speakerlab

[DrewBolce]

Since this thread never seems to die, I will chime back in. I have experimented with rear chamber stuffing. What I settled on was plastic window screening stapled over the back of the woofers with as little as possible, highly fluffed Dacron pillow stuffing in the rear chamber. I cannot emphasize enough to use the least amount of stuffing possible. Over stuffing will kill the lower bass.

Now for some complete heresy. The biggest effect I got was when I rounded off the sharp comer on the motorboard throat slot outside edge with a router rounding bit. This removed the "diffraction edge" like a modern bass port. The effect was to smooth the bass response noticeably. This may help with the "wood" sound several posters have complained about. I believe the Speakerlab plans called for a motorboard while the Klipsch mounts directly to the cabinet, so this may not be doable on most true Khorns. I should add that my cabinet has a 6' x 13" slot in the cabinet since I experimented with the larger throat slot in the early days. My findings where that the 3" x 13" slot worked the best with the Speakerlab woofer.

I use the ALK universal crossover with a 1mh coil for the Speakerlab 8 ohm woofer.

[ka7niq]

As long as there are SpeakerLab owners, this thread will continue I guess.

My limited experience with stuffing is this, it seems to needs some.

I removed all my stuffing, and real low bass went bye bye.

Such a PTA to remove and re install the access door though.

Still want to find a happy meduim.

[ka7niq]

Did your Speakerlab folded horn plans call for any stuffing in the rear woofer chamber, or did you use any ?

Yes the plans called for 18sq ft of 1" thick damping material, but after read some posts about stuffing I decided not to use any.

Might want to experiment some day ?

[ZAKO]

Ka7nig.....Real low bass....??? What do you mean by that discription???? You cant get some thing for nothing... Do you mean another octive?? or just a small boost in the same octive response??? or change in tonality of same frequency??? I can get that just changing damping factor of amp... Other than by ear ,did you verify with measurements??????? And if by measurments what instruments did you use.... What type of room did you use?? Do you have a full anechoic chamber??? Half chamber ??? Live end dead end room?? What calibrated mic did you have if any. Such a PTA to remove access door? I use J lugs and wing nuts.

[ka7niq]

Ka7nig.....Real low bass....??? What do you mean by that discription???? You cant get some thing for nothing... Do you mean another octive?? or just a small boost in the same octive response??? or change in tonality of same frequency??? I can get that just changing damping factor of amp... Other than by ear ,did you verify with measurements??????? And if by measurments what instruments did you use.... What type of room did you use?? Do you have a full anechoic chamber??? Half chamber ??? Live end dead end room?? What calibrated mic did you have if any. Such a PTA to remove access door? I use J lugs and wing nuts.

Good idea for the access door HornZak !

Forgive me for calling you that, but it would be a good moniker ?

I am aware of your aversion to stuffing the rear chamber from advice you gave me in another thread.

I did remove the stuffing, but it seems like I lost a little low bass.

This could be due to air leaks, or different amps.

I am still experimenting.

Is it NOT possible that Speakerlab wants stuffing, and designed for it ?

[DrewBolce]

I found that the light stuffing smoothed a ~100hz hump out (Speakerlab woofer). It is possible the hump is making you think you have lower bass loss since all is relative. I use pretty accurate computer based analysis, all calibrated, etc. However for subjective tests I like the Bach Fugue organ piece. I can't recall the exact name right now but it boasts notes down to 17hz.

I went to Home Depot and got some large flat head furniture screws that are driven by a square bit. Using my cordless drill I can get the panels off very fast without stripping the holes ( they are about 3 inches long with a 3/8 thread). I use a closed cell flat foam gasket for the seal, again from the hardware section of the big orange box.

I use water pipe insulation to seal between the wall and the tailboard. If you have not done this you will not get any reliable or repeatable bass results, in my experience.

[ka7niq]

I found that the light stuffing smoothed a ~100hz hump out (Speakerlab woofer). It is possible the hump is making you think you have lower bass loss since all is relative. I use pretty accurate computer based analysis, all calibrated, etc. However for subjective tests I like the Bach Fugue organ piece. I can't recall the exact name right now but it boasts notes down to 17hz.

I went to Home Depot and got some large flat head furniture screws that are driven by a square bit. Using my cordless drill I can get the panels off very fast without stripping the holes ( they are about 3 inches long with a 3/8 thread). I use a closed cell flat foam gasket for the seal, again from the hardware section of the big orange box.

I use water pipe insulation to seal between the wall and the tailboard. If you have not done this you will not get any reliable or repeatable bass results, in my experience.

Yeah, I gotta get some decent screws that are easier to remove.

The stuffing does seem to smooth the response,and too much really overdamps it.

No stuffing at all gives a fat, full, boomy bass.

My moldings stop my tailboard from contacting the wall corners.

how important is this ?

[DrewBolce]

Beyond important. Some of my early computer measurements showed a significant change in db and frequency response. The water pipe insulation comes in two versions for 1/2" and 3/4" pipe, get both it is cheap. One of them should work. If you are not familiar this stuff can be cut with scissors in order to clear floor and chair rail moldings. The key here is to get an airtight, gap free joint. I am told the top is not as important as the sides but I did both.

