Lascala Bass Bin Mod

[Marvel]

Looks a lot bigger seeing all the pics. Beautiful room. Is that a Taylor and a Les Paul hanging on the wall at the far end from the speakers?

I would think some dacron or polyester fill would work well. According to Dennis, they should have something in them.

Did you notice that Frode mentioned the bass was better with a slightly shorter port length? Do you have an spl meter you can use to make some reading with?

Marvel

ps My wife puts up with a lot from me too. I have had all kinds of friends in the haouse to record them and she has been very gracious over the years. I've never had the money to put up a seperate studio.

[homemade]

With 12 db of boost at 30hz one would probably never see the amp overpowering the woofer at this frequency. I've run mine for 15yrs this way without the amp ever going into overload and experiencing the woofer bottoming out. I used to use a 200watt/channel amp and now run a 60watt/channel surround reciever. Most of the energy of music is probably in the 100hz range. Does anyone know of a recording that pumps out max. volume at 30hz?

Also someone was saying that the mod made them as efficient at 35hz as at 100hz. This can't be without using the port as a passband type of hyper one note bass. The lower octave in this mod will only be as efficient as the K33 woofer used as a direct radiator. The specs shown on one example of this mod was taking some room effects into account. Would I do this mod. I sure would if I had some homemade LS's. The gain of 5db or so at 30hz is probably worth it but one will still need to boost the lower octave via an eq. to get a flat low end response and to tame the upper bass range unless one likes the tympany drum to vibrate the couch.

[rtaylor]

Hey Marvel, no that is a Taylor and a Yamaha(les paul),lol. Purchased from a friend who dabbles in guitar sales. I can't find any information at all about this guitar,it's like Yamaha never made it. SL-700S Studio Lord. I believe Gibson sued them over this. Mid 70's japaneze made.Push pull tone controls for single coil activation.

We have jam sessions here about every month or so. She hasn't left me yet. Listening to music after is usually louder than us playing. No, it is always louder.

[djk]

"The gain of 5db or so at 30hz is probably worth it but one will still need to boost the lower octave via an eq. to get a flat low end response and to tame the upper bass range unless one likes the tympany drum to vibrate the couch."

If you had a real drum in the house, would it shake the couch?

The vented mod for best results should be used with a high pass filter with a Q=2 at 31hz for a K33 (7" ports), or 28hz for a K43 (10" ports). This filter makes it flat to a -3dB at 31hz with the K33 and also adds about 2dB in the 50hz region.

The EV Inteface A filter is a good one for the K33, The EV sentry III/Inteface D is a good one for the K43. These show up on eBay for little of nothing from time to time. Change two resistors per channel to change frequency.

[NOSValves]

djk,

More information on this High Pass filter please. What would be required to build it ? How would it install in conjuction with a Type A network?

Craig

[homemade]

I can understand the reasoning behind getting an EV eq for extended bass response but I fail to see where the -3db freq. of 31hz or lower will really be -3db. Yes, in a direct radiator app. that would be the f3 freq. but we are dealing with a horn loaded upper bass that is going to add 10db to the efficiency of that region. Am I not wrong in this assessment? Doesn't the Altec A7 have this same problem? You are still going to have to boost the lower octave via an eq. and not just use the eq. an EV Sentry speaker has. My biggest complaint about the khorn and I assume the LS (haven't really listened to one recently in any home) is that the upper bass is way over accenuated compared to the lower octaves and the octaves above 300 hz or so. This leads to a resonant quality that is not natural. That's why I was talking about the tympani being over actunated. I did recently record a high school band and noticed the overemphazed tympani drum even when reducing the 100-200hz range about 4 db.

Yes, a tympani drum in my room would shake the couch but sitting back about 50 ft from the drum should tame things somewhat. How do you guys who are very picky about your sound deal with the overboosted upper bass without an eq.? Perhaps this phenomina isn't as apparent with symphony music as it is with some voice recordings and even pop music with overemphasized male voices.

[djk]

" Am I not wrong in this assessment?"

If you could add, you would see that that (ignoring the room dip at 40hz) the overall response of the LaScala with the K33+EV Interface A filter+7" Ports as constructed by Frode is ±3dB from 31hz~200hz.

[maxg]

Somewhere in this fascinating thread (truely) I missed the benefit of porting the extension. Inceasing the volume whilst keeping it sealed brings (apparently) a 4.5 dB boost at 30 Hz. This is the point I would be tempted to go - the porting worries me as I am sure we will have some kind of phase issues going on here.

