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panos29
09-19-2005, 11:07 AM
O.K its been a long time since I joined and follow this excellent forum, and I feel it is time to ask for some help on a design I am working in my mind for some time.

I got to tell I am into high efficiency speakers, 2 way at most and low power amps like less than 20W. My quest so far led me to horn loaded 15" tannoy dual concentric design I enjoy listening at, all the time. I am now ready to go into a different approach. I am about to design a 2 way bass reflex system with a 15" or 12" LF woofer paired with an HF compression driver I already have(altec 806a), matted to a 811B horn(i know I am "cheap").

I would like to ask for any proposals as far as the LF is concerned, I prefer older high effieciency woofers like 130A, D130, 2220(seems identical to 130A) and 2205. Which of these(or others) do you propose for this simple system? I really prefer alnico and non foam souround.

I was after a pair of K145s for some time but seems very difficult to locate a pair. Moreover, if anybody here is willing to part with such a "vintage" pair I am all ears. I recently located an 2205 pair that seems nice according to T/S parameters and an e145 pair that seems low sensitivity model but in excellent optical condition. I also think altec 515 and 416 may do nicely as well as TAD and Precision Devices although I prefer something from JBL. Please throw some light to my darkness...:banghead:

panos29
09-20-2005, 02:24 AM
Unfortunately E145s are not an option anymore:( some ebay trader won them, anyway altough nice modern woofer it was a bit out of focus as far as my project is concerned...

Earl K
09-20-2005, 04:14 AM
Hi

- The closest equivalent to the K145 that I can think of is the Altec 416-8B ( Alnico version of the "ferrite" 416-8C ) .

- They both have fairly light weight cones ( good for mid-range transients ) in the 60 to 70 gram range ( similar range as the 2220 or 130a ).

- I believe the 416 is also an underhung coil like the K145 ( good for maximum cone control and therefore, "better" articulation in a woofer ).

- The Altec 416 has a lower Fs than the 145 , so it will ultimately give a bit more bass extension .

- One speaker not mentioned , is the le15a ( 16 ohm ) . It has an underhung coil, working in a deep gap with a moderately weighted cone ( around 100 grams which is similar in weight to the 2205a ). All in all, for an efficient speaker , these represent a good set of design compromises . It's impedance might be a problem for you .

:cheers:

panos29
09-20-2005, 04:41 AM
Dear Earl, thank you so much for answering, I forgot to mention that since my target is a 2way system the woofer hf response should be at least 800Hz in order to have an fairly acceptable mating with my 800Hz Hf horn. 416-8b is a nice woofer but most of the times overpriced, thus I was thinking something in the lines of 2205 or 2220 that can be had for reasonable amounts, the question is, are these going to extend to around 800Hz as good as the 416 or 515? Moreover LE15s are super nice, though these have foam surrounds I rather try to avoid and also expensive. Anyway if we consider the 2220 and 2205, what is a reasonable cabinet volume if we suppose around 40Hz tunning? I really like fast mid bass instead of sub-bass responce and really hate booming and also I never listening ny nusic louder than 105dB most of the times I listen to 90dB level.

Earl K
09-20-2005, 05:30 AM
Hi

- Both the 2205 and the 2220 are happy with an 800 hz crossover point .
- There are guys around here using the 2225 ( successor to the 2205 ) and they like them quite well .

- The 2205 has almost a 30 gram heavier cone which translates into better bass fundamentals. The 2220, because of it's lighter cone handles the harmonics region better .

- If you have the time to look , see if you can find a pair of alnico 2220s that have been previously reconed with the 2205 or the 2225 kit. These hybrids aren't as rare as one might think. I have a pair. Many PA companies will have them laying about. In the 80s' when midrange duty was handed to 12 or 10 inch drivers , a lot of companies reconed their 2220s with 2225 cone kits creating this bass hybrid . These "bass" speakers are typically being retired and replaced by other sorts with much greater power handling as well as greater Xmax abilities ( & usually with the loss of some resolution ) .

- This hybrd has a mix of qualities from both the 2220 and the 2225 ( 2205 ).
The deeper gap ( 9mm / .35" ) that the 2220 has versus the 7.1mm / .28" ( in the 2225 ) makes quite a difference to the overall playback resolution . This deeper gap ( and a voice coil not completely centered in the gap, caused by the wrong kit in the wrong gap ) will reduce the Xmax figure / but really / for home HiFi use , it's not an issue ( in fact , for some reason, in PA work it was never an issue ). IMO, this hybrid is the best of the bunch . It also has the smoothest midrange when compared to the two originals ( maybe it's the old alnico / I don't know )
- There , that secret is out . ;) :p

- Build 4.5 to 5 cu' ( 127.4 to 141.6 litres ) boxes , tuned to 40 hz. Don't ask me for the port length / go get yourself some tuning software ( if you don't have any ) .
- Don't expect anything much below 40 hz ( except a bit of extra VLF response caused by room gain ) .


:)

panos29
09-21-2005, 05:38 AM
Thank you very much Earl for all the help and knowledge shared! To my astonishment, things were not as easy I considered them to be, meaning I played around with T/S parameters of the woofers under consideration using the JBLspeakershop in vented arrangements and the outcomes were very bad at least as far as these simulations are concerned. Meaning not matter what arrangement I tried on 2220, 2205, D130, I could not make it to a nice responce to my eyes. The best I could do was with 2205 at 150lt and Fb38Hz, the -3dB was from 100Hz to almost 40Hz. Is this responce normal for such a woofer or I got something very wrong? Definitely there is no such thing as a "free lunch"! :banghead:

spkrman57
09-21-2005, 06:12 AM
Check out the "Pi speaker" forum on the "AudioRoundTable" forum main page.

Wayne (Parham) uses several JBL/Eminence drivers for a 2-way configuration.

He recommends a 2.6 cubic ft(interior) box. I use anything from 3 to 5 cubic ft tuned to 40hz and get great results.

I also crossover my horns(1" drivers that is) at 1.6khz 3rd order for best results.

I believe 45 hz at 3 db down is pretty honest spec, plenty of midbass dynamics and slam.

Also, try and get a pair of Altec 902's as they go higher in HF response than the 806, also 2 db more efficient.


Hope this helps.

Ron

panos29
09-26-2005, 04:08 AM
Unfortunately the woofers I was after in Ebay were not won by me as I was away from home and now those 2205s went for 140 euro, but not to me:(
Next possibility now is a pair of altec 416-8c from a friend but this is not alnico :banghead: I would dare to ask if any of you got a working pair of 2205s or similar that would like part with? Any help or proposal welcomed! I am also after a pair of working alu diaphragms for my 806 drivers.

Thanks in advance
Panos