HoldOuts: An All RS TMM 2.5-way

[jclin4]

Re: HoldOuts: An All RS TMM 2.5-way

Great build , I am a big fan of the drivers used in this project , I would seriously consider building these if they were an MTM design. Beautiful cabinetry skills!!

Thanks for the kind words! FYI, another member on this board cjd has an MTM design with the RS150's but using Seas tweeters:

http://www.divine-audio.com/abouriou/

I myself prefer 2.5-ways over MTM's for their vertical dispersion pattern. They also lend themselves to aligning tweeter and listening height, more so than MTMs in my experience.

[Mattcc22]

Re: HoldOuts: An All RS TMM 2.5-way

I like the look of the chamfer on the baffle. How big of a chamfer is that? I don't believe I saw that anywhere in the thread or pics.

[mzisserson]

Re: HoldOuts: An All RS TMM 2.5-way

I am unsure why ANYONE would want to change these. Still one of my favorite DIY speakers I have heard. The dip is barely noticeable but the huge image, and great off axis response was very engaging and comfortable to listen to without feeling like compromise was made. The sum of the Holdouts performance is greater than any "lacking" a squiggly line may show.

[Ryan]

Re: HoldOuts: An All RS TMM 2.5-way

Am I to assume that with 2 ohms of DC resistance in the woofer sections inductors alone that this would be considered a 6 ohm speaker?

[lamski]

Re: HoldOuts: An All RS TMM 2.5-way

Nice job on the build. They will definitely be on my list to consider when I decide to build a tower speaker. Any suggestions for a matching center channel for these for home theater use?

[jclin4]

Re: HoldOuts: An All RS TMM 2.5-way

Thanks guys for the great comments. Sorry I haven't seen the recent activity on this thread...I have just subscribed!

I like the look of the chamfer on the baffle. How big of a chamfer is that? I don't believe I saw that anywhere in the thread or pics.

The chamfer bit is 22.5 degrees, the only chamfer bit I own. My router has a 1/4" collet, and I have no issues working on 3/4" MDF or 18mm baltic birch.

Am I to assume that with 2 ohms of DC resistance in the woofer sections inductors alone that this would be considered a 6 ohm speaker?

No, more like 4 Ohm. If you look at the modeled impedance in post #44 above, the low point is in the 4-5kHz range. You would need to have an amp that can handle 4 Ohms.

Nice job on the build. They will definitely be on my list to consider when I decide to build a tower speaker. Any suggestions for a matching center channel for these for home theater use?

I assume you are thinking of an horizontal MTM. The closest I can think of would be the cjd's build which I linked in post #46. Same RS150's used as midwoofers, but a Seas tweeter instead. I haven't heard these myself but they get lots of raves.

If you are willing to go with RS180's for the center channel then there are many designs using either the RS28a or f-version. One I would definitely consider would be Jeff B.'s take:

http://techtalk.parts-express.com/showthread.php?223870-My-RS180-MTM-Design

[IBM5150]

Re: HoldOuts: An All RS TMM 2.5-way

Great looking design, kudos on the finish and low XO part count! Hope to build this soon but have a few questions.
Why did you use the 8 ohm versions and not the 4 ohm to end up with an overall 8 ohm design?

Entered the info provided above into Unibox - I must be doing something wrong. I cannot get to the low 30's Fs no matter what Fb I try, the lowest F3 I can get is 38 Hz with an Fb of 40 Hz. Changing the Fb up or down will increase the F3? It is OK to tune below driver Fs - when and why?


Unibox is telling me the peak cone excursion xmax will be exceeded at ~120 Hz, is this not correct or ??

It also seems the port air speed is exceeded between 22-49 Hz, again is this not an issue or ?


I have tried modeling some designs in Unibox and discarded them because the xmax or port airspeed has been exceeded but maybe they would be OK? Building some subs and testing with tones it showed Unibox was correct and I did hear port noise but with music it seems OK.......

You mention a flared port, can I assume it is flared on both ends and just not shown for illustration reasons?

Thanks in advance.

Eric

[jclin4]

Re: HoldOuts: An All RS TMM 2.5-way

Hi Eric, you bring up some interesting questions. I went back to verify my unibox calcs and the closest I can come is around 34 Hz. Not sure where I got the 30Hz figure:



But I think some of the differences are I modeled the old shielded version of the RS-150's and there might be some differences in T/S measurements, although reports are frequency response and impedance is pretty close to the current unshielded units.

The other factors could be I modeled on 52 liters internal volume and damping walls covered. Only the external end of the port is flared, not both ends.

Regarding your questions on port speed and potential for chuffing, in unibox are do you have nominal power at 40 W? In discussions I have had with other builders, I learned that modeling nominal power at manufacturer's rating is not always realistic, at least for my application which is music. In other words there really is a larger margin of safety than you would otherwise think. In the real world, I have not noticed any issue with the ports on the HoldOuts.

