TL to TM

Electro

Member
2002-04-12 4:41 am
Yes and No.

Yes, you can convert a Transmission Line to a vented box unless you select a huge diameter tube.

No, you can not do this with out having problems. Vented boxes or bass reflex loudspeakers changes the frequency reponse of the speaker driver if its not tuned properly. This means if the enclosure is two times bigger than its flat response and using low tuning. In simpler terms an Extended Bass System or EBS.
 
I'd be wary of Electros advise. His words are cryptic and don't really address the question. His website is hosted with a free server and therefore has advertising. This is really tacky. His content is practically non-existant and what is there is vacuous. I don't think he knows very much about the subject on which he wants to give advise.

Other than the above, I can't supply any advise because I know nothing about the EVENT TL nor the Proac 2.5.
 
The Event TL uses a ScanSpeak 18W/8535 & D-2905/9300 with an XO that looks to be between 1.5 & 2 KHz. The kind of box should have no affect up there. The shape of the box and it's diffraction characteristics might.

I'm not familiar with the ProAc but it should be fairly simple to use box-modeling software to figure out how well the ProAc box will work and how much you need to change the porting for optimum performance in that box. What is optimum will depend on your room and whether you are using a sub (in which case no port might be the best port)

dave

Bill. It is true that Electro's comments don't really address the problem and the 1st sentence doesn't make much sense at all. His website doesn't work in my browser so i can't comment on its content and sometimes a free server is the most expensive one a person can afford, but lets see if we can keep things civil.
 

kelticwizard

diyAudio Moderator Emeritus
2001-09-18 2:33 am
Connecticut, The Nutmeg State
Okay, let's see. Since Planet 10 gave us the Scnspeak woofer model I went to the Scanspeak website and got the following numbers:

18W/8535-00

Characteristic sensitivity (2.83V / 1m) : 86.5 dB
Recommended frequency range : 26 - 3500 Hz
Free air resonance frequency, fs : 26 Hz
DC resistance, Re : 5.8 ohm
Voice coil inductance, Le : 0.3 mH
Effective piston area, Sd : 145 cm²
Moving mass incl. air, md : 15.5 g
Mechanical loss, Rm : 1.0 Ns/m
Force factor, BL : 5.7 Tm
Equivalent volume, Vas : 72 ltr.or 2.5 cu ft
Mechanical Q-factor, Qms : 2.5
Electrical Q-factor, Qes : 0.45
Total Q-factor, Qts : 0.38
Excursion, lin./max. : ±5.0 / ±10 mm
Voice coil diameter : 38 mm
Rated power handling : 70 W
Net weight : 1.8 kg

Ideal volume would appear to be about 2.5 cu ft. Workable volume would range from 1.5 cu ft to 4 cu. ft.

I'll search for the ProAc dimensions for the likely internal volume. This will at least get you started.
 

kelticwizard

diyAudio Moderator Emeritus
2001-09-18 2:33 am
Connecticut, The Nutmeg State
Apparently the ProAc uses the same woofer, different tweeter. So you don't even have to bother tuning the ProAc box.

Here's a website for a fellow building a ProAc clone:
http://www.geocities.com/diyproac25/comments.htm

One thing I would advise. When transferring your drivers to the ProAc cabinet, maintain the same space between the center of the woofer and the center of the tweeter that they had in the Event. This is assuming you are using the Event crossover. Spacing is important in crossovers.

Do you have a ProAc crossover in your ProAc boxes? If so, you might find it more convenient to simply the buy the tweeter the ProAc uses-it's on the website-and use the Proac crossover. The woofer is the same, so you can just hook it up to the ProAc crossover as well.

Good luck! :)
 

Electro

Member
2002-04-12 4:41 am
I should have put the first sentence through a word processor. I should also re-phrase the first question.


