Updated 2641 Measurements

Kevin P · « **on:** 6 Aug 2005, 05:31 pm »

These are the measurement results from the final version of the 2641.

Things to note:

* The 2641 is a tower TMWW configuration.

* Dimensions 41" (H) x 8" (W) x 12.5" (D)

* Tuned to 30Hz with 3" dual flared port

* Ten component crossover! Holy smokes this worked out well. For comparison our KIT61 has eight components and it's a 2-way design.

* The crossover points are at 700Hz between woofer & midrange with about a 2nd-3rd order acoustic slope. The crossover between midrange and tweeter is at 3.5K with a 4th-5th order acoustic slope between them.

Here is the on axis response from 1.5M with 1/3 octave smoothing.

Here is the 15 degree off-axis measurement. One of our highest priority design goals is smooth off-axis performance. Not only does this give you a wider sweet-spot, but smooth off-axis performance provides an even spectral balance of reflected engergy from room reflections. What we hear is a combination of direct radiated sound and reflected sound. Having an even frequenency balance of both goes a long way to providing great in-room performance.

Notice this isn't much changed from the on-axis measurement. The top end starts to droop ever so slightly. This gives even coverage at a listening distance (12-14ft) across the span of a full size couch.

Here is the 30 degree measurement. We notice more top-end loss due to the beaming of the 1" dome tweeter. This is reflective of all 1" domes.

Notice that at crossover (3.5K) you have very little difference in comparison with the on-axis data. This is the area where you start to have cancelations off-axis with lower order crossover slopes . The comb filtering effects play havoc with off-axis response in low order crossovers. As a designer you have to choose what is most important to you.

Finally here is the impedance data. Nice and smooth with very little variance across the speakers bandwidth. Notice we are at a low of around 3.8 Ohms at 3K (tweeter/mid crossover). There is little musical energy up at 3K so this doesn't strain amplifiers. Our high outside of the normal double peak of a bass reflex box is 14 ohms at 800Hz, close to woofer/midrange crossover. Nominal impedance is 6-8 Ohms and this represents a VERY easy load for amps. Notice also the double peak at the bottom which roughly shows the port tuning frequency at 30Hz.

Kevin P · « **Reply #1 on:** 7 Aug 2005, 05:31 am »

Here are some prototype pics.

Here are the internals. Bracing such that we don't have muliple resonance nodes of the same frequency. Rigid fiberglass so we absorb internal acoustic energy.

Here is our secret formula. Speaker feet based upon engine mount technology to decouple the speaker from the floor.

Crossover on the rear for prototype work. Easy to modify and listen and the wife just loves all those wires and thingies on the back.

It's a bird, its a plane.... no, its a speaker way up in the air for some measurement fun.

kfr01 · « **Reply #2 on:** 7 Aug 2005, 03:29 pm »

Wow! Bravo, Exodus Audio / DiyCable. They look excellent.

I can't wait to build a pair. This tower is -exactly- what I am looking for as a front ht / stereo pair.

bald · « **Reply #3 on:** 7 Aug 2005, 08:49 pm »

Wow!

Two extremis, no stand needed, vertical TM alignment and........FRONT PORTED - I may have finally found a left and right channel for HT. If budget allows, end goal would be to pair them with the front ported LCR.

Is that 1" MDF?

Availability of plans and the PCBs and such?

And a question for Al if he's listening, still planning on CNC/magnet's for the 2641s? Availability?

very exciting.

bald

I spy the 1014 in the background there

RAW · « **Reply #4 on:** 7 Aug 2005, 08:58 pm »

2641 CNC baffles if enough interest I will do them if not no.
Need to get a few interested in them to make it worth while.
As it sits now we have CNC baffles and grills for the LCRs and have not sold a single one.

So I do not see the 2641 going any were

Kevin P · « **Reply #5 on:** 7 Aug 2005, 10:05 pm »

Quote from: bald

Wow!

