1801F

David Ellis · « **on:** 19 Jan 2004, 04:27 am »

This section of my forum will address all things related to the 1801F. While this is a viable option for the 1801 components, I don't plan to develop an ornate set of cabinet plans for this cabinet option. Also, I don't plan on selling any completed speakers of this version. There are several reasons for this. My initial post here will address the tertiary backround for the 1801F. As this portal devlops, I encourage anyone to ask me questions pertaining to this project - really.

I fully realized that many folks seemed to want a floorstanding speaker. I also liked the look of a slim floorstanding speaker. The ProAc D15 was quite striking IMO, so I decided to build an 1801 version for testing. My initial results were favorable, but by a VERY small margin.

The 1801F bass seemed slightly better. I can attribute this effect to 2 (yes, bad english) possible causes. Both of these causes encompass port location. The port faces backwards at the very bottom of the cabinet. First, the distance between the port and driver is greater. This makes cancellations outside the tuning frequency more "difficult" because the front wave and the back wave must travel further to cancel. Second, the port is at ground level. This makes floor coupling much better. The initial wave and reflected wave are very close. This should make the bass cleaner. The overall result was more seamless bass, but the diffence was VERY slight.

The 1801F midrange seemed slightly worse. The midrange just wasn't as clear. Images didn't seem to float on air like the heavier 1801B with my 60lb stands. I believe the primary reason for this was my relatively weak experimental cabinet. The baffle was thin I'll seguay slighty and explain MY basic construction.

All exterior panels are built from 3/4" MDF and there is 1 vertical brace connecting the sides/top/bottom. The external dimensions are 40" tall x 7 1/2" wide x 10" deep. The tweeter is offset 1/2" and the flange is about 3/8" down from the top of the cabinet.

The lighting for this picture isn't the best, but it provides a general idea of the layout.

Anyhow, the front baffle on MY 1801F speakers is only 3/4" thick. Since the cabients were only for "fun", I didn't make the baffle thicker. I believe the thinner baffle is the reason for the slightly smeared midrange. As such, I recommend anyone building the 1801F to use a thicker baffle and adjust the cabinet depth appropriately. While 3/4" thick material might be acceptable for many hifi speakers, I am not fully convinced 3/4" thick baffles are adequate.

Again, I must mention these audible differences between the 1801b and 1801F (also a b), were extremely slightl. Dennis Murphy, Gary Ganser and I had the change to compare these speakers in Bethesda in the spring of 2003. The midrange differences were not audible (me included), and Dennis remarked that the bass from the 1801b (stand mounted) had a little more punch. I agree with Dennis on his assessment about the bass, and there is good reason for this.

The cabinet tuning of the 1801F was slightly lean for Doc's room. Since the 1801F cabinet is larger, it should have a proportionally shorter port. I am confident that with a shorter port bass differences would be minimized too.

So, this is a very long explanation to convey that the audible differences between the 1801B and 1801F are VERY small or non-existent.

My next post will be slightly shorter and encompass baffle differences.

Dave

randog · « **Reply #1 on:** 19 Jan 2004, 05:35 am »

Dave, beautiful cabinets.

'Just for fun' I'd like to see you build a floorstander with a larger Seas driver. Or maybe an additional woofer.

Welcome back,
Randog

HChi · « **Reply #2 on:** 19 Jan 2004, 07:17 am »

Dave, these are truly nice looking. I had the opportunity and pleasure to audition your MTM prototype at Dennis place last year. That sounded really nice to me. I would guess the MTM vesion would sound better. With Dennis' know-how and genuineness in designing superb xovers, would there be a possibility to see the MTM floorstand getting fully developed? If MTM can sound better than this or even 1801b, I think it would be a great idea to take it up to the next notch. Just a thought!

David Ellis · « **Reply #3 on:** 19 Jan 2004, 02:53 pm »

I have very certain thoughts on those matters, but I'll address those topics in a different thread. Things will be better organized this way.

My comments here will address the baffle differences between the 1801B and 1801BF. I think this will be how I describe the floorstander from this point forward. Calling it an "1801BF" migh eliminate some confusion.

Initially I was VERY paranoid

about changing the baffle size of ANY speaker with the same crossover. I have recently learned that some changes are acceptable. I will first explain the issue of baffle step.

ALL drivers on ALL baffles incur baffle step. Baffle step is a 6db progressive loading on the driver. It effectively causes a driver that is 85db (based on T/S parameters) to be 91db as frequency rises. It generally starts around 200hz and is fully established by 1200hz. The size of the baffle effects when the baffle step begins and ends. It is a very serious issue. Failing to control baffle step results in a loudspeaker that sounds very thin due to frequency response imbalance. The upward slope of the response sounds forward and... ouch! Bigger baffles start&end their baffle step at lower hz, and smaller baffles start&end their baffle step at higher hz.