[ka7niq]

Beyond important. Some of my early computer measurements showed a significant change in db and frequency response. The water pipe insulation comes in two versions for 1/2" and 3/4" pipe, get both it is cheap. One of them should work. If you are not familiar this stuff can be cut with scissors in order to clear floor and chair rail moldings. The key here is to get an airtight, gap free joint. I am told the top is not as important as the sides but I did both.

Wish I could see a picture of how you have it applied ?

Because of the moldings, the tailboard is out a ways from the corner.

Is this the way a folded horn works ?

Air shoots into the tailboard and fans out into the corners which form the horn ?

So what you are saying is any air leaks between tailboard and corners is not good ?

The question is HOW bad is it ?

Hate to go hacking up my home, but I will

[ZAKO]

Ka7,,,,,,,Hornzak I like that ,,, But ive been called worse... Pipe inssulation is a must.....But most important place your fingers lightly over the access door...You will feel a bit of vibration...I place a long strip of 1" by 6" wood across the door. to stop vib. the other side of cabinet does not vibrate.

[ka7niq]

Ka7,,,,,,,Hornzak I like that ,,, But ive been called worse... Pipe inssulation is a must.....But most important place your fingers lightly over the access door...You will feel a bit of vibration...I place a long strip of 1" by 6" wood across the door. to stop vib. the other side of cabinet does not vibrate.

Wish I could see a picture of how the pipe insulation is used Maron ?

Does it just go on the tailboard ?

Freddyi also suggested beefing up the access door ?

What about sealing the bloody thing ?

On the Speakerlab SK's, the woofer wires go through the door, gotta make sure no leaks ?

HOW critical are a few small air leaks in a folded horn ?

[WMcD]

If I may comment. There are several issues.

1) The sealling of the back chamber is very important and PWK commented on it. In one publication he discussed the use of a water manomometer (?) to check the back chamber. This also shows up in the EV Gregorian home built manual.

I'd love to find the time to check out my various bass horns. I suspect some of our beloved bass horn may be suffering.

A long time ago I checked my home built Belle - like horns with and without stuffing and could not find a difference. Now I wonder if a leak (I was very careful building them) may have overshadowed a leak.

2) The seal against the wall is difficult to quanitify. We generally get reports here that sealing with the pipe insulation or similar material leads to vast improvements. But it seems that you're asking whether a flaw of sealing amounting to one-pin-head, versus three-pin-heads . . . equates to exactly what . . ? Very hard to say.

3) My brother-in-law moved to a new, used house and I was in charge of setting up the SKs. I did use the 3/4 inch slitted pipe insulation from Home Depot. There is also non-slitted.

Unfortunately there was no time for photos. Further, to some extent, I didn't have time to make it perfect. My comments:

a) I addressed the three line interstections formed by the left and right sides. I.e. the tailboard, top of the bass bin and the bottom.

You can;t really see how bad the problem is without taking off the side grills and pushing the units into the corner. I had to sit on the carpet and and sort of do a seated squat press to slide them on the carpet. Feet on the front bottom.

Once you do that you can see and feel the extent of the gap to be filled. Naturally, no one can tell you what you have to do with exactness because your problem is probably unique. You really have to take a look at the problem and the material you can get at HD. It is not difficult. But there are no pat answers, in my view. Then you have to haul the beasts away from the wall and take a good look at solutions to filling the gap.

c) In my situation, the walls were not plumb. There was at least 1/4 inch worth of problem. The plastic baseboard was part of the problem. Real K-Horns have a cut out at the base. You can figure something.

d) I used the pipe insulation. You might consider a foam weather strip with a rectangular cross section. (A very good alternative) I might use that if I had to do it again. The pipe insulation from HD had sticky surfaces at the slit with a tear off shield, like a Band Aid. It helps keeping things in place.

e) The round stuff is about $2 for 6 feet. So your total investment here is less than $20 overall. A good investment.

f) The stuff cuts with kitchen shears very nicely. But, you'll see that it needs to be mitered (angle cut) at the corners where the tail board meets the top and bottom plates of the bass horn. I flubbed a bit on the first try.

If you use the round pipe insulation, I would suggest using one length cut up into an few 6-inch lenghts as an experiment to get an idea of how you have to make the miter cuts at the intersections at the top and bottom of the tailboard. It is a little puzzle. Not difficult to do, but hard to describe. Drat, lack of photos.

Best,

Gil

[ka7niq]

I was looking around Google, and found several instances of doing things with the back chamber of folded horn woofers.

One scheme was to port that chamber, and allow bass below horn cut off.

I really do not understand bass horns at all, or why the rear chameber should be any different then any other rear wave containing device like a sealed or vented box. ?

Maybe as I learn more ?

I will try the insulation, where do you get a water meter, LOL

[ZAKO]

Porting the chamber was met with complete folly....Only a dumb fool would attempt some thing like that...The back electromotive force was lost as a compression chamber... Plus the horn design cost him the resale value of the bass bin..nothing was gained.. That person should be horsewhipped, salt rubbed into his wounds and left out in the sun to die. If you want to improve the horn design you must start from scratch,,,Thats what Paul Klipsch and Roy Delgado did and the JUBILEE was born. There is no free lunch with tweeking the bass bin other than what we have stated !!!!!