Also - what are the dimensions of the add-on box and how are they chosen? what, for example, would happen if you merely made a larger enclosure and kept it sealed rather than keeping this size and porting?

Final question: Any indication of a change in sensitivity with this mod?

[Marvel]

Max,

You will notice that the cabinets that Frode made (with the Oris horn on top) were made new. I hadn't really noticed that about NO ports in the listing. When I read that before I thought he meant there were ports but no port tubes of any length.

If I were home, I would post the links to all the pics of these mods.

1. Add the box underneath (for some the added benefit of raising the cabinet to have the mid and tweeter more at ear level)

2. Build the whole thing from scratch (same outcome as 1.)

3. Enclose the top of the LS back and open the doghouse into that area. Still looks stock from the front, but you gain the benefit of the porting (which must then be ported out the back)

Marvel

[homemade]

DJK, Looking at the freq. response posted I see a 10db disparity between 125hz and 31 hz and more at 40hz. How much eq. does the EV eq. give anyway? You mention 2db at 50hz but what about 31 hz? I would venture to say that the dip at 40hz isn't a room "suckout" but the natural response of the speaker and the gain at 31hz is the room interactions. Look at the stock specs-it's about what the response of the LS is that Klipsch has in their literature. Yes, one is gaining some lower octave boost in the 5db range or so but it's not enough to keep up with the horn loaded upper bass. I still say a 10-15 band eq. is better than the EV eq. in that the upper bass can be tamed. Using a 15 band eq. is a lot simpler than modifing the speaker? Freq. response would be on the order of the khorn with perhaps 5db less output in the 40hz-60 range and the same response in the 30 hz range.

[DrWho]

Using EQ to boost the response by 12dB results in 4 times the excursion and 16 times the power to maintain the same SPL. With the lascala, as long as you're not listening above 109dB then this isn't an issue. However, the main benefit to using a horn is that it reduces cone excursion. Implementing an EQ to the system will exhibit 4 times the modulation distortion.

Modifying the design of the speaker with the port shouldn't change the excursion much at all or even the tension properties required for the horn throat (the springiness behind the driver is essential to HF reproduction). So in essence, the port seems like a free way to extend the frequency response of the driver. Then if EQ is indeed needed to maintain a flat frequency response, then the negative effects of EQ should be far less.

I have read that only 'improperly' tuned ports and bandpass systems result in one-note bass. It is entirely possible to 'properly' create such a system that does not. Check out some of the older Tannoy Studio subwoofers that use a 6th order bandpass design. They are far from one-notey (and you wouldn't expect something of studio quality to be that way either).

Btw, shouldn't the -6dB point of the lascala be around 45Hz (assuming a 24db/octave roll off from the horn)? Wouldn't that imply that a port tuned to 45Hz would extend the -3dB point to about 40Hz and maintain the 104dB sensitivity? I guess I'm not understanding how the response is extended an entire octave down below 30Hz (I can see the -10dB point being closer to 35Hz). Does adding the port at all change the LF characterstics of the horn loaded section itself?

[Marvel]

----------------

On 3/21/2005 6:04:00 PM DrWho wrote:

Using EQ to boost the response by 12dB results in 4 times the excursion and 16 times the power to maintain the same SPL. With the lascala, as long as you're not listening above 109dB then this isn't an issue. However, the main benefit to using a horn is that it reduces cone excursion. Implementing an EQ to the system will exhibit 4 times the modulation distortion.

Modifying the design of the speaker with the port shouldn't change the excursion much at all or even the tension properties required for the horn throat (the springiness behind the driver is essential to HF reproduction). So in essence, the port seems like a free way to extend the frequency response of the driver. Then if EQ is indeed needed to maintain a flat frequency response, then the negative effects of EQ should be far less.

----------------

I copied this from dennis' text on the first page:

"But by adding a simple two pole high pass filter ahead of the power amp we can now have a C6 with a -3dB point of 31hz. Since this is the Fb of the system there is no increase in cone excursion or distortion. The filter consists of a cap an inductor and a pot. The pot allows adjustment at Fb of +/- 3dB. This is similar to being able to change the Qtc of a sealed box from .5~1.0."

