TQWT with Fostex FE206E

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Hi,

I am playing a little bit with the FE206E. I had built the bass-reflex enclosure from the Fostex PDF with the recommended horn. That was quite ok, but I wanted to try a TQWT.

142085140_7b78acd989.jpg

(port facing to the floor, therfore the stands)

The few Excel sheets to simulate a TQWT gave quite promising results, telling the enclosure could go down to arround 30Hz with the Fostex.

As the enclosure is quite easy to built, I gave it a try:

175326699_ce4288c12b.jpg


Baffle width: 24,4 cm, port diameter 8,1 cm, lenght 12,1 cm.

The result was terrible. Mids and heights where wonderful, but no bass at all. Even male voices sounded thin. The BR enclosure was better in any way.

How can that be? What is wrong?

The reason why I'm playing with the 206 is, that bulding the Fostex recommended horn is to time consuming for me. I know Bob's design, but that needs a contour filter and I am loosing 3-4 dB of the 96dB. I need the 96dB (at least) for my 300b SET that I am building.

Thanks for you help,
Heinz
 
Definitely some thing grossly wrong, all the tqwts I have built have produced loadsa bass and low with it.

As you have built them I would cut out the bottom (terminus) completely and experiment with different heights until you find the right result.

Start at about 20mm and work up.
 
Morfeus said:
...The reason why I'm playing with the 206 is, that bulding the Fostex recommended horn is to time consuming for me. I know Bob's design, but that needs a contour filter and I am loosing 3-4 dB of the 96dB. I need the 96dB (at least) for my 300b SET that I am building.


You cannot avoid the baffle step with a single driver tall thin cabinet. BR, MLTL, TQWT, it makes no difference. A horn cabinet can be designed to boost frequencies below the baffle step, but to get to 30 Hz, the cabinet will be enormous. Mother Nature is a b, and Hoffmann's Iron Law prevails.

Second issue: Don't expect to get 96dB/w/m out of a 206E. Maybe in the ear-bleed highs, but not down where the music is. I wouldn't expect any more than 94dB/w/m best case. If you really need 96dB/w/m, you are going to have to make different plans.

Bob
 
Re: Re: TQWT with Fostex FE206E

Bob Brines said:


You cannot avoid the baffle step with a single driver tall thin cabinet. BR, MLTL, TQWT, it makes no difference. A horn cabinet can be designed to boost frequencies below the baffle step, but to get to 30 Hz, the cabinet will be enormous. Mother Nature is a b, and Hoffmann's Iron Law prevails.

Second issue: Don't expect to get 96dB/w/m out of a 206E. Maybe in the ear-bleed highs, but not down where the music is. I wouldn't expect any more than 94dB/w/m best case. If you really need 96dB/w/m, you are going to have to make different plans.

Bob

Hi Bob,

thank you for your email and your reply here.

To make my problem a little bit clearer: I am not talking about the lack of deep bass here. As I said, even the male voice was sounding totally thin. I would very much like to understand if I made a mistake in my project, as I am quite new in that field. If the answer is "no, you did not make a mistake, you just took the wrong way" this is ok for me, and I will try something else, like a horn i.e.

The 300b SET I am building will have about 8-10 W. The listening room is large. about 60 square meters, 3.7 meters high ceiling, parquet-flooring etc. One of those typical european houses arround 1900.

I am listening mainly to classics and jazz. Sometimes I like to hear the original sound level.

Ideas?

Heinz
 
If you designed this thing using an Excel sheet, I'm not surprised it's not optimal. You need Martin King's MathCad worksheets for that. But as Bob says, 96db 1w/1m from a 206 in a TQWT? No chance. Maybe ~92db. And you'd loose more with a circuit too. The only way you're going near 96db is to horn load the things. In a room that size, it's the way forward anyway IMO with FR units.

As you find the Fostex boxes (which aren't even genuine horns anyway) a bit over complicated, if you can cope with the size, a BIB is easy enough to build. I know you're not a fan Bob (forgive me), but they perform way better than they simulate, and it's probably the only simple option out there. Have a look here: http://www.zillaspeak.com/bib-fostex.asp The plot looks ragged, but that's because it's a 1/2 space sim, and doesn't really account for the room's infulence. Over 300Hz, they're actually pretty flat. Below that point, the room dominates anyway, so nothing is really clear-cut. They shift a lot of air, and unlike most horns, they are not exactly lacking in bass.
 
Re: Re: Re: TQWT with Fostex FE206E

Morfeus said:
The 300b SET I am building will have about 8-10 W. The listening room is large. about 60 square meters, 3.7 meters high ceiling, parquet-flooring etc. One of those typical european houses arround 1900.

I am listening mainly to classics and jazz. Sometimes I like to hear the original sound level.

Greets!

Then you will need Lowthers (or similar) in large BLHs if only a single driver is used: http://www.passdiy.com/speakers.htm

'Live' dynamics has considerable peak SPL, with up to +30 dB of dynamic headroom available on some of the better recorded CDs.

GM
 
Re: Re: Re: TQWT with Fostex FE206E

Morfeus said:
[...To make my problem a little bit clearer: I am not talking about the lack of deep bass here. As I said, even the male voice was sounding totally thin....

What you describe is exactly the consequences of baffle step. Your speaker is unbalanced. You have done nothing to tame the rising response of the 206E and the output below say 300 Hz is reduced up to 6 dB by the baffle step. You need to do two things:

1. Put a series resistor on the driver, 2-3 ohms will do. This will flatten out the rising frequency response.

2. Install a BSC filter. For starters, try 3 mH || 6 ohm with a zobel of 6.8 uF -- 10 ohm. These are rough values, but will get you in the ball park.

Now you will have a balanced speaker that is not thin on the lows and not ear-bleeding on the highs.



