Hi,
I am planning a Alpha TL speaker (Rick schultz) with Fostex full range drivers FE166en. My room is smallish approx 18 feet X 10 feet and my listening position will be around 11 feet away from the speaker. The speakers will still be around 6 feet to 7 feet away from the back wall. Distance between them will be around 7 feet approx.
I am not going to connect these speakers directly but going to have some kind of BSC + zobel in between to tame the mid-high frequency. Also have used x-sim to arrive at a near perfect SW response on the speaker system.
The box dimension with the published data sheet has a poor WAF due to my smallish room as its been shared by other members of my family. I am planning a tuning freq of 72Hz, which gives me a width of 7.25" and a depth of 12.5" considering golden ratio cross-section.
Expert's opinion needed in - Is alpha TL a good design option given my room dimension? I have tried ATL with 2 way speaker and have found the bass to be a little less in punch. But they were drivers with a low Vas (12 liters). The FE166en has a Vas of 37 liters which looks impressive on the low end front imo.
These are the results of simulation from published data sheet which i get from Xsim. I am going to build the compensation network with these simulations which gives a flat impedance, a pure resistive load and a near perfect square wave. Tweaks will follow based on my subjective experience which i am sure will be required to consider my room dimensions.
Am not sure if the measured response of the speaker in the box will give me similar results or even close given the room effect and measurement artifacts.
The drivers will take one more week to arrive and the box building will take a couple of weeks given my travel plans. But will try and complete atleast by next 3 to 4 months and post my findings.
Thanks for looking.
I am planning a Alpha TL speaker (Rick schultz) with Fostex full range drivers FE166en. My room is smallish approx 18 feet X 10 feet and my listening position will be around 11 feet away from the speaker. The speakers will still be around 6 feet to 7 feet away from the back wall. Distance between them will be around 7 feet approx.
I am not going to connect these speakers directly but going to have some kind of BSC + zobel in between to tame the mid-high frequency. Also have used x-sim to arrive at a near perfect SW response on the speaker system.
The box dimension with the published data sheet has a poor WAF due to my smallish room as its been shared by other members of my family. I am planning a tuning freq of 72Hz, which gives me a width of 7.25" and a depth of 12.5" considering golden ratio cross-section.
Expert's opinion needed in - Is alpha TL a good design option given my room dimension? I have tried ATL with 2 way speaker and have found the bass to be a little less in punch. But they were drivers with a low Vas (12 liters). The FE166en has a Vas of 37 liters which looks impressive on the low end front imo.
These are the results of simulation from published data sheet which i get from Xsim. I am going to build the compensation network with these simulations which gives a flat impedance, a pure resistive load and a near perfect square wave. Tweaks will follow based on my subjective experience which i am sure will be required to consider my room dimensions.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Am not sure if the measured response of the speaker in the box will give me similar results or even close given the room effect and measurement artifacts.
The drivers will take one more week to arrive and the box building will take a couple of weeks given my travel plans. But will try and complete atleast by next 3 to 4 months and post my findings.
Thanks for looking.
I will be using a Dared VP-300B SET which i think is 9 watts + 9 watts as per user manual.
This is the network i am planning to use with the FE166en,
An externally hosted image should be here but it was not working when we last tested it.
Yes, the stuffing density as per the calculation works out around 1.75 pounds/cubic feet. Will adjust the stuffing to balance the mids & lows by listening. IMO there is a very thin line between critical damping and over damping and could be adjusted by trial and error.
Thanks,
Hmm, it looks like you haven't factored in the amp's high output impedance's [Rs] impact on the driver's Qts, which will change your filter design and significantly lower the TL's design frequency [Fs/[Rs+Qts]]: mh-audio.nl - Home
GM
GM
Thanks for pointing out and the mh-audio link. I measured the Rs of my amplifier with an LCR meter and it shows an source resistance of 0.3 ohms. Substituting in the equation only marginally changes the Qts from 0.25 (published) to 0.256 which imo should be a fair approximation. I have not considered the speaker cable internal resistance in this calculation.
Not sure if i am missing something.
You're welcome!