I hope this helps.

Cheers,
- John

[IBM5150]

Re: HoldOuts: An All RS TMM 2.5-way

That's great John, thanks for the reply. Trying to look designs and figure out how it works so maybe I could come up with my own design using software tools is quite a challenge - especially when it doesn't come out right.

When I do the build am sure it will sound great but I don't have your skills on making anything so attractive.

Will also post my subwoofer projects and data and see what the rest have to say about the Unibox data and if it is valid or not.

Thanks again.

Eric

[Wolf]

Re: HoldOuts: An All RS TMM 2.5-way

I usually model for a worse-case scenario where the output equals 100dB if possible. This rarely takes all of the nominal power handling. 95dB at the least.

The reason for the 8 ohm units is to get the 2.5-way alignment to augment for full BSC, when placed in parallel in the bass range below the BS Fc.

While you can do a series wired 2.5-way, it takes twice the amount of parts, and you don't gain the same way for BSC augmentation.

Later,
Wolf

[IBM5150]

Re: HoldOuts: An All RS TMM 2.5-way

Hi Eric, you bring up some interesting questions. I went back to verify my unibox calcs and the closest I can come is around 34 Hz. Not sure where I got the 30Hz figure:

[ATTACH=CONFIG]42014[/ATTACH]

But I think some of the differences are I modeled the old shielded version of the RS-150's and there might be some differences in T/S measurements, although reports are frequency response and impedance is pretty close to the current unshielded units.

The other factors could be I modeled on 52 liters internal volume and damping walls covered. Only the external end of the port is flared, not both ends.

Regarding your questions on port speed and potential for chuffing, in unibox are do you have nominal power at 40 W? In discussions I have had with other builders, I learned that modeling nominal power at manufacturer's rating is not always realistic, at least for my application which is music. In other words there really is a larger margin of safety than you would otherwise think. In the real world, I have not noticed any issue with the ports on the HoldOuts.

I hope this helps.

Cheers,
- John

Re: low frequency response, the specific Hz number really doesn't matter since I am using a sub, I really wanted to know why I couldn't get it to model right. My box is 40L with walls covered and if I can get a flat response to 40 Hz that is fine. 40 Hz is great for a 5-1/4" driver.....

Re: Port flare, why the flare on one end, fitment in the box issue? Again I don't doubt it works but I usually buy the Precision Port kits and use the inside flare.

Re: Port speed graph, yes I used 40 W as nominal power in Unibox. Not surprised it is OK as 3" certainly seems more than adequate but have you tried it with test tones? The sub I designed with a 10" RSS265HF-04 and a 4" flared port which you would think is more than adequate for a 10" DOES make port noise with test tones at 25 and 31.5 Hz matching the Unibox model but with music I have not noticed a problem, or is it? Will post project & graphs today for review.

Re: Graph of cone excursion, this one is most worrisome to me, but if you say it's a non-issue I believe it. Trouble is when I modeled my own design it made me stop dead in my tracks for concerns of doing all the work and then having an unusable project in the end from cone bottoming. Is there a general rule, calculation, or tool to use to preventing overexcursion if not Unibox?

Thanks again for your reply.

Eric

[IBM5150]

Re: HoldOuts: An All RS TMM 2.5-way

I usually model for a worse-case scenario where the output equals 100dB if possible. This rarely takes all of the nominal power handling. 95dB at the least.

The reason for the 8 ohm units is to get the 2.5-way alignment to augment for full BSC, when placed in parallel in the bass range below the BS Fc.

While you can do a series wired 2.5-way, it takes twice the amount of parts, and you don't gain the same way for BSC augmentation.

Later,
Wolf

Wolf: Are you suggesting I lower the nominal power in Unibox to get 100 dB of output and then review the graphs? When I lowered the nominal power to 5 watts to achieve 100 dB, everything looks gold.


Re: BSC, I have read a little don't have a good handle on designing and implementing, but I knew there had to be a reason for using the two 8 ohm drivers. I see the inductor added to the 2nd woofer, and less parts, well I am all for that. Now will my amp handle it........

Thanks!

Eric

[Wolf]

Re: HoldOuts: An All RS TMM 2.5-way

Wolf: Are you suggesting I lower the nominal power in Unibox to get 100 dB of output and then review the graphs? When I lowered the nominal power to 5 watts to achieve 100 dB, everything looks gold.
[ATTACH=CONFIG]42021[/ATTACH][ATTACH=CONFIG]42022[/ATTACH][ATTACH=CONFIG]42023[/ATTACH]

Re: BSC, I have read a little don't have a good handle on designing and implementing, but I knew there had to be a reason for using the two 8 ohm drivers. I see the inductor added to the 2nd woofer, and less parts, well I am all for that. Now will my amp handle it........

Thanks!

Eric

Yep your model looks better. 100dB is VERY loud, so I use that as a benchmark instead of power capability.
Later,
Wolf