Scala bass bin with curved sides

[Arash]

I'll build a bass bin like LS but with curved side walls, maybe something similar to Volti Audio Vittora. I'm gonna use Baltic birch and I'll bend it using vacuum bag or I can use CNC slices. I know I can just draw something and build it and measure the sound so see what happens but I thought maybe someone can help here. any opinion?

[garyrc]

I'll build a bass bin like LS but with curved side walls, maybe something similar to Volti Audio Vittora. I'm gonna use Baltic birch and I'll bend it using vacuum bag or I can use CNC slices. I know I can just draw something and build it and measure the sound so see what happens but I thought maybe someone can help here. any opinion?

Side walls curved on the inside toward the sound path, or curved on the outside, toward the room? If on the inside, you would need some acoustical/engineering design data first, wouldn't you? Are there plans or detailed measurements for the Volti online?

The characteristics of the eminence woofer (the one in the stock LS) might be important. Good Luck.

[Arash]

I'll build a bass bin like LS but with curved side walls, maybe something similar to Volti Audio Vittora. I'm gonna use Baltic birch and I'll bend it using vacuum bag or I can use CNC slices. I know I can just draw something and build it and measure the sound so see what happens but I thought maybe someone can help here. any opinion?

Side walls curved on the inside toward the sound path, or curved on the outside, toward the room? If on the inside, you would need some acoustical/engineering design data first, wouldn't you? Are there plans or detailed measurements for the Volti online?

The characteristics of the eminence woofer (the one in the stock LS) might be important. Good Luck.

for sure it should be redesigned. I've access to Beyma and BMS and Faital Pro and B&C drivers for -70% off the original prices as well I may consider using. Faital Pro and B&C don't seems to come very handy but some of BMS and Beyma woofers are among the best. 15LX60V2 from Beyma is what I'd like to use. the mechanical/electrical features of the woofer should be taken into consideration for tuning in the dog house. about the horn path, is there is software for simulation such a horn?

Edited July 9, 2014 by Arash

[Arash]

this is the first try. when you try to make a La Scala cabinet with curved sides, the first thing you'll notice is that you should widen the cabinet otherwise you can't simply bend the sides in a way they won't touch the dog house which makes the whole horn a dead-ended valley! so I kept dog house intact and widen the cabinet. lets take a look at this:

Edit: I noticed what you see above has relatively the same footprint as a Khorn has.

Edited July 9, 2014 by Arash

[Schu]

you didnt take into account wall thickness.

[Arash]

you didnt take into account wall thickness.

yeah yeah I know. it's a simple Corel drawing not the final plan! I think I'll use 1" of baltic birch plywood. I drew it to see how it looks like at embryo stage.

[Arash]

I tried to add wall thickness and noticed that the dog house will be critically close to side wall. I thought why not change the dog house and make a little waveguide for woofer exit. it seems to be better IMO. at the left plan you see rounded sides with convectional dog house and at the right plan you see rounded sides among modified dog house.

Edited July 9, 2014 by Arash

[ClaudeJ1]

Build Quarter Pies and get real bass.

[Marvel]

The back part should have expansion already (vertically as it splits left and right)... don't forget how the LS looks inside, or even the Peavey FH1 (I have drawings of those at home).

LaScala11.pdf

[cradeldorf]

Not sure what you plan to gain, but if curiosity is the power behind this Feel free to learn. Knowledge is there for the taking.

[mungkiman]

Don't you want to increase the flare rate?

[Arash]

Don't you want to increase the flare rate?

AFAIK LaScala had a flare rate of 100Hz or so? I never simulated a folded or conical horn in Hornresp. maybe someone will give me some info about it

[mungkiman]

My understanding is that a larger flare rate (horn "mouth") produces lower notes. One of my questions about Klipschorns is whether it could be improved upon by utilizing full height exit horns. Especially since a 400/401 lens affords plenty of room...

[ClaudeJ1]

For fully horn loaded bass down to cutoff frequency, it is the 1/4 wave LENGTH of the horn that matters. The rest is just words on paper.

How short your bass horn is depends on the Subwwofer you will use with it.

