ISO Mid-Bass for Econo-Waveguide

[NEO Dan]

I know this is not the HTG brand of HiFi but for me and my intended use as HT satellites, there seems to be several positives to going this route:

• Huge sweetspot, like 6' wide. I run a modest FP setup and center channel is NOT happening, as I find it very distracting.

• Can be high sensitivity with the "right" midbass, that's why I'm here. :B

• Can handle the dynamics of reference + dB playback levels, and yes I admit it sometimes I break out the earmuffs and JAM.

So I wanna take a shot at these and I'm wondering if anyone else has found a woofer with a complementary polar response?
Earl Geddes posted this EQ'd polar:



There are 4 possible JBL PT WG's that have my curiosity:
12" W x 6.5" H, 90 x 50, screw on, JBL part #338800-001 $10
~6" x 6" 90 x 90, PT-B99HF-1 JBL part # 364914-001 $6
~8" x 8" 90 x 50, PTWG JBL part# 364700-001



~12"W x 10"H, 70 x 70, screw on, JBL Part # 354267-001, used in MRX500 series with the JBL 2408H equivalent to the BMS 4540ND that I want to try






Links:

http://www.jblproservice.com/index.html

http://www.jblpro.com/catalog/general/technicallibrary.aspx

[NEO Dan]

reserved for expansion

[ch83575]

Are you going to buy one of Dr. Geddes' waveguides? I am pretty sure he sells them separate from his designed systems for DIYers. If you are the woofers you are looking at seem rather out of line with the total cost of the project. If you are not buying a waveguide how are you planning on achieving the CD polars for the upper frequencies? ie. are you going to use a compression driver / horn like Geddes, a dome / waveguide or other?

-Chad

[kevinp.]

Are you going to buy one of Dr. Geddes' waveguides? I am pretty sure he sells them separate from his designed systems for DIYers. If you are the woofers you are looking at seem rather out of line with the total cost of the project. If you are not buying a waveguide how are you planning on achieving the CD polars for the upper frequencies? ie. are you going to use a compression driver / horn like Geddes, a dome / waveguide or other?

-Chad

what did i miss? How do you know what woofers he is looking at?

[JonMarsh]

Polar response for woofers is limited by the physical size of the driver- in this case you'd need a midwoofer that can cross at a fairly high frequency, with high sensitivity- but these are really "midranges", midwoofers. Something like the 18Sound 6ND430-16 might do the trick.





OTOH, being of a more conventional outlook, I'd be more inclined to go with a Seas ER18RNX, which has the T/S parameters to support a real bottom end, including Xmax of 6 mm, and is surprisingly close in sensitivity. But it doesn't have the power handling of the pro driver.

[ch83575]

what did i miss? How do you know what woofers he is looking at?

Just ignore me... I am an idiot. I thought the list of horns was a list of possible drivers.

[NEO Dan]

John,
possibly a 2.5way MTM configuration? I have been looking at that 18 Sound driver over at Zaphs, I'm not thrilled at the ascetic, but then again the look at the WG's. The 6"sq version of the WG could make for an amazingly potent yet compact package.

Would using the larger WG allow for a larger more efficient midbass?

[kevinp.]

How low are you looking to go?

[JonMarsh]

And how efficient are you looking for? Hoffman's iron law will set your limits. A 2.5 way with ER18NX could do ~90 dB with moderate BSC. If a wall build in, with no BSC, about 94 dB/2.83VRMS. You can find many higher efficiency drivers, but with much larger enclosure size requirements, and not with wide polar response at 1.5-2 kHz.

[kevinp.]

Could go with something like an Eminence Alpha 6 @ 94 db spl, .5 cu ft box, hi pass at 80hz and be able to break 110db without reaching xmax. And that's just one driver...

[NEO Dan]

The LF requirement for me would be a rising response to start a house curve, IMO nobody runs subs flat in a HT setup. I'm not looking to turn Dianna Krall into a chain smoking tranny here, but I need to be able to configure it to be on the rise for the transition to the subs. I would design for use with an 80Hz HPF, but personally I go with 120Hz because I run subs up front and I like to keep the cone motion in check on the midbass. On a whim last Labor Day I bought some cheap'o PR12's to experiment with, because I had really become annoyed with my B&W's lack of dynamic capability, they deliver, but boy do the highs suck. With the highpass in the AVR @120Hz the excursion is under 2mm p-p. For what they are, I've got no complaints. I want the HiFi sound back while retaining the dynamics of the PA speakers. I had hoped for sensitivity above mid 90's @ 2.83v, but that's not a total deal breaker. Big cone motion in the midbass however, I want to avoid that, hence asking about larger drivers.

