not the right question

[Sdiver2489]

Please refer to The topic RS180 and DMS30 MT project. You can delete or lock this thread.

Sorry about the mistake I made in my previous post. I feel so dumb. Hope I didn't blow my reputation on my first post on these forums . I appreciate the kind responses though.

[cjd]

You can not arbitrarily change components in a design as important as drivers without understanding that the crossover will almost always be differerent. Under no circumstance can you use a crossover designed for two woofers and only use one and have it sound good. Trust me - I had a wire come loose on mine recently and it was running this way. Very harsh.

Your project has no relation at all to the Modula. You will certainly be able to get sound. It may even sound OK. Maybe. For a while anyhow.

My first four or five crossover attempts were all miserable failures, and at this point I consider the one I settled on to be only tolerable. And they weren't using drivers as complex to work with as the RS series. It's been a long road with much learning since then.

If you aren't up to a long road with lots of reading, re-reading, complex math, and other crazy stuff, pick a project and stick to the plans. 100%.

Otherwise, you can certainly get the RS180 and MDT-30 to work together. You can cross at 1800Hz. It may not be optimal, but it will work. And I'm not entirely sure who to believe when it comes to what's "too high" and all that. If you're embarking on that journey, have fun, have patience, and don't be afraid to ask questions.

C

[JonMarsh]

I didn't ask if I should follow the plans. I asked if he thought it would work. I am not making an MTM and I am not using the seas tweeter unless someone gives a reason to. The purpose of this project is not to see if I can follow directions, its to challenge myself to apply a bit of what I have learned in college while having fund with it too. So please, just try and help me out, will it work?

For clarity's sake, you should start your own thread with that topic, and explain your goals; don't post it on a sticky thread started for a another project. We're pretty loose on forum etiquette here, but some times it's necessary for clarity of communication.

I did post a pretty complete reply on that thread, though, which you may find helpful, with a discussion of the RS180 characteristics as well the tweeters. I'll copy that post to this thread for your review, too.

Best regards,

Jon

[JonMarsh]

Quote:
Originally Posted by Sdiver2489
I am trying to do my first speaker project and I had decided on a RS180 and Morel DST-30 combo. Do you think I could let the RS180 go up to a 1800 crossover point with a 4th order linkwitz riley. At this point, the tweeter would have reached the end of its rollup to its max SPL. It may not be perfect but do you think it might work?


Are you talking about the Morel MDT-30 tweeter? I'm not familiar with a DST-30 Morel tweeter. Vifa has a DST line, but obviously not the same thing.

OK, first, with regards to the RS180, I investigated it's behavior in some detail, especially linear distortion effects stemming from sub breakup cone energy storage effects, and my conclusion was that the only way to get close to the optimum performance from this driver was a steep LR-8 equivalent crossover in the 1200-1400 Hz range. This is because by 1800 Hz there is some substantial energy storage and time smear coming from the cone, which is quite evident in cosine shaped sine burst testing at that frequency and above. The ONLY two 7" driver's I've seen with decent ETC plots (Energy Time Curve) at 1800 Hz are the Peerless 850439 (which is pretty good), and the Seas W18, which is excellent performing. Other's have ignored this point in RS180 designs, like Monte Kay's initial dipole design using the RS180's and RS270's, and come to regret it because of how it sounds with things like female vocals- he went back and changed the crossover design.

So, no, I don't recommend going higher in crossover frequency with a shallower slope. It will play music, but you may not like the results, depending on how good your ears are.

OK, so I'm a bit pickier than average, especially being an ex professional musician, and also having done live recording and helped design and build a couple of small studios. But NOTHING you can do to the upstream source and electronics can improve the sound if you use a driver outside it's linear range- in either frequency or dynamics- you'll just have to live with the grunge, grit, or honk which results. I prefer not to.