Edited July 10, 2014 by ClaudeJ1

[Arash]

still tweaking

[Marvel]

Here's a couple drawings. I got from a French site about the Peavey FH-1 and text about the FH-1 history:

From Marty McCann on message board http://www.livesoundint.com/lab/lab/archive3/55814.html

: Thanks to An Other Dave, for providing the link to that original thread. I must have been on the road back when they were posted. I was going to answer today's posting anyway, but now I'll try to provide a little more background.

: The FH-1 Enclosure was was first manufactured as the low frequency section of the original SP-1 made in 1976, about a year later Peavey began running the FH-1 as a seperate component along with the MF-1X high frequency horn. So the FH-1 existed from about 1977 until 1999 So it makes it one of the longest products in Peavey's catalog. The FH-1 even existed before the Black Widow loudspeaker. The SP-2 in all of its incarnations (Sp-2, SP-2A, SP-Ti, SP-2XT, and SP-2G)was first manufactured in 1978, so it is now the winner of the longevity product award.

: The first FH-1 had an Eminence 15" speaker rated at 150 Watts at the time. It appeared this box began to eat the spkrs at about 160 Watts, mainly due to the fact that the operators of these systems were ingnorant of the cut-off frequency spec of the box (60Hz). Yes, even for a horn loaded box it was small, 30 5/8" W x 25 3/8" H x 23 3/4"D (77.8cm x 64.5 cm x 57.8cm), the cut off frequency at the - 3dB down point was 58 Hz (the -10 dB point 45 Hz).

: In 1978 the first Black Widow loudspeakers were introduced and a model was designed for the FH-1. These were rated at 250 Watts of continuous power within the published bandwidth of 60 Hz to 600 Hz. In this case it was a bit of reverse engineering, because the box design already existed and Peavey wanted an alternative loudspeaker for the FH-1. The last FH-1's in the series had 350 Watt rated Black Widows in them, and were rated at 127 db of maximum SPL with a 104 dB (1W @ 1M) sensitivity.

: Between the introduction of the FH-1 and the introduction of the Black Widow, the FH-2 enclosure was also introduced, and it likewise initially had the 150 Watt vendor provided 15" loudspeaker.

: When the Black Widow loudspeaker was put in the FH-1 it became apparent that the more efficient loudspeaker caused the box to flex more than the previous speaker, so the brace or shelf was added across the center of the mouth. It made the box much less whuompier with this bracing.

: It was about the time of The Urban Cowboy when the FH-1 was used in an installation in Mickey Gilley's night club in Pasadena Texas. There were ten of them (and ten MF-1-X horns) placed around the dance floor facing-in towards the dance floor. This is the way the clubs house engineer specified the system. It didn't do much for the live music but when they danced the two step around that dance floor it was evenly covered. Later on they added subsequent speakers to actually cover the rest of the building.

: Now on the impedance thing it was a four ohm 15" loudspeaker that was actually "slot" loaded into the horn. The speaker was in a sealed triangular box. The baffle board that coupled the output of the speaker to the horn itself had a vertical slot in it that was about 3.5" wide and maybe 13" high. It also had a channel routed about 1/4" wide that was routed into the baffle to a depth of about 3/8." This was to allow for a little more excursion and helped prevent the surround from the banging into the baffle board. Opposite the slot in the baffle was a wedge center mounted against the back of the of the enclousre to allow the sound to defract to the left and right of this wedge, and in each corner there was a piece of plywood diagonally mounted top to bottom to creat a reflector in the left and right rear corners of the box. The distance from the baffle to the rear wall was less than maybe 4". This arrangement of playing through the restricted slot, wedge, waveguide, wedge, and subquent horn, resulted in a measured impedance higher than 4 ohms, and nominally 8 ohms from 60 Hz to 600 Hz. Again only when used in this bandwidth. When the uninformed would push the 31.5 Hz slider through the roof, the impedance would revert to 4 ohms, the transducer would be come un loaded and whoumpie was a euphemism, fart is more dead on because the speaker would bang against it's baffle on forward motion and the voice coil would strike the back plate on rear excursions.