You are right that it would mean little or no more cone excursion. (btw, I also added spaces back into the first quote of DJL's, so it is way easier to follow)

I want to hear more of Randy's thoughts after listening some more. And if he got some other good stuffing in those boxes.

Marvel

[djk]

200 160 125 100 80 63 50 40 31 25 20 HZ

_76 79 78 76 75 80 71 60 68 54 53 Ports cut to 7"

"DJK, Looking at the freq. response posted I see a 10db disparity between 125hz and 31 hz and more at 40hz. How much eq. does the EV eq. give anyway?"

Obviously you have no idea what "Q' means, its a relative measurement.

(log^base10)X20=dB

Q=2=6dB

Q=1=0dB

Q=.707=-3dB (you should have known this one, Butterworth)

Q=0.5=-6dB (you should have known this one, LR)

"I would venture to say that the dip at 40hz isn't a room "suckout" but the natural response of the speaker and the gain at 31hz is the room interactions."

The 11dB dip (WRT 50hz) at 40hz is a phase cancellation.

" Look at the stock specs-it's about what the response of the LS is that Klipsch has in their literature"

Look at the real data

http://forums.klipsch.com/idealbb/files/AES%20Preprint%20re%20LaScala.pdf

Hmmm, 8dB down at 60hz wrt 200hz, 16dB down at 45hz wrt 200hz

"I still say a 10-15 band eq. is better than the EV eq. in that the upper bass can be tamed"

It doesn't need to be, its within ±3dB to 200hz in room with the EV, besides most 10-15 band eqs are a huge POS.

"Modifying the design of the speaker with the port shouldn't change the excursion much at all "

It only cuts cone excursion in half at Fb, while adding 3dB more output. For a given excursion near Fb that is 9dB better than a sealed box.

"I have read that only 'improperly' tuned ports and bandpass systems result in one-note bass. It is entirely possible to 'properly' create such a system that does not."

True, listen to the B&W 800 series. 6th order tuning is about a 1/2oct below standard tuning, there is not much danger of it becoming high Q and ringing (sounding boomy).

"Somewhere in this fascinating thread (truely) I missed the benefit of porting the extension."

Try 9dB more output at 31hz, some from the port, and some from the Q=2 filter.

"Inceasing the volume whilst keeping it sealed brings (apparently) a 4.5 dB boost at 30 Hz. This is the point I would be tempted to go - the porting worries me as I am sure we will have some kind of phase issues going on here."

"If we close in the back of the high frequency cabinet and open the woofer rear chamber up into this volume and fill with fiberglass we now have Qtc=.577, Fc=58.2hz, F3=73.6hz. Bessel=Qtc.577=D2 gives the best transient response and the least group delay of all the sealed boxes. At 30hz the Qtc=.577 has 4.5dB more output than the Qtc=.85. Compared with sealed enclosures,the transient performance of the best vented enclosure is worse than the best sealed box enclosure. Since we have made great gains in performance some may elect to stop here."

"Also - what are the dimensions of the add-on box and how are they chosen?"

The add-on box was sized to be about the same net volume at the top of the LaScala. It was intended to be a try-it-before-you-buy-it kind of deal. If you didn't like it, you threw it away. If you liked it you added one board to the back of your home LaScalas (the pro version already has a board there, and works better for this mod because of the K43E woofer).

"what, for example, would happen if you merely made a larger enclosure and kept it sealed rather than keeping this size and porting?"

The size used for the mod gives the best response possible from a sealed box.

"Final question: Any indication of a change in sensitivity with this mod?"

None above 100hz or so.

[maxg]

djk,

Thanks - helps when you understand the science behind it - which I dont and you apparently do.

I am yet to find a LaScala setup in Greece that plays well and bypassed the speaker as a result - this mod might just save the day. I might just build a pair of these boxes for the guy that lives up the road and see what difference it makes - worst case scenario is that I will end up throwing out $30 of wood. Best case - I found my speaker.

Talking to various owners and previous owners the general line of thinking is that the standard horn loaded bass bin does not do well on marble floors - combined with the lower than ideal placing of the centre and mid driver. I am wondering if the raising of the unit (initially on a sealed enclosure) wouldnt solve both problems.

I think I will try the port later - although I will have to figrue out a way to re-seal the ports if that re-creates the woofer/floor interaction problem.

Food for thought....