OFF TOPIC:
planet10, you might have been using a web browser similar to Netscape 6. This is one web browser it doesn't show. I debugged my code so it should work. I haven't yet uploaded the revised pages to the servers yet. I'm using free servers because I don't have a lot of money to spend each month.

Also hit No if you see any advertisments pop ups such as Gator. Gator has spyware embedded in the software. DO NOT download GATOR.
 

kelticwizard

diyAudio Moderator Emeritus
2001-09-18 2:33 am
Connecticut, The Nutmeg State
There are some differences in tweeters. The Event tweeter has a larger faceplate.

There are some impedance differences, especially around 1500 to 2000 Hz. I would suggest making sure the tweeter is hooked up to the crossover it came with-that is, ProAc tweeter to ProAc crossover, Event tweeter to Event crossover. I would advise against mixing.

The woofers are the same, so it makes no differnce there.

That website I gave you has the ProAc crossover schematic, if you want to homebrew it.

Here is the Event tweeter.
 

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Electro said:
OFF TOPIC:
planet10, you might have been using a web browser similar to Netscape 6. This is one web browser it doesn't show.

I'm using iCab which isn't very tolerant of flaky javascript and has the hooks into Java only partially implemented.

I always feel that web pages should be kept simple and developed so that everybody can see them -- there is a whole 3rd world coming up that will be using a lot of out discarded computers and will be on modems for a long time. This means NO Frames, No Javascript, No Java. Anything whizzy should be on the server side.

And i have no problem with free web space, as i said not everyone can afford web space, but everyone should be able to piblish their stuff.

dave
 
kelticwizard said:
The woofers are the same, so it makes no difference there.

Well actually is does. The XO points aren't necessarily at the same place and the roll-offs (one would assume) have been tailored to the respective Ts. So use the Event XO if you use the Event tweeter, and the ProAc if you use the ProAc tweeter.

Good work keltic wizard...

dave
 

kelticwizard

diyAudio Moderator Emeritus
2001-09-18 2:33 am
Connecticut, The Nutmeg State
kelticwizard said:
The woofers are the same, so it makes no differnce there.

Oops. I did not mean to imply that you can use the woofer using Event's low pass crossover and attach it to a tweeter using the ProAc high pass crossover.

I only meant that you can unhook the woofer from the Event crossover and hook it right up to the ProAc crossover-no need to worry about impedance characteristics with the woofer since both speakers use the same one.
 

kelticwizard

diyAudio Moderator Emeritus
2001-09-18 2:33 am
Connecticut, The Nutmeg State
Which is the better, the Event or ProAc crossover? I don't know. I'll give you some thoughts, for what they are worth.

I am not that much of a crossover expert. I have heard of the ProAcs, not of the Events. That possibly might mean a better sound for the ProAcs but that is sketchy speculation at best.

The ProAcs are 8 element crossovers, the Events 6 element. The ProAc design seems slightly more sophisticated because on both the high pass and low pass sections, the series component is broken up into 2 parts with a parallel element between them. In the crossover world, however, where simpler frequently equals better, I can't say that's necessarily an advantage.

I have not had experience with either of the Scanspeak tweeters. The event's cost $76 at Madisound, the ProAc's cost $56. Each.

If you take a look at the dispersion charts, you see that the 3/4" ProAc tweeter has better dispersion than the 1" Event tweeter. If you take a look at the bottom line-60 degrees off axis-the difference becomes fairly large. That would tend to indicate that the highs on a ProAc might have a special "sheen".

However, I have not gotten around to using 3/4" tweeters so I cannot say. And highly priced, highly rated systems use 1" tweeters.

If anyone has had experience on 3/4" tweeters versus 1" tweeters, please jump in here.

Of course, there is some difference in cost. Two ProAc tweeters are over $100 right there, than add the crossover cost. You already have the Event tweeter and crossover.

If you want to spend between $150 and $200 to find out if the ProAc has a nicer high end, that's up to you. You already have a higher priced tweeter and crossover in your possession.