the two principles. 

 

Problem is, I don't know how the La Scala would work with a transmission line instead of a sealed enclosure. 

 

I am planning on doing a W-bin subwoofer enclosure, since the T-line is smaller than the La Scalas sealed cabinet, giving me much more space. 

 

 

 

 

TLDR: If I get a low Fs subwoofer, the really low end will be wasted because the horn won't do anything. Usually subwoofers with Low Fs's that are 8-10" are not super efficient, around the 87-89 Db Range. Thats why a pro driver fits the bill. they are more efficient by design, and I can boost the low end via a transmission line to get some flat transient bass, while maintaining  the efficiency of around 94-96 Db.

 

THEN you couple it with the horn for more efficiency.

 

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On 10/2/2019 at 9:48 PM, Marvel said:

Below about 100-125Hz, the LS acts more like a direct radiator. It still has a very low excursion, though. Yes, the low end  certainly rolls off, but the horn loaded bass is clean and articulate.

 

Horn bass IS clean and articulate, and Transmission line bass is low(er) and flat(er) than you can get with a typical ported or sealed. People describe the bass as "thunderous" (assuming you have a driver with a very low Fs) this is the case. Since I will be using one with a higher Fs, that "thunderous-ness" aspect will simply mean the 45-100Hz region MIGHT be more fast and transient, qualities that I love. Combine that with the clean articulate aspect of horns, and I think you have a pretty nice combo. 

 

Problem is I don't know how these two interact. 

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13 hours ago, JohnA said:

 

This sounds all monked-up.  A pro 10" with an Fs of 55+ will not make a subwoofer.  Floor monitor, sure.  Don't transmission lines need a Qts around .25 and an Fs also around 25?  Not that far from a Klipsch K-33-E.  Why would you want to mix 2 such disparate designs?  If you want a high efficiency horn subwoofer, there are many available designs with proven performance.  If you want La Scalas, but some. 

 

also, higher Qts drivers can be used, but it is VERY important to model them in a program first. They often have smoothness issues as low as 90 Hz, and suffer from massive peaks and dips after that. This can be remedied by placing the driver "down the line", and by reducing the cross sectional area of the line, however you don't want to reduce the cross sectional area of the line by more than 1/3 of the Sd of the driver, as this reduces efficiency at higher outputs.

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On 10/2/2019 at 4:21 PM, PerchPerkins said:

I am in the works of designing a W-bin subwoofer that utilizes a Transmission line enclosure instead of a typical 12 or 15" sealed woofer. It would utilize a 10" professional woofer with a Fs of around 55-70Hz which would give me a tuning frequency for the T-Line at the particular FS, allowing the speaker to output bass down to 45-55 Hz with very flat response and minimal excursion. 

 

 

You might want to look into tapped horns. They have elements of TL and horns, and are compact relative to exponential horns of the same low frequency cutoff. 

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