Two extremis, no stand needed, vertical TM alignment and........FRONT PORTED - I may have finally found a left and right channel for HT. If budget allows, end goal would be to pair them with the front ported LCR.

Is that 1" MDF?

Nope... I only use 0.75" for all the designs. It's easier for people to source 0.75" and its more thn sufficient when braced properly.

If you wanted to go nuts on cabinet construction I'd encourage doing a constrained layer build rather than thicker MDF. Build a cabinet per the plans in MDF and then cover it with a layer of 1/4" rubber material. Build another MDF or Baltic Birch ply cabinet over that and you have overkill cabinet design.

Quote

Availability of plans and the PCBs and such?

The kit will be available without the PCBs first. It takes 3-4 weeks for our PCB source to deliver and I've not even started on the PCB design.

Kyle has been doing our cabinet drawings so I've got to see if he has time available to get these popped out.

I'm guessing we will put them on sale before Sept.

Quote

And a question for Al if he's listening, still planning on CNC/magnet's for the 2641s? Availability?

I'm not sure if we will do baffles or not. It's something that has it's upsides and downsides. People seem to want them but not want to pay for them. Funny how that works.

Al is sitting on a bunch of baffles for the LCR and 61 and I just don't see how they make economic sense.

From my experience kit builders are split into two camps. One don't care about the price and just want the finished product. They hire someone to build the cabinets and the baffles don't make a lick of difference to them.

The second class are the guys who have the tools and desire to build the entire speaker. This group often want to personalize the speaker and they do the quick calculation on how much it cost for them to cut the baffle (without figuring their labor) and their threshold for what they will spend on a baffle is low.

Just my observations.

Quote

I spy the 1014 in the background there

That is the box!

I'm using the preamp section of the 1014 and the Hypex modules to power them.

I hate to brag but these speakers kick some serious butt. They have dynamics out the wazoo and they just never sound stressed. I find myself playing them far too loud.

I'm itching to get my entire screen done and everything up and rolling.

Speaking of rolling I've got to go do some painting.

bald · « **Reply #6 on:** 7 Aug 2005, 11:07 pm »

Quote from: RAW

2641 CNC baffles if enough interest I will do them if not no.
Need to get a few interested in them to make it worth while.
As it sits now we have CNC baffles and grills for the LCRs and have not sold a single one.

So I do not see the 2641 going any were

This is too bad. I can appreciate the frustration of your situation. Kfr01 and I would be interested in baffles for the speakers we build, despite having the tools to do them ourselves. We're both quite busy, and having the baffle done (and more accurately) turns the cabinet construction into a weekend project for us novice mdf workers. I assume an order of 4 2641 baffles would not qualify as 'enough interest.'

If I can do some Enron-style accounting on my budget and spring for 2641s and an LCR, I may be your first (front ported version) LCR CNC customer then.

Quote from: Kevin P

I'm not sure if we will do baffles or not. It's something that has it's upsides and downsides. People seem to want them but not want to pay for them. Funny how that works. Al is sitting on a bunch of baffles for the LCR and 61 and I just don't see how they make economic sense.

Well, I appreciate your efforts to bring high quality parts to the DIY crowd, and bring quality wood-working pieces to those of us that are tool-impaired.

Looking forward to the drawings -

bald

Brian Bunge · « **Reply #7 on:** 9 Aug 2005, 08:07 pm »

Kevin,

Just thought I'd chime in and mention that I have 1" MDF readily available to me and could easily built some of these out of 1" if anyone was interested. Those are looking really good btw! You need to get Kyle busy on those cabinet plans as I'm sure I'll have someone wanting a pair soon.

Also, I sent you an email yesterday evening. Let me know if you didn't receive it.

Kevin P · « **Reply #8 on:** 9 Aug 2005, 08:43 pm »

Quote from: Brian Bunge

Kevin,

Just thought I'd chime in and mention that I have 1" MDF readily available to me and could easily built some of these out of 1" if anyone was interested. Those are looking really good btw! You need to get Kyle busy on those cabinet plans as I'm sure I'll have someone wanting a pair soon.

