Philips 10100-8 10" woofer replacement in Transmission Line cabinets

[Paul K.]

Re: Philips 10100-8 10" woofer replacement in Transmission Line cabinets

This guy must be related to our old "friend" villastrangiato who also had weird ideas on TLs. I have to assume keilau would use T/S parameters to design and optimize a vented or sealed box for a specific driver, and wouldn't expect to then drop in any other driver that fit the cutout and expect the same results or even good results! Why, then, would he assume a TL would be any different? His comment about being "an engineer in trade" really irked me (see Post 10). Sure we have a bunch of hobbyists that partake in this hobby that may not have technical training/education or a deep understanding of everything (me included in the latter), but keilau came across as presuming he was smarter, more experienced and better educated than everyone here, and that's simply not the case (I really dislike pompous people).
Paul

[ATTACH=CONFIG]34870[/ATTACH]


I think you just cut that Gordian knot with the sword of reason.

[Pete Schumacher]

Re: Philips 10100-8 10" woofer replacement in Transmission Line cabinets

This guy must be related to our old "friend" villastrangiato who also had weird ideas on TLs. I have to assume keilau would use T/S parameters to design and optimize a vented or sealed box for a specific driver, and wouldn't expect to then drop in any other driver that fit the cutout and expect the same results or even good results! Why, then, would he assume a TL would be any different? His comment about being "an engineer in trade" really irked me (see Post 10). Sure we have a bunch of hobbyists that partake in this hobby that may not have technical training/education or a deep understanding of everything (me included in the latter), but keilau came across as presuming he was smarter, more experienced and better educated than everyone here, and that's simply not the case (I really dislike pompous people).
Paul

The only thing that matters in TL design is the use of wool, period. But isn't it odd that he needs a specific woofer recommendation from us that somehow matches the Phillips woofer?

Matches how exactly? Same diameter? Same motor strength and cone mass? In other words, same TS parameters?

Engineer my arse. Any engineer worth a hoot would realize that the parameters defining low frequency performance are the very things needed to pick a woofer that would drop in to the design without worrying about the results. The ill-logic being touted that somehow a TL must have wool, and that woofer parameters don't matter, stretch the bounds of credibility to the breaking point.

Why does Mr Know It All need our help picking a woofer? We don't have a clue about how to design a TL.

Especially you Paul . . .

[Sidi]

Re: Philips 10100-8 10" woofer replacement in Transmission Line cabinets

I have an EE degree. I design radio transmitters. Being an EE doesn't instantly make you an expert at everything.
I'm fine with having an amateur understanding of acoustics - for now.

[fdieck]

Re: Philips 10100-8 10" woofer replacement in Transmission Line cabinets

I have an EE degree. I design radio transmitters. Being an EE doesn't instantly make you an expert at everything.
I'm fine with having an amateur understanding of acoustics - for now.

To quote George Bailey (no relation to A R as far as I know), "It comes in handy down here bub.

[billfitzmaurice]

Re: Philips 10100-8 10" woofer replacement in Transmission Line cabinets

I have an EE degree. I design radio transmitters. Being an EE doesn't instantly make you an expert at everything.

It certainly doesn't make you an expert in acoustical engineering.

You can use stuffing (whatever the material) to alter/shape the low-end response, and if you use enough (by density but most assuredly by length) you can make the column act in a non-resonant mode because you have literally stuffed the life out of it. By doing that, you have completely eliminated all contribution to the system from the terminus.

The trick with a TL is to use enough stuffing to damp the pipe harmonics without damping the 1/4 wavelength resonance. It's not all that difficult, as the harmonics show up as bumps on an impedance sweep, while the 1/4 wavelength resonance (fp) is a full on impedance peak. When you've added enough stuffing to get rid of the former while not significantly reducing the latter you're good. But it does take a fair amount of trial and error to get it right.

[martin]

Re: Philips 10100-8 10" woofer replacement in Transmission Line cabinets

The trick with a TL is to use enough stuffing to damp the pipe harmonics without damping the 1/4 wavelength resonance. It's not all that difficult, as the harmonics show up as bumps on an impedance sweep, while the 1/4 wavelength resonance (fp) is a full on impedance peak. When you've added enough stuffing to get rid of the former while not significantly reducing the latter you're good. But it does take a fair amount of trial and error to get it right.

The first part of your response is correct, the higher harmonics (resonances) of the TL show up as bumps on the impedance curve that can be damped by fiber stuffing.

However, the second part of your response is not correct. There is no quarter wavelength resonance of the TL speaker system. There is a quarter wavelength response where the driver's motion is supressed and the open end of the enclosure produces the bass, typically this occurs very close to the frequency of the quarter wavelength resonance of the box alone. When a driver is mounted in the box to form a completed speaker system two new resonances are formed, these can be seen as the double humps in the impedance curve of the unstuffed TL system. These are the mathematical resonances and they will bracket the driver's fs and the box's quarter wave resonance. It is just like what happens in a bass reflex box when the driver is added to the enclosure.