A crude way of understanding baffle step is comparing it to horn loading. The bottom end of a horns loading is determined by the size of the flange. The same is true with the baffle. The bottom end frequency of baffle loading is determined by the size of the baffle. Smaller baffles don't load very low. Larger baffles will load much lower.

Given the 1801B and 1801BF, I was very concerned the baffle loading would be an issue. It's not. I measured it & listened to it. The impact isn't present.

The other issue extant between the 1801B and 1801BF is the roundover at the edge of the baffle. The 1801BF has no roundover. It has sharp veneer edges. The impact is measurable, but not audible. Again, the impact is measurable, but not audible. The 1801BF has an on axis ripple round 8khz that swings + & - 3 db. This is very visible on the graph. This is quite striking to the eye, because most of the 1801 response varies about 1db - very flat. However, when the microphone is moved off axis just a scosh the ripple flattens. Hence, the impact of the sharp baffle edge is only present on axis.

On a personal note. I found this very interesting. It was very insightful, and laid to rest some marketing issues among many manufacurers concerning edge roundover. I often wondered how speakers like Dunlavy could sound decent with all of those sharp edges around the drivers. Surely the B&W nautilus midrange must have a very clear advantage. After some personal education with baffle edge diffraction effect I believe 2 things.

1. There is a positive aesthetic, measurable and theoretical impact of a nice baffle edge roundover.

2. It ain't audible.

Dave

jackman · « **Reply #4 on:** 19 Jan 2004, 03:39 pm »

Hi Dave,
Welcome back! It's good to read your common sense approach to audio. Also, the F design looks very nice. I have a question regarding floor standing speakers. Have you ever tried a QW design similar to Dennis' "Bob" speakers? I heard a pair and was impressed by the bass output. Do you plan to test a "Bob" design for people who don't have the room for a large 3-way?

THanks!

Jack

David Ellis · « **Reply #5 on:** 19 Jan 2004, 06:36 pm »

I have no plans to work on a TQWP version of the 1801.

And, sorry, we never chatted about this on the telephone.

Hearing the Veracity version of TQWP was enough for me. Sure it sounded a little better, but didn't have real bass.

When I consider building a speaker I consider several things.

1. Electronics Cost

2. Cabinet size/Aesthetics

3. Sound Quality

I then consider #1 and #2 after I ship the bugger. The net result is that a TQWP is a very bad move. It nets considerable cost, and very little gain for the end user.

I did some TQWP calculations. The cabinet you witnessed at the Iowa DIY was too small for the W18E001. The size must be 1xSD on the small closed end and 4xSD on the big open end. Getting the W18E001 into the right size cabinet requires about 62 liters. Plus, the cabinet must be strong enough to support the low bass without flexing. If the cabinet flexes, the bass will go right through the cabinet walls. This makes for a big heavy cabinet and 62 liters internally. Heck, at 70 liters I could use a L26 or W26 woofer and get real bass.

I understand your fixation with size. Size does matter. Going just a little bigger will net much more performance from a real woofer.

Dave

gotmikey · « **Reply #6 on:** 20 Jan 2004, 05:17 am »

Dave,

What's your finalized port length?

Al Garay · « **Reply #7 on:** 20 Jan 2004, 05:52 am »

Dave,

What insulation did you use on these? That does not look like Walmart's bed cushion foam.

Al

Al Garay · « **Reply #8 on:** 20 Jan 2004, 05:53 am »

In addition to the 1 1/5" baffle, would the midrange have improved with spikes on the bottom?

Al

David Ellis · « **Reply #9 on:** 20 Jan 2004, 01:15 pm »

Fair Questions guys. Thanks for asking them.

I continue to use the sandard length port . It's 1 7/8" diameter and 5 1/8" long.

The foam used is from Madisound. I think it's 7/8" thick. It was slightly thinner, and less obtrusive behind the driver. I thought it might work better but never a/b tested this against anything else. Past experience and testing revealed no difference between WalMart mattress cushion and flat acoustic foam.

I believe the thicker baffle would help the midrange of the 1801BF, but again... this difference is very small or not audible. I thought (?) that I heard something in my living room. However, it wasn't present at Dennis Murphy's home. Dennis couldn't hear it. I couldn't hear it. Gary couldn't hear it. Nonetheless, it might be present in some circumstances. As such, I recommend a thicker baffle for those who build the 1801BF.