[Saurav]

I think Geddes uses a 10" woofer with his 10" WG, a 12" woofer with his 12" WG, etc. - for matching woofer directivity to WG. I read another comment somewhere saying a good starting point for woofer size was Sd == WG mouth area. To me, the problem becomes one of budget - a 12" woofer that'll play cleanly up to a 1.5kHz crossover is going to be a pretty expensive woofer.

I went in the other direction - a 6.5" midrange crossed to a 4"x4" WG. Of course, this has its own problems, the biggest one being that the crossover is now an octave higher (2.5kHz), right in the middle of where most people say you don't want a crossover to be.

One more comment based on my experiences with trying to mate a WG to a midrange - keep an eye on acoustic centers. A larger driver will have a deeper acoustic center, which will help with crossing over to a deeper/larger WG. My first attempt was with a 6.5" midrange and a 10"x8" WG, the impulse responses showed the tweeter AC was 4"+ behind the midrange, and I simply could not get the phase to line up through the crossover region. Someone with better crossover skills will probably be able to solve that problem, but I gave up and went with a shallower WG.

[Dennis H]

Dan, do you know which compression driver Earl was using for those measurements? The LF cutoff seems a bit high for a 12" waveguide. Most measurements I've seen of waveguides that big cut off at or below 1K which would give you a lot more flexibility picking a pro 10" or 12" to mate to it. As far as which pro midwoofer, the TD1?M series would be a no brainer except for the price.

Paul W's 0 and 45 degree measurements of a BMS 4552 on a cheap 12" waveguide similar to the Dayton.

[ThomasW]

I think Geddes uses a 10" woofer with his 10" WG, a 12" woofer with his 12" WG, etc. - for matching woofer directivity to WG. I read another comment somewhere saying a good starting point for woofer size was Sd == WG mouth area. To me, the problem becomes one of budget - a 12" woofer that'll play cleanly up to a 1.5kHz crossover is going to be a pretty expensive woofer.

Lot's of big drivers will play higher frequencies. Problem is they're beaming like mad at those frequencies.

Some kind of MTM using JohnJ's 10"s with the phase plug maybe the best compromise. I have no idea what their polar plots look like....

[ThomasW]

Dan, do you know which compression driver Earl was using for those measurements?

All Earl's existing systems use the B&C DE250. I think he used the screw-on Selenium to test the JBL Econo-WG

[Saurav]

Lot's of big drivers will play higher frequencies. Problem is they're beaming like mad at those frequencies.

Well, as I understood it, Geddes picked those driver sizes because he gets the "right amount of beaming" at the crossover frequency, i.e. the woofer's directivity matches the waveguide. I think he uses B&C woofers in his speakers, but I could be wrong.

[ThomasW]

Correct, Earl uses the 'beaming' and he uses B&C woofers.

Dan is asking for big drivers that don't beam at higher frequencies. That's a physical impossibility.

[Dennis H]

All Earl's existing systems use the B&C DE250. I think he used the screw-on Selenium to test the JBL Econo-WG

Ah, that might explain it. As I recall, that Selenium has a pretty high Fs.

[NEO Dan]

Dennis,
I dunno on the driver, but the 12" x 6" WG is available in both bolt on and screw on versions, I'll see if I can find the other part number.

Saurav,
the "right amount" would be my line of thought, thanks Saurav

Thomas,
I'm willing to go with with a 2.5way to get the SD I'm after and still make a good match in the directivity department.

[Saurav]

Saurav,
the "right amount" would be my line of thought, thanks Saurav

Well, you mentioned you wanted a wide sweet spot, I think that's where Tom (and others) concluded that you wanted wide dispersion. Geddes' design philosophy (to the extent that I understand it) goes for narrow dispersion.

[JoshK]

I find it odd that you conclude due to the narrow directivity (90º really isn't that narrow) that the sweet spot wouldn't be wide. I found Geddes' set up to have a much wider sweet spot then my Modula MTMs by comparison. One of the points of constant directivity is the uniform coverage over the entire listening seating.

[Saurav]

I stand corrected. I was going off something I remembered reading where he explicitly said he didn't want wide directivity, but you're right, that doesn't automatically mean a narrow sweet spot.

