[hubert]

DAVE, is it necessary to recess drivers on baffle?

[David Ellis]

Well,

I have never measured the impact of this with the 1801s, but Dennis did.  He said the impact was measurable and audible.  I believe he said the problem maker was the tweeter.  However, this was several years ago, and I am not 100% certain.

Sorry,

Dave

[hubert]

Hello Dave and all,

I have recently and simultaneously listen to PEM's 1801b and mine.
His drivers are flush-mounted, mine are not. His are stand-mounted, mine are floor-standed; It does exist a few differencys principaly in bass and sub-bass range    but the soundstages and image are perfectly the same on the two enclosures.
So,    audible impact about flush-mounting or not (at least in my relatively dead listening room).

   At the moment I'm a diet, so no beer

[Watson]

John Krutke's measurements are here:
http://www.zaphaudio.com/mtg-surface.html
Based on the measurements, he says:  "Surface mounting a normal 4" diameter tweeter is the worst thing you can do. A ragged lower treble response is guaranteed...."

Dennis Murphy measured similar results but his graphs are no longer online.

It doesn't make a lot of sense to me to spend $180 on tweeters and then install them in a sub-optimal manner (i.e. not flush mounted).  A 3/8 inch router rabetting bit is only about $22, and if you're really cheap, you can get by with just a standard router bit.

[hubert]

Watson,

Thanks for your reply and link to Zaphaudio measurements.
Obviously the problem is with the tweeter mounting, not with the woofer, at least with this relatively small Seas (as Dave guessed it).
When I said "no audible impact", I thought that surface mounting should affect only soundstages and/or image; in fact there were differencys in the upper-range transients, i.e. nicer attacks on ropes of guitars on PEM's 1801.
PEM uses the 8/15 ohms configuration (as he said to me, but I will mail with him today to be sure) and me the 7/12.5, so we get nearly the same electrical flow (0.2db or so isn't audible); I believed that the listening differencys came from the shadow of my bass and sub-bass which has quite more spl on my 1801.
I tried felt tips around the tweeter some months ago and founded no impact, but I listened only a few hours. So, I will try again.
 

[David Ellis]

I tried felt tips around the tweeter some months ago and founded no impact, but I listened only a few hours. So, I will try again.

For me... if I don't hear an impact in 5 minutes, I dissmiss the validity.  If I remain uncertain about the finding, I always get a second opinion.

Dave

[hubert]

Dave,

if I don't hear an impact in 5 minutes, I dismiss the validity...

Me too, problem is that I used self adhesive felt pastilles and I listened 60 minutes after having placed the pastilles. On PEM's 1801, the listening comparison was immediate.
So, to be sure, I will build a 4mm plywood baffle and listen to; if impact does exist, I will paint it and glue it on my present baffle.
But...I'm almost sure that the impact is more in the bass-range due to the stand-mounted vs floor-standed versions.
 

[hubert]

Dave,

if I don't hear an impact in 5 minutes, I dismiss the validity...

Me too, problem is that I used self adhesive felt pastilles and I listened 60 minutes after having placed the pastilles. On PEM's 1801, the listening comparison was immediate.
So, to be sure, I will build a 4mm plywood baffle and listen to; if impact  exists, I will paint and glue it on my present baffle.
But...I'm almost sure that the impact is more in the bass-range due to the stand-mounted vs floor-standed versions.
 

[Watson]

For me... if I don't hear an impact in 5 minutes, I dissmiss the validity.

Not to be critical, but this seems like a poor litmus test to me.  5 minutes is basically just one song.  It would be too easy to select a piece of music by chance that just doesn't highlight any of the differences.

Judging from John Krutke's measurements, the differences in tweeter mounting would probably be most audible with piccolo, harp, and violin music.  If anyone's planning on doing a 5 minute listening comparison, it would probably be wise to choose music that includes a significant performance by one of those instruments.

[David Ellis]

Not to be critical, but this seems like a poor litmus test to me. 5 minutes is basically just one song. It would be too easy to select a piece of music by chance that just doesn't highlight any of the differences.

Good point.  It's actually 3-4 pieces of music that cover female vocals, male vocals, strings, bass guitar, and drums.  I don't listen to the entire song until I am very close to getting things correct, or if I am uncertain about things being wrong.  

Dave

[hubert]

OK Doctor Watson   ,

You were right in pointing my mistake (laziness) about not to flush mount my drivers on my floorstanded 1801b.  
I have tried felt pastilles again around the two drivers and listened the result on well known cds. Obviously the character of the upper-range has changed; it is now in the same time softer and enlighted! softer because less dirty and harsh, and enlighted because it's as if I had obtained more spl from the top upper-range; in a few words, an accurater, truer and quieter   listening.