Also, I sent you an email yesterday evening. Let me know if you didn't receive it.

I'm not sure what is going on with the emails you send me but I didn't get this one either. Looked in the spam bucket and it wasn't there either. Resend if you get a chance to:

diycable.@olypen.com

kfr01 · « **Reply #9 on:** 11 Aug 2005, 04:26 pm »

Any word on cabinet drawings yet?

It would be nice to start on some cuts next week.

Brian Bunge · « **Reply #10 on:** 11 Aug 2005, 04:42 pm »

Kyle sent me cabinet drawings this morning but I'll wait for Kevin to look them over before posting the link. I think Kevin should give them the 'ok' first.

Kyle R. · « **Reply #11 on:** 11 Aug 2005, 06:24 pm »

Quote from: Brian Bunge

Kyle sent me cabinet drawings this morning but I'll wait for Kevin to look them over before posting the link. I think Kevin should give them the 'ok' first.

I've posted a PRELIMINARY drawing on my site so people can get an idea of what it will look like. Since this is preliminary I wouldnt build off of it yet as small changes will probably be made (heck, I've changed it since I sent Brian the link this morning). More than likely nothing critical will change but there is always the chance.

Brian Bunge · « **Reply #12 on:** 11 Aug 2005, 06:28 pm »

Which is precisely why I said I'd prefer for Kevin to give his blessing first! Based on the info. that Kevin sent me yesterday, I think I could build a pair of these even without your drawing. So there!

Kyle R. · « **Reply #13 on:** 11 Aug 2005, 06:29 pm »

I had to post again just so I wasnt a newbie with only 1 post

kfr01 · « **Reply #14 on:** 11 Aug 2005, 07:37 pm »

Looks pretty good. I predict that this will be one of Exodus Audio's best sellers. Front-ported and floor standing are huge plusses for me.

bald · « **Reply #15 on:** 12 Aug 2005, 02:51 am »

Quote from: kfr01

Any word on cabinet drawings yet?

It would be nice to start on some cuts next week.

Uh oh. Do I smell a few pairs of 2641's getting cooked up?

bald

RAW · « **Reply #16 on:** 12 Aug 2005, 03:56 am »

I guess so much for a 3/4" round over on those 2641.
Have to use some thin veneer to do a full wrap around a small radius.
Or square edge veneer

As the 8" width and the 7" cut out for the Extremis does not leave any room for the round over.

Not that it can not be done.Just limits veneer options.
Well if you have a veneer press its not a issue to bend around that small of radius.

I just had someone ask about the radius on some cabinets.And not till now did I see theclose edge to driver frame on the Extremis.

Brian
Going to use 3/8" round over and 10mm paper veneeer?

Brian Bunge · « **Reply #17 on:** 12 Aug 2005, 05:30 am »

You could get by with a 1/2" radius with 10-mil paperbacked veneer. It will bring the top edge of the roundover right to the edge of the recess for the Extremis'.

My new towers will be my first departure from the rounded vertical edges. They'll actually have 45 degree chamfers on the front and back vertical edges as well as the top edge of the front and back. I hope to have pics of them in a month or so. Too many other projects going on right now!

kfr01 · « **Reply #18 on:** 12 Aug 2005, 01:12 pm »

Quote from: bald

Uh oh. Do I smell a few pairs of 2641's getting cooked up?

bald

You do. I'll have more free time this coming week than I will for any time in the foreseeable future. May also buy that new full-ranger from CSS and make some computer speakers.

On the roundover issue ... Based on the above pictures I can see that the 2641s were designed and the crossover voiced without a roundover. Will a roundover negatively impact the sound?

Kyle R. · « **Reply #19 on:** 12 Aug 2005, 01:30 pm »

A roundover will not negatively impact the sound. In fact, you can make the enclosure slightly wider to accomodate a slightly larger roundover without negatively impacting the sound quality.