[rtaylor]

Sorry I haven't said anymore about the mod but I haven't had a chance to (haven't got off my butt) buy any stuffing yet. As is I haven't noticed any loss in attack or loudness. An increase in some very low end is noticed. As stated before the speakers sounded a tad more forward at first but now I'm not so sure I heard it. Promise to get some stuffin' and try shortening the tube to 7 inches. Don't have an instument to measure differences. Randy

[Frode]

Just to clear up some things. I never posted any numbers on the performance of the modified bin. This was done by some other Oris owners who used the K33E and no EQ. I used the JBL 2226H and 7dB EQ at 32Hz.I also tried shorter ports/no EQ, but in my opinion the long port/EQ sounded best.

Frode

[homemade]

DJK, What do you mean a 10band eq. is a pos compared to the ev eq? Now, all of your Q specs can be thrown out the windowbecause we really don't know how the woofer will react in a horn loaded enclosure with a constricted throat size, etc. I think we are on experimental terms here and not so mathimatical explanations that you are giving us. I don't see how this is a simple (not really simple) ported box. To achieve flat response an eq. of some sorts is going to be needed regardless of whether it's sealed, ported, enlarged, whatever. Can we gain some bass by enlarging and porting-sure. How did you know the 40hz response is due to phase cancellation? I'd like to see more actual freq. response measurements from the modified vs unmodified.

[djk]

"Just to clear up some things. I never posted any numbers on the performance of the modified bin. This was done by some other Oris owners who used the K33E and no EQ. I used the JBL 2226H and 7dB EQ at 32Hz.I also tried shorter ports/no EQ, but in my opinion the long port/EQ sounded best.

Frode"

I'm not sure where the photo and chart came from.

Bill Morrison in Dallas likes his with 7", anymore I kinda tune them around the room modes for smoothest response.

If you start out long, you can always make them shorter

"What do you mean a 10band eq. is a pos compared to the ev eq?"

Does it say 'White' on the front panel, and have rotary controls?

If not, there is a 99.999% chance that it is a POS.

"Now, all of your Q specs can be thrown out the windowbecause we really don't know how the woofer will react in a horn loaded enclosure with a constricted throat size, etc. I think we are on experimental terms here and not so mathimatical explanations that you are giving us. I don't see how this is a simple (not really simple) ported box."

Gee, you're so smart, why ain't you rich?

The port is tuned two octaves below Fc of the horn, the horn has no effect to speak of.

"To achieve flat response an eq. of some sorts is going to be needed regardless of whether it's sealed, ported, enlarged, whatever."

And he doesn't get it even after I explained filter 'Q' in a previous post.

Some people don't get it no matter how many times you show it to them. If you get it it seems simple, if not...

Try Don Lancaster's Filter Cookbook, it is still in print.

"How did you know the 40hz response is due to phase cancellation?"

Common sense: phase cancellations can be infinite, peaks are finite.

"I'd like to see more actual freq. response measurements from the modified vs unmodified."

Buy some test equipment and go for it!

[Marvel]

My apologies to Frode --

I had saved the photo and the text/chart from previous posts on this topic. My memory was faulty when I posted the two together. I admit I was lazy and didn't look them up again.

DJK,

Do you have the schematic for the EV filter? I, for one, would appreciate it.

Marvel

[homemade]

Quote: Gee, you're so smart, why ain't you rich?

Me: What an attitude!!!!!

Quote: And he doesn't get it even after I explained filter 'Q' in a previous post.Some people don't get it no matter how many times you show it to them. If you get it it seems simple, if not

Me: You don't get it!!! I'm saying you can't get flat response by running a ported enclosure for the bottome octave and a horn for the rest of the spectrum!

You're talking a running a Q factor that would boost the bass. I would have to go back and see if you're talking about using an eq. with a high Q factor or tuning the box to a high Q factor. If you're tuning the box to achieve a high Q factor-good luck with having smooth bass. Maybe you can.

Talking about the 40hz response:

Quote: Common sense: phase cancellations can be infinite, peaks are finite.

Me: Where is the infinite phase cancellation? Just because a modified speaker has 0db change at a certain freq. doesn't mean it's automatically a phase cancellation problem. Wasn't one of the response measurements with a larger sealed box without ports?

Quote: The port is tuned two octaves below Fc of the horn, the horn has no effect to speak of

Me: Are you saying the constricted throat has absolutely no bearing on how the woofer behaves at lower frequencies? Do you have data to back this up? I still don't understand your reference to white and rotary knobs and POS. Maybe your attitude is POS!