Regarding the Morel MDT30, it has a pretty nice reputation in the DIY community, but I've never completely understood why. It's down about 7 dB at 1 kHz compared wtih 2 kHz; it's ferrofluid damped; the true mechanical resonance is at about 1200, so it's not a good candidate for a 1400 Hz crossover. It has a slight peak at about 16-18 kHz, then rolls off on axis above that, being down about 5 dB at 25 kHz, and 10 dB at 30 kHz. Yet their brochure calls it a "fast" tweeter. Of axis is about what you'd expect for a 1" dome.

In comparison, the Seas 27TDFC is at about the same level at 30 kHz as it is at 5 kHz, and it's 30 degrees off axis behavior is better than many 1" domes on axis. Addtionally, it will handle "punishing" levels of low frequencies, exhbiting distortion with a 1 kHz centered cluster (1 kHz 50%, 900 Hz 25%, 1100 Hz 25%) at distortion levels similar to the Millenium Excel. In my opinion it's one of the best $28 tweeters available. I just don't see the Morel as being in the same class, especially not for twice the money.

But don't let me deter you from building a project the way you want to, and seeing how it works out. This isn't religion, you know, it's just DIY audio.

We're just trying to save you a little money and grief in getting good results. But then some things are best learned by one's own experience... I've pulled more than a few boners over some 35 years of speaker building.

~Jon

[Sdiver2489]

Whoops sorry guys, somehow instead of replying to a thread I was in I managed to post a completely new one! Sorry about that, didn't mean to I swear. you can close this thread if you want as I didn't mean to make it a completely seperate one. Sorry about this!
Whoops it doesn't look like I can change the title, I will post the changes as a new thread. Someone can delete this one or lock it. ops: ops: ops:

[ThomasW]

Okay it's better that you accidentally started a new thread. That way you can get answers to your specific project.

[Teran]

Ryan,
Speaker building is about compromise. Some people accept more/different compromises than others.

Some people grab a couple of buyout drivers, add a fairly textbook crossover, get a decent FR, and call it done. Others, like Jon, go the distance. In either case, the resulting speaker will usually outperform a comparably priced commercial speaker. Jon's designs will compete against speakers costing several thousands of dollars.

Where you end up with your own design will depend on what compromises you accept and how long you are willing to work on the project. Is it going to be a 201 Lab Project, a Master's Thesis, or a Doctoral Disertation? Expect to put in the appropriate amount of work for the level you shoot for.

Also, different boards will have people of different levels of experience, philosophies, and acceptable compromises.

Instead of popping from board to board, why don’t you pick one that has the level of people/compromise you are shooting for, post your goals and requirements, and let them help you reach your goals?

My $.02.

Yeah, I read this board, too. :B

[Sdiver2489]

very true. It seems like whenever I read another post I see something else that worries me. In this case its John saying crossing should happen at 1400 or lower. All of a sudden I think everything I was planning was wrong. ::shrug:: sorry if it seems like I don't take anyones opinion, really I am just collecting opinions. I just want the best I can do. Its not a project for school or anything, just for fun. But I do want the best out of it I can get. I really don't know which forums for DIY I like the best yet. I am kinda giving them all a try. Madisound people never replied to anything for the most part, HTF moves slowly, PE is the best so far, just thought I would talk to John here and see if he could offer input since he is obviously so experienced

[Teran]

very true. It seems like whenever I read another post I see something else that worries me.

That will happen. Forever, it seems.

Its not a project for school or anything, just for fun. But I do want the best out of it I can get.

I know it isn't for school, but the analogy still holds. You have to stop somewhere.

I'm not being critical, just trying to help. :T

[cjd]

PE is the best so far

PE is the most mixed bag too. I would still say it's the most "beginner friendly" forum I've come across. You just have to be careful, as there are folks that will shell out garbage.

Me, I started out with el-cheapo buyout drivers. Intentionally. I didn't ever expect the sound to be everything I wanted, but they still taught me an awful lot about speaker design. And I still use the speakers I developed in my HT - I don't think I can better them significantly with any budget I have available right now to make it worth doing.

C