However, even with the flush-mounting, i.e. attacks of ropes of guitar are a little smoother than on PEM's standed version. So I have no other explanation than the kind of shadow made by my stronger bass-range.

 

[teiki arii]

Hello everyone,
I have listened the Ellis 1801b without flushmounted speakers for two months. Since pemo made the recess, corrected the filter scheme, and made some tuning, the sound is far better than that passed time. To tell you if recess is important, I can't truly or fairly tell you since three parameters have been changed...But they sound better than Hubert's, for sure..

[hubert]

Ahhhh, teiki arii,

corrected the filter scheme

To be precise: not corrected the sheme but improved the connection between the - binding post and the capacitor of the tweeter filter part.

...But they sound better than Hubert's, for sure..

For sure, certainly do you use some personal technologies to improve their performance... Make them known to our community please. We all are very impatient... teiki,

[teiki arii]

Ahhhh, teiki arii,

corrected the filter scheme

To be precise: not corrected the sheme but improved the connection between the - binding post and the capacitor of the tweeter filter part.

Yes right,
because lazy Hubert didn't make a good job! the scheme was not respected as Dave asked for...

And thanks very much again to pemo...

[David Ellis]

Gents,

So, are you basically conveying that flush mounting the woofer had a positive impact in a/b comparisons?

Dave

[hubert]

Dave,

are you basically conveying that flush mounting the woofer had a positive impact in a/b comparisons?

First of all take care on what could Teiki arii say about this matter: he is a real jumping FROGGY  

To be serious, I must say that I made comparisons between pem's standed version with the two drivers flushmounted and my floorstanded version with no driver flushmounted. As said previously, pem's version had a real superiority on upper-mid and trebble attacks and a less harsh sound.
Since I have glued felt around the tweeter and reduced the tweeter recess to get the same plan for the frames of the two drivers, I got a less harsh upper-mid and trebbles, and a subjective clearer top end.

But I cannot hear any difference with felt glued around the woofer.  (I let it in place but...)

What is astonishing is that I don't get the same (i.e.)strings attacks than pem's standed version, even with the flushmounting; I have much more subjective spl in the sub-bass range and just a little more spl in low-mid, even with the same internal volume of 22liters and slightly the same port height from the floor. I have no other explanation than the increased baffle vertical sizes (same width) and ...oh yes...certainly it's coupling with the floor. So, more sub-bass spl and/or sligtly more low-mid seem to create a kind of shadow on the upper range. I like my floorstanded version but I'm sure that adding a subwoofer to a standed version should be better.
 

[teiki arii]

Hi Hubert,
to be serious, would you remind me which "resistance combination" you use? The "8/15" one or the "8/12,5" one? Besides, pemo made the "port" longer than mine: it could explain the differences of Bass between our Ellis even if you and I have standfloor versions...
NB: as I thought my port too short, I made it a little longer -20% of one inch, so 5mm-, and it changed radically the balance between high and low frequencies: better equilibrated, Bass less "boomies" but with more details...Another 5mm more, and the Ellis lost Bass!!!
that's my two cents...

[hubert]

Ahhhhh Teiki arii...

Hi Hubert,
to be serious, would you remind me which "resistance combination" you use? The "8/15" one or the "8/12,5" one?

7/12.5 and you, if I remember: 8/15. So spl is equal, only a fraction of db difference.

Besides, pemo made the "port" longer than mine: it could explain the differences of Bass between our Ellis even if you and I have standfloor versions...

NO, I tried at least 5 or 6 different port lenghts, differences in the upper-mid and trebbles attacks remained tooooo obvious. Coupling with the floor on floorstanded version certainly is the explanation in the bass-range; it could be interesting you try to remove your present 9" closed stand and replace it with an open-air stand; I guess you will get a clear improvement in this matter.

as I thought my port too short, I made it a little longer -20% of one inch, so 5mm-, and it changed radically the balance between high and low frequencies: better equilibrated, Bass less "boomies" but with more details...Another 5mm more, and the Ellis lost Bass!!!

I said you are a jumping    and it happends
...or you have golden ears to be able to hear 1/5" port lenght difference  
 

[teiki arii]

...or you have golden ears to be able to hear 1/5" port lenght difference  

Well, I made the experiment with a pianist, a friend of mine, and two other listeners, the difference was quite obvious, unfortunatly for you. No need to have golden ears...

[hubert]

the difference was quite obvious, unfortunatly for you

    I run immediately to a oto-rhino-laryngologist