I really can't comment on the spike issue. I didn't experiment with this and therefore have no first hand experience with this application. My comments would be theoretical and metaphysical only. Such disssertation is most often very long and convey's very little.

Dave

David Ellis · « **Reply #10 on:** 20 Jan 2004, 01:15 pm »

Fair Questions guys. Thanks for asking them.

I continue to use the sandard length port . It's 1 7/8" diameter and 5 1/8" long.

The foam used is from Madisound. I think it's 7/8" thick. It was slightly thinner, and less obtrusive behind the driver than mattress pad foam. I thought it might work better but never a/b tested this against anything else. Past experience and testing revealed no audible difference between WalMart mattress cushion and flat acoustic foam.

I believe the thicker baffle would help the midrange of the 1801BF, but again... this difference is very small or not audible. I thought (?) that I heard something in my living room. However, it wasn't present at Dennis Murphy's home. Dennis couldn't hear it. I couldn't hear it. Gary couldn't hear it. Nonetheless, it might be present in some circumstances. As such, I recommend a thicker baffle for those who build the 1801BF.

I really can't comment on the spike issue. I didn't experiment with this and therefore have no first hand experience with this application. My comments would be theoretical and metaphysical only. Such disssertation is most often very long and convey's very little.

Dave

David Ellis · « **Reply #11 on:** 15 Feb 2004, 06:02 pm »

This question was posted elsewhere and bears good validity herein:

Quote

What dimensions are 'finalized' for the 1801F version? I heard the volume isnt much larger than the 1801B, but it is probably 2x the height....so....less depth?

The external dimensions of the 1801F are again:

Quote

All exterior panels are built from 3/4" MDF and there is 1 vertical brace connecting the sides/top/bottom. The external dimensions are 40" tall x 7 1/2" wide x 10" deep. The tweeter is offset 1/2" and the flange is about 3/8" down from the top of the cabinet.

This assumes 3/4" material on the front & back of the speaker. I continue to think 3/4" thick MDF is fine for the back panel, but certainly the front panel could be 1 1/2" thick. This effectively makes the 1801F cabinet 10 3/4" deep.

salva · « **Reply #12 on:** 15 May 2004, 10:34 am »

OK, After having done one 1801b, I'm going now after a couple of 1801F's ...

While instructions are clear, I will like to see photos of any 1801F being assembled. So any picture of the process will be appreciated.

Salva

David Ellis · « **Reply #13 on:** 15 May 2004, 01:51 pm »

I didn't take any frame/assembly pictures.

Dave

Al Garay · « **Reply #14 on:** 15 May 2004, 11:49 pm »

Salva,

Why not wait until Dave releases the 1801b 3-way with the 10" driver?

I would like to build the SCC300 3-way since I have most of the drivers except for a pair of W18EX001.

Other alternatives, check the cabinet designs from Northcreekmusic.com. You can find excellent tips on cabinet designs by reading their cabinet instructions.

You can also post in the Madisound forum and ask for input on building a "Bob QWMLTL" like B. King made recently using Revelator 7" and Seas Millenium tweeter. It should work nicely with the 1801 drivers.

Al

salva · « **Reply #15 on:** 16 May 2004, 10:30 am »

Well.. this is why ...

I Did a couple of 1801b's for a friend, I wanted to see if I was able to do them, and if I liked them

Indeed l liked them, a lot.

Reason that I did them is because I intended them to be them the first step into my ultimate goal, design a 2 way thin floorstanding speaker that matched my furniture ...

Then I learned abt the 1801F. and that is what I'm now after...

I dont have space for other than the thin 1801F .... Perhaps a separate subwoofer, but not in the 1801F ...

By the way, I've posted the photos that Michel sent me of the manufacturing of 1801F's for all to see in my place ...

http://www.videoacustic.com/sferrairo/1801F/

Salva

salva · « **Reply #16 on:** 16 May 2004, 10:31 am »

Error, pls delete

David Ellis · « **Reply #17 on:** 16 May 2004, 12:54 pm »

I am not sure what you want deleted, but I cannot do this. Actually, I can't delete my posts. The only related possiblity is to edit the most recent post.

Also, the intenal 1801F pictures look good and right. Would you mind if I put them directly in this forum string? Other's may appreciate these pictures too.

Dave

salva · « **Reply #18 on:** 16 May 2004, 01:25 pm »

Yes, Indeed they are Michel's photos, I guess that will it be OK from him.

I meant that I doble post by mistake, that's why I asked the post itself that says "pls delete".

Salva

gotmikey · « **Reply #19 on:** 16 May 2004, 04:12 pm »

Yup, feel free to post them in the string, Dave. I have no clue on how to do this. If anyone wants a few more, I've got some.