...I would very much like to understand if I made a mistake in my project, as I am quite new in that field. If the answer is "no, you did not make a mistake, you just took the wrong way" this is ok for me, and I will try something else, like a horn i.e....

The mistake you made is using the wrong driver in the wrong application. You would have been much better off using the 207E with resonant cabinets like BR's and MLTL's. To make the 206E work requires serious compromises, particularly in the contour filter you simply have to have.


...The 300b SET I am building will have about 8-10 W. The listening room is large. about 60 square meters, 3.7 meters high ceiling, parquet-flooring etc. One of those typical european houses arround 1900.

I am listening mainly to classics and jazz. Sometimes I like to hear the original sound level....

Here is where the whole project is doomed from the beginning. You have a huge room by single driver standards. IMO, there is no way you will get concert levels from a single driver speaker except in the nearfield. Filling the room just isn't going to happen. If you want concert levels anywhere into the room and you are limited to 10 watts, you will need speakers with sensitivity well over 100 dB/w/m. That is serious horn territory and will be huge if you want any bass at all. The Fostex recommended back horn isn;t going to cut it.

Sorry to be so negative. Unfortunately, your requirements dictate a different approach.

Bob
 
Scottmoose said:
...I know you're not a fan Bob (forgive me), but they perform way better than they simulate, and it's probably the only simple option out there....


I'm not a fan of the BIB because it is contrary to my design philosophy: A single driver speaker with a balanced frequency response, a cut-off no higher than 40 Hz and sufficient WAF to be allowed in most living rooms. The approach that the room screws up the FR worse than the BIB does doesn't give me a warm fuzzy. Besides, a pair of BIB's won't fit my listening room.

I am amused that any driver can be fit into a BIB. Bring them on! It would seem to me that there is a sweet spot of driver parameters that would work best in a BIB. Perhaps you can help me here. I do have a passing interest in the BIB as a simple bass only corner horn. THIS seems to me to be a good application for the BIB.

Bob
 
Re: Re: Re: Re: TQWT with Fostex FE206E

Bob Brines said:
Here is where the whole project is doomed from the beginning. You have a huge room by single driver standards. IMO, there is no way you will get concert levels from a single driver speaker except in the nearfield. Filling the room just isn't going to happen. If you want concert levels anywhere into the room and you are limited to 10 watts, you will need speakers with sensitivity well over 100 dB/w/m. That is serious horn territory and will be huge if you want any bass at all. The Fostex recommended back horn isn;t going to cut it.

Sorry to be so negative. Unfortunately, your requirements dictate a different approach.

Hi Bob,

thank you so much for the explanations and no, that does not sound negative at all for me.

A horn seems the way to go, you're not the only one who was telling me this in the last two days.

Now, that is a completely new starting point for me. Looking at the measurements from the Fostex website the recommend horn looks not so bad:

176246025_082ba5d5cb_o.jpg


Why do you think it will not be ok for me? Other suggestions?

Greetings,
Heinz
 
Morfeus said:
Now, that is a completely new starting point for me. Looking at the measurements from the Fostex website the recommend horn looks not so bad:

176246025_082ba5d5cb_o.jpg


Why do you think it will not be ok for me? Other suggestions?
I think the Fostex-recommended would be cool. Another thing to look at would be the Dallas II. Plans and a couple photos of builds at:
http://fullrangedriver.com/gallery/thumbnails.php?album=3
 
I see a rising response in that graph. Nor does it get over 100db except in the peak. The Fostex horns aren't horns anyway, just an expanding cascade of 1/2 wave resonators. Some work quite well, I don't think the FE206E horn is one of their better examples though. You could try Onur's, that's a good 'un, but like most of this Big Vent Reflex type of horn design, it really prefers a higher Q driver. Adding series resitance will sort that, but lower the efficiency again. http://www.yildiz.edu.tr/~ilkorur/speaker/fostex_fe206e.htm

Nelson Pass' J-Lo could also be worth investigating. www.passdiy.com

Bob -I agree that BIB as a dedicated bass horn could be a really good aplication for these boxes. I think Dan's tried it to good effect, using his FE168ESigma BIBs to provide the LF, electronically crossed over to Visaton B200s on open baffles. I'd go for a driver with a Qt between, say 0.25 and 0.55. Fs between 30-50Hz. Moderate Vas is preferable -below 40L if possible, or the additional Vb required will cause the cabinet size to rocket.

Regards
Scott
 
Scottmoose said:
I see a rising response in that graph. Nor does it get over 100db except in the peak.
Both of which are consequences of the driver that you can't really avoid, at least with enclosure design. That rise in the response is in the infinite baffle freq response.

Ron Clarke has experimented with top-firing + a reflector, but his Dallas II design is merely direct radiating.

IME almost every full-ranger will sound best slightly off-axis, in the case of the FE206E perhaps moreso. (It is the case with my FE207E, although less noticeable after phaseplugging.)

IIRC http://www.boxen-baustelle.de/ has built almost all of the Fostex-recommended designs, fire him an e-mail if interested in getting his comments on the FE206E rearhorn.
 
Hi Heinz,

I also have Fostex FE 206 in the M.J.K. Project 5 (ML TL). Without BSC filter, it sounds terrible. Ear-piercing highs, no bass. Awful.

Besides the recommended BSC, you can also try the following:

Get a 220/12 v 50 w mains transformer. Wire a 20k (or even 10 K) pot across its primary (220v) and connect the speaker in series with transformer secondary (12v). You may try with a different transformer, this is just what I had and what I tried. You will loose efficency, but, in my opinion, FE 206 sounds much better this way.

On the other hand, I really started thinking about building a horn. Can't decide which one to build. :confused:
:bawling:

Regards,

Vix
 
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