No matter how we define the mathematical resonances of the TL the impedance and SPL curves will be the same. But for an engineer, knowing the resonances and understanding what is a resonance and what is just a response of combined resonances is important in advancing the engineering of the enclosure in a mathematically predicatable manner and not relying on cut and try methods or voodoo and magic.

[billfitzmaurice]

Re: Philips 10100-8 10" woofer replacement in Transmission Line cabinets

When a driver is mounted in the box to form a completed speaker system two new resonances are formed, these can be seen as the double humps in the impedance curve of the unstuffed TL system. These are the mathematical resonances and they will bracket the driver's fs and the box's quarter wave resonance.

Not in those that I've built and measured. They showed a distinct peak at the pipe frequency, with smaller bumps at the harmonics. When stuffed the fp peak remained, at the same frequency, while the harmonic bumps were flattened. But I don't do mass loaded TLs, which are closer to bass reflex than TL in both their operation and their impedance characteristics.

[martin]

Re: Philips 10100-8 10" woofer replacement in Transmission Line cabinets

Not in those that I've built and measured. They showed a distinct peak at the pipe frequency, with smaller bumps at the harmonics. When stuffed the fp peak remained, at the same frequency, while the harmonic bumps were flattened. But I don't do mass loaded TLs, which are closer to bass reflex than TL in both their operation and their impedance characteristics.

How did you determine the pipe frequency? I do not mean the frequency with the driver in the box. I mean the resonant frequency of the air volume in the box. TL, ML TL, or bass reflex thay all behave the same in terms of combining the box resonance with the driver resonance to form system resonances.

[Paul K.]

Re: Philips 10100-8 10" woofer replacement in Transmission Line cabinets

I've built numerous TLs, both mass-loaded and tapered. I've measured the impedance vs. frequency characteristics of their woofers in the stuffed lines and got results almost exactly as predicted by Martin's software. There are twin impedance peaks bracketing the woofers' Fs and the line's 1/4-wave resonance.
Paul

Not in those that I've built and measured. They showed a distinct peak at the pipe frequency, with smaller bumps at the harmonics. When stuffed the fp peak remained, at the same frequency, while the harmonic bumps were flattened. But I don't do mass loaded TLs, which are closer to bass reflex than TL in both their operation and their impedance characteristics.

[thekorvers]

Re: Philips 10100-8 10" woofer replacement in Transmission Line cabinets

Better yet, you read the AES articles by George L. Augspurger. His work was to TLs as Theile/Small were to vented boxes. It addresses all of your concerns, showing where Voigt, Bradbury and Bailey were correct, and where they were off the mark. Perhaps those three would have been closer to being correct had they the ability to incorporate T/S into their calculations, but as they pre-dated T/S they obviously could not do so.
If you are not an AES member and don't wish to purchase the Augspurger preprints this thesis is the next best thing, which expands even further beyond Augspurger's initial work:

http://citeseerx.ist.psu.edu/viewdoc...=rep1&type=pdf

Excellent dissertation on electroacoustic analysis of transmission line loudspeakers!

[michiganpat]

Re: Philips 10100-8 10" woofer replacement in Transmission Line cabinets

dumb question, but if the original phillips drivers are in good shape other than the rubber surrounds stiffening, you could try rescue the phillips drivers....if the rubber is stiff but not cracked, I've heard of wiping automotive brake fluid on rubber surrounds to help soften them back up. If they are cracked, you could cut the rubber surrounds off and either replace them with new rubber surrounds or new foam surrounds--measure your woofer OD, roll OD, roll ID, cone ID and note attachment type (flat or angled, glued to the front or rear of the cone) and start looking...there's a number of options for both butyl rubber and foam surrounds out there, especially on ebay. this option would probably be cheaper, and retain closer to proper driver parameters than trying to find a "drop in" replacement.

[Face]

Re: Philips 10100-8 10" woofer replacement in Transmission Line cabinets

Replacing rubber surrounds with foam surrounds would change the T&S parameters.

[Paul K.]

Re: Philips 10100-8 10" woofer replacement in Transmission Line cabinets

But according to the OP's "educated" opinion, the T/S parameters don't matter at all in TL design or performance!:p
Paul

Replacing rubber surrounds with foam surrounds would change the T&S parameters.

[michiganpat]

Re: Philips 10100-8 10" woofer replacement in Transmission Line cabinets

Replacing rubber surrounds with foam surrounds would change the T&S parameters.

true, but it still might be closer than some completely different driver....and like I said, there's a number of options for butyl rubber surrounds out there, too

and that experiment will most likely cost $20-30 at most for the pair, vs. $60-150 for the 2 woofers he mentioned....

[Pete Schumacher]

Re: Philips 10100-8 10" woofer replacement in Transmission Line cabinets

true, but it still might be closer than some completely different driver....and like I said, there's a number of options for butyl rubber surrounds out there, too

and that experiment will most likely cost $20-30 at most for the pair, vs. $60-150 for the 2 woofers he mentioned....

That assumes the motor strength of the original driver remains all these years later.

Oh, strike that. Like Paul K reiterated, TS parameters don't matter, only wool matters in the design of a TL.