: Now I read the threads where someone placed a Kilomax speaker in this enclosure, and was very happy with the results. He even stated that he did an impedance curve and it held a nominal 8 ohms all the way down to 40 Hz. I doubt however that a single enclosure would perform satisfactorly down to 40 Hz at full power. It may indeed have measured down to 40 Hz with six dB of headroom (85 Watts)as it would have had 1/4 fourth the excursion, but since it was below the frequency where the horn loaded the transducer, it probably produced harmonic distortion as well.

: Now if you did stack up multiples of them in the right manner, the coupling of the mouths did somewhat lower the usuable lower frequency. I will always remember the first time I tried Ansley Dunsbar's (Journey's drummer) kick drum monitor rig. He had twelve of the FH-1 enclosures, each being driven by a CS-800 in bridge mode. I just had to sit on his drum stool and try it for myself. Well let me tell you, if I would have been wearing a cowboy hat, it would have knocked it into the next county with it's 10,000 watts (840 W x 12 = 10,080 Watts)for ONLY the kick drum.

: Now here are some in services for working with that enclosure. Since the internal chamber is sealed, after replaceing the speaker a couple of times the gasket can fail to seal the box properly, which will affect the loading as covered above. In fact a small leak in the seal can put quite a notche in the response above 100 Hz. I have used silicon window or roofing caulk to replace the gasket when it has failed to seat properly.

: The recommended speaker from Peavey is the 1504-4DT BW. Since this enclosure is no longer available neither is this model of loudspeaker. We do offer a 1504-4DT RB, replacement basket for a MSRP of 85.99, and you can purchase a replacement Black Widow Super Structure Magnet Asslembly for a MSRP of $89.99.

: As many people have stated, this box would kick serious butt in a large room or outdoors, when operated within it's designed bandwidth (60 Hz - 600 Hz). It could however be a dissapointment in the hands of someone who doesn't believe in reading the spec sheet. The most of them that I had ever used personnally was 24 per side at an early Mississippi Delta Blues Festival (circa 1980).\

: I hope someone learns from this otherwise I could have worked at something else for the last twenty minutes.

: One more story, I had a couple of these enclosures that had been stored in an outbuilding for more than a few years. One summer (when I was single), I invited some people over one Sunday to play volleyball. I took the FH-1's and MF-1X's out of the outbuilding to play some Vollyball Rock & Roll through them. I went down to the house some 120 Ft away to turn on the music, and when I came out of the house, most of the girls and one guy were standing on the bumpers, hoods, and trunks of the cars. Some critters had built a nest in the enclosures, and when that first Buddy Guy guitar lick roared out of the folded horn, about a dozen teenage sized Rats exited in a hurry.

: Har Har, one of the ladies actually pissed herself with fright.

: mfm

: The jist of all of this I guess would be to state that a direct radiator is still the preferred choice for Near Field (up close) listening. But the folded horn will always retain it's punch at a great distance. Remember however, as has been addressed in other threads, it is not a good idea to mix these enclosures in the same bandpass.

[Arash]

can anyone help me test the following horn in Hornresp? I think this would perform much better than a stock LS.

sorry I'm not good in 3D modeling and my designer is on vacation. I think some kind of waveguide at dog house exit will decrease sound erosion:

[drboar]

Calculate

1.the chamber volume

2. Horn lengh

3. Mouth area

4. Throat area

Play around in horn response and you will discover that flare does little to change the bass. Parabolic section, conical, exponential or hyperbolic change some few dB and the roundness of the high pass knee. The chamber volume changes that roundness to. The low pass frequency is determined mainly by lenght of the horn and the unevenness/"peakyness" of the response is set by mouth area and radiation angle. Curvature and implementations of slots and bends will affect the real life low pass response but will do little in the bass response.

[seti]

Go bigger 8-)

[moray james]

the FH1 shown above in yellow is really your very best option. It is better than a Belle. If you want better than that you must go to a straight horn not a folded one. Best regards Moray James.

PS: take a look at some of John Inlow's designs http://www.inlowsound.com/