A large driver that narrows to 90 degree coverage by the crossover frequency might meet Dan's goals.

[NEO Dan]

I'm looking for something that complements the WG's polar response.
As for My current theory... even the 70 x 70 WG should be more than wide enough for domestic use, and it would probably be preferred in situations where the sidewalls are close by.

I was looking at the pricing and the JBL 2408H is ~$20 < the BMS. The JBL is also available in 16Ω

[Dennis H]

I don't think the directivity is a big problem for a 6' wide sweet spot. If the listening distance is 10', that's only +/- 17 degrees. The thing is, to match directivity like Geddes does, you kinda have to come at it backwards and decide the woofer diameter from how low you can cross the tweeter and that depends on the horn/compression driver combo. Lower cross, bigger diameter woofer.

FWIW, I heard that JBL OEMs some of their high end compression drivers from BMS. The only difference is it says JBL on it and it costs twice as much.

[NEO Dan]

Wider is better, if you could get a whole sectional couch load of people a stable phantom center image + dynamics + no horn glare= :B

I read that JBL buys the diaphragm for the 2408H from BMS even thought they bought a license to make them. It would be nice to source all the drivers from JBL but I don't know a thing about there <10". Actually that's not true, I know almost nothing about JBL drivers, all of them that is :B

[Dennis H]

Any idea what the LF cutoff is with the 2408H on a 12" horn? Hopefully it's low enough that you could use a 10" or 12" woofer. JBL woofers in that size range cost as much or more than the TDs from AE and the TDs are better drivers for crossing high.

[ThomasW]

Maybe you should just buy a pair of Yorkville U-15"s.....

[NEO Dan]

I posed the Unity as an alternative to the SH100 for someone the other day on AVS. Do you think the Unity is capable of the presentation, I'm tired of being the olny one with a good seat. I think everyone should get to enjoy.

It would be nice if there were a documented low cost build to come out of this somewhere down the road as I know of lots of folks who build my sub designs and then are left short by the remaining speakers in there HT setups.

[NEO Dan]

Any idea what the LF cutoff is with the 2408H on a 12" horn? Hopefully it's low enough that you could use a 10" or 12" woofer. JBL woofers in that size range cost as much or more than the TDs from AE and the TDs are better drivers for crossing high.

JBL specs the x-over at 1.7k with this horn:



JBL is even nice with the data on there products, including crossover component data.
Link to Data Pricing & TSP's Lots of PDF's in here

http://www.jblproservice.com/index.html

http://www.jblpro.com/catalog/general/technicallibrary.aspx

[Dennis H]

That's a pretty high crossover.... Okay, I read your first post again. "~12"W x 10"H, 70 x 70, screw on, JBL Part # 354267-001, used in MRX500 series with the JBL 2408H equivalent to the BMS 4540ND that I want to try." The BMS 4540 is a high resonance driver which can't really play low enough for a big 2-way. You need the 4552 which can cross much lower. And you really want a bolt-on waveguide, not a screw-on. The screw-ons have a straight 1" diameter section, 1/2" or more long. If you're going by the Geddes OS formula, by the time you get 1/2" out, it should be about 1.4" wide for a 90 degree waveguide.

Sorry if I'm trying to make you spend more money. I just can't see cheaping out on the drivers when it's so much work to build a speaker. And if you limit the frequency response too much, you'll end up needing a 3-way to get your dynamics which will cost more anyway. Me, I'd get a BMS 4552, a bolt-on waveguide and a TD10M or TD12M. John J. has already proven that combo for pro sound using the 18sound waveguide.

[augerpro]

Do you buy these parts directly from JBL? IS there a link to pics of all these horns or other specs?

[ThomasW]

People having the original Unity are pleased and it has some issues. The redesigned 3 driver mid section is supposed to be quite good and IIRC the fully assembled U-15 costs less than the original Lambda kit.

There's no problem making a low cost high output speaker. The problem is doing one with a wide dispersion, high output, and low cost.

[ThomasW]

Do you buy these parts directly from JBL? IS there a link to pics of all these horns or other specs?

http://www.jblproservice.com/parts.html

http://www.jblproservice.com/navigation/pdf_nav_parts%20lists.html

[NEO Dan]

I did quite a lot of searching tonight and I want to scale things back to reality so I actually get to build sometime this millenium.