[dkalsi]

thought I post this up while you guys discuss Speaker Labs K-horns

http://cls.audiogon.com/cgi-bin/cls.pl?spkrfull&1198777438

no affiliation - etc.

[ka7niq]

You could always place the port on access door Maron ?

That way, if it don't work, just make another door ?

So, what you are saying is the air spring will be lost if we tamper with the rear chamber I guess.

I have seen dome compression drivers with felt pads under the domes, what's up with that ?

[ka7niq]

thought I post this up while you guys discuss Speaker Labs K-horns

http://cls.audiogon.com/cgi-bin/cls.pl?spkrfull&1198777438

no affiliation - etc.

Yeah, I saw that.

No comparasion to my Speakerlab SK's, that's for sure.

I do not know WHAT those are ?

Even the SpeakerLab K's had a crossover with capacitors.

Those could be Speaker FACTORY clones ?

SpeakerLab was quite successful in it;s day.

I know, I lived in Seattle back in SpeakerLab's heyday.

A copy of Speakerlab called Speaker Factory popped up.

They did offer a folded horn speaker.

[mike stehr]

You could always place the port on access door Maron ?

That way, if it don't work, just make another door ?

So, what you are saying is the air spring will be lost if we tamper with the rear chamber I guess.

I have seen dome compression drivers with felt pads under the domes, what's up with that ?

You put a port on the access door, and all the air will vent out of the compression chamber......."Compression" "Air spring"...think about it. I would guess that the air wont' properly flow into the horn/wall flare interface. Maybe lost bass, efficiency.....you lose bass efficiency, and the mid and top-end will start to sound hot. It would be the same thing as drilling a big 3 inch hole in the center of your Speakerlab K. All the air would go out the hole, not the horn.

Dunno about felt under compression drivers....damping? From the backwave?

I have a Lascala project going. I cobbled them together with parts on hand until I can get the right parts. I was using a pair of Magnavox 8 ohm 15" woofers. Not optimum with too high a fs, and too small a magnets, but I had to try it. It was too objectionable, (boomy, no low extension, one note kinda sound) so they are getting sanded now.

But with one I put about a half-pound of polyfil in the doghouse, just to see. The 8 ohm drivers are too inefficient as it is, the polyfil made it even a bit more inefficient. Not much, but noticed. It did seem to smooth out the bass I geuss, but it also seemed to dampen the higher frequency range of the bass. I noticed no lower extension of bass from the polyfil. Maybe I'll try it again with the K33 replacement...who knows...

I think keeping the compression chamber sealed as much as possible like PWK mentions, is the best option. He designed the things.

[ka7niq]

You could always place the port on access door Maron ?

That way, if it don't work, just make another door ?

So, what you are saying is the air spring will be lost if we tamper with the rear chamber I guess.

I have seen dome compression drivers with felt pads under the domes, what's up with that ?

You put a port on the access door, and all the air will vent out of the compression chamber......."Compression" "Air spring"...think about it. I would guess that the air wont' properly flow into the horn/wall flare interface. Maybe lost bass, efficiency.....you lose bass efficiency, and the mid and top-end will start to sound hot. It would be the same thing as drilling a big 3 inch hole in the center of your Speakerlab K. All the air would go out the hole, not the horn.

Dunno about felt under compression drivers....damping? From the backwave?

I have a Lascala project going. I cobbled them together with parts on hand until I can get the right parts. I was using a pair of Magnavox 8 ohm 15" woofers. Not optimum with too high a fs, and too small a magnets, but I had to try it. It was too objectionable, (boomy, no low extension, one note kinda sound) so they are getting sanded now.

But with one I put about a half-pound of polyfil in the doghouse, just to see. The 8 ohm drivers are too inefficient as it is, the polyfil made it even a bit more inefficient. Not much, but noticed. It did seem to smooth out the bass I geuss, but it also seemed to dampen the higher frequency range of the bass. I noticed no lower extension of bass from the polyfil. Maybe I'll try it again with the K33 replacement...who knows...

I think keeping the compression chamber sealed as much as possible like PWK mentions, is the best option. He designed the things.

But I keep reading stuff like this http://www.diyaudio.com/forums/showthread/t-25493.html

and this http://www.freepatentsonline.com/7252176.html

that make me wonder ?

Getting back on topic regarding SpeakerLab, one must wonder if the amount of the stuffing for the rear chamber was taken into account when they designed their woofers ?

Is it not possible they purposely designed their woofers to work in the Klipsch Folded Horn with stuffing ?

IME, a stuffed chamber has some advantages over an unstuffed one, like keeping sound from re radiating through the cone.

[ZAKO]

Due to the V shape of the chamber the sound will not reradiate through the cone....You have a better chance of re rediating from the spokes of woofer basket. as far as reradiating in back chamber of a mid driver that motion is very miniscule compaired to a woofer cone....What you have been reading on the other sites is voodoo science and half truths of obsessive compulsives pontificating there own false adgenda....Paul Kliptch new what he was doing.