You are based on the amp's specs, which states it's either 4 ohms or 8 ohms [AKA 'matching impedance' outputs] depending on the tap used, which will significantly increase the driver's effective Qts, though you need to measure them correctly to be sure: http://www.dared.us/products_vp300b.php
I don't have access to my tech info, so you'll have to find all the salient details among these postings: https://www.google.com/webhp?source...e=UTF-8#q=calculate tube amp output impedance
GM
You are based on the amp's specs, which states it's either 4 ohms or 8 ohms [AKA 'matching impedance' outputs] depending on the tap used, which will significantly increase the driver's effective Qts, though you need to measure them correctly to be sure: http://www.dared.us/products_vp300b.php
I don't have access to my tech info, so you'll have to find all the salient details among these postings: https://www.google.com/webhp?source...e=UTF-8#q=calculate tube amp output impedance
GM
Thanks once again for your inputs. I measured the output impedance of my amplifier using this link Impedance, and how it affects audio equipment from Elliot sound products and i got a value of 3.1 ohms. (i used the 8 ohms tapping)
Considering nominal impedance of the Fostex driver (8 ohms) the damping factor works out to be 2.58
using this link : mh-audio.nl - Home
when i substitute the Rs i get a new Qts value of 0.342.
When i recalculate my Alpha TL Box with these new values keeping the same pipe length, i get a different cross-section and stuffing values which is atleast 20% more than the published values with the increase in Qts.
Hence the crux remains in measuring the drivers TS-parameter with reasonable accuracy (> 98%) and also measuring the amplifier source resistance (Rs) too with reasonable accuracy (again >98%) to arrive at the box dimensions.
Again referring to the original white paper of Alpha TL its review comments by Augspurger mentions that in Alpha TL the cross-section & volume is not very important. More importance is given to the pipe length and stuffing (damping density).
Going by the amplifier source resistance method, the box size will again change by the change in amplifier as the source resistance has again changed.
@ GM - your further comments will be appreciated.
BR, Hari
Today afternoon i received the Fostex Drivers from Madisound and after a small break-in for 20 minutes @ 30Hz at moderate volume (around 4 watts) measured the TS parameters.
I noticed that the parameters are reasonably close to the published values within 6% overall and i can safely use the published values for my boxes (i presume they must have done a proper break-in before measurements).
I noticed that the parameters are reasonably close to the published values within 6% overall and i can safely use the published values for my boxes (i presume they must have done a proper break-in before measurements).
Thanks Bob. I will be using the published parameters for the box calculations. I am still confused about the Qts value. Should i consider the source resistance Rs of the amp as suggested by GM or can i safely ignore it. Please suggest.
I would have loved to make the Fostex published BLH design but am severely constrained by space in my room and hence settling for the next logical design of going for a TL.
Are Alpha TL going to be very bad for the FE166en? How about a TQWT instead? Looking for advise.
This is the shape of the box that i am planning to build. The terminus will open at the floor and there will be a clearance of around 2.5" from the floor which imo is good enough.
An externally hosted image should be here but it was not working when we last tested it.
If you're committed to the FE166, I'd suggest that a BLH designed for gain in the lower octaves might yield better results. At the risk of "peddling" a particular design -the FHXL and larger Woden Victor are two to consider. I've heard several drivers in the XL - two models of Alpair10, and Fostex FF165WK- and FE166s in the Victor.
Thanks Chrisb. I reviewed the published design for FHXL & Woden Victor and will find it difficult for approval considering the WAF factor as the room will be shared by other members of my family.
This is the only reason i am looking for a TL design rather than a horn design as dimension will be a bit modest with TLs. Within TL i have options of going for Alpha TL, MLTL, TQWT. Advise required on which will be the best choice.
Regards,
This is the only reason i am looking for a TL design rather than a horn design as dimension will be a bit modest with TLs. Within TL i have options of going for Alpha TL, MLTL, TQWT. Advise required on which will be the best choice.
Regards,
Thanks planet10 for your suggestions.
One of the major reason i considered the Fostex was to avoid the crossover completely. If i needed to add a subwoofer + crossover then the purpose of this project gets defeated.
Won't a active subwoofer + active filter @ 150Hz be a better option than a passive BW or LR filter considering filter phasing and sub/satellite integration issues?
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