I think it's prudent to investigate the EWG setup in the following manner:
I should buy all three versions of the horns for testing and either a matching pair of 2408's or one each of 8Ω and 16Ω. And a pair of the Selenium D220Ti drivers that are the current spec for the project to set the base line and see how bad the sparkle of the titanium is.

Looks sparkley



and the 2408, "clearly" better IMO

[penngray]

Dan, I will be following this project! Hoping that you have great success since I will be doing a similar project in the future (its delayed right now).


I would love to see something similar to Geddes performance at a fraction of the cost of one off his kits. I know its probably impossible but who knows.

[CraigJ]

Dan,

Your probably already know this, but Dr. Geddes is also using a B&C DE10 compression driver in his smaller Harper speaker. As usual, excellent advice from Dennis regarding the BMS drivers. Dennis's advice mirrors my experience with the DDS waveguide using the 4540ND and 4552. Also, the higher you cross, the more center-to-center driver spacing becomes an issue, especially with a big waveguide. FWIW, I second the vote to check PaulW's work using the Dayton 12" waveguide.

Craig

[kevinp.]

who is PaulW and what work are you referring to?

[CraigJ]

Who is Paul W.? ;x(



Some info here:

https://www.htguide.com/forum/showthread.php?p=392802#post392802

and here:

https://www.htguide.com/forum/showthread.php?p=329361#post329361

Enjoy.

Craig

[kevinp.]

awesome, thanks!

[NEO Dan]

Great moogly googly that's a lotta $,$$$

***
I dunno about that DE10, it's an inverted 1" dome:



And this whole OS WG thing has me thinking that to truly have the recepie correct you need a driver that probably doesn't exist. Probably should be a like a BMS to make a planar wave but the WG taper should extend deep into the driver... probably something along the lines of a 4540nd but 1.4" exit and bolt on. Of course the 4555 already is this configuration but it would probably need a 2" exit to fit the curve... Oh well.

This brings me back to the EWG. Now I have no illusions that it's upper echelon material, but I do interpret what I've read so far to = really good for what it is. That is good enough for me at this point in time to buy the WG's and 220Ti's and a couple midbass drivers for investigation.

[Saurav]

The DE10 also needs a ~2.5kHz XO, so I would think you'd have to do a 3-way, I don't see how you'd get a 2-way woofer to go up that high.

FWIW, Zaph tested the DE10 on the ME10 horn, so you'll find some data on his site:

http://zaphaudio.com/tidbits/

[Dennis H]

Hey Dan,

I sorta missed the 'econo' part of your thread title. Sorry about that. Eminence has a lot of good bang for the buck pro woofers. Naturally, we like to support our sponsor PE by clicking their banner at the top of the page when looking for Eminence stuff.

[ThomasW]

Chasw98 and I each have a pair of the JBL econo-wave guides. He has the Selenium 220ti drivers on order, I'm going to try my EWGs with a spare pair of BMS 4540's.

I don't have any metal diaphragm compression drivers. I have the 4540ND and B&C DC250's, both of those have a sonic signature similar to a soft dome tweeter provided it's not messed up by horn colorations.

I've been experimenting with different WG's and horns. I'll post about them when I finish the comparisons.

[NEO Dan]

That's good to hear, do you want any of the other JBL PT WG's or a 220Ti to test? Truthfully I also PM'd Brandon with the same offer as I don't have confidence in my measurements that I would rely on or publish. I've done my fair share of useful "investigating" with REW and the ECM8000, but I am an amateur I would have started with the EWG and stock crossover/driver combo measurements and progressed from there... SLOWLY :B

So what are you guys cooking up for the EWG's? 3-way? Is this for the DIY realm or commercial? Do tell...

I've own SoundEasy for a couple years now and I'll admit it... I've never actually measured anything with it I know I need a new sound card, I hurt my USB Mobile Pre measuring an amp

If you projects are gong on Mission Accomplished let me know if you want Sketchup renders and cut sheets for the projects.

[augerpro]

RCF had a decent horn that I always thought looked good, better than a lot of the cheap JBL stuff and really popular. It was the H100. Usspeaker used to carry it but now it's gone. The PAudio PH 220 looks exactly like it though, and aluminum, which I always liked better than the thin plastic the cheap stuff is made from. Probably needs some dampening but at least it is strong and stiff enough to function as part of the baffle.

But that one JBL you posted a pic of looks interesting, I'll have to dig for some pics of the other stuff, maybe there is something more akin to a smooth WG then what Iv'e seen from them so far.