bd pipes port material?

[porkchop61]

Well, first impression was that they are a bit muddy. This is after listening to the same amplifier setup (SE using KT66's at the moment) with '80s two-way JBL bookshelf speakers. Again, these have the unknown Kenwood drivers in them, so I have no idea what the specifications are on the drivers.
To be fair, this is my first listen to these types of speakers. I also own a pair of Altec A-7's (I really like the horn sound) but the A-7's have a low WAF due to their size

I will say that the speakers sounded MUCH better after switching the amplifier over to a pair of EH 6CA7 tubes. These tubes (along with another pair of EH EL34's) seem more "forward" sounding in this amp, so that's probably what changed the sound more to my liking. I have found the KT66, 6L6 family of tubes to be more "warm" sounding. I haven't changed back to the original KT88's that the amp was originally built with just yet. I'm slowly testing all my tubes to see which pair I like the most.

I would assume the speakers will sound totally different with a "real" pair of drivers like the Fostex 103's or a Tang Band W4-616SA.

Glenn

 

[GM]

Yeah, this cab was designed for ACR FE103S drivers, so all others will probably need some form of EQ to work their best.

GM

 

[porkchop61]

I just wanted to update this post as to the sound of these speakers.
I've replaced the "El Cheapo" Kenwood drivers with a set of Tang Band W4-616SA's. These are really good sounding cabinets with the right drivers in them! Still not my choice for rock music though (which I knew going into this build). Excellent for classical and jazz though.
Parts Express has the drivers on sale now:
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=264-818

 

[chrisb]

I just wanted to update this post as to the sound of these speakers.
I've replaced the "El Cheapo" Kenwood drivers with a set of Tang Band W4-616SA's. These are really good sounding cabinets with the right drivers in them! Still not my choice for rock music though (which I knew going into this build). Excellent for classical and jazz though.
Parts Express has the drivers on sale now:
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=264-818

HP filter them around 120 or so and add a pair of powered subs, and the performance on rock will improve significantly - but of course not approach concert level performance of large multiway PA horn types.

These cabinets really do shine with the drivers which Bert originally intended, the FE103E ( not Sigmas)

 

[GM]

Then why did Bert call them (ACR) FE103S? http://www.tnt-audio.com/intervis/lowthernl_e.html

True, it's not a bone-fide Fostex since these were assembled using Fostex parts by ACR, but the Sigma-like horn driver specs this pipe is alleged to be designed for certainly falls more in line with the Sigma series than the basic FE103 series:

Fs = 65Hz
Vas = 0.39ft^3
Qms = 3.1
Qes = 0.26
Pd = 5W
Re = 6ohm
Dia = 2.75"
Sd = 5.94"^2
sens = 92.52dB/W/m

All that said, unless some form of EQ is used to raise its effective Qts (BSC, high output impedance amp or similar), then a higher Qts driver such as the FE103E is a better choice overall.

GM

 

[JeroenR]

I bought the FE103S divers from Bert when I built my pipes. And.. hope I remember this correctly, Bert designed a BSC and advised to use a low quality coil or inductor as the loss of <insert some technical word here> would be beneficial.

Jeroen

 

[GM]

Right, since low quality coils, inductors have a higher resistance, lowering the driver's <effective motor strength>, i.e. raising its effective Qes, ergo Qts.

GM

 

[planet10]

(ACR) FE103S

That is indeed what they were designed for. I doubt ACR actually assembled them, much more likely an OEM order for 1000+ units. They were an FE103 with an extra magnet disk.

dave

 

[chrisb]

Then why did Bert call them (ACR) FE103S? http://www.tnt-audio.com/intervis/lowthernl_e.html

True, it's not a bone-fide Fostex since these were assembled using Fostex parts by ACR, but the Sigma-like horn driver specs this pipe is alleged to be designed for certainly falls more in line with the Sigma series than the basic FE103 series:

Fs = 65Hz
Vas = 0.39ft^3
Qms = 3.1
Qes = 0.26
Pd = 5W
Re = 6ohm
Dia = 2.75"
Sd = 5.94"^2
sens = 92.52dB/W/m

All that said, unless some form of EQ is used to raise its effective Qts (BSC, high output impedance amp or similar), then a higher Qts driver such as the FE103E is a better choice overall.

GM

Not to nit pick, or second guess your understanding of the provenance of the "ACR drivers", but here is a snip of exact quote from the interview:

TNT-Audio >
Suppose you want to build an inexpensive no-crossover loudspeaker that can sound fine with low-powered SETs. Where would you start from?

BD >
Then the Fostex (ACR) FE 103 S in a TQWP or reflex cabinet would be a very nice start.
This driver isn't expensive, has a 92dB sensitivity plays up to 20k and needs no filter. The only drawback is the small cone which makes it almost impossible to have a party with them...

I perhaps mistakenly understood that the ACR was essentially a private label OEM rebranding - sometimes the only difference in the product is the sticker and lack of printed literature and "factory packaging".

(and it's probably unlikely that Bert would be inclined to clarify the question )


FWIW, I built at least 10 prs of these over the years, using several antecedents or variants of the current official FE103E (i.e. RS 40-1197 and vintage Foster alnico magnet versions)

http://homepage.mac.com/tlinespeakers/FAL/images/foster10RG11-220605.jpg


Actually, I've not heard current production FE103E in this design, but it's hard to imagine them not sounding equal or superior to the 40-1197.


As for "impossible to have a party with them...", I guess it's a question of how loud you need to get - Metallica at 105dB just ain't my thing. In fact, I found the endearing qualities of this particular design to include spacious soundstage and imaging at even moderate late-night listening levels - relaxed and intimate enough that I never felt the need for higher than probably the mid 90's.

 

[JeroenR]

I built them with just one driver per speaker and no filter. I love the sound with jazz, and light classical music. Voices/singing sounds very very good. They fail with pop music which for me is an added bonus....

I'm now scanning ebay for 2 extra FE103S drivers as I recently got a 4ohm amp. They are scarce unfortunately.

Jeroen

 

[GM]

OK, I could have misinterpreted some remarks made about ACR in general and these drivers in particular, but the way it was explained to me was that these were Swiss made Fostex, but if the main (only?) difference is an extra magnet, then maybe it just means ACR added it to a FE103 to make it their own.

Then again, I've never seen an extra magnet to an existing driver lower Qts this much, so pardon me for being a bit skeptical for now.

GM